ACCELERATION OF MICHAEL ADDITION-REACTION BY MICROWAVE IRRADIATION INTHE PRESENCE OF METAL-OXIDE CATALYSTS

The effect of microwave irradiation on Michael addition of beta-dicarb onyl compounds(acetyl acetone, methyl acetoacetate, dimethyl malonate and diethyl ethylmalonate) to methyl vinyl ketone was investigated by using four different metal oxide catalysts, i.e., CaO, MgO, Al2O3 and SiO2 without any solvent. The microwave irradiation markedly accelerat ed the addition reaction, reducing the reaction time dramatically in c omparison with the case of mechanical stirring (1/100-1/1500). The yie lds of the products were also moderately improved, and the values of t he yield were dependent on the metal oxide catalysts. Thus, the order was well correlated with the partial charge on oxygen atom in metal ox ide. This indicates that the more basicity due to larger partial charg e on oxygen atom makes easier to extract proton at alpha-position of d icarbonyl compounds.