Formoxyboranes as hydroborane surrogates for the catalytic re-duction of carbonyls through transfer hydroboration

A new class of Lewis base stabilized formoxyboranes demonstrates the feasibility of catalytic transfer hydroboration. In the presence of a ruthenium catalyst, they have shown broad applicability for reducing carbonyl compounds. Various borylated alcohols are obtained in high selectivity and yields up to 99 %, tolerating several functional groups. Computational studies enabled to propose a mechanism of this transformation, revealing the role of the ruthenium catalyst and the absence of hydroborane intermediates.