Hydrochloric Acid → 5-Amino-4,5,6,7-tetrahydrobenzimidazole dihydrochloride

Participants

Reaction Conditions

Reaction Steps

Add 5% Rh/C (5.215 g) to a 500 ml glass Parr bottle. Purge the bottle with nitrogen and wet the 5% Rh/C with 3 N HCl (50 ml). Then add 6-nitro-1H-benzoimidazole (10.354 g, 0.0635 mol) and 3N HCl (100 ml) to the purged bottle. Seal the Parr bottle and purge the reaction vessel with nitrogen (3×) and with hydrogen (3×). Then pressurize the reaction mixture with hydrogen (60 psig), seal the vessel but add hydrogen as needed to maintain 60 psig, agitate the reaction and heat to 80° C. Continue the reaction for 24 hours then turn off the heat and allow the reaction mixture to cool to ambient temperature. Vent the excess hydrogen from the vessel, purge the vessel with nitrogen (3×) and filter the reaction mixture to remove the 5% Rh/C catalyst. The filtrate is concentrated to dryness on a rotary evaporator and then under high vacuum. Dissolve the solid residue in 20 mL of methanol, heat to approximately 60° C. and add additional methanol (approximately up to 10 mL or as needed) to dissolve the residue completely. Cool the solution to room temperature and add ether (40 mL). A white solid separates, filter and dry under high vacuum to give the product (8.gm).

Provenance & Evidence