Catalyst-Controlled Stereoselective Construction of Indole-Fused Heterocycles through Cycloadditions of Indolyl-Allenes: A Theoretical Investigation

The mechanisms and stereoselectivity of Pt- and Au-catalyzed cycloaddition of N-(2-(1H-indol-1-yl)-ethyl)-N-(4-cyclopropyl-2-methylbuta-2,3-dien-1-yl)-4-methylbenzenesulfonamide have been theoretically investigated with the aid of density functional theory (DFT) calculations. Our results reveal that the rate- and stereoselectivity-determining step are both the tandem cyclization. The stereoselectivity observed in the experiment could be interpreted through our calculations. The steric and electronic properties of the cyclopropyl group account for the stereoselectivity.