Stoichiometric reductions of alkyl-substituted ketones and aldehydes to borinic esters

Abstract

A series of alkyl-substituted ketones are shown to activate hydrogen in the presence of B(C₆F₅)₃, affording the corresponding borinic esters RR′CHOB(C₆F₅)₂. The mechanism is shown to proceed via H₂ activation, hydride delivery and protonation of a C₆F₅ group. The aliphatic aldehyde Et₂CHCHO reacts with B(C₆F₅)₃ or BPh₃ to give boron enolates Et₂CCH(OBAr₂) (Ar = C₆F₅, Ph). These latter species are amenable to FLP-catalyzed reduction to the corresponding borinic esters.