Enantioselective Hydrosilylation of Aryl Ketones
UPDATE
Scheme 2. Possible mechanism that accounts for the silane effect.
References
A
ketone (path B). Further studies are required to fully
understand the mechanistic pathway.
In summary, we have shown that the enantioselec-
tivity of hydrosilylation reactions mediated by Cu(I)
systems is strongly dependent upon the nature of the
silane. Among the tested silane substrates, phenyl-
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A
AHCTREUNG
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(methyl)silane appears to be the most promising can-
didate. Thus, the combination of this silane with a cat-
alytic amount of Cu(I)/BINAP catalyst is a remarka-
bly efficient system for the highly enantioselective hy-
drosilylation of aryl alkyl ketones. Two likely mecha-
nisms for this reaction may be proposed on the basis
of kinetic studies; however, further studies are
needed and will be the focus of our work in this area.
[3] a) H. Nishiyama, H. Sakaguchi, T. Nakamura, M. Hori-
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Experimental Section
General Procedure for the Hydrosilylation Reaction
(Table 2, entry 1).
A Schlenk tube was charged with CuCl (0.025 mmol), NaO-
t-Bu (0.025 mmol) and (R)-BINAP (0.025 mmmol). Dry tol-
uene was added under argon (5.0 mL) and the solution was
stirred for 20 min at room temperature. After cooling to
À788C, the silane (PhMeSiH2, 1.0 mmol) was added drop-
wise followed by the acetophenone (0.5 mmol). The yellow
solution was stirred at À788C for 16 h. Upon completion, a
solution of NaOH in methanol was added (2 mL, 1.0M) and
the resulting mixture was stirred for 1 h at room tempera-
ture. Column chromatography provided the desired alcohol;
yield: 60.4 mg (99%). GC analysis on a chiral column gave
a 93% ee (R). The absolute configuration was determined
by comparison of the optical rotation with literature values.
[8] B. H. Lipshutz, K. Noson, W. Chrisman, A. Lower, J.
Am. Chem. Soc. 2003, 125, 8779.
[9] H. Brunner, W. Miehling, J. Organomet. Chem. 1984,
275, C17.
[10] An efficient asymmetric conjugate reduction of a,b-un-
saturated esters or cyclic enones using chiral phos-
À
phine/Cu H systems was also reported: a) D. H. Ap-
Acknowledgements
pella, Y. Moritani, R. Shintani, E. M. Ferreira, S. L.
Buchwald, J. Am. Chem. Soc. 1999, 121, 9473; b) Y.
Moritani, D. H. Appella, V. Jurkauskas, S. L. Buchwald,
J. Am. Chem. Soc. 2000, 122, 6797; c) J. Yun, S. L.
Buchwald, Org. Lett. 2001, 3, 1129.
We thank the CNRS and the Ministère de l’Education Natio-
nale, de la Recherche et de la Technologie for a Ph.D. grant
(J.T.I) and an “ACI Jeunes chercheuses et jeunes chercheurs”.
Adv. Synth. Catal. 2006, 348, 1991 – 1994
© 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
1993