Lanthanide triflate catalyzed one-pot synthesis of dihydropyrimidin-2(1H)-thiones by a three-component of 1,3-dicarbonyl compounds, aldehydes, and thiourea using a solvent-free Biginelli condensation

Novel one-pot Biginelli-type reaction has been developed. Aromatic and aliphatic aldehydes with beta-dicarbonyl compounds and thiourea in the presence of catalytic amount 5 mol% of Yb(OTf)3 at 100degrees C for 60-90 min under solvent-free conditions proceeded smoothly to afford corresponding dihydropyrimidin-thiones. The yields of the classical Biginelli reaction can be increased from 20-50% to 81-91 % while the reaction time was shortened from 18-48 h to 60-90 min. In addition the catalyst can be easily recovered and reused.