Push-pull nitronates in the [3+2] cycloaddition with nitroethylene: Molecular Electron Density Theory study.

The structure and the participation of the N-methoxy-N-[bis(methoxycarbonyl)methylene]amine N-oxide as model push-pull nitronate 1 with nitroethylene 2 in [3 + 2] cycloaddition (32CA) reaction have been analyzed within the Molecular Electron Density Theory (MEDT) using Density Functional Theory (DFT) calculations at the B3LYP(PCM)/6-31G(d) level. Topological analysis of the Electron Localization Function (ELF) of nitronate 1 reveals that this compound has pseudoradical center, while the conceptual DFT reactivity indices characterizes this three-atom-component (TAC) as a strong electrophile. The analyzed 32CA reaction takes place through a one-step mechanism. A Bonding Evolution Theory (BET) study of the more favorable reaction path associated with the 32CA reaction of nitronate 1 with nitroethylene 2 indicates that it is associated with a non-concerted two-stage one-step mechanism, in which the activation energy is mainly related with to the initial formation of the O3-C4 single bond. In the case of this reaction, an additional mechanism with formation of intermediate 7 is also found.