Synthesis of Boron Analogues of Enamines via Hydroamination of a Boron−Boron Triple Bond

An N‐heterocyclic‐carbene‐stabilized diboryne undergoes rapid, high‐yielding and catalyst‐free hydroamination reactions with primary amines, yielding 1‐amino‐2‐hydrodiborenes, which can be considered boron analogues of enamines. The electronics of the organic substituent at nitrogen influence the structure and further reactivity of the diborene product. With electron‐rich anilines, a second hydroamination can occur at the diborene to generate 1,1‐diamino‐2,2‐dihydrodiboranes. With isopropylamine, the electronic influence of the alkyl substituent upon the diborene leads to an unprecedented boron‐mediated intramolecular N‐dearylation reaction of an N‐heterocyclic carbene unit.