PURPOSE: To efficiently obtain indoline in high yield, b catalytically hydrogenating indole in the presence of a specific inexpensive readily handleable nickel catalyst capable of being recycled and used for a long period with hardly any deterioration in catalytic activity under specific conditions in a relatively short time.
CONSTITUTION: Indole is catalytically hydrogenated in the presence of a nickel catalyst containing dry reduced diatomaceous earth as a carrier in an amount of 1W20wt.% based on the indole, as necessary, using a solvent, such as hexane, at 120W180°C under ≥20kg/cm2.G pressure of H2 for 1W2hr and the catalyst is then separated by a means, such as decantation or filtration. Distillation, etc., is subsequently carried out to afford the aimed indoline useful as a synthetic raw material for medicines, etc., intermediate compound for agricultural chemicals, etc. The separated catalyst and recovered unreacted indole are recycled for use. The above-mentioned nickel catalyst used is obtained by cooling the substance after dry reduction to replace H2 with CO2 gas and slowly adding air to slightly oxidize and stabilize the surface.
Nakamura, Takenori
Mizoi, Tomonao