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

Abstract

The oxidation of alcohols to aldehydes and ketones by air or oxygen under mild conditions (room temperature and atmospheric pressure), catalysed by persistent and non-persistent nitroxyl radicals in combination with transition metal salts, appears to be the most convenient of the numerous processes developed for these purposes. The thermochemistry, the kinetics, and the Hammett correlations have allowed us to establish, on a quantitative basis, the fundamental difference

Immobilization of Organic Catalysts: When, Why, and How

“…[4,26] The benefecial effect of the spacer was also demonstrated in a subsequent work [27] where pre-catalysts 1 and 2c (1-5 mol %) were employed for the oxidation of primary and secondary alcohols using oxygen as the terminal oxidant in the presence of 2 mol % of CoA C H T U N G T R E N N U N G (NO 3 ) 2 hydrate and MnA C H T U N G T R E N N U N G (NO 3 ) 2 hydrate as co-catalyst. [28] For instance, under these conditions oxidation of 1-octanol and cyclooctanol [Scheme 1, Eqs. (1) and (2)] occurred in quantitative yield with 1 and in only about 65 % yield with 2c.…”

A Complexation Promoted Organic N‐Hydroxy Catalytic System for Selective Oxidation of Toluene

“…It was reported that cobalt or manganese salts, CuCl, and Fe/MgO were effective co-catalysts for NHPI. [12] Among the tested metal salts in the present work, however, besides cobalt acetate, copper salts showed considerable activity for the oxidation of toluene (entries 1, 7-9, Table 2). And especially when CuCl 2 was combined with HPPDO, the best activity was obtained with 70.9% conversion of toluene and 93.5% selectivity for benzoic acid (Entry 9).…”

Hydrogen abstraction from H‐donor substrates by the 6‐CF3‐benzotriazol‐N‐oxyl radical (TFNO)

“…[18] [24] Therefore, a higher HAT reactivity for weaker bonds can be inferred, a result consistent with analogous findings for PINO and BTNO. [14,16,17] Summing it up, the reactivity features of TFNO in the HAT process (Table 2) are akin to those of other aminoxyl radicals, [10] including the finding of an accelerating effect from electron-donor and the retarding effect from electron-withdrawing substituents on the benzylic substrate. Significant figures for this comparison of reactivity among aminoxyl radicals are selected and given in Table 3, proper allowance being made to the different solvents employed (no major effects upon the rates are however expected in these radical processes [14,15,25] ).…”

“…1), and the synthetic value of PINO-induced oxidations is recognised and has prompted studies upon the reactivity features of the aminoxyl radical intermediates. [9,10,12,13] Kinetic surveys have been already performed with PINO or else with its X-aryl-substituted cognates, [13][14][15][16][17] and have been recently complemented by a kinetic investigation with another aminoxyl radical, that is benzotriazole N-oxyl (BTNO), [18] originating from precursor 1-hydroxybenzotriazole (HBT). [19] Another kinetic study had been reported with bis(trifluoromethyl)aminoxyl radical, [20] (CF 3 ) 2 N-O .…”