Water → 1,2,3,4-Tetrahydro-cyclopenta(b)indole

Temperature

20 °C

A solution of phenylhydrazine (32.44 g, 300 mmol) in 2-propanol (300 mL) was treated with cyclopentanone (27 mL, 25.7 g, 305 mmol). The solution was stirred at 20° C. for 1 h and poured onto mixture of ice (900 g) and water (300 mL). The chilled mixture was stirred until the ice had melted then filtered. The filter-cake was washed with water (2×300 mL) an the resultant damp solid (85 g) was added to water (540 mL). The stirred suspension was treated with concentrated sulfuric acid (33 mL, 61 g, 600 mmol) then heated under reflux for 30 min, cooled to 0° C. and stirred for 15 min. The dark red solid was filtered off, washed with water (2×60 mL) and air-dried for 18 h. The crude product was added to dichloromethane (300 mL), stirred for 30 min then filtered, washing with dichloromethane (100 mL). The filtrate was treated with silica (48 g), stirred for 1 h, filtered and washed with dichloromethane (400 mL). The filtrate was concentrated to give a solid, which was triturated with hexane to give 1,2,3,4-tetrahydrocyclopent[b]indole (30 g, 65%) as a pink solid. Analytical data for 1,2,3,4-tetrahydrocyclopent[b]indole are included in Table 3 below.

1. filtrationhad melted then filtered
2. washThe filter-cake was washed with water (2×300 mL) an the resultant damp solid (85 g)
3. additionwas added to water (540 mL)
4. temperaturethen heated
5. temperatureunder reflux for 30 min
6. temperaturecooled to 0° C.
7. stirringstirred for 15 min
8. filtrationThe dark red solid was filtered off
9. washwashed with water (2×60 mL)
10. customair-dried for 18 h
11. additionThe crude product was added to dichloromethane (300 mL)
12. stirringstirred for 30 min
13. filtrationthen filtered
14. washwashing with dichloromethane (100 mL)
15. additionThe filtrate was treated with silica (48 g)
16. stirringstirred for 1 h
17. filtrationfiltered
18. washwashed with dichloromethane (400 mL)
19. concentrationThe filtrate was concentrated
20. customto give a solid, which
21. customwas triturated with hexane

ORD record

ord-c3d105a44b274f51afe300f6d4d71f0a

Source dataset

uspto-grants-2002_11

DOI

10.6084/m9.figshare.5104873.v1

Patent number

US06479534B1