Into a 500-mL three-necked flask fitted with a J-KEM type-T temperature probe, overhead stirrer, reflux condensor, and nitrogen inlet was added (4-chloro-2-pyridin-3-yl-thiazol-5-yl)-ethyl-amine hydrochloride (20.0 g, 72.4 mmol green solid) and dichloromethane (150 mL). To this suspension was added pyridine (14.32 g, 181 mmol, 2.5 eq) (portionwise over 1 min to form a dark green-black solution. To this solution was added DMAP (4.4 g, 36 mmol) followed by 2-methyl-3-methylthiopropanoyl chloride (16.5 g, 108.6 mmol), which was added portionwise over 1 minute. The reaction exotherm went from 20° C. to 31° C. during the addition of the acid chloride. The reaction was heated to 35° C. for 10 hours then cooled to 25° C. for 14 h. To the dark brown reaction mixture was added dichloromethane (200 mL) and the solution was transferred to a 500 mL separatory funnel. The solution was washed with water (100 mL) and the layers were separated. The brown aqueous layers was extracted with dichloromethane (50 mL) and the dark brown dichloromethane extracts combined, washed with brine (100 mL), dried (MgSO4), filtered and rotary evaporated. This gave 30.49 g (74% pure by HPLC at 254 nm) of a crude black oil. The crude product was purified by silica gel chromatography (0 to 100% ethyl acetate/hexanes) to afford a beige solid (23.2 g, 89%): mp 79-81° C.; 1H NMR (300 MHz, CDCl3) δ 9.11 (d, J=1.7 Hz, 1H), 8.71 (d, J=4.8 Hz, 1H), 8.27-8.13 (m, 1H), 7.42 (dd, J=8.0, 4.9 Hz, 1H), 3.90 (bs, 1H), 3.69 (bs, 1H), 2.80 (bs, 2H), 2.47 (bs, 1H), 2.02 (s, 3H), 1.21 (q, J=7.3 Hz, 6H); ESIMS m/z 356 (M+1).
