Abstract
The [3+2] cycloaddition (32CA) reactions of diphenyl nitrilimine and phenyl nitrile oxide with (R)-carvone have been studied within the Molecular Electron Density Theory (MEDT). Electron localisation function (ELF) analysis of these three-atom-components (TACs) permits its characterisation as carbenoid and zwitterionic TACs, thus having a different reactivity. The analysis of the conceptual Density Functional Theory (DFT) indices accounts for the very low polar character of these 32CA reactions, while analysis of the DFT energies accounts for the opposite chemoselectivity experimentally observed. Topological analysis of the ELF along the single bond formation makes it possible to characterise the mechanisms of these 32CA reactions as cb- and zw-type. The present MEDT study supports the proposed classification of 32CA reactions into pdr-, pmr-, cb- and zw-type, thus asserting MEDT as the theory able to explain chemical reactivity in Organic Chemistry.
Highlights
IntroductionAit Itto et al reported the 32CA reactions of (R)-carvone 1 with diaryl nitrilimines (NIs) 2a–d and arylnitrile oxides (NOs) 4a–d in dichloromethane (DCM), yielding pyrazoles 3a–d and isoxazoles 5a–r, respectively (see Scheme 1) [16]
In order to characterise the electronic structure of diphenyl-NI 2a and phenyl NO 4a and, establish their reactivity in 32CA reactions [21], a topological analysis of the Electron localisation function (ELF) [25] of these TACs was to establish their reactivity in 32CA reactions [21], a topological analysis of the ELF [25] of these TACs first performed; the electronic structure of (R)-carvone 1 is analysed
The topological analysis of the ELF of diaryl NI 2a and aryl NO 4a allows characterising their electronic structure as carbenoid and zwitterionic TACs, respectively
Summary
Ait Itto et al reported the 32CA reactions of (R)-carvone 1 with diaryl nitrilimines (NIs) 2a–d and arylnitrile oxides (NOs) 4a–d in dichloromethane (DCM), yielding pyrazoles 3a–d and isoxazoles 5a–r, respectively (see Scheme 1) [16]. These 32CA reactions presented total regioand chemoselectivity, resulting in a mixture of a pair of diastereoisomers resulting from the attack of Molecules 2020, 25, 1085; doi:10.3390/molecules25051085 www.mdpi.com/journal/molecules. Molecules 2020, 25, 1085 isoxazoles 5a–r, respectively (see Scheme 1) [16] These 32CA reactions presented total regio- and chemoselectivity, resulting in a mixture of a pair of diastereoisomers resulting from the attack of these these TACs the faces two faces of the.
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