Catalytic asymmetric C-H activation of sp3 hybridized C-H bonds by means of carbenoid C-H insertions:: applications in organic synthesis

The development of practical catalytic asymmetric methods for selective C-H activation could revolutionize the approaches used for the construction of complex organic compounds [1]. In this review, our progress in achieving a practical and catalytic method for asymmetric intermolecular C-H activation using rhodium carbenoid intermediates will be described (Eq. (1)) [2]. The inherent advantage of the carbenoid method over traditional C-H activation processes is the ease of achieving a catalytic cycle. Efficient reactions using chiral catalyst loadings of 1% or less are readily achieved. In order for the carbenoid-induced C-H activation to be useful in organic synthesis, issues of enantioselectivity, diastereoselectivity and regioselectivity need to be controlled. We have demonstrated that rhodium carbenoids containing both electron donor and acceptor groups are ideal reagents for selective C-H functionalization of hydrocarbons [3]. The synthetic potential of this chemistry will be illustrated by examples in which the C-H activation is used as a surrogate for some of the classic C-C bond-forming reactions of organic synthesis. These classic reactions will include the Michael reaction, the aldol reaction, the Mannich reaction and the Claisen rearrangement. [GRAPHICS] (C) 2002 Elsevier Science B.V. All rights reserved.