Formation of Isoxazolidines by Enantioselective Copper-Catalyzed Annulation of 2-Nitrosopyridine with Allylstannanes

摘要

Allenylsilanes and allylsilanes have been successfully used by Danheiser et al. and Knolker et al. as nucleophiles in reactions with activated alkenes using Lewis acids in formal [3+2] cycloadditions for the formation of substituted cyclo-pentanes. Analogous transformations with heteroolefins C=X (X = O, NR) have also been accomplished to provide the corresponding five-membered heterocycles. These annula-tions occur through initial C-C bond formation at the γ-C atom of the unsaturated silane with the π acceptor, followed by cationic 1,2-silyl migration and subsequent cyclization [Eq. (1)].