Nitrogen → 2-(5-Chloro-pyridin-3-yl)-indole-1-carboxylic acid tert-butyl ester

Participants

Reaction Steps

A flask is charged with N-Boc-indole-2-boronic acid (0.407 g, 1.55 mmol), 3-chloro-5-bromopyridine (0.200 g, 1.03 mmol), s-phos (0.021 g, 0.05 mmol), potassium phosphate (0.441 g, 2.07 mmol) and toluene (5 mL). The flask is evacuated and filled with N2 thrice and Pd2(dba)3 (0.019 g, 0.02 mmol) is added. The flask is evacuated and filled with N2 thrice. The mixture is refluxed for 1 h, then cooled to room temperature and filtered through celite. The filtrate is concentrated in vacuo to afford 2-(5-chloro-pyridin-3-yl)-indole-1-carboxylic acid tert-butyl ester as an oil. The residue is dissolved in DCM (5 mL) and trifluoroacetic acid (2 mL) is added. The reaction mixture is stirred at room temperature for 4 h, followed with quenching with a saturated sodium bicarbonate solution. Extraction with dichloromethane, drying of the organic layer over sodium sulfate and concentration in vacuo gives a residue which is purified by silica gel flash chromatography (heptane-ethyl acetate, 3:2) to afford 2-(5-chloro-pyridin-3-yl)-1H-indole. 1H NMR (400 MHz, MeOD) δ ppm 7.06 (s, 1H), 7.08 (d, J=7.8 Hz, 1H), 7.20 (t, J=7.7 Hz, 1H), 7.45 (d, J=8.3 Hz, 1H), 7.61 (d, J=7.8 Hz, 1H), 8.30 (t, J=2.1 Hz, 1H), 8.47 (d, J=2.3 Hz, 1H), 8.96 (d, J=1.8 Hz, 2H). HRMS (ESI) m/z 229.0542 [(M+H)+calcd for C13H10ClN2: 229.0533].

Provenance & Evidence