Understanding the Regioselectivity and the Molecular Mechanism of [3 + 2] Cycloaddition Reactions between Nitrous Oxide and Conjugated Nitroalkenes: A DFT Computational Study.

Regiochemical aspects and the molecular mechanism of the [3 + 2] cycloaddition between nitrous oxide and conjugated nitroalkenes were evaluated on the basis of the wb97xd/6-311 + G(d) (PCM) computational study. It was found that, independently of the nature of the nitroalkene, all considered processes are realized via polar, single-step mechanisms. All attempts at the localization of hypothetical zwitterionic intermediates were unsuccessful. Additionally, the DFT computational study suggested that, in the course of the reaction, the formation of respective Δ-4-nitro-4-R-5-R-1-oxa-2,3-diazolines was preferred from the kinetic point of view.