Alanes carboxylic acids

Alane (AIH3) and its derivatives have also been utilized in the reduction of carboxylic acids to primary alcohols. It rapidly reduces aldehydes, ketones, acid chlorides, lactones, esters, carboxylic acids and salts, tertiary amides, nitriles and epoxides. In contrast, nitro compounds and alkenes are slow to react. AIH3 is particularly useful for the chemoselective reduction of carboxylic acids containing halogen or nitro substituents, to produce the corresponding primary alcohols. DIBAL-H reduces aliphatic or aromatic carboxylic acids to produce either aldehydes (-75 °C) or primary alcohols (25 C) Aminoalu-minum hydrides are less reactive reagents and are superior for aldehyde synthesis. ... 

Aromatic and aliphatic A,iV-dialkyl carboxylic acid amides, carboxylic esters, and free carboxylic acids are converted into aldehydes by diisobutyl-alane if reduction is carried out at low temperatures (0°C or — 70°C) 269, 279, 280, 286) ... 

Esterification s. Carboxylic acid esters from carboxylic acids, Redoxesterification Esters, active s. Carboxylic acid esters, active Etherates s. Alane etherates Ethers (s. a. Alkoxy...,... 

Subst. carboxylic acid amides from isocyanates Reactions with alanes... 

Two synthetic routes were employed by Alan Ardis in 1947. The first route involved the pyrolysis of an alkyl-3-acyloxy-2-cyanopro-pionate to yield an alkyl-2-cyanoacrylate plus a carboxylic acid. 

In dicarboxylic acids with one free and one esterified carboxyl group the free carboxyl only may be reduced with hydrides (alanes, boranes). The monoethyl ester or adipic acid was converted by an equimolar amount of borane in tetrahydrofuran at —18° to 25° to ethyl 6-hydroxyhexanoate in 88% yield [971] Procedure 19, p. 209). 

AIH3 and alkyl derivatives are powerful Lewis acidic reducing agents that rapidly convert carboxylic esters into primary alcohols. In many cases, the reduction may be stopped at the intermediate aldehyde stage, providing that the stoichiometry and temperature are carefully controlled. However, complete reduction is experimentally easier to carry out. DIBAL-H is the most useful and widely used alane. 

The mechanism of carboxylation of pyruvic acid (the Wood and Workman reaction ) remained obscure for many years. In 1948 Ochoa, with Alan Mehler and Arthur Kornberg, discovered the first enzyme system which fixed COj to pyruvic acid. It produced malic acid. The enzyme, first obtained from liver extracts, was called malic enzyme (see Fig. 1). The reaction proved to be reversible, producing pyruvic from malic acid. The enzyme serves, as do similar reactions discovered since then, to replenish the citric acid cycle intermediates ( anaplerotic reactions). In so doing it is of vital importance in the intermediary metabolism of animal and bacterial cells. 

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