4,5-dibromo-N-(3-oxopropyl)-1H-pyrrole-2-carboxamide → 2,3-Dibromo-6,7-dihydropyrrolo[2,3-c]azepin-8(1H)-one

Participants

Reaction Steps

A solution of 12 (1.0 g, 3.3 mmol) in 10 mL of methanesulfonic acid was stirred at room temperature for 7 d. The reaction mixture was diluted with ether (500 mL), washed with sat. NaHCO3 (100 mL ×3) and sat. NaCl (100 mL). The organic layer was dried (MgSO4) and evaporated under reduced pressure. The resulting residue was purified by flash chromatography (CH2Cl2/MeOH 19:1) to give 13 (0.68 g, 80%) as a colorless solid: mp 170-175° C.; 1H NMR (CD3OD) d 3.57 (d, 2H, J=6.4), 6.01 (dt, 1H, J=10.1, 6.4), 6.65 (d, 1H, J=10.1); (DMSO-d6) d 3.46 (dd, 2H, J=6.4, 4.9), 6.03 (dt, 1H, J=10.0, 6.4), 6.54 (d, 1H, J=10.0), 7.75 (t, 1H, J=4.9), 13.04 (s, 1H); 13C NMR (CD3OD) d 39.6 (e), 100.2 (e), 108.4 (e), 126.4 (o), 126.7 (e), 126.8 (o), 127.0 (e), 164.6 (e); IR (nujol) 3184, 1639, 1603, 1541 cm−1; UV (CH3OH) 1max 288, 227 nm; MS, m/z (relative intensity) 308 (M++4, 30), 306 (M++2, 60), 304 (M+, 30), 225 (100), 200 (80), 182 (40), 170 (40); HRMS, calcd for C8H6N2OBr2 (M+) 303.8847, found 303.8833. Anal. Calcd for C8H6N2OBr2: C, 34.41; H, 1.98; N, 9.16; Found: C, 34.75; H, 2.09; N, 9.07.

Provenance & Evidence