New pathway of the reaction of hetareno[a]pyrrole-2,3-diones with NH nucleophiles

By reactions of 3-benzoylpyrrolo[1,2-a]quinoxaline-1,2,4(5H)-trione (Ia) with phenylhydrazine and of 3-benzoyl-1H-benzo[b]pyrrolo[1,2-d][1,4]oxazine1,2,4-trione (Ib) with 2-hydrazinobenzoic acid (reactant molar ratio 1 : 1, anhydrous acetonitrile, 1–3 min under reflux; TLC monitoring), we obtained products resulting from nucleophilic attack at the C carbon atom, (Z)-3-benzoyl-2-(2-phenylhydrazono)pyrrolo[1,2-a]quinoxaline-1,4(2H,5H)-dione (IIa) and (Z)-2-{2-(3-benzoyl)-1,4-dioxo-1H-benzo[b]pyrrolo[1,2-d][1,4]-oxazin-2(4H)-ylidenehydrazino}benzoic acid (IIb). The product structure was proved by X-ray analysis of compound IIb. Although the possibility for other (than those indicated above [1]) direction of nucleophilic attack on 4-acyl-1H-pyrrole-2,3-diones fused at the N–C bond to various heterocycles was theoretically predicted about 20 years ago [2], products of such reactions were isolated for the first time.