Potassium Tri sec-butyl hydroborate

Lithium tri(sec-butyl)hydroborate(l -) is a highly active reducing agent with exceptional stereoselectivity for reduction of ketones to alcohols.4 The potassium analog exhibits equal or greater stereoselectivity. 

Reactions were carried out in THF freshly distilled from lithium tetra-hydridoaluminate(l-) under nitrogen or argon.8 Since THF readily forms explosive hydroperoxides in contact with air, only THF from freshly opened bottles was used, and only a sufficient quantity for immediate use was distilled from the drying agent. 

A 125-mL flask equipped with a Teflon-covered magnetic stirring bar and an injection inlet closed by a serum stopper is dried in an oven (125° or higher), then cooled and purged with dry argon. Into this flask is weighed 

75 mmol of potassium hydride (10.0 gof 33 wt% dispersion in mineral oil ). The dispersion should be thoroughly stirred before weighing to ensure uniformity resegregation of the dispersion is slow enough not to interfere with weighing. 

Boron is determined by oxidation of tri(sec-butyl)borane to 2-butanol.911,12 A 4.0-mL aliquot of the potassium tri(sec-butyl)hydro-borate(l — ) solution is hydrolyzed by adding it, with stirring, to a mixture of 

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