Selective oxidation of benzylic and allylic alcohols with NaOCl/silica gel system

Sodium hypochlorite, a cheap and readily available compound, when supported on silica gel can selectively oxidize benzylic and allylic alcohols to their carbonyl compounds in the presence of catalytic amount of DMSO.     

Efficient ruthenium-catalyzed aerobic oxidation of alcohols using a biomimetic coupled catalytic system

Efficient aerobic oxidation of alcohols was developed via a biomimetic catalytic system. The principle for this aerobic oxidation is reminiscent of biological oxidation of alcohols via the respiratory chain and involves selective electron/proton transfer. A substrate-selective catalyst (ruthenium complex 1) dehydrogenates the alcohol, and the hydrogens abstracted are transferred to an electron-rich quinone (4b). The hydroquinone thus formed is continuously reoxidized by air with the aid of an oxygen-activating Co[bond]salen type complex (6). Most alcohols are oxidized to ketones in high yield and selectivity within 1-2 h, and the catalytic system tolerates a wide range of O(2) concentrations without being deactivated. Compared to other ruthenium-catalyzed aerobic oxidations this new catalytic system has high turnover frequency (TOF).     

Selective photocatalytic oxidation of alcohols by heteropolytungstates

A series of primary, secondary, saturated and unsaturated alcohols have been selectively oxidized photocatalytically to the corresponding aldehydes and ketones by a series of heteropolytungstates using near visible and UV light. Stoichiometrically, one photon adds two electrons onto the heteropolytungstates and produces one molecule of aldehyde or ketone. Using oxygen-saturated solutions, the photocatalytic cycle is obtained at the early stage of the photoredox reaction, with optimization of the quantum yield for the oxidized organic product being ∼ 0.1. After at least 20 photocatalytic cycles, when the production of the organic oxidation product was 20 times the amount of catalyst, there was no sign of decomposition of the catalyst.     

Selective oxidation of alcohols over nickel zirconium phosphate

Nickel zirconium phosphate nanoparticles were found to function as efficient catalysts for the selec-tive oxidation of a wide range of alcohols to their corresponding ketones and aldehydes using H2O2 as an oxidizing agent and without any organic solvents, phase transfer catalysts, or additives. The steric and electronic properties of various substrates had significant influence on the reaction con-ditions required to achieve acetylation. The results showed that this method can be applied for the chemoselective oxidation of benzyl alcohols in the presence of aliphatic alcohols. The catalyst used in the current study was characterized by ICP-OES, XRD, NH3-TPD, Py-FTIR, N2 adsorp-tion-desorption, SEM and TEM. These analyses revealed that the interlayer distance in the catalyst increased from 0.75 to 0.98 nm when Ni2+ was intercalated between the layers, whereas the crystal-linity of the material was reduced. The nanocatalyst could also be recovered and reused at least seven times without any discernible decrease in its catalytic activity. This new method for the oxi-dation of alcohols has several key advantages, including mild and environmentally friendly reaction conditions, short reaction time, excellent yields and a facile work-up.     

Selective oxidation of alcohols over copper zirconium phosphate

The catalytic activity of copper zirconium phosphate (ZPCu) in the selective oxidation of alcohols to their corresponding ketones or aldehydes, using H₂O₂ as an oxidizing agent, was studied. The oxidation reaction was performed without any organic solvent, phase-transfer catalyst, or additive. Steric factors associated with the substrates influenced the reaction. The catalyst was characterized using X-ray diffraction, inductively coupled plasma atomic emission spectroscopy, energy-dispersive X-ray spectroscopy, and scanning electron microscopy. It was shown that the interlayer distance increased from 0.74 to 0.80 nm and the crystallinity was reduced after Cu²⁺ intercalation into the layers. This catalyst can be recovered and reused three times without significant loss of activity and selectivity.     

Selective oxidation of hydroxy groups of phenylthio and phenylseleno alcohols

Various kinds of alcohols bearing phenylthio or phenylseleno moiety were converted into the corresponding carbonyl compounds in good to excellent yields by treating with dimesityl diselenide and $\text{tert}$-butyl hydroperoxide.     

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.     

A novel ruthenium-catalyzed amination of primary and secondary alcohols

An improved method for the N-alkylation of primary amines with primary and secondary alcohols has been developed. Novel, effective catalyst systems, for example, Ru₃(CO)₁₂ combined with tri-o-tolylphosphine or n-butyl-di-1-adamantylphosphine, allow for aminations in a good yield under comparatively mild conditions.     

An unusual ruthenium-catalyzed cycloisomerization of alkynes and propargyl alcohols

CpRu(NCCH3)3+PF6- catalyzes the cycloisomerization of diyne-ols to alpha,beta,gamma,delta-unsaturated aldehydes and ketones in good-to-excellent yields. 1-Hydroxy-2,7-diynes and 1-hydroxy-2,8-diynes can be utilized to form highly functionalized five- and six-membered rings, respectively. Tertiary as well as secondary propargyl alcohols are cycloisomerized to a single isomeric product. A wide variety of tether substitution can be tolerated. Even totally unsubstituted tethers can be employed, as geminal disubstituents are not required for cyclization. Additional hydroxyl substituents at an alternative "internal" propargylic position are eliminated during the reaction-a feature that leads to a convenient cyclopentadiene synthesis. Furthermore, 3-hydroxy-1,6-diynes also can be cyclized to form cross-conjugated aldehydes.     

Selective oxidation of alcohols at the benzylic position by benzeneseleninic anhydride

Benzeneseleninic anhydride in the presence of tert-butyl hydroperoxide in chlorobenzene at about 70 degrees C is an effective oxidizing agent for the selective oxidation of alcohols at the benzylic position.     

Selective oxidation of alcohols by porphyrin-based porous polymer-supported manganese heterogeneous catalysts

A series of porphyrin-based porous polymers to support Mn heterogeneous catalysts (Mn/TFP-DPM, Mn/TFP-DPM-2, Mn/TFP-DPM-3, and Mn/TFP-DPM-4) in the selective oxidation of alcohols were designed. TFP-DPM and TFP-DPM-2 demonstrated micro/nanoscale spherical morphology, whereas TFP-DPM-3 and TFP-DPM-4 exhibited nanosheets structure. According to surface area and porosity analysis results, the specific surface areas of these catalysts were less than 300 m² g^–1. Thermogravimetric analysis indicated that the synthesized catalysts maintain their stability even at 300 °C. Catalysts Mn/TFP-DPM and Mn/TFP-DPM-3, which had the smallest and largest specific surface area among the four catalysts, respectively, were used to perform selective oxidation reaction of alcohols, with experimental results indicating that both have excellent catalytic performance. As these catalysts possess good catalytic performance despite their low specific surface area, we suggest that porphyrin-based porous polymer-supported Mn heterogeneous catalysts are promising materials for selective oxidation of alcohols.     

Condensation of phenols and alcohols with 1,2-dichloroethyl-gem-dichlorocyclopropanes

Dichlorocarbenation of 3,4-dichlorobut-1-ene by Makosza method results in the stereoisomeric 1,2-dichloroethyl-gem-dichlorocyclopropanes in a 1:1 ratio. The reaction of the mixture of stereoisomeric gem-dichlorocyclopropanes with phenols and alcohols in dimethylsulfoxide in the presence of solid sodium hydroxide gives rise to the corresponding ketals containing the exocyclic double and triple bonds. In this case, the acetylene compounds dominate in the reaction products. The ratio of the reaction products containing the double and triple bonds depends on the nucleophile nature.     

Remarkable effect of N-substituent on enantioselective ruthenium-catalyzed propargylation of indoles with propargylic alcohols

Ruthenium-catalyzed enantioselective propargylation of indoles with propargylic alcohols affords the corresponding beta-propargylated indoles in good yields with a high enantioselectivity (up to 95% ee). A remarkable effect of the nature of the N-substituent of indoles is observed for the enantioselectivity of the propargylated indoles. The preparative method described in this paper may provide a novel protocol for asymmetric Friedel-Crafts alkylation of indoles using propargylic alcohols as a new type of electrophiles.     

Selective oxidation of unsaturated alcohols by potassium permanganate adsorbed on solid supports

Potassium permanganate adsorbed on solid supports can be used to oxidize unsaturated secondary alcohols to the corresponding ketones without degradation of the carbon—carbon double bonds.