A General, Practical Triethylborane-Catalyzed Reduction of Carbonyl Functions to Alcohols

A combination of the abundant and low‐cost triethylborane and sodium alkoxide generates a highly efficient catalyst for reduction of esters, as well as ketones and aldehydes, to alcohols using an inexpensive hydrosilane under mild conditions. The catalyst system exhibits excellent chemoselectivity and a high level of functional group tolerance. Mechanistic studies revealed a resting state of sodium triethylalkoxylborate that is the product of the reaction of BEt3 with sodium alkoxide. This borate species reacts with hydrosilane to form NaBEt3H, which rapidly reduces esters. Low‐cost alcohol: With abundant and low‐cost BEt3 as the catalyst, a selective, mild, and user‐friendly method is developed for the reduction of esters, ketones, and aldehydes into alcohols using an inexpensive hydrosilane. The mechanism involves in situ formation of NaBEt3H by hydride transfer from hydrosilane to sodium triethylalkoxyl borate (see scheme).