6533b858fe1ef96bd12b5837

RESEARCH PRODUCT

Understanding the molecular mechanism of the [3 + 2] cycloaddition reaction of benzonitrile oxide toward electron-richN-vinylpyrrole: a DFT study

subject

description

The [3 + 2] cycloaddition (32CA) reaction of benzonitrile oxide, BNO 2, with an electron-rich N-vinylpyrrole derivative, NVP 3a, in the presence of dichloromethane, has been theoretically studied using density functional theory (DFT) methods at the B3LYP/6-31G(d) level. This 32CA reaction presents a relatively high activation Gibbs free energy as a result of the low polar character of this zwitterionic-type (zw-type) reaction. Analyses of the calculated relative Gibbs free energies and transition state geometries indicate that the studied 32CA reaction, in excellent agreement with experimental outcomes, takes place in a complete regioselective manner as a consequence of the steric repulsions that appear at the most unfavorable transition state. An electron localization function (ELF) topological analysis of the bonding changes along this 32CA reaction supports a non-concerted two-stage one-step molecular mechanism in which the formation of the O3-C5 single bond takes place at the end of the reaction after the complete formation of the C1-C4 one. Copyright © 2016 John Wiley & Sons, Ltd.