Efficient synthesis of thieno[2,3- d]pyrimidin-4(3 H)-ones by a sequential aza-Wittig reaction/base catalyzed cyclization.

7-Benzyl-5,6,7,8-tetrahydropyrido[4′,3′:4,5]thieno[2,3- d]pyrimidin-4(3 H)-ones were synthesized by base catalyzed reactions of nucleophilic reagents (aliphatic amines, alcohols or phenols) with carbodiimides 4, which in turn were obtained by the aza-Wittig reaction of iminophosphoranes 3 with aromatic isocyanates. [ABSTRACT FROM AUTHOR]