Novel Synthesis of (Z)-Difluoroacrylates via a Highly Stereoselective Addition−Elimination Reaction

On treating readily prepared benzyl 2,3,3-trifluoroacrylate with various Grignard reagents, e.g., aryl-, alkyl-, or alkenylmagnesium halide, in the presence of a catalytic amount of copper(I) salt in THF at −78 °C for 1 h, the corresponding α,β-difluoroacrylates were obtained in 54−98% yields with high Z-selectivity.