Reactions of 1,2-dichloro-3,3-difluorocyclopropene with methanolic sodium methoxide

Slow addition of sodium methoxide in methanol to 1,2-dichloro-3,3-difluorocyclopropene yields initially 1-chloro-2-methoxy-3,3-difluorocyclopropene. Further addition of methoxide in methanol yields preferentially Z 1-chloro-2-fluoro-3,3,3-trimethoxypropene and a small amount of dimethyl malonate. The ortho ester undergoes facile hydrolysis during the reaction and work up to form the acrylate ester, Z methyl 2-fluoro-3-chloroacrylate. A mechanism is suggested to account for the selective isomer formation.