Enolate-Based Regioselective Anti-Beckmann C-C Bond Cleavage of Ketones
The Baeyer-Villiger or Beckmann rearrangements are established methods for the cleavage of ketone derivatives under acidic conditions, proceeding for unsymmetrical precursors selectively at the more substituted site. However, the fragmentation regioselectivity cannot be switched and fragmentation at the less-substituted terminus is so far not possible. We report here that the reaction of ketone enolates with commercial alkyl nitrites provides a direct and regioselective way of fragmenting ketones into esters and oximes or ω-hydroxyimino esters, respectively. A comprehensive study of the scope of this reaction with respect to ketone classes and alkyl nitrites is presented. Control over the site of cleavage is gained through regioselective enolate formation by various bases. Oxidation of kinetic enolates of unsymmetrical ketones leads to the otherwise unavailable "anti-Beckmann"cleavage at the less-substituted side chain, while cleavage of thermodynamic enolates of the same ketones represents an alternative to the Baeyer-Villiger oxidation or the Beckmann rearrangement under basic conditions. The method is suited for the transformation of natural products and enables access to orthogonally reactive dicarbonyl compounds.
Ma?ek, Tomá?,Jahn, Ullrich
p. 11608 - 11632
(2021/09/02)
Metal nitrite: A powerful oxidizing reagent
An efficient and simple source of nitroso reagents and their oxidation reactions are described. The combination of a Lewis acid and a metal nitrite was applied to the oxidation of silyl enol ethers. Amino acid and peptide derivatives were easily accessed through in situ C-C bond cleavage of fully substituted silyl enol ethers upon oxidation.
Baidya, Mahiuddin,Yamamoto, Hisashi
p. 13880 - 13882
(2011/10/09)
A remarkably simple α-oximation of ketones to 1,2-dione monooximes using the chlorotrimethylsilane-isoamyl nitrite combination
Ketones undergo α-oximation by NOCl formed in situ from Me3SiCl and isoamyl nitrite, either in solution or under solvent-free conditions, to produce 1,2-dione monooximes in excellent yields. The oximation is regiospecific in appropriate cases.
Mohammed, Abdulkarim H.A.,Nagendrappa, Gopalpur
p. 2753 - 2755
(2007/10/03)
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