Stereoselective synthesis of methyl (Z)-α-methoxyacrylates via two-carbon homologation of aldehydes

Methyl (Z)-α-methoxyacrylates are generated in good yields by a mild, stereospecific two-carbon homologation of a wide variety of aldehydes utilizing commercial methyl 2,2-dichloro-2-methoxyacetate and CrCl2 under Barbier conditions at room temperature. A rational mechanism based upon a Reformatsky-type addition pathway or an in situ generated (E)-trioxo-chromium vinylidene carbenoid is proposed.