Synthetic aspects; numbering follows the main manuscript. Synthesis of triflate (7) 1 A Schlenk tube was charged with 2-bromo-4,5-difluorophenol (1.64 ml, 3g, 1.44·10 -2 mol) under nitrogen and 9 ml of pyridine. The stirred solution is cooled to 0º C and then trifluoromethanesulfonic anhydride, 2.67 ml, is added very slowly through the rubber stopper via a syringe. The temperature is maintained at 0º C for 5 min and then allowed to warm to room temperature and stirred overnight (20-25 h). The

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... sulting mixture was poured into water and extracted with ethyl ether. The ether extract (upper phase) was washed sequentially with water, 10% aqueous hydrochloric acid solution (2x), water, and a concentrated sodium chloride solution, dried (MgSO 4 ), and concentrated to yield an oil. Chromatography (flash column, petroleum spirit 40-60ºC / EtOAc, 20:1) and solvent removing (rotavapor, 40º C, high vacuum, 3h, to remove all the EtOAc) afforded the desired product, 7, as a colourless liquid (3.2 g, 65%) 1 H-NMR (CDCl 3 , 400 MHz) δ ppm: 7.56 (t, J=8.46, 8.46 Hz, 1H); 7.28 (dd, J=6.85, 9.51 Hz, 1H).