Direct spiro heterocyclization of pyrrolobenzoxazinetriones under the action of diphenylguanidine

Spiro heterocyclization of 1-aryl-4-aroyl-5methoxycarbonyl-1Н-pyrrole-2,3-diones is described occurring under the action of 1,3-diphenylguanidine and proceeding due to the addition of the secondary amino group of diphenylguanidine to the atom С of pyrrolediones followed by the closure of the imidazole ring through the intramolecular attack of the secondary amino group of diphenylguanidine on the ester carbonyl group in the substituent in the position 5 of the pyrroledione ring accompanied with methanol elimination [1, 2]. The reaction of hetareno[е]pyrrole2,3-diones with guanidines was not studied.