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[Display omitted] • New cis -dioxo Mo(VI) complexes incorporating ONO donor Schiff base ligands derived from dihalosalicylaldehyde and nicotinic hydrazide were synthesized and characterized. • X-ray crystallographic study has confirmed the structures of the H 2 Cl 2 SN ligand and two Mo(VI) complexes (2 & 3). • All complexes were successfully screened as catalysts for the selective oxidation of benzylic alcohols employing ethanol and hydrogen peroxide. Three ONO donor Schiff base ligands were obtained by the condensation of 3,5-dihalosalicylaldehydes with nicotinoylhydrazide (H 2 Cl 2 SN: (E)-N'-(3,5-dichlorosalicylaldehyde) nicotinoylhydrazone, H 2 Br 2 SN: (E)-N'-(3,5-dibromosalicylaldehyde) nicotinoylhydrazone, and H 2 I 2 SN: (E)-N'-(3,5-diiodosalicylaldehyde) nicotinoylhydrazone on refluxing in ethanol. The treatment of [MoO 2 (acac) 2 ] (acac = acetylacetonato) with these ligands in methanol afforded cis -dioxidomolybdenum(VI) complexes [MoO 2 (Cl 2 SN)(CH 3 OH)] (1), [MoO 2 (Br 2 SN)(CH 3 OH)] (2), and [MoO 2 (I 2 SN)(CH 3 OH)] (3). Various techniques like NMR (1H and 13C), FT-IR, Mass, TGA, elemental (CHN), and single-crystal X-ray diffraction analysis (for H 2 Cl 2 SN · H 2 O , 2a , [MoO 2 (Br 2 SN)(C 2 H 5 OH)], and 3a , [MoO 2 (I 2 SN)(H 2 O)].DMF) were utilized to characterize the synthesized compounds. The data collected from diffraction studies revealed that the geometry around Mo(VI) ions was distorted octahedral. Additionally, all complexes were successfully screened as catalysts for the selective oxidation of benzylic alcohols employing ethanol and hydrogen peroxide. [ABSTRACT FROM AUTHOR]

The oxidation of benzylic alcohol to corresponding aldehyde and ketone using N-chlorosuccinimide (NCS)–N,N-dimethylformamide (DMF) has been described. This method gives easy access to the corresponding carbonyl compounds under metal-free conditions, without the use of corrosive reagent at ambient temperature in good yield. [ABSTRACT FROM AUTHOR]

A practical protocol was disclosed for the nickel-catalyzed C-alkylation of 9-fluorenone hydrazone with alcohols using t-BuOK as the base, and 9-monoalkylated fluorene derivatives were obtained in good yields under the benign conditions. [ABSTRACT FROM AUTHOR]

A strategy for the dehydrative N-benzylation of electron-deficient anilines in water has been developed. The gold(III)/sodium diphenylphosphinobenzene-3-sulfonate (TPPMS) catalyst is highly effective as a Lewis acid for the activation of alcohols and tolerates aerobic conditions. A Hammett study in the reaction of para -substituted benzhydryl alcohols shows negative σ values, indicating a build-up of cationic charge during the rate-determining sp3 C–O bond-cleavage step. The inverse kinetic solvent isotope effect (KSIE = 0.6) is consistent with a specific acid catalysis mechanism. This simple protocol can be performed under mild conditions in an atom-economic process without the need for base or other additives, furnishing the electron-deficient N -benzylic anilines in moderate to excellent yields along with water as a sole coproduct. [ABSTRACT FROM AUTHOR]

A method for the solvent-free photocatalytic conversion of solid and liquid substrates was developed, using a novel rod mill apparatus. In this setup, thin liquid films are realized which is crucial for an effective photocatalytic conversion due to the low penetration depth of light in heterogeneous systems. Several benzylic alcohols were oxidized with riboflavin tetraacetate as photocatalyst under blue light irradiation of the reaction mixture. The corresponding carbonyl compounds were obtained in moderate to good yields.

A convenient and highly selective microwave assisted procedure for the conversion of allylic, benzylic and aliphatic alcohols to their corresponding halide using polymer-bound triphenylphosphine and iodine is presented. In case of symmetrical diols, mono-iodination product is obtained in very high yield. Additionally, high regioselective behavior is observed in our procedure. Simplicity in operation, no column chromatography requirement for purification of the product, recyclability of the reagents used, short reaction times and good to excellent yields are the advantages of our protocol. Most functional groups remain unaffected under our reaction condition.

We describe the dehydroxymethylbromination of alkoxybenzyl alcohol by using a hypervalent iodine reagent and lithium bromide in F3CCH2OH at room temperature. Selective monobromination or dibromination was possible by adjusting the molar ratios of hypervalent iodine reagent and lithium bromide. [ABSTRACT FROM AUTHOR]

The graphene-based materials, particularly graphene oxide (GO) with rich oxygenated groups, exhibit high catalytic performance in various metal-free oxidation reactions. However, the intrinsic active site is still unclear, which greatly retards to further develop advanced catalysts. Here, the modified graphene oxide (abGO) was synthesized by sequential base and acid treatment and employed in the aerobic oxidation of benzyl alcohol to benzaldehyde. This novel catalyst displayed much higher activity, selectivity and stability than that of conventional GO. 93.1% conversion and 100% selectivity were achieved over abGO. More importantly, it is shown that the yield of benzaldehyde is linearly proportional to the content of surface phenol hydroxyl groups. Experimentally observed reactivity trends, structure-behavior correlation, molecule mimicking and characterization results strongly confirm that the surface phenol hydroxyl groups are the intrinsic active sites. [ABSTRACT FROM AUTHOR]

An efficient, facile, and mild oxidation of a variety of primary benzylic alcohols to the corresponding aldehydes with potassium peroxodisulfate in the presence of a catalytic amount of sodium chloride and silica sulfuric acid (SSA) in acetonitrile as solvent is reported. It is a renowned fact that potassium peroxodisulfate acts as a powerful oxidizing agent and the control of conditions is difficult. For this purpose, SSA as a mild, efficient and reusable solid acid catalyst was used to afford the carbonyl compounds in excellent yields and short time. The structure of all of the resulting products was confirmed by FT-IR spectroscopy.DOI: http://dx.doi.org/10.4314/bcse.v27i1.14

Alcohol oxidation to carbonyl compounds is one of the most commonly used reactions in synthetic chemistry. Herein, we report the use of base metal layered double hydroxide (LDH) catalysts for the oxidation of benzylic alcohols in polar solvents. These catalysts are ideal reagents for alcohol oxidations due to their ease of synthesis, tunability, and ease of separation from the reaction medium. LDHs synthesized in this study were fully characterized by means of X-ray diffraction, NH3-temperature programmed desorption (TPD), pulsed CO2 chemisorption, N2 physisorption, electron microscopy, and elemental analysis. LDHs were found to effectively oxidize benzylic alcohols to their corresponding carbonyl compounds in diphenyl ether, using O2 as the terminal oxidant. LDH catalysts were also applied to the oxidation of lignin β-O-4 model compounds. Typically, for all catalysts, only trace amounts of the ketone formed from benzylic alcohol oxidation were observed, the main products comprising benzoic acids and phenols arising from β-aryl ether cleavage. This observation is consistent with the higher reactivity of the ketones, resulting from weakening of the Cβ–O4 bond that was shown to be aerobically cleaved at 180 °C in the absence of a catalyst.

Various primary and secondary benzylic alcohols were efficiently oxidized to aromatic aldehydes and aromatic ketones with iodic acid in DMF at 60 °C for 2 h and with iodic acid in the presence of TEMPO (5 mol %) in DMF at room temperature, respectively. The former method was effective for the oxidation of sterically hindered alcohols at 60 °C and the latter method was effective for the oxidation of less sterically hindered alcohols at room temperature. [ABSTRACT FROM AUTHOR]

A new two-step lignin depolymerization strategy was developed, in which the benzylic alcohols in lignin was methylated under microwave irradiation, followed by a hydrogenolysis for the cleavage of β O 4 bond with Pd/C as the catalyst. The results showed that an efficient and selective catalytic methylation of benzylic alcohols was achieved with various lignin model compounds, and the acidic environment promoted the methylation of benzylic alcohol. Methylation of benzylic alcohol increased the β O 4 bond cleavage rate by 55.9%, and improved products selectivity. Preliminary study of lignin depolymerization illustrated that methylation pretreatment of benzylic alcohols facilitated lignin depolymerization to produce aromatic monomers and reduced the oxygen content of aromatic monomers. [ABSTRACT FROM AUTHOR]

Oxidation of benzylic alcohol to ketone or aldehyde is one of the most challenging reactions in terms of green chemistry. We report herein that employing H 2 O 2 , catalytic amount of Br − and acid in continuous-flow system to realize oxidation of benzylic alcohols with broad substrate scope and high selectivity. More importantly, no over oxidation to acid was obtained and it showed higher selectivity to 2° hydroxyl groups rather than 1°. [ABSTRACT FROM AUTHOR]

Instead of traditional N,N-bidentate ligands, N-functionlized amino acids were used as powerful N,O-bidentate ligands in aerobic copper/TEMPO-catalyzed system for promoting oxidation of benzylic alcohols. Under the optimized reaction conditions, a wide range of primary and secondary benzylic alcohols have been efficiently converted into aldehydes and ketones with good to excellent yields in water. [ABSTRACT FROM AUTHOR]

The biooxidation of benzylic alcohols catalyzed by (5-hydroxymethyl)furfural oxidase (HMFO) to the corresponding benzaldehydes or benzoic acids was investigated in the presence of various organic (co)solvents. Whereas the enzyme activity decreased at elevated concentrations of water-miscible polar solvents, the presence of (halogenated) hydrocarbons was tolerated up to 90% (v/v), which led to drastically improved conversions of up to >99% in case of hexafluorobenzene. This remarkable effect was correlated with the improved solubility of O 2 in the employed solvents. Reaction rates were boosted by O 2 -saturation of solvents. [ABSTRACT FROM AUTHOR]

We herein report a catalyst system for the dynamic kinetic resolution of secondary alcohols by combining the enzymatic resolution with an iron-catalyzed racemization. A new air-stable tricarbonyl (cyclopentadienone)iron complex is identified as the active racemization catalyst for this transformation without any additive. Various substrates including benzylic, heteroaromatic, aliphatic alcohols can be used and afford the corresponding esters in good yields and with excellent enantioselectivities. [ABSTRACT FROM AUTHOR]

• The β -O-4 bond cleavage reactivity was significantly enhanced via benzylic alcohol dehydration to α , β -alkenyl group (C α =C β) under a Pd/C hydrogenolysis system. • An easy formation of C α H─H from the C α =C β hydrogenation led to the enhancement of the β -O-4 bond cleavage reactivity being achieved. • The formation of C α H─H increased the β -O-4 bond cleavage rate by 6.2 times compared to C α =O. • The β -O-4 bond attached to the C α =C β was more thermodynamically favorable to be cleaved. Lignin has immense potential for the production of monoaromatics that can be further prepared as target chemicals or alkyl biofuels. In this work, experiments and density functional theory (DFT) calculations were employed to investigate the effect of benzylic alcohol (α -hydroxyl group, C α H─OH) dehydration to α , β -alkenyl group (C α = C β) on the enhancement of the β -aryl ether (β -O-4) bond cleavage reactivity of lignin model dimer over Pd/C by formic acid. This study demonstrated that the β -O-4 bond cleavage reactivity was significantly enhanced via the benzylic alcohol dehydration to C α = C β. The cleavage reactivity of the β -O-4 bond attached to C α functional groups was in the order of α -hydrogen atom (C α H─H) > C α H─OH > α -carbonyl group (C α = O). An easy formation of the C α H─H from the C α = C β hydrogenation led to the enhancement of the β -O-4 bond cleavage reactivity being achieved. The β -O-4 bond cleavage rate was increased by 6.2 times in the presence of the C α H─H compared to the C α = O. Due to few and lower required energy barriers after C α H─OH dehydration, the β -O-4 bond attached to the C α = C β was more thermodynamically favorable to be cleaved. The work highlights the prospect of efficient depolymerization of lignin into monoaromatics. [ABSTRACT FROM AUTHOR]

The aerobic oxidation of benzylic alcohols to their corresponding aldehydes was performed in a RuCl3 · 3H2O–dicyclohexylamine (DCHA) catalyst system under ambient atmosphere at room temperature. It is noteworthy that the RuCl3 · 3H2O–DCHA system displayed a preference for the primary versus secondary benzylic alcohols in both intermolecular and intramolecular competition experiments. [ABSTRACT FROM PUBLISHER]

A variety of benzylic alcohols were oxidized to the corresponding carbonyl compounds selectively with 30% hydrogen peroxide (H2O2) in the presence of activated carbon. Alkylarenes such as fluorenes, xanthenes, and anthrone were also effectively oxygenated to the corresponding carbonyl compounds with 30% H2O2 as oxidant in the presence of activated carbon. [ABSTRACT FROM AUTHOR]

Abstract: 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. [Copyright &y& Elsevier]

The combination of FeCl3 and PMHS is an efficient reducing system for the selective dehydroxylation of secondary benzylic alcohols, even in the presence of carbonyls, under very mild conditions. [ABSTRACT FROM AUTHOR]

A metal-free aerobic oxidation of benzylic alcohols to the corresponding benzylaldehyde derivatives was accomplished using proton ionic liquids (pyridium nitrate) as catalyst in a nonsolvent system with excellent conversion and selectivity. The catalyst could be recycled with no other polluted emission in this reaction procedure. [image omitted] [ABSTRACT FROM AUTHOR]

Abstract: Selective oxidation of benzyl alcohol to benzaldehyde in aqueous solution, under acidic conditions, through the TiO2/Cu(II)/solar UV photocatalytic system, was investigated. Different commercial TiO2 samples were tested. The best result found, in terms of yield, was of 35% for benzaldehyde with respect to the initial benzyl alcohol concentration. During a single run, a partial conversion of benzaldehyde to benzoic acid was also observed. By-products, present at trace level, were 2-hydroxy-benzyl-alcohol, 4-hydroxy-benzyl-alcohol, 2-hydroxy-benzaldehyde and 4-hydroxy-benzaldehyde. On the basis of the formation of these species a production of HO radicals could be thus inferred. The study suggested that different operative parameters, such as the composition and amount of photocatalyst, pH, ionic components in water and the initial concentration of Cu(II) ions, played an important role in the photocatalytic selective oxidation of benzyl alcohol. Moreover, the results of the present investigation indicated that, at the end of the process, Cu(II) could be regenerated and reused, through a re-oxidation of Cu(0), produced during the photolytic run, with air in the dark. A general mechanism of oxidation, supported by the experimental results was proposed. [Copyright &y& Elsevier]

[image omitted] A new environmentally friendly method for oxidation of benzylic alcohols to aldehydes or ketones has been developed using trichloroisocyanuric acid and [bmim]BF4 in water. [ABSTRACT FROM AUTHOR]

Abstract: We reported herein new reactivities and possible mechanistic implications of a simplest oxidant (NaH/air) uncovered on a broad range of useful transformations, including aerobic alcohol oxidations, allylic alcohol isomerizations and oxidations, cyclopropyl alcohol fragmentations, and direct aryl aldehyde oxidative amidations. These readily implementable transition-metal-free processes feature exceptional material accessibility, operational simplicity, and environmental compatibility, and add new dimensions to its synthetic utilities that are fairly robust yet had not previously been fully realized and systematically explored. [Copyright &y& Elsevier]

Abstract: was employed as a catalyst for the conversion of alcohols into the corresponding iodides using NaI in CH3CN at room temperature. Present procedure is found to be selective for the conversion of benzylic alcohols in the presence of saturated alcohols into benzylic iodides. The catalyst was characterized by XRD, FTIR, elemental analysis, BET surface area and TG–DTA techniques. This protocol provides a mild and efficient way for the one pot conversion of structurally diverse alcohols to their corresponding alkyl iodides with high selectivity. Display Omitted [Copyright &y& Elsevier]