Oxidation of alkoxide

The oxidation of alkoxides instead of alcohols is an alternative to achieve the desired oxidation. A spiro-cyclization of (5) occurred, when it was electrolyzed in EtOH containing both EtONa and LiBF4 to afford 61% of the spiroacetal (6)... 

Only a few of rather numerous reactions of oxidation of alkoxides by oxygen, peroxides, halogens, and other compounds may be used for synthesis of M(OR) (with considerable yields). These reactions are known for uranium alkoxides [197, 856], such as... 

Oxidation of Alkoxides in Air Vapors of aluminum iec-butoxide and silicon ethoxide (premixed or sequentially delivered) were oxidized in air at 700-1400°C for various times (64-170ms) and different. VFOj/SiO, ratio (mass%). 

Scheme 5. Rhenium-mediated oxidation of alkoxide and alkyl ligands.

The early transition metals are dissolved via a complex mechanism involving oxidation of alkoxide ligands with formation of extremely reactive alkoxo-radicals that in turn attack the metal, forming soluble alkoxide complexes already at the anode ... 

Acetone in conjunction with benzene as a solvent is widely employed. With cyclohexanone as the hydrogen acceptor, coupled with toluene or xylene as solvent, the use of higher reaction temperatures is possible and consequently the reaction time is considerably reduced furthermore, the excess of cyclohexanone can be easily separated from the reaction product by steam distillation. At least 0 25 mol of alkoxide per mol of alcohol is used however, since an excess of alkoxide has no detrimental effect 1 to 3 mols of aluminium alkoxide is recommended, particularly as water, either present in the reagents or formed during secondary reactions, will remove an equivalent quantity of the reagent. In the oxidation of steroids 50-200 mols of acetone or 10-20 mols of cyclohexanone are generally employed. 

The slow oxidation of primary alcohols, particularly MeOH, is utilized for the oxidation of allylic or secondary alcohols with allyl methyl carbonate without forming carbonates of the alcohols to be oxidized. Allyl methyl carbonate (564) forms 7r-allylpalladium methoxide, then exchange of the methoxide with a secondary or allylic alcohol 563 present in the reaction medium takes place to form the 7r-allylpalladium alkoxide 565, which undergoes elimination of j3-hydrogen to give the ketone or aldehyde 566. The lactol 567 was oxidized selectively with diallyl carbonate to the lactone 568 without attacking the secondary alcohol in the synthesis of echinosporin[360]. 

This reaction is important in the manufacture of long-chain alcohols by means of hydrolysis of the aluminum alkoxide. Examples of oxidation of metal alkoxides (40,42) include ... 

The same products may be made from primary alkoxides by the violent reaction with elementary chlorine or bromine. A radical mechanism has been proposed to account for the oxidation of some of the alkoxy groups (54) ... 

The oxidation of a hydroxyl group by an aluminum alkoxide-catalyzed hydrogen exchange with a receptor carbonyl compound is known as the Oppenauer oxidation. For oxidation of steroidal alcohols the reaction is generally... 

Spontaneous aerial oxidation of the initially formed alkoxide is reported in the reaction between a 7-lithiotriazolopyridine and pyridine-2-carboxaldehyde, to give ketone 144 (98T15287). 

In other studies, the combination of alkoxides and chlorides, or alkoxides and amides without oxidant have been used to deposit hafnium silicate thin films by ALD [3,7],... 

Srivastava DN, Perkas N, Seisen Bueva GA, Koltypin Y, Kessler VP, Gedanken A (2003) Preparation of porous cobalt and nickel oxides from corresponding alkoxides using a sonochemical technique and its application as a catalyst in the oxidation of hydrocarbons. Ultrason Sonochem 10(1) 1-9... 

After successful installation of the first two stereocenters, our attention was focused on elaboration of the terminal alkene in 64 (Scheme 6.9). Treatment with disiamylborane followed by oxidative workup afforded primary alcohol 65 in good yield (70-85 %). A side product containing a mixture of two diastereomers (66) was also observed and resulted from conjugate addition of the alkoxide formed during basic workup onto the unsaturated ester. Maintaining the temperature at 0 °C by a slow, dropwise quench during the oxidative workup was necessary to minimize the amount of the undesired cyclization product (66). Subsequent oxidation of the primary alcohol 65 using Dess-Martin periodinane [28] and a Pinnick oxidation afforded carboxylic acid 67 [29]. 

Addition of alkyllithium to cyclobutanones and transmetallation with VO(OEt)Cl2 is considered to give a similar alkoxide intermediates, which are converted to either the y-chloroketones 239 or the olefinic ketone 240 depending on the substituent of cyclobutanones. Deprotonation of the cationic species, formed by further oxidation of the radical intermediate, leads to 240. The oxovanadium compound also induces tandem nucleophilic addition of silyl enol ethers and oxidative ring-opening transformation to produce 6-chloro-l,3-diketones and 2-tetrahydrofurylidene ketones. (Scheme 95)... 

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