[Cl:1][C:2]1[C:11]([I:12])=[CH:10][C:5]2[NH:6][C:7](=[S:9])[NH:8][C:4]=2[CH:3]=1.Br[CH2:14][C:15]([O:17][CH3:18])=[O:16].C([O-])([O-])=O.[Cs+].[Cs+]>C1COCC1>[Cl:1][C:2]1[C:11]([I:12])=[CH:10][C:5]2[N:6]=[C:7]([S:9][CH2:14][C:15]([O:17][CH3:18])=[O:16])[NH:8][C:4]=2[CH:3]=1A mixture of 6-chloro-5-iodo-2-thio-1H-benzo[d]imidazole (Intermediate 2; 4.00 g, 12.9 mmol), methyl bromoacetate (1.2 mL, 12.9 mmol), and Cs2CO3 (8.41 g, 25.8 mmol) in 65 mL of THF was stirred for 2.5 h at rt. The volume of the solvent was reduced by rotary evaporation to about 20 mL, the mixture was diluted with 200 mL of EtOAc and washed with brine, dried (MgSO4) and evaporated. The resulting residue was subjected to chromatography on an 80 g column of SiO2 eluting with 14% EtOAc in hexanes, followed by 20% to provide the title compound as an amorphous solid, which exists as a tautomer mixture in DMSO according to 1H NMR: 1H NMR (500 MHz, DMSO-d6): δ 3.66, 3.72, 3.73 (s each, 3H), 4.24, 4.25, 4.26 (s each, 2H), 7.71, 7.95 (s each, 1H), 7.99, 8.11, 8.22 (s each, 1H), 12.91 (br s, 1H); LC-MS: calculated for C10H8ClIN2O2S 382.6, observed m/e 382.9/384.9 (M+H)+.
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