3.8.6. Preparation of 2-((2,3-Dioxo-1,2,3,4-tetrahydroquinoxalin-6-yl)sulfonyl)-N-substituted Hydrazine-1-carbothioamide 8a,b

A solution of the sulfonohydrazide derivative 3 (2.56 g, 10 mmol) and the appropriate isothiocyanate, namely 4-methoxybenzene isothiocyanate and/or benzoyl isothiocyanate (10 mmol) in DMF (20 mL) containing a few drops of triethylamine, was heated under reflux for 6 h. After reaction completion, the mixture was poured onto an ice/H₂O mixture and neutralized with HCl. The formed ppt was collected by filtration, washed several times with water, and recrystallized from ethanol.

Yield (73%); mp203–205 °C; IR (KBr, cm⁻¹): 3433–3313 (4NH), 3035 (CH, aromatic), 2954 (CH-alicyclic), 1681 (2C=O), 1469 (C=S), 1327, 1172 (SO₂); ¹H NMR (DMSO-d₆, δ ppm): 3.81 (s, 3H, OCH₃), 6.90, 7.31, 7.52, 7.64 (4d, 6H, aromatic-H, J = 8.01 Hz), 8.13 (s, 1H, aromatic-H), 10.71, 11.32, 11.97 (3s, 5H, 5NH, exchangeable with D₂O); ¹³C NMR (DMSO-d₆, δ ppm): 55.44 (CH₃), 113.63, 113.78, 113.91, 114.01, 114.11, 114.22, 114.27, 118.11, 118.21, 127.09, 134.68, 153.69 (aromatic-C), 155.60 (C=O), 174.98 (C=S); MS, m/z (%): 422 [M⁺ + 1] (25.38), 421 [M⁺] (17.39); Analysis for C₁₆H₁₅N₅O₅S₂ (421.45), Calcd.: %C, 45.60; H, 3.59; N, 16.62; S, 15.21; Found: %C, 45.74; H, 3.65; N, 16.85; S, 15.49.

Yield (75%); mp. 265–267 °C; IR (KBr, cm⁻¹): 3460–3417 (4NH), 3093 (CH, aromatic), 2955 (CH-alicyclic), 1795–1681 (3C=O), 1489 (C=S), 1384, 1172 (SO₂). ¹H NMR (DMSO-d₆, δ ppm): 7.51–7.75 (m, 3H, aromatic-H), 7.80−8.05 (m, 4H, aromatic-H), 8.14 (s, 1H, aromatic-H), 10.71, 11.32, 11.97 (3s, 5H, 5NH, exchangeable with D₂O); ¹³C NMR (DMSO-d₆, δ ppm): 115.32, 120.27, 122.73, 125.36, 126.06, 127.39, 129.52, 131.72, 132.35, 133.76, 134.68, 136.27 (aromatic-C), 155.60, 156.58 (2C=O), 180.36 (C=S); MS, m/z (%): 419 [M⁺] (23.18); Analysis for C₁₆H₁₃N₅O₅S₂ (419.43), Calcd.: %C, 45.82; H, 3.12; N, 16.70; S, 15.29; Found: %C, 45.97; H, 3.38; N, 16.48; S, 15.36.