Sterically Controlled Cobalt-CNC Catalyst System for Efficient 1,1-Diboration of Terminal Alkynes

1,1-diborylalkenes have emerged as versatile building blocks in organic synthesis, offering a straightforward and stereoselective approach to multisubstituted compounds. However, the direct 1,1-diboration of terminal alkynes using diboron reagents, which presents a simple pathway for constructing 1,1-diborylalkenes, has been limited by substrate scope and efficiency. In this study, we report a cobalt-catalyzed 1,1-diboration reaction of terminal alkynes employing B₂pin₂, facilitated by commercially available cobalt salts and readily accessible, air-stable CNC pincer ligands. By tuning the sterics of the ligands, this methodology enables the efficient functionalization of a broad range of terminal alkynes, including sterically hindered and electron-rich aryl-substituted substrates. The reaction is operationally simple, scalable to gram quantities, and demonstrates utility in the late-stage modification of bioactive compounds.