A regioselective synthesis of dimethyl phthalide-3-phosphonates

Dimethyl phthalide-3-phosphonates having various substituents on the benzene ring were regioselectively synthesized by the reaction of N,N-diethyl-2-formylbenzamides with tert-butyldimethylsilyl dimethyl phosphite followed by treatment with methanesulfonic acid. N,N-Diethyl-2-formylbenzamides were regioselectively prepared by ortho lithiation-formylation of the corresponding benzamides