Synthesis of C2-Symmetric gem-Difluoromethylenated Angular Triquinanes.

A synthesis of symmetrical gem-difluoromethylenated angular triquinanes is described. The synthetic strategy involved sequential fluoride-catalyzed nucleophilic addition of PhSCF2SiMe3 (1) to 2,2-diallylated or 2,2-dipropargylated indane-1,3-diones 2 followed by stereoselective radical cyclization of the resulting adducts 3 to provide the cyclized gem-difluoromethylenated diquinanes 4 as a mixture of stereoisomers. Repeated addition of 1 to 4 followed by cyclization resulted in the stereoselective synthesis of the desired C2-symmetric gem-difluoromethylenated angular triquinanes 6 in good yields with high stereoselectivity.