Recyclization of 2-imino-2H-1-benzopyrans under the action of nucleophilic reagents: the novel approach for 2-(coumarin-3-yl)-3H-quinazolin-4-thiones

The series of approaches for synthesis of 2-(coumarin-3-yl)-3H-quinazolin-4-thiones were evaluated and it was established that the ‘recyclization’ of 2-iminocoumarin-3-carboxamides under the action of 2-aminothiobenzamide appeared to be the preferable approach compared to the thionation of 2-(coumarin-3-yl)-3H-quinazolin-4-ones. The proposed method allowed us to obtain the desired 2-(coumarin-3-yl)-3H-quinazolin-4-thiones in a short time with excellent yields using a one-pot synthetic procedure.