Water-soluble N-oxyl compounds-mediated electrooxidation of alcohols in water: a prominent access to a totally closed system

Electrooxidation of alcohols in water involving water-soluble N-oxyl compounds (WS-TEMPOs) proceeded smoothly to afford the corresponding ketones and aldehydes in good yields. Notably, most of WS-TEMPOs in water remained intact after the electrolysis. The aqueous solution containing WS-TEMPOs was recovered easily and repeatedly used for the electrooxidation of alcohols, offering a totally closed system.     

Electrooxidation of alcohols in an N-oxyl-immobilized rigid network polymer particles/water disperse system

The electrooxidation of alcohols in an aqueous disperse system with N-oxyl-immobilized poly(p-phenylene benzobisthiazole) network polymer particles (PBZT_NT-N-Oxyl) as a disperse phase was performed successfully in a simple beaker-type undivided cell under a constant current condition to afford the corresponding ketones, aldehydes, and/or carboxylic acid in moderate to good yields. Recycle use of both the PBZT_NT-N-Oxyl particles and the aqueous media could be achieved successfully by immobilization of additional N-oxyl moiety on the polymer particles in an appropriate interval. Notably, the shape and the particle size of PBZT_NT-N-Oxyl were not appreciably changed even after 60 times recycle use.     

Fast oxidation of secondary alcohols by the bromate-bromide system using cyclic microwave heating in acidic water

We report an improved, gentle, cyclic microwave activation technique for the oxidation of secondary alcohols using nonhazardous hypobromous acid (BrOH) as the reagent in acidic water. Several aliphatic and aromatic secondary alcohols were successfully oxidized to the corresponding ketones using this technique in high yields and with only minor amounts of side products.     

Silver(I)-promoted intramolecular addition of N-heterocyclic carbenes towards unsaturated esters in water

Silver(I)-promoted intramolecular addition reaction between N-heterocyclic carbene and unsaturated esters in water is described. The reaction leads to 1H-imidazo[1,2-a]indole derivatives in moderate to excellent yields.     

Comparison of TEMPO and its derivatives as mediators in laccase catalysed oxidation of alcohols

A series of TEMPO (2,2′,6,6′-tetramethylpiperidinyl-1-oxy) derivatives were studied as mediators of laccase (from Trametes versicolor) in the oxidation of benzyl alcohol and 1-phenylethyl alcohol. TEMPO (1), 4-hydroxy-TEMPO (2) and 4-acetylamino-TEMPO (4) turned out to be the most active mediators for laccase. In addition, 4-acetylamino-TEMPO and 4-hydroxy-TEMPO were more active in the oxidation of 1-phenylethanol compared to TEMPO. For these mediators kinetic isotope effects in the range of 2.1-3.2 were observed for α-monodeutero-p-methylbenzyl alcohol oxidation. These values are consistent with a mechanism involving oxoammonium intermediacy. Competition experiments between benzyl alcohol and 1-phenylethanol showed that TEMPO and its derivatives react faster with primary alcohols than with secondary alcohols, also in line with the proposed mechanism.     

In situ-generated N-thiocyanatosuccinimide (NTS) as a highly efficient reagent for the one-pot thiocyanation or isothiocyanation of alcohols

The first application of in situ-generated N-thiocyanatosuccinimide (NTS) for the thiocyanation of alcohols is described. This method can be easily applied for the facile conversion of primary, secondary and tertiary alcohols into the corresponding alkyl thiocyanates or alkyl isothiocyanates in good to excellent yields.     

水相中底物促进的铜催化氨基醇N-芳基化反应

在水相体系中, 利用铜催化一系列氨基醇类底物(1.2 mmol)与碘代芳烃(1.0 mmol)进行N-芳基化反应. 由于氨基醇具有双齿配位及相转移催化能力, 该反应利用氨基醇类底物自身的促进作用, 在不使用外加配体与相转移催化剂的温和条件下以高收率获得了氨基醇N-芳基化产物(64%-93%).     

Selective and efficient oxidation of sulfides to sulfoxides with N-bromosuccinimide in the presence of β-cyclodextrin in water

A simple and highly selective oxidation of sulfides to sulfoxides with N-bromosuccinimide (NBS) catalyzed by β-cyclodextrin in water has been developed. A series of sulfides were oxidized selectively at room temperature in excellent yields. This reaction proceeds without over-oxidation to sulfones under mild conditions using water as a solvent and has many advantages over the existing methodologies.     

Fluorination of alcohols and diols with a novel fluorous deoxy-fluorination reagent

We prepared a novel fluorous deoxy-fluorination reagent N,N-diethyl-α,α-difluoro-[3,5-bis(1H,1H,2H,2H-perfluorodecyl)benzyl]amine (1b) from 3,5-diiodobenzoic acid (3b) via N,N-diethyl-3,5-bis(1H,1H,2H,2H-perfluorodecyl)benzamide (2b) in four steps and used it for the fluorination of alcohols and diols. After the fluorination reactions, the isolation of the products and recovery of 2b was performed by extraction with a fluorous/organic solvent system.     

Aerobic alcohol oxidation using a PdCl2/N,N-dimethylacetamide catalyst system under mild conditions

A new and simple PdCl₂/DMA catalytic system for the alcohol oxidation has been developed using molecular oxygen as the sole oxidant under mild conditions. The catalytic system could be reused for three runs without significant loss of catalytic activity. A variety of active and non-active alcohols were oxidized to their corresponding carbonyl compounds in good to excellent yields. Gas-uptake kinetics for the catalytic system was also investigated. The ca. 1:1 molar ratio of O₂ uptake to product yield is observed, suggesting the in situ formation of H₂O₂.     

Silica gel promoted synthesis of N-sulfonylcyclothioureas in water

N-Sulfonylcyclothioureas were synthesized from N-sulfonyldiamines and CS₂ with moderate to good yields in silica gel-water system. Moreover, the silica gel can be recycled for at least three times.     

Palladium(II)-N-heterocyclic carbene complex derived from proline towards Suzuki-Miyaura coupling reaction in water at room temperature

Palladium(II)-N-heterocyclic carbene complex 1 derived from proline has been proved to be a highly effective catalyst in the Suzuki-Miyaura coupling reaction of aryl iodides and bromides with arylboronic acids in water at room temperature. The reactions are tolerant towards various functional groups in the substrates. Moreover, the complex 1-catalyzed medium-scale (10.0 mmol) Suzuki-Miyaura reactions were also carried out and it was found that the complex was also effective enough in these cases.     

Synthesis of enantiopure azetidines: a route to new β-amino alcohols

β-Amino alcohols possessing an E vinylsilane moiety were cyclized in the presence of N-bromosuccinimide to afford diastereoisomerically pure polyfunctional azetidines. These azetidines were then transformed into enantiopure β-amino alcohols with a Z vinylic bromide moiety.     

Oxidant-dependent selective oxidation of alcohols utilizing multinuclear copper-triethanolamine complexes

Multinuclear Cu(II)-triethanolamine complexes were employed as catalysts for the selective oxidation of primary and secondary alcohols using tert-butylhydroperoxide (TBHP) and O₂/2,2′,6,6′-tetramethylpiperidinyl-1-oxyl (TEMPO) system, respectively. The catalytic performances, especially in terms of selectivities, were oxidant-dependent in forming the corresponding carbonyl compounds as the major products. Excellent selectivities and moderate to good yields were obtained for the transformation of secondary alcohols to ketones in the case of TBHP and also for the conversion of benzylic primary alcohols to aldehydes in the case of O₂/TEMPO system.     

TEMPO-catalyzed oxidation of benzylic alcohols to aldehydes with the H2O2/HBr/ionic liquid [bmim]PF6 system

A selective oxidation of benzylic alcohols to the corresponding aldehydes in room temperature ionic liquid was achieved by using TEMPO/HBr/H₂O₂ system, and both ether-insoluble acetamido-TEMPO and ionic liquid [bmim]PF₆ can be successfully recovered and reused for the oxidation of the same (different) substrate.     

Efficient synthesis of carbonyl compounds: oxidation of azides and alcohols catalyzed by vanadium pentoxide in water using tert-butylhydroperoxide

Catalytic amount of vanadium reagent with tert-butylhydroperoxide as the oxidant was found to be an excellent oxidizing agent in aqueous medium. Vanadium pentoxide with aq tert-butylhydroperoxide readily oxidizes primary benzylic azides to the corresponding acids and secondary benzylic azides to the corresponding ketones in excellent yields. Further, vanadium pentoxide and aq tert-butylhydroperoxide combination turned out to be an effective catalyst for the oxidation of alcohols. Using vanadium pentoxide and aq tert-butylhydroperoxide primary alcohols were oxidized to the corresponding acids, whereas secondary alcohols underwent a smooth transformation to furnish corresponding ketones in excellent yields. All the oxidations are performed in water.     

One-pot synthesis of N-alkyl purine and pyrimidine derivatives from alcohols using TsIm: a rapid entry into carboacyclic nucleoside synthesis

A convenient and efficient one-pot N-alkylation of nucleobases from alcohols using N-(p-toluenesulfonyl)imidazole (TsIm) is described. In this method, treatment of alcohols with a mixture of purine or pyrimidine nucleobase, TsIm, K₂CO₃, and triethylamine in refluxing DMF regioselectively furnishes the corresponding N-alkyl nucleobases in good yields. This methodology is highly efficient for various structurally diverse primary alcohols.     

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.     

Identification of phenyl-N-methylcarbamates and their transformation products in Tunisian surface water by solid-phase extraction liquid chromatography-tandem mass spectrometry

Liquid chromatography-pneumatically assisted electrospray mass spectrometry with both negative and positive ionization has been used for the determination of carbamates pesticides and their transformation products in Tunisian surface water. Eight pesticides and four of their hydrolysis products were covered in this study.Optimization of electrospray inlet conditions is described as well as results from investigations of the linearity of the detector response. Conditions for tandem mass spectrometry (MS-MS) detection of characteristic daughter ions formed by collision induced dissociation (CID) of the parent ion are described. Detection limits using MS in the selected ion monitoring (SIM) mode were generally in the order of 0.5 μg L⁻¹ or below. A principle of analysis is proposed based on triple quadrupole MS as a method for quantitative determination followed by verification of positive findings by CID-MS-MS. Application of the method for detecting carbamates residues in surface water is demonstrated.