Question

Draw the products formed when cholesterol is treated with [1] bh3·thf; [2] h2o2, −oh. indicate the stereochemistry around any stereogenic centers in the product.

Answer 1

Alkene on Hydration yield Alcohols. When Asymmetric Alkenes are treated with water in the presence of acid they follow Markovnikoff rule, and the Hydrogen of incoming reagent goes to that carbon which contain more number of Hydrogen atoms. The reverse (Anti-Markovnikoff) is done by carrying out Hydroboration reaction.In this case the Hydrogen atom of incoming reagent goes to that carbon which contains less number of Hydrogen atoms. In this reaction both -H and -OH adds in syn fashion. The Hydroboration reaction of Chloestrol is shown below,