a) Synthesis of 2-ethynyl-5-fluoropyridine: 5-fluoro-2-formylpyridine (1.10 g, 9.0 mmol) was dissolved in methanol (38 mL), potassium carbonate (2.44 g, 0.018 mol) was added followed by the slow dropwise addition of a solution of dimethyl (1-diazido-2-oxopropyl)phosphonate (2.03 g, 11 mmol) in methanol (12 mL). The reaction mixture was stirred at room temperature for 90 minutes. After completion of the reaction, the mixture was extracted with diethyl ether. The organic layers were combined, washed sequentially with 1 M sodium bicarbonate solution and saturated brine, dried over anhydrous sodium sulfate, filtered, and concentrated under reduced pressure at 0 °C to give a light brown liquid 2-alkynyl-5-fluoropyridine (1.01 g, 78% yield). Mass spectrum (MS): m/e = 121.0 [M]+.
