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......................
