Zinc metal-promoted stereoselective olefination of aldehydes and ketones with gem-dichloro compounds in the presence of chlorotrimethylsilane

A combination of zinc metal and a catalytic amount of chlorotrimethylsilane has been found to promote the transformation of various aldehydes and keto nes with gem-dichloro compounds, such as benzylidene dichloride (la) and me thyl dichloroacetate (Ib), to the corresponding cross-coupling products, su ch as substituted styrene 3 and methyl acrylates 4 derivatives, under mild reaction conditions in THF. The E-isomer of the corresponding alkenes was o btained stereoselectively in good-to-excellent yields. The reaction serves as a very convenient one-pot procedure.