N-Acetylimidazolidinone → 1-{2-[(2,3-Dihydro-1H-inden-4-yl)amino]-4,5-dihydro-1H-imidazol-1-yl}ethan-1-one

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Reaction Steps

140.9 g (1.1 moles) of 1-acetyl-2-imidazolidinone (melting point 186°-187° C.) are introduced into 1,320 ml of POCl3 and 133.2 g (1 mole) of 4-amino-indan are added dropwise, with vigorous stirring, under conditions such that the internal temperature does not rise above 50° C. After completion of the addition, stirring is continued for 40 hours at 50° C. The excess POCl3 is then distilled off as completely as possible under reduced pressure on a rotary evaporator and the distillation residue is added to 5 l of ice water whilst keeping the temperature at ≤15° C. by further addition of ice. The pH is brought to 11 by means of 25% strength sodium hydroxide solution, whilst cooling with ice, the mixture is repeatedly extracted with chloroform, the combined chloroform phases are again washed with 1 liter of 2 N sodium hydroxide solution and are then washed neutral with water and dried over anhydrous sodium sulfate, and the chloroform is distilled off. The residue is recrystallized from isopropanol. 84.3 g of pure 1-acetyl-(4-indanylamino)-2-imidazoline of melting point 180.5°-182° C. are obtained.

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