Effect of hydrogen bonds and CF group on the regioselectivity and mechanism of [3 + 2] cycloaddition reactions between nitrile oxide and 2,4-disubstituted cyclopentenes. A MEDT study.

The mechanism and the regioselectivity of the non-polar [3 + 2] cycloaddition reactions between nitrile oxide and two cyclopentenes were theoretically investigated within the molecular electron density theory (MEDT) using DFT methods, namely the B3LYP, MPWB1K and ωB97XD functionals together with the standard 6-31G(d) basis set. The activation energies of these 32CA reactions are relatively high, due to the low nucleophilic power of both cycloalkenes and the relatively moderate electrophilic nature of the nitrile oxide. The B3LYP and MPWB1K functionals reproduced high relative energies values, while the ωB97XD one yields better values in the kinetic and thermodynamic energies.