Hexachloroethane → 5-Chloro-3-(2,5-dimethyl-1H-pyrrol-1-yl)-1-methyl-1H-pyrazole

Participants

Reaction Conditions

Reaction Steps

A solution of 3-(2,5-dimethyl-pyrrol-1-yl)-1-methyl-1H-pyrazole (Intermediate 7, 0.51 g, 2.91 mmol) in tetrahydrofuran (25 mL) cooled to −70° C. was treated dropwise with a 2.5M solution of n-butyllithium in hexanes (1.3 mL, 3.25 mmol). The reaction was stirred at −70° C. for 2.6 h. After this time, the reaction was treated dropwise over 2-3 min with a solution of hexachloroethane (0.77 g, 3.2 mmol) in tetrahydrofuran (2.5 mL). The reaction was maintained at −70° C. for 20-25 min. After this time, the cooling bath was removed. The reaction continued to stir for 90 min, at which time the reaction was concentrated in vacuo. The residue was then partitioned between water (50 mL) and diethyl ether (1×50 mL). The organics were washed with a saturated aqueous sodium chloride solution (1×50 mL), dried over magnesium sulfate, filtered, rinsed with diethyl ether and concentrated in vacuo. Silica gel column chromatography (AnaLogix, 40 g, 5-10% ethyl acetate/hexanes) afforded 5-chloro-3-(2,5-dimethyl-pyrrol-1-yl)-1-methyl-1H-pyrazole (0.36 g, 60%) as a light brown solid; ES+-HRMS m/e calcd for C10H12N3Cl [M+H+] 210.0793, found 210.0792.

Provenance & Evidence