Ru(PPh3)(OH)-salen complex: a designer catalyst for chemoselective aerobic oxidation of primary alcohols

Based on the analysis of the mechanism of aerobic oxidation of alcohols using Ru(NO)-salen catalyst, we designed a new complex, Ru(PPh₃)(OH)-salen 3, which was proved to be an excellent catalyst for chemoselective aerobic oxidation of primary alcohols to the aldehydes in the presence of secondary alcohols under ambient and non-irradiated conditions. Complex 3 was also successfully applied to the oxidation of 1-phenyl-1,n-diols to the lactols or the n-hydroxy aldehyde. It is of note that selective oxidation of primary alcohols was achieved even in the presence of activated secondary alcohols.     

Catalytic Oxidation of Alcohols to Corresponding Aldehydes or Ketones with TEMPO-Mediated Iodosobenzene in Water in the Presence of a Surfactant

An efficient, facile, and rapid oxidation of alcohols to the corresponding aldehydes or ketones with a stoichiometric amount of iodosobenzene (PhIO) in the presence of catalytic amounts of 2,2,6,6-tetramethyl-1-piperidinyloxyl free radical (TEMPO), KBr, and a surfactant, such as SDS (sodium dodecylsulfate), was reported. The oxidation proceeded in water at room temperature to afford aldehydes or ketones in excellent yields and high selectivity without overoxidation to carboxylic acids. Selective oxidation of primary alcohols in the presence of secondary alcohols was also achieved with the catalytic system of PhIO/TEMPO/KBr/SDS. A possible mechanism for the oxidation was supposed.     

A new polymer-attached reagent for the oxidation of primary and secondary alcohols

A new, polymer-bound reagent system for the efficient oxidation of primary alcohols to aldehydes and secondary alcohols to ketones in the presence of a catalytic amount of 2,2,6, 6-tetramethyl-1-piperidinyloxyl (TEMPO) is described. In most cases, workup of this heavy metal-free oxidation is achieved by simple filtration followed by removal of the solvent. In selected examples this reagent was compared with the known polymer-bound permanganate and chromium(VI) reagents.     

Kinetic resolution of racemic secondary alcohols catalyzed by chiral diaminodiphosphine-Ir(I) complexes

Chiral diaminodiphosphine-Ir(I) complexes were found to efficiently catalyze enantioselective oxidation of racemic secondary alcohols in acetone. In the presence of base, oxidative kinetic resolution of the alcohols proceeded smoothly with excellent enantioselectivity (up to 98% ee) under mild conditions. [reaction: see text].     

Photochemical Transformations with Iodine Azide after Release from an Ion‐Exchange Resin

This report discloses the photochemical homolytic cleavage of iodine azide after its formation following release from polymer‐bound bisazido iodate(I) anions. A series of radical reactions are reported including the 1,2‐functionlization of alkenes and the unprecedented chemoselective oxidation of secondary alcohols in the presence of primary alcohols.     

Synthetic scope of alcohol transfer dehydrogenation catalyzed by Cu/Al2O3: a new metallic catalyst with unusual selectivity

A method for the anaerobic oxidation of a wide series of alcohols including cyclohexanols and steroidal alcohols, has been set up. It relies on a transfer dehydrogenation reaction from the substrate alcohol to styrene catalyzed by a heterogeneous, reusable copper catalyst under very mild liquid-phase experimental conditions (90 degrees C, N(2)) and shows unusual selectivity. Thus, the method is selective for the oxidation of secondary and allylic alcohols even in the presence of unprotected primary and benzylic alcohols. Electronic effects and the choice of the hydrogen acceptor account for the selectivity observed.     

New efficient aerobic oxidation of some alcohols with dioxygen catalysed by N-hydroxyphtalimide with vanadium co-catalysts

New efficient vanadium co-catalysts have been developed for the oxidation of some alcohols with O(2) catalysed by N-hydroxyphthalimide (NHPI). Various alcohols (primary and secondary) were selectively oxidized by O(2) under mild conditions in the presence of a catalytic amount of NHPI as a radical-producing agent combined with small amounts of vanadium complexes with or without the addition of a simple salt (e.g. LiCl) or base (e.g. pyridine).     

Selective aerobic oxidation of allylic and benzylic alcohols catalyzed by N-hydroxyindole and copper(I) chloride

In the presence of copper(I) chloride, tert-butyl 1-hydroxy-2-methyl-6-trifluoromethyl-1H-indole-3-carboxylate acted as a catalyst for the chemoselective aerobic oxidation of allylic and benzylic alcohols. A variety of primary and secondary allylic and benzylic alcohols were oxidized into the corresponding α,β-unsaturated carbonyl compounds in good yields without affecting non-allylic alcohols.     

Aerobic oxidation of primary alcohols in the presence of activated secondary alcohols

Chemoselective aerobic oxidation of primary alcohols in the presence of activated secondary alcohols was effected under irradiation of visible light by using (nitrosyl)Ru(salen) complex 6 that possesses bulky 1-ethyl-1-methylpropyl groups at C3, C3′, C5 and C5′, as catalyst. For example, oxidation of n-decanol was >50 times faster than oxidation of 1-phenylethanol at 10 °C.     

Oxidation reaction of steroid alcohols by ruthenium tetroxide

Oxidation of steroid alcohols by ruthenium tetroxide gives corresponding ketones in almost quantitative yields. The reaction provides a simple and convenient procedure for converting secondary alcohols to ketones in neutral media. The reconversion of ruthenium dioxide, produced during the oxidation, into the tetroxide with an appropriate oxygen donor such as sodium metaperiodate makes possible the oxidation of a given steroid alcohol to a ketone in the presence of a catalytic amount of ruthenium tetroxide.     

Efficient selective oxidation of alcohols to aldehydes catalyzed by a morpholinone nitroxide

Efficient chemoselective oxidation of primary alcohols to the corresponding aldehydes is described. The transformation is promoted by a catalytic morpholinone nitroxide radical catalyst which can be easily synthesized. A broad range of substrates including aromatic and aliphatic primary alcohols are converted with excellent yields under mild conditions. The control experiments reveal that the morpholinone nitroxide can be used as a selective oxidant for primary alcohols in the presence of secondary alcohols.     

Enantioselective oxidation of racemic secondary alcohols catalyzed by chiral Mn(III)-salen complexes with N-bromosuccinimide as a powerful oxidant

We demonstrate an efficient enantioselective oxidation of secondary alcohols catalyzed by Mn(III)-salen complex using N-bromosuccinimide (NBS) as the oxidant. The new protocol is very efficient for the oxidative kinetic resolution of a variety of secondary alcohols, including ortho-substituted benzylic alcohols.     

A reasonable explanation for the mechanism of photo-promoted chemoselective aerobic oxidation of alcohols using (ON)Ru(salen) complex as catalyst

The mechanism of aerobic oxidation of alcohols using (ON)Ru(salen) complex as catalyst under photo-irradiation was examined through studies of kinetics of the oxidation, kinetic isotope effect in the oxidation, and effect of the ligand structure on the chemoselectivity of the oxidation of primary and secondary alcohols. It was demonstrated that the aerobic oxidation includes an intramolecular hydrogen atom transfer process that is attributed to realization of efficient differentiation of primary and secondary alcohols in the oxidation.     

A new cr(VI) reagent for the catalytic oxidation of secondary alcohols to ketones

A new process is described for the oxidation of secondary alcohols to ketones using peroxyacetic acid in the presence of a catalytic amount of 2,4-dimethylpentane-2, 4-diol cyclic chromate.     

Efficient oxidation of secondary alcohols to Ketones by NaOCl catalyzed by Salen-Mn(III)/NBS

An efficient catalytic system salen-Mn(III)/NBS for oxidation of secondary alcohols to ketones by inexpensive and readily available oxidizing agent NaOCl has been developed. The process resulted in good to excellent yields under the action of 2 mol % of salen-Mn(III) and 13 mol % of NBS at room temperature. However, such system was not efficient in oxidation of secondary benzyl alcohols with a strong electronicdonating substituent attached to the benzene ring due to bromination of the alcohols.     

Catalytic oxidation of alcohols with allyl diethyl phosphate and palladium acetate

Allyl diethyl phosphate (ADP) was found to function as a stoichiometric hydrogen acceptor in a catalytic oxidation reaction of alcohols with Pd(OAc)₂. A variety of acyclic primary and secondary alcohols were oxidized in good yields and under mild conditions to the corresponding aldehydes and ketones, in the presence of Na₂CO₃ or K₂CO₃. Simple aliphatic primary alcohols yielded esters, exclusively. Polar ligand solvents (DMF, DMSO) were found to accelerate the reaction. Slow, but high yield reactions were encountered in THF and acetonitrile as solvents. The reactivity of several other allyl systems serving as H-acceptors, and several Pd compounds serving as catalysts, in the above oxidation reaction, was evaluated. It has been experimentally demonstrated (H-NMR) that ADP is capable of generating a π-allyl-Pd complex using a Pd(0) complex. Consequently, a catalytic cycle was proposed for the above oxidation reaction.     

In situ generation of o-iodoxybenzoic acid (IBX) and the catalytic use of it in oxidation reactions in the presence of Oxone as a co-oxidant

[structure: see text] Catalytic use of o-iodoxybenzoic acid (IBX) in the presence of Oxone as a co-oxidant is demonstrated for the oxidation of primary and secondary alcohols in user- and eco-friendly solvent mixtures. Also demonstrated is the in situ (re)oxidation of 2-iodosobenzoic acid (IBA) and even commercially available 2-iodobenzoic acid (2IBAcid) by Oxone to IBX allowing one to use these less hazardous reagents, in place of potentially explosive IBX, as catalytic oxidants.     

Mechanistic investigations of the iridium(III)-catalyzed aerobic oxidation of primary and secondary alcohols

The commercially available catalysts [(Cp*IrCl2)2] is employed with O2 as the terminal oxidant in the presence of catalytic amounts of Et3N for the aerobic oxidation of primary and secondary alcohols. A new mechanism for the Ir-catalyzed aerobic oxidation is also presented that suggests that the transition metal maintains its +3 oxidation state throughout the entire catalytic cycle.     

Lewis base catalysis by thiourea: N-bromosuccinimide-mediated oxidation of alcohols

In recent times, (thio)urea derivatives have become synonymous with hydrogen bonding owing to their extensive applicability as small molecule organocatalysts. In this paper, another activation mode by thiourea derivatives, namely via Lewis base catalysis, is disclosed for the NBS-mediated oxidation of alcohols. The mild reaction conditions employed here is suitable for chemoselective oxidation of secondary alcohol in the presence of primary alcohol.     

The Mn(acac)3—RCN—CCl4 system as a new efficient reagent for the oxidation of secondary alcohols into ketones

The Mn(acac)₃—RCN—CCl₄ system was found to be efficient for the oxidation of secondary alcohols into the corresponding ketones in 80—93% yields. The oxidation proceeds through the formation of alkyl hypochlorites, which are generated from CCl₄ and the alcohols in the presence of the Mn(acac)₃—RCN catalytic system (R = Me, Et, and Ph).