4-Hydroxybenzoic Acid → (1,1'-Biphenyl)-2,3'-diol

Participants

Reaction Conditions

Reaction Steps

A mixture consisting of 276.24 g 4-hydroxybenzoic acid, 124.12 g toluhydroquinone, 20.00 g p-toluenesulfonic acid monohydrate and 1800 ml o-xylene in a chemical reactor equipped with stirrer, thermometer and separator for the azeotropic removal of water under reflux is heated to reflux in an oil bath of 178° C. Refluxing and separation of water starts at a vapour temperature of ca. 137° C. and is continued for a total of 18 hours with ca. 35 ml of water separated. A beige, slightly viscous suspension is formed. It is cooled to 65° C. and 1250 ml of toluene are added. After further cooling to 25° C. the mixture is stirred for 30 minutes at this temperature and then filtered. The crystalline filter residue is washed with toluene to yield a beige solid. The orange filtrates are discarded. The solid is suspended in 1250 ml ethyl acetate and stirred for 1 hour at 45° C. The suspension is cooled to 6° C., filtered, the filter residue washed with ca. 800 ml of ice-cold ethyl acetate and dried in vacuum at 50° C. to constant weight to yield 341.60 g nearly colourless diphenol (XIV). HPLC purity is 99 area %

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