[CH3:1][C:2]1[CH:7]=[CH:6][CH:5]=[C:4]([CH3:8])[C:3]=1[NH:9][CH2:10][CH:11]([N:13]([CH3:15])[CH3:14])[CH3:12].[CH:16](O)=O.C=O.N>O>[CH3:16][N:9]([CH2:10][CH:11]([N:13]([CH3:15])[CH3:14])[CH3:12])[C:3]1[C:2]([CH3:1])=[CH:7][CH:6]=[CH:5][C:4]=1[CH3:8]A mixture of 1.5 g (7.3 mmoles) of 1-(2,6-dimethylphenyl-amino)-2-dimethylamino-propane, prepared as described in Example 8, 1.5 ml of 99% formic acid and 1.5 ml of a 36% aqueous formaldehyde solution is boiled for 6 hours. The mixture is cooled, poured onto 30 ml of water, the aqueous solution is rendered alkaline (pH=9) with concentrated aqueous ammonia, and extracted then thrice with 10 ml of benzene, each. The benzene solutions are combined, dried over anhydrous potassium carbonate, and the solvent is evaporated under reduced pressure. 1.58 g (98,8%) of 1-[N-methyl-N-(2,6-dimethylphenyl)-amino]2-dimethylamino-propane are obtained as a light yellow oil; b.p.: 102°-104° C./133.3 Pa.
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