Phthalic Anhydride → HCID 178507831, compound

A mixture of phthalic anhydride (22.7 g, 2.5 eq) and urea hydrogen peroxide (17.3 g, 3.0 eq) in 80 mL 3:1 acetonitrile/methanol was heated at 35–40° C. until all solids dissolved. After cooling to room temperature, solid 4-amino-3,5-dichloropyridine (10 g, 61 mmol, available from Aldrich Chemical Company, Milwaukee, Wis.) was added portion-wise. The reaction temperature was maintained at 20–25° C. during addition. This mixture was stirred at room temperature for 18 h and quenched with 150 mL chilled aqueous sodium sulfite solution (10.4 g Na2SO3, 1.4 eq). The resulting slurry was filtered and washed with water. The wet phthalate salt of the N-oxide was reslurried in 20 mL water and free based with aqueous K2CO3. After stirring for 6 h at room temperature, the slurry was filtered and washed with water. The wet cake was air-dried at 75° C. The residual water was removed by reslurrying the dry cake in refluxing methanol for 2 h. It was filtered at 10-20° C. and washed with methanol. The cake was vacuum dried at 75° C. until the methanol content was less than 0.1%. The product, 4 amino-3,5-dichloropyridine-N-oxide (the compound of formula X) was obtained (9.5 g, 98% purity, 85% yield).

1. temperaturewas heated at 35–40° C. until all solids
2. dissolutiondissolved
3. temperatureThe reaction temperature was maintained at 20–25° C. during addition
4. customquenched with 150 mL
5. filtrationThe resulting slurry was filtered
6. washwashed with water
7. stirringAfter stirring for 6 h at room temperature
8. filtrationthe slurry was filtered
9. washwashed with water
10. customThe wet cake was air-dried at 75° C
11. customThe residual water was removed
12. temperaturein refluxing methanol for 2 h
13. filtrationIt was filtered at 10-20° C.
14. washwashed with methanol
15. dry with materialdried at 75° C. until the methanol content

ORD record

ord-1dff48d99fba419d8c50e751922f5821

Source dataset

uspto-grants-2006_10

DOI

10.6084/m9.figshare.5104873.v1

Patent number

US07129357B2