1,2-Dibromo-1,1,2,2-tetrachloroethane → 3-Bromo-1-(dimethylsulfamoyl)pyrazole

To a solution of N-dimethylsulfamoylpyrazole (44.0 g, 0.251 mol) in dry tetrahydrofuran (500 mL) at −78° C. was added dropwise a solution of n-butyllithium (2.5 M in hexane, 105.5 mL, 0.264 mol) while maintaining the temperature below −60° C. A thick solid formed during the addition. Upon completion of the addition the reaction mixture was maintained for an additional 15 minutes, after which time a solution of 1,2-dibromo-tetrachloroethane (90 g, 0.276 mol) in tetrahydrofuran (150 mL) was added, dropwise while maintaining the temperature below −70° C. The reaction mixture turned a clear orange; stirring was continued for an additional 15 minutes. The −78° C. bath was removed and the reaction was quenched with water (600 mL). The reaction mixture was extracted with methylene chloride (4×), and the organic extracts were dried over magnesium sulfate and concentrated. The crude product was further purified by chromatography on silica gel using methylene chloride/hexane (50:50) as eluent to afford the title product as a clear colorless oil (57.04 g).

1. temperaturewhile maintaining the temperature below −60° C
2. customA thick solid formed during the addition
3. additionUpon completion of the addition the reaction mixture
4. temperaturewas maintained for an additional 15 minutes
5. temperaturedropwise while maintaining the temperature below −70° C
6. customThe −78° C. bath was removed
7. customthe reaction was quenched with water (600 mL)
8. extractionThe reaction mixture was extracted with methylene chloride (4×)
9. dry with materialthe organic extracts were dried over magnesium sulfate
10. concentrationconcentrated
11. customThe crude product was further purified by chromatography on silica gel

ORD record

ord-bc5c5a868a0740d5801968ee40903dc1

Source dataset

uspto-grants-2014_04

DOI

10.6084/m9.figshare.5104873.v1

Patent number

US08697734B2