Ammonia → 6-phenyl-6-(4-dimethylaminophenyl)-6H-chromeno[4,3-b]-indole

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Reaction Steps

11.26 g of 4-dimethylaminobenzophenone and 10.5 g of 2-(2'-hydroxyphenyl)-indole are stirred in 50 ml of phosphorus oxychloride for 4 hours under reflux. The reaction mixture is poured onto ice and rendered alkaline with ammonia and the resulting precipitate is then filtered off. Repeated dissolving of the residue in methanol with the addition of a little 37% strength hydrochloric acid and precipitating with ammonia and water gives a slightly impure product, which is purified through a column, packed with 80 g of silica gel/ethyl acetate. Crystallisation from ethyl acetate/ethanol gives 16.7 g of 6-phenyl-6-(4-dimethylaminophenyl)-6H-chromeno[4,3-b]-indole of the formula ##STR17## in the form of yellowish crystals with a melting point of 229°-231° C. On silton clay, this colour-forming agent develops a blue colour with a λ max of 600 nm.

Provenance & Evidence