Sodium Carbonate → 5-Nitro-3',6'-dihydro-2'H-[2,4]bipyridinyl-1'-carboxylic acid tert-butyl ester

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Reaction Steps

To a mixture of N-Boc-1,2,3,6-tetrahydropyridine-4-boronic acid pinacol ester (1.52 g, 4.93 mmol), 2-bromo-5-nitropyridine (1.00 g, 4.93 mmol) and PdCl2(PPh3)2 (173 mg, 0.246 mmol) under nitrogen was added dioxane (30 mL) followed by 3 M aqueous Na2CO3 (4.93 mL, 14.8 mmol). The resulting mixture was degassed with a stream of nitrogen for 10 minutes then heated at reflux for 16 hours. On cooling, EtOAc (150 mL) was added and the resulting mixture was washed with water (3×50 mL) and brine (50 mL). The organics were dried (Na2SO4), filtered and concentrated under reduced pressure to give a brown solid that was purified by silica gel column chromatography (Biotage Isolera, 40 g SiO2 cartridge, 0-30% EtOAc in petroleum benzine 40-60° C.) to give the title compound I5 as a yellow solid (1.43 g, 95%); 1H NMR (400 MHz, CDCl3) δ 9.37 (dd, J=2.6, 0.5 Hz, 1H), 8.43 (dd, J=8.8, 2.7 Hz, 1H), 7.53 (d, J=8.8 Hz, 1H), 6.95-6.83 (m, 1H), 4.20 (d, J=3.0 Hz, 2H), 3.67 (t, J=5.6 Hz, 2H), 2.70-2.63 (m, 2H), 1.49 (s, 9H). LCMS-A: rt 6.140 min; m/z 304 [M−H]−.

Provenance & Evidence