Lithium tri-sec-butylborohydride, also known as L-selectride, is a metal hydride reagent t...

Lithium tri-sec-butylborohydride, also known as L-selectride, is a metal hydride reagent that contains three sec-butyl groups bonded to boron. When this reagent is used to reduce cyclic ketones, one stereoisomer often predominates as product. Explain why the reduction of 4-fert-butylcyclohexanone with L-selectride forms the cis alcohol as the major product.