Carbon Dioxide → 3,5-Dichloropyrazine-2-carboxylic acid

Temperature

-78 °C

To a solution of diisopropylamine (13.0 mL, 92.6 mmol, 2.3 eq.) in anhydrous THF (300 mL) at −78° C. under N2 was added dropwise a solution of 1.6 M nBuLi in hexanes (57.9 mL, 92.6 mmol, 2.3 eq.). After 1 hour a solution of 2,6-dichloropyrazine in anhydrous THF (6.0 g, 40.3 mmol) was added dropwise over 30 minutes. After stirring at −78° C. for 1 hour, the reaction mixture was poured onto crushed dry ice (solid carbon dioxide), and the reaction mixture was stirred at ambient temperature for 16 hours. The mixture was then diluted with water (100 mL) and washed with ethyl acetate (3×100 mL). The aqueous layer was cooled to 0° C., acidified with 2N HCl until pH ˜2, and extracted with ethyl acetate (3×100 mL). The combined organic extracts were dried (Na2SO4), filtered and evaporated in vacuo. The resultant crude was purified by column chromatography (Si-PPC, gradient 0% to 50%, methanol in dichloromethane) to give the desired product as a beige solid (3.16 g, 40.6%). 1H NMR (CDCl3, 400 MHz) δ ppm 8.60 (s, 1H).

1. additionthe reaction mixture was poured
2. stirringthe reaction mixture was stirred at ambient temperature for 16 hours
3. washwashed with ethyl acetate (3×100 mL)
4. temperatureThe aqueous layer was cooled to 0° C.
5. extractionextracted with ethyl acetate (3×100 mL)
6. dry with materialThe combined organic extracts were dried (Na2SO4)
7. filtrationfiltered
8. customevaporated in vacuo
9. customThe resultant crude was purified by column chromatography (Si-PPC, gradient 0% to 50%, methanol in dichloromethane)

ORD record

ord-c2c273b5830540b085b01fc53902607e

Source dataset

uspto-grants-2015_12

DOI

10.6084/m9.figshare.5104873.v1

Patent number

US09206174B2