Vinylation of Aldehydes Using Mn/Cr Alloy and a N4-Ligand/NiII-Catalyst.

We report an efficient and practical protocol for the Cr/Ni-catalyzed vinylation of aldehydes, based on the use of Mn/Cr alloy (ca. 10 % Cr) and TMSCl. No additional Cr salts need to be added. In the presence of NiCl2 (0.3 mol %) and a bis(ketimino)-2,2'-bipyridine as N4 -chelating ligand (1 mol %), the vinylations proceed smoothly at room temperature. The presence of catalytic amounts of MeOH and LiOAc as additives was found to further promote the efficiency of the catalytic system, even in the absence of the ligand. Detailed reaction monitoring revealed that LiOAc accelerates the product alcohol silylation, thus increasing the turnover rate.