1: With 2-fluoro-pyridine; trifluoromethylsulfonic anhydride in dichloromethane T=-78 - 0°C; Inert atmosphere; 2: With triethylsilane in dichloromethane T=0°C; Inert atmosphere; 3: With citric acid in tetrahydrofuran; dichloromethane; water T=45°C; 2 h; chemoselective reaction;