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Shedding light on the energetics, regioselectivity, stereoselectivity, and mechanistic aspects of [3 + 2] cycloaddition reaction between azomethine imines and 2‐sulfolene through molecular electron density theory
Author(s) -
Babazadeh Sayyed Mohsen,
Emamian Saeedreza
Publication year - 2020
Publication title -
journal of physical organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.325
H-Index - 66
eISSN - 1099-1395
pISSN - 0894-3230
DOI - 10.1002/poc.4042
Subject(s) - regioselectivity , chemistry , cycloaddition , electrophile , nucleophile , imine , reactivity (psychology) , stereoselectivity , reaction mechanism , density functional theory , heteroatom , nucleophilic addition , stereochemistry , computational chemistry , organic chemistry , ring (chemistry) , catalysis , medicine , alternative medicine , pathology
In the light of Molecular Electron Density Theory (MEDT), [3 + 2] cycloaddition (32CA) reaction between E ‐azomethine imine ( E ‐AI‐2 ) and 2‐sulfolene ( SF‐3 ) was explored at the M06‐2X/6‐31G(d,p) computational level. Calculated global reactivity indices classify E ‐AI‐2 and SF‐3 as, respectively, a strong nucleophile and a moderate electrophile. The generation of cycloadduct CA‐2x , as the sole product, takes place along an irreversible pathway acting as the driving force to proceed such zwitterionic type ( zw ‐type) 32CA reaction. Analysis of the electrophilic and nucleophilic Parr functions, computed at the reactive sites of reactants, rationalizes the entirely N3‐C4 regioselectivity observed experimentally. Moreover, the exo‐stereoselectivity predominance is explained through non‐covalent interactions (NCIs) analysis over the two competitive exo TS‐2x and endo TS‐2n involved in the energetically more preferred regioselective pathway. An exploration of electron localization function (ELF) of the most relevant points located along the intrinsic reaction coordinate (IRC) profile of TS‐2x elucidates the molecular mechanism of the studied [3 + 2] cycloaddition reaction. Indeed, this reaction follows a nonconcerted two‐stage one‐step molecular mechanism providing two different patterns regarding carbon‐carbon (C–C) and carbon‐heteroatom (C–N) single bonds formation.