Trifluoroacetic anhydride → 3,8-Dibromo-benzo[c]chromen-6-one

A solution of TFAA (2.1 mL, 3.15 mmol) in dichloromethane (5 mL) was added dropwise to a suspension of 2,7-dibromo-fluoren-9-one (3.3 g, 10 mmol) and H2O2-urea (1.4 g, 15 mL) in dichloromethane (50 mL). The mixture was stirred at room temperature for 48 hours, a second portion of H2O2-urea was added, and stirring was continued at room temperature for a further 72 hours. The mixture was filtered, the organic phase was extracted with water (50 mL), and dried over Na2SO4. After removal of solvent, the residue was heated with 2N NaOH at 80° C. for 10 minutes, filtered, the cooled filtrate extracted with ether. The aqueous phase was acidified with 2N HCl and extracted with ethyl acetate (200 mL). HCl (2 mL 4M solution) was added to the ethyl acetate and heated for 2 hours. The solvent was removed under vacuum, the residue was recrystallized from ethyl acetate/ethanol to give the final product 3,8-Dibromo-benzo[c]chromen-6-one as a white solid (1.5 g, 40%).

1. stirringstirring
2. waitwas continued at room temperature for a further 72 hours
3. filtrationThe mixture was filtered
4. extractionthe organic phase was extracted with water (50 mL)
5. dry with materialdried over Na2SO4
6. customAfter removal of solvent
7. temperaturethe residue was heated with 2N NaOH at 80° C. for 10 minutes
8. filtrationfiltered
9. extractionthe cooled filtrate extracted with ether
10. extractionextracted with ethyl acetate (200 mL)
11. additionHCl (2 mL 4M solution) was added to the ethyl acetate
12. temperatureheated for 2 hours
13. customThe solvent was removed under vacuum
14. customthe residue was recrystallized from ethyl acetate/ethanol

ORD record

ord-a37b257125754f7dae68c9628ad4c8a9

Source dataset

uspto-grants-2014_09

DOI

10.6084/m9.figshare.5104873.v1

Patent number

US08841278B2