Cascade recyclization of pyrrolo[1,2-c][4,1]benzoxazepinetriones with o-phenylenediamine

4-Acyl-1H-pyrrole-2,3-diones fused through the N–C bond to azaheterocycles are known to react with o-phenylenediamine along three pathways. 3-Aroyland 3-hetaroylpyrrolo[2,1-c][1,4]benzoxazine-1,2,4triones (1H-pyrrole-2,3-diones fused through the N–C bond to benzoxazinone fragment) react with o-phenylenediamine via initial addition of one amino group of the reagent to C, followed by opening of the oxazine and pyrrole rings and formation of quinoxalin2-one derivatives [1, 2]. Reactions of 3-aroylpyrrolo[1,2-a]quinoxaline-1,2,4-triones (1H-pyrrole-2,3-diones fused through the N–C bond to quinoxalinone fragment) and 8-aroyl-3,4-dihydropyrrolo[1,2-a]pyrazine-1,6,7(2H)-triones (1H-pyrrole-2,3-diones fused through the N–C bond to pyrazinone fragment) with o-phenylenediamine also involve initial addition of the amino group to C, but next follows intramolecular cyclization with participation of the aroyl carbonyl group and formation of substituted benzo[b]pyrrolo[2,3-e][1,4]diazepines [3] and benzo[b]pyrazino[1′,2′ : 1,2]pyrrolo[2,3-e][1,4]diazepines [4], respectively. 3-Pivaloylpyrrolo[1,2-a]quinoxaline-1,2,4(5H)triones take up o-phenylenediamine molecule at the C atom with subsequent opening of the pyrrole ring and heterocyclization to 3,3′-(2-oxobutane-1,1-diyl)di[quinoxalin-2(1H)-one] derivatives [5]. We have synthesized new hetareno[e]pyrrole-2,3diones, 3-aroylpyrrolo[1,2-c][4,1]benzoxazepine-1,2,4triones [6], and studied their reaction with o-phenylenediamine. The reactions of 3-aroylpyrrolo[1,2-c][4,1]benzoxazepine-1,2,4-triones 1a and 1b with o-phenylenediamine were carried out by heating the reactants in boiling anhydrous chloroform for 4–5 min. As a result, we isolated (Z)-4-aryl-N-[2-(2-hydroxymethyl)phenyl]-2,4-dioxo-3-[3-oxo-3,4-dihydroquinoxalin-2(1H)-ylidene]butanamides 2a and 2b whose spectral characteristics were fairly similar to those of methyl (E)-4-[(4-chlorophenyl)amino]-3,4-dioxo-2-[3oxo-3,4-dihydroquinoxalin-2(1H)-ylidene]butanoate; the structure of the latter was determined by X-ray analysis [7]. Presumably, compounds 2 are formed as a result of nucleophilic attack by the amino groups of o-phenylenediamine on the C and C atoms of 1 and subsequent opening of the oxazepine ring at the C–O and C–N bonds. The described reaction may be regarded as cascade recyclization of pyrrolo[1,2-c][4,1]benzoxazepintriones by the action of o-phenylene-