ORGANIC
LETTERS
2001
Vol. 3, No. 25
4111-4113
Efficient Enantioselective Hydrosilylation
of Ketones Catalyzed by Air Stable
Copper Fluoride−Phosphine Complexes
Sabine Sirol, James Courmarcel, Naoue1l Mostefai, and Olivier Riant*
Laboratoire de Chimie Organique et Me´dicinale, Place Louis Pasteur, 1,
UniVersite´ catholique de LouVain, B-1348 LouVain-La-NeuVe, Belgium
Received October 16, 2001
ABSTRACT
Copper(II) fluoride−chiral diphosphine systems catalyze the hydrosilylation of several ketones with moderate to excellent enantioselectivities.
An oxygen acceleration effect was observed and led to a practical protocol with low catalyst loading.
The selective reduction of unsaturated double bonds (CdO,
CdN, CdC) catalyzed by homogeneous transition metal
complexes is of great interest in organic synthesis.1 Hydrosi-
lanes, which are by themselves inert toward nonactivated
carbonyl compounds, become suitable reductive agents for
the hydrosilylation of these compounds in the presence of
catalytic amounts of rhodium or titanium complexes.2
However, in most cases, the cost of the catalysts as well as
the rigorously anaerobic conditions required in those reac-
tions have limited their use in the laboratory. More recently,
new methods for the asymmetric hydrosilylation of prochiral
ketones using inexpensive hydride sources such as PMHS
(polymethylhydrosiloxane) and easily accessible catalysts
based on titanium,3 zinc,4 and tin5 have opened a new
pathway in this area in the view of practical applications.
(I) systems such as [CuH(PPh3)]6 or CuCl/PPh3/Bu4NF act
as a catalyst for the hydrogenation as well as the 1,4-
reduction of enones or enals in combination with silanes.6
Related work on copper(I)-phosphine systems has shown
that highly enantioselective 1,4-reduction of R,â-unsaturated
esters (80-92% enantiomeric excess (ee)) and cyclic enones
(87-98% ee) can be achieved with a catalyst formed from
CuCl/NaOtBu/chiral diphosphine (binap or BIPHEMP) and
PMHS.7 Very recently, Lipshutz has also demonstrated the
effectiveness of [CuH(PPh3)]6 for the hydrosilylation of
aromatic and nonconjugated aldehydes and ketones.8 This
report prompted us to display our own results on the
(3) (a) Carter, M. B.; Schiøtt, B.; Gutie´rrez, A.; Buchwald, S. L. J. Am.
Chem. Soc. 1994, 116, 11667-11670. (b) Yu, J.; Buchwald, S. L. J. Am.
Chem. Soc. 1999, 121, 5640-5644. (c) Rahimian, K.; Harrod, J. F. Inorg.
Chim. Acta 1998, 270, 330-336.
The potential of copper for hydride delivery was recog-
nized early, but it had mainly been used as a stoichiometric
reducing agent. It was later shown that phosphine-copper-
(4) Mimoun, H.; de Saint Laumer, J. Y.; Giannini, L.; Scopelliti, R.;
Floriani, C. J. Am. Chem. Soc. 1999, 121, 6158-6166.
(5) Lawrence, N.; Bushell, S. M. Tetrahedron. Lett. 2000, 41, 4507-
4512.
(6) (a) Lipshutz, B. H.; Keith, J.; Papa, P.; Vivian, R. Tetrahedron. Lett.
1998, 39, 4627-4630. (b) Mori, A.; Fujita, A.; Kajiro, H.; Nishihara, Y.;
Hiyama, T. Tetrahedron 1999, 55, 4573-4582. (c) Lipshutz, B. H.;
Chrisman, W.; Noson, K.; Papa, P.; Sclafani, J. A.; Vivian, R. W.; Keith,
J. M. Tetrahedron 2000, 56, 2779-2788. (d) Chen, J. X.; Daenble, J. F.;
Stryker, J. M. Tetrahedron 2000, 56, 2789-2798 and references therein.
(7) (a) Appella, D. H.; Moritani, Y.; Shintani, R.; Ferreira, E. M.;
Buchwald, S. L. J. Am. Chem. Soc. 1999, 121, 9473-9474. (b) Moritani,
Y.; Appella, D. H.; Jurkauskas, V.; Buchwald, S. L. J. Am. Chem. Soc.
2000, 122, 6797-6798.
(1) ComprehensiVe Organic Synthesis; Trost, B. M., Fleming, I., Eds.;
Pergamon Press: 1991; Vol. 8.
(2) (a) Ojima, I.; Kogure, T.; Nagai, Y. Tetrahedron. Lett. 1972, 49,
5098-5038. (b) Barr, K. J.; Berk, S. C.; Buchwald, S. L. J. Org. Chem.
1994, 59, 4323-4326. (c) Verdaguer, X.; Hansen, M. C.; Berk, S. C.;
Buchwald, S. L. J. Org. Chem. 1997, 62, 8522-8528. (d) Breeden, S. W.;
Lawrence, N. J. Synlett 1994, 833-835. (e) Reding, M. Y.; Buchwald, S.
L. J. Org. Chem. 1995, 60, 7884-7890. (f) Itsuno, S. In Organic Reactions;
Paquette, L. A., Ed.; Wiley: 1998; Vol. 52, Chapter 2, p 440. (g) Nishiyama,
H. In ComprehensiVe Asymmetric Catalysis; Jacobsen, E. N., Pfaltz, A.,
Yamamoto, H., Eds.; Springer-Verlag: 1999; Chapter 6.3.
(8) Lipshutz, B. H.; Chrisman, W.; Noson, K. J. Organomet. Chem. 2001,
624, 367-371.
10.1021/ol0169170 CCC: $20.00 © 2001 American Chemical Society
Published on Web 11/20/2001