A Direct Reduction of Aliphatic Aldehyde, Acyl Chloride, Ester, and Carboxylic Functions into a Methyl Group

Abstract

The aliphatic carboxylic group was efficiently reduced to the methyl group by HSiEt(3) in the presence of catalytic amounts of B(C(6)F(5))(3). To the best of our knowledge, this is the first example of a direct exhaustive reduction of aliphatic carboxylic function. Aliphatic aldehydes, acyl chlorides, anhydrides, and esters also underwent complete reduction under similar reaction conditions. Aromatic carboxylic acids, as well as other carbonyl functional equivalents, underwent smooth partial reduction to the corresponding TES-protected benzylic alcohols. It was shown that, unlike the reduction of aliphatic substrates, the exhaustive reduction of aromatic substrates was not straightforward: a concurrent Friedel-Crafts-like alkylation process competed with the reduction yielding trace to notable amounts of dimeric products, thus decreasing the overall selectivity of the reduction process.

Triethylsilane (TES)

“…(C) Recently, Longshaw and co-workers, while re-investigating the use of (TMS) 3 CH as mediator of radical reactions, observed that it does not function in this reaction. 10 However, in competition experiments, they noted that TES plays as a more effective reagent for this kind of reaction, since the abstraction of bromine from 1-bromoadamantane is exothermic for Et 3 Si, but endothermic for (TMS) 3 C. …”

“…10 However, in competition experiments, they noted that TES plays as a more effective reagent for this kind of reaction, since the abstraction of bromine from 1-bromoadamantane is exothermic for Et 3 Si, but endothermic for (TMS) 3 C. …”

“…Triethylsilane (TES or Et 3 SiH) is a versatile reagent in organic chemistry that can be used primarily as a hydride source in a series of reduction reactions, including etherification of carbonyls, 1 aldol reactions, 2 conversion of aliphatic carboxyl derivates in hydrocarbons, 3 and reduction of organic azides to amines 4 and nitro groups to hydroxylamines or amines. 5 TES also has great potential for use in radical reactions, performing as an alternative to the toxic Bu 3 SnH as hydrogen source.…”

A New Solvent‐Free Reaction for the Preparation of Alkoxysilane from Cyclic Ethers, Alcohols, or Carbonyl Compounds

“…Corriu et al described the alcoholysis of dihydro-and trihydrosilanes [1] with potassium carbonate, and Yamamoto et al reported the reduction of carbonyl groups to a methyl group by using triethylsilane and B(C 6 F 5 ) 3 . [2] Although silane derivatives give rise to harmless silica as the ultimate by-product, trichlorosilane, trialkylsilane, methoxysilane are expensive, toxic, and difficult to use. The use of polymethylhydrosiloxane (PMHS) and 1,1,3,3-tetramethyldisiloxane (TMDS), which are relatively nontoxic hydride donors, appears to be a good alternative for the reduction of several functions.…”

Synthesis of vinyl substitute poly(silphenylene‐siloxane) via silyl hydride‐dialkoxysilane process

“…Silyl hydrides/B(C 6 F 5 ) 3 , generally Ph 3 SiH/B(C 6 F 5 ) 3 or Et 3 SiH/B(C 6 F 5 ) 3 is a useful system in organic chemistry, particularly in the transformation of aldehydes, ketones, alcohol, carboxylic acids, and their derivatives into silyl ethers or hydrocarbons. [20][21][22][23][24][25][26][27][28][29] B(C 6 F 5 ) 3 catalyzed coupling reaction of silyl hydrides with alkoxysilanes was a newly developed methods to prepare linear polysiloxanes by Rubinsztajn and coworkers. 30,31 This reaction takes place at or below room temperature in the presence of very low levels of B(C 6 F 5 ) 3 .…”