A Molecular Electron Density Theory Study of 3+2 Cycloaddition Reaction between Azomethine Ylides and Electron-Deficient Nitroalkenes

摘要

abstract_textpThe 3+2 cycloaddition (32CA) reaction of an azomethine ylide namely (S,E)-3-benzylidene-2-(tert-butyl)-1-methyl-5-oxoimidazolidin-3-ium-4-ide, AZY6, toward a highly electron-deficient ethylene derivative namely (E)-(2-nitrovinyl)benzene, NVB7, was theoretically studied at the B3LYP/6-31G(d) computational level. This 32CA reaction takes place with a total regio- and stereoselectivity, and with a very low activation enthalpy, 4.2kcal/mol, as a consequence of high pseudodiradical character of AZY6. Analysis of the conceptual density functional theory (DFT) reactivity indices allows explaining the high reactivity of AZY6 and NVB7, as well as the total regioselectivity experimentally observed. Both analyses of the molecular electrostatic potential (MEP) maps as well as non-covalent interactions (NCIs) allow explaining the endo stereoselectivity. An electron localization function (ELF) topological analysis of selected points along the most favorable reactive channels allows establishing the non-concerted two-stage one-step molecular mechanism./p/abstract_text