학술논문
Unveiling the mechanism, selectivity, solvent and temperature effects on the [3 + 2] cycloaddition reaction of N-methyl-C-(2-furyl) nitrone with maleimide derivatives from the molecular electron density theory perspective.
Document Type
Article
Author
Source
Subject
*ELECTRON density
*KINETIC control
*TEMPERATURE effect
*SOLVENTS
*ACTIVATION energy
*RING formation (Chemistry)
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Language
ISSN
1432-881X
Abstract
The [3 + 2] cycloaddition (32CA) reactions of N-methyl-C-(2-furyl) nitrone with maleimide derivatives have been studied in gas phase, ethanol and acetonitrile within the Molecular Electron Density Theory (MEDT) framework at the B3LYP-D3/6-31G(d) level. Topological analysis allows classifying the nitrone as a zwitterionic (zw-) three-atom component (TAC) associated with high energy barrier. Interestingly, the global electron density transfer (GEDT) between 0.10 and 0.13 e predicts low polar character of forward electron density transfer (FEDF) type with the electronic flux from the nitrone to the maleimides, resulting in decreased activation parameters relative to that of the nitrone cycloadditions with simple alkenes. These 32CA reactions follow a one-step mechanism under kinetic control with highly asynchronous bond formation, and no new covalent bonds are formed at the TSs. The predicted exo-selectivity agrees well with the experimental findings. Inclusion of solvent effects increases the activation energy, in particular along the endo pathway. The activation enthalpies are between 5.58 and 7.68 kcal/mol in gas phase and between 6.61 and 11.10 kcal/mol in ethanol and acetonitrile. Also, the influence of temperature was investigated at 289.15 K, 298.15 K and 393.15 K. Non-covalent interactions (NCIs) were identified at the interactions regions of the TSs from the topological analysis of the AIM (atoms-in-molecules) and characterized using Independent Gradient Model (IGM) analysis. [ABSTRACT FROM AUTHOR]