Patent GB-264916-A (GB)
Title: Improvements in and relating to the production of anthraquinone derivatives
IPC: C09B1/22
Filed: 1925-07-21
Abstract: 264,916. Drescher, H. A. E., Smith, W., Thomas, J., and Scottish Dyes, Ltd. July 21, 1925. #-Substituted aminoanthraquinones.-The mixture of isomeric substituted aminoanthraquinones obtained by ring closure of a 3-amino-4-substituted-benzoylbenzoic acid by means of sulphuric acid is separated into its components either by fractional precipitation from concentrated sulphuric acid or by fractional crystallization from hydrochloric acid or organic solvents. The crude cordensation product need not be isolated, the sulphuric acid solution being successively diluted to the appropriate concentrations for the isolation of the respective isomers. The crude mixtures may also be monochlorinated or monobrominated prior to the separation which is sometimes thus facilitated. The 3-amino-4-substituted benzovlbenzoic acids can be obtained by nitration and reduction of 4-substituted benzoylbenzoic acids. According to examples (1) 3-amino-4-chlorbenxoylbenzoic acid is treated with sulphuric acid to effect ring-closure and the solution diluted to an acid concentration of 80 per cent whereupon a #-amido-chloranthraquinone separates; upon diluting the filtrate until the acid concentration is 55 per cent a sulphate of another aminochloranthraquinone separates and is hydrolyzed by water to the free base; it is probably the 1-amino- 2-chlor compound and can be brominated in nitrobenzene or weak sulphuric acid suspension to 1-amino-2-chlor-4-bromanthraquinone which yields blue dyestuffs when condensed with aromatic amines and sulphonated : the first mentioned #-aminochloranthmquinone can also be brominated and can then be condensed to chlorinated indanthrones and flavanthrones. (2) The crude product of condensation of 3-amino-4-chlorbenzoylbenzoic acid is brominated and the product separated by fractional precipitation from sulphuric acid into 1-brom-2-amino-3-chloranthraquinone and 1-amino-3-chlor-4-bromanthraquinone, the latter being further purified by recrystallization from weak sulphuric acid or organic solvents; by chlorinating the crude product and then precipitating from sulphuric acid; 1 : 3- dichlor-2-aminoanthraquinone can be obtained. (3) The separation of the condensation product (or its brominated derivative) of 3-amino-4-chlorbenzoylbenzoic acid is effected by crystallization from concentrated hydrochloric acid, aniline, nitrobenzene, tetrachlorethane, solvent naphtha, phenol, or cresol, or, less satisfactorily by crystallization from chloroform, chlorbenzene, acetic acid, pyridine, acetone, ethylphthalate, glycerin, or methyl or butyl alcohol. (4) 3-Amino-4-brombenzoylbenzoic acid (obtained by condensing phthalic anhydride with brombenzene, nitrating, and reducing) is subjected to ring closure and the product separated into 2 : 3- and 1 : 2-aminobromanthraquinones; the former yields a dibrom-2- aminoanthraquinone by bromination in aqueous suspension; the mixture can also be brominated prior to the separation. (5) 3-Amino-4-methylbenzoylbenzoic acid is heated with monohydrate and the two isomers separated as the sulphates by dilution; the less soluble #-amino-compound yields 1-brom-2-amino-3-methylanthraquinone by bromination while the more soluble compound (probably 1-amino-2-methylanthraquinone) dyes cellulose acetate in orange shades.