Rhodium-catalyzed hydroarylation and -alkenylation of alkynes with silanediols. A crucial role of the hydroxy group for the catalytic reaction

Article abstract of DOI:10.1055/s-2002-19785

Aryl- and alkenylsilanediols, which possess two hydroxy groups on the silicon atom, undergo the rhodium-catalyzed addition of an organic group on silicon to internal alkynes. Treatment of several internal alkynes with aryl- or alkenylsilanediols in the pr

Full text of DOI:10.1055/s-2002-19785

LETTER
295
Rhodium-catalyzed Hydroarylation and -Alkenylation of Alkynes with
Silanediols. A Crucial Role of the Hydroxy Group for the Catalytic Reaction
R
hodium-cataly
o
zedHydroar
s
ylationan
h
d
-alkenylati
i
onof
A
n
lkynes ari Fujii, Tooru Koike, Atsunori Mori,* Kohtaro Osakada
Chemical Resources Laboratory, Tokyo Institute of Technology, 4259 Nagatsuta, Yokohama 226-8503, Japan
Fax +81(45)9245224; E-mail: amori@res.titech.ac.jp
Received 14 November 2001
(3 mol%) in toluene–H2O at 100 °C for 24 hours, 3 was
Abstract: Aryl- and alkenylsilanediols, which possess two hydroxy
groups on the silicon atom, undergo the rhodium-catalyzed addition
of an organic group on silicon to internal alkynes. Treatment of sev-
eral internal alkynes with aryl- or alkenylsilanediols in the presence
obtained in 73% yield (Equation). The Table shows the re-
sults on various alkynes (1a–c) with aryl- and alkenylsi-
lanediols (2 and 4–6). A cationic rhodium complex,
of 3 mol% of [Rh(OH)(cod)]2 affords the hydroarylated or hy- [Rh(cod)2]BF4, also catalyzed the arylation (64%, for 18
droalkenylated products in good yields. A crucial role of the hy-
h), whereas no reaction occurred with a neutral rhodium
droxy group of silanediol for the catalytic reaction is also discussed
with the related aryltin reagent.
complex, [RhCl(cod)]2. The reaction took place in tolu-
ene–H2O system efficiently, while the yield was found to
be much inferior in the absence of water. Symmetrical in-
Key words: silanediol, rhodium complex, hydroarylation, hy-
droalkenylation, internal alkyne
ternal alkynes 1a and 1b with alkyl or aryl substitutents
proceeded smoothly.5 On the other hand, phenylacety-
lene, a terminal alkyne, resulted in polymerization, and
We have recently described rhodium-catalyzed C–C
bond-forming reactions with silanediols to , -unsaturat-
ed carbonyl compounds affording both conjugate addition
and Mizoroki–Heck (MH)-type products in a controllable
manner as shown in Scheme 1.1,2 Further studies on the
rhodium-catalyzed reactions with organosilicon com-
pounds have been partly focused on a substrate that is un-
able to undergo -hydride elimination leading to the MH-
type product. Internal alkyne is a choice since it does not
possess an appropriate hydrogen atom to facilitate -hy-
dride elimination of the arylmetallated product.3 A recent
communication by Hayashi and co-workers on the rhodi-
um-catalyzed addition of arylboronic acids to alkynes4
prompted us to report our findings on the reaction with si-
lanediols. We discuss also that the hydroxy group on the
silicon atom plays a crucial role for the rhodium-catalyzed
reaction.
disubstituted alkynes bearing electron-withdrawing
groups such as methyl phenylpropiolate (PhC CCOOMe)
and
dimethyl
acetylenedicarboxylate
(MeO-
COC CCOOMe) afforded a complex mixture of uniden-
tified products. In addition to arylsilanediols,
alkenylsilanediol 6 also affected the hydroalkenylation to
afford the corresponding dienes 9 and 106 in good yields.
Although the reaction with an unsymmetrical alkyne 1c
proceeded, the regiochemistry was not controlled effec-
tively to result in giving a mixture of isomers 11 and 12.7
Equation
We consider that the key intermediate of the catalytic re-
action is an alkenylrhodium species, which would be sub-
jected to protonolysis leading to the product. On the other
hand, the similar reaction with tributyl(4-methoxyphe-
nyl)tin that did not possess any hydroxy groups resulted to
afford the hydroarylated product in < 5% yield with re-
covery of a considerable amount of the tin reagent both in
the presence and the absence of water.8 The results sug-
gest that the hydroxy group of silanediol plays a signifi-
cant role for protonolysis. Indeed, addition of
triethylsilanol or diisopropylsilanediol that did not pos-
sess a transferable organic group on silicon to the reaction
Scheme 1
When 4-octyne (1a) was treated with ethyl(4-methox-
yphenyl)silanediol (2) in the presence of [Rh(OH)(cod)]2
Synlett 2002, No. 2, 01 02 2002. Article Identifier:
1437-2096,E;2002,0,02,0295,0297,ftx,en;Y23101ST.pdf.
© Georg Thieme Verlag Stuttgart · New York
ISSN 0936-5214

296
T. Fujii et al.
LETTER
with the tin reagent could affect the hydroarylation as intermediate 13a would partly rearrange into 13b via in-
shown in Scheme 2. Butylboronic acid and phenol were tramelecular 1,4-hydrogen shift.4,9 The result that hy-
also found to be effective additives whereas benzoic acid droarylation with the aryltin reagent has not proceeded
resulted in no reaction.
even in the presence of water suggests following: Subse-
quent protonolysis of 13a or 13b does not proceed with
water but occurs via the reaction of 13 with SiO-H to re-
sult in giving the hydroarylated product as illustrated in
Scheme 3.
The rhodium-catalyzed reaction would occur via trans-
metalation-insertion sequence to give alkenylrhodium
spcecies 13a in a similar manner to other rhodium-cata-
lyzed reactions of silanediols1a and boron reagents.2 The
Table Rhodium-catalyzed Hydroarylation and -alkenylation of Alkynes with Silanediolsa
Alkyne
Silanediol
Solvent
Time (h)
24
Product, (Yield,b %)
toluene–H2O (10:1)
1a
2
3 (73)
3 (60)
toluene–H2O (10:1)
toluene–H2O (1:1)
toluene
18
3 (58)
3 (28)
3 (39)
3 (27)
3 (25)
dioxane–H2O (10:1)
dioxane
MeOH–H2O (10:1)
toluene–H2O (10:1)
24
4
7 (67)
5
8 (65)
9 (66)
10 (49)
6
1b
1c
5
11 (39)
12 (22)
a The reaction was carried out using 0.3 mmol of 1, 0.6 mmol of 2 and 4–6, and 0.009 mmol of [Rh(OH)(cod)]2 at 100 °C in 3.3 mL of solvent.
b Isolated yield after silica gel chromatography.
Synlett 2002, No. 2, 295–297 ISSN 0936-5214 © Thieme Stuttgart · New York

LETTER
Rhodium-catalyzed Hydroarylation and -Alkenylation of Alkynes
297
fate. Concentration of the solvent left a crude oil, which was sub-
jected to chromatography on silica gel (hexane) to afford 216 mg of
3 (66%).
Acknowledgement
This work was supported by a Grant-in-aid for Scientific Research
(No. 13650915) from Japan Society for the Promotion of Science.
References
(1) (a) Mori, A.; Danda, Y.; Fujii, T.; Hirabayashi, K.; Osakada,
K. J. Am. Chem. Soc. 2001, 123, 10774. (b) See
also:Hirabayshi, K.; Nishihara, Y.; Mori, A.; Hiyama, T.
Tetrahedron Lett. 1998, 39, 7893. (c) Hirabayashi, K.;
Ando, J.; Kawashima, J.; Nishihara, Y.; Mori, A.; Hiyama,
T. Bull. Chem. Soc. Jpn. 2000, 73, 1409. (d) Hirabayashi,
K.; Ando, J.; Nishihara, Y.; Mori, A.; Hiyama, T. Synlett
1999, 99. (e) Hirabayashi, K.; Kondo, T.; Toriyama, F.;
Nishihara, Y.; Mori, A. Bull. Chem. Soc. Jpn. 2000, 73, 749.
(2) Recent rhodium-catalyzed reactions with unsaturated
compounds: (a) Sakai, M.; Hayashi, H.; Miyaura, N.
Organometallics 1997, 16, 4229. (b) Sakuma, S.; Sakai, M.;
Itooka, R.; Miyaura, N. J. Org. Chem. 2000, 65, 5951.
(c) Takaya, Y.; Ogasawara, M.; Hayashi, T.; Sakai, M.;
Miyaura, N. J. Am. Chem. Soc. 1998, 120, 5579. (d) Oi, S.;
Moro, M.; Ono, S.; Inoue, Y. Chem. Lett. 1998, 83. (e) Oi,
S.; Moro, M.; Inoue, Y. Chem. Commun. 1997, 1621.
(f) Li, C.-J.; Meng, Y. J. Am. Chem. Soc. 2000, 122, 9538.
(g) Huang, T.; Meng, Y.; Venkatraman, S.; Wang, D.; Li, C.-
J. J. Am. Chem. Soc. 2001, 123, 7451. (h)Lautens, M.; Roy,
A.; Fukuoka, K.; Fagnou, K.; Martin-Matute, B. J. Am.
Chem. Soc. 2001, 123, 5358. (i) Oguma, K.; Miura, M.;
Satoh, T.; Nomura, M. J. Am. Chem. Soc. 2000, 122, 10464.
(3) (a) Du, X.; Suguro, M.; Hirabayashi, K.; Mori, A.;
Nishikata, T.; Hagiwara, N.; Kawata, K.; Okeda, T.; Wang,
H. F.; Fugami, K.; Kosugi, M. Org. Lett. 2001, 3, 3313.
(b) Oda, H.; Morishita, M.; Fugami, K.; Sano, H.; Kosugi,
M. Chem. Lett. 1996, 811. (c) Fugami, K.; Hagihara, S.;
Oda, H.; Kosugi, M. Synlett 1998, 477.
Scheme 2
Scheme 3
In conclusion, aryl and alkenylsilanediols were found to
promote the rhodium-catalyzed addition of an organic
group on silicon to internal alkynes. Although the similar
reaction with aryltributyltin that possess no hydroxy
group on tin did not proceed, several additives bearing hy-
droxy groups to the reaction could affect the reaction of
the tin reagent. The results suggest that the hydroxy group
of silanediol was found to play a crucial role for the aryla-
tion and alkenylation of organosilicon reagents.
(4) Hayashi, T.; Inoue, K.; Taniguchi, N.; Ogasawara, M. J. Am.
Chem. Soc. 2001, 123, 9918.
(5) All products were identical with authentic samples (ref.4).
(6) Xi, Z.; Hara, R.; Takahashi, T. J. Org. Chem. 1995, 60, 4444.
(7) (a) Kunai, A.; Kawakami, T.; Matsuo, Y.; Ishikawa, M.
Organometallics 1992, 11, 1593; (11). (b) Ikenaga, K.;
Kikukawa, K.; Matsuda, T. J. Org. Chem. 1987, 52, 1276;
(12).
(8) No rhodium-catalyzed carbostannylation of the alkyne
observed. Carbostannylation of alkynes catalyzed by Pd and
Ni complexes: (a) Shirakawa, E.; Yoshida, H.; Kurahashi,
T.; Nakao, Y.; Hiyama, T. J. Am. Chem. Soc. 1998, 120,
2975. (b) Shirakawa, E.; Yamasaki, K.; Yoshida, H.;
Hiyama, T. J. Am. Chem. Soc. 1999, 121, 10221.
Typical Experimental Procedure for the Rhodium-catalyzed
Hydroarylation and Hydroalkenylation with Silandiols is as
follows, (E)-4-(4-Methoxyphenyl)-4-octene (3)
(9) Although Hayashi reported that 98% of alkenylrhodium
rearrange to arylrhodium in the reaction of PhB(OH)2 with
Rh(acac)(C2H4)2/dppb (ref.4), the reaction of 2 with 1a in
toluene–D2O (10:1) showed 28% deuterium incorporation at
the vinylic position and 68% at the ortho position of the
aromatic ring.
To a mixture of 2 (595 mg, 3 mmol) and [Rh(OH)(cod)]2 (20 mg,
0.045 mmol) in 15 mL of toluene and 1.5 mL of H2O was added 1a
(0.22 mL, 1.5 mmol) and the resulting light yellow solution was
stirred at 100 °C for 24 h. After cooling to r.t. the mixture was
poured into the mixture of 1 M HCl and diethyl ether and the two
phases were separated. The organic layer was washed with sat. aq
NaHCO3 solution and brine and dried over anhyd magnesium sul-
Synlett 2002, No. 2, 295–297 ISSN 0936-5214 © Thieme Stuttgart · New York