Radical-induced cyclopentannulation of Henry (nitroaldol)-derived intermediates.

Tributyltin hydride-mediated cyclizations of 1-nitro-2-acetoxy-5-hexenes 7a-g having multiple substitutions on carbons 1 and 6 result in 2,3-substituted-1-acetoxycyclopentanes 1a-g. The substrates were prepared by nitroaldol reactions of silyloxyaldehydes followed by acetylation, desilylation, and oxidation to the acetoxynitroaldehydes 6a-e. Wittig olefination of aldehydes 6a-e then afforded substrates for the radical cyclizations. The overall scheme gave a diverse array of cyclopentanes, including gem-disubstituted cyclopentanes having substitution on three contiguous carbons.