Chlorosuccinimide → 3-Chloro-5-methyl-3-methylthiooxindole

Participants

Reaction Steps

A solution of 5-methyl-3-methylthiooxindole (1.00 g, 0.0052 mol) and N-chlorosuccinimide (700 mg, 0.0053 mol) in carbon tetrachloride (100 ml) was stirred at room temperature for 1 hour. The precipitate was removed by filtration and the filtrate was evaporated to give the crude 3-chloro-5-methyl-3-methylthiooxindole, which was dissolved in tetrahydrofuran (20 ml) and added to a vigorously stirred slurry of red mercuric oxide (1.13 g, 0.0052 mol) and boron trifluoride etherate (745 mg, 0.0052 mol) in 70 ml of 20 percent aqueous tetrahydrofuran. After stirring at room temperature for 2 hours, the reaction mixture was filtered through a Celite pad and the filtrate was extracted with two 100-ml portions of chloroform. The chloroform extracts were dried over anhydrous magnesium sulfate, filtered, and the filtrate was evaporated. The residue was chromatographed on silica gel. Elution with chloroform gave 5-methylisatin (610 mg, 0.0038 mol, 74%), mp 185°-187° (recrystallized from ethanol) as red needles.

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