Patent GB-349080-A (GB)
Title: The manufacture of conversion products of 1.2-anthraquinonethioglycollic-carboxylic acid
IPC: C09B5/24
Filed: 1930-02-20
Abstract: Thiophenanthrones; anthraquinone-oxythiophenes.-Anthraquinone -1.2-thioglycollic-carboxylic acid is heated with an organic acid anhydride to yield two series of products, one containing the thiophenanthrone structure, the other an oxythiophene ring. Generally a mixture of products is obtained comprising thiophenanthrone-2-carboxylic acid and anthraquinone-1.2-acyloxythiophene.  These may be separated either by dissolving out the thiophenanthrone-2-carboxylic acid with dilute soda or sodium carbonate, or by treating the crude product with an organic diluent in which the acyloxythiophene is more soluble.  The anthraquinone-1.2-acyloxythiophene may be saponified to the oxythiophene.  If heating is carried out for a shorter time an intermediate product, C-carboxythiophenanthrone-2-carboxylic acid, may be isolated; this substance may be converted to thiophenanthrone-2-carboxylic acid by heating it in an organic diluent.  It is possible to favour the yield of either series of products: thus by acting with the acid anhydride on an alkali salt of the anthraquinone-1.2-thioglycollic-carboxylic acid, or on a mixture of the free acid and an alkali, or on a mixture of the free acid and a metallic oxide or salt of a weak acid, the acyloxythiophene compound is mainly formed, and by heating the free thioglycollic-carboxylic acid alone or in the presence of a higher boiling diluent, the anthraquinone-1.2-oxythiophene is obtained directly; on the other hand, by heating an alkaline solution of anthraquinone - 1.2 - thioglycollic - carboxylic acid alone, the thiophenanthrone-2-carboxylic acid is mainly formed, and when stronger alkaline solutions are heated for a longer time the C-carboxythiophenanthrone-2-carboxylic acid is obtainable.  In examples, anthraquinone - 1.2 - thioglycollic - carboxylic acid (prepared by acting with monochloracetic acid on anthraquinone-1-mercapto-2-carboxylic acid,-cf.  Example (1) of Specification 249,489, [Class 2 (iii), Dyes &c.]), is (1), boiled with acetic anhydride, and the thiophenanthrone-2-carboxylic acid extracted with dilute sodium carbonate solution leaving anthraquinone-1.2-acetyloxythiophene in the residue; separation may also be effected by extracting the mass with chlorbenzene or toluene in which the thiophenanthrone-2-carboxylic is nearly insoluble; if the boiling is stopped at an earlier stage C-carboxythiophenanthrone-2-carboxylic acid is isolated: (2) is boiled with acetic anhydride and sodium carbonate or sodium benzoate to yield anthraquinone-1.2-acetyloxythiophene; treatment of this with alcoholic caustic potash gives anthraquinone-1.2-oxythiophene: (3) is boiled with acetic anhydride and barium oxide (or oxides of calcium, magnesium or zinc may be used) to yield anthraquinone-1.2-acetyloxythiophene; this body is also obtained by heating the sodium salt of the acid, or a mixture of the free acid and its sodium salt, with acetic anhydride: (4) is boiled in trichlorbenzene (or quinoline, dimethylaniline or tetrahydronaphthalene may be used) to yield anthraquinone-1.2-oxythiophene: (5) is dissolved in weak soda solution and boiled to yield thiophenanthrone-2-carboxylic acid; alternatively the starting material may be anthraquinone-1-mercapto-2-carboxylic acid which is treated with a weakly alkaline solution of monochloracetic acid and then boiled; if in this latter process the solution of monochloracetic acid is of somewhat greater alkalinity, on boiling for an hour C-carboxythiophenanthrone-2-carboxylic acid is obtained.