Regiochemistry and mechanism of oxidation ofN-benzyl-N-alkylhydroxylamines to nitrones
作者:Azfar Hassan、Mohammed I. M. Wazeer、Mohammed T. Saeed、Mohammad N. Siddiqui、Sk. Asrof Ali
DOI:10.1002/1099-1395(200008)13:8<443::aid-poc253>3.0.co;2-9
日期:2000.8
The oxidation of various N-(o-, m-, p-substituted benzyl)-N-alkylhydroxylamines and their dideuteriobenzyl (PhCD2) 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 rho 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 H-1 NMR data. The E = Z isomerization was found to be a bimolecular process. Copyright (C) 2000 John Wiley & Sons, Ltd.