A novel method for the synthesis of α, β-unsaturated compounds was developed by using methanol as a methylenylating agent. Methyl or methylene group at α-position of saturated ketones, esters or nitriles is converted into vinyl group by the addition of methanol over metal ion containing magnesium oxide catalysts, M-MgO [M=Cr(III), Fe(III), Al(III), Mn(II), Ni(II), Cu(II)]. The most promising application of this method is demonstrated by the selective synthesis of acrylonitrile from acetonitrile and methanol over Cr-MgO catalyst. Selectivity to acrylonitrile of more than 95% is attained at 10% conversion of acetonitrile and no deactivation of the catalyst is observed. The method was also applied to the conversion of acetone to methyl vinyl ketone and that of methyl propionate to methyl methacrylate. It was found that the step determining the rate of reaction was the abstraction of α-hydrogen from substrates by surface basic sites. Reaction mechanism and role of added metal ion are discussed.