Patent GB-564990-A (GB)
Title: Improvements in and relating to azo compounds
Filed: 1941-12-13
Abstract: Azo compounds having bactericidal properties are obtained by (a) coupling an aromatic diazo compound, carrying either an N-substituted sulphonamide group in p-position or carrying two N-substituted or unsubstituted sulphonamide groups, with a hydroxycarboxylic acid of the benzene or heterocyclic series, free from any nuclear nitrogen atom or any amino group attached to the nucleus; (b) condensing an aromatic amine carrying one or two sulphonamide groups as above with a nitroso derivative of a hydroxycarboxylic acid as above; (c) condensing an aromatic nitroso compound carrying one or two sulphonamide groups as above with an amino derivative of a hydroxycarboxylic acid as above; (d) oxidising to an azo group the hydrazo group of a corresponding hydrazo compound; (e) reducing to an azo group the azoxy group of a corresponding azoxy compound; (f) subjecting to the action of ammonia or an amine a corresponding azo compound carrying one or more groups capable of conversion by such action into the required sulphonamide groups; or (g) diazotising a corresponding azo compound derived from an aromatic aminocarboxylic acid and warming the diazo compound to convert the diazo group into a hydroxyl group.  Examples relate to (1) the coupling of diazotised a -(p-aminobenzenesulphonamido)-pyridine with salicylic acid; (2) the coupling of the same diazo compound with o-cresotinic acid; (3) the coupling of diazotised 2-(p-aminobenzenesulphonamido)-4-methyl-thiazole with salicylic acid; (4) the condensation of a  - (p - aminobenzenesulphonamido) - pyridine with 5 - nitrososalicylic acid; (5) the condensation of a -(p-nitrosobenzenesulphonamido) - pyridine with 5 - amino - 2 - hydroxybenzoic acid; (6) the oxidation of 4 - dimethylsulphonamido - hydrazobenzene - 41-hydroxy-31-carboxylic acid with bromine in aqueous sodium hydroxide; (7) the reduction with stannous chloride in hydrochloric acid of the azoxy compound obtained by condensation of a - (p - hydroxylaminobenzenesulphonamido) - pyridine with 5-nitrososalicyclic acid; (8) the reaction with dimethylamine of aniline-4-sulphonic acid methyl ester --> salicylic acid; (9) the warming of the diazo compound from a -(p-aminobenzenesulphonamido)-pyridine --> 2-aminobenzoic acid; (10) the coupling of diazotised a  - (p - aminobenzenesulphonamido) - pyridine with 6-hydroxy-3-methyl-cumarone-2-carboxylic acid; (11) the coupling of diazotised p - dimethylsulphonamidoaniline with umbelliferone-3-carboxylic acid.  a  - (p - Nitrosobenzenesulphonamido) - pyridine is obtained by the action of Caro's acid on a -(p-aminobenzenesulphonamido) - pyridine in dioxane. 4-Dimethylsulphonamido - hydrazobenzene - 41-hydroxy - 31 - carboxylic acid is obtained by reduction of a mixture of p-nitrobenzenedimethylsulphonamide and 5-nitro-2-hydroxybenzoic acid. a  - (p - Hydroxylaminobenzenesulphonamido)-pyridine is obtained by reduction of the corresponding nitro compound with powdered zinc. The Specification as open to inspection under Sect. 91 comprises also the manufacture of (a) the corresponding compounds derived from any aromatic hydroxycarboxylic acid, containing any desired number of hydroxy or carboxylic acid groups; (b) the corresponding compounds derived from sulphonamides of heterocyclic compounds; (c) thiazole-21-amidosulphonylbenzene - (4 - azo - 5) - 2 - hydroxybenzoic acid; (d) 41-aminosulphonyl-aminosulphonylbenzene - (4 - azo - 5) - 2 - hydroxybenzoic acid and its 41-N-dimethyl, 3-methyl and 41-N-dimethyl-3-methyl derivatives; (e) 1 : 3-disulphonamidobenzene - (4 - azo - 5) - 2 - hydroxybenzoic acid; (f) pyridine-a -amidosulphonyl-benzene-(4-azo-5)-2-hydroxy - 1 : 3 - dicarboxylic acid; (g) diethylamidosulphonylbenzene - (4 - azo - 5) - 2 : 4 - dihydroxybenzoic acid, and additional examples, viz. of (12) the coupling of diazotised sulphanilylsulphanilamide with salicylic acid; (13) the coupling of diazotised N-dimethylsulphanilylsulphanilamide with o-cresotinic acid; (14) the coupling of diazotised aniline-2 : 4-disulphonamide with salicylic acid; (15) the coupling of diazotised a  - (p - aminobenzenesulphonamido)-pyridine with 2 - hydroxybenzene - 1 : 3 - dicarboxylic acid; (16) the coupling of diazotised aniline-4-sulphondiethylamide with 2 : 4-dihydroxybenzoic acid.  This subject-matter does not appear in the Specification as accepted.