Resumen

MOHAMMED SALIH, Sabir A.; BASHEER, Huda A.  y  MOHAMMAD-SALIM, Haydar A.. Unveiling [3 + 2] Cycloaddition Reactions of N-Methyl-C-3-Bromophenyl-Nitrone to Dimethyl Maleate: Molecular Electron Density Theory Perspective. J. Mex. Chem. Soc [online]. 2022, vol.66, n.4, pp.560-574.  Epub 10-Abr-2023. ISSN 1870-249X.  https://doi.org/10.29356/jmcs.v66i4.1801.

The zwitterionic-type (zw-type) [3+2] cycloaddition (32CA) reactions of N-methyl-C-3-bromophenyl-nitrone 1 with dimethyl maleate 2 with increased electrophilicity were investigated using the Molecular Electron Density Theory (MEDT) at the MPWB95/6-311++G(d,p) computational level. Both reactivity and selectivity are rationalized in relation to the polarity of the reaction. The associated zw-type 32CA reactions are accelerated due to the high nucleophilic character of N-methyl-C-3-bromophenyl-nitrone 1 and the strong electrophilic character of dimethyl maleate 2, which also play a critical part in the mechanism of the reaction, influencing the stereoselectivity, with activation enthalpies in between 34.04 and 38.37 kJ.mol-1 in the gas phase. The CDFT indices are used to anticipate global electron density flux from the nucleophilic N-methyl-C-3-bromophenyl-nitrone 1 to the electrophilic dimethyl maleate 2. These exergonic 32CA reactions have negative Gibbs free energy along the endo and exo stereochemical pathways. The endo stereochemical process is preferred over the exo stereochemical pathway in this kinetically controlled 32CA reaction. The predictions of bonding evolution theory (BET) for the endo and exo pathways indicate a one-step process with early transition states, which is compatible with the ELF topological examination of transition states.

Palabras llave : Molecular electron density theory; nitrone; [3+2]; cycloaddition reactions; electron localization function.