To a mixture of 1-[1,1-dimethylethoxycarbonyl]-4-[3-amino-2-pyridinyl]piperazine (International Publication No. WO 88/08424, 5.40 g), cuprous chloride (1.00 g), copper powder (1.00 g), and dry dimethylformamide (25 ml) under nitrogen at 0° is added a solution of 3-chloro-3-methyl-1-butyne (2.00 g) in dry dimethylformamide (5 ml) in 4 portions over 15 min. The resulting mixture is then stirred at 20°-25° for 16 hrs, concentrated, and diluted with methylene chloride (75 ml) and water (20 ml). The layers are separated and the aqueous phase is extracted with methylene chloride (25 ml). The combined organic phase is washed with saline (20 ml), dried over anhydrous magnesium sulfate, and concentrated under reduced pressure to give a residue which is chromatographed on silica gel (70-230 mesh, 500 g), eluting with a gradient of ethyl acetate/hexane (10/90-20/80). Pooling of fractions giving an Rf =0.31 (ethyl acetate/hexane, 25/75) and removal of solvent under reduced pressure gives the title compound, NMR (CDCl3) 7.75, 7.47, 6.94, 4.61, 3.56, 3.00, 2.39, 1.64 and 1.48 δ.
