Trifluoroacetic acid → 3-Methyl-1-(1-methyl-1h-imidazol-4-yl)-2-oxo-4-imidazolidinecarboxylic acid trifluoroacetate salt

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Reaction Steps

To a stirred mixture of 1,1-dimethylethyl 3-methyl-2-oxo-4-imidazolidinecarboxylate (200 mg, 0.999 mmol) (prepared as described in step (iii) of Example 13, starting from (4S)-2-oxo-3-{[(phenylmethyl)oxy]carbonyl}-4-imidazolidinecarboxylic acid) and 4-bromo-1-methyl-1H-imidazole (193 mg, 1.199 mmol) in 1,4-dioxane (8 ml) was added potassium phosphate (1060 mg, 4.99 mmol), copper(I) iodide (190 mg, 0.999 mmol) and trans-N,N-dimethylcyclohexane-1,2-diamine (0.158 ml, 0.999 mmol) and the reaction mixture was stirred at reflux under argon for 3 hours. The mixture was cooled to room temperature and diluted with dichloromethane (20 mL) and filtered and washed through with dichloromethane. The filtrate was concentrated under vacuum and taken up in dichloromethane. The solution was washed with 0.880 ammonia (×3), water then brine and separated by hydrophobic frit and the organic layer was reduced under vacuum. The residue was purified by Flashmaster automated silica gel chromatography eluting with 0-20% methanol in dichloromethane to leave an oil which crystallised on standing. The residue was dried under vacuum overnight to give 1,1-dimethylethyl 3-methyl-1-(1-methyl-1H-imidazol-4-yl)-2-oxo-4-imidazolidinecarboxylate (285 mg, 87% yield). LC/MS [M+H]+=281. (ii) Trifluoroacetic acid (1.0 ml, 12.98 mmol) was added to a solution of 1,1-dimethylethyl 3-methyl-1-(1-methyl-1H-imidazol-4-yl)-2-oxo-4-imidazolidinecarboxylate (220 mg, 0.785 mmol) in DCM (2 ml) and the reaction mixture was stirred at room temperature for 5 hours. The solvent was evaporated under vacuum, azeotroping with toluene and the residue was dried under vacuum over the weekend to give crude 3-methyl-1-(1-methyl-1H-imidazol-4-yl)-2-oxo-4-imidazolidinecarboxylic acid trifluoroacetate salt which was taken through to next step without further purification. LC/MS [M+H]+=225.

Provenance & Evidence