Structural and electronic control of the bidentate 1-(2-pyridyl)benzotriazole ligand in copper chemistry with application to catalysis in the A3 coupling reaction

The hybrid bidentate 1-(2-pyridyl)benzotriazole (pyb) ligand was introduced into 3d transition metal catalysis. Specifically, [CuII(OTf)2(pyb)2]·2?CH3CN (1) enables the synthesis of a wide range of propargylamines by the A3 coupling reaction at room temperature in the absence of additives. Experimental and high-level theoretical calculations suggest that the bridging N atom of the ligand imposes exclusive trans coordination at Cu and allows ligand rotation, while the N atom of the pyridine group modulates charge distribution and flux, and thus orchestrates structural and electronic precatalyst control permitting alkyne binding with simultaneous activation of the C-H bond via a transient CuI species.