Chlorosulfonic acid → 5-(3-Methylbutoxy)-8-propyl-1-thiachromone-2-carboxylic acid

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Reaction Steps

65 Parts of [5-(3-methylbutoxy)-2-propylphenylthio] fumaric acid was added portionwise to 240 parts of chlorosulphonic acid over a period of 20 minutes with stirring. The dark, orange solution was allowed to stand for 10 minutes before pouring cautiously into 2000 parts of ice. The resulting solid precipitate was allowed to settle under the gravity. The solid was filtered off, washed with water and sucked dry. At this point the material, became oily and it was extracted into ethyl acetate. The latter was dried over magnesium sulphate, filtered, concentrated in vacuo and allowed to crystallize in the refrigerator. The resulting yellow crystalline solid was collected and dried in vacuo to afford 8.4 parts of the desired product, mp 153° - 154°C (d). Recrystallization from ethyl acetate gave 6.0 parts of 5-(3-methylbutoxy)-8-propyl-1-thiachromone-2-carboxylic acid, mp 156°C (d).

Provenance & Evidence