Interplay of hydrogenation and dehydrogenation in isoindoline and indoline isomers: a density functional theory study.

Under the conditions of palladium-catalyzed formate reduction, the isomers isoindoline and indoline undergo distinct hydrogenation and dehydrogenation processes to form 4,5,6,7-tetrahydroisoindole and indole, respectively. In terms of resonance energy, the reduction of isoindoline is accompanied by a loss of aromaticity, whereas the dehydrogenation of indoline occurs with a gain in aromaticity. To rationalize why isoindoline and indoline, under the same conditions of palladium catalysis, form different products, we used density functional theory calculations to investigate the mechanisms of the two reaction pathways.