Cesium carbonate → tert-butyl 4-(2-amino-3-nitrophenyl)-5,6-dihydropyridine-1(2H)-carboxylate

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A solution containing 2-chloro-6-nitroaniline (0.83 g, 4.8 mmol), tert-butyl 4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-5,6-dihydropyridine-1(2H)-carboxylate (2.97 g, 9.6 mmol), and cesium carbonate (3.13 g, 9.6 mmol) in dioxane (32 mL) and water (6 mL) was degassed with nitrogen and tris(dibenzylideneacetone)palladium(0) (0.22 g, 0.24 mmol) was added followed by the addition of tri-t-butylphosphine tetrafluoroborate (0.139 g, 0.48 mmol). The mixture was stirred at room temperature for about 20 min then heated at about 80° C. for about 18 h. The solvent was removed in vacuo and the residue was partitioned between water (40 mL) and EtOAc (50 mL). The organic phase was washed with brine (40 mL), dried over magnesium sulfate, filtered and concentrated in vacuo. The residue was purified by silica gel chromatography eluting with 12% EtOAc:heptane to yield the desired product as a yellow solid (0.87 g, 2.7 mmol). Rf (25% EtOAc:heptane) 0.68.

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