Chiral N-hydroxybenzamides (1H–3H) have been synthesized as precursors of chiral short-lived N-oxyl radicals 1•–3•. The latter species have been generated by oxidation of 1H–3H with Pb(OAc)4 or hydrogen abstraction from 1H–3H by the tert-butoxyl radical and characterized by UV–vis spectrophotometry and EPR spectroscopy. Through a kinetic study of the hydrogen atom transfer processes promoted by 1•–3• from three chiral benzylic substrates (1-phenylethylamine, 1-phenylethanol, and α-vinylbenzyl alcohol), a moderate chiral discrimination has been found, with selectivity factors 0.5 ≤ kH(S)/kH(R) ≤ 2.
ChiralN-Hydroxybenzamides as Potential Catalysts for Aerobic Asymmetric Oxidations
FRANCHI, PAOLA;LUCARINI, MARCO
2014
Abstract
Chiral N-hydroxybenzamides (1H–3H) have been synthesized as precursors of chiral short-lived N-oxyl radicals 1•–3•. The latter species have been generated by oxidation of 1H–3H with Pb(OAc)4 or hydrogen abstraction from 1H–3H by the tert-butoxyl radical and characterized by UV–vis spectrophotometry and EPR spectroscopy. Through a kinetic study of the hydrogen atom transfer processes promoted by 1•–3• from three chiral benzylic substrates (1-phenylethylamine, 1-phenylethanol, and α-vinylbenzyl alcohol), a moderate chiral discrimination has been found, with selectivity factors 0.5 ≤ kH(S)/kH(R) ≤ 2.File in questo prodotto:
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