Cobalt benzyl alcohol

Wender and coworkers conclude that cobalt-catalyzed benzyl alcohol homologation involves the intermediate formation of car-bonium ions (8). However, since the methyl cation (CH3+) is unstable and difficult to form (9), it is more likely that methanol homologation to ethanol proceeds via nucleophilic attack on a protonated methyl alcohol molecule. Protonated dimethyl ether and methyl acetate forms have been invoked also by Braca (10), along with the subsequent formation of methyl-ruthenium moieties, to describe ruthenium catalyzed homologation to ethyl acetate. 

As, for the most part, the corresponding ester derivatives are a more important synthetic target, recent literature has demonstrated methods to prepare the esters directly. Examples include the use of nickel carbonyl in a methanol/dimethylformamide solvent system(37) the direct conversion of benzyl alcohol to methylphenyl-acetate using cobalt carbonyl(38) and a reaction system which utilizes an ammonium salt bound to an organic polymer(39). 

The reaction conditions were mild (room temperature, 1 atm CO) and a two-fold excess of base was used along with a catalytic amount of cobalt carbonyl. The product distribution was quantified by VPC. The mixtures contained starting material, ester product, and various amounts of methyl benzyl ether. No detectable amounts of benzyl alcohol, ketones, or hydrocarbons were seen. Potassium methoxide alone afforded mostly the ether. A mixture of potassium methoxide and alumina gave a slight improvement in ester yield but the predominant product was again the ether. In contrast, when potassium methoxide on alumina was used, the carboxyalkylated product, methyl phenylacetate, was prepared in 70 yield with little ether detected. Benzyl chloride reacted in a similar fashion under these mild reaction conditions. Other alkoxide and carbonate bases could be used as... 

MCBA enhances the solubility of the cobalt salts in MeCN solution, thereby ensuring better efficiency to a needed redox decomposition of the hydroperoxide intermediate of the substrate en route to the products". By using the HPI/Co(II)/MCBA/02 system in MeCN solution at 25 °C, competitive oxidations of p-X-substituted benzyl alcohols were run pairwise (Scheme 8). From the amount of the aldehydes produced, the relative reactivity (kx/ h) could be reckoned, and the acquired data provided a p = —0.68 in a Hammett plot vs. <7+. ... 

The reaction of o-nitrobenzaldehydes with some benzene derivatives in the presence of strong acid (H2S04, PPA) is a classical synthesis of acridinol N-oxides (373) (37BSF240) The synthesis works for benzyl alcohol, benzene, toluene and halobenzenes, but not for benzoic acid, benzonitrile, dimethylaniline, or nitrobenzene. Isoquinoline N-oxides (374) have been obtained from o-bromobenzaldoxime or the acetophenone derivative, and active methylene compounds with copper bromide and sodium hydride (77S760). The azobenzene cobalt tricarbonyl (375) reacts with hexafluorobut-2-yne to give a quinol-2-one (72CC1228), and the 3,4,5-tricyanopyridine (376) is formed when tetracyanoethylene reacts with an enaminonitrile (80S471). 

Toluene is, in low conversion, oxidized, with air, in the liquid phase to benzyl hydroperoxide, which yields mainly benzyl alcohol and some benzaldehyde upon hydrolysis, for example, in the presence of a cobalt salt. Benzyl alcohol thus obtained requires a more thorough purification for use in perfumes and flavors. 

Benzaldehyde. The addition of less than stoichiometric quantities of benz-aldehyde to CoH (H2 atmosphere) did not result in hydrogen absorption. However, when this procedure was carried out with CoH containing added alkali (KOH, 2x cobalt concentration), hydrogen was taken up, 1.0 atom of hydrogen being absorbed per mole of substrate. Since benzyl alcohol was isolated in 66% yield, it is assumed that a portion of the product may have been formed via a competitive Cannizzaro reaction. Reinforcing this assumption is the observation of an apparent depletion of alkali during the run. 

Zeno W. Wicks, Jr., Consultant, Las Cruces, NM, Drying Oils Pieter R, Wiederhold. General Eastern Instruments Corporation. Water-town. MA, Hygrometry and Psychrometry Paul Wight, Seneca Specialties. Manchester, U.K. Xanthene Dyes E. Williams, Cobalt Information Centre, Londtm. UK, Cobait Richard A Wilsak, Amoco Chemical Company. Naperville. IL Butylenes Richard A. Wilson, International Flavors Fragrances. Union Beach, NJ. http //www.ifT.coni/. Benzyl Alcohol and /j-Phenethyl Alcohol Oils, Essential... 

Schiff base-cobalt-nitro complexes are too mild as oxidants to react as such with alkenes. However, the addition of Lewis acids (e.g. BF3 Et20, LiPF6) to these complexes activates the nitro ligand and produces a variety of both stoichiometric and catalytic oxidations. Stoichiometric transformations involve the oxidation of sulfides to sulfoxides and 1,3-cyclohexadiene to benzene.467 Alcohols such as benzyl alcohol and cycloheptanol are catalytically transformed into the corresponding carbonyl compounds.467,474... 

Styrene derivatives can be selectively converted to the corresponding benzyl alcohols by molecular oxygen in the presence of bis(dimethylglyoximato)chloro(pyridine)cobalt(III) and sodium tetrahydroborate (equation 242).559 A likely mechanism for this reaction involves insertion of the alkene into the cobalt-hydride bond, followed by 02 insertion into the cobalt-carbon bond, as in equation (11), and decomposition of the peroxide adduct (168) to the ketone, which is reduced to alcohol by NaBH4 (equation 243). 

A range of aromatic alkenes and acrylic acid derivatives have been converted into benzyl alcohols and a-hydroxyalkanoic acids in good yields by a reductive oxidation process. This reaction is accomplished by reaction with oxygen and triethylsilane with a cobalt(II) catalyst, followed by treatment with trialkyl phosphites (equation 30)154. The aromatic olefins may also be converted into the corresponding acetophenone in a modified procedure where the trialkyl phosphite is removed155. In a similar reaction 2,4-alkadienoic acids are converted into 4-oxo-2-alkenoic acids156. 

Sobkowiak A, Sawyer DT (1991) Cobalt(II)-induced activation of dioxygen for the dehydrogenation of N-methylanilines and benzyl alcohol. J Am Chem Soc 113(25) ... 

The regeneration of the benzoquinone can also be achieved with dioxygen in the absence of the cobalt cocatalyst. Thus, Hanyu et al. [86] showed that a combination of RuCl2(Ph3P)3, hydroquinone and dioxygen, in PhCF3 as solvent, oxidized primary aliphatic, allylic and benzylic alcohols to the corresponding aldehydes in quantitative yields (Eq. 20). 

A detailed study has been made of the reaction of nuclear substituted benzyl alcohols with synthesis gas in the presence of dicobalt octa-carbonyl (Wender, Greenfield, Metlin, and Orchin, 19). Under the conditions of the reaction it was postulated that some of the dicobalt octacarbonyl is converted to cobalt hydrocarbonyl, HCo(CO)4, which is a strong acid. It was of interest to determine the effect of different substituent groups on (a) the variations in the speed of the reaction and (b) the relative proportions of the hydrogenated and homologated product. All reactions were conducted in as nearly an identical fashion as possible. The results are shown in Tables II and III. 

Ruthenium-exchanged hydrotalcites were shown by Kaneda and coworkers [156], to be heterogeneous catalysts for the aerobic oxidation of reactive allylic and benzylic alcohols. Ruthenium could be introduced in the Brucite layer by ion exchange [156]. The activity of the ruthenium-hydrotalcite was significantly enhanced by the introduction of cobalt(II) in addition to ruthenium(III), in the Brucite layer [157 ]. For example, cinnamyl alcohol underwent complete conversion in 40 min in toluene at 60 °C, in the presence of Ru/Co-HT, compared with 31% conversion under the same conditions with Ru-HT. A secondary aliphatic... 

Several Co complexes with chelating nitrogen ligands catalyze oxidation reactions, e.g. [CoII(bipy)2]2+ activates 02 and oxidizes N-methyl-anilines, benzyl alcohols, and aldehydes. In the absence of organic substrates 02 is reduced to H202.M Cobalt(II) complexes of tetraaza macrocyclic ligands (N4) reversibly form 02 adducts [(N4)CoOO]2+ which are rapidly reduced to [(N4)CoOOH]2+ these species are involved in the electro-reduction of 02 to H202.23... 

Substituted benzyl alcohols can be converted with cobalt carbonyl to the homologous amides under mild conditions, even using sterically hindered secondary amines (equation 42). 

Industrially performed catalytic oxidation reactions often suffer from drawbacks such as poor conversion and selectivity due to overoxidation, corrosive reaction media, lack of solvent and catalyst recycling, and negative environmental impact due to evaporation of the solvents. In order to provide a methodology that addresses these problems, ionic liquids have been investigated as reaction media. For example, the aerobic oxidation of benzyl alcohol and alkylbenzene to benzaldehyde and benzoic acids was performed in l-butyl-2,3-dimethylimidazolium tetrafluoroborate ([C4dmim][BF ]) using palladium and cobalt complexes respectively [34, 35]. 

Electronic spectra of liver alcohol dehydrogenase substituted with cobalt at the catalytic site. Binary complex with NAD.ternary complex with NAD and Cl (---------) binary complex with acetate (.) intermediate in the oxidation of benzyl alcohol with... 

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