Dialkynyldiboranes(4) and the selectable reactivity of their C–H, CC and B–B bonds

The synthesis and reactivity of dialkynyldiboranes(4), a little-studied family of diboranes, are presented herein. Three dialkynyldiboranes(4) were prepared via two different salt metathesis pathways. The three reactive sites of these dialkynyldiboranes(4) are then selectively addressed by judicious application of reagents: addition of an amine N-oxide leads to oxygen insertion into the B–B bond, dicobaltoctacarbonyl binds to the alkynyl CC bonds, while Sonogashira–Hagihara cross-coupling conditions lead to double C–C bond formation at the alkynyl C–H groups.