In an oven-dried flask were charged 2-fluoro-3-iodopyrazine (0.829 g, 3.70 mmol), 1,1′-bis(diphenylphosphino)ferrocene]dichloride palladium(ii)complex with dichloramethane (0.091 g, 0.111 mmol), copper(i) iodide (0.042 g, 0.222 mmol), and DMA (3 mL). The resulting mixture was degassed with alternating vacuum/nitrogen purges. The (1-(tert-butoxycarbonyl)piperidin-4-yl)zinc(II) iodide (1.951 g, 5.18 mmol) solution from previous step was filtered into the mixture. It was degassed one more time and then heated to 80° C. with stirring for 16 h. After cooling to RT, the reaction mixture was treated with methyl tert-butylether (13 ml) and 1 N NH4Cl (13 ml). The organic layer was partitioned between EtOAc and 1 N NH4Cl and the aqueous layer was back extracted with EtOAc (2 x). The combined organic layer was washed with water, brine, dried (Na2SO4) and concentrated. The crude material was chromatographed through a Redi-Sep pre-packed silica gel column (40 g), eluting with a gradient of 0% to 20% EtOAc in hexane, to provide tert-butyl 4-(3-fluoropyrazin-2-yl)piperidine-1-carboxylate as orange oil. MS (ESI, pos. ion) m/z: 226.0 (M−56).
