Improvements in and relating to the production of benzoylbenzoic acid and anthraquinone derivatives

摘要

Halogenated benzoyl-o-benzoic acids; halogenanthraquinones 2-Benzoylbenzoic acid or a halogen derivative thereof is treated with a halogenating agent in a sulphuric acid medium, in the presence or not of a catalyst such as iodine. The products may be ring-closed to give halogenanthraquinones, and, if desired, ring-closure may proceed without isolation of the halogenated acid. The halogenanthraquinones may be isolated by fractional dilution of the sulphuric acid solution. In examples, (1) 2-benzoylbenzoic acid is chlorinated in oleum (5 per cent) and in presence of iodine to give products of different chlorine content dependent on the duration of halogenation; these products are ring-closed by heating in 10 per cent oleum at 110-120 DEG C., and details of the fractional isolation of one of the reaction-mixtures is also given wherein the concentrated sulphuric acid solution is diluted to 87,5 per cent strength, 85 per cent strength, and finally with excess of water to separate the isomers; (2) 41-chloro-2-benzoylbenzoic acid is chlorinated in 90 per cent sulphuric acid in presence of iodine; the product is ring-closed in pure sulphuric acid at 160 DEG C. and the solution diluted to 90 per cent strength in order to isolate 2-3-dichloranthraquinone. The use of chlorsulphonic acid as a suitable medium is also mentioned.