Cesium carbonate → tert-butyl (3R)-3-methyl-4-(6-nitro-3-pyridyl)piperazine-1-carboxylate

Participants

Reaction Conditions

Reaction Steps

A 100-mL single-neck round-bottomed flask equipped with a magnetic stirrer and reflux condenser was charged with 1,4-dioxane (60 mL), 5-bromo-2-nitropyridine (2.0 g, 10.0 mmol), (R)-tert-butyl 3-methylpiperazine-1-carboxylate (2.0 g, 10.0 mmol), and cesium carbonate (6.5 g, 20 mmol). See FIG. 9. After bubbling nitrogen through the resulting mixture for 30 minutes, XantPhos (579 mg, 1.0 mmol) and tris(di-benzylideneacetone)dipalladium(0) (915 mg, 1.0 mmol) were added, and the reaction mixture was heated at 100° C. for 15 h. After this time the reaction was cooled to room temperature and filtered. The filtrate was partitioned between ethyl acetate (100 mL) and water (100 mL). The aqueous layer was separated and extracted with ethyl acetate (150 mL×3). The combined organic layer was washed with brine (50 mL) and dried over sodium sulfate. The drying agent was removed by filtration and the filtrate was concentrated under reduced pressure. The residue was purified on flash column eluting with 30:1 DCM/MeOH to afford 109a (1.6 g, 44%) as a yellow solid. MS: [M+H]+ 323. 1H NMR (500 MHz, DMSO) δ 8.21 (d, J=3.5, 1H), 8.18 (d, J=9.0, 1H), 7.43-7.45 (m, 1H), 4.33 (s, 1H), 3.92-3.99 (m, 1H), 3.80 (d, J=12.5, 2H), 3.06-3.23 (m, 3H), 1.43 (s, 9H), 1.09 (d, J=6.5, 3H).

Provenance & Evidence