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General and Efficient α‐Oxygenation of Carbonyl Compounds by TEMPO Induced by Single‐Electron‐Transfer Oxidation of Their Enolates
Author(s) -
Dinca Emanuela,
Hartmann Philip,
Smrček Jakub,
Dix Ina,
Jones Peter G.,
Jahn Ullrich
Publication year - 2012
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/ejoc.201200736
Subject(s) - chemistry , radical , oxygenation , carbonyl group , electron transfer , bond cleavage , organic chemistry , combinatorial chemistry , catalysis , medicinal chemistry , ecology , biology
A generally applicable method for the synthesis of protected α‐oxygenated carbonyl compounds is reported. It is based on the single‐electron‐transfer oxidation of easily generated enolates to the corresponding α‐carbonyl radicals. Coupling with the stable free radical TEMPO provides α‐(piperidinyloxy) ketones, esters, amides, acids or nitriles in moderate‐to‐excellent yields. Enolate aggregates influence the outcome of the oxygenation reactions significantly. Competitive reactions have been analyzed and conditions for their minimization are presented. Chemoselective reduction of the products led to either N–O bond cleavage to α‐hydroxy carbonyl compounds or reduction of the carbonyl functionality tomonoprotected 1,2‐diols or O ‐protected amino alcohols.