Stereocontrolled Synthesis of gem-Difluoromethylenated Goniodiols and Goniothalamin Epoxides Based on Ring-Closing Metathesis

An efficient and general method to stereoselectively synthesize gem-difluoromethylenated goniodiols and goniothalamin epoxides has been developed. The introduction of a gem-difluoro­methyl-containing group was achieved by the reaction of aldehydes with 3-bromo-3,3-difluoropropene in the presence of indium. The gem-difluoromethylenated α,β-unsaturated-δ-lactone moiety was constructed through the ring-closing metathesis of highly electron-deficient gem-difluoromethylenated acryloyl esters by Grubbs’ II catalyst in toluene at reflux.