General procedure for the Ni-catalyzed cross-electrophile coupling of pyridinium salts with bromoalkynes

An oven-dried 25-ml Schlenk tube equipped with a stir bar was charged with redox-active pyridinium salts 1 (0.2 mmol, 1.0 equiv), Ni(acac)₂ (0.02 mmol), 4-4′-di-tert-butyl-2,2′-bipyridine (0.02 mmol), and zinc flake (−325 mesh, 99.9%) (0.5 mmol). The tube was then evacuated and back-filled with argon (three times). Anhydrous DMF (1 ml) and bromoalkynes (0.3 mmol) were added under argon. The resulting mixture was allowed to stir for 8 hours under argon atmosphere at 60°C (oil bath). The reaction mixture was quenched with water and extracted with EtOAc. The organic layer was washed with water and brine and dried over Na₂SO₄. The organic layer was concentrated under vacuum by rotary evaporator in a water bath at 45°C. Flash column chromatography provided the product.