PEG-embedded thiourea dioxide (PEG.TUD) as a novel organocatalyst for the highly efficient synthesis of 3,4-dihydropyrimidinones

The host–guest complex between polyethylene glycol and thiourea dioxide (PEG.TUD) was prepared via different approaches involving co-crystallization method and by a chemical reaction. The resulting PEG.TUD complex was found to be very active and recyclable catalyst for the direct synthesis of 3,4-dihydropyrimidinones via Biginelli condensation and provided high product yields. Interestingly, the corresponding poly(ethylene glycol)–thiourea complexes, PEG.TU, were found to be unreactive and no reaction occurred under similar reaction conditions.