4-Fluorophenyl isocyanate → (S)-1-acetyl-6-bromo-N-(4-fluorophenyl)-2-methyl-2,3-dihydropyrido[2,3-b]pyrazine-4(1H)-carboxamide

Participants

Reaction Conditions

Reaction Steps

A reaction vial was charged with (S)-1-(6-bromo-2-methyl-3,4-dihydropyrido[2,3-b]pyrazine-1(2H)-yl)ethanone (0.1 M solution in 1,2-dichloroethane, 0.30 mL, 0.03 mmol) and N,N-diisopropylethylamine (0.052 mL, 0.300 mmol) was added. 1-Fluoro-4-isocyanatobenzene (0.017 mL, 0.150 mmol) was added neat, followed by the addition of a catalytic amount of DMAP (˜1 mg), and the reaction was shaken at 50° C. overnight. The reaction was diluted with ethyl acetate and washed with saturated aqueous sodium bicarbonate solution. The aqueous layer was separated and extracted with ethyl acetate, and the combined organic layers were concentrated under a stream of nitrogen and vacuum to yield (S)-1-acetyl-6-bromo-N-(4-fluorophenyl)-2-methyl-2,3-dihydropyrido[2,3-b]pyrazine-4(1H)-carboxamide. The crude product was dissolved in 1,4-dioxane (100 μL and 1-cyclopropyl-4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-1H-pyrazole (0.2 M solution in 1,4-dioxane, 0.27 mL, 0.054 mmol), potassium carbonate (1.0 M solution in water, 0.090 mL, 0.090 mmol) and [1,1′-bis(diphenylphosphino) ferrocene]dichloropalladium(II) dichloromethane adduct (0.02 M solution in 1,2-dichloroethane, 150 μL, 0.003 mmol) were added. The reaction was purged with nitrogen, and heated to 80° C. on a heater shaker for 4 hours. The reaction was diluted with ethyl acetate and washed with 1 N aqueous sodium hydroxide solution and brine. The combined organic layers were concentrated in a Genevac. The crude product was purified by mass triggered preparatory HPLC. The product-containing fractions were combined and concentrated to afford (S)-1-acetyl-6-(1-cyclopropyl-1H-pyrazol-4-yl)-N-(4-fluorophenyl)-2-methyl-2,3-dihydropyrido[2,3-b]pyrazine-4(1H)-carboxamide. MS (ESI, pos. ion) m/z 435 [M+H]+.

Provenance & Evidence