Carboxylic acids, reduction

Nitriles are similar in some respects to carboxylic acids and are prepared either by SN2 reaction of an alkyl halide with cyanide ion or by dehydration of an amide. Nitriles undergo nucleophilic addition to the polar C=N bond in the same way that carbonyl compounds do. The most important reactions of nitriles are their hydrolysis to carboxylic acids, reduction to primary amines, and reaction with organometallic reagents to yield ketones. 

Access to the corresponding enantiopure hydroxy esters 133 and 134 of smaller fragments 2 with R =Me employed a highly stereoselective (ds>95%) Evans aldol reaction of allenic aldehydes 113 and rac-114 with boron enolate 124 followed by silylation to arrive at the y-trimethylsilyloxy allene substrates 125 and 126, respectively, for the crucial oxymercuration/methoxycarbonylation process (Scheme 19). Again, this operation provided the desired tetrahydrofurans 127 and 128 with excellent diastereoselectivity (dr=95 5). Chemoselective hydrolytic cleavage of the chiral auxiliary, chemoselective carboxylic acid reduction, and subsequent diastereoselective chelation-controlled enoate reduction (133 dr of crude product=80 20, 134 dr of crude product=84 16) eventually provided the pure stereoisomers 133 and 134 after preparative HPLC. 

Reduction of Carboxylic Acids by Carboxylic Acid Reductase 297 Whole-cell Carboxylic Acid Reduction... 

Halo-carboxylic acids, reduction by trivalent uranium, 34 80... 

Carbonochloridic acid, methyl ester, 65, 47 Carboxylic acids, reduction, 66, 160... 

Carbonylative coupling reaction, 68, 116 3-Carboxy-5-dodecen-2-one, (E), 68, 210 Carboxylation, vicinal di-, 68, 41 Carboxylic acids, reduction, 66, 160... 

Fig. Oxidation of alkyl side chains to aromatic carboxylic acids. Reduction...

Reactions of Nitriles Nitriles undergo acidic or basic hydrolysis to amides, which may be further hydrolyzed to carboxylic acids. Reduction of a nitrile by lithium aluminum hydride gives a primary amine, and the reaction with a Grignard reagent gives an imine that hydrolyzes to a ketone. 

Alcohols containing heterocyclic nuclei, halo, and alkoxyl groups as well as double bonds may be prepared. Without doubt, this is the best general procedure for the formation of the primary alcohol grouping from compounds at the oxidation level of a carboxylic acid. Reductions by this reagent were reviewed in 1951. °°... 

Finally, some of the methods for carboxylic acid reduction (Section 1.12.2) have also been applied to esters. Thus, the ethyl ester of thiazole-2-caiboxylic acid has been reduced electrochemically to the corresponding aldehyde, and some of the high temperature metal oxide catalyzed hydrogenations have been used on esters. ... 

NBH, in the presence of carboxylic acids. Reduction with sodium cyanoborohydride gives reduction but no alkylation under similar conditions. The reduction of 5-nitroisoquinoline produced dihydroiso-quinoline (27) or tetrahydroisoquinoline (28) with NBH in acetic acid, depending on the solvent and temperatures employed. 

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