5-Methoxyindole → 5-methoxy-2,3-dihydro-1H-indole

Temperature

11 °C

5-Methoxyindole (50 g, 0.34 mol) was dissolved in glacial acetic acid (500 mL) in a 3 L 3-necked flask fitted with a mechanical stirrer, a dropping funnel and a thermometer. The solution was cooled to 10-12° C. with an ice bath and sodium cyanoborohydride (64 g, 1.0 mol) was added in portions while ensuring the temperature remained at or below 15-16° C. After the addition was complete the cooling bath was removed and the reaction was warmed to ambient temperature for 0.5 hour. TLC (1:1 EtOAc/hexane) confirmed a complete reaction. The reaction was cooled to 5-10° C. and 50% aqueous sodium hydroxide was added until the pH was 8-10. The product oiled out and was extracted with ethyl acetate (3×700 mL). The combined organic layers were washed with water (2×500 mL) and brine (400 mL), dried over anhydrous potassium carbonate, filtered and concentrated to afford 5-methoxyindoline (50 g, 0.337 mol, 99% yield) as a thick oil. This product was used without further purification. The structure was corroborated by NMR spectroscopy.

1. customfitted with a mechanical stirrer, a dropping funnel
2. custombelow 15-16° C
3. additionAfter the addition
4. customwas removed
5. temperaturethe reaction was warmed to ambient temperature for 0.5 hour
6. customa complete reaction
7. temperatureThe reaction was cooled to 5-10° C.
8. extractionwas extracted with ethyl acetate (3×700 mL)
9. washThe combined organic layers were washed with water (2×500 mL) and brine (400 mL)
10. dry with materialdried over anhydrous potassium carbonate
11. filtrationfiltered
12. concentrationconcentrated

ORD record

ord-59ad10aa3abf4724aa5307cac92df16d

Source dataset

uspto-grants-2010_04

DOI

10.6084/m9.figshare.5104873.v1

Patent number

US07704667B2