This review presents the current state of knowledge on the (3+2) cycloaddition (32CA) reactions involving heteroarene N-oxides. While aromatic amine oxides behave similarly to nitrones, their participation in cycloaddition processes is chemically distinct due to the thermodynamic stability of the aromatic ring system. The manuscript critically examines these reactions, focusing on the competition between the formation of stable fused isoxazolidines and the tendency toward rearomatization. The latter often leads to spontaneous ring opening, elimination, or complex rearrangements rather than the isolation of the primary cycloadduct.

The usefulness of various quantum chemical algorithms (semiempirical, HF, DFT) for predicting the energy and geometry of transition states of polar pseudocyclic processes was analyzed using the example of a model cycloaddition process between (Z)-C,N-diphenylnitrone and (E)-2-phenyl-1-nitroethene. These studies clearly recommend the ωB97XD functional in 6-311+G(d) basis set as the relatively most precise tool for studying the mechanisms of polar pseudocyclic processes.

The correlation between coefficients from Dimroth equations and descriptors of global electron density transfer was explored based on the data available in the recent literature. We established that the obtained results should be very usable for the interpretation of the organic reactivity and molecular mechanisms.