Reduction carbon-oxygen double bonds

The most established of bioreduction processes focuses on carbon-oxygen double bond reduction. For example, alcohol dehydrogenases (ADHs), which can even catalyze the reduction of sterically demanding substrates such as 2-hydroxy ketones, can be used effectively [8]. The mild conditions of the enzymatic reaction mean that... 

Neither sodium borohydride nor lithium aluminum hydride reduces isolated carbon-carbon double bonds This makes possible the selective reduction of a carbonyl group m a molecule that contains both carbon-carbon and carbon-oxygen double bonds... 

Reduction of aldehydes and ketones usually occurs by the addition of hydrogen across the carbon-oxygen double bond to yield alcohols, but reductive conversion of a carbonyl group to a methylene group requires complete removal of the oxygen, and is called deoxygenation. 

Although the addition of t-BuMgCl to benzophenone had been reported [43] to yield 63% of the expected tertiary alcohol, 1,1-diphenyl-2,2-dimethyl-1-propanol, diphenyl-t-butylcarbinol (no reduction products, such as benzhydrol and benzopinacol, were found then), it was shown that besides the normal addition to the carbon-oxygen double bond, 1,2-addition and also 1,6-addition had taken place, leading to the formation of an alkyldihydrobenzophenone [44] (Scheme 9) ... 

Hydrogenation of ketones in alkaline medium at room T and atmospheric P, catalyzed by [Rh(2,2 -bipyridine) (diene)]PFg type complexes occurs with selectivity for reduction of carbon-oxygen double bonds to hydroxyl groups even in the presence of olefinic bonds. The system acts as a hydrogenolysis catalyst for molecular O2, and hydrogenation activity is retained even if large amounts of 62 are present. ... 

Catalytic reduction of a carbon-oxygen double bond is generally more difficult than that of an olefinic one. This experience is probably related to the following two factors, among others ... 

Solodar studied the reduction of piperitenone (8), a compound containing two different olefinic bonds and a prochiral carbon-oxygen double bond. He found that mainly the sterically less hindered C=C bond was favored in the hydrogenation reaction, and thus pulegone was the major product, but also other compounds were formed in minor amounts. 

The most common type of reduction reaction over solid supports is hydrogenation [98, 99]. However, as this class of reaction involves hydrogen in the gas phase, it does not fall within the bounds of this chapter. In liquid phase processes the most widely investigated type of reaction is the reduction of compounds containing carbon-oxygen double bonds. Ketones and aldehydes are readily reduced by a number of methods using solid catalysts or supported reagents [100]. 

Because the metal (e.g., Pt, Pd, Ni) catalyzed reduction of a carbon-carbon double bond is more facile than that of the carbon-oxygen double bond, unsaturated alde-... 

In this case, both carbon-oxygen double bonds are in the same product molecule, which means that the starting material must be a cycUc alkene.The product contains carboxylic acids, so we know that an oxidative workup is required. A reductive workup would give an aldehyde. 

We have seen reduction of carbonyl compounds before. In Chapter 14 (p. 645), we encountered the Clemmensen and Wolff-Kishner reductions in which a carbon—oxygen double bond is reduced all the way to a methylene group. 

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