AN EFFICIENT SYNTHESIS OF 1,3-DIARYL-PYRROLO[1,2-a]QUINOXALINES FROM 2-(1H-PYRROL-1-YL)PHENYLAMINES

The condensation of 1,3-diaryl-4-bromo-2-buten-1-ones with o-phenylenediamine leads to 2-[2,4-diaryl-1H-pyrrol-1-yl]phenylamines. Heating solutions of these compounds in formic acid leads to formylation and intramolecular condensation to give 1,3-diarylpyrrolo[1,2-a]quinoxalines. The acylation of 2-[2,4-diphenyl-1H-pyrrol-1-yl]phenylamine with acetic anhydride in acetic acid leads to an acetamide, which readily cyclizes to give 4-methyl-1,3-diphenylpyrrolo[1,2-a]quinoxaline upon heating with POCl(3).