a) General procedure for the synthesis of 2,2-dimethyl-N-(pyridin-4-yl)propionamide: 4-Aminopyridine (2 g, 21.3 mmol) was dissolved in dichloromethane (20 ml), to which pentanoyl chloride (3.1 ml, 25.6 mmol) and triethylamine (8.9 ml, 63.9 mmol) were added sequentially dropwise at room temperature. The reaction mixture was stirred at room temperature for 15 h. The reaction was subsequently quenched by addition of water. The organic layer was extracted with ethyl acetate and the combined organic layers were washed with saturated sodium chloride solution (50 ml), dried over anhydrous sodium sulfate, filtered and concentrated under reduced pressure. The residue was purified by silica gel column chromatography with dichloromethane:methanol (20:1, v/v) as eluent. The fraction containing the target product was collected and concentrated to afford N-(pyridin-4-yl)trimethylacetamide as a white solid (3.6 g, 95% yield).1H-NMR (CDCl3, 300 MHz) data were as follows: δ= 8.47 (d, J = 6.1 Hz, 2H), 7.79 (br s, 1H), 7.52 (d, J = 6.0 Hz, 2H), 7.52 (d, J = 6.0 Hz, 2H). 1.32 (s, 9H).
