Recyclization of isopropyl (1-aryl-4,5-dioxo-2-phenyl-4,5-dihydro-1H-pyrrol-3-yl)oxoacetates by the action of o-aminophenol

Abstract

SHORT COMMUNICATIONSReactions of 4-acyl-1H-pyrrole-2,3-diones with o-phenylenediamine and o-aminobenzenethiol involve successive attack by two nucleophilic centers of the reagents on the carbon atom in position 5 and carbonyl group in the acyl substituent on C 4 of the substrate to give substituted pyrrolobenzodiazepines [1] and pyrrolobenzothiazepines [2], respectively.We have found that isopropyl (1-aryl-4,5-dioxo-2-phenyl-4,5-dihydro-1H-pyrrol-3-yl)oxoacetates Ia and Ib react with o-aminophenol at a reactant ratio of 1 : 1 in anhydrous benzene at room temperature (reaction time 5-10 min) to produce in good yields isopropyl 2-hydroxy-4,5-dioxo-1-aryl-3-[(Z)-phenyl(2-hydroxyphenylamino)methylidene]pyrrolidine-2-carboxylates IIa and IIb instead of expected pyrrolobenzoxazepines. The spectral parameters of compounds IIa and IIb were very similar to those of isopropyl 2-hydroxy-4,5-dioxo-1-phenyl-3-[(Z)-phenyl(phenylamino)methylidene]pyrrolidine-2-carboxylate whose structure was determined by X-ray analysis [3].Presumably, compounds IIa and IIb are formed via initial addition of the primary amino group of o-aminophenol to C 5 of pyrrolediones Ia and Ib, cleavage of the pyrrole ring at the N 1 -C 5 bond, and subsequent closure of new pyrrole ring as a result of intramolecular nucleophilic addition of the nitrogen atom in the N-aryloxamoyl group to the ketone carbonyl carbon atom in the isopropoxalyl fragment.The described reaction is an example of pyrroledione-pyrroledione recyclization (i.e., opening of dioxoAr = Ph (a), 4-MeOC 6 H 4 (b).

Five-membered 2,3-dioxo heterocycles: LXXII. Recyclization of isopropyl 2-(1-aryl-4,5-dioxo-2-phenyl-4,5-dihydro-1H-pyrrol-3-yl)-2-oxoacetates by the action of aliphatic amines

“…Reactions of isopropyl 2-(1-aryl-4,5-dioxo-2-phenyl-4,5-dihydro-1H-pyrrol-3-yl)-2-oxoacetates with aromatic amines involve initial nucleophile addition at the carbon atom in position 2 or 5, followed by opening of the pyrrole ring at the N 1 -C 2 or N 1 -C 5 bond and intramolecular cyclization to isopropyl 1-aryl-2-hydroxy-4,5-dioxo-3-[phenyl(arylamino)methylidene]pyrrolidine-2-carboxylates [4][5][6]. Reactions of 4-acyl-substituted 1H-pyrrole-2,3-diones with aliphatic amines were not studied previously.…”