Pyrimidine derivatives 4a-e were synthesized by Biginelli reaction under microwave irradiation. The effectiveness of different baths or containers including ceramic, silica gel, potsherd, alumina, and molecular sieve as heat sinks in mediating the microwave irradiation for the formation. of 4a-e has been investigated. All one-pot condensations of beta-Ketoester 1, aryl aldehyde 2, and (thio)urea 3 in heat sinks provide high yields of the desired compounds, particularly when reactions are run at low temperature. In, addition, we found that potsherd and ceramic are suitable heat sinks for preparation of these cyclocondensation products under microwave irradiation.