In a schlenk tube 50 ml, 2a (5 mmol, 2.5 equiv) was added. The tube was then closed with a rubber septum and sealed off with parafilm. Three cycles of evacuate-refill with nitrogen were performed to remove O2 and CHCl3 (20 mL, 1 M) was added, followed by three cycles of Freeze Pump Thaw to completely remove O2. After that, 1f (353 mg, 2.00 mmol, 1.00 equiv) was added under N2 atmosphere and the top of the schlenk tube was sealed again with parafilm .