Alcohols diols, oxidation

From the preceding discussion, it is easily understood that direct polyesterifications between dicarboxylic acids and aliphatic diols (Scheme 2.8, R3 = H) and polymerizations involving aliphatic or aromatic esters, acids, and alcohols (Scheme 2.8, R3 = alkyl group, and Scheme 2.9, R3 = H) are rather slow at room temperature. These reactions must be carried out in the melt at high temperature in the presence of catalysts, usually metal salts, metal oxides, or metal alkoxides. Vacuum is generally applied during the last steps of the reaction in order to eliminate the last traces of reaction by-product (water or low-molar-mass alcohol, diol, or carboxylic acid such as acetic acid) and to shift the reaction toward the... 

Generally, primary aliphatic alcohols are oxidized to their respective aldehydes, secondary aliphatic and aromatic alcohols to the corresponding ketones, and allyl and benzyl alcohols to their carboxylic acid or carboxylate ions. For instance, 2-propanol, acetaldehyde, and methyl-benzoate ions are oxidized quantitatively to acetone, acetate, and terephtalate ion respectively, while toluene is converted into benzoate ion with an 86% yield. Controlling the number of coulombs passed through the solution allows oxidation in good yield of benzyl alcohol to its aldehyde. For diols,502 some excellent selectivity has been reached by changing the experimental conditions such as pH, number of coulombs, and temperature. 

Primary and secondary alcohols are oxidized slowly at low temperatures by benzyltriethylammonium permanganate in dichloromethane primary alcohols produce methylene esters (60-70%), resulting from reaction of the initially formed carboxylate anion with the solvent, with minor amounts of the chloromethyl esters and the carboxylic acids. Secondary alcohols are oxidized (75-95%) to ketones [34] the yields compare favourably with those obtained using potassium permanganate on a solid support. 1,5-Diols are oxidized by potassium permanganate under phase-transfer catalytic conditions to yield 8,8-disubstituted-8-valerolactones [35] (Scheme 10.1). 

Benzene-l,4-diols are oxidized to quinones by benzyltrimethylammonium tribromide under mild conditions in almost quantitative yields [6]. With an excess of the tribromide further reaction produces the 2-bromo-l, 4-quinones. This oxidation is in contrast to the analogous reaction of phenols, which produces bromophenols (see Section 2.3). Hindered 4-methyl-phenols are oxidized to the corresponding benzyl alcohols, benzaldehydes, bromomethyl derivatives and 4-bromo-4-methylcyclo-hexa-2,5-dien-l-ones [7]. Benzylic alcohols are oxidized under neutral or basic conditions to yield the corresponding aldehydes (>70%) oxidation with an excess of the reagent produces the benzoic acids (>90%) [8],... 

Charged polymers Neutral polymers, e.g., polysaccharides, polyvinyl alcohol, polyethylene oxide Epoxide-based, diol, polyethylene glycol. 

It is noteworthy that allylic alcohols are oxidized to products with retained configuration of the olefinic bond. Geraniol and nerol were oxidized to the corresponding ( )-and (Z)-a-enals, respectively. As expected, primary alcohols were oxidized faster than secondary ones with the RuCl2(PPh3)3/BTSP system with relative rates from 20-40 1. The new system was applicable for the selective oxidation of primary-secondary diols... 

Oxidation of alcohols, diols, and 2-hydroxyacids in alkaline solution 364... 

From oxidative cleavage of 1,2-diols and 1,2-amino alcohols Dibutyltin oxide, 95 By reaction of alkyl halides with sulfur-stabilized carbanions Methylthiomethyl p-tolyl sulfone, 192 From reduction of carboxylic acids Vilsmeier reagent, 341 From terminal alkenes by addition reactions... 

In this tetrol, a single secondary alcohol is oxidized with 88% yield thanks to the formation of the most stable cyclic stannylene intermediate by the regioselective reaction of BU2S11O with one of the 1,2-diol moieties in the molecule. 

Gold NPs deposited on carbons are active and selective for mild oxidations in liquid phase although they exhibit almost no catalytic activity in the gas phase. Examples are aerobic oxidation of mono-alcohols, diols, glycerol, glucose, alkenes and alkanes. 

Resolution of bromohydrifts.2 Diastereoisomeric esters of bromohydrins with MTPA are readily separated by fractional crystallization and characterized by NMR. The optically pure bromo MTPA esters are convertible by known methods into chiral alcohols, diols, and epoxides, including arene oxides. 

Two tandem alkene metathesis-oxidation procedures using Grubb s second-generation ruthenium catalyst resulted in unique functional group transformations. Use of sodium periodate and cerium(III) chloride, in acetonitrile-water, furnished cis-diols. Oxidation with Oxone, in the presence of sodium hydrogencarbonate, yielded a-hydroxy ketones.296 Secondary alcohols are oxidized to ketones by a hydrogen... 

The C—Si bond formed by the hydrosilation of alkene is a stable bond. Although it is difficult to convert the C—Si bond to other functional groups, it can be converted to alcohols by oxidation with MCPBA or H2O2. This reaction enhances the usefulness of hydrosilylation of alkenes [219], Combination of intramolecular hydrosilylation of allylic or homoallylic alcohols and the oxidation offers regio- and stereoselective preparation of diols [220], Internal alkenes are difficult to hydrosilylate without isomerization to terminal alkenes. However, intramolecular hydrosilation of internal alkenes can be carried out without isomerization. Intramolecular hydrosilylation of the silyl ether 572 of the homoallylic alcohol 571 afforded 573 regio- and stereoselectively, and the Prelog-Djerassi lactone 574 was prepared by applying this method. 

A mixed oxide of ruthenium, copper, iron and alumnium has been developed as a catalyst for the synthesis of aldehydes and ketones from alcohols.258 Oxidation of chiral secondary 1,2-diols with 2,3-dichloro-5,6-dicyano-l,4-benzoquinone under ultrasound wave promotion leads to the selective oxidation of benzylic or allylic hydroxyl group. The configuration of the adjacent chiral centre is retained.259 The kinetics of oxidation of ethylbenzene in the presence of acetic anhydride have been studied.260... 

Heterogeneous oxidation of diols to lactones.1 A mixture of KMn04 and Cu-S04-5H20 is recommended for heterogeneous oxidation of 1,4- and 1,5-diols to lactones. This oxidation can be highly selective since primary alcohols are oxidized... 

Oxidations of Alcohols, Diols and Ketones with Fluorine... 

Aldehydes, RCHO (Sec. 7.9) (Sec. 7.9) (Sec. 8.4) (Sec. 17.7, 19.2) (Sec. 19.2, 21.6) from disubstituted alkenes by ozonolysis from 1,2-diols by cleavage with sodium periodate from terminal alkynes by hydroboration followed by oxidation from primary alcohols by oxidation from esters by reduction with DIB AH [HA1(i-Bu)2]... 

---