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Chemically triggered C–ON bond homolysis in alkoxyamines. Part 7. Remote polar effect
Author(s) -
Audran Gérard,
Ibanou Matisse Bim Batsiandzy,
Brémond Paul,
Marque Sylvain R. A.,
Obame Germain,
Roubaud Valérie,
Siri Didier
Publication year - 2014
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.3275
Subject(s) - chemistry , natural bond orbital , homolysis , reactivity (psychology) , methylene , computational chemistry , phosphonate , medicinal chemistry , stereochemistry , mulliken population analysis , radical , organic chemistry , density functional theory , medicine , alternative medicine , pathology
In a recent work ( Org . Lett . 2012, 14 , 358–361), we showed that the activation by benzylation of alkoxyamine 1 (diethyl (1‐( tert ‐butyl(1‐(pyridin‐4‐yl)ethoxy)amino)‐2,2‐dimethylpropyl)phosphonate) afforded a surprisingly large C–ON bond homolysis rate constant k d . Taking advantage of the easy preparation of para ‐X‐benzyl‐activated alkoxyamines 2 and of the presence of a shielding methylene group between the two aromatic moieties, we investigated the long range (10 bonds between the X group and the C–ON bond) polar effect for X = H, F, OMe, CN, NO 2 , NMe 2 , + NHMe 2 ,Br − . It was observed that the effect was weak (4‐fold) and mainly due to the zwiterionic mesomeric forms generated by the presence of group X on the para position, i.e. k d increased for CN and NO 2 and decreased for OMe, NMe 2 and + NMe 2 H,Br − . DFT calculations at the B3LYP/6‐31G(d,p) level were performed to determine orbital interactions (natural bond orbital (NBO) analysis), Mulliken and NBO charges which support the reactivity described. Copyright © 2014 John Wiley & Sons, Ltd.