A Consecutive Two-Step Radical-Mediated Cyclization of gem-Difluorinated Diynes to Access gem-Difluorinated Cedrenes

Abstract

A consecutive two-step radical-mediated cyclization of gem-difluoromethylenated bis(3-arylpropagyl)-indane-1,3-diones to access structurally unique gem-difluoromethylenated cedrenes is described. Substituents located on the aryl rings of the two propagyl units play an important role in governing the consecutive cyclization pattern. Upon treatment of gem-difluoromethylenated 1,3-diane with Bu₃SnH/AIBN, a tributylstannyl radical-mediated radical cyclization between the two diyne units chemoselectively took place, leading to the corresponding gem-difluoromethylenated acoradienes in good yields, after removal of tributylstannyl group by TFA. Subsequently, Bu₃SnH/AIBN promoted reductive cleavage of the phenylsulfanyl group leading to difluoroalkyl radicals which spontaneously underwent radical cyclization to give a series of gem-difluoromethylenated cedrenes.