Ammonium Chloride → 1-cyclopentanecarbonyl-3-trifluoromethyl-5,6-dihydro-8H-imidazo[1,5-a]pyrazine-7-carboxylic acid tert-butyl ester

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Reaction Steps

1-(Methoxy-methyl-carbamoyl)-3-trifluoromethyl-5,6-dihydro-8H-imidazo[1,5-a]pyrazine-7-carboxylic acid tert-butyl ester 27e (0.3 g, 0.79 mmol) was dissolved in 20 mL of tetrahydrofuran under stirring, and then cyclopentylmagnesium bromide (0.79 mL, 1.58 mmol) was added dropwise to the solution at 0° C. The reaction mixture was stirred at 0° C. for 3 hours and monitored by thin layer chromatography until the disappearance of the starting materials. 50 mL of saturated ammonium chloride and 10 mL of saturated brine were added. The crude mixture was extracted with ethyl acetate (100 mL×3), and then the combined organic phase was dried with anhydrous magnesium sulfate, filtered and concentrated under reduced pressure. The resulting residue was purified by silica gel column chromatography to obtain the title compound 1-cyclopentanecarbonyl-3-trifluoromethyl-5,6-dihydro-8H-imidazo[1,5-a]pyrazine-7-carboxylic acid tert-butyl ester 28a (0.1 g, yield 30%) as a yellow oil.

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