4-Methoxy-3,3-dimethyl-1,3-dihydro-indol-2-one → 4-Hydroxy-3,3-dimethyl-1,3-dihydro-indol-2-one

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Reaction Conditions

Reaction Steps

Pyridine hydrochloride (51.10 g, 442.2 mmol) and 4-methoxy-3,3-dimethyl-1,3-dihydro-indol-2-one (21.61 g, 113.0 mmol) are combined and stirred in a melt at 220° C. for 45 minutes. Heating is removed and when the mixture cooled to 100° C., water (60 mL) is added, followed by ethyl acetate (150 mL) at 65° C. The layers are separated and the aqueous phase is extracted five times with ethyl acetate (50 mL). The combined organic layers are extracted first with a combination of aqueous hydrochloric acid (1N, 10 mL) and a saturated solution of sodium chloride (10 mL), then with a combination of a saturated solution of sodium bicarbonate (10 mL) and a saturated solution of sodium chloride (10 mL). After drying over magnesium sulfate, the solvent is removed via rotary evaporation. The crude material is dissolved in ethyl acetate (200 mL) and hexane (200 mL) at 60° C. Crystallization is allowed to begin slowly over 1 hour at 50° C. After stirring for 12 hours at 24° C., the slurry is cooled to 0° C. for 1 hour, then vacuum filtered washing twice with cold 1:1, ethyl acetate:hexane (35 mL, 0° C.) to provide 13.8 g (98.6% purity, 68% yield) of 4-hydroxy-3,3-dimethyl-1,3-dihydro-indol-2-one, mp 224–225° C. MS (ES+) m/z 178 (M++1). From the filtrate a second crop (5.0 g, 98.4% purity, 25% yield) is obtained to give a total yield of 93%.

Provenance & Evidence