Dabco → Methyl 6-(3,3-diethoxyprop-1-ynyl)-5-methyl-3-oxo-4-(3-(trifluoromethyl)phenyl)-3,4-dihydropyrazine-2-carboxylate

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Reaction Steps

Methyl 6-iodo-5-methyl-3-oxo-4-[3-(trifluoromethyl)phenyl]-3,4-dihydropyrazine-2-carboxylate (SM1, 1.2 g, 2.8 mmol), allylpalladium(II) chloride dimer (0.0072 g), 10% by weight tri(tert-butyl)phosphine in hexane (2.1 mL) and anhydrous DMF (3.0 mL) were stirred until a clear solution was obtained. Propargylaldehyde diethyl acetal (0.44 mL, 3.1 mmol) in anhydrous DMF (2.3 mL) was added, followed by 1,4-diazabicyclo[2.2.2]octane (0.63 g, 5.6 mmol) in small portions. The red solution was purged with dry argon for 5 minutes and then stirred under argon at RT. After 4 h, the solvent was evaporated off using an oil pump. The residue was taken up in acetonitrile (10 mL), filtered through glass-wool and then concentrated with silica. Chromatography on silica with ethyl acetate-heptanes (1:10 and 1:2) as eluents gave the title compound (0.46 g, 37%) as a yellow oil.

Provenance & Evidence