Reduction of Ethyl Indoxylate. I. Catalytic Reduction of Acetyl Derivatives of Ethyl Indoxylate

The high-pressure catalytic hydrogenation of the acetyl derivatives of ethyl indoxylate was investigated. Under 85 atms. of hydrogen atmosphere at 100∼110°, nickel catalyst converted ethyl 3-acetoxyindole-2-carboxylate (V) into ethyl 3-acetoxy-4, 5, 6, 7-tetrahydroindole-2 -carboxylate (IX), and ethyl 1-acetyl-3-acetoxyindole-2-carboxylate (VI) into ethyl 1-acetylindoline-2-carboxylate (XI), but ethyl 1 -acetylindoxylate (VIII) was hydrogenated to ethyl 1-acetyl-3-hydroxyindoline-2-carboxylate (XIII) at 60 atms. and 60°, and to ethyl 1-acetyl-3-hydroxyoctahydroindole-2-carboxylate (XIX) at 150 atms. and 110∼120°.