Water → 4,5-Dihydro-4-oxo-5-phenylpyrano[3,2-b]indole-2-carboxylic acid

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Reaction Steps

A mixture of 1.0 g (0.0033 mole) of ethyl 4,5-dihydro-4-oxo-5-phenylpyrano[3,2-b]indole-2-carboxylate in 10 ml glacial acetic acid and 2.0 ml conc. hydrochloric acid was stirred at reflux for 41/2 hr, then cooled and added to 75 g ice--H2O. The solid was filtered, washed with cold water, then added to a mixture of 35 ml 5% aqueous sodium carbonate and 250 ml water. After filtering by gravity, the aqueous solution was washed three times with 75 ml chloroform, cooled in ice, and acidified with 4.0 N hydrochloric acid. The orange precipitate was filtered, digested 15 min on the steam bath with 25 ml water and re-filtered warm. Recrystallization from DMF-water yielded an off-white solid of mpt. >290°.

Provenance & Evidence