Methanesulfonic Acid → 1-Ethyl-3-[5-hydroxy-7-(2-pyridyl)-1,3-benzothiazol-2-yl]urea
Reaction equation
C([O:8][C:9]1[CH:10]=[C:11]([C:24]2[CH:29]=[CH:28][CH:27]=[CH:26][N:25]=2)[C:12]2[S:16][C:15]([NH:17][C:18]([NH:20][CH2:21][CH3:22])=[O:19])=[N:14][C:13]=2[CH:23]=1)C1C=CC=CC=1.CS(O)(=O)=O>C(Cl)Cl>[CH2:21]([NH:20][C:18]([NH:17][C:15]1[S:16][C:12]2[C:11]([C:24]3[CH:29]=[CH:28][CH:27]=[CH:26][N:25]=3)=[CH:10][C:9]([OH:8])=[CH:23][C:13]=2[N:14]=1)=[O:19])[CH3:22]Participants
4
Procedure
To a stirred solution of ix (76 g, 0.187 mol) in DCM (1.7 L) was added methane sulfonic acid (270 mL, 4.17 mol) dropwise over 30 min. The mixture was stirred at RT for 3 h. The reaction was concentrated in vacuo. EtOAc (1 L) was added to the residue and this solution was poured carefully onto the crushed ice. The pH of the solution was modified to 8-9 by addition of saturated NaHCO3 solution followed by extraction with EtOAc (3×5 L). The combined organics were washed with H2O, brine, dried (Na2SO4), filtered and concentrated in vacuo. The residue was stirred in Et2O (1.0 L) for 1 h at RT and then filtered to obtain x (57.0 g, 97%). 1H-NMR (DMSO-d6, 400 MHz): δ 1.08 (t, J=7.20 Hz, 3H), 3.20 (m, 2H), 6.86 (br s, 1H), 7.0 (s, 1H), 7.46 (s, 2H), 7.96 (m, 1H), 8.10 (m, 1H), 8.76 (m, 1H), 9.59 (br s, 1H) and 10.41 (br s, 1H). MS: 315.06 [M+H]+.