Elucidating the mechanism and origins of selectivity on catalyst-dependent cyclization reactions to form polycyclic indolines from a theoretical study

Abstract

There is a significant role for bioactive polycyclic indolines in the pharmaceutical science field. In this paper, a systematic DFT study at the M06-D3/SMD/BS2//B3LYP-D3/BS1 level is adopted to investigate the cyclization reaction catalyzed by Rh₂(esp)₂ and InCl₃ to generate polycyclic indolines. Luckily, the simplification of the Rh₂(esp)₂ computational model is feasible, and successfully used in this study. The computational results detailed indicate the reaction mechanisms catalyzed by different catalysts, and the regio- and diastereo-selectivity. The regio-selectivity is controlled by the weak interaction (reflected in repulsive interaction) of the key transition state in the InCl₃-catalyzed pathway, and the larger distortion energy makes the regio-selectivity more obvious in the pathway catalyzed by Rh₂(esp)₂. It is important that this theoretical study suggests the significance of the catalyst in the reaction system in detail by NBO and FMO analysis. This paper is a good explanation of the experimental phenomenon caused by the catalyst where InCl₃ is more significant than Rh₂(esp)₂. The reaction mechanism and the importance of the catalysts are revealed in detail by this particular theoretical study.