An efficient route for synthesis of 2-alkylamino benzo[b]thieno[3,2-d]pyrimidin-4(3H)-one

The carbodiimide 2, obtained from the aza-Wittig reactions of iminophosphorane 1 with alkyl isocyanates, reacted with primary amino to give 2-alkylamino benzo[b]thieno[3,2-d]pyrimidin-4(3H)-ones 4 and 5. The formation mechanism of the title compounds has been investigated.