Couple 2-chloro-3-(4-chlorophenyl)-pyrazine (0.148 g, 0.710 mmol) and piperazine-1-carboxylic acid t-butyl ester (0.216 g, 1.16 mmol), using 2-(dicyclohexylphosphino)biphenyl (0.0321 g, 0.0916 mmol), tris(dibenzylideneacetone) dipalladium (0.0328 g, 0.0388 mmol), and the sodium salt of 2-methylpropan-2-ol (0.104 g, 1.09 mmol) in toluene (9 mL) at 82° C. for 17 hr. Cool the reaction to room temperature, dilute with diethyl ether (50 mL), filter through a 1 cm pad of silica gel, rinse the pad with diethyl ether (2×25 mL), combine the organic solutions, concentrate and purify (silica gel chromatography, eluting with 0:100 to 1:1 ethyl acetate:hexanes) to give 3′-(4-chloro-phenyl)-2,3,5,6-tetrahydro-[1,2′]bipyrazinyl-4-carboxylic acid t-butyl ester (0.143 g, 56%). MS (ES): m/z=303 [M+H-isobutylene]+.
