The general procedure for the synthesis of 3-propylpyridine from ethyl iodide was as follows: i) n-butyllithium (BuLi, 1.6 M hexane solution, 15.4 mL, 25 mmol) was added drop-wise to a tetrahydrofuran (THF, 35 mL) solution of diisopropylamine (3.53 mL, 24.7 mmol) at 0 °C. After 30 min, hexamethylphosphorotriamine (HMPA , 15.7 g, 24.7 mmol) was added and the mixture was kept at 0 °C for 15 min. Subsequently, a THF (10 mL) solution of 3-methylpyridine (2.3 g, 24.7 mmol) was added dropwise.After 30 min, a THF (10 mL) solution of ethyl iodide (EtI, 3.45 g, 24.7 mmol) was added dropwise.The reaction mixture was stirred for 1 h at room temperature. After completion of the reaction, the mixture was poured into 10% hydrochloric acid (HCl) solution. The aqueous phase was extracted with ether (Et2O), the organic phase was washed with water, dried over anhydrous sodium sulfate and concentrated under vacuum to give a yellow oily product (300 mg, 10% yield), which could be used in subsequent steps without further purification.
