New Reactions of Contraction of the o-Quinone Ring with the Formation of Derivatives of 2-(2-Indolyl)-cyclopenta[b]pyrrole-3,4-diones and Pyrindino[1,2-a]indoles: A Combined Experimental and Density Functional Theory Investigation

[Image: see text] Derivatives of 2-(2-indolyl)-cyclopenta[b]pyrrole-3,4-diones and pyrindino[1,2-a]indoles were synthesized by a new reaction of contraction of the o-quinone ring, and their structures were investigated by X-ray crystallography and nuclear magnetic resonance spectroscopy. The mechanisms of the reactions were suggested based on density functional theory calculations of the critical parts of the potential energy surfaces.