Oppenauer oxidation primary alcohols

Selective oxidation of allylic alcohols.1 This zircononcene complex when used in catalytic amount can effect an Oppenauer-type oxidation of alcohols, including allylic ones, in the presence of a hydrogen acceptor, usually benzaldehyde or cyclohexanone. This system oxidizes primary alcohols selectively in the presence of secondary ones. Thus primary allylic alcohols are oxidized to the enals with retention of the configuration of the double bond in 75-95% yield. The method is not useful for oxidation of propargylic alcohols. 

The reduction of ketones to secondary alcohols and of aldehydes to primary alcohols using aluminum alkoxides is called the Meerw>ein-Ponndorf-Verley reduction. The reverse reaction also is of synthetic value, and is called the Oppenauer oxidation. ... 

Interestingly, when analogous phosphine adducts were tested, very poor catalytic activity was obtained (Table 10.4, entries 6 and 7). On the other hand, the NHC-cationic complex [IrCp (ITM)(NCMe)2][OTf]2 25 proved highly efficient for the Oppenauer-type oxidation of a large range of secondary as well as primary alcohols in acetone (e.g.. Table 10.4, entries 4, 5, 8-10). 

Hiroi et al. also reported the Cp lr complex-catalyzed Oppenauer-type oxidation of primary alcohols in acetone and butanone [31]. These authors prepared a novel Ir-ligand bifunctional catalyst 6 having an amido-alkoxo ligand, the... 

Maruoka s group also developed the extremely active aluminium compound 68,38 which in a proportion as low as 1 mol% is able to promote the oxidation of alcohols with pivalaldehyde or acetone at room temperature. Oppenauer oxidations employing catalyst 68 succeed in a variety of secondary and primary alcohols, providing yields of aldehydes and ketones above 80% in a consistent way. Only lineal primary aliphatic alcohols fail to be cleanly oxidized to the corresponding aldehydes. 

A common side reaction during Oppenauer oxidations consists of the base-catalyzed condensation of the carbonyl compound, resulting from the oxidation, with the carbonyl compound used as oxidant. Sometimes, advantage is taken from this side reaction for synthetic purposes. For example, oxidation of primary alcohols with an aluminium alkoxide and acetone results in the formation of an intermediate aldehyde that condenses with acetone, resulting in a synthetically useful formation of an enone.59... 

A selective oxidation of a secondary alcohol is achieved by the Oppenauer oxidation of a sterol. A primary alcohol is partially transformed in an aldehyde that condenses in situ with cylohexanone employed as oxidant. 

Other alkaloids isolated from Rhazya stricta include96 strictamine (168) and strictalamine (169). The structure and relative configuration of strictamine were confirmed by X-ray crystal structure analysis strictalamine is then (169), since reduction of (168) and (169) affords the same primary alcohol (170), with retention of stereochemical integrity at C-17. Conversely, Oppenauer oxidation of (170)... 

A zirconium complex, bis(cyclopenta(Uenyl)zirconium(IV) hydride will function as a catalyst for the chemoselective Oppenauer oxidation of primary alcohols in the presence of a hydrogen acceptor (cyclohexanone, benzaldehyde or benzophenone). This method appears to be of some value, since it also allows for the selective monooxidation of primary (and secondary) diols (Scheme 3). 1,2-Diols are not cleaved under these conditions and retro-aldol reactions appear not to be a problem. 

A modification of the Oppenauer oxidation which uses trichloroacetaldehyde on alumina provides a good, general oxidation of alcohols, and in particular will oxidize a secondary akdiol in the presence of a primary one, as shown by the examples given in Scheme 16. This method is claimed to be superiw to silver carbonate on Celite and much cheaper. Other advantages of this method are that it is neutral, nonaqueous, and halide, ester and lactone functionalities survive the reaction conditions. ... 

The secondary alcohols are oxidized to ketones by refluxing with aluminium isopropoxide, A1[0CH(CH3)2]3 [or Al(0-iPr)3], or potassium t-butoxide, KOC(CH3)3 [or KO-t-Bu]. A ketone such as acetone used in the reaction as refluxing agent is reduced to alcohol, 2-propanol. The reaction is known as the Oppenauer oxidation. The reverse reaction known as the Meerwein-Ponndorf-Verly reduction is the reduction of ketones to alcohols in the presence of alcohol such as 2-propanol. Potassium fert-butoxide can be used for the oxidation of primary alcohols. Aluminium isopropoxide in acetone is particularly used for... 

Oppenauer oxidation Oxidation of primary and secondary alcohols with ketones in the presence of metal alkoxides to afford the conesponding aldehydes and ketones. 320... 

Suzuki, T., Morita, K., Tsuchida, M., Hiroi, K. Iridium-Catalyzed Oppenauer Oxidations of Primary Alcohols Using Acetone or 2-Butanone as Oxidant. J. Org. Chem. 2003, 68, 1601-1602. 

Oppenauer oxidation In combination with p-nitrobenzaldehyde, (i-PrO) A1(0C0CF3) oxidizes secondary alcohols but not primary alcohols under the defined conditions (room temperature). 

The hydroxyl group in macralstonidine is contained in a primary alcohol function since Oppenauer oxidation gives an aldehyde, macral-... 

An important advantage of the Oppenauer oxidation of primary alcohols to aldehydes, over several traditional methods, is that over-oxidation towards carboxylic acids is prohibited. 

The zirconocene complex [2ZrH2] catalyses an Oppenauer-type oxidation of alcohols in the presence of an appropriate hydrogen acceptor. On oxidation of diols containing two primary alcohols, and of diols containing two secondary alcohol groups, one of the alcohol groups is selectively oxidized to form hydroxy-aldehydes and hydroxy-ketones respectively. This system... 

Nonsteroidal alcohols can, of course, be oxidized by this method. 42,143 jjj general, Oppenauer oxidation of primary alcohols gives low yields of aldehydes. Although oxidation of benzyl alcohol gave about 60% of... 

The Oppenauer oxidation with aluminium alkoxides provides an alternative method for the oxidation of secondary (and less commonly primary) alcohols. The reaction is the reverse of the Meerwein-Pondorff-Verley reduction (see Section 7.3). Typically aluminium triisopropoxide (or aluminium tri-tert-butoxide) is used, which serves to form the aluminium alkoxide of the alcohol. This is then oxidized through a cyclic transition state at the expense of acetone (or cyclohexanone or other carbonyl compound). By use of excess acetone, the equilibrium is forced to the right (6.45). 

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