Cyclization reactions of β,β-difluoroalkyl radicals (-CF 2-C·) for synthesizing gem-difluorocyclic compounds

Abstract

Cyclization reactions of β,β-difluoroalkyl radicals were carried out. 5 or 6-Exo selective radical cyclizations gave gem-difluorocyclopentane or -cyclohexane derivatives in 53 – 96% yields. 2,5-Disubstituted-3,3-difluorotetrahydropyran derivatives were prepared in 36 – 82% yields with moderate trans-selectivity (2.0 : 1–3.1 : 1). 4,5-Disubstituted-3,3-difluorotetrahydropyran derivatives were obtained via radical deoxygenation in 60 – 74% yields. High stereo-selectivity of radical cyclization for the formation of gem-fluorotetrahydropyran rings was achieved by introducing the bulky TBDPS group onto the acceptor double bond.