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An 82 g. (0.5 mole) sample of 5-nitrobenzimidazole in 900 ml of ethanol was reduced over 4 g. of 5% Pd/C catalyst containing 50% H2O. After a pressure drop of 108 lb. (calcd. 106 lb.), the reduction stopped. After filtration of the catalyst, 65 g. (0.5 mole) of ethyl acetoacetate, 20 g. of anhydrous calcium sulfate, and 0.5 ml of HOAc was added. After filtration of the anhydrous calcium sulfate the solution was concentrated in vacuo till till a solid remained. The product was filtered and washed with fresh ethanol and air-dried. The yield was 84 g. (69%), m.p. 160°-162°C.

1. filtrationAfter filtration of the catalyst, 65 g
2. filtrationAfter filtration of the anhydrous calcium sulfate the solution
3. concentrationwas concentrated in vacuo till till a solid
4. filtrationThe product was filtered
5. washwashed with fresh ethanol
6. customair-dried