Synthesis of quinoxalinones by the reaction of o-phenylenediamines with dimethyl acetylenedicarboxylate

The reaction of N-monosubstituted o-phenylenediamines with dimethyl acetylenedicarboxylate gives 1-substituted 3-(ethoxycarbonylmethylene)-3,4-dihydroquinoxalin-2(1H)-ones. Hydrolysis and decarboxylation of these products is accompanied by rearrangement to the 1-substituted 3-methylquinoxalin-2-ones. In the case of the product derived from 7-amino-2-methylindoline, the intermediate 3-methylene com…