Trifluoroacetic anhydride → 2,6-Dibromopyridine N-Oxide

Temperature

5 °C

2,6-dibromo pyridine (79 g, 334 mmol) was dissolved in 800 ml of dry dichloromethane and cooled under nitrogen to 5° C. then urea hydrogen peroxide (104 g, 1.1 mol) was added in one portion. When the mixture had cooled again to 3° C., a solution of trifluoro acetic acid anhydride (140 mL, 1 mol) in 100 ml DCM was added via dropping funnel over 45 min, whilst keeping the temperature between 5-7° C. The mixture was allowed to warm to room temperature and stirred for 20 hours. The mixture was cooled in an ice bath to 10° C. and 10% aq. Na2SO3 (˜50 g/500 ml) was added dropwise over 60 minutes until test with starch iodide paper was negative. The resulting mixture was filtered to remove a quantity of fluffy solid and the layers were separated. The aqueous layer was extracted with dichloromethane (2×200 ml) and the combined extracts were dried over MgSO4 and concentrated under reduced pressure to give a light brown solid. Recrystallisation of crude product using 600ml of boiling acetone gave 48.47 g of the title compound.

1. temperatureWhen the mixture had cooled again to 3° C.
2. customover 45 min
3. custombetween 5-7° C
4. temperatureto warm to room temperature
5. temperatureThe mixture was cooled in an ice bath to 10° C.
6. filtrationThe resulting mixture was filtered
7. customto remove a quantity of fluffy solid
8. customthe layers were separated
9. extractionThe aqueous layer was extracted with dichloromethane (2×200 ml)
10. dry with materialthe combined extracts were dried over MgSO4
11. concentrationconcentrated under reduced pressure
12. customto give a light brown solid
13. customRecrystallisation of crude product

ORD record

ord-316b56d9990046838b7811b71ec17c39

Source dataset

uspto-grants-2010_04

DOI

10.6084/m9.figshare.5104873.v1

Patent number

US07691877B2