N-bromobutanimide → Tert-butyl 1'-(5-bromopyrazin-2-yl)-4,4'-bipiperidine-1-carboxylate

The tert-butyl 1′-pyrazin-2-yl-4,4′-bipiperidine-1-carboxylate (16 mg, 0.046 mmol, prepared as described for Example 8) and N-bromosuccinimide (8.2 mg, 0.046 mmol) were dissolved in DMF (0.2 ml) and the solution stirred overnight at 50 C. The slurry was diluted with 15% brine:water (40 ml) and extracted with ethyl acetate (3×25 ml). The combined organic fraction was washed with brine, dried over magnesium sulfate, filtered, and the volatiles removed in vac. The crude material was purified by chromatography on silica gel with 20% acetone:hexanes to yield the title compound.