Regioselective Hydroformylation of Enynes Catalyzed by a Zwitterionic Rhodium Complex and Triphenyl Phosphite

Article abstract of DOI:10.1021/jo982425y

The reaction of aliphatic 1-en-3-ynes with synthesis gas in the presence of the zwitterionic rhodium complex (η⁶-C₆H₅BPh₃)^-Rh ⁺(1,5-COD) and triphenyl phosphite affords formyl dienes in high stereoselectivity. This catalytic system provides a useful method for the hydroformylation of both nonfunctionalized and functionalized conjugated enynes under mild conditions, affording formyl dienes in moderate to good yields.

Full text of DOI:10.1021/jo982425y

3964
J . Org. Chem. 1999, 64, 3964-3968
Regioselective Hyd r ofor m yla tion of En yn es Ca ta lyzed by a
Zw itter ion ic Rh od iu m Com p lex a n d Tr ip h en yl P h osp h ite
Bernard G. Van den Hoven and Howard Alper*
Department of Chemistry, University of Ottawa, 10 Marie Curie, Ottawa, Ontario, Canada K1N 6N5
Received December 10, 1998
The reaction of aliphatic 1-en-3-ynes with synthesis gas in the presence of the zwitterionic rhodium
complex (η6-C6H5BPh3)-Rh+(1,5-COD) and triphenyl phosphite affords formyl dienes in high
stereoselectivity. This catalytic system provides a useful method for the hydroformylation of both
nonfunctionalized and functionalized conjugated enynes under mild conditions, affording formyl
dienes in moderate to good yields.
In tr od u ction
enynes is an attractive synthetic route for the preparation
of formyl dienes, an interesting subgroup of substituted
dienes used in the preparation of cyclized materials and
as chain extensions.8 Enynes may be prepared through
a variety of methods including the reaction of an alkyne
with various organometallic species, affording acetylenes
bearing alkyl, vinyl, aryl, or heteroaryl groups R to the
triple bond.9a More recent methods have been developed
using palladium and tris(2,6-dimethoxyphenyl)phosphine
to self-couple terminal alkynes or cross-couple terminal
alkynes to functionalized internal alkynes.9b
The use of rhodium-based catalysts for the hydro-
formylation of alkenes is well documented. In recent
years, the zwitterionic complex (η6-C6H5BPh3)-Rh+(1,5-
COD) (1) has been shown to be capable of hydrogenating
imines,10 hydroformylating alkenes,11 germylformylating
and silylformylating terminal alkynes,12,13 and polymer-
izing phenyl acetylene.14
The hydroformylation of alkenes is an important
industrial process which has been extensively investi-
gated for many years.1 In contrast, the hydroformylation
of alkynes to give R,â-unsaturated aldehydes has at-
tracted less attention until recently, since past research
resulted in poor product yields and selectivities.2
In 1995, Buchwald and co-workers3 reported an effec-
tive hydroformylation catalyst composed of Rh(CO)2acac
(acac ) acetylacetonate) and a sophisticated bisphosphite
ligand. This catalyst system enabled the hydroformyla-
tion of internal alkynes to occur under mild conditions
and with good selectivity. Last year, Hidai and co-
workers4 reported a heterobimetallic catalyst to hydro-
formylate internal acetylenes. The conditions used by
Hidai and co-workers were not as mild as those of
Buchwald, although the conversion and selectivity were
good. The Hidai group described the hydroformylation
of the conjugated enyne (Z)-1,4-diphenyl-1-buten-3-yne
to form (2E,4Z)-2,5-diphenyl-2,4-pentadienal as the ex-
clusive hydroformylation product in 80% conversion and
39% isolated yield. Doyama and others5a,b noted that
when an alkyne is conjugated to an alkene, the triple
bond is more reactive toward hydroformylation. Conju-
gated enynes undergo hydroformylation giving formyl
dienes in either a linear or branched fashion.
We now describe the use of catalytic quantities of 1,
in the presence of triphenyl phosphite, to attain the
Enynes find practical use in the preparations of
polymers6a and substituted benzenes6b and in enediyne
antibiotics.7 The catalytic hydroformylation of conjugated
(6) (a) Xu, W.; Alper, H.; Macromolecules 1996, 29, 6695-6699. (b)
Gevorgyan, V.; Takeda, A.; Yamamoto, Y. J . Am. Chem. Soc. 1997,
119, 11313-11314.
(7) Stang, P. J .; Diederich, F. Chapter 7. In Modern Acetylene
Chemistry; VCH Publishers: New York, 1995.
(8) (a) O′Shea, D. F.; Sharp, J . T. J . Chem. Soc., Perkins Trans. 1,
1997, 3025-3034. (b) Kimura, M.; Ezoc, A.; Shibata, K.; Tamaru, Y.
J . Am. Chem. Soc. 1998, 120, 4033-4034. (c) Barluenga, J .; Canteli,
R. M.; Flo´rez, J .; Gutie´rrez-Rodriquez, A.; Martin, E. J . Am. Chem.
Soc. 1998, 120, 2514-2522.
(9) (a) Sauveˆtre, R.; Normant, J . F. Tetrahedron Lett. 1982, 23,
4325-4328. (b) Trost, B. M.; Sorum, M. T.; Chan, C.; Harms, A. E.;
Ru¨hter, G. J . Am. Chem. Soc. 1997, 119, 698-708.
(10) Zhou, Z.; J ames, B. R.; Alper, H. Organometallics 1995, 14, 4.
4209-4212.
(11) (a) Alper, H.; Zhou, J . Q. J . Org. Chem. 1992, 57, 3729-3731.
(b) Totland, K.; Alper, H. J . Org. Chem. 1993, 58, 3326-3329. (c) Amer,
I.; Alper, H. J . Am. Chem. Soc. 1990, 112, 3674-3676. (d) Lee, C. W.;
Alper, H. J . Org. Chem. 1995, 60, 499-503.
(12) Monteil, F.; Alper, H. J . Chem. Soc., Chem. Commun. 1995,
1601-1602.
(13) Zhou. J . Q.; Alper, H. Organometallics 1994, 13, 1586-1591.
(14) Goldberg, Y.; Alper, H. J . Chem. Soc., Chem. Commun. 1994,
1209-1210.
(1) (a) Trost, B. M.; Fleming, I. In Comprehensive Organic Synthesis;
Perganon: Oxford, 1991; Vol. 4, pp 913-950. (b) Elschenbroich, C.;
Salzer, A. In Organometallics: A Concise Introduction, 2nd ed.; VCH
Publishers: New York, 1992; pp 434-437. (c) Cornils, B.; Herrmann,
W. A. In Applied Homogeneous Catalysis with Organometallic Com-
pounds; VCH Publishers: 1996; Vol. 1, pp 29-111.
(2) (a) Fell, B.; Beutler, M. Tetrahedron Lett. 1972, 3455-3456. (b)
Botteghi, C.; Salomon, C. Tetrahedron Lett. 1974, 4285-4288. (c)
Greenfield, H.; Wotiz, J . H.; Wender, I. J . Org. Chem. 1957, 22, 542.
(d) Wuts, P. G. M.; Ritter, A. R. J . Org. Chem. 1989, 54, 5180-5182.
(e) Campi, E. M.; J ackson, W. R.; Nilsson, Y. Tetrahedron Lett. 1991,
32, 1093-1094. (f) Nombel, P.; Lugan, N.; Mulla, F.; Lavigne, G.
Organometallics 1994, 13, 4673.
(3) J ohnson, J . R.; Cuny, G. D.; Buchwald, S. L. Angew. Chem., Int.
Ed. Engl. 1995, 34, 1760-1761.
(4) Ishii, Y.; Miyashita, K.; Kamita, K.; Hidai, M. J . Am. Chem. Soc.
1997, 119, 6448-6449.
(5) (a) Doyama, K.; J oh, T.; Takahashi, S. Tetrahedron Lett. 1996,
27, 4497-4500. (b) Doyama, K.; J oh, T.; Shiohara, T.; Takahashi, S.
Bull. Chem. Soc. J pn. 1988, 61, 4353-4360. (c) Campi, E. M.; J ackson,
W. R. Aust. J . Chem. 1989, 42, 471-478.
10.1021/jo982425y CCC: $18.00 © 1999 American Chemical Society
Published on Web 04/30/1999

Regioselective Hydroformylation Enynes
J . Org. Chem., Vol. 64, No. 11, 1999 3965
Ta ble 1. Hyd r ofor m yla tion of 2,7-Dim eth yl-1-octen -3-yn e (3a ) w ith CO/H2 Usin g Differ en t Ca ta lyst System s a n d
Solven tsa
entry
rhodium catalyst
ligand
solvent
reactn time (h)
convn (%)b
product ratio (4/5)c
isolated yield of 4a (%)d
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
(PhO)3P
(PhO)3Pe
(PhO)3Pf
(PhO)3P
(PhO)3P
(PhO)3P
Ph3P
CH2Cl2
CH2Cl2
CH2Cl2
Et2O
benzene
THF
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
48
48
24g
48
48
48
48
48
8l
>95
50
100
<10
100
60
50
<10
80
10:1
10:1
3:1
only 4a
4:1
52
26
37
42
39
16
20:1
2 (:1)h
undefinedj
10:1
dppbi
1
2k
51
33
10
11
Rh(CO)2acac
CO(PPh3)2RhCl
(PhO)3P
(PhO)3P
48
48
67
<5
5:1
only 4a
a
Reaction conditions: enyne (3a ), 3 mmol; rhodium catalyst, 0.12 mmol; triphenyl phosphite, 0.48 mmol; CH2Cl2, 10 mL; CO, 6 atm;
H2, 6 atm; 60 °C. The percent conversion was determined by the loss of the olefin 1H NMR signal at 5.17 ppm. c The ratio of 4/5 was
determined by the ratio of their aldehyde H NMR signals. The saturated aldehyde (5) proton signal appeared as a doublet approximately
b
1
d
0.10 ppm downfield from the unsaturated aldehyde (4). The product was isolated by Kugelrohr distillation followed by column
chromatography using pentane:ether (90:10) as eluant. e The reaction temperature was 50 °C. f The reaction temperature was 70 °C.
g
h
After 24 h a pressure drop of 80 psi was observed, and the reaction was stopped; this was consistent with a completed reaction.
A
cyclopentenone was identified by an olefin 1H NMR signal at 5.90 ppm in the crude mixture, it had a ratio of 1:2 to 4a . Campi and
J ackson identified this proton signal as being due to the cyclopentenone.5c A 2:1 ratio of dppb:1 was used. The reaction gave multiple
i
j
products in the 1H NMR region of 9-10 ppm. A 1.5:1 ratio of 2/1 was used. After 8 h a pressure drop of 80 psi was observed, and the
k
l
reaction was stopped.
hydroformylation of both simple and functionalized enynes
in good conversions, selectivities, and yields.
uct in all reactions. Unidentified polymeric material was
also formed, in accord with similar behavior for 2,2-
disubstituted olefins.15
Rea ction Op tim iza tion . The optimization of this
process was effected using 2,7-dimethyl-1-octen-3-yne
(3a ) as the model substrate. The hydroformylation pro-
cess is temperature, solvent, ligand, and catalyst depend-
ent (Table 1). The highest isolated yield of 4a resulted
using the conditions described in the previous paragraph
(Table 1, entry 1). Decreasing the temperature by 10 °C
(60 to 50 °C) leads to only 50% conversion of the enyne
(3a ) after 48 h (Table 1, entry 2). Increasing the tem-
perature by 10 °C (60 to 70 °C) leads to completion of
the reaction in 24 h. An undesirable consequence of the
increased reactivity is the substantial increase in the
formation of 5a (Table 1, entry 3). Use of benzene, THF,
or ether as the solvent results in lower yields of 4a (Table
1, entries 4-6). Mono- (Ph3P) and bidentate (dppb)
phosphorus ligands give inferior results when compared
with (PhO)3P (Table 1, entries 7 and 8). Ligand 2 affords
results comparable to those of (PhO)3P (Table 1, entry
9). The substituents present on 2 have a significant
influence on the rate of the reaction, resulting in a 6-fold
rate increase. Rh(CO)2acac and CO(Ph3P)2RhCl are in-
ferior to 1 (Table 1, entries 10 and 11).
Resu lts a n d Discu ssion
The phosphite skeleton of the ligand used by Buchwald
and co-workers (2),3 when applied in conjunction with a
rhodium catalyst, enables the hydroformylation of inter-
nal alkynes to be carried out under very mild conditions.
It was envisaged that this catalytic system could also
be used to carry out the hydroformylation of enynes
under mild conditions as well. We reasoned that a much
simpler phosphite such as triphenyl phosphite could be
used for the hydroformylation of enynes. Indeed, the
catalytic system of 1 with triphenyl phosphite gives
preferential hydroformylation of the triple bond in con-
jugated enynes affording unsaturated aldehydes in high
selectivity (eq 1).
Hyd r ofor m yla tion of En yn es. The hydroformylation
of 3b (Table 2) was reported previously by Campi and
J ackson5c using carbonylhydridotris(triphenylphosphine)-
rhodium(I) and excess triphenylphosphine as the cata-
lytic system at 80 °C and 26 atm of synthesis gas in
benzene. The formyl diene 4b and the cyclopentenone 6
were formed in 20% and 10% yields, respectively (eq 2).
Under the conditions described herein, the formyl diene
(4b) was obtained in 50% isolated yield (Table 2).
Treatment of enynes (3) (3-6 mmol) with 4 mol % 1,
16 mol % triphenyl phosphite, and 12 atm of CO/H2 (total
pressure) in CH2Cl2 affords one formyl diene in all cases.
The branched formyl diene (4) is the major product, with
the nonconjugated unsaturated aldehyde (5) as a byprod-
(15) Stevens, M. P. In Polymer Chemistry: An Introduction, 2nd ed.;
Oxford University Press: New York, 1990; Chapter 6.

3966 J . Org. Chem., Vol. 64, No. 11, 1999
Van den Hoven and Alper
Ta ble 2. Hyd r ofor m yla tion of En yn es (3) w ith CO/H2 Usin g Zw itter ion ic Rh od iu m (1) a n d (P h O)3P a
a
Reaction conditions: enyne (3), 6 mmol; 1, 0.24 mmol; triphenyl phosphite, 0.96 mmol; CH2Cl2, 10 mL; CO, 6 atm; H2, 6 atm; 60 °C;
36-48 h. The percent conversion was determined by the loss of the olefin 1H NMR signal at 5.17 ppm. c The ratio of 4/5 was determined
b
by the ratio of their aldehyde 1H NMR signals. The saturated aldehyde (5) proton signal appeared as a doublet approximately 0.10 ppm
d
downfield from the unsaturated aldehyde (4). The product was isolated by Kugelrohr distillation followed by column chromatography
using pentane:ether (90:10) as eluant.
In our investigation we examined three types of
conjugated enynes: internal acetylenes, terminal acety-
lenes, and functionalized internal acetylenes at the
position â to the triple bond. In the first case (Table 2)
only one unsaturated aldehyde was obtained in 50-55%
yield (4a , 4b, and 4c). In the second group, terminal
acetylenes, a multiple number of products were observed
from 1-ethynylcyclohexene after 12 h. In this situation
there was no selectivity, possibly due to the lack of any
steric interaction with the “R” substituent, as in the
internal acetylene case.
4f.16 In contrast, only one product (4e) was formed when
2,7-dimethyl-5-methoxy-1-octen-3-yne (3e) was the sub-
strate. The appearance of the minor product 4f' from 3f
(16) 1-(3-Methoxy-2-propynyl)cyclohexene, 3f, was prepared by the
reaction of 1-ethynylcyclohexene with n-butyllithium followed by
chloromethyl methyl ether. After hydroformylation under the same
conditions as for the nonfunctionalized enynes, a mixture of two
hydroformylated products was obtained, 4f and 4f'. The spectral data
-1
for 4f are as follows: IR ν(CO) 1690 cm
;
1H NMR δ 9.32 (s, 1H),
6.40 (t, 1H, J ) 5.8 Hz), 5.34 (m, 1H), 4.13 (d, 2H, J ) 5.8 Hz), 3.28 (s,
3H), 2.36 (m, 1H), 2.17 (m, 1H), 1.98 (m, 2H), 1.56 (m, 4H); 13C NMR
-1
δ 194.2. The spectral data for 4f' are as follows: IR ν(CO) 1690 cm
;
1H NMR δ 9.32 (s, 1H), 6.78 (s, 1H), 6.29 (m, 1H), 4.09 (s, 2H), 3.23 (s,
3H), 2.36 (m, 1H), 1.98 (m, 4H), 1.56 (m, 4H); 13C NMR δ 195.4.
Mixture: EI MS (m/e) 180 [M+]; EI HRMS calculated for C11H16O2 [M+]
180.11503, found 180.11510.
Placement of a methyl ether in the position â to the
triple bond, i.e., 3f, affords a second isomer of the formyl
diene (4f') in a ratio of 1:2 relative to the usual product

Regioselective Hydroformylation Enynes
J . Org. Chem., Vol. 64, No. 11, 1999 3967
promise. Hydroformylation in the presence of an ether
or an ester linkage allows ready access to products with
the potential for further interesting chemistry.
Exp er im en ta l Section
Ma ter ia ls. All chemicals were purchased from commercial
sources. The zwitterionic rhodium complex (η6-C6H5BPh3)-Rh+-
(1,5-COD) 1 was prepared as described by Schrock and
Osborn.17 All solvents were distilled under nitrogen prior to
use.
F igu r e 1. Rhodium coordination prior to hydroformylation.
H yd r ofor m yla t ion of Un fu n ct ion a lized Con ju ga t ed
En yn es. Into a 45 mL autoclave with a glass liner and stirring
bar were placed the zwitterionic rhodium catalyst 1 (0.24
mmol), triphenyl phosphite (0.96 mmol), the conjugated enyne
3 (6 mmol), and CH2Cl2 (10 mL). The autoclave was flushed
three times with carbon monoxide and pressurized to 6 atm,
and then hydrogen was introduced up to a total pressure of
12 atm. The autoclave was placed in an oil bath at 60 °C for
48 h and then allowed to cool to room temperature. The
autoclave was depressurized, and the solvent was removed by
rotary evaporation. The resulting yellow residue was separated
from the catalyst and polymeric material (if formed) by
Kugelrohr distillation to give a clear colorless liquid. Product
4 was further purified by silica gel chromatography using
pentane:ether (90:10) as the developer to give the formyl dienes
4a -c.
(E)-2-(1-Meth yleth en yl)-6-m eth yl-2-h epten -1-al (4a): col-
orless liquid; IR ν(CO) 1690 cm-1; 1H NMR δ 9.32 (s, 1H), 6.43
(t, 1H, J ) 7.4 Hz), 5.15 (d, 1H, J ) 1.0 Hz), 4.68 (d, 1H, J )
1.0 Hz), 2.34 (quintet, 2H, J ) 7.4 Hz), 1.80 (s, 3H), 1.54 (m,
1H), 1.30 (quartet, 2H, J ) 7.0 Hz), 0.83 (d, 6H, J ) 6.6 Hz);
13C NMR δ 194.4, 155.8, 146.9, 138.9, 117.2, 38.5, 28.4, 28.1,
23.2, 22.9; EI MS (m/e) 166 [M+]; EI HRMS calculated for
C
11H18O [M+] 166.13576, found 166.13541.
(E)-2-(1-Meth yleth en yl)-2-p en ten -1-a l (4b): colorless liq-
uid; IR ν(CO) 1690 cm-1; H NMR δ 9.29 (s, 1H), 6.40 (t, 1H,
J ) 7.6 Hz), 5.10 (d, 1H, J ) 1.0 Hz), 4.64 (d, 1H, J ) 1.0 Hz),
2.30 (quintet, 2H, J ) 7.6 Hz), 1.77 (s, 3H), 1.01 (t, 3H, J )
7.6 Hz); 13C NMR δ 194.4, 156.8, 146.5, 138.8, 117.1, 23.5, 23.1,
1
F igu r e 2. Proposed mechanism.
13.9; EI MS (m/e) 124 [M+]; EI HRMS calculated for C8H12
O
[M+] 124.08882, found 124.08891.
may be explained by prior coordination of the rhodium
catalyst with the oxygen atom of the methyl ether and
the triple bond (7) followed by subsequent hydroformy-
lation (see Figure 1). This same double coordination is
possible between the alkene and the alkyne in the
conjugated enyne prior to hydroformylation (8). Depend-
ing on the coordinating ability of the group â to the
alkyne, different ratios of products are possible. Prefer-
ence for one product is observed when there is a large
sterically hindered group at the opposite side of the
enyne.
A possible mechanism for the hydroformylation of
enynes is outlined in Figure 2. The initial step may
involve coordination of the rhodium with the double and
triple bonds (10). This step is followed by the intra-
molecular addition of the rhodium hydride to the triple
bond of the enyne affording the (E) isomer (11). In the
case of the ether substituent, the initial coordination is
between the rhodium catalyst, the triple bond, and the
ether oxygen. This complexation governs the selectivity
of the resulting unsaturated product. Carbonyl insertion
(12), and regeneration of the rhodium catalyst by hydro-
gen (9), releases the formyl diene (4).
(E)-2-(1-Meth yleth en yl)-2-h ep ten -1-a l (4c): colorless liq-
1
uid; IR ν(CO) 1690 cm-1; H NMR δ 9.33 (s, 1H), 6.44 (t, 1H,
J ) 7.6 Hz), 5.14 (d, 1H, J ) 1.0 Hz), 4.67 (d, 1H, J ) 1.0 Hz),
2.34 (quintet, 2H, J ) 7.2 Hz), 1.80 (s, 3H), 1.35 (m, 4H), 0.86
(t, 3H, J ) 6.8 Hz); 13C NMR δ 194.4, 155.7, 147.1, 138.9, 117.3,
31.5, 29.9, 23.2, 23.0, 22.9, 14.4; EI MS (m/e) 152 [M+]; EI
HRMS calculated for C10H16O [M+] 152.12012, found 152.12311.
Hyd r ofor m yla tion of 5-Acetyl-2,7-d im eth yl-1-octen -3-
yn e (3d ). Enyne 3d was prepared from 2,7-dimethyl-7-octen-
5-yn-4-ol by the following procedure. A solution of 2.8 mL (2.0
g, 20 mmol) of triethylamine in CH2Cl2 (5 mL) was added
dropwise to a stirred solution of 1.52 g (10 mmol) of 2,7-
dimethyl-7-octen-5-yn-4-ol, 1.43 mL (1.57 g, 20 mmol) of acetyl
chloride, and 0.12 g (1.0 mmol) of 4-(dimethylamino)pyridine
in CH2Cl2 (25 mL). After 2 h the reaction mixture was treated
with CH2Cl2 (50 mL), washed with 10% HCl, saturated
NaHCO3, and brine, and then dried over anhydrous MgSO4.
The solvent was removed by rotary evaporation to afford a
light yellow solution. The ester was further purified by silica
gel chromatography using CH2Cl2 as eluant (Rf ) 0.75) to give
3d as a colorless liquid (90% isolated yield): IR ν(CO) 1744
cm-1; 1H NMR δ 5.50 (t, 1H, J ) 7.4 Hz), 5.25 (d, 1H, J ) 1.0
Hz), 5.20 (d, 1H, J ) 1.0 Hz), 2.07 (s, 3H), 1.85 (s, 3H), 1.80-
1.58 (m, 3H), 0.90 (d, 6H, J ) 7.0 Hz); 13C NMR δ 170.6, 126.6,
123.2, 86.3, 63.7, 44.3, 25.4, 23.8, 23.1, 22.9, 21.6; MS (m/e)
194 [M+]; EI HRMS calculated for C12H18O2 [M+] 194.13068,
found 194.13074.
In conclusion, the catalyst system of the zwitterionic
rhodium conplex (1) and triphenyl phosphite is of value
for the hydroformylation of conjugated enynes. The use
of a readily available phosphite ligand under mild condi-
tions makes this process of considerable commercial
The hydroformylation of 3d was effected as described above
to give 4d .
(17) Schrock, P. R.; Osborn, J . A. Inorg. Chem. 1970, 9, 2339-2343.

3968 J . Org. Chem., Vol. 64, No. 11, 1999
Van den Hoven and Alper
(E)-4-Acetyl-2-(1-m eth yleth en yl)-6-m eth yl-2-h ep ten -1-
a l (4d ): colorless liquid; IR ν1(CO) 1742 cm-1 and ν2(CO) 1695
cm -1; 1H NMR δ 9.37 (s, 1H), 6.22 (d, 1H, J ) 8.4 Hz), 5.66 (t,
1H, J ) 8.4 Hz), 5.21 (d, 1H, J ) 1.0 Hz), 4.78 (d, 1H, J ) 1.0
Hz), 2.01 (s, 3H), 1.87 (s, 3H), 1.71 (m, 2H), 1.28 (m, 1H), 0.90
(d, 3H, J ) 6.6 Hz), 0.88 (d, 3H, J ) 6.6 Hz); 13C NMR δ 193.9,
170.8, 150.3, 146.70, 138.8, 118.8, 70.3, 43.7, 25.1, 23.8, 22.8,
22.4, 21.6; FAB MS (m/e) 225.1413 [M + H]+, calculated for
colorless liquid in 80% isolated yield: 1H NMR δ 5.25 (d, 1H,
J ) 1.0 Hz), 5.17 (d, 1H, J ) 1.0 Hz), 4.08 (t, 1H, J ) 8.4 Hz),
3.38 (s, 3H), 1.87 (s, 3H), 1.58 (m, 2H), 1.22 (m, 1H), 0.90 (d,
6H); 13C NMR δ 127.0, 122.2, 87.8, 70.6, 66.7, 45.2, 25.2, 24.0,
23.2, 23.0; MS (m/e) 166 [M+]; EI HRMS calculated for C11H18
O
[M+] 166.13576, found 166.13570.
The hydroformylation of 3e follows the same procedure used
for the acetyl ester (3d ).
C
13H20O3 [M + H]+ 225.1413.
(E)-4-Meth oxy-2-(1-m eth yleth en yl)-6-m eth yl-2-h ep ten -
-1
1-a l (4e): colorless liquid; IR ν(CO) 1695 cm
;
1H NMR δ
Hyd r ofor m yla tion of 5-Meth oxy-2,7-d im eth yl-1-octen -
3-yn e (3e). Enyne 3e was prepared from 2,7-dimethyl-7-octen-
5-yn-4-ol by the following procedure. A solution of 1.52 g (10
mmol) of the alcohol in pyridine (25 mL) was cooled to 0 °C
and treated with 4 g (20 mmol) of p-toluenesulfonyl chloride.
The reaction solution became brown with white crystals
(pyridinium chloride). After the reaction was complete the
mixture was added to 150 mL of ice-water. The tosylate
appeared oily and was taken up in ether. The aqueous layer
was extracted three times with additional portions of ether.
The collected fractions of ether were further washed with 10%
HCl, distilled water, and brine and dried over anhydrous Na 2-
SO4. The solvent was evaporated to give a pale yellow solution
of the tosylate.
Sodium (0.7 g, 30 mmol) was dissolved in 50 mL of
anhydrous methanol at 0 °C. A solution of the above tosylate
in 5 mL of anhydrous methanol was added slowly and was
allowed to react for 2 h. The solution was poured into 150 mL
of ice-water, extracted with ether, and dried over anhydrous
MgSO4. Evaporation of the ether afforded a clear yellow liquid.
The liquid was further purified by silica gel chromatography
using CH2Cl2 as eluant (Rf ) 0.85) to give 3e as a clear
9.43 (s, 1H), 6.27 (d, 1H, J ) 9.0 Hz), 5.22 (d, 1H, J ) 1.0 Hz),
4.74 (d, 1H, J ) 1.0 Hz), 4.18 (td, 1H, J d ) 4.4 Hz, J t ) 9.0
Hz), 3.25 (s, 3H), 1.87 (s, 3H), 1.60 (m, 2H), 1.19 (m, H), 0.89
(d, 6H, J ) 6.6 Hz); 13C NMR δ 194.0, 154.2, 147.9, 138.6,
118.0, 76.5, 57.7, 44.8, 25.0, 24.0, 23.4, 22.6; EI MS (m/e) 196
[M+]; EI HRMS calculated for C12H20O2 [M+] 196.14633, found
196.14782.
Ack n ow led gm en t. We are grateful to the Natural
Sciences and Engineering Research Council of Canada
for financial support of this research. We are indebted
to Professor Stephen L. Buchwald for providing a
sample of the bisphosphite ligand (2) to test under our
reaction conditions.
Su p p or t in g In for m a t ion Ava ila b le: 1H NMR and 13C
NMR spectra of 3d -f and 4a -f . This material is available
free of charge via the Internet at http://pubs.acs.org.
J O982425Y