Functionalization of tetrahydroindol-4-one derivatives

Abstract

Available and effective methods of tetrahydroindol-4-one derivatives transformation are described, which include functionalization of the nitrogen atom, carbonyl group, side chains in positions 1,2,3,7 of the bicycle, as well as aromatization of the cyclohexene fragment in the presence of dehydrogenating agents. Original preparative approaches to the synthesis of [4,5]-fused indole derivatives (pyrroles, thiophenes, pyrazoles, isoxazoles, thiazoles, 1,2,3-triazoles, pyridazinones), implemented by introducing functional groups in the α-position to the carbonyl group with subsequent cyclocondensations (Hanch, Paal-Knorr, [4+2] and [3+2]-cyclization reactions) are reviewed. Beckman and Schmidt rearrangements in the chemistry of tetrahydroindolones are accompanied by a cycle expansion with the formation of lactams or their transformation products. The Fischer reaction allows to obtain polyheterocycles with a new indole ring at the same time as the Dimrot rearrangement allows to synthesize pyrroloquinolones. Among the ways of modifying side chains of tetrahydroindolone, the three-component Passerini reaction is the most promising one, which provides quick access to indolone-N-amino acid derivatives.