1,5,6,7-Tetrahydro-4H-indol-4-one → Tetrahydroindole

Temperature

77.5 °C

4-oxo-4,5,6,7-tetrahydroindole 5.15 g (38.1 mmol) was gradually added to a stirred slurry of lithium aluminum hydride 4.0 g in anhydrous THF 0.45 L with cooling on ambient water bath, portion-wise, over 30 min period. The mixture was then placed on oil bath and refluxed under Ar on a 75-80° C. oil bath for 26 hours. The reaction mixture was cooled on ambient water bath, quenched by sequential addition of ethyl acetate 4 mL followed by dropwise water addition, 4 mL (very slowly, gas evolution), followed by 15% wt NaOH solution 12 mL followed by additional water 4 mL. The resulting slurry was stirred vigorously for 30 min, the salts were removed by filtration (the cake was washed thoroughly with THF) and the filtrates were concentrated on a rotovap. The oily residue was distilled on highvac using a short-path distillation apparatus, to provide 3.83 g (84%) of tetrahydroindole as oily liquid that turns yellow on light and air exposure, by 57-60° C./0.7 Torr.

1. temperaturewith cooling on ambient water bath
2. customThe mixture was then placed on oil bath
3. temperatureThe reaction mixture was cooled on ambient water bath
4. customquenched by sequential addition of ethyl acetate 4 mL
5. additionfollowed by dropwise water addition, 4 mL (very slowly, gas evolution),
6. customthe salts were removed by filtration (the cake
7. washwas washed thoroughly with THF) and the filtrates
8. concentrationwere concentrated on a rotovap
9. distillationThe oily residue was distilled on highvac

ORD record

ord-8463ead765c644d0a09616ea5ba51dd0

Source dataset

uspto-grants-2015_10

DOI

10.6084/m9.figshare.5104873.v1

Patent number

US09162981B2