Fused Tetracyclic Quinoxalines from Reactions of o-Phenylenediamines in Polyphosphoric Acid

Abstract

The condensation of 2,3-diaminobenzoic acid and the 5-chloro derivative with o-hydroxyphenylglyoxylic acid, isatin and benzothiophen-2,3-dione in polyphosphoric acid leads to the appropriate tetracycles. Isomeric products are formed from these unsymmetrical diamines, and methods of assigning particular structures are described.