反应详情

An 82 g. portion (0.5 mole) of 5-nitrobenzimidazole in 1 L of ethanol is reduced over 5 g. of 5% palladium-charcoal catalyst containing 50% water. The reduction stops after a pressure drop of 97 psig. (97%) in 75 min. The catalyst is filtered, 108 g. (0.5 mole) of diethoxymethylenemalonate is added to the filtrate and the solution is boiled in an open flask until about one-half of the solvent has boiled away (ca. 2 hr.). The product sets to a solid cake upon cooling. Ethanol containing a little water is added to assist in breaking up the cake and the product is filtered, washed with cold ethanol-H2O (3:1) and air-dried; yield, 125 g. (83%). A 50 g. portion of this anil is added to 500 ml. of boiling Dowtherm over a 3-4 min. period and boiling is continued 4 min. longer. After cooling to room temperature the product is filtered, washed with Dowtherm, then benzene and air-dried; 44 g. of crude product is obtained. Extraction of this material with 500 ml. of boiling ethanol gives 22 g., m.p. 315°-316° C.

1. filtrationThe catalyst is filtered
2. customthe solution is boiled in an open flask until about one-half of the solvent
3. custom(ca. 2 hr.)
4. temperatureupon cooling
5. filtrationthe product is filtered
6. washwashed with cold ethanol-H2O (3:1)
7. customair-dried
8. customyield
9. additionportion of this anil is added to 500 ml
10. filtrationis filtered
11. washwashed with Dowtherm
12. dry with materialbenzene and air-dried
13. customof crude product is obtained
14. extractionExtraction of this material with 500 ml
15. customof boiling ethanol gives 22 g