3,4,5-Trichlorobenzene-1,2-diamine → 2-Amino-4,5,6-trichlorobenzimidazole

Participants

Reaction Steps

To a stirred solution of 3.62 mL of 5M BrCN/MeCN in 35 mL of H2O, was addrid dropwise a solution of 3,4,5-trichloro-1,2-phenylenediamine (13a) (3.478 g, 16.446 mmol) in 35 mL of MeOH. After the addition had been completed, stirring was continued at room temperature for 2 hr. The reaction mixture was concentrated to 18 35 mL and was washed with EtOAc (50 mL). The EtOAc phase was extracted with H2O (50 mL). The combined H2O phase was neutralized with sat. NaHCO3 solution to ~ pH 8 and the resulting suspension was extracted with EtOAc (150 mL). The EtOAc phase was washed with a mixture of sat. NaHCO3 and sat. NaCl solution (20 mL/130 mL), dried (Na2SO4), and evaporated. The residue was dissolved in MeOH, decolorized with charcoal, and then recrystallized from MeCN to give 3.098 g (2 crops, 80%) of 13b as a slightly grey crystals. MP: 255°-258° C. MS: (El) m/e 234.9473 (100%, M+ =234.9471). 1H NMR (DMSO-d6): d 11.25 (br s, 1, 1-NH), 7.29 {s, 1, 7(4)-H}, 6.75 (br s, 2, 2-NH2). Anal. Calcd. for C7H4Cl3N3 : C 35.55, H 1.70, N 17.77, Found: C 35.72, H 1.78, N 17.89.

Provenance & Evidence