Hydrochloric Acid → 1,2,3,3a,4,8b-Hexahydrocyclopenta[b]indole

A mixture of 1,2,3,4-tetrahydrocyclopenta[b]indole (11 mmol, 1.8 g), 5% Pd/C (0.5 g), and concentrated hydrochloric acid (1.2 mL) was hydrogenated at 45 psi on a Parr shaker. After 3 h, the mixture was removed from the shaker and filtered through Celite. The solid bed was washed with methanol. The filtrate was concentrated. The crude oil was dissolved in 1 N HCl and washed with ether. The aqueous phase was treated with 2.5 N NaOH to pH>10 and then extracted with chloroform. The combined chloroform extracts were dried over MgSO4, filtered and concentrated to give the crude indoline. The material was purified by flash column chromatography through silica gel (Biotage, elution with 10% ethyl acetate-hexanes) to give the known indoline (7.6 mmol, 1.2 g, 69%) as a clear oil.

1. customthe mixture was removed from the shaker
2. filtrationfiltered through Celite
3. washThe solid bed was washed with methanol
4. concentrationThe filtrate was concentrated
5. dissolutionThe crude oil was dissolved in 1 N HCl
6. washwashed with ether
7. additionThe aqueous phase was treated with 2.5 N NaOH to pH>10
8. extractionextracted with chloroform
9. dry with materialThe combined chloroform extracts were dried over MgSO4
10. filtrationfiltered
11. concentrationconcentrated
12. customto give the crude indoline
13. customThe material was purified by flash column chromatography through silica gel (Biotage, elution with 10% ethyl acetate-hexanes)

ORD record

ord-97a61d1ab04f4d4282a7c206923c4eb6

Source dataset

uspto-grants-2008_04

DOI

10.6084/m9.figshare.5104873.v1

Patent number

US07351839B2