Potassium Acetate → Indole

Temperature

80 °C

To a mixture of 4-bromoindole (1, 9.80 g, 50 mmol), pinacole diborate (2, 13.97 g, 55 mmol), and KOAc (14.72 g, 150 mmol) in DMSO (200 mL) was added Palladium catalyst PdCl2(dppf)CH2Cl2 (1.22 g, 1.5 mmol). The system was degassed, and then charged with nitrogen for three times. The mixture was stirred at 80° C. oil bath under nitrogen for 22 hours. TLC2 showed the complete disappearance of the starting material 4-bromoindole (1). The mixture was cooled to room temperature, and then poured to water (1 L). The product was extracted with ethyl acetate for three times. The combined extracts were washed by brine for five times to remove DMSO solvent, and then dried over Na2SO4. During the washing step, the catalyst may precipitate out, which was removed by filtration. The ethyl acetate solution was filtered and condensed. The residue was purified on a silica gel column eluting with EtOAc-hexane (9:1). The first fraction provided the side product indole (1.25 g, 21% yield), Rf0.55 (EtOAc-Hexane 5:1). The second fraction provided the product 4-(4,4,5,5-tetramethyl-[1,3,2]dioxaborolan-2-yl)-1H-indole as a white solid (3, 8.01 g, 66%), Rf0.46 (EtOAc-Hexane 5:1).

1. customThe system was degassed
2. additioncharged with nitrogen for three times
3. temperatureThe mixture was cooled to room temperature
4. additionpoured to water (1 L)
5. extractionThe product was extracted with ethyl acetate for three times
6. washThe combined extracts were washed by brine for five times
7. customto remove DMSO solvent
8. dry with materialdried over Na2SO4
9. customDuring the washing step, the catalyst may precipitate out
10. customwhich was removed by filtration
11. filtrationThe ethyl acetate solution was filtered
12. customcondensed
13. customThe residue was purified on a silica gel column
14. washeluting with EtOAc-hexane (9:1)

ORD record

ord-74e1068207894584a15d46cf77bd1e39

Source dataset

uspto-grants-2005_03

DOI

10.6084/m9.figshare.5104873.v1

Patent number

US06861418B2