Intermolecular 1,2‐Aminoboration of Alkynes and the Critical Role of Electron‐Rich Alkynes

The intramolecular 1,2‐aminoboration of alkynes by aminoboranes is rare and invariably requires a catalyst to proceed, while the intermolecular aminoboration of alkynes is yet entirely unknown. Through an exploration of the significance of electronics in alkynes for activating the B−N σ‐bond of aminoboranes, we demonstrate in this work the first intermolecular 1,2‐aminoboration of alkynes. These reactions employ a series of (amino)dihaloboranes and aminoboronic esters, mild reaction conditions, and no catalysts, yielding syn ‐addition alkene products with the incorporation of two crucial functionalities: amino and boryl. While highly electron‐rich examples can afford the aminoborated products ( Z )‐2‐borylethenamines, other alkynes, including unactivated and less electron‐rich examples, do not lead to the corresponding aminoborated products due to the fundamental impediment that the reactions are significantly endergonic.