Phosphine Catalyzed Anti -Selective Diborylation of Ynones with an Unsymmetrical Diboron Reagent

Organoboron compounds are among the most versatile synthetic intermediates, yet the direct diborylation of ynones remains elusive because the corresponding α-boryl ketone intermediates are intrinsically unstable. Herein, this challenge is addressed through reagent design rather than increased reactivity. An electronically differentiated unsymmetrical diboron reagent selectively installs the less Lewis acidic Bmdan unit at the α-position, while N-methylation suppresses premature proton transfer from the diboron reagent. This combination enables the first phosphine-catalyzed anti-selective diborylation of ynones, providing electronically differentiated 1,2-diboryl enones with excellent regio- and stereoselectivities across a broad substrate scope. The resulting Bpin unit undergoes chemoselective derivatization while the Bmdan unit remains intact, highlighting the utility of electronically differentiated diboron reagents for accessing otherwise unstable α-boryl ketone motifs.