New strategic reactions for organic synthesis: catalytic asymmetric C-H activation alpha to oxygen as a surrogate to the aldol reaction.
The C-H activation of silyl ethers by means of rhodium carbenoid-induced C-H insertion represents a very direct method for the stereoselective synthesis of silyl-protected beta-hydroxy esters. The reaction can proceed with very high regio-, diastereo-, and enantioselectivity and represents a surrogate to the aldol reaction. The reaction is catalyzed by the rhodium prolinate complex Rh(2)(S-DOSP)(4). A critical requirement for the high chemoselectivity is the use of donor/acceptor-substituted carbenoids such as those derived from methyl aryldiazoacetates. A range of silyl ethers may be used such as allyl silyl ethers, tetraalkoxysilanes, and even simple trimethylsilyl alkyl ethers. In general, C-H activation preferentially occurs at methylene sites, as the reactivity is controlled by a delicate balance between steric and electronic effects.
Davies
Huw M L
HM
Department of Chemistry, University at Buffalo, The State University of New York, Buffalo, New York 14260-3000, USA. hadvis@acsu.buffalo.edu
Beckwith
Rohan E J
RE
Antoulinakis
Evan G
EG
Jin
Qihui
Q