5-bromo-1H-indazole → tert-butyl 4-(1H-indazol-5-yl)piperidine-1-carboxylate

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Reaction Steps

Into a 50-mL three neck round-bottom flask, which was purged and maintained with an inert atmosphere of nitrogen, was placed a suspension of Zn (990 mg, 15.1 mmol) in DMA (1 mL) A 7:5 v/v mixture of TMSCl/1,2-dibromoethane (0.12 mL) was added drop-wise at a rate to maintain the temperature below 65° C., then the mixture was stirred for an additional 10 min. A solution of tert-butyl 4-iodopiperidine-1-carboxylate (3.17 g, 10.2 mmol) in DMA (2 mL) was added drop-wise and stirred at 40-45° C. for 30 min. The resulting mixture was added to a mixture of 5-bromo-1H-indazole (1.00 g, 5.08 mmol), CuI (80 mg, 0.42 mmol) and Pd(dppf)Cl2 (260 mg, 0.36 mmol) in DMA (1 mL) in a 50-mL round-bottom flask under a nitrogen atmosphere. The resulting mixture was stirred overnight at 85° C., then cooled and diluted with ethyl acetate (50 mL) and washed with brine (3×20 mL), dried (Na2SO4), filtered, and concentrated under reduced pressure. The residue was purified by silica gel column chromatography with ethyl acetate/petroleum ether (1/5) as the eluent to yield the title compound as a yellow solid (200 mg, 12%).

Provenance & Evidence