Patent GB-684027-A (GB)
Title: Process for the manufacture of so-called naphthoquinone-imines
Filed: 1949-09-13
Abstract: Naphthoquinoneimines of the general formula <FORM:0684027/IV (b)/1> (wherein X represents hydrogen, bromine or chlorine and Y represents -O- or -NH-) are manufactured by subjecting compounds of the general formula <FORM:0684027/IV (b)/2> (wherein Z denotes -OH or = O, R1 denotes -N = N-Aryl or -NO2, and R2 denotes -N = N-Aryl or = O when Z denotes -OH on = O respectively) to reduction followed by oxidation. In examples: (1) 4 : 8-bis-benzeneazo-1 : 5-dihydroxynaphthalene is reduced with stannous chloride and hydrochloric acid in aqueous propanol suspension, and the product is dissolved in caustic soda and air is passed through the solution, yielding 5-amino-8-hydroxy-1 : 4-naphthoquinone-1-imine; (2) and (7) 2 : 6 - dibromo - 4 : 8 - bis - benzeneazo - 1 : 5 -dihydroxynaphthalene is treated as in (1) to produce 3 : 7-dibromo-5-amino-8-hydroxy-1 : 4-naphthoquinone-1-imine; (3) the product of (2) is obtained directly by bromination of the starting material of (1) in nitrobenzene at 140 DEG  C., the reduction in this case being effected by the hydrobromic acid present in the reaction mass and the re-oxidation by means of excess bromine without isolation of intermediates; (4) 8 - nitro - 2 : 6 - dibromo - 5 - hydroxy - 1 : 4 - naphthoquinone is treated as in (1); (5) the reduction in (4) is effected with hydrogen in the presence of nickel in glacial acetic acid; (6) 2 : 6-dichloro-4 : 8-bis-benzeneazo-1 : 5-dihydroxynaphthalene is treated as in (1); (8) the process of (3) is carried out at 60-80 DEG  C. using concentrated sulphuric acid instead of nitrobenzene as solvent and with the addition of iodine, the reaction mixture being cooled and diluted with water keeping the temperature below 40 DEG  C. if the same product as in (3) is desired; if the temperature rises above 50 DEG  C. the product is 3 : 7 - dibromo - 5 : 8 - dihydroxy - 1 : 4 - naphthoquinone-1-imine; (9) the bromine in (8) is replaced by chlorine, with ultra-violet irradiation.  Specifications 606,008 and 629,706 are referred to.  8 - Nitro - 2 : 6 - dibromo - 5 - hydroxy - 1 : 4 - naphthoquinone is obtainable by brominating 1 : 5-dihydroxynaphthalene and nitrosating or nitrating the product (e.g. nitrating it with a mixture of 100 per cent nitric acid and concentrated sulphuric acid).ALSO:Naphthoquinoneimines of the general formula <FORM:0684027/IV (c)/1> (wherein X represents hydrogen, bromine or chlorine and Y represents -O- or -NH-) are manufactured by subjecting compounds of the general formula <FORM:0684027/IV (c)/2> (wherein Z denotes -OH or =O, R1 denotes -N=N-Aryl or -NO2, and R2 denotes -N=N-Aryl or =O, when Z denotes -OH or =O respectively) to reduction followed by oxidation.  In examples: (1) 4 : 8-bis-benzeneazo-1 : 5-dihydroxynaphthalene is reduced with stannous chloride and hydrochloric acid in aqueous propanol suspension, and the product is dissolved in caustic soda and air is passed through the solution, yielding 5-amino-8-hydroxy - 1 : 4 - naphthoquinone - 1 - imine; (2) and (7) 2 : 6-dibromo-4 : 8-bis-benzeneazo-1 : 5-dihydroxynaphthalene is treated as in (1) to produce 3 : 7-dibromo-5-amino-8-hydroxy-1 : 4-naphthoquinone-1-imine; (3) the product of (2) is obtained directly by bromination of the starting material of (1) in nitrobenzene at 140 DEG  C., the reduction in this case being effected by the hydrobromic acid present in the reaction mass and the reoxidation by means of excess bromine without isolation of intermediates; (4) 8 - nitro - 2 : 6 - dibromo - 5 - hydroxy - 1 : 4 - naphthoquinone is treated as in (1); (5) the reduction in (4) is effected with hydrogen in the presence of nickel in glacial acetic acid; (6) 2 : 6 - dichloro - 4 : 8 - bis - benzeneazo - 1 : 5 - dihydroxynaphthalene is treated as in (1); (8) the process of (3) is carried out at 60-80 DEG  C., using concentrated sulphuric acid instead of nitrobenzene as solvent and with the addition of iodine, the reaction mixture being cooled and diluted with water keeping the temperature below 40 DEG  C. if the same product as in (3) is desired; if the temperature rises above 50 DEG  C. the product is 3 : 7-dibromo-5 : 8-dihydroxy-1 : 4-naphthoquinone-1-imine; (9) the bromine in (8) is replaced by chlorine, with ultraviolet irradiation.  Specifications 606,008 and 629,706 are referred to.  Diazo compounds of the second general formula above (Z=OH, R1=R2=N=N-Aryl) are obtainable by coupling 1 : 5-dihydroxynaphthalene with diazo compounds (e.g. diazotized aniline), and, if desired, introducing bromine or chlorine before or after coupling.