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Regiochemistry and mechanism of oxidation of N ‐benzyl‐ N ‐alkylhydroxylamines to nitrones
Author(s) -
Hassan Azfar,
Wazeer Mohammed I. M.,
Saeed Mohammed T.,
Siddiqui Mohammad N.,
Asrof Ali Sk.
Publication year - 2000
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 - 10.1002/1099-1395(200008)13:8<443::aid-poc253>3.0.co;2-9
Subject(s) - chemistry , isomerization , regioselectivity , hydrogen atom abstraction , conjugated system , nitrone , intermolecular force , photochemistry , medicinal chemistry , stereochemistry , radical , organic chemistry , molecule , catalysis , cycloaddition , polymer
The oxidation of various N ‐( o‐, m‐, p ‐substituted benzyl)‐ N ‐alkylhydroxylamines and their dideuteriobenzyl (PhCD 2 ) counterparts was carried out using mercury(II) oxide and p ‐benzoquinone ( p ‐BQ) as oxidants. An overwhelming preference for the formation of conjugated nitrones is observed in the oxidation of N ‐benzyl‐ N ‐isopropylhydroxylamines. Considerable intra‐ and intermolecular kinetic isotope effects and negative ρ values in the Hammet plots point towards a mechanistic pathway that involves electron transfer from nitrogen to the oxidant followed by hydrogen abstraction. The conformation of unstable ( E )‐nitrones, which readily isomerize to the more stable ( Z )‐nitrones, is deduced from 1 H NMR data. The E ⇌ Z isomerization was found to be a bimolecular process. Copyright © 2000 John Wiley & Sons, Ltd.