Ethanol → 7-(Tert-butoxycarbonyl)-3-phenyl-5,6,7,8-tetrahydroimidazo[1,5-a]pyrazine-1-carboxylic acid

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Reaction Steps

To 7-tert-butyl 1-methyl 3-phenyl-5,6-dihydroimidazo[1,5-a]pyrazine-1,7(8H)-dicarboxylate (3A) (1.6 g, 4.47 mmol) in THF (50 mL) was added aqueous LiOH (0.7 g in 18.5 mL water) and ethanol (13 mL). The resulting mixture was stirred at room temperature for 2 days. The reaction mixture was concentrated under reduced pressure, diluted with water and acidified to pH 4 with 1N aqueous HCl solution. The aqueous suspension was extracted 3 times with ethyl acetate. The combined organic extracts were washed with brine, dried over anhydrous MgSO4, filtered and concentrated under reduced pressure to give Intermediate 3B as a white solid in quantitative yield. The material was used in the next step without further purification. 1H-NMR (400 MHz, CDCl3) δ: 1.52 (s, 9H), 3.81 (m, 2H), 4.14 (m, 2H), 5.02 (s, 2H), 7.46-7.51 (m, 3H), 7.62-7.68 (m, 2H). LCMS (+ESI) m/z 344.23 [M+H]+.

Provenance & Evidence