Synthesis of pharmaceutically active dihydropyrimidinones by biginelli reaction under microwave irradiation

Abstract

Microwave irradiation has become a very useful tool in organic synthesis. Microwave technology in organic chemistry has been explored extensively within the last decade. Microwave irradiation often leads to a remarkable decrease in reaction time, increased yields, easier work-up matching with green chemistry protocols. There are a few reports on the synthesis of 3,4-dihydropyrimidin-2(1H)-ones under microwave irradiation. Here a convenient method is reported for the synthesis of 3,4-dihydropyrimidin-2(1H)- ones/thiones 1-14under microwave irradiation using catalytic amounts of zinc chloride for a threecomponent coupling of substituted aldehyde A, β-keto ester B and urea or thiourea C.While the Biginelli reaction with ZnCl2 is known , the reaction takes about 4-5 hour for completion under normal condition. The new protocol under microwave irradiation works in the absence of a solvent,, the yields are high and the reaction goes to completion within 3-4min as shown in Scheme1......................