Benzyltriethylammonium borohydride

Although the exact mechanism is speculative, it has been found that carboxylic acids, but not esters, are reduced directly to the corresponding alcohols on reaction with benzyltriethylammonium borohydride in the presence of trichlorosilane [21]. Yields are generally in excess of 85%. The failure of the system to reduce esters suggests that diborane is not produced during the reaction [22],... 

Cyclic enol ethers are reductively cleaved to produce a,to-diols using a stoichiometric amount of benzyltriethylammonium borohydride and chlorotrimethylsilane [30] acyclic enol ethers give saturated alcohols. 

Another synthetic route to 3-methylhasubanan (43), proposed by Lattes et al. (74), consists of the intramolecular aminomercuration (75) of amino-ethylphenanthrene 27. The key intermediate 27 was treated with mercury(II) acetate in THF/water to yield 9-acetoxymercury-3-methoxyhasubanan (46), as depicted in Scheme 3, and then the reaction product 46 was successively treated with benzyltriethylammonium chloride, sodium hydroxide, and sodium borohydride to furnish the target, 3-methylhasubanan (43) (74). 

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