C O M M U N I C A T I O N S
Scheme 3. Enantioselective Trienylation
geometrical isomers (96:4 Z/E), but in the case of 3k, complete retention
of the geometry was observed.6
Table 2. Enantioselective Alkenylation with Various Vinylsilanes
1a-k and Ethyl Glyoxylate 2
(E,E,E)-trienylsilane 6 afforded the corresponding trienyl product 7 with
high enantioselectivity and geometrical purity in good yield (Scheme 3).
In summary, we have achieved dicationic Pd complex-catalyzed
alkenylation to give highly optically active allylic alcohols. The reaction
is applicable to dienylation and trienylation. Attempts to construct more
sterically demanding structures (e.g., quaternary carbon centers) are
ongoing.
T
(°C)
time
(h)
yield
(%)b
ee
(%)d
entry
R1
R2
R3
1
2
3
Ph (1a)
H
H
H
H
H
H
Me
Me
Me
H
H
H
H
H
H
H
H
0
0
0
0
r.t.
r.t.
0
0
r.t.
24
18
18
18
48
48
24
24
24
84
83
85
91
55
64
75
83
73
98
95
97
94
97
91e
99
99
99
4-OMe-C6H4 (1b)
3-OMe-C6H4 (1c)
2-OMe-C6H4 (1d)
4-CF3-C6H4 (1e)
nBu (1f)
4
Acknowledgment. We are grateful to Takasago International Co.
for providing BINAP derivatives and SEGPHOS. This research was
supported in part by a grant program “Collaborative Development of
Innovative Seeds” from the Japan Science and Technology Agency.
5a
6a
7
Ph (1g)
8
9
n-C6H11 (1h)
Me (1i)
Me
Supporting Information Available: Experimental procedures and
compound characterization data. This material is available free of charge via
----------------------------------------------------------------------------------------
10
H (1j)
H (1k)
Ph
H
H
0
r.t.
24
48
79c
60
96f
11a
nBu
95e
a Using 10 mol% catalyst. b Isolated yield. c A 96:4 Z/E mixture.
References
e
d Determined by HPLC analysis. Determined by H and 19F NMR analyses
1
after MTPA esterification. f Enantiopurity of the Z product.
(1) (a) Katsuki, T.; Martin, V. S. Org. React. 1996, 1. (b) Katsuki, T. In
ComprehensiVe Asymmetric Catalysis; Jacobsen, E. N., Pfaltz, A., Yama-
moto, H., Eds.; Springer: Berlin, 1999; Vol. 2, p 621. (c) Johnson, R. A.;
Sharpless, K. B. In Catalytic Asymmetric Synthesis; Ojima, I., Ed.; Wiley-
VCH: New York, 2000; p 231.
Additionally, a crossover experiment was examined to clarify whether
silicon transfer proceeds via an intra- or intermolecular process (Scheme
2). Only the intramolecular silicon transfer was observed, ruling out a
vinylpalladium intermediate, although Pd is well-known to engage in
transmetalation. The alcohol products were produced after desilylation
under the reaction conditions.
(2) For catalytic enantioselective alkenylation of aldehydes using organozinc reagents
via hydroboration, see: (a) Oppolzer, W.; Radinov, R. N. HelV. Chim. Acta 1992,
75, 170. (b) Oppolzer, W.; Radinov, R. N. J. Am. Chem. Soc. 1993, 115,
1593. (c) Oppolzer, W.; Radinov, R. N.; De Brabander, J. Tetrahedron Lett.
1995, 36, 2607. (d) Oppolzer, W.; Radinov, R. N.; El-Sayed, E. J. Org. Chem.
2001, 66, 4766. (e) Dahmen, S; Bra¨se, S. Org. Lett. 2001, 3, 4119. (f) Chen,
Y. K.; Lurain, A. E.; Walsh, P. J. J. Am. Chem. Soc. 2002, 124, 12225. (g) Ji,
J.-X.; Qui, L.-Q.; Yip, C. W.; Chan, A. S. C. J. Org. Chem. 2003, 68, 1589.
(h) Lurain, A. E.; Walsh, P. J. J. Am. Chem. Soc. 2003, 125, 10677. (i) Jeon,
S.-J.; Chen, Y. K.; Walsh, P. J. Org. Lett. 2005, 7, 1729. (j) Lauterwasser, F.;
Gall, J.; Ho¨fener, S.; Bra¨se, S. AdV. Synth. Catal. 2006, 348, 2068. (k) Salvi,
L.; Jeon, S.-J.; Fisher, E. L.; Carroll, P. J.; Walsh, P. J. J. Am. Chem. Soc. 2007,
129, 16119.
Scheme 2. Crossover Experiment for Silyl Substituents
(3) For catalytic enantioselective alkenylation of aldehydes using organozinc reagents
via hydrozirconation, see: (a) Wipf, P.; Xu, W. Tetrahedron Lett. 1994, 35,
5197. (b) Wipf, P.; Xu, W. Org. Synth. 1996, 74, 205. (c) Wipf, P.; Ribe, S.
J. Org. Chem. 1998, 63, 6454. (d) Li, H.; Walsh, P. J. J. Am. Chem. Soc.
2004, 126, 6538. (e) Li, H.; Walsh, P. J. J. Am. Chem. Soc. 2005, 127, 8355.
(4) For reviews of catalytic enantioselective alkenylation of aldehydes using organozinc
reagents with alkenylzirconocenes, see: (a) Wipf, P.; Kendall, C. Chem.sEur. J.
2002, 8, 1779. (b) Wipf, P.; Nunes, R. L. Tetrahedron 2004, 60, 1269.
(5) For a review of catalytic enantioselective alkenylation via hydrogenative coupling
of alkynes to carbonyls and imines, see: Skucas, E.; Ngai, M.-Y.; Komanduri, V.;
Krische, M. J. Acc. Chem. Res. 2007, 40, 1394.
With these successes in terms of high yield and enantioselectivity, we
attempted dienylation of ethyl glyoxylate 2 with dienylsilanes 4 (Table
3). Use of (E,E)-dienylsilane 4a gave the corresponding (E,E)-dienyl
alcohol product 5a in 95% ee with exclusive retention of E,E geometry
(entry 1). Both electron-donating MeO and electron-withdrawing CF3
substituents also led to high yield and enantioselectivity (97 and 96% ee)
(entries 2, 4). The low catalyst loading of 1 mol% slightly reduced the
enantioselectivity (96% ee) (entry 3). Dienylsilane 4d with an aliphatic
isovaleryl group gave high enantioselectivity (92% ee) (entry 5). Moreover,
(6) Long, M. J. C.; Aye, Y. Chem.sEur. J. 2009, 15, 5402.
(7) (a) Tomita, D.; Wada, R.; Kanai, M.; Shibasaki, M. J. Am. Chem. Soc. 2005,
127, 4138. (b) Motoki, R.; Tomita, D.; Kanai, M.; Shibasaki, M. Tetrahedron
Lett. 2006, 47, 8083. (c) Tomita, D.; Yamatsugu, K.; Kanai, M.; Shibasaki, M.
J. Am. Chem. Soc. 2009, 131, 6946.
(8) Evans, D. A.; Aye, Y. J. Am. Chem. Soc. 2006, 128, 11034.
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Orden, L. J. V.; White, P. S.; Gagne´, M. R. Org. Lett. 2002, 4, 727. (c) Aikawa,
K.; Kainuma, S.; Hatano, M.; Mikami, K. Tetrahedron Lett. 2004, 45, 183.
(d) Doherty, S.; Knight, J. G.; Smyth, C. H.; Harrington, R. W.; Clegg, W. J.
Org. Chem. 2006, 71, 9751. (e) Doherty, S.; Knight, J. G.; Smyth, C. H.;
Harrington, R. W.; Clegg, W. Organometallics 2007, 26, 5961. (f) Luo, H. K.;
Khim, L. B.; Schumann, H.; Lim, C.; Jie, T. X.; Yang, H. Y. AdV. Synth. Catal.
2007, 349, 1781. (g) Mikami, K.; Kawakami, Y.; Akiyama, K.; Aikawa, K.
J. Am. Chem. Soc. 2007, 129, 12950.
Table 3. Enantioselective Dienylation with Dienylsilanes 4a-d
(10) Shibasaki and Sodeoka have reported dicationic aqua Pd-catalyzed aldol-type
reactions via Pd enolates: (a) Sodeoka, M.; Ohrai, K.; Shibasaki, M. J. Org. Chem.
1995, 60, 2648. (b) Hamashima, Y.; Sodeoka, M. Chem. Rec. 2004, 4, 231.
(c) Umebayashi, N.; Hamashima, Y.; Hashizume, D.; Sodeoka, M. Angew. Chem.,
Int. Ed. 2008, 47, 4196.
entry
R
T (°C)
time (h)
yield (%)b
ee (%)c
(11) Luo, H. K.; Yang, H. Y.; Jie, T. X.; Chiew, O. S.; Schumann, H.; Khim, L. B.;
Lim, C. J. Mol. Catal. A: Chem. 2007, 261, 112.
1
Ph (4a)
-20
-20
0
0
-20
30
30
48
24
30
84
83
61
81
76
95
97
96
96
92.
(12) For diastereofacial selective vinylsilane addition to chiral glyoxylates, see: Mikami,
K.; Wakabayashi, H.; Nakai, T. J. Org. Chem. 1991, 56, 4337.
2
4-OMe-C6H4 (4b)
4-OMe-C6H4 (4b)
4-CF3-C6H4 (4c)
(CH3)2CHCH2 (4d)
3a
4
(13) Whether AgCl was filtered or not, the conditions of 10 mol% AgSbF6 to 5 mol%
BINAP-PdCl2 complex produced the same result. It was also observed that AgSbF6
did not catalyze the reaction.
5
(14) TCI ethyl glyoxylate polymer form in 47% toluene solution.
a Using 1 mol% catalyst. b Isolated yield. c Determined by HPLC analysis.
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