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 added 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 ~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