Abstract (Z)-3-Phenacylidene-and (Z)-3-hetaroylmethylidene-1-phenyl-1, 2, 3, 4- tetrahydroquinoxalin-2-ones react with oxalyl chloride to give 3-acyl-5-phenyl-1, 2, 4, 5- tetrahydropyrrolo [1, 2-a] quinoxaline-1, 2, 4-triones. Thermolysis of the latter generates acyl (3-oxo-4-phenyl-3, 4-dihydroquinoxalin-2-yl) ketenes which are stabilized via [4+ 2]- cyclodimerization followed by [1, 3]-acylotropic shift to afford 4-acyl-3-acyloxy-2-(3-oxo-4- ...