Mechanistic study on [3+2] cycloaddition and cyclopropanation reactions of 1,3-dioxepine derivatives in the presence of copper (I) catalyst

The density functional theory method at the B3LYP/6-31G(d) level of theory is used to determine the mechanism of [3+2] cycloaddition and cyclopropanation reactions of 1,3-dioxepine derivatives with dimethyldiazomalonate (DMDM) in the presence of a copper(I) catalyst. The dynamics of the catalytic [3+2] cycloaddition mechanism have been elucidated, and it is found that the reaction proceeds via a stepwise pathway due to the presence of copper. The experimental product distribution for the reaction of DMDM with 4,5-dihydro-2-methyl-1,3- dioxepine and 4,7-dihydro-2-methyl-1,3dioxepine in the presence of Cu(I) catalyst has also been reproduced and explained by means of computational tools. Calculated results enabled us to explain the reactivity behaviors based on differences in free energy barriers and NBO analysis.