Metal‐Free Ammonia Borane‐Catalyzed Hydroboration of Lactones and Esters to Alcohols.

Herein we describe an efficient methodology for metal‐free hydroborative cleavage of lactones and esters with HBPin (Pin=pinacol) to the corresponding alcohol derivatives using ammonia borane as a pre‐catalyst. The reactions proceed under mild conditions, can be performed in a solvent‐free manner, and do not require an inert atmosphere. Combined experimental and computational mechanistic studies suggest a novel mechanism that involves μ‐aminodiboranes as catalytically active species. [ABSTRACT FROM AUTHOR]