2-Aminopyridine → Ethyl imidazo[1,2-a]pyridine-2-carboxylate

Participants

Reaction Steps

To a solution of 2-aminopyridine (292, 1.1022 g; 11.71 mmol) and Bu2SnCl2 (431 mg; 1.3 mmol) in DME (20 mL), ethyl 3-bromopyruvate (1.56 mL; 11.16 mmol) was added to give an instant yellow precipitate. The suspension was stirred at room temperature for 2 h, then solid K2CO3 (2.6 g; 18.8 mmol) was added and the mixture stirred for additional 20 h at the same temperature. The reaction mixture was then diluted with ethyl acetate (200 mL) and washed with saturated aqueous sodium chloride. The organic layer was dried (MgSO4), filtered and concentrated. The residue was purified by flash chromatography on silica gel (eluent 50% ethyl acetate in dichloromethane), to afford the title compound 293 (1.31 g, 59% yield) as a white crystalline material. 1H NMR (400.2 MHz, DMSO) δ (ppm): 8.54 (m, 1H); 8.53 (d; J=0.9 Hz; 1H); 7.59 (ddd; J=1.3, 2.0, 9.2 Hz; 1H); 7.33 (ddd; J=1.3, 6.7, 9.2 Hz; 1H); 6.98 (dt; J=0.9, 7.8 Hz; 1H); 4.30 (q; J=7.0 Hz; 2H); 1.32 (t; J=7.0 Hz; 3H). MS: calc: 190.0; found: 191.1 (M+H).

Provenance & Evidence