Asymmetric Intermolecular C-H Functionalization of Benzyl Silyl
Ethers Mediated by Chiral Auxiliary-Based Aryldiazoacetates and
Chiral Dirhodium Catalysts
Huw M. L. Davies,*Simon J. Hedley, andBrooks R. Bohall
Department of Chemistry, University at Buffalo, The State University of New York,
Buffalo, New York 14260-3000
hdavies@acsu.buffalo.edu
Received August 18, 2005
Abstract:
C-H functionalization of benzyl silyl ethers by means of rhodium-catalyzed insertions of aryldiazoacetates can be achieved in a highly diastereoselective and enantioselective manner by judicious
choice of chiral catalyst or auxiliary. The dirhodium tetraprolinates such as Rh2((S)-DOSP)4 have
been widely successful as chiral catalysts in the C-H functionalization chemistry of aryldiazoacetates, but give poor enantioselectivity in the reactions of aryldiazoacetates with benzyl silyl ether
derivatives. The use of (S)-lactate as a chiral auxiliary resulted in C-H functionalization with
moderately high diastereoselectivity (79-88% de) and enantioselectivity (68-85% ee). The best
results (91-95% de, 95-98% ee), however, were achieved using Hashimoto's Rh2((S)-PTTL)4 catalyst.
