51-17-2

3752-24-7

The general procedure for the synthesis of 4,5,6,7-tetrahydro-1H-benzimidazole from benzimidazole was as follows: a suspension of benzimidazole (3.0 g, 25.4 mmol) with Pd/C (Degussa 5 wt%; 1.3 g) in acetic acid (50 mL) was added to a Parr reactor, and the reaction was carried out at 80 °C and 200 psi hydrogen pressure overnight. Upon completion of the reaction, the mixture was cooled to room temperature, filtered through diatomaceous earth and the diatomaceous earth pad was washed several times with distilled water. The filtrates were combined and the pH was adjusted to 9 with solid K2CO3, followed by liquid-liquid separation by addition of ethyl acetate. The organic layer was dried over anhydrous magnesium sulfate and concentrated under reduced pressure to give 4,5,6,7-tetrahydro-1H-benzimidazole (2.4 g, 77% yield) as a white solid. The product was characterized by 1H NMR (400 MHz, CDCl3): δ 1.82-1.85 (m, 4H), 2.06-2.10 (m, 4H), 7.55 (s, 1H), 10.21 (br s, NH).LC-MS (ES+) analysis showed m/z 123 ([M+H]+) and retention time (RT) was consistent with the solvent front (method A).