General procedure for the preparati

General procedure for the preparation of 3,4-dihydropyrimidinones/
thiones 4: A mixture of aldehyde 1 (2 mmol), ethyl acetoacetate
2 (2.5 mmol), urea/thiourea 3 (2.5 mmol) and triphenylphosphine
(0.2 mmol) was heated with stirring at 100 C for 10 h. After cooling,
the reaction mixture was poured into crushed ice with stirring.
The crude product was filtered, washed with cold water, dried and
recrystallized from 95% ethanol or ethyl acetate to give pure products
4 (42–70%). All compounds were fully characterized by mp, IR,
1H and 13C NMR spectroscopy.