A mixture of 6,8-dibromoimidazo[1,2-a]pyrazine (12.5 mmol), 4-(4-amino-phenyl)-piperazine-1-carboxylic acid tert-butyl ester (12) (13.1 mmol), potassium carbonate (25 mmol), acetonitrile (50 mL) and N,N-dimethylacetamide (20 mL) is heated at 65° C. for 16 hrs. The mixture is cooled to room temperature, treated water (100 mL), and extracted with ethyl acetate (3×80 mL). The extracts are washed with water (3×60 mL) and brine (1×60 mL), dried over magnesium sulfate, and concentrated in vacuo. The residue is chromatographed over silica gel, eluting with ethyl acetate, to give 4-[4-(6-bromo-imidazo[1,2-a]pyrazin-8-ylamino)-phenyl]-piperazine-1-carboxylic acid tert-butyl ester (13) as a light brown foam.
