Scheme 4. Mechanistic consideration. Reagents and conditions: (eqn (1)) 1a (0.1 mmol), CuCl₂ (0.03 mmol), KI (0.05 mmol), DMSO (1 mL), 120 °C, 24 h, under air; (eqn (2)) 1a (0.1 mmol), 2a (0.05 mmol), CuCl₂ (0.03 mmol), KI (0.05 mmol), 1,1′-diphenylethylene (0.2 mmol), DMSO (1 mL), 120 °C, 24 h, under air.