[CH2:1]([C:3]1[CH:4]=[C:5]([OH:11])[CH:6]=[C:7]([CH3:10])[C:8]=1[NH2:9])[CH3:2].[OH-].[K+].Br[CH2:15][CH2:16][CH2:17][CH2:18][C:19]([O:21][CH2:22][CH3:23])=[O:20].Cl>CS(C)=O>[CH3:10][C:7]1[CH:6]=[C:5]([O:11][CH2:15][CH2:16][CH2:17][CH2:18][C:19]([O:21][CH2:22][CH3:23])=[O:20])[CH:4]=[C:3]([CH2:1][CH3:2])[C:8]=1[NH2:9]
500 ml of dimethyl sulfoxide (DMSO) are introduced at room temperature and, while stirring vigorously, 52.1 g (338.6 mmol) of the 3-ethyl-4-amino-5-methylphenol prepared in stage 2 are added in small portions. The mixture is cooled to 15° C. Then 33.5 g (507.9 mmol) of aqueous 85% strength potassium hydroxide solution are added dropwise so that the reaction temperature does not exceed 20° C. Then 82.7 ml (507.9 mmol) of ethyl 5-bromovalerate are added dropwise over the course of 70 minutes, maintaining the reaction temperature at 25° C. After a homogeneous solution has formed it is added to a mixture of 130 ml of 4M hydrochloric acid and ice and stirred well. The aqueous mixture is washed with diethyl ether. The aqueous phase is then made alkaline with 2M NaOH and extracted with diethyl ether, and the ether phase is washed twice with water and then with saturated brine, dried over sodium sulfate and concentrated. 67.5 g of a viscous oil are obtained and purified by vacuum distillation. Yield 31.7 g (33.7% of theory), boiling point 151°-152° C./10-2Torr.
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