To a mixture of 4-(5-bromo-3-methylpyridin-2-yl)piperazine-1-carboxylic acid tert-butyl ester (3.6 g), bis(tricyclohexylphosphine)palladium (II) dichloride (396 mg), tripotassium phosphate (12 g) and cyclopropylboronic acid (2.1 g) were added toluene (30 mL) and water (1.5 mL), and the mixture was refluxed for 8 hr. After cooling, the mixture was extracted with ethyl acetate, washed with saturated brine, and the solvent was evaporated. The residue was purified by column chromatography (chloroform) to give 4-(5-cyclopropyl-3-methylpyridin-2-yl)piperazine-1-carboxylic acid tert-butyl ester (2.2 g). 4-(5-Cyclopropyl-3-methylpyridin-2-yl)piperazine-1-carboxylic acid tert-butyl ester (2.2 g) was dissolved in chloroform (5 mL), 4N hydrogen chloride/ethyl acetate (5 mL) was added, and the mixture was stirred at room temperature overnight. Ethyl acetate (20 mL) was added, and the mixture was filtered to give the title compound (1.3 g).
