In the course of our research on the synthesis of coumarins, the interaction of 2-iminocoumarin-3-carboxamides with a series of 2-aminothiophene-3-carboxamides was studied. It was established that the initial products - 2-substituted coumarin-3-carboxamides - can undergo rearrangement to 2-(coumarin-3-yl)thieno[2,3-d]pyrimidin-4-ones by refluxing in DMF.
cyclizations - heterocycles - lactones - Gewald reaction - coumarins