Phenol → 4-Hydroxy-4'-chlorobenzophenone

Participants

Reaction Steps

Phenol is reacted with p-chlorobenzoyl chloride in a Friedel-Crafts reaction in the presence of aluminium chloride to give 4-chloro-4'-hydroxybenzophenone, m.p. 179°-181° C. (A). To a solution of this (5 g.) in pyridine (6 ml.) was added methanesulphonyl chloride (2.5 g.), at room temperature. The reactants were heated on a steam bath for 11/2 hours and the liquid reaction product poured into dilute hydrochloric acid to give a solid which was filtered and air-dried. This solid was recrystallised from industrial methylated spirits to give 4-chloro-4'-methylsulphonyloxybenzophenone, m.p. 120°-121° C. (B). To a solution of this (9.35 g.) in ethanol (200 ml.) was added hydrazine hydrate (8 ml.) followed by glacial acetic acid (1.5 ml.). The mixture was heated under reflux with stirring for 17 hours. The solvent was evaporated under reduced pressure to give an oil which was extracted with chloroform. The extract was washed with water, aqueous sodium hydroxide and water and then dried over magnesium sulphate. The solvent was evaporated under reduced pressure to give an oil. On standing this crystallised to give 4-chloro-4'-methylsulphonyloxybenzophenone hydrazone, m.p. 70°-110° C. (C). This product (5 g.) was heated under reflux with acetone (25 ml.) for 24 hours. The mixture was then evaporated under reduced pressure to give 4-chloro-4'-methylsulphonyloxybenzophenone isopropylidenehydrazone m.p. 148°-9° C.

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