Alcohol coupled oxidation

An intriguing example of those enzymes that use both tyrosine residues and transition metal ions as partners in affecting redox chemistry is the fungal enzyme GO (GO EC 1.1.3.9 68 kD) (60,61,81), which catalyzes the two-electron oxidation of primary alcohols coupled to the two-electron reduction of O2 to H2O2, Eq. (2). 

R)-alcohols in high enantiomeric excess can be obtained with the aid of the NADP-dependent ADH from Lactobacillus kefir. Due to the broad substrate specificity of this enzyme, aromatic, cyclic, polycyclic as well as aliphatic ketones can be reduced. A simple method for the regeneration of NADPH is given by the simultaneously coupled oxidation of isopropanol by the same enzyme. Several chiral alcohols (Table 8) were synthesized at a 2.5 mmol scale within a reaction time of 12-36 h [160]. 

Note that Table I shows that primary alcohols are not effectively oxidized by the KMhO /CuSO, couple. This contrasts with the usual solution behavior where primary alcohols are oxidized faster than secondary alcohols. Thus, the solid phase system presented the possibility of carrying out selective oxidations not easily accomplished In solution CH2CH CH OH... 

Corey et al reported that the complex formed by chromium(VI) oxide and 2,4-dimethylpentane-2,4-diol can be used as a catalytic oxidant with peroxyacetic acid as a cooxidant. When used stoichiome-trically, secondary alcohols are oxidized quickly even at -20 C, but the oxidation of primary alcohols is slow and large amounts of ester coupling are observed. 

Primary and secondary alcohols are oxidized to the corresponding carboxylic acids and ketones, respectively (Eqs. 3.41 and 3.42) [4c, 77]. Electrooxidation using a double mediatory system consisting of RUO4/RUO2 and C /Cr redox couples is also effective for oxidation of alcohols (Eq. 3.43) [77e]. 

A single enzyme is sometimes capable of many various oxidations. In the presence of NADH (reduced nicotinamide adenine dinucleotide), cyclohexanone oxygenase from Acinetobacter NCIB9871 converts aldehydes into acids, formates of alcohols, and alcohols ketones into esters (Baeyer-Villiger reaction), phenylboronic acids into phenols sulfides into optically active sulfoxides and selenides into selenoxides [1034], Horse liver alcohol dehydrogenase oxidizes primary alcohols to acids (esters) [1035] and secondary alcohols to ketones [1036]. Horseradish peroxidase accomplishes the dehydrogenative coupling [1037] and oxidation of phenols to quinones [1038]. Mushroom polyphenol oxidase hydroxylates phenols and oxidizes them to quinones [1039]. 

The union of fragments 78 and 81 was performed by treatment of 81 with t-BuLi to induce a bromine-lithium exchange, followed by transmetal lation to the cerium reagent [49] and finally the addition of aldehyde 78 (Scheme 17). The coupled product was obtained in 85% yield as a diastereomeric mixture of alcohols. Swem oxidation [50] and reaction with MeMgBr at -78 °C provided the tertiary alcohol stereoselectively in 98% yield. A final deprotection with tosic acid gave venustatriol (2). 

Allylic and benzylic alcohols are oxidized to carbonyl compounds with the Pd(0Ac),-02/DMS0 system. " The behavior of benzylic bromides toward (PhjPjCoCI differs in the presence or absence of oxygen under oxidative conditions aldehydes are formed, otherwise C-C bond coupling occurs. ... 

Oxidations with sodium persulfate are markedly catalyzed by silver ions the actual reagent is presumed to be SjOg Ag". Toluene is oxidized to benzaldehyde (50% yield) together with coupled products, and benzyl alcohol is oxidized to benzaldehyde (75% yield). Phenols are oxidized to resinous polyphenols. ... 

Surface plasmon resonance 1000 Surfactants 948, 972 Suzuki coupling 1406, 1424 Sympathomimetic drugs 995 Synergism 889-891 Syringic acid, irradiation of 1079 Syringyl alcohol, catalytic oxidation of 1205, 1208... 

The ease with which alcohols are oxidized to aldehydes, ketones, or carboxylic acids (depending on the alcohol that you start with and the conditions that you employ), coupled with the ready availability of alcohols, provides the pathway necessary to many successful s)mthetic transformations. For example, let s develop a method for synthesizing ethyl propanoate, using any inorganic reagent you wish but limiting yourself to organic alcohols that contain three or fewer carbon atoms ... 

In an alcoholic solution of a primary amine, the alcohol is oxidized to an aldehyde or ketone, which couples with the amine to form a Schiff-base by N-alkylation. The intermediate is then reduced to a secondary amine (Fig. 10) [146]. Similar reactions can yield tertiary amines. 

Thus, the coupled oxidation of C1-C4 alkanes and SnCl2 was found to proceed in acetonitrile at room temperature [47a]. The yields of alcohols, which are the oxidation products, reach 7-15% per SnCh. Comparatively high yields of the products of cyclohexane oxidation are obtained in the presence of oxidizing... 

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