Synthesis of esters of o-dicarboxylic acids of the quinoxaline series

Abstract

Esters of substituted quinoxaline-2,3-dicarboxylic acids (Table 1), which are intermediates in the synthesis of heterocyclic analogs of phthalocyanin [2,3], were synthesized by the condensation of aromatic o-diamines with esters of diketosuccinic acid [1]. A similar condensation is described only in the case of a heterocyclic o-diamine — 2,3-diaminoquinoxaline [4], 2,3-Dihydroxyquinoxaline was isolated instead of the expected ester of quinoxalinedicarboxylic acid in [5] by the reaction of o-phenylenediamine with diethyl diketosuccinate; however, we were able to obtain the normal condensation products by using pure starting ester.