Radical versus “Oxenoid” Oxygen Insertion Mechanism in the Oxidation of Alkanes and Alcohols by Aromatic Peracids. New Synthetic Developments

Abstract

Evidences concerning a novel free-radical mechanism for the oxidation of alkanes by aromatic peracids are reported. The mechanism involves hydrogen abstraction from the OH group of peracids by an aroyloxyl radical; the acylperoxyl radical thus generated is responsible for the selective oxidation. The reaction is affected by the presence of oxygen and it is inhibited by TEMPO and by solvents forming hydrogen bonds with peracids. A more simple and effective synthetic procedure has been developed, on the basis of the autoxidation of aliphatic and aromatic aldehydes in the presence of alkanes. It is also shown that the previously reported inertness of alcohols toward peracids must be ascribed to solvent effects, due to the formation of hydrogen bonds; in suitable solvents alcohol oxidation smoothly occurs.

Mechanisms of the aerobic oxidations catalyzed by N-hydroxyderivatives

“…(4)): (26) Nitroxyl radicals are generally electrophilic, but this polar character is considerably enhanced by the presence of two carbonyl groups (Eq. (27)): (27) The effect is similar to those observed with acylperoxyl, RC( O)OO • , and acyloxyl, RC( O)O • radicals compared to peroxyl, ROO • , and alkoxyl, RO • , radicals; the former are more electrophilic than the latter [25]. The phenomenon is more marked with PINO than with acylperoxyl and acyloxyl radicals because the nitrogen atom can stabilize a positive charge, as in Eq.…”

Functionalized Nanodiamonds Part I. An Experimental Assessment of Diamantane and Computational Predictions for Higher Diamondoids

“…Other types of reagents that play an important role in alkane chemistry are peroxo species like dioxiranes, [52] peracids, [53] as well as metal-oxo compounds. [54] The CÀH activations with peracids and dioxiranes are believed to occur through concerted insertions, [55] that is, they are mechanistically different from radical abstractions.…”

Mechanisms of the Aerobic Oxidation of Alcohols to Aldehydes and Ketones, Catalysed under Mild Conditions by Persistent and Non‐Persistent Nitroxyl Radicals and Transition Metal Salts − Polar, Enthalpic, and Captodative Effects

“…(18) The effects are similar to those observed with acyl peroxyl, RC(ϭO)OO · , and acyloxyl, RC(ϭO)O · , radicals when compared to alkyl peroxyl, ROO · , and alkoxyl, RO · , radicals; the former are more electrophilic than the latter. [23] The phenomenon is more marked with PINO than with acylperoxyl and acyloxyl radicals because the nitrogen atom can stabilise a positive charge, as in Equation (18), better than carbon or oxygen atoms.…”