Oxidations of alcohols and diols

Ri and R2 can be alkyl groups or hydrogen. The oxidation of one tertiary alcohol, terf.-butyl alcohol, has been studied the stoichiometry is uncertain, but acetone and formaldehyde are the main products (section 2.2.5). 

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By using various polypyridyl oxo complexes a relationship between redox potentials ( 1/2) of the complexes and the efficiency and the selectivity of the electrocatalytic oxidation of alcohols and diols has been established.506 Higher 1/2 gives higher reactivity. The best results, from the point of view of synthesis, were obtained with the complex /ra ,v-[Ru (terpy)(0)2(0I I2)]2 which is characterized by a high redox potential and a relatively high stability. 

Gold catalyzed oxidations of alcohols and diols possess great potential towards selectivity [10]. As example, chemical kinetics was measured during the catalytic oxidation of ethylene glycol based on the O2 consumptiom Deposited Au on the porous glass shows no catalytic activity while the Au loaded ceria replica shows an initial activity of 53 mmol-gAu min within the first 10 minutes of the reaction. In the latter case, after 60 minutes a conversion of 59% was obtained. As main prodnct glycolic acid was produced at a selectivity of 94%. Oxalic acid and glyoxylic acid were detected as side products. 

Miscellaneous Applications. The chemoselective oxidation of alcohols and diols using T 0-i- r)Jt-Butyl Hydroperoxide has been reported. The title reagent has also been employed as a catalyst in Diels-Alder reactions and as an additive in the palladium-catalyzed reaction of aryl-substituted allylic alcohols with zinc enolates of p-dicarbonyl compounds (eq 24). The latter... 

For the discussion of noncompetitive and mixed product inhibition, we turn to an actual case and its corresponding treatment in the literature (L. G. Lee, 1986). The oxidation of alcohols, especially diols, to ketones with dehydrogenases and concomitant reduction of NAD+ to NADH is prone to product inhibition by the ketones. 

The use of organometallic rhenium complexes has found a very broad scope as oxidation catalysts as described in the previous section, making MTO the catalyst of choice for many oxidation reactions of olefins. Interestingly, MTO and related rhenium compounds have also found application in the reverse reaction, the deoxygenation of alcohols and diols. Especially in recent years, this reaction has attracted much attention due to the increased interest in the use of biomass as feedstock for the chemical industry. This section provides an overview of the use of rhenium-based catalysts in the deoxygenation reaction of renewables. 

This phase can be used in the preparative and analytical stereochemical resolution of a wide variety of compounds, including acetate derivatives of alcohols and diols benzylic alcohol derivatives pora-substituted d-phenyl-d-valerolactones 3,4-dihydro-2H-pyran-2-carboxylic acid derivatives phenylvinylsulfoxide fra s-stilbene oxide (46). 

De Munari, S., Frigerio, M., Santagostino, M. Hypervalent Iodine Oxidants Structure and Kinetics of the Reactive Intermediates in the Oxidation of Alcohols and 1,2-Diols by o-lodoxybenzoic Acid and Dess-Martin Periodinane. A Comparative 1H-NMR Study. J. Org. Chem. 1996, 61, 9272-9279. 

Y. Ishii, K. Yamawaki, T. Ura, H. Yamada, T. Yoshida, M. Ogawa, Hydrogen peroxide oxidation catalyzed by heteropoly acids combined with cetylpyridinium chloride. Epoxidation of olefins and allylic alcohols, ketonization of alcohols and diols, and oxidative cleavage of 1,2-Diols and olefins,/. Org. Chem. 53 (1988) 3587. 

In 2003, Chen et al. studied the effect of different types of ionic liquids in the oxidation of alcohols and 1,2-diols with IBX. The DMSO is not protic solvent found that [bmim][Cl] is the better choice because it can readily dissolve IBX in the presence of small amounts of water at room temperature to form a homogeneous... 

Scheme 14.14 Oxidation of alcohols and 1,2-diols with IBX in [bmim][Cl]...

Oxidation of ols and diols (7, 414-415). Even unprotected scc-alcohols can be oxidized to ketones by trityl tetrafluoroborate (2 equiv.) in CHaCla at 25 (10-13 hours). Typical yields are in the range 65-857o- Primary, secondary diols can be oxidized selectively to hydroxy ketones by the reagent (2.1-2.2 equiv.) under the same conditions (yields 55-807o). 

Ishii, Y, Yamawaki, K., Ura, T., et al (1988). Hydrogen Peroxide Oxidation Catalyzed by Heteropoly Acids Combined with Cetylpyridinium Chloride. Epoxidation of Olefins and Allylic Alcohols, Ketonization of Alcohols and Diols, and Oxidative Cleavage of 1,2-Diols and Olefins, J. Org. Chem., 53, pp. 3587-3593. 

Ishii, Y., Yamawaki, K., Ura, T., et al. (1988). Hydrogen Peroxide Oxidation Catalyzed by Heteropoly Acids Combined with Cetylpyridinium Chloride. Epoxidation of Olefins And Allylic Alcohols, Ketonization of Alcohols and Diols, and Oxidative Cleavage of 1,2-Diols and Olefins, J. Org. Chem., 53, pp. 3587-3593 Sato, K., Aoki, M., Ogawa, M., et al. (1997). A Halide-Free Method for Olefin Epoxidation with 30% Hydrogen Peroxide, Bull. Chem. Soc. Jpn., 70, pp. 905-915 Xi, Z. W., Zhou, N., Sun, Y., et al. (2001). Reaction-Controlled Phase-Transfer Catalysis for Propylene Epoxidation to Propylene Oxide, Science, 292, pp. 1139-1141 Neumann, R. 

Trityl tetrafluoroborate oxidizes secondary alcohols to ketones primary, secondary diols are selectively oxidized at the secondary position by this reagent. /Lt-Oxo-bis(chlorotriphenylbismuth) is a mild reagent for the oxidation of alcohols, and is particularly suitable for the oxidation of the hydroxy-group in allylic alcohols. Dichlorodicyanobenzoquinone (DDQ) with periodic acid in HCl-benzene has also been used for the latter purpose. ... 

DMSO can be boiled under reflux for long periods largely unchanged (3.7% of volatile decomposition products after 72 h) but under air or O2 in a sealed tube, kept just below the boiling point (189 C) for 68 h, it is completely transformed into paraformaldehyde, dimethyl sulphide, and bis(methylthio)methane, water, and dimethyl disulphide." " Peroxides catalyse the decomposition, as does MeSOjH." " The formaldehyde formed in this way can be used for in situ methylene acetal formation with oxidation products of alcohols and diols." Reduction of DMSO with Br2+HBr gives MezS, MeSOsH, and paraformaldehyde, while diphenyl sulphoxide is unchanged." ... 

The C2-symmetric epoxide 23 (Scheme 7) reacts smoothly with carbon nucleophiles. For example, treatment of 23 with lithium dimethylcuprate proceeds with inversion of configuration, resulting in the formation of alcohol 28. An important consequence of the C2 symmetry of 23 is that the attack of the organometallic reagent upon either one of the two epoxide carbons produces the same product. After simultaneous hydrogenolysis of the two benzyl ethers in 28, protection of the 1,2-diol as an acetonide ring can be easily achieved by the use of 2,2-dimethoxypropane and camphor-sulfonic acid (CSA). It is necessary to briefly expose the crude product from the latter reaction to methanol and CSA so that the mixed acyclic ketal can be cleaved (see 29—>30). Oxidation of alcohol 30 with pyridinium chlorochromate (PCC) provides alde-... 

Heteropoly acids can be synergistically combined with phase-transfer catalysis in the so-called Ishii-Venturello chemistry for oxidation reactions such as oxidation of alcohols, allyl alcohols, alkenes, alkynes, P-unsaturated acids, vic-diols, phenol, and amines with hydrogen peroxide (Mizuno et al., 1994). Recent examples include the epoxidations of alkyl undecylenates (Yadav and Satoskar, 1997) and. styrene (Yadav and Pujari, 2000). 

The addition of Grignard reagents to aldehydes, ketones, and esters is the basis for the synthesis of a wide variety of alcohols, and several examples are given in Scheme 7.3. Primary alcohols can be made from formaldehyde (Entry 1) or, with addition of two carbons, from ethylene oxide (Entry 2). Secondary alcohols are obtained from aldehydes (Entries 3 to 6) or formate esters (Entry 7). Tertiary alcohols can be made from esters (Entries 8 and 9) or ketones (Entry 10). Lactones give diols (Entry 11). Aldehydes can be prepared from trialkyl orthoformate esters (Entries 12 and 13). Ketones can be made from nitriles (Entries 14 and 15), pyridine-2-thiol esters (Entry 16), N-methoxy-A-methyl carboxamides (Entries 17 and 18), or anhydrides (Entry 19). Carboxylic acids are available by reaction with C02 (Entries 20 to 22). Amines can be prepared from imines (Entry 23). Two-step procedures that involve formation and dehydration of alcohols provide routes to certain alkenes (Entries 24 and 25). 

Hofmann degradation of the nonnatural protoberberine 454 afforded the 10-membered ring base 455 (65%) in addition to the styrene-type compound (13%) (Scheme 92). Dihydroxylation of the former with N-bromosuccinimide in the presence of a large excess of hydrochloric acid and subsequent oxidation of the product diol 456 with periodic acid afforded the dialdehyde 457. On irradiation in tert-butyl alcohol 457 provided ( )-cis-alpinigenine (445) along with ( )-alpinigenine (441) as a result of endo and exo intramolecular cycloaddition, respectively, of the intermediate photodienol (221,222). 

Halogens are frequently used as oxidation agents and, under two-phase conditions, they can either be employed as ammonium complex halide salts [3], or in the molecular state with or without an added quaternary ammonium catalyst [4]. Stoichiometric amounts of tetra-n-butylammonium tribromide under pH controlled conditions oxidize primary alcohols and low-molecular-weight alkyl ethers to esters, a,cyclic ethers produce lactones [3], and secondary alcohols yield ketones. Benzoins are oxidized to the corresponding benzils (80-90%) by the tribromide salts in acetonitrile in the presence of benzoyl peroxide [5]. 

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