N-Substituted Ureas and Thioureas in Biginelli Reaction Promoted by Chlorotrimethylsilane: Convenient Synthesis of <i>N</i>1-Alkyl-, <i>N</i>1-Aryl-, and <i>N</i>1,<i>N</i>3-Dialkyl-3,4-Dihydropyrimidin-2(1<i>H</i>)-(thi)ones

Abstract

The classical Biginelli reaction has been extended by the use of N-substituted ureas and thioureas. A set of N1-alkyl-, N1-aryl-, and N1,N3-dialkyl-3,4-dihydropyrimidin-2(1H)-(thi)ones was readily prepared in excellent yield when chlorotrimethylsilane in N,N-dimethylformamide was used as promoter and water scavenger.