Ethyl Acetate → 6-Chloro-5-hydroxy-1H-indole-2-carboxylic acid ethyl ester

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Reaction Steps

To a cooled (−78° C.) solution of 6-chloro-5-methoxy-1H-indole-2-carboxylic acid ethyl ester (example 39, step 1, 930 mg, 1.0 eq.) in dichloromethane (20 mL), was slowly added a solution of boron tribromide 1M in dichloromethane (7.33 mL, 2.0 eq.). The mixture was stirred at room temperature for 1 h, partitionned between ethyl acetate and ice water. The aqueous layer was extracted with ethyl acetate and the combined organic fractions were washed with 10% sodium bicarbonate solution and brine, dried over sodium sulfate, filtered, evaporated to dryness and purified on silica gel, eluting with a 4:1 to 3:1 gradient of cyclohexane/ethyl acetate, to yield 655 mg (74%) from the desired product as light brown solid. MS (m/e): 239.2 (M+, 35%).

Provenance & Evidence