Fig. 2 Substrate scope of oxidative [4 + 2] annulation of styrenes with alkynes. Reaction conditions: alkene 1 (0.26 mmol), alkyne 2 (0.2 mmol), Acr + -Mes ClO 4 − (3 mol%), Co(dmgH) 2 py 2 PF 6 (8 mol%) in DCE (14 mL), 3W blue LEDs, 24 h; isolated yields are shown. * 0.2 mmol alkene and 0.6 mmol alkyne were