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Iminoxyl Radical‐Based Strategy for Intermolecular CO Bond Formation: Cross‐Dehydrogenative Coupling of 1,3‐Dicarbonyl Compounds with Oximes
Author(s) -
Krylov Igor B.,
Terent'ev Alexander O.,
Timofeev Vladimir P.,
Shelimov Boris N.,
Novikov Roman A.,
Merkulova Valentina M.,
Nikishin Gennady I.
Publication year - 2014
Publication title -
advanced synthesis and catalysis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.541
H-Index - 155
eISSN - 1615-4169
pISSN - 1615-4150
DOI - 10.1002/adsc.201400143
Subject(s) - chemistry , potassium permanganate , manganese , oxidizing agent , radical , permanganate , intermolecular force , oxime , electron paramagnetic resonance , medicinal chemistry , coupling reaction , photochemistry , inorganic chemistry , organic chemistry , molecule , catalysis , physics , nuclear magnetic resonance
Cross‐dehydrogenative CO coupling of 1,3‐diketones and 1,3‐keto esters with oximes was realized for the first time. The reaction proceeds in the presence of the oxidants [KMnO 4 , Mn(OAc) 2 /KMnO 4 , Mn(OAc) 3 ⋅2 H 2 O, MnO 2 , Mn(acac) 3 , Fe(ClO 4 ) 3 , Cu(ClO 4 ) 2 ⋅6 H 2 O, Cu(NO 3 ) 2 ⋅2.5 H 2 O, and (NH 4 ) 2 Ce(NO 3 ) 6 ]. Twenty cross‐coupling products were synthesized using potassium permanganate (KMnO 4 ), manganese(II) acetate dihydrate [Mn(OAc) 3 ⋅2 H 2 O], or the manganese(II) acetate/potassium permanganate [Mn(OAc) 2 /KMnO 4 ] system; yields are 27–92%. The synthesis can be easily scaled up to gram quantities of the target products. Apparently, the reaction proceeds via a radical mechanism in which the oxidizing agent serves to generate radicals from oximes and perform the one‐electron oxidation of 1,3‐dicarbonyl compounds. The formation of oxime radicals was confirmed quantitatively by electron spin resonance (ESR) spectroscopy. The coupling described in the present study is the first example of the selective intermolecular reaction involving unstable iminoxyl radicals generated in situ .