Cyclization Reaction of Donor-Acceptor Oxiranes with N,N'-Disubstituted Thioureas: A Domino Process to trans-Dihydropyrimidines.

An unprecedented cyclization reaction of donor-acceptor oxiranes with N,N'-disubstituted thioureas to construct trans-dihydropyrimidines is presented. Preliminary reaction mechanism studies demonstrated that the reaction underwent sequential cycloaddition/amine ester exchange/oxygen-sulfur exchange/desulfuration/Michael addition process. A wide range of trans-dihydropyrimidines were produced with high yields up to 94% by using this method.