[CH2:1]([N:3]([CH2:11][CH2:12][OH:13])[C:4]1[CH:9]=[CH:8][CH:7]=[C:6]([CH3:10])[CH:5]=1)[CH3:2].S(=O)(=O)(O)O.[N:19](OC(C)C)=[O:20]>O>[CH2:1]([N:3]([CH2:11][CH2:12][OH:13])[C:4]1[CH:9]=[CH:8][C:7]([N:19]=[O:20])=[C:6]([CH3:10])[CH:5]=1)[CH3:2]360 g of N-ethyl-N-(2-hydroxyethyl)-m-toluidine and 1,250 g of water are initially introduced into a stirred flask. 196 g of concentrated sulfuric acid are added, while stirring and cooling. During this addition, the internal temperature should not rise above 50°. After cooling to 0°, 187 g of isopropyl nitrite is allowed to run in slowly at -2° to +2°. The excess of nitrite is then removed in the customary manner with amidosulfonic acid. The reaction mixture is brought to room temperature and degassed under reduced pressure. 60 g of prereduced Pd/C (5%) is added to this solution as the catalyst and the N-ethyl-N-(2-hydroxyethyl)-3-methyl-4-nitroso-aniline, which has not been isolated, is hydrogenated at 20° to 40° under a gauge pressure of 0.4 bar of hydrogen. When the reaction has ended, the reaction batch is let down, the catalyst is filtered off and the reaction mixture is concentrated.
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