Recyclization of 2-imino-2h-1-benzopyrans under the influence of nucleophilic reagents. 1. New approach to the synthesis of 3-(1,3,4oxadi-, thiadi-, and triazolyl-2)coumarins

It has been found that under the action of hydrazides of carboxylic acids, 2-iminocoumarin-3-carboxamides are recyclized to N⁽¹⁾-acylamidrazones of coumarin-3-carboxylic acids. The use of N⁽¹⁾-acylamidrazones is proposed as a simple and effective means of synthesizing 3-(1,3,4-oxadi-, thiodi-, and triazolyl-2)coumarins. The possibilities of alternate schemes of synthesis are discussed, and a mechanism is suggested for the recyclization.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 186–192, February, 1996.