Leflunomide → 5-Methyl-4-(4-trifluoromethylphenyl)aminothiocarbonylisoxazole

Participants

Reaction Steps

A solution of 24 grams of 5-methyl-4-(4-trifluoromethylphenyl)aminocarbonylisoxazole and 39 grams of Lawesson's reagent [2,4-bis(4-methoxyphenyl)-1,3-dithia-2,4-diphosphetane-2,4-disulfide] in 400 ml of toluene was refluxed for three hours. Upon cooling of mixture to room temperature, all the solid was filtered off and the filtrate was concentrated. The resulting crude product from the filtrate was then purified on a silica gel column with 3% methanol in dichloromethane to yield 16.5 grams of 5-methyl-4-(4-trifluoromethylphenyl)aminothiocarbonylisoxazole.

Provenance & Evidence