Effect of methanol on the regioselectivity and reaction rate of 1,3-dipolar cycloaddition of methyldiazoacetate to methyl acrylate and butene-1

The effect of methanol as a solvent on 1,3-dipolar cycloaddition reaction of methyldiazoacetate to alkenes has been studied by DFT calculations. Reaction reactivity has been qualitatively analyzed by the frontier molecular orbital (FMO) approach and quantitatively estimated by hard and soft acid base (HSAB) theory. Application of the FMO theory to the (3 + 2)-cycloaddition process testifies that the specific solvation of methanol with reagents increases reaction rate in comparison to the gas phase, since it is reflected in Δε reduction. From the point of view of the HSAB theory was shown that the complexation of methanol with reagents plays a predominating role in the acceleration of the (3 + 2)-cycloaddition reaction, however, the neglecting of the solvent influence as polarized continuum will cause an appreciable error in the calculation results and, consequently, is not justified.