Alcohols by reduction of aliphatic carbonyl compounds

The trapping by alkene bonds of radicals obtained in the reduction of aliphatic carbonyl compounds has proved to be a versatile route for the formation of carbon-carbon bonds. Reactions are carried out in protic solvents where the reactive species is the a-radical formed by protonation of the carbonyl radical anion. The competing reaction is reduction of the carbonyl group to the alcohol. 

SchifT s bases A -Arylimides, Ar-N = CR2, prepared by reaction of aromatic amines with aliphatic or aromatic aldehydes and ketones. They are crystalline, weakly basic compounds which give hydrochlorides in non-aqueous solvents. With dilute aqueous acids the parent amine and carbonyl compounds are regenerated. Reduction with sodium and alcohol gives 

Lower aliphatic amines are widely used as intermediates for the synthesis of herbicides, insecticides and drugs or can be applied as rubber accelerators, corrosion inhibitors, surface active agents etc. [l]. The most widespread method for the preparation of lower aliphatic amines involves the reaction of ammonia with an alcohol or a carbonyl compound in the presence of hydrogen. The most common catalysts used for reductive amination of alcohols, aldehydes and ketones contain nickel, platinum, palladium or copper as active component [ I — 3 ]. One of the most important issues in the reductive amination is the selectivity control as the product distribution, i.e. the ratio of primary to secondary or tertiary amines, is strongly affected by thermodynamics. 

The majority of aliphatic ketones give the secondary alcohol on reduction at electrodes of carbon, mercury, lead, or platinum. The usual choice of electrolyte has been dilute sulfuric acid, acetate buffer, or a neutral salt solution, which will become alkaline during the course of reaction that consumes protons. Relatively few studies have been recorded of the isomer ratio obtained by reduction of open chain ketones with a prochiral center adjacent to the carbonyl function [32,33]. Results are collected in Table 2, and one aromatic carbonyl compound is included here for convenience. In general, the erythro-alcohol is favored and in an excess over that present in the equilibrium mixture [32,33]. These results are explained in terms of adsorption of intermediates at the electrode surface. For many of the examples in Table 2, the total yield of alcohol is low and this result is not generally typical of aliphatic carbonyl compounds, as can be seen from Table 3. 

---