A Novel Ring Transformation of 3a,5,6a-Triaryl-3,3a-dihydro-2H-furo[3,2-b]pyrrole-2,6(6aH)-diones into 3-Aroyl-2,5-diarylpyrrole Derivatives

Under aqueous conditions dimethylamine, piperidine, and triethylamine catalyzed the ring-transformation reaction of triaryl-2H-furo[3,2-b]pyrrole-2,6(6aH)-diones (1), giving benzoylhydroxy-1-pyrrolines 2, which afforded benzoylpyrroles 3 upon acid-catalyzed dehydration. The lactone-ring-opened amides 6 were obtained in the reaction of 1 with methylamine, pyrrolidine, piperidine, and perhydroazepine at room temperature in ethanol. Pyrrolidine and piperidine produced pyrrolecarboxamides 7 when the reaction was carried out in aqueous ethanol under reflux. Amides 6 afforded 7 upon treatment with the amines under the above-mentioned conditions.