Triethylamine → N-(2,3-dihydrobenzo[b][1,4]dioxin-6-yl)-1,4-dimethyl-2,3-dioxo-1,2,3,4-tetrahydroquinoxaline-6-sulfonamide

1,4-dimethyl-2,3-dioxo-1,2,3,4-tetrahydroquinoxaline-6-sulfonyl chloride (example 6-3a, 450 mg, 1.6 mmol) was added to a stirred solution of the 2,3-dihydrobenzo[b][1,4]dioxin-6-amine (215 mg, 1.4 mmol) and triethylamine (170 mg, 1.7 mmol) in dichloromethane (10 mL). The reaction was stirred at ambient temperature overnight then concentrated. The crude product was purified by silica gel chromatography (0-30% ethyl acetate in hexanes) to provide N-(2,3-dihydrobenzo[b][1,4]dioxin-6-yl)-1,4-dimethyl-2,3-dioxo-1,2,3,4-tetrahydroquinoxaline-6-sulfonamide as a white solid. MS (M+H, 404.10); 1H NMR (400MHz, DMSO-d6): δ, ppm: 3.47 (s, 3H), 3.49 (s, 3H), 4.12 (m, 4H), 6.55 (m, 1H), 6.61 (d, J=2.4 Hz, 1H), 6.69 (d, J=8.4 Hz, 1H), 7.53 (m, 1H), 7.59 (d, J=2 Hz, 1H), 10.00 (s, 1H).