Detalle de: A density functional theory study of rhodium-catalyzed hetero-[5+2]- cycloaddition of cyclopropyl imine derivatives and alkynes

The intermolecular [5+2]-cycloaddition mechanism of cyclopropyl imines and alkynes catalyzed by [Rh(CO)2Cl]2 has been studied using density functional theory, comparing this multistep process with the two-step reaction in the absence of catalyst. Calculations show that a similar mechanism to that found for dihydroazepines could also lead to the formation of oxepines by replacing the imine nitrogen by oxygen. The results indicate that the formation of the oxepine can proceed with smaller barriers than those found for dihydroazepines. In fact, energy barriers are even smaller than those for other reactions employed for oxepine production, exhibiting values similar to those obtained for the reactions between acetilene and vinylcyclopropanes. Several substituted alkynes were tested for the reaction leading to no significant differences among them.