Reaction #9055

Reaction equation

2,3-diaminotoluene

trimethylorthoformate

trifluoroacetic acid

→

4-methyl-1H-benzimidazole

Solvents

CH2Cl2

CH2Cl2

Conditions

Workup

1. 1
   Washwashed consecutively with saturated aqueous NaHCO3 (40 mL) and H2O (40 mL)
2. 2
   DryingThe combined organic extracts were dried over MgSO4
3. 3
   Concentrationconcentrated to a rusty brown solid (1.07 g, 97%)

Procedure

To a stirred solution of 2,3-diaminotoluene (1.00 g, 8.2 mmol) in CH2Cl2 (82 mL) was added trimethylorthoformate (4.5 mL, 41 mmol) and trifluoroacetic acid (0.32 mL, 4.1 mmol) and the mixture stirred at room temperature for 24 h after which the reaction mixture was diluted with CH2Cl2 (200 mL), and washed consecutively with saturated aqueous NaHCO3 (40 mL) and H2O (40 mL). The aqueous layers were reextracted with CH2Cl2 (2×100 mL). The combined organic extracts were dried over MgSO4 and concentrated to a rusty brown solid (1.07 g, 97%). 1H NMR (300 MHz, CDCl3) δ 8.08 (s, 1H), 7.49 (d, 1H, J=8.1 Hz), 7.23–7.18 (m, 1H), 7.10 (d, 1H, J=7.5 Hz), 2.64 (s, 3H).

Source