Cesium carbonate → 7-tert-butyl 1-methyl 3-phenyl-5,6-dihydroimidazo[1,5-a]pyrazine-1,7(8H)-dicarboxylate

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Reaction Conditions

Reaction Steps

To a round-bottomed flask charged with Intermediate 1H (2 g, 5.55 mmol), phenyl boronic acid (2.07 g, 16.65 mmol), [Pd-(dppf)Cl2] (0.45 g, 10 mol %), and cesium carbonate (5.45 g, 16.65 mmol) was added toluene (anhydrous and de-gassed; 80 mL). The reaction mixture was heated to 110° C. while stirring under argon for 6 hours. After cooling to room temperature, saturated aqueous NaHCO3 solution was added and the mixture was extracted three times with ethyl acetate. The combined extracts were dried over anhydrous MgSO4, filtered and concentrated under reduced pressure to give the crude product. Purification by column chromatography (silica), eluting with ethyl acetate/hexane mixtures, provided Intermediate 3A as a white solid (70% yield). 1H-NMR (400 MHz, CDCl3) δ: 1.52 (s, 9H), 3.79 (m, 2H), 3.93 (s, 3H), 4.12 (m, 2H), 5.00 (s, 2H), 7.43-7.47 (m, 3H), 7.63-7.66 (m, 2H). LCMS (+ESI) m/z 358.28 [M+H]+.

Provenance & Evidence