Regiochemical Reversals in Nitrosobenzene Reactions with Carbonyl Compounds: α-Aminooxyketone versus
Donna J Nelson1, Ravi Kumar, Shagufta
1Department of Chemistry and Biochemistry, University of Oklahoma, Norman, OK 73019, USA.
Abstract:
The Lewis acid-catalyzed reaction of nitrosobenzene with a ketone can produce an α-aminooxyketones or an α-hydroxyaminoketone, with reaction regiochemistry switching from the latter to the former, dependent upon the addition of Lewis acid or sterically-hindered solvent. While the latter (C-N bond formation) is easily explained by attack of the enolate α-carbon at N, the former (C-O bond formation) has been an enigma, with few proposed explanations, and none which explain simultaneously formation of both products and all the regiochemical reversals. Herein, the regiochemistry reversal is proposed to occur via (1) nucleophile formation governed by Hard and Soft Acids and Bases (HSAB) theory, (2) a nucleophilic attack by the enolate O at N, followed by (3) a [2,3]-sigmatropic rearrangement. This mechanistic pathway and HSAB considerations account for formation of both products and explain the three reported regiochemistry reversals, which are observed upon the introduction of (A) Lewis acid catalyst, (B) AcOH, or (C) solvent bulkiness.
Related Concept Videos
Nitrosation of Enols
Preparation of Amines: Reduction of Oximes and Nitro Compounds
Though catalytic hydrogenation can reduce nitrobenzenes, the reduction is nonselective in the presence of other functional groups. For instance, if nitrobenzene contains an aldehyde group,...
Preparation of Amines: Reductive Amination of Aldehydes and Ketones
α-Hydroxy Ketones via Reductive Coupling of Esters: Acyloin Condensation Overview
meta-Directing Deactivators: –NO2, –CN, –CHO, –⁠CO2R, –COR, –CO2H
Ketones with Nonenolizable Aromatic Aldehydes: Claisen–Schmidt Condensation
As the self-condensation of ketones is generally not favored in basic conditions, the self-condensed products do not form in the reaction between ketones and benzaldehyde. The general reaction of Claisen–Schmidt condensation is...


