A direct reduction of aliphatic aldehyde, acyl chloride, ester, and carboxylic functions into a methyl group

The aliphatic carboxylic group was efficiently reduced to the methyl group by HSiEt3 in the presence of catalytic amounts of B(C6F5)(3). To the best o f our knowledge, this is the first example of a direct exhaustive reduction of aliphatic carboxylic function. Aliphatic aldehydes, acyl chlorides, anh ydrides, and esters also underwent complete reduction under similar reactio n conditions. Aromatic carboxylic acids, as well as other carbonyl function al equivalents, underwent smooth partial reduction to the corresponding TES -protected benzylic alcohols. It was shown that, unlike the reduction of al iphatic substrates, the exhaustive reduction of aromatic substrates was not straightforward: a concurrent Friedel-Crafts-like alkylation process compe ted with the reduction yielding trace to notable amounts of dimeric product s, thus decreasing the overall selectivity of the reduction process.