To a solution of 4-(3-chloro-pyrazin-2-yl)-piperidine-1-carboxylic acid tert-butyl ester (39) (297 mg, 1 mmol) and piperidin-4-yl-methanol (35) (126.5 mg, 1.1 mmol) in DMSO (6 mL) was added Et3N (202 mg, 2 mmol). The reaction mixture was stirred at 100° C. overnight. The reaction mixture was diluted with water, extracted with EtOAc (30 mL×3). The combined organic extracts were washed with water (30 mL) and brine (30 mL), dried over Na2SO4 and filtered. The filtrate was evaporated in vacuo and the residue was purified by flash column chromatography on silica gel to give compound (40) (302 mg, 0.8 mmol, yield 80.32%).
