C([NH:8][C:9]1[N:10]=[N:11][C:12]([C:15]2[CH:20]=[CH:19][C:18]([O:21][CH3:22])=[C:17]([O:23][CH:24]3[CH2:28][CH2:27][CH2:26][CH2:25]3)[CH:16]=2)=[CH:13][CH:14]=1)C1C=CC=CC=1.Cl.C1CCCCC=1>C(O)(=O)C.[Pd]>[NH2:8][C:9]1[N:10]=[N:11][C:12]([C:15]2[CH:20]=[CH:19][C:18]([O:21][CH3:22])=[C:17]([O:23][CH:24]3[CH2:25][CH2:26][CH2:27][CH2:28]3)[CH:16]=2)=[CH:13][CH:14]=1
15 g (40 mmol) of 3-benzylamino-6-(3-cyclopentyloxy-4-methoxyphenyl)pyridazine are heated to reflux in a mixture of 100 ml of glacial acetic acid, 6.5 ml of concentrated hydrochloric acid, 9.8 g (0.12 mol) of cyclohexene and 3 spatula tips of Pd/C (10 percent) for 4 hours. 9.8 g of cyclohexene and Pd/C are added once again, and boiling is continued for 16 hours. The catalyst is filtered off, the solution is diluted with 1 l of water and neutralized with concentrated ammonia, and the resulting precipitate is filtered off with suction. The product is purified by chromatography on silica gel with dichloromethane. 4.8 g (42.1%) of 3-amino-6-(3-cyclopentyloxy-4-methoxyphenyl)pyridazine of m.p. 207° C. are obtained.
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