Rhodium-catalyzed silylformylation of acetylenic bonds: Its scope and mechanistic considerations

Organometallics 1997, 16, 4327-4345

4327

Rh od iu m -Ca ta lyzed Silylfor m yla tion of Acetylen ic

Bon d s: Its Scop e a n d Mech a n istic Con sid er a tion s

Isamu Matsuda,*^,†Yukimasa Fukuta,^†Toru Tsuchihashi,^†

Hideo Nagashima,^‡and Kenji Itoh^†

Department of Applied Chemistry, Graduate School of Engineering, Nagoya University,

Chikusa, Nagoya 464-01, J apan, and School of Material Science, Toyohashi University of

Technology, Tempaku-cho, Toyohashi 441, J apan

Received J une 27, 1997^X

“Silylformylation” of alkynes, which means the simultaneous introduction of a trialkylsilyl

group and a formyl group into a carbon-carbon triple bond to give 3-silyl-2-alkenal, is

attained selectively by the interaction of an alkyne with a monohydrosilane in the presence

of Rh catalyst under CO pressure (over 10 kg/cm²). The presence of Rh catalyst is crucial

for the attainment of this coupling, regardless of the types of precursors: Rh₄(CO)₁₂, RhH-

(CO)(PPh₃)₃, [Rh(COD)Cl]₂, [Rh(COD)(PPh₃)₂]PF₆, or [Rh(COD)(DPPB)]PF₆. This silyl-

formylation is applicable to both terminal and internal alkynes. In the terminal ones, the

terminal sp carbon is selectively silylated. The sp carbon bearing the bulkier substituent is

formylated preferentially in internal alkynes, except for those containing a strong electron-

withdrawing group. When a 1 mol excess of 1-alkynes is used under silylformylation

conditions, the formation of 2-cyclopentenone derivatives is confirmed in addition to the

usual silylformylation. All of these cyclopentenones are composed of two molecules of

1-alkyne and one molecule each of hydrosilane and CO. A catalyst precursor of these

reactions, Rh₄(CO)₁₂, reacts almost quantitatively with hydrosilane and phenylacetylene to

form Rh(CO)₄SiR₃and Rh₂(CO)₇(phenylacetylene), respectively, under CO pressure in the

stoichiometric reaction. Both of these species catalyze silylformylation with a similar

efficiency to Rh₄(CO)₁₂. Furthermore, Rh(CO)₄SiR₃readily reacts with phenylacetylene under

a CO atmosphere to give 1,5-disilyl-2,4-diphenyl-1(Z),4(Z)-pentadien-3-one and Rh₄(CO)₁₂.

On the basis of these results, a plausible pathway for silylformylation is elucidated by the

sequence of the insertion of alkyne into the Rh-Si bond to form Rh-vinyl species and the

subsequent insertion of CO. The insertion of another 1 mol of alkyne into Rh-vinyl species

prior to CO insertion results in cyclopentenone annulations.

In tr od u ction

ated ketones,^3,4esters,⁵lactones,⁶amides,⁷and lactams.^7c

Although hydroformylation of acetylenic bonds could be

an attractive method for the preparation of R,â-unsatur-

ated aldehydes,^2f,8a serious drawback is that the

presence of excess hydrogen in the reaction vessel

causes consecutive hydrogenation of carbon-carbon

and/or carbon-oxygen double bonds of the resulting

unsaturated aldehydes. In addition, there is no reliable

Catalytic incorporation of carbon monoxide is one of

the most elegant and economical synthetic tools for the

direct introduction of a carbonyl group into organic

molecules.¹Various carbonylation reactions catalyzed

by transition-metal complexes have been explored since

the discovery of Roelen’s reaction.²That of acetylenic

compounds has been particularly interesting, since it

provides a facile means for the synthesis of R,â-unsatur-

(3) (a) Mise, T.; Hong, P.; Yamazaki, H. Chem. Lett. 1982, 401. (b)

Hong, P.; Mise, T.; Yamazaki, H. J . Organomet. Chem. 1987, 334, 129.

(4) Deshong, P.; Sidler, D. R.; Rybczynski, P. J .; Slough, G. A.;

Rheingold, A. L. J . Am. Chem. Soc. 1988, 110, 2575.

(5) (a) Tsuji, J .; Nogi, T. J . Org. Chem. 1966, 31, 2641. (b) Tsuji, J .;

Nogi, T. J . Am. Chem. Soc. 1966, 88, 1289. (c) Chiusoli, G. P.; Dubini,

M.; Ferraris, M.; Guerreri, F.; Merzoni, S.; Mondelli, G. J . Chem. Soc.

C 1968, 2889. (d) Heck, R. F. J . Am. Chem. Soc. 1972, 94, 2712. (e)

Casser, L.; Chiusoli, G. P.; Guerreri, F. Synthesis 1973, 509. (f)

Kasahara, A.; Iizumi, T.; Suzuki, A. Bull. Chem. Soc. J pn. 1977, 50,

1639. (g) Knifton, J . F. J . Mol. Catal. 1977, 2, 293. (h) Alper, H.;

Despeyroux, B.; Woell, J . Tetrahedron Lett. 1983, 28, 5691. (i) Tsuji,

Y.; Kondo, T.; Watanabe, Y. J . Mol. Catal. 1987, 40, 295. (j) Itoh, K.;

Miura, M.; Nomura, M. Tetrahedron Lett. 1992, 33, 5369. (k) Takeuchi,

R.; Sugiura, M. J . Chem. Soc., Perkin Trans. 1 1993, 1031.

(6) (a) Murray, T. F.; Norton, J . R. J . Am. Chem. Soc. 1979, 101,

4107. (b) Murray, T. F.; Samsel, E. G.; Varma, V.; Norton, J . R. J .

Am. Chem. Soc. 1981, 103, 7520. (c) Mise, T.; Hong, P.; Yamazaki, H.

J . Org. Chem. 1983, 48, 238. (d) J oh, T.; Doyama, K.; Shiohara, T.;

Takahashi, S. Organometallics 1991, 10, 2493.

^†Nagoya University.

^‡Toyohashi University of Technology. Present address: Institute

of Advanced Material Study, Kyushu University, Kasuga, Fukuoka

816, J apan.

^XAbstract published in Advance ACS Abstracts, September 1, 1997.

(1) (a) Heck, R. F. Palladium Reagents in Organic Synthesis;

Academic Press: New York, 1985; p 341. (b) Colquhoun, H. M.;

Thompson, D. J .; Twigg, M. V. Carbonylation: Direct Synthesis of

Carbonyl Compounds; Plenum Press: New York, 1991. (c) Thompson,

D. J . In Comprehensive Organic Synthesis; Trost, B. M., Fleming, I.,

Eds.; Pergamon Press: Oxford, U.K., 1991; Vol. 3, p 1015. (d) Tsuji, J .

Palladium Reagents and Catalyst; Wiley: Chichester, U.K., 1995; p

340.

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F.; Bianchi, M. In Organic Synthesis via Metal Carbonyls; Wender, I.,

Pino, P., Eds.; Wiley: New York, 1977; Vol. 2, p 43. (c) Pruett, R. L. In

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Oxford, U.K., 1991; Vol. 4, p 913.

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1990, 63, 640. (c) Torii, S.; Okumoto, H.; Sadakane, M.; Xu, L. H. Chem.

Lett. 1991, 1673.

(8) Pino, P.; Braca, G. In Organic Synthesis via Metal Carbonyls;

Wender, I., Pino, P., Eds.; Wiley: New York, 1977; Vol. 2, p 419.

4328 Organometallics, Vol. 16, No. 20, 1997

Matsuda et al.

aldehydes,²⁰epoxides,²¹and N,N-acetals²²using R₃SiH/

CO/transition-metal systems. The tacit assumption in

explaining these reactions is that starting substrates

insert into the transition-metal-silicon bond first formed;

however, no definitive evidence supporting this assump-

tion has yet been obtained. For organic synthesis the

present rhodium-catalyzed silylformylation of alkynes

is an ideal vehicle for the construction of many building

blocks because of its high regio- and chemoselectivity,

in sharp contrast to the results of hydroformylation. It

provides a convenient access to â-silyl enals, which have

been prepared by an indirect and relatively tedious

procedure²³and which have attracted the attention of

many synthetic organic chemists as precursors of silyl-

substituted dienes,²⁴dienones,²⁵and R,â-unsaturated

ketones.²⁶

Sch em e 1. P a tter n s In cor p or a tin g CO in th e

P r esen ce of R₃SiH

Sch em e 2. Silylfor m yla tion of Alk yn es

In this paper, we report on the following three topics

concerning rhodium-catalyzed silylformylation of

alkynes: (i) full details of alkyne silylformylation fo-

cused on the regio- and stereoselectivity of the reactions,

(ii) a novel type of cyclopentenone annulation which

results from the coupling of two molecules of an alkyne

and one molecule each of a hydrosilane and CO, and

(iii) stoichiometric reactions of Rh₄(CO)₁₂with hydrosi-

lanes under CO pressure that provide informative

suggestions on the reaction mechanism.

means to control the regiochemistry in the introduction

of a hydrogen atom and a formyl group except for the

hydroformylation of acetylenic bonds bearing a triorga-

nosilyl group on one side of two sp carbons.⁹Hydrosi-

lanes have been widely used in recent organic synthesis

as a synthetic equivalent of molecular hydrogen. Car-

bonylation in the presence of hydrosilanes, which is

conceptually comparable to the carbonylation under

hydrogen pressure, has been explored by Murai and co-

workers.¹⁰Their pioneering work established a method

using Co₂(CO)₈as a catalyst to introduce CO and

hydrosilanes into alkenes,¹¹aldehydes,¹²and cyclic

ethers.¹³However, the most characteristic point in the

Murai reaction of alkenes is that the isolated product

is neither â-silyl aldehyde (A) nor acylsilane (B), which

would be expected from the formal analogy with Ro-

elen’s reaction, but an enol silyl ether (C) (Scheme 1).

In 1989 we discovered the first examples of “silyl-

formylation” of alkynes,¹⁴in which simultaneous incor-

poration of a triorganosilyl group and a formyl group

into an acetylenic bond is attained by rhodium-catalyzed

coupling of an alkyne, a hydrosilane, and CO as shown

in Scheme 2. This finding triggered burgeoning interest

in the incorporation of CO into alkynes,^15-18enamines,¹⁹

Resu lts a n d Discu ssion

P r ep a r a tion of â-Silyl Alk en a ls by Silylfor m yl-

a tion of Acetylen ic Com p ou n d s. As described in our

previous paper,¹⁴â-silyl alkenals are generally synthe-

sized by carbonylation of alkynes in the presence of

trialkylhydrosilanes and catalytic amounts of Rh₄(CO)₁₂.

Typically, a benzene²⁷solution of phenylacetylene (1a ),

Me₂PhSiH (1 equiv based on 1a ), and Rh₄(CO)₁₂(0.1-1

mol % based on 1a ) was stirred under CO pressure (20

kg/cm²) to give the â-silylalkenal 2a in 70-90% yield

(eq 1). Addition of Et₃N to the reaction mixture was

(9) (a) J ackson, W. R.; Lovel, C. G. Aust. J . Chem. 1983, 36, 1975.

(b) Fitzmaurice, N. J .; J ackson, W. R.; Perlmutter, P. J . Organomet.

Chem. 1985, 285, 375.

(10) (a) Murai, S.; Sonoda, N. Angew. Chem., Int. Ed. Engl. 1979,

18, 837. (b) Murai, S.; Seki, Y. J . Mol. Catal. 1987, 41, 197. (c) Chatani,

N.; Kajikawa, Y.; Nishimura, H.; Murai, S. Organometallics 1991, 10,

21. (d) Chatani, N.; Murai, S. Synlett 1996, 414.

(11) Seki, Y.; Kawamoto, K.; Chatani, N.; Hidaka, A.; Sonoda, N.;

Ohe, K.; Kawasaki, Y.; Murai, S. J . Organomet. Chem. 1991, 403, 73.

(12) Murai, S.; Kato, T.; Sonoda, N.; Seki, Y.; Kawamoto, K. J .

Organomet. Chem. 1979, 18, 393.

not crucial for the silylformylation, but both the reaction

(17) (a) Doyle, M. P.; Shanklin, M. S. Organometallics 1993, 12, 11.

(b) Doyle, M. P.; Shanklin, M. S. Organometallics 1994, 13, 1081.

(18) Zhou, J .-Q.; Alper, H. Organometallics 1994, 13, 1586.

(19) Ikeda, S.; Chatani, N.; Kajikawa, Y.; Ohe, K.; Murai, S. J . Org.

Chem. 1992, 57, 2.

(13) Murai, T.; Yasui, E.; Kato, S.; Hatayama, Y.; Suzuki, S.;

Yamasaki, Y.; Sonoda, N.; Kurosawa, H.; Kawasaki, Y.; Murai, S. J .

Am. Chem. Soc. 1989, 111, 7938.

(14) Matsuda, I.; Ogiso, A.; Sato, S.; Izumi, Y. J . Am. Chem. Soc.

1989, 111, 2332.

(20) Wright, M. E.; Cochran, B. B. J . Am. Chem. Soc. 1993, 115,

2059.

(21) Fukumoto, Y.; Chatani, N.; Murai, S. J . Org. Chem. 1993, 58,

4187.

(22) Ikeda, S.-I.; Chatani, N.; Murai, S. Organometallics 1992, 11,

3494.

(23) (a) Matione, R.; Leroux, Y. J . Organomet. Chem. 1971, 31, 5.

(b) Merault, G.; Picard, J .; Buorgeois, P.; Dunogues, J .; Duffault, N.

J . Organomet. Chem. 1972, C80. (c) Pillot, J .; Dunogues, J .; Calas, R.

Bull. Soc. Chim. Fr. 1975, 2143. (d) Cunico, R. F.; Clayton, F. J . J .

Org. Chem. 1976, 41, 1480. (e) Otera, J .; Mandai, T.; Shiba, M.; Saito,

T.; Shimohata, K.; Takemori, K.; Kawasaki, Y. Organometallics 1983,

2, 332. (f) Campi, E.; Fitzmaurice, N. J .; J ackson, W. R.; Perlmutter,

P.; Smallridge, A. Synthesis 1987, 1032.

(24) (a) J ung, M. E.; Gaede, B. Tetrahedron 1979, 35, 621. (b) Carter,

M. J .; Fleming, I.; Percival, A. J . Chem. Soc., Perkin Trans. 1 1981,

2415.

(25) Pillot, J .; Dunogues, J .; Calas, R. J . J . Chem. Res., Synop. 1977,

268.

(15) (a) Matsuda, I.; Ogiso, A.; Sato, S. J . Am. Chem. Soc. 1990,

112, 6120. (b) Matsuda, I.; Sakakibara, J .; Nagashima, H. Tetrahedron

Lett. 1991, 32, 7431. (c) Matsuda, I.; Sakakibara, J .; Inoue, H.;

Nagashima, H. Tetrahedron Lett. 1992, 33, 5799. (d) Matsuda, I.;

Ishibashi, H.; Ii, N. Tetrahedron Lett. 1995, 36, 241. (e) Monteil, F.;

Matsuda, I.; Alper, H. J . Am. Chem. Soc. 1995, 117, 4419. (f) Ojima,

I.; Vidal, E.; Tzamarioudaki, M.; Matsuda, I. J . Am. Chem. Soc. 1995,

117, 6797.

(16) (a) Ojima, I.; Ingallina, P.; Donovan, R. J .; Clos, N. Organome-

tallics 1991, 10, 38. (b) Ojima, I.; Donovan, R. J .; Eguchi, M.; Shay,

W. R.; Ingallina, P.; Korda, A.; Zeng, Q. Tetrahedron 1993, 49, 5431.

(c) Eguchi, M.; Zeng, Q.; Korda, A.; Ojima, I. Tetrahedron Lett. 1993,

34, 915. (d) Ojima, I.; Tzamarioudaki, M.; Tsai, C.-Y. J . Am. Chem.

Soc. 1994, 116, 3643. (e) Ojima, I.; Fracchiolla, D. A.; Donovan, R. J .;

Banerji, P. J . Org. Chem. 1994, 59, 7594.

(26) Fleming, I.; Perry, D. A. Tetrahedron 1981, 37, 4027.

Rh-Catalyzed Silylformylation of Acetylenic Bonds

Organometallics, Vol. 16, No. 20, 1997 4329

rate and the yield of the product were somewhat

improved in its presence. It is well-known that rhodium

complexes behave as an efficient catalyst for the hy-

drosilylation of alkynes. In fact, Rh₄(CO)₁₂catalyzed

the hydrosilylation of 1a under an inert-gas atmosphere

(vide infra). Though hydrosilylation is almost com-

pletely suppressed under CO pressure, it becomes an

appreciable competing process in the silylformylation.

Two practical procedures were devised to exclude the

hydrosilylation; all of the reactants, solvents, and the

catalyst were mixed at low temperature (-70 °C), where

hydrosilylation does not occur, and then the reaction

vessel was pressurized by CO. Alternatively, a solution

of the catalyst was saturated with CO (20 kg/cm²; 5 min)

prior to the addition of reactants. In either procedure,

the product yields remained unaltered when the CO

pressure was reduced to 7-10 kg/cm², whereas ap-

preciable amounts of hydrosilylation products were

concomitantly formed as byproducts under less than 5

kg/cm²of CO pressure. When 10-20 kg/cm²of CO

pressure and 0.1-0.2 mol % of the catalyst were applied,

the reaction was complete within 2 h at 100 °C.

Although the reaction became slower (600-700 turnover

frequency at room temperature after 17 h), the silyl-

formylation proceeded smoothly even at room temper-

ature.

There are two possible regiochemistries with respect

to the addition of the formyl group and the silyl group;

however, it was confirmed that 2a was the sole regioi-

somer in the silylformylation of 1a with Me₂PhSiH. Of

the two possible stereoisomers of 2a (Z and E), the Z

isomer was found to be a kinetic product, which was

slowly isomerized to the thermodynamically more stable

E isomer under the carbonylation conditions.^28-30Typi-

cally, the Z:E ratio of 2a was 88:12 in the reaction at

100 °C for 2 h, and the ratio of E form increased when

a longer reaction time was applied. In other words,

stereoselective preparation of the kinetic product (Z

form of 2a ) is possible with careful selection of the

reaction conditions; in fact, the Z to E ratio was 98:2 at

20 °C for 17 h. The extreme result (absence of detect-

able E isomer) was observed in the reaction containing

a relatively large amount of catalyst (mole ratio of 1a

to Rh₄(CO)₁₂∼320), in which the silylformylation was

completed within 20 min at 25 °C. Such high regio- and

stereoselectivities observed in the silylformylation are

in notable contrast to the hydrosilylation, which resulted

in rather sluggish selectivities. Treatment of 1a and

Me₂PhSiH with a catalytic amount of Rh₄(CO)₁₂at room

temperature under an N₂atmosphere gave a mixture

of the two regioisomers 3 and 4 in a ratio of 87:13 as

shown in eq 2. The Z to E ratio of 3 was also low (64:

36).

The use of a 1:1 mixture of 1a and Me₂PhSiH is also

critical to the formation of 2a in high yields; alteration

of the ratio caused the concomitant formation of several

types of byproducts. As described later in detail,

cyclopentenones resulting from the participation of two

molecules of 1a were obtained as a minor product when

an excess amount of 1a (1a :Me₂PhSiH ) 2:1) was used

in the carbonylation. In contrast to the above result,

the subsequent hydrosilylation of 2a took place in the

presence of excess Me₂PhSiH. For example, in the

silylformylation using a 1:2 mixture of 1a and Me₂-

PhSiH at 95 °C for 13 h, appreciable amounts of 5, 6,

and 7 in addition to 2a were detected in the NMR

spectrum of the reaction mixture. Compounds 6 and 7

were derived from the subsequent hydrosilylation of 2a ,

whereas 5 was formed by protodesilylation of the enol

silyl ether part of 7.

Some other hydrosilanes in addition to Me₂PhSiH

were applicable to the silylformylation of 1a , in which

most of them were completely consumed after stirring

a mixed solution at 100 °C for 2 h or at 25 °C for 15 h.

Although the rough profiles of the reactions were

identical in most silanes, details of the rate of reaction

and the yield of the product were remarkably affected

by the substituents contained in hydrosilanes, as shown

in Table 1.

(27) Benzene is not the solvent of choice in silylformylation. All of

the following solvents gave similar results under similar conditions:

toluene, hexane, CHCl₃, CH₂Cl₂, CH₃CN, and THF.

(28) The stereoisomers of â-silylalkenals were easily diagnosed by

¹H NMR spectra using the NOE technique. In a typical example using

both isomers of 2e, which were completely separated by silica gel

column chromatography, 12% enhancement of signals was observed

in the NOE experiment between the formyl proton and the vinyl one

in the E form, whereas it was not seen in the Z form. Similar

experiments on all of the â-silylalkenals described in this paper

revealed that the formyl proton contained in the Z form generally

appeared at 0.3-0.5 ppm lower field than the E form. This observation

is consistent with a previous report.²⁹

(29) Bestmann, H. J .; Roth, K.; Ettlinger, M. Chem. Ber. 1982, 115,

161.

(30) 3-Silylalkenals 2a , 2c, 2d , 2e, 2j, 2k , 9e, and 10e, isolated as

mixture of Z and E forms, were exclusively converted to the

a

corresponding E form by stirring a benzene solution of the respective

sample in the presence of a catalytic amount of HI for 14 h at 25 °C.

Although the process from E form to Z form exists in a particular case

such as 2m , in which separate CDCl₃solutions of the isolated E and

Z isomers settled down into an identical mixture (Z:E ) 19:81) even

in the absence of HI, all these results consistently suggest that the E

form of the silylformylation product is generally more thermodynami-

cally stable than the Z form.

For example, it was found that silylformylation of 1a

4330 Organometallics, Vol. 16, No. 20, 1997

Matsuda et al.

Ta ble 1. Silylfor m yla tion of P h en yla cetylen e (1a )^a

Ta ble 2. Silylfor m yla tion of 1-Alk yn e w ith

Hyd r osila n es^a

products

yield (%)^c

entry

no.

conditions^b

Z:E^d

alkyne 1

products

hydrosilane

entry

no.

R¹

hydrosilane

yield (%)^b

Z:E^c

1

2

3

4

5

6

7

8

9

10

11

12

13

14

Me₂PhSiH

MePh₂SiH

Et₃SiH

A

B

A

B

A

B

A

B

A

B^e

B

A

2a

8

9a

89

90

94

84

92

85

75

78

22^f

82

70^g

47^h

0

88:12

98:2

83:17

97:3

91:9

98:2

79:21

98:2

92:8

98:2

50:50

14:86

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

1b

1c

1d Et

H

Me

Me₂PhSiH

Et₃SiH

2b

2c

2d

2e

9e

73

99

91

93

62^d

91

13^e

91^d,f

86^d

81^d

71^d,f

71

82^d

86^d

96

90

94

0:100

80:20

94:6

95:5

90:10

97:3

1e

1f

ⁿC₃H₇

ⁿC₄H₉

Et₃SiH

9a

Et₂MeSiH

^tBuMe₂SiH

Me₂(EtO)SiH

(MeO)₃SiH

ⁱPr₃SiH

10a

11a

12

13

^tBuMe₂SiH 11e

99:1

^tBuMe₂SiH 11e

Me₂PhSiH

Et₂MeSiH

^tBuMe₂SiH 11f

Me₂PhSiH

Et₃SiH

100:0

85:15

89:11

100:0

87:13

95:5

2f

10f

1g ⁿC₅H₁₁

1h ⁿC₆H₁₃

1i

1j

1k Me₃SiCH₂

1l Me₃Si

1m HOCH₂

1n MeOCH₂

1o Cl(CH₂)₃

2g

9g

9h

2i

2j

2k

2l

2m

2n

2o

Ph₂SiH₂

0

96:4

a

All reactions were conducted on a scale of 3-9 mmol in a

benzene solution containing 0.2 mol % of Rh₄(CO)₁₂and equimolar

amounts of 1a , hydrosilane, and Et₃N under CO pressure (20 kg/

^cC₆H₁₁

Me₂PhSiH

100:0

73:27

91:9

100:0

37:63

77:23

88:12

CH₂dCHCH₂Me₂PhSiH

Me₂PhSiH

b

cm²). Legend: (A) reaction was carried out for 2 h at 100 °C; (B)

55

83

78^d

32^g

78

reaction was carried out for 15 h at 25 °C. ^cIsolated yield.

d

Determined from the ¹H NMR spectra. ^eReaction time was

increased to 65 h. ^fThe reaction was not completed. ^gThe product

was obtained as a mixture of 12 and hemiacetal 14 (12:14 ) 2:1)

h

by direct distillation of the reaction mixture. The product was

a

obtained as a mixture of 13 and hemiacetal 15 (13:15 ) 6:1) by

direct distillation of the reaction mixture.

Reactions were conducted on a scale of 2-10 mmol in a

benzene solution containing 0.3 mol % of Rh₄(CO)₁₂and equimolar

amounts of 1, hydrosilane, and Et₃N under CO pressure (10-30

b

kg/cm²) for 2 h at 100 °C unless stated otherwise. Isolated yield.

with hydrosilanes bearing a phenyl group proceeds

approximately 10 times faster than that with trialkyl-

silanes. The rate was roughly estimated from the

turnover frequencies of Rh₄(CO)₁₂, 570, 460, and 60,

which were obtained in the silylformylation at 25 °C for

3.5 h using Me₂PhSiH, MePh₂SiH, and Et₂MeSiH as the

hydrosilane, respectively. It takes 65 h to complete

d

^cDetermined from the ¹H NMR spectra. The reaction was carried

out in the absence of Et₃N. ^eReaction time was increased to 17 h.

^fThe reaction was carried out in an acetonitrile solution for 17 h

g

at 90 °C. The reaction was carried out for 15 h at 25 °C.

Me₂(EtO)SiH and (MeO)₃SiH reacted readily with 1a

to incorporate CO; however, the obtained product was

a mixture of the corresponding â-silylalkenal (12a or

13a ) and hemiacetal (14 or 15). These products did not

t

silylformylation of 1a with BuMe₂SiH at 25 °C (entry

10 in Table 1); this is approximately 4 times as long as

that with Et₂MeSiH.³¹The operation at 100 °C in order

to accelerate reaction rate did not improve the yield of

11a (entry 9 in Table 1) but resulted in the formation

of significant amounts of byproducts derived from the

participation of 2 mol of 1a and the corresponding silane

(vide infra). The high reactivity of Me₂PhSiH is also

reflected in the result that 2a was formed predomi-

nantly (2a /11a > 7) in the competitive reaction starting

allow further purification except by bulb-to-bulb distil-

lation, due to a facile hydrolysis of Si-O bonds. They

changed to resinous intractable materials during stor-

age in a sealed tube even at room temperature. In

sharp contrast to monohydrosilane, the dihydrosilane

Ph₂SiH₂did not cause silylformylation at all; hydrosi-

lylation was the sole reaction pattern observed.

t

from 1 equiv each of 1a , Me₂PhSiH, and BuMe₂SiH (eq

4). Despite the presence of an excess of hydrosilanes,

any side reaction product was detected at all because

the reaction was carried out at 25 °C.

Other alkynes as well as 1a were also active to the

silylformylation. The reactions of 1-alkynes generally

gave the corresponding 2-substituted 3-silylpropenals

in high yields as summarized in Table 2, in which no

regioisomer was detected. As reported earlier,^15asome

of the homopropargyl alcohols reacted with hydrosilanes

and CO to give R-(silylmethylene)-γ-lactones accompa-

nied by the elimination of an H₂molecule. This

evidence makes us expect that the intermediate in-

volved in the catalytic cycle of silylformylation is

susceptible to the free hydroxy group contained as

alcohols or water. However, the reaction of 1m afforded

the corresponding alkenal as the sole product in high

yield. Analogously, silylformylation of 1 was not af-

fected by the presence of more than 1 equiv of either

H₂O or methanol. Functional groups contained in the

alkyne molecules, such as olefinic, Me₃Si, hydroxy,

methoxy, and chloro groups, remained intact as shown

In an extreme case, as exemplified in the reaction of

ⁱPr₃SiH, incorporation of CO was completely suppressed

because of the steric hindrance. The alkoxysilanes

(31) Poor reactivity of ^tBuMe₂SiH was in some cases complemented

by the use of acetonitrile as a solvent instead of benzene (see entries

7, 8, and 11 in Table 2).

Rh-Catalyzed Silylformylation of Acetylenic Bonds

Organometallics, Vol. 16, No. 20, 1997 4331

Ta ble 3. Silylfor m yla tion of In ter n a l Alk yn es (16)

w ith Me₂P h SiH^a

in entries 16-22. It should also be pointed out that 2j

was isolated as the sole product in the silylformylation

of 1j, though the structure of 2j is in the same category

as 4-pentenal derivatives which are readily converted

to cyclopentanone rings by Rh-catalyzed operations.^32,33

There is an interesting report³that an ethylene mol-

ecule is incorporated together with CO and H₂into

terminal alkynes to form R,â-unsaturated ketones with

the assistance of Rh₄(CO)₁₂. Similar participation of

ethylene is also expected in our silylformylation because

of the analogy of starting materials; however, 2e was

the sole product (95%) in the reaction of 1e with Me₂-

PhSiH in the presence of CO (25 kg/cm²) and ethylene

(15 kg/cm²).

It is of interest that the rate of silylformylation

strongly depends on the substituents linked to an sp

carbon of the acetylenic part. A competitive reaction

using Me₂PhSiH as a hydrosilane revealed that pheny-

lacetylene reacts much faster than 1-hexyne to give 2a

predominantly, as shown in eq 5. (Trimethylsilyl)-

alkyne 16

yield (%) of product^b

17 18

entry no.

R¹

R²

1

2

3

4

5

6

7

8

a

b

c

d

e

f

Me

Ph

Me

Ph

Me

a

b

c

d

e

f

94^c

60

74

90^d

0

ⁿC₃H₇

Ph

b

c

26

8

Ph

CO₂Me

CO₂Et

SiMe₃

e

f

g

h

67

43

0

g

h

Me

Ph

g

h

0

a

Reactions were conducted on a scale of 2-10 mmol in benzene

solution containing 1 mol % of Rh₄(CO)₁₂and equimolar amounts

of 16, Me₂PhSiH, and Et₃N under CO pressure (10-30 kg/cm²)

b

d

for 2 h at 100 °C. Isolated yield. ^cZ:E ) 100:0. Z:E ) 95:5.

bulkier substituent. Derivatives of propiolates, 16e and

16f, were different from the dialkyl- or alkylarylacety-

lenes due to the fact that the electronic effect was a

major factor determining the regiochemistry; R-silyl

â-formyl R,â-unsaturated esters 18e and 18f were

obtained as single isomers. Hydrosilylation was a

serious competitive reaction in the silylformylation of

16e and 16f. (Trimethylsilyl)acetylenes 16g and 16h

did not give any carbonylated products; this could be

attributable to steric hindrance arising from the bulki-

ness of the Me₃Si group.

acetylene was susceptible to silylformylation despite the

apparent retardation of the rate because of a bulky

substituent, whereas 3,3-dimethyl-1-butyne did not give

any coupling product under similar conditions. The

results of experiments varying the pair of an alkyne and

a silane suggest that all the substituents contained in

alkynes and hydrosilanes actually affect the reaction

rate. The reactivity of alkynes decreased in the order

phenylacetylene > 1-hexyne > (trimethylsilyl)acetylene

. 3,3-dimethyl-1-butyne, whereas that of hydrosilane

was Me₂PhSiH, MePh₂SiH > Et₂MeSiH, Et₃SiH >

In the above experiments, Rh₄(CO)₁₂acted as an

efficient catalyst for the silylformylation. In an extreme

case, turnover frequency exceeded 12 000. Although the

efficiency as the catalyst was lower than for Rh₄(CO)₁₂,

it was discovered that the rhodium complexes RhH(CO)-

(PPh₃)₃,Rh(acac)(CO)₂,[Rh(COD)Cl]₂,[Rh(COD)(PPh₃)₂]-

PF₆, [Rh(COD)(DPPB)]PF₆, and [RhCp*Cl₂]₂(acac )

2,4-pentanedionato, COD ) 1,5-cyclooctadiene, and

DPPB ) 1,4-bis(diphenylphosphino)butane; Cp* )

1,2,3,4,5-pentamethylcyclopentadienyl) had sufficient

ability to accomplish the silylformylation. The extent

of regio- and stereoselectivity in the reactions catalyzed

by these complexes was similar to the result observed

in the Rh₄(CO)₁₂-catalyzed one. We should stress that

no carbonylation took place when Co₂(CO)₈, Ru₃(CO)₁₂,

or [Ir(COD)(PPh₃)₂]PF₆was used as a catalyst. The role

of the rhodium catalyst in the silylformylation is an

interesting problem, as described in the section that

follows on Mechanistic Considerations.

Cyclop en ten on e An n u la tion . Silylformylation of

alkynes provides a clear and selective formation of a

â-silyl alkenals as long as starting substrates, alkynes

and hydrosilanes, are mixed in a nearly equal mole

ratio. Though sometimes the presence of small amounts

of side reaction products has been detected by TLC

analyses of the reaction mixtures, their quantities were

usually too small to warrant concentrating our effort

on their isolation. However, appreciable amounts of

i

^tBuMe₂SiH . Pr₃SiH. Thus, the rate of silylformyla-

tion largely depends on the combination of alkynes and

hydrosilanes. The following order of the rate is deduced

from the yield: a pair of phenylacetylenes and Me₂-

PhSiH > that of 1-hexyne and Me₂PhSiH . a pair of

t

phenylacetylenes and BuMe₂SiH > a pair of 1-hexynes

t

and BuMe₂SiH ≈ a pair of (trimethylsilyl)acetylenes

and Me₂PhSiH.

The silylformylation of internal acetylenes also pro-

ceeded smoothly. As shown in Table 3, 2-butyne (16a ),

2-hexyne (16b), 1-phenylpropyne (16c), and diphenyl-

acetylene (16d ) gave the corresponding â-silylalkenals

in good yields. Two regioisomers were formed in the

reaction of unsymmetrically substituted alkynes 16b

and 16c. The regioselectivity seems to be governed by

the steric bulkiness of the substituents; the formyl group

was always introduced at the sp carbon bearing the

(32) (a) Sakai, K.; Ide, J .; Oda, O.; Nakamura, N. Tetrahedron Lett.

1972, 1287. (b) Barnhart, R. W.; Wang, X.; Noheda, P.; Bergens, S.

H.; Whelan, J .; Bosnich, B. J . Am. Chem. Soc. 1994, 116, 1821.

(33) Eilbrachat, P.; Acker, M.; Haedrich, I. Chem. Ber. 1988, 121,

519.

4332 Organometallics, Vol. 16, No. 20, 1997

Matsuda et al.

Sch em e 3. Rh ₄(CO)₁₂-Ca ta lyzed Ca r bon yla tion in

th e P r esen ce of a n Excess of 1-Hexyn e

side reaction products were detected in some combina-

tions of an alkyne and a hydrosilane. For example, no

product other than 11a was observed in the reaction of

1a with ^tBuMe₂SiH at room temperature despite a

prolonged period (65 h) for the completion of the

reaction, whereas interesting byproducts were obtained

in the same reaction at 100 °C. When all of 1a was

consumed after 16 h, the silylformylation product 11a

was obtained as a major component (49% yield) (vide

supra). Unexpectedly, cyclopentenone derivatives 19³⁴

and 20³⁵were also isolated in 23 and 3% yields,

respectively, in addition to 11a . It is apparent that the

formation of 19 and 20 was achieved by the coupling of

t

two molecules of 1a and one molecule each of BuMe₂-

SiH and CO. In fact, the reaction mixture containing

2 mol equiv of 1a and 1 mol equiv of Me₂PhSiH at 100

°C raised the yields of 19 and 20 to 38% and 6%,

respectively (eq 7). This reaction pattern resembles the

of alkynes were present in the reaction mixture. For

example, the silylformylation of 1a with either Me₂-

PhSiH or Et₂MeSiH (1a :silane > 2:1) gave congeners

of 19, which was detected in the ¹H NMR spectra of

their reaction mixture. Their purification through a

silica gel column gave a small amount of 2,4-diphenyl-

cyclopent-2-enone 21³⁴(a few percent based on the

charged 1a ). Similar reactions using 1-hexyne (1f) gave

homologues of 20 as the major cyclocarbonylation

products. The reaction of 1f with Et₂MeSiH (1f:Et₂-

MeSiH ) 3:1) gave 10f and 22a in 48% and 13% yields,

Pauson-Khand type cyclopentenone annulation, which

is attained by the combination of an alkene, an alkyne,

and Co₂(CO)₈or Ti complex in most instances.³⁶

The cyclopentenone annulation was a common side

reaction in the silylformylation when excess amounts

t

respectively. In the silylformylation of 1f with BuMe₂-

(34) It is difficult to determine the precise positions of substituents

of 19 from NMR spectra. We carried out protodesilylation of 19 by KF

in aqueous MeOH at 25 °C for 36 h to give 21 as a single product.

Assignment of 21 was unequivocally performed by the comparison of

spectral data with those of an authentic sample prepared according

to the sequence shown:

SiH, 22b was isolated as a major byproduct in addition

to 11f, though other byproducts, 23-26, were also

isolated as minor products. These results are sum-

marized in Scheme 3.

R ea ct ion s of R h ₄(CO)₁₂w it h H yd r osila n es or

Alk yn es. No visible change was detected by mixing

Rh₄(CO)₁₂and Me₂PhSiH under nitrogen or a CO

atmosphere as described in the following section, whereas

a similar mixture prepared by stirring for more than 8

h under CO pressure (20 kg/cm²) changed from wine

red to straw yellow. At the same time the appearance

of a characteristic singlet (δ 0.81) assignable to a Me₂-

PhSi group was observed with a consumption of the

corresponding amount of Me₂PhSiH in the ¹H NMR

spectrum of this mixture. This fact implies strongly

that a new species is formed as the sole product bearing

a Me₂PhSi group in the mixture. Both starting sub-

strates were completely consumed, and the species

showing a singlet peak at δ 0.81 was formed as the sole

product in the reaction of Rh₄(CO)₁₂with 4 molar equiv

of Me₂PhSiH under CO pressure (20 kg/cm²). Unfor-

(35) The structures of 20 and 22 were determined by spectroscopic

analogy with 19. It is worthwhile to point out that Ojima and

co-workers proposed the structure 27 for the cyclopentenone derivative

isolated as a side reaction product in the silylformylation of 1-hexyne

catalyzed by some Co-Rh bimetallic clusters:^16b

(36) (a) Khand, I. U.; Knox, G. R.; Pauson, P. L.; Watts, W. E.;

Foreman, M. I. J . Chem. Soc., Perkin Trans. 1 1973, 977. (b) Pauson,

P. L. Tetrahedron 1985, 41, 5855. (c) Schore, N. E. Chem. Rev. 1988,

88, 1081. (d) Schore, N. E. Org. React. 1991, 40, 1. (e) Schore, N. E. In

Comprehensive Organic Synthesis; Trost, B. M., Fleming, I., Paquette,

L. A., Eds.; Pergamon Press: Oxford, U.K., 1991; Vol. 5, p 1037. (f)

Hicks, F. A.; Buchwald, S. L. J . Am. Chem. Soc. 1996, 118, 11688.

Rh-Catalyzed Silylformylation of Acetylenic Bonds

Organometallics, Vol. 16, No. 20, 1997 4333

tunately, this species was not isolated as a specific form

because removal of the solvent caused decomposition of

the compound even under this atmosphere. Since the

new compound was stable as long as it was stored in

the original solution under a CO atmosphere (preferably

more than 5 kg/cm²of CO pressure) regardless of the

solvent, CH₂Cl₂, CHCl₃, CDCl₃, C₆H₆, and hexane, a

freshly prepared solution of the new compound was used

under an atmosphere of CO. The product isolated was

divinyl ketones; 29a and 29b were derived from the

corresponding Rh-Si species 28a and 28b, respectively

(eq 9). Insertion of phenylacetylene into the Rh-Si

1

for a spectroscopic study. No H NMR resonance was

detected in the Rh-H region, and the sole singlet peak

assigned to Si-CH₃protons appeared at δ 0.81. The

chemical shift of the latter peak is at lower field than

those of Me₂PhSiH (δ 0.34) and is comparable to those

of Me₂PhSiCl (δ 0.68); this suggests that the Me₂PhSi

group is bonded to electron-withdrawing species. Ortho

protons of the phenyl group were significantly deshield-

ed (δ 7.58-7.65). A ¹³C NMR resonance assigned to the

CO coordinated to Rh was observed at δ 189.37, which

splits into a doublet (J ) 66 Hz) due to a coupling with

a single ¹⁰⁵Rh nuclei. Only terminal CO absorptions

were observed in the IR spectrum (ν_CdO2102, 2049,

2017, and 1982 cm^-1). Thus, the plausible structure of

a new product is a mononuclear silylrhodium carbonyl

complex, Rh(CO)₄SiMe₂Ph (28a ). Similar rhodium-

bond in 28 must be involved at the first stage in the

conversion of 28 to 29. The resulting vinyl-rhodium

species could react with CO to form an acyl-rhodium

intermediate, coupling of which with another molecule

of the vinyl-rhodium species would afford the vinyl

ketones 29. Possibility of the insertion of unsaturated

molecules into a transition-metal-silyl bond has been

pointed out in the catalytic reactions related to

hydrosilylation^42g,43b,44or silylformylation.^10,16aHow-

ever, there has been little direct evidence supporting

the insertion of unsaturated molecules into a metal-

silyl bond in organometallic complexes.^38,45Thus, the

fact that 29 was readily derived from 28 and 1a provides

not only positive evidence of this but also deep insight

into the mechanism of silylformylation.

Another remarkable feature of a rhodium-silyl spe-

cies is that the triorganosilyl group is exchangeable

between 28 and a free hydrosilane under CO pressure

(20 kg/cm²). The presence of this exchanging step was

silyl compounds were isolated from the reaction of Et₂-

MeSiH or BuMe₂SiH with Rh₄(CO)₁₂under CO pres-

t

1

revealed by measurement of the H NMR spectrum of

sure. Cobalt homologues of these complexes,

Co(CO)₄SiMe₃(ν_CdO2090, 2026, 1995 cm^-1) and Co(CO)₄-

SiEt₃(ν_CdO2089, 2026, and 1995 cm^-1), were actually

prepared and subjected to a spectroscopic study.³⁷

These spectral features are comparable to our data for

Rh(CO)₄SiMe₂Ph. To our knowledge, the rhodium car-

bonyl complex 28 is the first example of a nonbridging

rhodium(I)-silyl complex derived from the reaction of

Rh₄(CO)₁₂with R₃SiH, though a series of complexes, Rh-

an equimolar mixture of 28c and Me₂PhSiH in which

28a and ^tBuMe₂SiH appeared increasingly with a

concomitant decrease of 28c and Me₂PhSiH. The

reverse behavior, appearance of 28c and Me₂PhSiH with

a concomitant decrease of 28a and ^tBuMe₂SiH, was

1

observed in the H NMR spectrum of a mixture of 28a

t

and BuMe₂SiH, though the extent of the exchange is

less than that derived from a mixture of 28c and Me₂-

(PR¹) SiR₃, has been isolated and characterized struc-

3 3

(42) Co: (a) Kirch, L.; Orchin, M. J . Am. Chem. Soc. 1959, 81, 3597.

(b) Harrod, J . F.; Chalk, A. J . J . Am. Chem. Soc. 1965, 87, 1133. (c)

Chalk, A. J .; Harrod, J . F. J . Am. Chem. Soc. 1967, 89, 1640. (d) Baay,

Y. L.; MacDiarmid, A. G. Inorg. Chem. 1969, 8, 986. (e) Sommer, L.

H.; Lyons, J . E.; Fujimoto, H. J . Am. Chem. Soc. 1969, 91, 7051. (f)

Bradley, G. F.; Stobart, S. R. J . Chem. Soc., Dalton Trans. 1974, 264.

(g) Reichel, C. L.; Wrighton, M. S. Inorg. Chem. 1980, 19, 3858. (h)

Sisak, A.; Ungva´ry, F.; Marko´, L. Organometallics 1986, 5, 1019.

(43) (a) Ojima, I. In The Chemistry of Organic Silicon Compounds;

Patai, S., Rappoport, Z., Eds.; Wiley: Chichester, U.K., 1989; Vol. 2, p

1479. (b) Ojima, I.; Clos, N.; Donovan, R. J .; Ingallina, P. Organome-

tallics 1990, 9, 3127. (c) Hiyama, T.; Kusumoto, T. In Comprehensive

Organic Synthesis; Trost, B. M., Fleming, I., Paquette, L. A., Eds.;

Pergamon Press: Oxford, U.K., 1991; Vol. 8, p 763.

(44) (a) Schroeder, M. A.; Wrighton, M. S. J . Organomet. Chem.

1977, 128, 345. (b) Archer, N. J .; Haszeldine, R. N.; Parish, R. V. J .

Chem. Soc., Dalton Trans. 1979, 695. (c) Onopchenko, A.; Sabourin,

E. T.; Beach, D. L. J . Org. Chem. 1983, 48, 5101; 1984, 49, 3389. (d)

Duckett, S. B.; Perutz, R. N. Organometallics 1992, 11, 90. (e)

Marciniec, B.; Guli’nski, J . J . Organomet. Chem. 1983, 253, 349. (f)

Seki, Y.; Takeshita, K.; Kawamoto, K.; Murai, S.; Sonoda, N. J . Org.

Chem. 1986, 51, 3890. (g) Takeshita, K.; Seki, Y.; Kawamoto, K.; Murai,

S.; Sonoda, N. J . Org. Chem. 1987, 52, 4864. (h) Seki, Y.; Takeshita,

K.; Kawamoto, K. J . Organomet. Chem. 1989, 369, 117. (i) Tanke, R.

S.; Crabtree, R. H. J . Am. Chem. Soc. 1990, 112, 7984. (j) Hostetler,

M. J .; Butts, M. D.; Bergman, R. G. Organometallics 1993, 12, 65.

(45) (a) Randolf, C. L.; Wrighton, M. S. J . Am. Chem. Soc. 1986,

108, 3366. (b) Wakatsuki, Y.; Yamazaki, H.; Nakano, M.; Yamamoto,

Y. J . Chem. Soc., Chem. Commun. 1991, 703. (c) Seitz, F.; Wrighton,

M. S. Angew. Chem., Int. Ed. Engl. 1988, 27, 289. (d) Brookhart, M.;

Grant, B. E. J . Am. Chem. Soc. 1993, 115, 2151. (e) Yamashita, H.;

Tanaka, M.; Goto, M. Organometallics 1993, 12, 988.

turally by X-ray analyses.³⁸This type of declusteriza-

tion of carbonyl clusters has been established and used

widely as a preparative route for M(CO)_nSiR₃under an

inert-gas atmosphere using other metals.^39-42

It is noteworthy that the isolated Rh(CO)₄SiR₃reacted

readily with phenylacetylene at room temperature even

(37) (a) Anderson, F. R.; Wrighton, M. S. J . Am. Chem. Soc. 1984,

106, 995. (b) Kova´cs, I.; Sisak, A.; Ungva´ry, F.; Marko´, L. Organome-

tallics 1988, 7, 1025.

(38) (a) Thorn, D. L.; Harlow, R. L. Inorg. Chem. 1990, 29, 2017. (b)

Hofmann, P.; Meier, C.; Hiller, W.; Heckel, M.; Riede, J .; Schmidt, M.

U. J . Organomet. Chem. 1995, 490, 51.

(39) (a) Mackay, K. M.; Nicholson, B. K. In Comprehensive Orga-

nometallic Chemistry; Wilkinson, G., Stone, F. G. A., Abel, E. W., Eds.;

Pergamon Press: Oxford, U.K., 1982; Vol. 6, p 1043. (b) Tilley, T. D.

In The Chemistry of Organic Silicon Compounds; Patai, S., Rappoport,

Z., Eds.; Wiley: Chichester, U.K., 1989; p 1415.

(40) Mn: (a) Berry, A. D.; MacDiarmid, A. G. Inorg. Nucl. Chem.

Lett. 1969, 5, 601. (b) Gladysz, J . A.; Williams, G. M.; Tam, W.;

J ohnson, D. L.; Parker, D. W.; Selover, J . C. Inorg. Chem. 1979, 18,

553.

(41) Re: (a)Hoyano, J . K.; Elder, M.; Graham, W. A. G. J . Am. Chem.

Soc. 1969, 91, 4568. (b) Elder, M. Inorg. Chem. 1970, 9, 762. (c) Webb,

M. J .; Graham, W. A. G. J . Organomet. Chem. 1975, 93, 119. (d)

Couldwell, M. C.; Simpson, J .; Robinson, W. T. J . Organomet. Chem.

1976, 107, 323. (e) Cowie, M.; Bennett, M. J . Inorg. Chem. 1977, 16,

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10, 2387.

4334 Organometallics, Vol. 16, No. 20, 1997

Matsuda et al.

Sch em e 4. Rever sible Exch a n ge of a

Tr ior ga n osilyl Gr ou p

Sch em e 5. Rea ction s of Rh ₄(CO)₁₂w ith 1a u n d er

CO P r essu r e

PhSiH in the same reaction time. The results obtained

from both experiments suggest that exchange of a

triorganosilyl group between 28 and a hydrosilane is a

reversible process, the equilibrium point of which

depends on a combination of two triorganosilyl groups.

In the combination of 28c and Me₂PhSiH, an equilib-

rium lies predominantly to the side of 28a (28a :28c ≈

88:12).⁴⁶The process of this equilibration is elucidated

by the intervention of disilylrhodium(III) species 30

(Scheme 4). This type of silyl group exchange has been

well-documented in cobalt complexes under thermal^42e,47

and photochemical^37b,43gconditions.

coordinated alkyne was not replaced by a free one in

solution. The stability of 32 in a CDCl₃solution was

confirmed by the comparison of ¹H NMR spectra of 32a

and 32b containing 1 mol equiv of 1g and 1a , respec-

tively.

The reaction of this dinuclear species, 32a , with Me₂-

PhSiH under CO pressure gave rise to the formation of

some amount of silylformylation product 2a (26%), but

the rate was substantially slower than that of the

reaction of Rh(CO)₄SiMe₂Ph with phenylacetylene un-

der CO pressure (eq 10). The silylrhodium complex 28a

The reaction of phenylacetylene with a stoichiometric

amount of Rh₄(CO)₁₂afforded multimetallic rhodium

carbonyls coordinated to phenylacetylene, presumably

Rh₄(CO)₁₀(phenylacetylene) (31), under either an Ar or

a CO atmosphere, the structure of which was deduced

from the known^48,49Rh₄(CO)₁₀(diphenylacetylene): ¹H

NMR δ 7.00-7.30 (m, Ph), 9.16 (quint, CH). Complex

31 reacted with Me₂PhSiH to form (E)-3 as the sole

organic product, and no type of silylformylation occurred

under a CO atmosphere. When 20 kg/cm²of CO

pressure was applied to a solution of the tetranuclear

complex 31, the cluster was decomposed to a rhodium

carbonyl having a bridging CO ligand and coordinated

phenylacetylene. In fact, complex 32a was isolated as

the sole product (yellow-brown blocks from CH₂Cl₂/

hexane) in the reaction of 1a with Rh₄(CO)₁₂under CO

pressure (20 kg/cm²), irrespective of the quantity of 1a

used. The structure of 32a was elucidated on the basis

was formed concomitantly in 44% yield. Although it

cannot be completely excluded that there is an unknown

pathway leading from 32a to 2a , the poor stoichiometry

for this formation and the concomitant formation of Rh-

(CO)₄SiMe₂Ph suggest that the reaction of 32 with Me₂-

PhSiH under CO pressure gives Rh(CO)₄SiMe₂Ph (28a )

and free phenylacetylene. As a result, the 1a liberated

is silylformylated under the reaction conditions cata-

lyzed by 28a .

1

of IR and H and ¹³C NMR spectroscopy and elemental

Mech a n istic Con sid er a tion s of Silylfor m yla tion .

It is conceivable that the mechanism for silylformylation

of alkynes is closely related to that for hydrosilylation.⁴³

However, the greatest discrepancy between these reac-

tions is that the former reaction of 1-alkynes is ex-

tremely regioselective as well as stereoselective, whereas

the latter gives a mixture of regio- and stereoisomers

(eq 2). It is interesting to reveal the role of rhodium

metal in the catalytic cycle of silylformylation. First of

all, a couple of deuterium labeling reactions using

deuteriophenylacetylene (1a -D) and Me₂PhSiD as a

reactant were designed to confirm the origin of the

formyl proton. Alkenal 2a -D_(formyl)(Z:E ) 87:13) deu-

terated (>98%) at the formyl carbon was selectively

given in 73% yield from the reaction of 1a with Me₂-

analysis. It is slightly different from cobalt dinuclear

complexes.^16a,50Moreover, no specific indication of CO

insertion was observed at this stage, while there are

some precedents reporting the formation of such com-

plexes as 33⁵¹and 34^52,53in the reaction of metal

carbonyls with alkynes. The coordination of alkynes to

rhodium metal in 32 is relatively stable, and the

(46) The time required for the equilibrium in these controlled

experiments was far longer than the silylformylation. Phenylacetylene

may act as a catalyst for the exchange between silyl groups.

(47) Harrod, J . F.; Chalk, A. J . In Organic Synthesis via Metal

Carbonyls; Wender, I., Pino, P., Eds.; Wiley-Interscience: New York,

1977; Vol. 2, p 673.

(48) (a) Iwashita, Y.; Tamura, F. Bull. Chem. Soc. J pn. 1970, 43,

1517. (b) Booth, B. L.; Else, M. J .; Fields, R.; Haszeldine, R. N. J .

Organomet. Chem. 1971, 27, 119.

(49) (a) Dahl, L. F.; Smith, D. L. J . Am. Chem. Soc. 1962, 84, 2450.

(b) Ojima, I.; Clos, N.; Donovan, R. J .; Ingallina, P. Organometallics

1991, 10, 3211.

(50) (a) Dickson, R. S.; Fraser, P. J . Adv. Organomet. Chem. 1974,

12, 323. (b) Aime, S.; Milone, L.; Rossetti, R.; Stanghellini, P. L. Inorg.

Chim. Acta 1977, 22, 135.

(52) (a) Dyke, A. F.; Knox, S. A. R.; Naish, P. J .; Taylor, G. E. J .

Chem. Soc., Dalton Trans. 1982, 1297. (b) J ohnson, K. A.; Gladfelter,

W. L. J . Am. Chem. Soc. 1991, 113, 5097. (c) Burn, M. J .; Kiel, G. Y.;

Seils, F.; Takats, J .; Washington, J . J . Am. Chem. Soc. 1989, 111, 6850.

(53) Dickson, R. S.; Gatehouse, B. M.; Nesbit, M. C.; Pain, G. N. J .

Organomet. Chem. 1981, 215, 97.

(51) Burt, R.; Cooke, M.; Green, M. J . Chem. Soc. A 1970, 2981.

Rh-Catalyzed Silylformylation of Acetylenic Bonds

Organometallics, Vol. 16, No. 20, 1997 4335

Sch em e 6. Silylfor m yla tion In d u ced by 28

PhSiD under conventional silylformylation conditions

(eq 11). Alkenal 2a -D_(vinyl)(Z:E ) 57:43) deuterated

(>94%) at the vinyl carbon was selectively isolated from

the reaction of 1a -D with Me₂PhSiH under similar

conditions (eq 12).⁵⁴This observation shows clearly that

the hydrogen atom of the formyl group is derived from

the hydrosilane used and that there is minimal scram-

bling of hydrogen atoms between a hydrosilane and a

terminal acetylene in Rh-catalyzed silylformylation.

Second, the course of silylformylation was monitored

using a spectroscopic method. As noted previously,

hydrosilylation of alkynes becomes a serious competitive

reaction in silylformylations unless the reaction is

carried out under CO pressure. An interesting observa-

tion was obtained in the experiments using Rh₄(CO)₁₂,

1a , and Me₂PhSiH in a ratio of 1:4:4, that is, stoichio-

metric amounts of 1a and the silane based on one Rh

atom. Silylformylation of 1a proceeded to give 2a

selectively with recovery of Rh₄(CO)₁₂in the reaction

under CO pressure (20 kg/cm²). When both substrates

were mixed at once in a CDCl₃solution of Rh₄(CO)₁₂

under a CO atmosphere, smooth progress of the silyl-

rhodium species does not exist at all or that the rate of

the interaction is too rapid to be detected on the time

scale of H NMR under a CO atmosphere. Despite no

1

clear indication of the presence of intermediate detect-

1

able in the H NMR spectrum of a mixture resulting in

the silylformylation, the fact that silylformylation pro-

ceeds smoothly suggests that each step of the catalytic

cycle of silylformylation occurs more rapidly than the

1

time scale of H NMR.

In contrast to the results described above, 28 was

selectively formed in the reaction of Rh₄(CO)₁₂with 4

mol equiv of R₃SiH under CO pressure (20 kg/cm²). The

solution containing 28 resulted in silylformylation

regardless of a stoichiometric or catalytic reaction to

give the corresponding product in the presence of equal

amounts of 1 and a hydrosilane under CO pressure. An

interesting behavior of 28 was also observed when 28

and a hydrosilane have different types of triorganosilyl

groups. For example, the two silylformylation products

2a and 11a , and the two silyl-rhodium species 28a and

28c, were obtained from two stoichiometric reactions

under CO pressure (20 kg/cm²), that of ^tBuMe₂SiH with

Rh(CO)₄SiMe₂Ph (28a ) and that of Me₂PhSiH with Rh-

(CO)₄Si^tBuMe₂(28c) in the presence of an equimolar

amount of 1a as shown in Scheme 6. It is interesting

that the relative ratios of these products were almost

identical in these two independent experiments. This

result suggests that exchange of silyl groups between

R₃SiH and Rh(CO)₄SiR′₃occurs prior to the insertion

of phenylacetylene into the Rh-Si bond. In particular,

the fact that the ratios of 2a to 11a are identical in the

two separate reactions seems to reflect that the relative

quantities of 28a and 28c in both reaction systems are

controlled by a certain equilibrium triggered by the

1

formylation of 1a was observed by monitoring the H

NMR spectra of the mixture; this clearly showed that

2a was formed as a major product with concomitant

formation of small amounts of hydrosilylation products

and Me₂PhSiOH. A similar result was obtained when

1a was added into the solution provided by mixing Me₂-

PhSiH and Rh₄(CO)₁₂under a CO atmosphere for 30

min prior to use. In sharp contrast to these results,

when Me₂PhSiH was treated with the solution prepared

from Rh₄(CO)₁₂and 1a under a CO atmosphere, the sole

reaction observed was not silylformylation but hydrosi-

lylation. These results unequivocally suggest that the

prior interaction among a silane, a rhodium complex,

and CO is important in silylformylation.

Disappearance of the spin-spin coupling between the

1

SiCH₃and SiH protons was observed in the H NMR

spectrum of a solution containing Me₂PhSiH and Rh₄-

(CO)₁₂in the ratio 4:1 under an Ar atmosphere. This

finding indicates that rhodium species interact revers-

ibly with the Si-H bond, whereas the inherent signals

assigned to Me₂PhSiH itself did not change at all in a

similar sample as long as the solution was stored under

CO atmosphere. This fact is elucidated by an assump-

tion either that interaction between Me₂PhSiH and

t

presence of free Me₂PhSiH or BuMe₂PhSiH. Thus, the

results shown in Scheme 4 suggest the presence of a

preequilibrium between the hydrosilane and the rhod-

ium-silyl complex. The resulting mixture of 28a and

28c reacts with phenylacetylene and CO, resulting in

(54) The deuterium content of these compounds was determined by

¹H NMR integration of the residual proton signals at the site of labeling

relative to the intensity of another signal assigned to one proton at an

unlabeled position.

4336 Organometallics, Vol. 16, No. 20, 1997

Matsuda et al.

Sch em e 7. Silylfor m yla tion In d u ced by Rh od iu m

Sp ecies

They pointed out that the heteronuclear cluster frame-

work plays an important role in the smooth proceeding

of reactions.^16aHowever, we confirmed that several

monometallic rhodium complexes, RhH(CO)(PPh₃)₃,

[Rh(COD)(DPPB)]PF₆, and Rh(acac)(CO)₂, also cata-

lyzed the silylformylation, though the reaction rate was

substantially lower than that with Rh₄(CO)₁₂as de-

scribed above. We conclude that the presence of Rh

metal, regardless of the nuclearity, is essential in order

to catalyze the silylformylation of alkynes. The idea

that Rh₄(CO)₁₂generates mononuclear metal carbonyl

species such as Rh(CO)₄SiR₃is rather more reasonable

than the notion that RhH(CO)(PPh₃)₃produces multi-

nuclear metal carbonyl species, since metal carbonyl

clusters have generally been known to decompose to

metal carbonyl complexes with lower nuclearity under

CO pressure. In spite of the claim⁵⁵that the cluster

framework of Rh₄(CO)₁₂is retained in the hydroformy-

lation, it is difficult to assume that the nuclearity of Rh₄-

(CO)₁₂remains intact during the silylformylation of

alkynes on the basis of our observations on stoichio-

metric reactions of Rh₄(CO)₁₂with R₃SiH or pheny-

lacetylene under CO pressure.

Thus, the catalytic cycles A and B for silylformylation

are proposed as one persuasive possibility (Scheme 8).

In cycle A, Rh(CO)₄SiR₃(28), which is initially formed

by the reaction of R₃SiH with Rh₄(CO)₁₂and equilibrates

with 40 in the reaction system, is allowed to react with

acetylene to form the vinyl-rhodium species 37. Inser-

tion of CO between the carbon-rhodium bond of 37

affords the acyl-rhodium intermediate 38. Oxidative

addition of a Si-H bond to the rhodium metal is

followed by reductive elimination of the silylformylation

product and regeneration of Rh(CO)₄SiR₃in the pres-

ence of R₃SiH. When hydrosilane is absent, 38 reacts

with another molecule of 37 to afford divinyl ketones

as described previously (eq 9). Recent demonstration

of alkene insertion into a Rh-Si bond³⁸makes it

possible to propose the process from 35 to 37. Moreover,

the pathway to form 38 from 35 through continuous

insertion of alkyne and CO is supported by the evidence

of eq 9 and the reported result that manganese acyl

complexes (43) are obtained from the reaction of Mn-

(CO)₅SiMe₃with aldehydes as shown in eq 13.⁵⁶The

Ta ble 4. Rela tive Efficien cy of Ca ta lyst

P r ecu r sor s in Silylfor m yla tion of 1a ^a

entry

no.

substrate/ yield of 2a turnovers/

catalyst

Rh₄(CO)₁₂

28a

28c

Rh

(%)^b

min

1

2

3

4

5

84

86

82

83

82

88

70

65

16^c

3.4

3.8

2.9

2.7

0.2

32a

RhH(CO)(PPh₃)₃

a

Reactions were conducted in

a benzene (7 mL) solution

containing the fixed mole ratio 1a :Me₂PhSiH:[Rh] ) 83:83:1 at

b

25 °C for 20 min under CO pressure (20 kg/cm²). Isolated yield.

^cReaction time was increased to 1 h because of the low conversion

within the prescribed time.

the predominant formation of 2a . Since a mixture of

free silanes (Me₂PhSiH:^tBuMe₂SiH ≈ 12:88) might be

present in the reaction mixture at that stage, these

hydrosilanes contribute to the generation of 28a and 28c

in a ratio of close to 13:87 in the final step of the

reactions.

Both of the well-characterized complexes 28 and 32

readily interacted with a mixture containing an equimo-

lar amount of 1a and Me₂PhSiH under CO pressure to

give 2a as selectively as did Rh₄(CO)₁₂itself. All

complexes used as starting substrates were recovered

intact after the completion of silylformylation, as shown

in Scheme 7. This suggests that complexes 28 and 32

are uniformly effective as catalysts for silylformylation.

However, the result of 32b suggests strongly that the

alkyne molecules contained in 32 are not incorporated

directly as a component of silylformylation. This point

is also supported by the finding that the major product

is 2f (2f:2a ≈ 3:1) in the reaction of 32a with a

stoichiometric mixture of Me₂PhSiH and 1f, despite the

overwhelming priority of 1a in the catalytic competitive

silylformylation (eq 5). All these species showed cata-

lytic ability comparable to that of Rh₄(CO)₁₂for silyl-

formylation at 25 °C despite the apparent difference in

behavior between 28 and 32 in the stoichiometric

reactions (Table 4). In contrast to these precursors

derived from Rh₄(CO)₁₂, a stable mononuclear complex,

RhH(CO)(PPh₃)₃showed far inferior catalytic efficiency

at 25 °C, though the efficiency improved in the reactions

under practical operation at 100 °C.

final stage of forming 2, 8, 9, 10, 11, 12, or 13 from 38

is also supported by the evidence that the cobalt-acyl

complex liberates aldehyde in the interaction with

hydrosilane.⁵⁷

An alternative cycle, shown in cycle B of Scheme 8,

can be proposed. Complex 40 derived from 35 by the

oxidative addition of R₃SiH interacts directly with an

alkyne to form 42 via 41. The insertion of CO into the

rhodium-carbon(vinyl) bond of 42 leads to 39. The rest

of the cycle is shared with cycle A. It is difficult at

present to conclude unequivocally which of these cycles

From these results, we conclude that the most plau-

sible catalytic cycle involves a mononuclear Rh(CO)₄SiR₃

as an intermediate at the present stage. The catalytic

cycle is similar to the Murai reaction, the cobalt-

catalyzed silylformylation of alkenes,¹⁰and is compa-

rable to well-known cobalt- or rhodium-catalyzed hy-

droformylation of alkenes and alkynes. Ojima and co-

workers reported that similar silylformylation of alkynes

was catalyzed by a mixed-metal cluster, Co₂Rh₂(CO)₁₂.

(55) Rosas, N.; Ma´rquez, C.; Herna´ndez, H.; Go´mez, R. J . Mol. Catal.

1988, 48, 59.

(56) Brinkman, K. C.; Gladysz, J . A. Organometallics 1984, 3, 147.

(57) Wegman, R. W. Organometallics 1986, 5, 707.

Rh-Catalyzed Silylformylation of Acetylenic Bonds

Organometallics, Vol. 16, No. 20, 1997 4337

Sch em e 8. Ca ta lytic Cycle for Silylfor m yla tion ^a

a

Ligands on rhodium are eliminated for clarification.

Sch em e 9. P la u sible P a th w a y To F or m

Cyclop en ten on e Der iva tives

Sch em e 10. P la u sible P a th w a y To F or m 26

starting from 38, as shown in Scheme 10. Analogous

elucidation from 42 and 39 leads to the same products.

Con clu sion

dominates silylformylation because the observable steps

such as the formation of 28 and silyl exchange in

Scheme 4 require far longer time than that sufficient

for silylformylation.

Detailed studies of “silylformylation” of alkynes at-

tained by the interaction of hydrosilane and CO have

been presented in which triorganosilyl groups are

introduced into an acetylenic triple bond in a substan-

tially (Z)-selective mode. The presence of a catalytic

amount of rhodium complex is crucial for smooth

incorporation of CO regardless of the forms of the

precursors over a considerably wide range of complexes.

The reactions proceed selectively to form the sole

regioisomer formylated on the internal sp carbon of

1-alkynes in a controlled mole ratio (1:1) of alkyne to

hydrosilane. When an excess of alkyne is present in

this reaction, a new type of cyclopentenone annulation

is realized, despite a relatively poor yield. These two

types of carbonylations are elucidated consistently by

postulation of the insertion of an alkyne into a Rh-Si

bond as a key catalytic step. Mechanistic aspects aside,

however, the present novel reaction composed of an

alkyne, hydrosilane, and CO should prove to be a simple

and efficient approach to form 2. The structure of 2 is

of interest as a versatile building block for the synthesis

In whichever cycle silylformylation may take place,

the findings obtained so far are consistent with both of

those shown in Scheme 8. Furthermore, the postulated

key intermediates 37 or 42 and 38 or 39 are connectable

to the sequence for the formation of the products

contained in eq 7 and Scheme 3. The pathways branch-

ing from 37 and 38 are illustrated in Schemes 9 and

10, respectively. Analogous elucidation from 42 and 39

leads to the same products. The second vinyl complex

of Rh, 44, is formed by the immediate insertion of the

second molecule of alkyne into the Rh-C bond of 37.

The subsequent insertion of CO into the resultant Rh-C

bond of 44 gives 45, which cyclizes to form 46. The final

products 19, 20, 22, 23, 24, and 25 are derived from

47, which represents some isomers generated by proto-

or silatropy from 46 and subsequent oxidative addition

of R₃SiH to Rh metal (Scheme 9). The formation of

divinyl ketone 26 is also described by a similar sequence

of complex molecules via a Peterson olefination,^24a,26

a

4338 Organometallics, Vol. 16, No. 20, 1997

Matsuda et al.

Nazarov type cyclopentenone annulation,⁵⁸or a Trost

type cyclopentane annulation.⁵⁹

Elemental analyses were performed by the Microanalytical

Center of Kyoto University.

Ca r bon yla tion s. All carbonylation reactions were carried

out in glass tubes held in a 100 mL stainless steel autoclave.

The procedure for the synthesis of 2a is described as a typical

example.

Exp er im en ta l Section

Gen er a l Con sid er a tion s. All carbonylation reactions

were carried out in a glass tube held in a 100 mL stainless

steel autoclave under carbon monoxide unless otherwise

indicated. Anhydrous solvents were transferred via an oven-

dried syringe. The following solvents and reagents were

distilled prior to use: tetrahydrofuran (THF) from sodium

benzophenone ketyl and N,N-dimethylformamide (DMF) from

calcium hydride. Benzene (thiophene free) and all other

solvents were utilized at their commercial level of purity. The

following preparations were based on standard literature

procedures: Rh₄(CO)₁₂,⁶⁰RhCl(PPh₃)₃,⁶¹RhH(CO)(PPh₃)₃,⁶²

Rh(acac)(CO)₂,⁶³[Rh(COD)Cl]₂,⁶⁴[Rh(COD)(PPh₃)₂]PF₆,⁶⁵[Rh-

(COD)(DPPB)]PF₆,⁶⁶[RhCp*Cl₂]₂,⁶⁷Ru₃(CO)₁₂,⁶⁸[Ir(COD)-

(PPh₃)₂]PF₆,⁶⁹and 1j.⁷⁰Dicobalt octacarbonyl (Co₂(CO)₈) was

purchased from Strem. Acetylenes except for 1j and silanes

were obtained from Aldrich, Lancaster, Tokyo Kasei, Shin-

etsu Chemicals, or Petrarch. These were used as received.

All reactions were monitored by thin-layer chromatography

carried out on 0.25 mm E. Merck silica gel plates (60 F-254)

using UV light as the visualizing agent and 7% ethanolic

phosphomolybdic acid and heat as the developing agent. E.

Merck silica gel (60, particle size 0.063-0.200 mm) was used

for column chromatography. Medium-pressure preparative

liquid chromatography was performed on a YFLC-600 system

equipped with a silica gel (particle size 0.025-0.040 mm)

column. Preparative thin-layer chromatography (PTLC) sepa-

rations were carried out on 2 mm E. Merck silica gel plates

(60F-254).

Proton nuclear magnetic resonance (¹H NMR) data were

obtained at 200 MHz on a Varian GEM-200 or at 500 MHz on

a Varian VXR-500 spectrometer. Chemical shifts are reported

in δ units, in parts per million (ppm) relative to the singlet at

7.26 ppm for chloroform-d. Splitting patterns are designated

as follows: s, singlet; d, doublet; t, triplet; q, quartet; quint,

quintet; sext, sextet; m, multiplet; b, broad. Coupling con-

stants are reported in hertz (Hz). Carbon-13 nuclear magnetic

resonance (¹³C NMR) data were obtained at 50 MHz on a

Varian GEM-200 or at 125.7 MHz on a Varian VXR-500 and

are reported in ppm with the center line of a triplet at 77.00

ppm for chloroform-d. Routine ¹³C spectra were fully de-

coupled by broad-band decoupling. Infrared data were re-

corded in 0.2 mm path length sodium chloride cavity cells on

a J ASCO IR-810 spectrometer. Absorbance frequencies are

reported in reciprocal centimeters (cm^-1). Mass spectra were

recorded on a J EOL J MS-AX505H gas chromatograph-mass

spectrometer using 2-methylpropane gas for chemical ioniza-

tion (CI) or electron impact (EI) at 70 eV. Melting points were

obtained on a Bu¨chi 510-K apparatus in sealed capillary tubes

and are uncorrected. Boiling points are also uncorrected.

Ku¨gelrohr distillation was performed in a Bu¨chi KR-3 oven.

R h ₄(CO)₁₂-Ca t a lyzed Silylfor m yla t ion of 1a w it h

Me₂P h SiH (P r oced u r e 1). A glass tube (28 mm o.d.) fitted

with a stirring bar was charged with Rh₄(CO)₁₂(0.012 g, 0.016

mmol) and benzene (8 mL) saturated by CO. The tube was

placed in a 100 mL stainless steel autoclave. The reactor was

pressurized by CO to 20 kg/cm². The contents were stirred

for 5 min at ambient temperature, and then the pressurized

CO was purged under a hood. Into this tube were added

subsequently Me₂PhSiH (1.210 g, 8.89 mmol) in C₆H₆(3 mL),

1a (0.937 g, 9.17 mmol) in C₆H₆(3 mL), and Et₃N (0.831 g,

8.21 mmol) through a syringe needle at ambient temperature.

The reactor was pressurized again by CO to 20 kg/cm². The

contents were stirred for 2 h at 100 °C and cooled to ambient

temperature. After excess CO was purged under a hood, the

reaction mixture was concentrated under reduced pressure.

The residual oily liquid was chromatographed on silica gel

using hexane/AcOEt (98/2) as an eluent to give an oily liquid.

The subsequent bulb-to-bulb distillation of this oil gave pure

3-(dimethylphenylsilyl)-2-phenylpropenal (2a ; 2.115 g, 89%,

Z:E ) 88:12, bp 165 °C/0.1 Torr) as a pale yellow oil. Both Z

and E stereoisomers were isolated by iterative column chro-

matography on silica gel. (Z)-2a : IR (CCl₄) 2730 (CHO), 1693

1

(CdO), 1580 (CdC), 1560 (CdC), and 1250 (SiCH₃) cm^-1; H

NMR (200 MHz, CDCl₃) δ 0.61 (s, 6H, Si(CH₃)₂), 7.29 (s, 1H,

dCH), 7.38-7.45 (m, 8H, Ph), 7.58-7.65 (m, 2H, Ph), and

10.08 (s, 1H, CHO); ¹³C NMR (50 MHz, CDCl₃) δ -0.74

(SiCH₃), 128.17 (Ph), 128.33 (Ph), 128.39 (Ph), 128.61 (Ph),

129.69 (Ph), 133.78 (Ph), 137.47 (Ph, ipso), 137.92 (Ph, ipso),

152.00 (dCH), 154.54 (dC, q), and 192.46 (CHO). Anal. Calcd

for C₁₇H₁₈OSi: C, 76.64; H, 6.81. Found: C, 76.85; H, 7.01.

(E)-2a : IR (CCl₄) 2730 (CHO), 1693 (CdO), 1600 (CdC), 1582

1

(CdC), and 1252 (SiCH₃) cm^-1; H NMR (200 MHz, CDCl₃) δ

0.19 (s, 6H, Si(CH₃)₂), 7.05-7.13 (m, 3H, Ph), 7.13 (s, 1H,

dCH), 7.35-7.40 (m, 6H, Ph), 7.40-7.50 (m, 2H, Ph), and 9.71

(s, 1H, CHO); ¹³C NMR (50 MHz. CDCl₃) δ -2.48 (SiCH₃),

128.08 (Ph), 128.15 (Ph), 128.45 (Ph), 129.33 (Ph), 129.56 (Ph),

133.79 (Ph), 135.31 (Ph, ipso), 137.48 (Ph, ipso), 154.11 (dCH),

157.14 (dC, q), and 194.52 (CHO).

Silylformylations of 1a catalyzed by other complexes were

carried out on a 1 mmol scale in a manner similar to procedure

1 in the presence of Me₂PhSiH. Results are summarized in

the sequence of solvent, yield of 2a , and Z:E as follows: Co₂-

(CO)₈(C₆H₆, 0%, s), Ru₃(CO)₁₂(C₆H₆, 0%, s), [Ir(COD)-

(PPh₃)₂]PF₆(CH₂Cl₂, 0%, s), RhCl(PPh₃)₃(C₆H₆, 4%, 80:20),

RhH(CO)(PPh₃)₃(C₆H₆, 87%, 90:10), Rh(acac)(CO)₂(C₆H₆, 87%,

90:10), [Rh(COD)(DPPB)]PF₆(CH₂Cl₂, 73%, 88:12), and [Rh-

(COD)Cl]₂(C₆H₆, 85%, 92:8), [RhCp*Cl₂]₂(CH₂Cl₂, 41%, 88:

12).

R h ₄(CO)₁₂-Ca t a lyzed H yd r osilyla t ion of 1a w it h

Me₂P h SiH u n d er a n Ar Atm osp h er e. Into a hexane (5 mL)

solution of Rh₄(CO)₁₂(0.0096 g, 0.0128 mmol) in a 30 mL round

flask fitted with a stirrer bar, a reflux condenser, and a

dropping funnel was added dropwise a hexane (3 mL) solution

of 1a (0.333 g, 3.26 mmol) and Me₂PhSiH (0.448 g, 3.29 mmol)

at 25 °C. Since a slightly exothermic reaction started im-

mediately after the addition of the first few drops, the rest of

the solution was added at a rate that maintained the temper-

ature of the contents below 50 °C. After the complete addition

of substrates, the mixture was stirred for a further 2 h at 25

°C. Volatiles were evaporated under reduced pressure, and

the residue was distilled to give 0.567 g (73%) of a mixture of

3 and 4 ((E)-3:(Z)-3:4 ) 31:56:13) as a colorless liquid (bp 110

°C/0.2 Torr).^45c,71

(58) (a) J ones, T. K.; Denmark, S. E. Helv. Chim. Acta 1983, 66,

2377. (b) J ones, T.; Denmark, S. E. Helv. Chim. Acta 1983, 66, 2397.

(59) Trost, B. M.; Mignani, S. M.; Nanninga, T. N. J . Am. Chem.

Soc. 1988, 110, 1602.

(60) Martinengo, S.; Giordano, G.; Chini, P. Inorg. Synth. 1990, 28,

242.

(61) Osborn, J . A.; Wilkinson, G. Inorg. Synth. 1990, 28, 77.

(62) Ahmad, N.; Levison, J . J .; Robinson, S. D.; Uttley, M. F. Inorg.

Synth. 1990, 28, 82.

(63) Bonati, F.; Wilkinson, G. J . Chem. Soc. 1964, 3156.

(64) Giordano, G.; Crabtree, R. H. Inorg. Synth. 1990, 28, 88.

(65) Schrock, R. R.; Osborn, J . A. J . Am. Chem. Soc. 1971, 93, 2397.

(66) Anderson, M. P.; Pignolet, L. H. Inorg. Chem. 1981, 20, 4101.

(67) Kang, J . W.; Maitlis, P. M. J . Am. Chem. Soc. 1969, 91, 5970.

(68) Bruce, M. I.; J ensen, C. M.; J ones, N. L. Inorg. Synth. 1990,

28, 216.

(69) Haines, L. M.; Singleton, E. J . Chem. Soc., Dalton Trans. 1972,

1891.

(70) Brandsma, L. In Preparative Acetylenic Chemistry; Elsevier:

Amsterdam, 1972; p 135.

(71) Watanabe, H.; Kitahara, T.; Motegi, T.; Nagai, Y. J . Organomet.

Chem. 1977, 139, 215.

Rh-Catalyzed Silylformylation of Acetylenic Bonds

Organometallics, Vol. 16, No. 20, 1997 4339

Silylfor m yla tion of 1a in th e P r esen ce of a n Excess

of Me₂P h SiH. A C₆H₆(12 mL) solution containing Rh₄(CO)₁₂

(0.0073 g, 0.009 76 mmol), Me₂PhSiH (0.740 g, 5.43 mmol),

1a (0.260 g, 2.54 mmol), and Et₃N (0.214 g, 2.11 mmol)

prepared in a way similar to procedure 1 was stirred for 13 h

at 95 °C under CO pressure (20 kg/cm²) and cooled to ambient

temperature. The residue obtained by evaporation of volatiles

from the reaction mixture was chromatographed on a silica

gel column to give a viscous mixture (0.711 g) containing 2a

as a pale yellow oily liquid. Further purification of this sample

was not carried out. Its ¹H NMR spectrum allowed us to

deduce that the mixture contains 2a , 5, and, 6 as major

products. 5 (prepared from catalytic hydrogenation (Pd/C, H₂,

AcOEt) of 2a ): bp 110 °C/0.1 Torr (colorless oil); IR (CCl₄) 2700

(CHO), 1723 (CdO), 1600 (aromatic CdC), and 1248 (SiCH₃)

mmol), ^tBuMe₂SiH (0.480 g, 4.12 mmol), 1a (0.436 g, 4.27

mmol), and Et₃N (0.412 g, 4.07 mmol) prepared in a way

similar to procedure 1 was stirred for 65 h at 25 °C under CO

pressure (20 kg/cm²). The residue obtained by evaporation of

volatiles from the reaction mixture was purified by chromato-

graphic separation and bulb-to-bulb distillation to give 11a

(0.830 g, 82%, bp 145 °C/0.3 Torr, Z:E ) 98:2) as a pale yellow

liquid. (Z)-11a : IR (CCl₄) 2740 (CHO), 1695 (CdO), 1582

(CdC), 1565 (CdC), and 1253 (SiCH₃) cm^-1

;

¹H NMR (200

t

MHz, CDCl₃) δ 0.30 (s, 6H, Si(CH₃)₂), 0.99 (s, 9H, Bu), 7.19

(s, 1H, dCH), 7.37 (s, 5H, Ph), and 10.09 (s, 1H, CHO)

(additional signals for (E)-11a : δ -0.19 (s, 6H, Si(CH₃)₂), 0.93

t

(s, 9H, Bu), 7.05 (s, 1H, dCH), 7.37 (s, 5H, Ph), and 9.68 (s,

1H, CHO)); ¹³C NMR (50 MHz, CDCl₃) δ -3.61 (SiCH₃), 17.00

(^tBu, q), 26.22 (^tBu), 128.30 (Ph), 128.47 (Ph), 137.81 (Ph, ipso),

153.11 (dCH), 155.55 (dC, q), and 192.83 (CHO). Anal. Calcd

for C₁₅H₂₂OSi: C, 73.11; H, 9.00. Found: C, 73.06; H, 9.13.

3-(Dim eth yleth oxysilyl)-2-p h en ylp r op en a l (12). With

Rh₄(CO)₁₂(0.0285 g, 0.0381 mmol), (EtO)Me₂SiH (0.647 g, 6.21

mmol), 1a (0.616 g, 6.03 mmol), and Et₃N (0.665 g, 6.57 mmol)

as starting materials, a mixture of 12 and 14 (0.983 g, 70%,

bp 140 °C/0.2 Torr, (Z)-12:(E)-12:14 ) 1:1:1) was obtained as

a pale yellow liquid after immediate distillation of the mixture.

IR (CCl₄): 2735 (CHO), 1698 (CdO), 1592 (CdC), 1565 (CdC),

and 1253 (SiCH₃) cm^-1. (Z)-12: ¹H NMR (500 MHz, CDCl₃) δ

0.40 (s, 6H, Si(CH₃)₂), 1.24 (t, J ) 7.1 Hz, 3H, CH₃), 3.76 (q, J

) 7.1 Hz, 2H, CH₂), 6.97 (s, 1H, dCH), 7.2-7.4 (m, 5H, Ph),

and 10.20 (s, 1H, CHO). (E)-12: ¹H NMR (500 MHz, CDCl₃)

δ 0.03 (s, 6H, Si(CH₃)₂), 1.14 (t, J ) 7.1 Hz, 3H, CH₃), 3.60 (q,

J ) 7.1 Hz, 2H, CH₂), 6.91 (s, 1H, dCH), 7.3-7.6 (m, 5H, Ph),

and 9.70 (s, 1H, CHO). 14: ¹H NMR (500 MHz, CDCl₃) δ 0.32

(s, 3H, SiCH₃), 0.37 (s, 3H, SiCH₃), 1.23 (t, J ) 7.1 Hz, 3H,

CH₃), 3.68 (dq, J ) 9.3 (d) and 7.1 (q) Hz, 1H, OCH₂), 3.79

(dq, J ) 9.3 (d) and 7.1 (q) Hz, 1H, OCH₂), 6.06 (s, 1H, OCH),

6.59 (s, 1H, dCH), and 7.3-7.45 (m, 5H, Ph).

1

cm^-1; H NMR (200 MHz, CDCl₃) δ 0.11 (s, 3H, SiCH₃), 0.12

(s, 3H, SiCH₃), 1.24 (dd, J ) 14.8 and 9.5 Hz, 1H, CH ₂), 1.56

(dd, J ) 14.8 and 5.6 Hz, 1H, CH₂), 3.50 (ddd, J ) 9.5, 5.6,

and 1.9 Hz, 1H, CH), 7.09-7.15 (m, 2H, Ph), 7.26-7.5 (m, 7H,

Ph), and 9.58 (d, J ) 1.9 Hz, 1H, CHO). 6: ¹H NMR (200

MHz, CDCl₃) δ 0.23 (s, 6H, Si(CH₃)₂), 0.40 (s, 6H, Si(CH₃)₂),

4.46 (s, 2H, CH₂), 6.11 (s, 1H, dCH), and 7.1-7.5 (m, 15H, 3

× Ph).

3-(Meth yld ip h en ylsilyl)-2-p h en ylp r op en a l (8). With

Rh₄(CO)₁₂(0.0053 g, 0.007 09 mmol), MePh₂SiH (0.595 g, 3.00

mmol), and 1a (0.306 g, 3.00 mmol) as starting materials, 8

(0.926 g, 94%, Z:E ) 83:17, bp 195 °C/0.15 Torr) was obtained

analogously to 2a as an orange-yellow viscous oil. (Z)-8: IR

(CCl₄) 2740 (CHO), 1698 (CdO), 1582 (CdC), 1567 (CdC), and

1

1253 (SiCH₃) cm^-1; H NMR (200 MHz, CDCl₃) δ 0.86 (s, 6H,

SiCH₃), 7.32-7.49 (m, 12H, Ph and dCH), 7.54-7.64 (m, 4H,

Ph), and 9.99 (s, 1H, CHO) (additional signals for (E)-8: δ 0.24

(s, 6H, SiCH₃) and 9.77 (s, 1H, CHO)); ¹³C NMR (50 MHz,

CDCl₃) δ -1.61 (SiCH₃), 128.30 (Ph), 128.43 (Ph), 128.80 (Ph),

129.98 (Ph), 134.69 (Ph), 136.01 (Ph, ipso), 137.34 (Ph, ipso),

149.79 (dCH), 155.56 (dC, q), and 192.48 (CHO). Anal. Calcd

for C₂₂H₂₀OSi: C, 80.44; H, 6.14. Found: C, 80.27; H, 6.22.

3-(Tr ieth ylsilyl)-2-p h en ylp r op en a l (9a ). With Rh₄(CO)₁₂

(0.0046 g, 0.006 15 mmol), Et₃SiH (0.349 g, 3.00 mmol), 1a

(0.307 g, 3.01 mmol), and Et₃N (0.315 g, 3.11 mmol) as starting

materials, 9a (0.680 g, 92%, Z:E ) 91:9, bp 125 °C/0.15 Torr)

was obtained analogously to 2a as a pale yellow viscous oil.

(Z)-9a : IR (CCl₄) 2730 (CHO), 1695 (CdO), 1580 (CdC), and,

1563 (CdC) cm^-1; ¹H NMR (200 MHz, CDCl₃) δ 0.80 (m closed

to q, 6H, Si(CH₂CH₃)₃), 1.02 (m closed to t, 9H, Si(CH₂CH₃)₃),

7.14 (s, 1H, dCH), 7.37 (approximately s, 5H, Ph), and 10.03

(s, 1H, CHO) (additional signals for (E)-9a : δ 6.97 (s, 1H,

dCH) and 9.69 (s, 1H, CHO)); ¹³C NMR (50 MHz, CDCl₃) δ

5.05 (SiCH₂), 7.29 (SiCH₂CH₃), 128.26 (Ph), 128.33 (Ph), 128.46

(Ph), 137.68 (Ph, ipso), 152.77 (dCH), 155.64 (dC, q), and

192.81 (CHO). Anal. Calcd for C₁₅H₂₂OSi: C, 73.11; H, 9.00.

Found: C, 72.93; H, 9.04.

3-(Tr im et h oxysilyl)-2-p h en ylp r op en a l (13). With

Rh₄(CO)₁₂(0.0266 g, 0.0356 mmol), (MeO)₃SiH (0.719 g, 5.88

mmol), 1a (0.592 g, 5.79 mmol), and Et₃N (0.395 g, 3.90 mmol)

as starting materials, a mixture of 13 and 15 (0.683 g, 47%,

bp 140 °C/0.3 Torr, (Z)-13:(E)-13:15 ) 5:1:1) was obtained as

a pale yellow oily liquid after immediate distillation of the

mixture. IR (CCl₄): 2695 (CHO), 1703 (CdO), 1605 (CdC),

and 1587 (CdC) cm^-1. (Z)-13: ¹H NMR (200 MHz, CDCl₃) δ

3.38 (s, 9H, Si(OCH₃)₃), 6.62 (s, 1H, dCH), 7.26-7.43 (m, 5H,

Ph), and 9.73 (s, 1H, CHO); ¹³C NMR (50 MHz, CDCl₃) δ 50.16

(OCH₃), 126.45 (Ph), 127.84 (Ph), 129.04 (Ph), 134.57 (Ph,

ipso), 141.75 (dCH), 158.25 (dC, q), and 194.13 (CHO). (E)-

13: ¹H NMR (200 MHz, CDCl₃) δ 3.66 (s, 9H, Si(OCH₃)₃), 6.79

(s, 1H, dCH), 7.26-7.43 (m, 5H, Ph), and 10.22 (s, 1H, CHO).

15: ¹H NMR (200 MHz, CDCl₃) δ 3.36 (s, 3H, SiOCH₃), 3.58

(s, 3H, SiOCH₃), 3.61 (s, 3H, OCH₃), 5.82 (d, J ) 0.8 Hz, 1H,

OCH), 6.29 (d, J ) 0.8 Hz, 1H, dCH), and 7.26-7.43 (m, 5H,

Ph).

3-(Dieth ylm eth ylsilyl)-2-p h en ylp r op en a l (10a ). With

Rh₄(CO)₁₂(0.0059 g, 0.007 89 mmol), Et₂MeSiH (0.409 g, 4.00

mmol), 1a (0.408 g, 3.99 mmol), and Et₃N (0.387 g, 3.82 mmol)

as starting materials, 10a (0.696 g, 75%, Z:E ) 79:21, bp 125

°C/0.15 Torr) was obtained analogously to 2a as a pale yellow

oily liquid. (Z)-10a : IR (CCl₄) 2740 (CHO), 1697 (CdO), 1582

Com p etition betw een Me₂P h SiH a n d ^tBu Me₂SiH in

th e Silylfor m yla tion of 1a . A C₆H₆(10 mL) solution

containing Rh₄(CO)₁₂(0.0022 g, 0.002 94 mmol), Me₂PhSiH

(0.136 g, 1.00 mmol), ^tBuMe₂SiH (0.116 g, 1.00 mmol), and 1a

(0.102 g, 1.00 mmol) prepared in a way similar to procedure 1

was stirred for 5 h at 25 °C under CO pressure (20 kg/cm²).

The residue obtained by evaporation of volatiles from the

reaction mixture was passed through a short pad of silica gel.

The filtrate was concentrated under reduced pressure, and the

residue was distilled to give 0.248 g (quantitative, bp 145 °C/

0.3 Torr) of a mixture of 2a (Z:E ) 85:15) and 11a as a yellow

oily liquid. The ratio of both products (2a :11a ) 88:12) was

(CdC), 1567 (CdC), and 1253 (SiCH₃) cm^-^{1 1}H NMR (200

;

MHz, CDCl₃) δ 0.28 (s, 3H, SiCH₃), 0.78 (m closed to q, 4H,

Si(CH₂)₂), 1.02 (m closed to t, 6H, Si(CH₂CH₃)₂), 7.14 (s, 1H,

dCH), 7.37 (centered m, 5H, Ph), and 10.07 (s, 1H, CHO)

(additional signals for (E)-10a : δ -0.14 (s, 3H, SiCH₃), 0.46

(q, J ) 7.6 Hz, 4H, Si(CH₂CH₃)₂), 0.86 (t, J ) 7.6 Hz, 6H, Si-

(CH₂CH₃)₂), 6.98 (s, 1H, dCH), 7.11-7.18 (m, 2H, Ph), 7.32-

7.40 (m, 3H, Ph), and 9.68 (s, 1H, CHO)); ¹³C NMR (50 MHz,

CDCl₃) δ -3.80 (SiCH₃), 6.76 (SiCH₂), 7.23 (SiCH₂CH₃), 128.23

(Ph), 128.35 (Ph), 128.48 (Ph), 137.67 (Ph, ipso), 153.57 (dCH),

1

determined by the H NMR spectrum of the distilled sample.

3-(Dim eth ylp h en ylsilyl)p r op en a l (2b) (P r oced u r e 2).

A glass tube fitted with a stirring bar was charged with Rh₄-

(CO)₁₂(0.0012 g, 0.016 mmol) and benzene (10 mL) saturated

with CO. The tube was put in a 100 mL stainless steel

autoclave. The reactor was cooled to an external temperature

of -78 °C with an acetone-dry ice bath under an atmosphere

155.14 (dC, q), and 192.70 (CHO). Anal. Calcd for C₁₄H₂₀

-

OSi: C, 72.35; H, 8.67. Found: C, 72.15; H, 8.85.

3-(ter t-Bu tyld im eth ylsilyl)-2-p h en ylp r op en a l (11a ). A

C₆H₆(12 mL) solution containing Rh₄(CO)₁₂(0.0079 g, 0.0106

4340 Organometallics, Vol. 16, No. 20, 1997

Matsuda et al.

of CO. Into this tube were added subsequently Me₂PhSiH

(0.218 g, 1.60 mmol) in C₆H₆(2 mL) and Et₃N (0.190 g, 1.88

mmol) in C₆H₆(2 mL) through a syringe needle at the same

temperature. The reactor was pressurized by acetylene (1b)

to 2.5 kg/cm²and then CO to 20 kg/cm². The contents were

stirred for 2 h at 100 °C and cooled to ambient temperature.

After excess CO was purged under a hood, the reaction mixture

was concentrated under reduced pressure. The residual oily

liquid was chromatographed on silica gel using hexane/AcOEt

(97/3) as an eluent to give 0.017 g (7%) of dimethylphenylvi-

nylsilane and 0.222 g (73%) of (E)-2b as a colorless liquid,

respectively. (E)-2b: bp 126 °C/0.3 Torr; IR (CCl₄) 2700

(m, 2H, Ph), and 9.79 (s, 1H, CHO); ¹³C NMR (50 MHz, CDCl₃)

δ -0.35 (SiCH₃), 13.51 (CH₃), 21.37 (CH₂CH₃), 33.68 (dCCH₂),

128.28 (Ph), 129.66 (Ph), 133.66 (Ph), 138.16 (Ph, ipso), 149.42

(dCH), 157.11 (dC, q), and 193.63 (CHO). Anal. Calcd for

C

₁₄H₂₀OSi: C, 72.36; H, 8.67. Found: C, 72.47; H, 8.96. (E)-

2d : ¹H NMR (500 MHz, CDCl₃) δ 0.51 (s, 6H, Si(CH₃)₂), 0.80

(t, J ) 7.2 Hz, 3H, CH₃), 1.29 (sext, J ) 7.2 Hz, 2H, CH₂CH₂-

CH₃), 2.26 (t, J ) 7.2 Hz, 2H, CH₂CH₂CH₃), 6.78 (s, 1H, dCH),

7.35-7.42 (m, 3H, Ph), 7.50-7.60 (m, 2H, Ph), and 9.43 (s,

1H, CHO); ¹³C NMR (50 MHz, CDCl₃) δ -2.01 (SiCH₃), 13.97

(CH₃), 22.58 (CH₂CH₃), 30.23 (dCCH₂), 128.19 (Ph), 129.58

(Ph), 133.84 (Ph), 137.25 (Ph, ipso), 151.38 (dCH), 158.14 (dC,

q), and 196.10 (CHO).

1

(CHO), 1694 (CdO), 1590 (CdC), and 1253 (SiCH₃) cm^-1; H

NMR (200 MHz, CDCl₃) δ 0.47 (s, 6H, Si(CH₃)₂), 6.55 (dd, J )

18.7 and 7.6 Hz, 1H, dCH), 7.29 (d, J ) 18.7 Hz, 1H, dCH),

7.35-7.45 (m, 3H, Ph), 7.50-7.55 (m, 2H, Ph), and 9.54 (d, J

) 7.6 Hz, 1H, CHO); ¹³C NMR (50 MHz, CDCl₃) δ -3.66

(SiCH₃), 128.24 (Ph), 129.87 (Ph), 133.91 (Ph), 135.83 (Ph,

ipso), 145.24 (dCH), 156.66 (dCH), and 194.83 (CHO). Anal.

Calcd for C₁₁H₁₄OSi: C, 69.42; H, 7.41. Found: C, 69.17; H,

7.26.

3-(Tr ieth ylsilyl)-2-p r op ylp r op en a l (9e). With Rh₄(CO)₁₂

(0.0063 g, 0.008 43 mmol), Et₃SiH (0.576 g, 4.95 mmol), 1e

(0.347 g, 5.09 mmol), and Et₃N (0.474 g, 4.68 mmol) as starting

materials, 9e (0.957 g, 91%, Z:E ) 97:3, bp 136 °C/0.07 Torr)

was obtained analogously to 2a as a pale yellow oil. (Z)-9e:

IR (CCl₄) 2730 (CHO), 1686 (CdO), and 1588 (CdC) cm^-1; ¹H

NMR (200 MHz, CDCl₃) δ 0.65-0.77 (m, 6H, Si(CH₂CH₃)₃),

0.85-1.03 (m, 12H, Si(CH₂CH₃)₃and CH₃), 1.45 (sext, J ) 7.5

Hz, 2H, CH₂CH₂CH₃), 2.28 (dt, J ) 7.3 (t) and 1.1 (d) Hz, 2H,

CH₂CH₂CH₃), 6.74 (t, J ) 1.1 Hz, 1H, dCH), and 9.75 (s, 1H,

CHO); ¹³C NMR (50 MHz, CDCl₃) δ 5.52 (SiCH₂), 7.47

(SiCH₂CH₃), 13.70 (CH₃), 21.82 (CH₂CH₃), 33.96 (dCCH₂),

148.95 (dCH), 157.52 (dC, q), and 193.62 (CHO). Anal. Calcd

for C₁₂H₂₄OSi: C, 67.85; H, 11.39. Found: C, 67.62; H, 11.46.

(E)-9e: ¹H NMR (200 MHz, CDCl₃) δ 0.42-0.63 (m, 6H,

Si(CH₂CH₃)₃, 0.85-1.03 (m, 12H, Si(CH₂CH₃)₃and CH₃), 1.43

(sext, J ) 7.4 Hz, 2H, CH₂CH₃), 2.30 (t, J ) 7.2 Hz, 2H,

dCCH₂), 6.61 (s, 1H, dCH), and 9.41 (s, 1H, CHO); ¹³C NMR

(50 MHz, CDCl₃) δ 4.09 (SiCH₂), 7.40 (SiCH₂CH₃), 14.41 (CH₃),

22.92 (CH₂CH₃), 31.10 (dCCH₂), 150.90 (dCH), 158.17 (dC,

q), and 195.63 (CHO).

3-(ter t-Bu tyldim eth ylsilyl)-2-pr opylpr open al (11e). With

Rh₄(CO)₁₂(0.0060 g, 0.008 02 mmol), ^tBuMe₂SiH (0.568 g, 4.88

mmol), and 1e (0.338 g, 4.96 mmol) in acetonitrile as starting

materials, 11e (0.944 g, 91%, Z:E ) 98:2, bp 116 °C/0.09 Torr)

was obtained as a colorless liquid after reaction for 17 h at 90

°C. (Z)-11e: IR (CCl₄) 2730 (CHO), 1688 (CdO), 1590 (CdC),

and 1253 (SiCH₃) cm^-1; ¹H NMR (200 MHz, CDCl₃) δ 0.22 (s,

6H, Si(CH₃)₂), 0.89 (t, J ) 7.2 Hz, 3H, CH₂CH₃), 0.93 (s, 9H,

^tBu), 1.44 (sext, J ) 7.2 Hz, 2H, CH₂CH₂CH₃), 2.27 (dt, J )

7.2 (t) and 0.9 (d) Hz, 2H, dCCH₂), 6.81 (t, J ) 0.9 Hz, 1H,

dCH), and 9.81 (s, 1H, CHO); ¹³C NMR (50 MHz, CDCl₃) δ

-3.34 (SiCH₃), 13.49 (CH₂CH₃), 16.76 (^tBu, q), 21.54 (CH₂-

CH₃), 26.14 (^tBu), 33.87 dCCH₂), 149.78 (dCH), 157.45 (dC,

q), and 194.11 (CHO). Anal. Calcd for C₁₂H₂₄OSi: C, 67.86;

H, 11.39. Found: C, 67.58; H, 11.63.

3-(Dim eth ylp h en ylsilyl)-2-m eth ylp r op en a l (2c). With

Rh₄(CO)₁₂(0.0040 g, 0.005 35 mmol), Me₂PhSiH (0.367 g, 2.69

mmol), 1c (0.5 mL, ca. 0.35 g, 8.73 mmol), and Et₃N (0.206 g,

2.04 mmol) as starting materials, 2c (0.542 g, 99%, Z:E ) 80:

20, bp 118 °C/0.14 Torr) was obtained analogously to 2b as a

colorless oily liquid. (Z)-2c: IR (CCl₄) 2730 (CHO), 1695

(CdO), 1595 (CdC), and 1253 (SiCH₃) cm^-^{1 1}H NMR (200

;

MHz, CDCl₃) δ 0.50 (s, 6H, Si(CH₃)₂), 1.93 (d, J ) 1.1 Hz, 3H,

CH₃), 6.97 (q, J ) 1.1 Hz, 1H, dCH), 7.35-7.41 (m, 3H, Ph),

7.48-7.58 (m, 2H, Ph), and 9.77 (s, 1H, CHO); ¹³C NMR (50

MHz, CDCl₃) δ -0.41 (SiCH₃), 18.61 (CH₃), 128.30 (Ph), 129.63

(Ph), 133.68 (Ph), 138.02 (Ph, ipso), 150.46 (dCH), 152.85 (dC,

q), and 193.68 (CHO). Anal. Calcd for C₁₂H₁₆OSi: C, 70.53;

H, 7.89. Found: C, 70.32; H, 7.96. (E)-2c: ¹H NMR (200 MHz,

CDCl₃) δ 0.50 (s, 6H, Si(CH₃)₂), 1.81 (d, J ) 0.8 Hz, 3H, CH₃),

6.84 (q, J ) 0.8 Hz, 1H, dCH), 7.35-7.41 (m, 3H, Ph), 7.50-

7.55 (m, 2H, Ph), and 9.46 (s, 1H, CHO); ¹³C NMR (50 MHz,

CDCl₃) δ -2.20 (SiCH₃), 13.38 (CH₃), 128.25 (Ph), 129.68 (Ph),

133.83 (Ph), 137.13 (Ph, ipso), 151.21 (dCH), 153.57 (dCH),

and 196.10 (CHO).

2-Eth yl-3-(d im eth ylp h en ylsilyl)p r op en a l (2d ). With

Rh₄(CO)₁₂(0.0104 g, 0.0139 mmol), Me₂PhSiH (0.680 g, 4.99

mmol), 1d (2 mL, ca. 1.4 g, 25.9 mmol), and Et₃N (0.513 g,

5.06 mmol) as starting materials, 2d (0.989 g, 91%, Z:E ) 94:

6, bp 120 °C/0.07 Torr) was obtained analogously to 2a as a

pale yellow liquid. (Z)-2d : IR (CCl₄) 2720 (CHO), 1688 (CdO),

1593 (CdC), and 1251 (SiCH₃) cm^-^{1 1}H NMR (200 MHz,

;

CDCl₃) δ 0.52 (s, 6H, Si(CH₃)₂), 1.06 (t, J ) 7.5 Hz, 3H, CH₃),

2.34 (q, J ) 7.5 Hz, 2H, CH₂), 6.93 (b s, 1H, dCH), 7.35-7.41

(m, 3H, Ph), 7.48-7.58 (m, 2H, Ph), and 9.81 (s, 1H, CHO);

¹³C NMR (50 MHz, CDCl₃) δ -0.32 (SiCH₃), 12.22 (CH₃), 24.41

(CH₂), 128.31 (Ph), 129.61 (Ph), 133.70 (Ph), 138.18 (Ph, ipso),

147.98 (dCH), 158.65 (dC, q), and 193.63 (CHO). Anal. Calcd

for C₁₃H₁₈OSi: C, 71.50; H, 8.31. Found: C, 71.54; H, 8.38.

(E)-2d : ¹H NMR (200 MHz, CDCl₃) δ 0.51 (s, 6H, Si(CH₃)₂),

0.89 (t, J ) 7.5 Hz, 3H, CH₃), 2.28 (q, J ) 7.5 Hz, 2H, CH₂),

6.76 (s, 1H, dCH), 7.36-7.42 (m, 3H, Ph), 7.51-7.58 (m, 2H,

Ph), and 9.43 (s, 1H, CHO); ¹³C NMR (50 MHz, CDCl₃) δ -1.97

(SiCH₃), 13.51 (CH₃), 21.59 (CH₂), 128.22 (Ph), 129.68 (Ph),

133.85 (Ph), 137.29 (Ph, ipso), 150.92 (dCH), 159.56 (dC, q),

and 195.99 (CHO).

3-(Dim eth ylp h en ylsilyl)-2-p r op ylp r op en a l (2e). With

Rh₄(CO)₁₂(0.0071 g, 0.0095 mmol), Me₂PhSiH (0.694 g, 5.09

mmol), 1e (0.375 g, 5.50 mmol), and Et₃N (0.498 g, 4.92 mmol)

as starting materials, 2e (1.100 g, 93%, Z:E ) 95:5, bp 136

°C/0.07 Torr) was obtained analogously to 2a as a pale yellow

oil. (Z)-2e: IR (CCl₄) 2740 (CHO), 1692 (CdO), 1592 (CdC),

and 1255 (SiCH₃) cm^-1; ¹H NMR (500 MHz, CDCl₃) δ 0.52 (s,

6H, Si(CH₃)₂), 0.92 (t, J ) 7.3 Hz, 3H, CH₃), 1.48 (sext, J )

7.3 Hz, 2H, CH₂CH₂CH₃), 2.30 (t, J ) 7.3 Hz, 2H, CH₂CH₂-

CH₃), 6.94 (s, 1H, dCH), 7.35-7.42 (m, 3H, Ph), 7.50-7.60

2-Bu t yl-3-(d im et h ylp h en ylsilyl)p r op en a l (2f). With

Rh₄(CO)₁₂(0.0114 g, 0.0152 mmol), Me₂PhSiH (1.596 g, 11.71

mmol), and 1f (0.956 g, 11.63 mmol) as starting materials, 2f

(2.465 g, 86%, Z:E ) 85:15, bp 120 °C/0.04 Torr) was obtained

analogously to 2a as a pale yellow oil. (Z)-2f: IR (CCl₄) 2730

1

(CHO), 1688 (CdO), 1590 (CdC), and 1252 (SiCH₃) cm^-1; H

NMR (200 MHz, CDCl₃) δ 0.50 (s, 6H, Si(CH₃)₂), 0.90 (t, J )

7.0 Hz, 3H, CH₃), 1.22-1.44 (m, 4H, CH₂CH₂CH₃), 2.30 (dt, J

) 7.2 (t) and 1.2 (d) Hz, 2H, dCCH₂), 6.93 (t, J ) 1.2 Hz, 1H,

dCH), 7.35-7.40 (m, 3H, Ph), 7.48-7.55 (m, 2H, Ph), and 9.77

(s, 1H, CHO) (additional signals for (E)-2f: δ 0.50 (s, 6H, Si-

(CH₃)₂), 6.75 (s, 1H, dCH), and 9.42 (s, 1H, CHO)); ¹³C NMR

(50 MHz, CDCl₃) δ -0.32 (SiCH₃), 13.70 (CH₃) 22.26 (CH₂),

30.42 (CH₂), 31.39 (CH₂), 128.30 (Ph), 129.60 (Ph), 133.68 (Ph),

137.18 (Ph, ipso), 149.25 (dCH), 157.42 (dC, q), and 193.70

(CHO). Anal. Calcd for

C₁₅H₂₂OSi: C, 73.11; H, 9.00.

Found: C, 72.81; H, 9.19.

2-Bu t yl-3-(d iet h ylm et h ylsilyl)p r op en a l (10f). With

Rh₄(CO)₁₂(0.0050 g, 0.006 69 mmol), Et₂MeSiH (0.502 g, 4.91

mmol), and 1f (0.402 g, 4.89 mmol), 10f (0.839 g, 81%, Z:E )

89:11, bp 100 °C/0.08 Torr) was obtained analogously to 2a as

a colorless liquid. (Z)-10f: IR (CCl₄) 2730 (CHO), 1687 (CdO),

1590 (CdC), and 1255 (SiCH₃) cm^-^{1 1}H NMR (200 MHz,

;

Rh-Catalyzed Silylformylation of Acetylenic Bonds

Organometallics, Vol. 16, No. 20, 1997 4341

CDCl₃) δ 0.19 (s, 3H, SiCH₃), 0.62-0.74 (m, 4H, Si(CH₂CH₃)₂),

0.82-1.00 (m, 9H, Si(CH₂CH₃)₂and CH₃), 1.20-1.45 (m, 4H,

CH₂CH₂CH₃), 2.28 (dt, J ) 7.8 (t) and 1.1 (d) Hz, 2H, dCCH₂),

6.76 (t, J ) 1.1 Hz, 1H, dCH), and 9.78 (s, 1H, CHO); ¹³C

NMR (50 MHz, CDCl₃) δ -3.56 (SiCH₃), 6.95 (SiCH₂), 7.13

(SiCH₂CH₃), 13.69 (CH₃), 22.22 (CH₂CH₃), 30.54 (CH₂), 31.38

(CH₂), 150.25 (dCH), 157.58 (dC, q), and 193.98 (CHO). Anal.

Calcd for C₁₂H₂₄OSi: C, 67.85; H, 11.39. Found: C, 67.73; H,

11.52. (E)-10f: IR (CCl₄) 2685 (CHO), 1685 (CdO), 1590

Si(CH₂CH₃)₃), 0.88 (t, 3H, J ) 6.6 Hz, CH₃), 1.20-1.48 (m,

8H, CH₂CH₂CH₂CH₂CH₃), 2.29 (dt, J ) 7.0 (t) and 1.1 (d) Hz,

2H, dCCH₂), 6.74 (t, J ) 1.1 Hz, 1H, dCH), and 9.75 (s, 1H,

CHO) (additional signals for (E)-9h : δ 6.61 (s, 1H, dCH) and

9.41 (s, 1H, CHO)); ¹³C NMR (50 MHz, CDCl₃) δ 5.21 (SiCH₂),

7.21 (SiCH₂CH₃), 13.84 (CH₃), 22.41 (CH₂CH₃), 28.38 (CH₂),

28.76 (CH₂), 31.47 (CH₂), 31.71 (CH₂), 149.14 (dCH), 158.03

(dC, q), and 194.12 (CHO). Anal. Calcd for C₁₅H₃₀OSi: C,

70.79; H, 11.88. Found: C, 70.62; H, 11.92.

1

(CdC), and 1247 (SiCH₃) cm^-1; H NMR (200 MHz, CDCl₃) δ

2-Cycloh exyl-3-(d im et h ylp h en ylsilyl)p r op en a l (2i).

With Rh₄(CO)₁₂(0.0099 g, 0.0132 mmol), Me₂PhSiH (0.152 g,

1.11 mmol), 1i (0.113 g, 1.04 mmol), and Et₃N (0.116 g, 1.14

mmol) as starting materials, 2i (0.290 g, 96%, Z form only, bp

135 °C/0.05 Torr) was obtained analogously to 2a as a pale

yellow oil. (Z)-2i: IR (CCl₄) 2730 (CHO), 1689 (CdO), 1588

0.18 (s, 3H, SiCH₃), 0.62-0.75 (m, 4H, Si(CH₂CH₃)₂), 0.90 (t,

J ) 6.5 Hz, 3H, CH₃), 0.92-1.02 (m, 6H, Si(CH₂CH₃)₂), 1.25-

1.42 (m, 4H, CH₂CH₂CH₃), 2.29 (t, J ) 7.2 Hz, 2H, dCCH₂),

6.61 (s, 1H, dCH), and 9.40 (s, 1H, CHO); ¹³C NMR (50 MHz,

CDCl₃) δ -5.25 (SiCH₃), 5.60 (SiCH₂), 7.12 (SiCH₂CH₃), 13.69

(CH₃), 22.95 (CH₂CH₃), 28.41 (dCCH₂), 31.73 (dCCH₂CH₂),

151.85 (dCH), 158.25 (dC, q), and 196.17 (CHO).

1

(CdC), and 1255 (SiCH₃) cm^-1; H NMR (200 MHz, CDCl₃) δ

0.51 (s, 6H, Si(CH₃)₂), 1.04-1.50 (m, 5H, cyclohexyl), 1.61-

1.90 (m, 5H, cyclohexyl), 2.54-2.72 (tt, J ) 11.5 and 2.8 Hz,

1H, dCCH), 6.90 (s, 1H, dCH), 7.35-7.45 (m, 3H, Ph), 7.49-

7.61 (m, 2H, Ph), and 9.79 (s, 1H, CHO); ¹³C NMR (50 MHz,

CDCl₃) δ -0.29 (SiCH₃), 25.98 (CH₂), 26.35 (2 × CH₂), 32.30

(2 × CH₂), 37.93 (CH), 128.23 (Ph), 129.50 (Ph), 133.63 (Ph),

138.32 (Ph, ipso), 146.53 (dCH), 162.51 (dC, q), and 193.55

2-Bu tyl-3-(ter t-bu tyld im eth ylsilyl)p r op en a l (11f). With

Rh₄(CO)₁₂(0.0053 g, 0.007 09 mmol), ^tBuMe₂SiH (0.575 g, 4.94

mmol), and 1f (0.481 g, 5.85 mmol) as starting materials, (Z)-

11f (0.792 g, 71%, bp 95 °C/0.3 Torr) was obtained analogously

to 2a as a pale yellow liquid after reaction in acetonitrile for

17 h at 90 °C. (Z)-11f: IR (CCl₄) 2735 (CHO), 1687 (CdO),

1588 (CdC), and 1252 (SiCH₃) cm^-^{1 1}H NMR (200 MHz,

;

(CHO). Anal. Calcd for

C₁₇H₂₄OSi: C, 74.94; H, 8.88.

CDCl₃) δ 0.22 (s, 6H, Si(CH₃)₂), 0.90 (t, J ) 7.3 Hz, 3H,

Found: C, 75.19; H, 9.12.

t

CH₂CH₃), 0.93 (s, 9H, Bu), 1.14-1.48 (m, 4H, CH₂CH₂CH₃),

3-(Dim eth ylp h en ylsilyl)-2-(2-p r op en yl)p r op en a l (2j).

With Rh₄(CO)₁₂(0.0051 g, 0.006 82 mmol), Me₂PhSiH (0.548

g, 4.02 mmol), 1j (0.364 g, 5.51 mmol), and Et₃N (0.418 g, 4.13

mmol) as starting materials, 2j (0.834 g, 90%, Z:E ) 73:27,

bp 124 °C/0.09 Torr) was obtained analogously to 2a as a pale

yellow liquid. (Z)-2j: IR (CCl₄) 2740 (CHO), 2720 (CHO), 1687

2.30 (dt, J ) 7.4 (t) and 1.1 (d) Hz, 2H, dCCH₂), 6.81 (t, J )

1.1 Hz, 1H, dCH), and 9.81 (s, 1H, CHO); ¹³C NMR (50 MHz,

CDCl₃) δ -3.36 (SiCH₃), 13.67 (CH₂CH₃), 16.74 (^tBu, q), 22.20

(CH₂CH₃), 26.12 (^tBu), 30.58 (dCCH₂), 31.55 (dCCH₂CH₂),

149.44 (dCH), 157.74 (dC, q), and 194.03 (CHO). Anal. Calcd

for C₁₃H₂₆OSi: C, 68.96; H, 11.57. Found: C, 68.75; H, 11.80.

3-(Dim eth ylp h en ylsilyl)-2-p en tylp r op en a l (2g). With

Rh₄(CO)₁₂(0.0046 g, 0.006 15 mmol), Me₂PhSiH (0.545 g, 4.00

mmol), and 1g (0.384 g, 3.99 mmol) as starting materials, 2g

(0.737 g, 71%, Z:E ) 87:13, bp 130 °C/0.14 Torr) was obtained

analogously to 2a as a pale yellow oil. (Z)-2g: IR (CCl₄) 2750

(CdO), 1640 (CdC), 1594 (CdC), and 1253 (SiCH₃) cm^-1; H

1

NMR (200 MHz, CDCl₃) δ 0.52 (s, 6H, Si(CH₃)₂), 3.08 (dddd, J

) 6.2, 1.4, 1.4, and 0.9 Hz, 2H, dCCH₂), 5.09 (ddt, J ) 18.2

(d), 1.7 (d), and 1.4 (t) Hz, 1H, dCH₂), 5.12 (ddt, J ) 9.3 (d),

1.7 (d), and 1.4 (t) Hz, 1H, dCH₂), 5.82 (ddt, J ) 18.2 (d), 9.3

(d), and 6.2 (t) Hz, 1H, dCH), 6.98 (t, J ) 0.9 Hz, 1H, dCH),

7.35-7.45 (m, 3H, Ph), 7.49-7.60 (m, 2H, Ph), and 9.81 (s,

1H, CHO); ¹³C NMR (50 MHz, CDCl₃) δ -0.43 (SiCH₃), 35.51

(CH₂), 117.40 (dCH₂), 128.32 (Ph), 129.66 (Ph), 133.68 (Ph),

134.96 (dCH), 137.92 (Ph, ipso), 150.24 (dCH), 154.91 (dC,

q), and 193.02 (CHO). Anal. Calcd for C₁₄H₁₈OSi: C, 72.99;

H, 7.88. Found: C, 73.04; H, 8.00. (E)-2j: IR (CCl₄) 2705

(CHO), 1695 (CdO), 1640 (CdC), 1595 (CdC), and 1255

1

(CHO), 1687 (CdO), 1588 (CdC), and 1252 (SiCH₃) cm^-1; H

NMR (200 MHz, CDCl₃) δ 0.51 (s, 6H, Si(CH₃)₂), 0.88 (t, J )

6.6 Hz, 3H, CH₃), 1.20-1.51 (m, 6H, CH₂CH₂CH₂CH₃), 2.30

(dt, J ) 7.5 (t) and 1.2 (d) Hz, 2H, dCCH₂), 6.93 (t, J ) 1.2

Hz, 1H, dCH), 7.35-7.40 (m, 3H, Ph), 7.48-7.55 (m, 2H, Ph),

and 9.78 (s, 1H, CHO) (additional signals for (E)-2g: δ 0.50

(s, 6H, Si(CH₃)₂), 6.75 (s, 1H, dCH), and 9.42 (s, 1H, CHO));

¹³C NMR (50 MHz, CDCl₃) δ -0.31 (SiCH₃), 13.82 (CH₃), 22.27

(CH₂), 27.93 (CH₂), 31.39 (CH₂), 31.65 (CH₂), 128.30 (Ph),

129.61 (Ph), 133.70 (Ph), 138.20 (Ph, ipso), 149.21 (dCH),

(SiCH₃) cm^-^{1 1}H NMR (200 MHz, CDCl₃) δ 0.51 (s, 6H, Si-

;

(CH₃)₂), 3.02 (ddd, J ) 6.1, 1.7, and 1.7 Hz, 2H, dCCH₂), 4.85,

(ddt, J ) 17.2 (d), 1.7 (t), and 1.7 (t) Hz, 1H, dCH₂), 4.94 (ddt,

J ) 10.4 (d), 1.7 (d), and 1.7 (t) Hz, 1H, dCH₂), 5.70 (ddt, J )

17.2 (d), 10.4 (d), and 6.0 (t) Hz, 1H, dCH), 6.90 (s, 1H, dCH),

7.32-7.45 (m, 3H, Ph), 7.48-7.60 (m, 2H, Ph), and 9.45 (s,

1H, CHO); ¹³C NMR (50 MHz, CDCl₃) δ -2.03 (SiCH₃), 31.93

(CH₂), 116.09 (dCH₂), 128.26 (Ph), 129.77 (Ph), 133.92 (Ph),

134.90 (dCH), 137.02 (Ph, ipso), 152.54 (dCH), 155.08 (dC,

q), and 195.46 (CHO).

157.47 (dC, q), and 193.69 (CHO). Anal. Calcd for C₁₆H₂₄

-

OSi: C, 73.78; H, 9.29. Found: C, 73.84; H, 9.35.

3-(Tr ieth ylsilyl)-2-p en tylp r op en a l (9g). With Rh₄(CO)₁₂

(0.0041 g, 0.005 48 mmol), Et₃SiH (0.465 g, 4.00 mmol), and

1g (0.384 g, 3.99 mmol) as starting materials, 9g (0.790 g, 82%,

Z:E ) 95:5, bp 125 °C/0.15 Torr) was obtained analogously to

2a as a pale yellow liquid. (Z)-9g: IR (CCl₄) 2730 (CHO), 1687

1

(CdO), and 1588 (CdC) cm^-1; H NMR (200 MHz, CDCl₃) δ

3-(Dim eth ylp h en ylsilyl)-2-((tr im eth ylsilyl)m eth yl)p r o-

p en a l (2k ). With Rh₄(CO)₁₂(0.0035 g, 0.004 68 mmol), Me₂-

PhSiH (1.362 g, 10.00 mmol), 1k (1.733 g, 15.45 mmol), and

Et₃N (1.031 g, 10.18 mmol) as starting materials, 2k (2.585 g,

94%, Z:E ) 91:9, bp 140 °C/0.59 Torr) was obtained analo-

gously to 2a (reaction time was increased to 14 h) as a pale

yellow liquid. (Z)-2k : IR (CCl₄) 2740 (CHO), 1685 (CdO), 1578

0.55-0.78 (m, 6H, Si(CH ₂CH₃)₃), 0.83-1.01 (m, 9H, Si-

(CH₂CH₃)₃), 0.96 (t, J ) 7.5 Hz, 3H, CH₃), 1.15-1.47 (m, 6H,

CH₂CH₂CH₂CH₃), 2.29 (dt, J ) 7.5 (t) and 1.1 (d) Hz, 2H,

dCCH₂), 6.74 (t, J ) 1.1 Hz, 1H, dCH), and 9.74 (s, 1H, CHO)

(additional signals for (E)-9g: δ 6.61 (s, 1H, dCH), and 9.41

(s, 1H, CHO)); ¹³C NMR (50 MHz, CDCl₃) δ 5.21 (SiCH₂), 7.21

(SiCH₂CH₃), 13.82 (CH₃), 22.28 (CH₂CH₃), 28.10 (CH₂), 31.33

(CH₂), 31.68 (dCCH₂), 149.14 (dCH), 158.04 (dC, q), and

194.12 (CHO). Anal. Calcd for C₁₄H₂₈OSi: C, 69.93; H, 11.74.

Found: C, 69.78; H, 11.93.

3-(Tr ieth ylsilyl)-2-h exylp r op en a l (9h ). With Rh₄(CO)₁₂

(0.0022 g, 0.002 94 mmol), Et₃SiH (0.465 g, 4.00 mmol), and

1h (0.441 g, 3.99 mmol) as starting materials, 9h (0.871 g,

86%, Z:E ) 96:4, bp 130 °C/0.14 Torr) was obtained analo-

gously to 2a as a pale yellow liquid. (Z)-9h : IR (CCl₄) 2728

(CHO), 1685 (CdO), and 1588 (CdC) cm^-1; ¹H NMR (200 MHz,

CDCl₃) δ 0.65-0.78 (m, 6H, Si(CH₂CH₃)₃), 0.83-1.01 (m, 9H,

(CdC), and 1252 (SiCH₃) cm^-1; H NMR (200 MHz, CDCl₃) δ

1

0.00 (s, 9H, Si(CH₃)₃), 0.51 (s, 6H, Si(CH₃)₂), 1.91 (bs, 2H,

dCCH₂), 6.75 (bs, 1H, dCH), 7.35-7.42 (m, 3H, Ph), 7.52-

7.58 (m, 2H, Ph), and 9.73 (s, 1H, CHO); ¹³C NMR (50 MHz,

CDCl₃) δ -1.94 (SiCH₃), -0.10 (SiCH₃), 22.70 (CH₂), 128.25

(Ph), 129.51 (Ph), 133.63 (Ph), 138.58 (Ph, ipso), 146.32 (dCH),

155.47 (dC, q), and 193.12 (CHO). Anal. Calcd for C₁₅H₂₄

-

OSi₂: C, 65.15; H, 8.75. Found: C, 65.24; H, 8.79. (E)-2k :

¹H NMR (200 MHz, CDCl₃) δ -0.07 (s, 9H, Si(CH₃)₃), 0.50 (s,

6H, Si(CH₃)₂), 1.84 (s, 2H, dCCH₂), 6.57 (s, 1H, dCH), 7.35-

7.42 (m, 3H, Ph), 7.50-7.59 (m, 2H, Ph), and 9.41 (s, 1H,

4342 Organometallics, Vol. 16, No. 20, 1997

Matsuda et al.

CHO); ¹³C NMR (50 MHz, CDCl₃) δ -1.77 (SiCH₃), -1.01

(SiCH₃), 19.15 (CH₂), 128.20 (Ph), 129.61 (Ph), 133.97 (Ph),

137.54 (Ph, ipso), 146.57 (dCH), 156.64 (dC, q), and 196.29

(CHO).

δ 0.51 (s, 6H, Si(CH₃)₂), 3.17 (s, 3H, OCH₃), 4.05 (s, 2H, OCH₂),

7.04 (s, 1H, dCH), 7.35-7.42 (m, 3H, Ph), 7.51-7.57 (m, 2H,

Ph), and 9.48 (s, 1H, CHO); ¹³C NMR (50 MHz, CDCl₃) δ -1.99

(SiCH₃), 58.10 (OCH₃), 66.63 (OCH₂), 128.09 (Ph), 129.46 (Ph),

133.74 (Ph), 137.69 (Ph, ipso), 153.43 (dCH), 155.83 (dC, q),

and 194.65 (CHO).

3-(Dim eth ylph en ylsilyl)-2-(tr im eth ylsilyl)pr open al (2l).

With Rh₄(CO)₁₂(0.0041 g, 0.005 48 mmol), Me₂PhSiH (0.138

g, 1.01 mmol), 1l (0.193 g, 1.96 mmol), and Et₃N (0.115 g, 1.14

mmol) as starting materials, (Z)-2l (0.416 g, 55%, bp 128 °C/

0.8 Torr) was obtained analogously to 2a as a pale yellow liquid

with the concomitant formation of 3-(dimethylphenylsilyl)-

propanal (0.017 g, 17%). (Z)-2l: IR (CCl₄) 2710 (CHO), 1675

2-(3-Ch lor op r op yl)-3-(d im et h ylp h en ylsilyl)p r op en a l

(2o). With Rh₄(CO)₁₂(0.0086 g, 0.0115 mmol), Me₂PhSiH

(0.708 g, 5.20 mmol), 1o (0.532 g, 5.19 mmol), and Et₃N (0.469

g, 4.64 mmol) as starting materials, 2o (1.083 g, 78%, Z:E )

88:12, bp 210 °C/0.2 Torr) was obtained analogously to 2a as

a pale yellow liquid. (Z)-2o: IR (CCl₄) 2700 (CHO), 1692

(CdO), 1590 (CdC), and 1250 (SiCH₃) cm^-^{1 1}H NMR (200

;

MHz, CDCl₃) δ 0.18 (s, 9H, Si(CH₃)₃), 0.53 (s, 6H, Si(CH₃)₂),

7.35-7.42 (m, 3H, Ph), 7.50-7.59 (m, 2H, Ph), 7.57 (s, 1H,

dCH), and 10.02 (s, 1H, CHO); ¹³C NMR (50 MHz, CDCl₃) δ

-1.74 (SiCH₃), -0.39 (SiCH₃), 128.32 (Ph), 129.62 (Ph), 133.70

(Ph), 137.88 (Ph, ipso), 164.89 (dCH), 167.57 (dC, q), and

197.19 (CHO). Anal. Calcd for C₁₄H₂₂OSi₂: C, 64.06; H, 8.45.

Found: C, 63.79; H, 8.67. 3-(Dim eth ylp h en ylsilyl)p r op a -

n a l: IR (CCl₄) 2715 (CHO), 1732 (CdO), and 1255 (SiCH₃)

(CdO), 1597 (CdC), and 1252 (SiCH₃) cm^-^{1 1}H NMR (200

;

MHz, CDCl₃) δ 0.52 (s, 6H, Si(CH₃)₂), 1.85-1.99 (m, 2H, CH₂),

2.47 (dt, J ) 7.6 (t) and 1.1 (d) Hz, 2H, CH₂), 3.52 (t, J ) 6.5

Hz, 2H, CH₂Cl), 7.02 (t, J ) 1.1 Hz, 1H, dCH), 7.34-7.42 (m,

3H, Ph), 7.48-7.56 (m, 2H, Ph), and 9.77 (s, 1H, CHO); ¹³C

NMR (50 MHz, CDCl₃) δ -0.43 (SiCH₃), 29.35 (CH₂), 30.94

(CH₂), 44.19 (CH₂), 128.37 (Ph), 129.73 (Ph), 133.65 (Ph),

137.78 (Ph, ipso), 150.95 (dCH), 155.34 (dC, q), and 193.25

(CHO) (additional signals for (E)-2o: ¹H NMR δ 0.53 (s, 6H,

Si(CH₃)₂), 3.36 (t, J ) 6.5 Hz, 2H, CH₂Cl), 6.86 (t, J ) 1.1 Hz,

1H, dCH), and 9.43 (s, 1H, CHO); ¹³C NMR δ -2.15 (SiCH₃),

26.01 (CH₂), 31.62 (CH₂), 44.62 (CH₂), 128.30 (Ph), 129.73 (Ph),

cm^-^{1 1}H NMR (500 MHz, CDCl₃) δ 0.30 (s, 6H, Si(CH₃)₂),

;

0.99-1.03 (m, 2H, CH₂), 2.36-2.40 (m, 2H, CH₂), 7.35-7.39

(m, 3H, Ph), 7.48-7.51 (m, 2H, Ph), and 9.72 (t, J ) 1.6 Hz,

1H, CHO); ¹³C NMR (125.7 MHz, CDCl₃) δ -3.29 (SiCH₃), 7.40

(CH₂), 38.38 (CH₂), 127.91 (Ph), 129.21 (Ph), 133.51 (Ph),

137.92 (Ph, ipso), and 202.87 (CHO).

133.87 (Ph), and 193.25 (CHO)). Anal. Calcd for C₁₄H₁₉

-

ClOSi: C, 63.02; H, 7.18. Found: C, 63.12; H, 7.32.

2-(H yd r oxym et h yl)-3-(d im et h ylp h en ylsilyl)p r op en a l

(2m ). With Rh₄(CO)₁₂(0.0040 g, 0.005 35 mmol), Me₂PhSiH

(0.685 g, 5.02 mmol), and 1m (0.309 g, 5.51 mmol) as starting

materials, 2m (0.862 g, 78%, Z:E ) 77:23, bp 128 °C/0.8 Torr)

was obtained analogously to 2a as a pale yellow liquid. (Z)-

2m : IR (CCl₄) 3630 (OH), 2730 (CHO), 1680 (CdO), 1600

Com p etition betw een 1a a n d 1f in Silylfor m yla tion .

A C₆H₆(10 mL) solution containing Rh₄(CO)₁₂(0.0022 g,

0.002 94 mmol), Me₂PhSiH (0.136 g, 1.00 mmol), 1a (0.102 g,

0.999 mmol), and 1f (0.082 g, 0.999 mmol) prepared in a way

similar to procedure 1 was stirred for 5 h at 25 °C under CO

pressure (20 kg/cm²). The residue obtained by evaporation of

volatiles from the reaction mixture was passed through a short

pad of silica gel. The filtrate was concentrated under reduced

pressure, and the residue was distilled to give 0.246 g (93%,

bp 145 °C/0.3 Torr) of a mixture of 2a (Z:E ) 95:5) and 2f as

a pale yellow oily liquid. The ratio of both products (2a :2f )

93:7) was determined by the ¹H NMR spectrum of the distilled

sample.

1

(CdC), and 1252 (SiCH₃) cm^-1; H NMR (200 MHz, CDCl₃) δ

0.54 (s, 6H, Si(CH₃)₂), 2.13 (bs, 1H, OH), 4.36 (d, J ) 1.4 Hz,

2H, CH₂OH), 7.20 (t, J ) 1.4 Hz, 1H, dCH), 7.32-7.46 (m,

3H, Ph), 7.48-7.61 (m, 2H, Ph), and 9.80 (s, 1H, CHO); ¹³C

NMR (50 MHz, CDCl₃) δ -0.67 (SiCH₃), 62.56 (OCH₂), 128.39

(Ph), 129.83 (Ph), 133.72 (Ph), 137.42 (Ph, ipso), 149.24 (dCH),

154.42 (dC, q), and 193.61 (CHO). Anal. Calcd for C₁₂H₁₆O₂-

Si: C, 65.41; H, 7.32. Found: C, 65.30; H, 7.35. (E)-2m : ¹H

NMR (200 MHz, CDCl₃) δ 0.53 (s, 6H, Si(CH₃)₂), 2.12 (bs, 1H,

OH), 4.29 (s, 2H, CH₂OH), 6.99 (s, 1H, dCH), 7.35-7.45 (m,

3H, Ph), 7.52-7.58 (m, 2H, Ph), and 9.48 (s, 1H, CHO); ¹³C

NMR (50 MHz, CDCl₃) δ -1.93 (SiCH₃), 59.04 (OCH₂), 128.38

(Ph), 129.88 (Ph), 133.76 (Ph), 136.89 (Ph, ipso), 154.37 (dCH),

155.01 (dC, q), and 196.43 (CHO).

3-(Dim eth ylph en ylsilyl)-2-m eth ylbu t-2-en al (17a). With

Rh₄(CO)₁₂(0.0077 g, 0.0103 mmol), Me₂PhSiH (0.682 g, 5.00

mmol), and 16a (0.415 g, 7.66 mmol) as starting materials,

17a (1.022 g, 94%, Z form only, bp 131 °C/0.2 Torr) was

obtained analogously to 2a as a pale yellow liquid. (Z)-17a :

IR (CCl₄) 2740 (CHO), 1680 (CdO), 1585 (CdC), and 1257

(SiCH₃) cm^-^{1 1}H NMR (200 MHz, CDCl₃) δ 0.52 (s, 6H, Si-

;

Isom er iza tion of (Z)-2 to (E)-2. Isomerization of 2e is

described as a typical example. Into a C₆H₆(10 mL) solution

of 2e (Z:E ) 92:8, 0.118 g, 0.508 mmol) was mixed 0.05 mL of

aqueous HI (57 wt %) at 25 °C. The mixture was stirred for

5 h at 25 °C and then diluted with Et₂O (50 mL). The resulting

solution was subsequently washed with aqueous sodium

thiosulfate (10%, 10 mL), aqueous NaHCO₃(saturated, 10 mL),

and water (15 mL), dried (anhydrous MgSO₄), filtered, and

evaporated. The residual oil was distilled to give isomerized

2e (Z:E ) 9:91, 0.103 g, 87%). Pure (E)-2e was obtained by

TLC separation with hexane/AcOEt (94:6) as eluent.

(CH₃)₂), 1.86 (q, J ) 1.0 Hz, 3H, CH₃), 2.06 (q, J ) 1.0 Hz, 3H,

CH₃), 7.32-7.40 (m, 3H, Ph), 7.43-7.55 (m, 2H, Ph), and 9.80

(s, 1H, CHO); ¹³C NMR (50 MHz, CDCl₃) δ -0.20 (SiCH₃),

11.24 (CH₃), 21.04 (CH₃), 128.27 (Ph), 129.48 (Ph), 133.55 (Ph),

138.38 (Ph, ipso), 148.24 (dC, q), 161.15 (dC, q), and 193.51

(CHO). Anal. Calcd for

C₁₃H₁₈OSi: C, 71.50; H, 8.31.

Found: C, 71.51; H, 8.54.

3-(Dim eth ylp h en ylsilyl)-2-p r op ylbu t-2-en a l (17b) a n d

3-(Dim eth ylp h en ylsilyl)-2-m eth ylh ex-2-en a l (18b). With

Rh₄(CO)₁₂(0.0114 g, 0.0152 mmol), Me₂PhSiH (0.543 g, 3.99

mmol), 16b (0.380 g, 4.63 mmol), and Et₃N (0.417 g, 4.12

mmol) as starting materials, a mixture of 17a and 18b (0.832

g, 85%, 17b:18b ) 70:30, bp 123 °C/0.07 Torr) was obtained

analogously to 2a as a colorless liquid. The following data

were obtained from a mixture of both isomers. IR (CCl₄): 2730

3-(Dim eth ylp h en ylsilyl)-2-(m eth oxym eth yl)p r op en a l

(2n ). With Rh₄(CO)₁₂(0.0125 g, 0.0167 mmol), Me₂PhSiH

(0.682 g, 5.01 mmol), 1n (0.353 g, 5.04 mmol), and Et₃N (0.506

g, 5.00 mmol) as starting materials, 2n (0.377 g, 32%, Z:E )

88:12, bp 125 °C/0.2 Torr) was obtained analogously to 2a as

a pale yellow liquid. (Z)-2n : IR (CCl₄) 2720 (CHO), 1686

(CHO), 1677 (CdO), 1578 (CdC), and 1250 (SiCH₃) cm^-1

.

17b: ¹H NMR (200 MHz, CDCl₃) δ 0.53 (s, 6H, Si(CH₃)₂), 0.93

(t, J ) 7.5 Hz, 3H, CH₃), 1.38 (sext, J ) 7.5 Hz, 2H, CH₂CH₂-

CH₃), 2.10 (s, 3H, CH₃), 2.39 (t, J ) 7.5 Hz, 2H, CH₂CH₂CH₃),

7.31-7.42 (m, 3H, Ph), 7.44-7.55 (m, 2H, Ph), and 9.79 (s,

1H, CHO) (additional signals for 18b: δ 0.53 (s, 6H, Si(CH₃)₂),

0.96 (t, J ) 7.5 Hz, 3H, CH₃), 1.40 (sext, J ) 7.5 Hz, 2H,

CH₂CH₂CH₃), 1.88 (s, 3H, CH₃), 2.46 (t, J ) 7.5 Hz, 2H, CH₂-

CH₂CH₃), 7.31-7.42 (m, 3H, Ph), 7.44-7.55 (m, 2H, Ph), and

9.82 (s, 1H, CHO)); ¹³C NMR (50 MHz, CDCl₃) δ -0.09 (SiCH₃),

13.96 (CH₂CH₃), 20.75 (dCCH₃), 21.68 (CH₂CH₃), 27.51

(CdO), 1601 (CdC), and 1251 (SiCH₃) cm^-^{1 1}H NMR (200

;

MHz, CDCl₃) δ 0.54 (s, 6H, Si(CH₃)₂), 3.41 (s, 3H, OCH₃), 4.15

(d, J ) 1.7 Hz, 2H, OCH₂), 7.23 (t, J ) 1.7 Hz, 1H, dCH),

7.35-7.42 (m, 3H, Ph), 7.51-7.57 (m, 2H, Ph), and 9.79 (s,

1H, CHO); ¹³C NMR (50 MHz, CDCl₃) δ -0.61 (SiCH₃), 58.69

(OCH₃), 70.25 (OCH₂), 128.34 (Ph), 129.73 (Ph), 133.74 (Ph),

137.69 (Ph, ipso), 148.82 (dCH), 152.30 (dC, q), and 192.70

(CHO). Anal. Calcd for

C₁₃H₁₈O₂Si: C, 66.62; H, 7.74.

Found: C, 66.50; H, 7.73. (E)-2n : ¹H NMR (200 MHz, CDCl₃)

Rh-Catalyzed Silylformylation of Acetylenic Bonds

Organometallics, Vol. 16, No. 20, 1997 4343

(dCCH₂), 128.28 (Ph), 129.46 (Ph), 133.49 (Ph), 138.54 (Ph,

ipso), 152.67 (dC, q), 160.87 (dC, q), and 193.59 (CHO)

(additional signals for 18b: δ 0.13 (SiCH₃), 10.97 (CH₂CH₃),

14.21 (dCCH₃), 21.91 (CH₂CH₃), 36.28 (dCCH₂), 128.24 (Ph),

129.35 (Ph), 133.60 (Ph), 138.93 (Ph, ipso), 147.66 (dC, q),

NMR (200 MHz, CDCl₃) δ 0.62 (s, 6H, Si(CH₃)₂), 0.95 (t, J )

7.2 Hz, 3H, CH₂CH₃), 3.92 (q, J ) 7.2 Hz, 2H, CH₂CH₃), 7.18-

7.25 (m, 3H, Ph), 7.30-7.43 (m, 5H, Ph), 7.60-7.70 (m, 2H,

Ph), and 9.92 (s, 1H, CHO); ¹³C NMR (50 MHz, CDCl₃) δ -1.25

(SiCH₃), 13.63 (CH₂CH₃), 60.77 (OCH₂), 128.13 (Ph), 128.35

(Ph), 128.59 (Ph), 128.83 (Ph), 130.01 (Ph), 133.88 (Ph), 134.69

(Ph, ipso), 136.67 (Ph, ipso), 150.02 (dC, q), 155.39 (dC, q),

170.51 (CO₂CH₂), and 192.17 (CHO). 3-(Eth oxyca r bon yl)-

2-p h en ylp r op -2-en a l: yellow oil, bp 145 °C/0.27 Torr; ¹H

NMR (200 MHz, CDCl₃) δ 1.12 (t, J ) 7.1 Hz, 3H, CH₂CH₃),

4.13 (q, J ) 7.1 Hz, 2H, CH₂CH₃), 6.71 (s, 1H, dCH), 7.19-

7.30 (m, 2H, Ph), 7.35-7.43 (m, 3H, Ph), and 9.76 (s, 1H,

CHO); ¹³C NMR (50 MHz, CDCl₃) δ 13.54 (CH₂CH₃), 61.17

(OCH₂), 128.07 (Ph), 129.01 (Ph), 129.15 (Ph), 131.33 (Ph,

ipso), 136.28 (dCH), 149.62 (dC, q), 165.27 (CO₂CH₂), and

193.11 (CHO). Anal. Calcd for C₁₂H₁₂O₃: C, 70.57; H, 5.92.

Found: C, 70.85; H, 6.22.

164.83 (dC, q), and 194.08 (CHO)). Anal. Calcd for C₁₅H₂₂

-

OSi: C, 73.11; H, 9.00. Found: C, 73.21; H, 9.30.

3-(Dim eth ylp h en ylsilyl)-2-p h en ylbu t-2-en a l (17c) a n d

3-(Dim e t h ylp h e n ylsilyl)-2-m e t h yl-2-p h e n ylh e x-2-e n a l

(18c). With Rh₄(CO)₁₂(0.0068 g, 0.009 09 mmol), Me₂PhSiH

(0.553 g, 4.06 mmol), 16c (0.461 g, 3.97 mmol), and Et₃N (0.425

g, 4.19 mmol) as starting materials, a mixture of 17c and 18c

(0.908 g, 82%, 17c:18c ) 90:10, bp 160 °C/0.12 Torr) was

obtained analogously to 2a as a pale yellow oil. 17c: IR (CCl₄)

2735 (CHO), 1682 (CdO), 1560 (CdC), and 1255 (SiCH₃) cm^-1

;

¹H NMR (200 MHz, CDCl₃) δ 0.61 (s, 6H, Si(CH₃)₂), 1.97 (s,

3H, CH₃), 7.05-7.09 (m, 3H, Ph), 7.26-7.41 (m, 5H, Ph), 7.43-

7.56 (m, 2H, Ph), and 9.97 (s, 1H, CHO); ¹³C NMR (50 MHz,

CDCl₃) δ -0.40 (SiCH₃), 22.92 (dCCH₃), 127.66 (Ph), 128.36

(Ph), 129.46 (Ph), 129.68 (Ph), 133.61 (Ph), 135.96 (Ph, ipso),

138.09 (Ph, ipso), 152.90 (dC, q), 163.02 (dC, q), and 192.57

Rh ₄(CO)₁₂-Ca ta lyzed Cycloca r bon yla tion of 1a in th e

P r esen ce of ^tBu Me₂SiH. A C₆H₆(12 mL) solution of

Rh₄(CO)₁₂(0.0071 g, 0.009 44 mmol), ^tBuMe₂SiH (0.418 g, 3.60

mmol), and 1a (0.804 g, 7.87 mmol) prepared in a way similar

to procedure 1 was stirred for 41 h at 80 °C under CO pressure

(10 kg/cm²). Oily materials left after evaporation of volatiles

from the reaction mixture were separated by medium-pressure

liquid chromatography on silica gel using hexane/AcOEt (95/

5) as an eluent to give 19 (0.479 g, 38%) and 20 (0.082 g, 6%)

as well as 11a (0.371 g, 42%). 19: yellow viscous oil, bp 190

°C/0.3 Torr (solidifies on storage); IR (CCl₄) 1693 (CdO), 1600

(CdC), 1253 (SiCH₃) cm^-1; ¹H NMR (500 MHz, CDCl₃) δ 0.13

(CHO). Anal. Calcd for

C₁₈H₂₀OSi: C, 77.09; H, 7.19.

Found: C, 76.93; H, 7.25. 18c: IR (CCl₄) 2740 (CHO), 1683

1

(CdO), 1600 (CdC), 1578 (CdC), and 1255 (SiCH₃) cm^-1; H

NMR (200 MHz, CDCl₃) δ 0.32 (s, 6H, Si(CH₃)₂), 1.63 (s, 3H,

CH₃), 6.79-7.00 (m, 3H, Ph), 7.13-7.63 (m, 7H, Ph), and 9.99

(s, 1H, CHO); ¹³C NMR (50 MHz, CDCl₃) δ 0.04 (SiCH₃), 13.35

(dCCH₃), 125.68 (Ph), 126.42 (Ph), 128.42 (Ph), 128.63 (Ph),

129.62 (Ph), 133.66 (Ph), 138.48 (Ph, ipso), 143.18 (Ph, ipso),

148.23 (dC, q), 165.04 (dC, q), and 194.35 (CHO).

t

(s, 3H, SiCH₃), 0.15 (s, 3H, SiCH₃), 0.94 (s, 9H, Bu), 2.57 (d,

J ) 1.1 Hz, 1H, CHSi), 4.14 (dd, J ) 3.2 and 1.1 Hz, 1H,

CHPh), 7.17-7.42 (m, 8H, Ph), 7.64 (d, J ) 3.2 Hz, 1H, dCH),

7.73-7.76 (m, 2H, Ph); ¹³C NMR (50 MHz, CDCl₃) δ -6.81

(SiCH₃), -6.75 (SiCH₃), 17.86 (^tBu, q), 26.87 (^tBu), 47.96

(CHPh), 50.83 (CHSi), 127.20 (Ph), 127.46 (Ph), 128.55 (Ph),

129.10 (Ph), 131.74 (Ph, ipso), 142.04 (Ph, ipso or dC, q),

142.85 (dC, q or Ph, ipso), 158.53 (dCH), 208.84 (CdO). Anal.

Calcd for C₂₃H₂₈OSi: C, 79.26; H, 8.10. Found: C,79.35; H,

8.09. 20: brownish yellow viscous oil, bp 190 °C/0.3 Torr; IR

(CCl₄) 1703 (CdO), 1605 (CdC), 1573 (CdC), 1248 (SiCH₃)

cm^-1; ¹H NMR (500 MHz, CDCl₃) δ -0.17 (s, 3H, SiCH₃), -0.12

3-(Dim eth ylph en ylsilyl)-2,3-d ip h en ylp r op -2-en a l (17d ).

With Rh₄(CO)₁₂(0.0090 g, 0.0120 mmol), Me₂PhSiH (0.768 g,

5.64 mmol), 16d (1.004 g, 5.63 mmol), and Et₃N (0.590 g, 5.82

mmol) as starting materials, 17d (1.734 g, 90%, Z:E ) 95:5,

bp 210 °C/0.05 Torr) was obtained analogously to 2a as a pale

yellow oil. 17d : IR (CCl₄) 2730 (CHO), 1687 (CdO), 1595

1

(CdC), and 1253 (SiCH₃) cm^-1; H NMR (200 MHz, CDCl₃) δ

0.41 (s, 6H, Si(CH₃)₂), 6.74-6.91 (m, 4H, Ph), 6.98-7.15 (m,

6H, Ph), 7.35-7.45 (m, 3H, Ph), 7.58-7.67 (m, 2H, Ph), and

10.15 (s, 1H, CHO) (additional signals for (E)-17d : δ -0.03

(s, 6H, Si(CH₃)₂) and 9.57 (s, 1H, CHO)); ¹³C NMR (50 MHz,

CDCl₃) δ 0.15 (SiCH₃), 126.19 (Ph), 126.88 (Ph), 127.18 (Ph),

127.59 (Ph), 127.92 (Ph), 128.48 (Ph), 129.70 (Ph), 129.99 (Ph),

133.69 (Ph), 135.31 (Ph, ipso), 138.30 (Ph, ipso), 142.38 (Ph,

ipso), 151.86 (dC, q), 166.01 (dC, q), and 193.13 (CHO). Anal.

Calcd for C₂₃H₂₂OSi: C, 80.65; H, 6.48. Found: C, 80.41; H,

6.62.

3-(Meth oxyca r bon yl)-3-(d im eth ylp h en ylsilyl)-2-m eth -

ylp r op -2-en a l (18e). With Rh₄(CO)₁₂(0.0028 g, 0.0037 mmol),

Me₂PhSiH (0.283 g, 2.08 mmol), 16e (0.194 g, 1.98 mmol), and

Et₃N (0.199 g, 1.97 mmol) as starting materials, 18e (0.345 g,

67%, bp 126 °C/0.27 Torr) was obtained analogously to 2a as

a pale yellow oil accompanied by 0.028 g (6%) of hydrosilylation

product. 18e: IR (CCl₄) 2730 (CHO), 1724 (CdO), 1693 (CdO),

1655 (CdC), 1588 (CdC), and 1252 (SiCH₃) cm^-1; ¹H NMR (200

MHz, CDCl₃) δ 0.54 (s, 6H, Si(CH₃)₂), 1.84 (s, 3H, CH₃), 3.73

(s, 3H, OCH₃), 7.35-7.41 (m, 3H, Ph), 7.52-7.58 (m, 2H, Ph),

and 9.75 (s, 1H, CHO); ¹³C NMR (50 MHz, CDCl₃) δ -1.10

(SiCH₃), 13.82 (dCCH₃), 51.65 (OCH₃), 128.37 (Ph), 130.03

(Ph), 133.72 (Ph), 136.60 (Ph, ipso), 147.64 (dC, q), 154.08 (dC,

q), 171.55 (CO₂CH₃), and 192.81 (CHO). Anal. Calcd for

t

(s, 3H, SiCH₃), 0.90 (s, 9H, Bu), 3.05 (dd, J ) 19.1 and 3.1

Hz, 1H, CH₂), 3.42 (dd, J ) 19.1 and 7.5 Hz, 1H, CH₂), 3.70

(dd, J ) 7.5 and 3.1 Hz, 1H, CHPh), 7.18-7.43 (m, 10H, Ph);

¹³C NMR (50 MHz, CDCl₃) δ -4.78 (SiCH₃), -4.73 (SiCH₃),

17.38 (^tBu, q), 27.35 (^tBu), 45.97 (CH₂), 52.67 (CHPh), 126.60

(Ph), 126.90 (Ph), 127.55 (Ph), 128.21 (Ph), 128.81 (Ph), 128.95

(Ph), 139.69, 139.76, 140.21 (Ph ipso, Ph ipso, and dCSi),

186.07 (dCPh), 212.64 (CdO). Anal. Calcd for C₂₃H₂₈OSi: C,

79.26; H, 8.10. Found: C, 79.18; H, 8.19.

P r otod esilyla tion of 19. To a methanol (10 mL) solution

of 19 (0.058 g, 0.165 mmol) were added KF (0.096 g, 1.65 mmol)

and water (0.1 mL). The mixture was stirred for 36 h at 25

°C. The residue resulting from the evaporation of methanol

was diluted with 70 mL of AcOEt. The solution was washed

with 10 mL of water and dried over MgSO₄. Volatiles were

evaporated under reduced pressure, and the residue was

purified by column chromatography on silica gel to give 21

(0.0261 g, 68%).

Au th en tic P r ep a r a tion of 21. 1-(Dimethylphenylsilyl)-

2,5-diphenylpenta-1,4-dien-3-one (0.957 g, 49%) was obtained

as a pale yellow oily liquid by the following three steps:

addition of (2-phenylethenyl)magnesium bromide (4.2 mmol)

to 2a (0.787 g, 2.95 mmol) in THF (25 mL) to give 1-(dimeth-

ylphenylsilyl)-2,5-diphenylpenta-1,4-dien-3-ol, subsequent PDC

oxidation of this crude alcohol in DMF (15 mL), and column

chromatography on silica gel. Into a 50 mL flask containing

this divinyl ketone (0.957 g, 2.59 mmol) was added FeCl₃(0.442

g, 2.72 mmol). The resulting solution was stirred for 20 h at

25 °C and worked up according to the literature⁵⁸to give 21

(0.126 g, 22%) as a pale yellow oily liquid. 21: bp 160 °C/0.14

C

₁₄H₁₈O₃Si: C, 64.09; H, 6.91. Found: C, 64.22; H, 7.15.

3-(Eth oxyca r bon yl)-3-(d im eth ylp h en ylsilyl)-2-p h en yl-

p r op -2-en a l (18f). With Rh₄(CO)₁₂(0.0050 g, 0.006 69 mmol),

Me₂PhSiH (0.425 g, 3.12 mmol), 16f (0.530 g, 3.04 mmol), and

Et₃N (0.313 g, 3.08 mmol) as starting materials, a mixture of

18f (0.463 g, 45%) and the hydrosilylation product ethyl

2-(dimethylphenylsilyl)-3-phenylpropenoate (0.404 g, 43%)

were obtained analogously to 2a as a pale yellow oil. 18f

(slightly contaminated by its protodesilylation product): pale

yellow oil, bp 180 °C/0.2 Torr; IR (CCl₄) 2720 (CHO), 1707

1

(CdO), 1695 (CdO), 1620 (CdC), and 1253 (SiCH₃) cm^-1; H

Torr; IR (CCl₄) 1715 (CdO) and 1605 (CdC) cm^-1; H NMR

4344 Organometallics, Vol. 16, No. 20, 1997

Matsuda et al.

(500 MHz, CDCl₃) 2.58 (dd, J ) 19.0 and 2.9 Hz, 1H, CH₂),

3.18 (dd, J ) 19.0 and 6.8 Hz, 1H, CH₂), 4.18 (ddd, J ) 6.8,

2.9, and 2.4 Hz, 1H, CHPh), 7.21-7.43 (m, 8H, Ph) 7.75-7.78

(m, 2H, Ph), and 7.80 (d, J ) 2.4 Hz, 1H, dCH); ¹³C NMR (50

MHz, CDCl₃) δ 43.67 (CH), 45.59 (CH₂), 127.39 (Ph), 128.66

(Ph), 128.85 (Ph), 129.17 (Ph), 131.28 (Ph ipso), 142.08 (Ph,

ipso), 143.05 (dCPh), 160.82 (dCH), 207.54 (CdO).

(^tBu), 30.12 (CH₂), 33.72 (CH₂), 38.46 (SiCCH₂), 43.50 (ring

CH₂), 144.02 (dCCH₂), 166.57 (dCH), 210.48 (CdO). Anal.

Calcd for C₁₉H₃₆OSi: C, 73.95; H, 11.76. Found: C, 73.83; H,

11.95. 24 (tentatively assigned): pale yellow oil, bp 160 °C/

0.2 Torr; IR (CCl₄) 1693 (CdO), 1595 (CdC), and 1253 (SiCH₃)

1

cm^-1; H NMR (500 MHz, CDCl₃) δ 0.05 (s, 3H, SiCH₃), 0.08

(s, 3H, SiCH₃), 0.88 (t, J ) 6.5 Hz, 3H, CH₃), 0.88 (s, 9H, ^tBu),

0.94 (t, J ) 7.3 Hz, 3H, CH₃), 1.22-1.34 (m, 4H, 2 × CH₂),

1.34-1.44 (m, 2H, CH₂), 1.46-1.64 (m, 4H, 2 × CH₂), 2.04

(dd, J ) 1.3 and 1.1 Hz, 1H, ring CHSi), 2.23-2.30 (m, 1H,

ring CHCH₂), 2.50 (t, J ) 6.1 Hz, 2H, CH₂), 5.82 (dt, J ) 1.3

and 1.3 Hz, 1H, dCH); ¹³C NMR (125.7 MHz, CDCl₃) δ -5.72

(SiCH₃), -4.57 (SiCH₃), 13.76 (CH₃), 13.85 (CH₃), 18.32 (^tBu,

q), 22.42 (CH₂), 22.85 (CH₂), 27.02 (^tBu), 28.39 (CH₂), 29.77

(CH₂), 34.01 (CH₂), 34.66 (CH₂), 42.94 (ring CH), 51.31 (ring

CH), 126.21 (dCH), 188.08 (dC, q), 212.73 (CdO). 25: pale

yellow oil, 160 °C/0.2 Torr; IR (CCl₄) 1695 (CdO), 1653 (CdC),

Rh ₄(CO)₁₂-Ca ta lyzed Cycloca r bon yla tion of 1f in th e

P r esen ce of Et₂MeSiH. A C₆H₆(12 mL) solution of Rh₄(CO)₁₂

(0.0052 g, 0.006 95 mmol), Et₂MeSiH (0.339 g, 3.31 mmol), and

1f (0.804 g, 9.78 mmol) prepared in a way similar to procedure

1 was stirred for 21 h at 85 °C under CO pressure (4 kg/cm²).

Oily materials left after evaporation of volatiles from the

reaction mixture were directly distilled to remove 10f (120 °C/

0.1 Torr, 0.340 g, 48%). Then, the residue was purified by

medium-pressure liquid chromatography on silica gel using

hexane/AcOEt (96/4) as an eluent to give 22a (0.131 g, 13%)

after bulb-to-bulb distillation as a pale yellow oily liquid: bp

140 °C/0.1 Torr; IR (CCl₄) 1692 (CdO), 1587 (CdC), 1245 (Si-

1570 (CdC), and 1248 (SiCH₃) cm^-^{1 1}H NMR (500 MHz,

;

CDCl₃) δ 0.26 (s, 6H, SiCH₃), 0.88 (s, 9H, ^tBu), 0.94 (t, J ) 7.0

Hz, 3H, CH₃), 0.96 (t, J ) 7.0 Hz, 3H, CH₃), 1.40 (sext, J )

7.0 Hz, 2H, CH₂CH₃), 1.50 (sext, J ) 7.5 Hz, 2H, CH₂), 1.52

(quint, J ) 7.5 Hz, 2H, CH₂), 2.16 (dt, J ) 7.5 and 7.5 Hz, 2H,

dCHCH₂), 2.55 (dd, J ) 7.5 and 7.5 Hz, 2H, CH₂), 3.13 (bs,

2H, ring CH₂), 6.45 (tt, J ) 7.5 and 1.9 Hz, 1H, dCH); ¹³C

NMR (125.7 MHz, CDCl₃) δ -4.08 (SiCH₃), 13.88 (2 × CH₃),

17.58 (^tBu, q), 21.81 (CH₂), 23.06 (CH₂), 26.77 (^tBu), 30.53

(CH₂), 31.84 (CH₂), 34.24 (CH₂), 35.94 (ring CH₂), 132.77

(dCH), 135.76 (ring CdCH), 139.65 (dCSi), 184.08 (ring

dCCH₂), 201.14 (CdO). Anal. Calcd for C₁₉H₃₄OSi: C, 74.44;

H, 11.18. Found: C, 74.22; H, 11.41. 26 (Z:E ) 64:36): pale

yellow oil, bp 165 °C/0.2 Torr; IR (CCl₄) 1663 (CdO), 1617

(CdC), and 1248 (SiCH₃) cm^-1. (Z)-26: ¹H NMR (500 MHz,

C) cm^-^{1 1}H NMR (500 MHz, CDCl₃) δ 0.18 (s, 3H, SiCH₃),

;

0.72 (m, 4H, Si(CH₂CH₃)₂), 0.88 (t, J ) 7.8 Hz, 9H, Si-

(CH₂CH₃)₂and CH₂CH₃), 0.94 (t, J ) 7.3 Hz, 3H, CH₂CH₃),

1.22-1.33 (m, 5H, 2 × CH₂and CHCH₂), 1.38 (sext, J ) 7.3

Hz, 2H, CH₂), 1.50 (quint, J ) 7.8 Hz, 2H, CH₂), 1.72-1.79

(m, 1H, CHCH₂), 2.25 (dd, J ) 18.6 and 2.9 Hz, 2H, ring CH₂),

2.25-2.31 (m, 1H, ring CH), 2.48 (t, J ) 8.0 Hz, 2H, CH₂),

2.75 (dd, J ) 18.6 and 7.3 Hz, 1H, ring CH₂); ¹³C NMR (125.7

MHz, CDCl₃) δ -5.11 (SiCH₃), -5.09 (SiCH₃), 5.54 (SiCH₂),

5.58 (SiCH₂), 7.43 (SiCH₂CH₃), 13.95 (CH₃), 13.97 (CH₃), 22.70

(CH₂CH₂CH₃), 22.97 (CH₂CH₂CH₃), 29.58 (CH₂), 30.83 (CH₂),

31.35 (CH₂), 33.91 (CH₂), 39.63 (ring CH₂), 46.52 (ring CH),

136.92 (dCSi), 189.04 (dCCH₂), 216.42 (CdO). Anal. Calcd

for C₁₈H₃₄OSi: C, 73.39; H, 11.64. Found: C,73.20; H, 11.64.

t

CDCl₃) δ -0.04 (s, 6H, Si(CH₃)₂), 0.88 (s, 9H, Bu), 0.90 (t, J

) 7.1 Hz, 3H, CH₃), 0.92 (t, J ) 7.2 Hz, 3H, CH₃), 1.28-1.49

(m, 8H, 4 × CH₂), 2.25 (dt, J ) 6.8 and 6.8 Hz, 2H, CH₂), 2.29

(t, J ) 7.3 Hz, 2H, CH₂), 5.67 (t, J ) 1.2 Hz, dCH), 6.16 (dt,

J ) 15.8 (d) and 1.1 (t) Hz, 1H, dCH), 6.81 (dt, J ) 15.8 (d)

and 6.8 (t) Hz, 1H, dCH); ¹³C NMR (125.7 MHz, CDCl₃) δ

-5.27 (SiCH₃), 13.72 (CH₃), 13.79 (CH₃), 16.65 (^tBu, q), 22.18

(CH₂), 22.98 (CH₂), 26.42 (^tBu), 30.05 (CH₂), 31.68 (CH₂), 32.26

(CH₂), 38.17 (CH₂), 127.14 (dCH), 130.43 (dCH), 151.26

(dCHSi), 158.50 (dC, q), 200.63 (CdO); EI MS m/z 251 (M⁺

- 57). (E)-26: ¹H NMR (500 MHz, CDCl₃) δ 0.16 (s, 6H, Si-

Rh ₄(CO)₁₂-Ca ta lyzed Cycloca r bon yla tion of 1f in th e

P r esen ce of ^tBu Me₂SiH. A C₆H₆(12 mL) solution of

t

Rh₄(CO)₁₂(0.0078 g, 0.0104 mmol), BuMe₂SiH (0.528 g, 4.54

mmol), and 1f (0.752 g, 9.15 mmol) prepared in a way similar

to procedure 1 was stirred for 165 h at 100 °C under CO

pressure (20 kg/cm²). Oily materials obtained by evaporation

of volatiles from the reaction mixture were directly distilled

to remove 11f (120 °C/0.1 Torr, 0.232 g, 23%). Then, the

residue was separated by medium-pressure liquid chromatog-

raphy on silica gel and subsequent preparative TLC using

hexane/AcOEt (93/7) as an eluent to give 22b (0.169 g, 12%),

23 (0.042 g, 3%), 24 (0.019 g, 1%), 25 (0.041 g, 3%), 26 (0.015

g, 1%), and 11f (0.189 g, 18%) in addition to some inseparable

products. 22b: bp 160 °C/0.2 Torr, pale yellow oil; IR (CCl₄)

t

(CH₃)₂), 0.90 (t, J ) 6.8 Hz, 3H, CH₃), 0.92 (s, 9H, Bu), 0.92

(t, J ) 6.8 Hz, 3H, CH₃), 1.28-1.29 (m, 8H, 4 × CH₂), 2.25

(dt, J ) 6.8 and 6.8 Hz, 2H, CH₂), 2.42 (t, J ) 7.3 Hz, 2H,

CH₂), 6.33 (s, 1H, dCH), 6.51 (dt, J ) 15.6 (d) and 1.0 (t) Hz,

1H, dCH), 6.82 (dt, J ) 15.6 (d) and 6.8 (t) Hz, 1H, dCH); ¹³

C

1

1690 (CdO), 1580 (CdC), 1247 (SiCH₃) cm^-1; H NMR (500

NMR (125.7 MHz, CDCl₃) δ -4.57 (SiCH₃), 13.76 (CH₃), 13.88

(CH₃), 16.88 (^tBu, q), 22.22 (CH₂), 22.98 (CH₂), 26.37 (^tBu),

30.27 (CH₂), 31.68 (CH₂), 31.72 (dCCH₂), 32.34 (dCCH₂),

126.99 (dCH), 135.00 (dCHCH₂), 148.93 (dCHSi), 158.50

(dC, q), and 194.68 (CdO); EI MS m/z 251 (M⁺- 57).

MHz, CDCl₃) δ 0.21 (s, 3H, SiCH₃), 0.23 (s, 3H, SiCH₃), 0.86

t

(s, 9H, Bu), 0.89 (t, J ) 7.1 Hz, 3H, CH₃), 0.95 (t, J ) 7. 3

Hz, 3H, CH₃), 1.22-1.34 (m, 5H, 2 × CH₂and CHCH₂), 1.38

(sext, 2H, CH₂), 1.47-1.55 (m, 2H, CH₂), 1.73-1.81 (m, 1H,

CHCH₂), 2.26 (dd, J ) 18.8 and 2.9 Hz, 1H, ring CH₂), 2.25-

2.31 (m, 1H, ring CH), 2.50 (dd, J ) 7.8 and 7.8 Hz, 2H,

dCCH₂), 2.76 (dd, J ) 18.8 and 7.1 Hz, 1H, ring CH₂); ¹³C

NMR (50 MHz, CDCl₃) δ -4.43 (SiCH₃), -4.24 (SiCH₃), 13.78

(2 × CH₃), 17.41 (^tBu, q), 22.53 (CH₂), 22.95 (CH₂), 26.67 (^t-

Bu), 29.45 (CH₂), 30.38 (CH₂), 31.23 (CH₂), 34.38 (CH₂), 39.32

(ring CH₂), 46.46 (ring CH), 136.80 (dCSi), 189.77 (dCCH₂),

and 216.64 (CdO). Anal. Calcd for C₁₉H₃₆OSi: C, 73.95; H,

11.76. Found: C, 73.90; H, 11.90. 23: pale yellow oil, bp 160

°C/0.2 Torr; IR (CCl₄) 1695 (CdO), 1617 (CdC), and 1252

1-De u t e r io-3-(d im e t h ylp h e n ylsilyl)-2-p h e n ylp r op e -

n a l (2a -D_{(for m yl)}). With Rh₄(CO)₁₂(0.0060 g, 0.008 02 mmol),

Me₂PhSiD (0.672 g, 4.89 mmol), 1a (0.502 g, 4.92 mmol), and

Et₃N (0.541 g, 5.35 mmol) as starting materials, 2a -D_{(for m yl)}

was obtained analogously to 2a as a pale yellow oily liquid

(0.922 g, 71%, Z:E ) 87:13, 140 °C/0.09 Torr): IR (CCl₄) 2095

(CDO), 1680 (CdO), 1615 (CdC), 1580 (CdC), and 1250

(SiCH₃) cm^-1

.

3-De u t e r io-3-(d im e t h ylp h e n ylsilyl)-2-p h e n ylp r op e -

n a l (2a -D_{(vin yl)}). With Rh₄(CO)₁₂(0.0077 g, 0.0103 mmol),

Me₂PhSiH (0.271 g, 1.99 mmol), 1a -D (0.201 g, 1.95 mmol),

and Et₃N (0.181 g, 1.78 mmol) as starting materials, 2a -D_{(vin yl)}

was obtained analogously to 2a as a colorless oily liquid (0.460

g, 88%, Z:E ) 57:43, bp 140 °C/0.07 Torr): IR (CCl₄) 2730

(SiCH₃) cm^-^{1 1}H NMR (500 MHz, CDCl₃) δ -0.08 (s, 3H,

;

SiCH₃), -0.04 (s, 3H, SiCH₃), 0.86 (t, 3H, J ) 7.3 Hz, CH₃),

t

0.91 (t, J ) 7.3 Hz, 3H, CH₃), 0.93 (s, 9H, Bu), 1.22-1.29 (m,

4H, 2 × CH₂), 1.34 (sext, J ) 7.2 Hz, 2H, CH₂), 1.40-1.48 (m,

2H, CH₂), 1.57-1.64 (m, 1H, CSiCH₂), 1.71-1.77 (m, 1H,

CSiCH₂), 2.17 (t, J ) 7.8 Hz, 2H, dCCH₂), 2.27 (d, J ) 19.5

Hz, 1H, ring CH₂), 2.51 (d, J ) 19.5 Hz, ring CH₂), 7.19 (t, J

) 1.1 Hz, 1H, dCH); ¹³C NMR (50 MHz, CDCl₃) δ -7.63

(SiCH₃), -7.45 (SiCH₃), 13.65 (CH₃), 13.77 (CH₃), 18.61 (^tBu,

q), 22.40 (CH₂), 23.11 (CH₂), 24.27 (CH₂), 26.49 (CH₂), 27.80

(CHO), 1690 (CdO), 1580 (CdC), and 1253 (SiCH₃) cm^-1

.

Stoich iom etr ic Rea ction s of Rh ₄(CO)₁₂. Rea ction s in

a Sa m p le Tu be for ¹H NMR. The weighed starting materi-

als were charged consecutively into a ¹H NMR sample tube

containing 0.6 mL of CDCl₃under an Ar or CO atmosphere.

Rh-Catalyzed Silylformylation of Acetylenic Bonds

Organometallics, Vol. 16, No. 20, 1997 4345

The resulting solution was monitored at the respective stages

of the addition by H NMR spectroscopy.

as a pale yellow oily liquid. 29b: IR (CCl₄) 1667 (CdO), 1610

1

(CdC), and 1255 (SiCH₃) cm^-1; H NMR (500 MHz, CDCl₃) δ

Rea ction of Rh ₄(CO)₁₂w ith Me₂P h SiH (P r oced u r e 3).

A glass tube (12 mm o.d.) fitted with a stirring bar was charged

with Rh₄(CO)₁₂(0.0396 g, 0.0529 mmol) and CDCl₃(0.6 mL)

saturated with CO. The tube was placed in a 100 mL stainless

steel autoclave. The reactor was pressurized by CO to 20 kg/

cm². The contents were stirred for 20 min at ambient

temperature, and then the pressurized CO was purged under

a hood. Into this tube was added Me₂PhSiH (0.0274 g, 0.201

mmol) in CDCl₃(0.2 mL) through a syringe needle at ambient

temperature. The reactor was pressurized again by CO to 20

kg/cm². The contents were stirred for 14 h at 25 °C. After

excess CO was purged under a hood, the reaction mixture (now

cream yellow) was transferred into a sample tube for NMR

spectroscopy under a CO atmosphere. A sample for an IR

spectrum was prepared by an analogous procedure in hexane

solution. 28a : IR (hexane) 2102 (s), 2049 (s), 2017 (vs), and

-0.23 (s, 6H, 2 × SiCH₃), 0.39 (q, J ) 7.8 Hz, 8H, 2 × Si(CH₂-

CH₃)₂), 0.82 (t, J ) 7.8 Hz, 12H, 2 × Si(CH₂CH₃)₂), 6.60 (s,

2H, 2 × dCH), 7.14-7.17 (m, 4H, Ph), and 7.27-7.31 (m, 6H,

Ph); ¹³C NMR (125.7 MHz, CDCl₃) δ -5.07 (SiCH₃), 6.05

(SiCH₂), 7.38 (SiCH₂CH₃), 127.66 (Ph), 128.81 (Ph), 138.63 (Ph,

ipso), 140.45 (dCH), 155.92 (dC, q), and 197.76 (CdO); CI

MS m/z 435 (M⁺+ 1); EI MS m/z 434 (M⁺), 419 (M⁺- 15),

405 (M⁺- 29). Anal. Calcd for C₂₇H₃₈OSi₂: C, 74.59; H, 8.81.

Found: C, 74.51; H, 8.75.

Su bseq u en t R ea ct ion s of R h ₄(CO)₁₂w it h 1a a n d

Me₂P h SiH. Into a glass tube (12 mm o.d.) containing a CDCl₃

(0.5 mL) solution of Rh₄(CO)₁₂(5.70 mg, 0.007 62 mmol) was

added 1a (0.81 mg, 0.007 93 mmol) in CDCl₃(0.2 mL) under

a CO atmosphere. The resulting dark red solution was stirred

for 36 h at 25 °C to form 31 and then transferred to an NMR

1

sample tube through a syringe needle for H NMR observation.

1

1982 (w) cm^-1; H NMR (200 MHz, CDCl₃) δ 0.81 (s, 6H, Si-

When Me₂PhSiH (1.03 mg, 0.007 56 mmol) in CDCl₃(0.1 mL)

was added into this solution, (E)-3 was formed almost selec-

tively within 30 min. 31: ¹H NMR (200 MHz, CDCl₃) δ 7.00-

7.30 (m, 5H, Ph) and 9.16 (quint, J ) 1.0 Hz, 1H, tCH).

(CH₃)₂), 7.32-7.40 (m, 3H, Ph), 7.58-7.65 (m, 2H, Ph); ¹³C

NMR (125.7 MHz, CDCl₃, -55 °C, 9 mg of Cr(acac)₃was added)

δ 6.33 (SiCH₃), 127.64 (Ph), 128.44 (Ph), 132.56 (Ph), 142.92

(Ph, ipso), 189.37 (d, J ) 65.9 Hz, CdO).

P r ep a r a tion of 32a . A glass tube (25 mm i.d.) fitted with

a stirring bar was charged with Rh₄(CO)₁₂(0.0446 g, 0.0597

mmol) and CH₂Cl₂(3 mL) saturated by CO. The tube was put

in a 100 mL stainless steel autoclave. The reactor was

pressurized by CO to 20 kg/cm². The contents were stirred

for 15 min at ambient temperature, and then the pressurized

CO was purged under a hood. Into this tube was added 1a

(0.0134 g, 0.131 mmol) in CH₂Cl₂(1 mL) through a syringe

needle at ambient temperature. The reactor was pressurized

again by CO to 20 kg/cm². The contents were stirred for 20 h

at 25 °C. After excess CO was purged under a hood, the

reaction mixture was concentrated to about 1 mL by a CO

stream and diluted with 7 mL of hexane. This solution was

cooled to -78 °C and kept for 12 h at the same temperature.

The solid was collected on a glass filter and washed with

hexane to give 32a (0.032 g, 53%) as a yellow-brown powder.

32a : mp 92-95 °C dec; IR (CH₂Cl₂) 2129 (m), 2111 (w), 2094

P r ep a r a tion of a Solu tion of 28b a n d 28c. A CDCl₃

solution of these species was prepared according to procedure

1

3 for NMR spectroscopy. 28b: H NMR (200 MHz, CDCl₃) δ

0.46 (s, 3H, SiCH₃), 0.87-1.11 (m, 10H, Si(CH₂CH₃)₂); ¹³C

NMR (125.7 MHz, CDCl₃, -55 °C, 9 mg of Cr(acac)₃was added)

δ 3.27 (SiCH₃), 8.47 (SiCH₂), 13.38 (SiCH₂CH₃), and 189.81

(d, J ) 65.9 Hz, CdO). 28c: ¹H NMR (200 MHz, CDCl₃) δ

0.49 (s, 6H, Si(CH₃)₂), 1.01 (^tBu).

P r ep a r a tion of 29a by Rea ction of 28a w ith 1a u n d er

CO P r essu r e. Into a glass tube (28 mm o.d.) containing a

CH₂Cl₂(16 mL) solution of 28a resulting from a reaction of

Rh₄(CO)₁₂(0.0643 g, 0.0860 mmol) and Me₂PhSiH (0.044 g,

0.330 mmol) by an operation similar to procedure 3 was added

a CH₂Cl₂(1 mL) solution of 1a (0.0344 g, 0.337 mmol) through

a syringe needle at ambient temperature. The reactor was

pressurized by CO to 20 kg/cm². The contents were stirred

for 24 h at 25 °C. After excess CO was purged under a hood,

the volatiles were evaporated under reduced pressure. The

residual oily liquid was chromatographed on silica gel using

hexane/AcOEt (96/4) as an eluent to give 0.0503 g (61%) of

29a as a pale yellow oily liquid. 29a : IR (CCl₄) 1665 (CdO),

1

(vs), 2077 (m), 2053 (m), and 1665 (broad w) cm^-1; H NMR

(200 MHz, CDCl₃) δ 5.17 (d, J ) 1.0 Hz, 1H, tCH), 7.21-7.41

(m, 3H, Ph), 7.42-7.51 (m, 2H, Ph); ¹³C NMR (125.7 MHz,

CDCl₃, -55 °C, 9 mg of Cr(acac)₃was added) δ 63.91 (m, CH),

82.20 (m, quaternary C), 128.09 (Ph), 128.27 (Ph), 129.17 (Ph),

134.35 (Ph, ipso), 173.97 (d, J ) 70.9 Hz, CdO), 182.68 (t, J

) 42.4 Hz, CdO), 210.65 (d, J ) 21.4 Hz, CdO), and 214.17

(d, J ) 20.2 Hz, CdO). Anal. Calcd for C₁₅H₆O₇Rh₂: C, 35.75;

H, 1.20. Found: C, 35.89; H, 1.20.

1585 (CdC), and 1250 (SiCH₃) cm^-^{1 1}H NMR (500 MHz,

;

CDCl₃) δ 0.06 (s, 12H, 2 × Si(CH₃)₂), 6.77 (s, 2H, 2 × dCH),

7.02-7.07 (m, 4H, Ph), and 7.19-7.38 (m, 16H, Ph); ¹³C NMR

(125.7 MHz, CDCl₃) δ -2.21 (SiCH₃), 127.63 (Ph), 127.68 (Ph),

127.71 (Ph), 128.18 (Ph), 128.86 (Ph), 128.91 (Ph), 133.44 (Ph),

138.01 (Ph, ipso), 138.35 (Ph, ipso), 139.84 (dCH), 156.15 (dC,

q), and 197.46 (CdO). Anal. Calcd for C₃₃H₃₄OSi₂: C, 78.83;

H, 6.82. Found: C, 78.72; H, 6.92.

P r ep a r a tion of 29b by Rea ction of 28b w ith 1a u n d er

CO P r essu r e. Divinyl ketone 29b (0.0898 g, 81%) resulted

from a consecutive reaction of Rh₄(CO)₁₂(0.0916 g, 0.123 mmol)

with Et₂MeSiH (0.0523 g, 0.512 mmol) and 1a (0.0558 g, 0.546

mmol) in CH₂Cl₂(22 mL) according to the previous procedure

Ack n ow led gm en t. This work was supported by a

Grant-in-Aid for Scientific Research from the Ministry

of Education, Science, and Culture of J apan. We thank

Professor K. Takagi and Mr. K. Kondo for measurement

of mass spectra.

OM970549F

Article Doi

Rhodium-catalyzed silylformylation of acetylenic bonds: Its scope and mechanistic considerations

DOI: 10.1021/om970549f

Source and publish data:

Authors:

Article abstract of DOI:10.1021/om970549f

Full text of DOI:10.1021/om970549f

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