Synthesis of 3-indolylazoles and meridianin derivatives from indolyl enaminonitriles

Abstract

The reaction of indole derivatives with cyanoacetic acid followed by treatment with DMFDMA gave the intermediate indolyl enaminonitriles (3). Further reaction with aminoguanidine yielded 5´-cyanomeridianin analogues (4). The same intermediate reacted with p-methoxyphenylhydrazine to give the pyrazolyl derivative (8). Treatment of (2E)-3-dimethylamino-2-(1H-indol-3-yl)-propenoate (3a) with hydroxylamine hydrochloride in basic medium afforded (5-amino-isoxazol-4-yl)-(1H-indol-3-yl)-methanone (5) and the acrylic acid derivative (6) after a short or a long heating, respectively. Unequivocal structural elucidation of the latter compound was achieved from single-crystal X-ray diffraction studies.