New Efficient Synthesis of 2-Substituted 5,6,7,8-Tetrahydro-benzothieno[2,3-<i>d</i>]pyrimidin-4(3<i>H</i>)-ones

Abstract

The carbodiimides 4, obtained from aza-Wittig reactions of iminophosphorane 3 with aromatic isocyanates, reacted with secondary amines to give 2-dialkylamino-5,6,7,8-tetrahydro-benzothieno[2,3-d]pyrimidin-4(3H)-ones 6 in presence of catalytic EtO-Na+. Reactions of 4 with phenols or ROH in presence of catalytic K2CO3 or RO-Na+ gave 2-aryl(alkyl)oxy-5,6,7,8-tetrahydro-benzothieno[2,3-d]pyrimidin-4(3H)-ones 6 in satisfactory yields. The effects of the nucleophiles on cyclization have been investi­gated.