A computational study on the substituent effects and product stereoselectivity of the intermolecular formal aza-[3+3] cycloaddition reaction between vinylogous amides and alpha,beta-unsaturated imine cations

摘要

The substituent effects and product stereoselectivity of the title reaction has been studied using density functional theory (DFT) calculations at the B3LYP/6-31G(d,p) level of theory. It was found that the substituents do not perturb the mechanism of intermolecular formal aza-[3+3] cycloaddition. Our calculations also show that methyl or benzyl groups on the N atom of vinylogous amide favor the addition step, but alkyl substituents on the either N atom or terminal C atom of a, P-unsaturated imine cation have opposite effects. Alkyl substituents on the N atom of alpha,beta-unsaturated imine cation may lower the activation barriers for elimination of amide. The steric interaction between two substituents leads to the formation of major product both thermodynamically and kinetically. (c) 2006 Elsevier B.V. All rights reserved.