Dimethylformamide → 5'-Ethoxy-2'-fluorobiphenyl-2-carbonitrile

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Under argon, 5-ethoxy-2-fluorophenylboronic acid (300 mg, 1.63 mmol), potassium phosphate (433 mg, 2.04 mmol) and tetrakis(triphenylphosphine)palladium(0) (57 mg, 0.05 mmol) were dissolved in abs. N,N-dimethylformamide (8 ml), and the mixture was stirred at room temperature for 5 minutes. 2-Chlorobenzonitrile (112 mg, 0.82 mmol) was then added, and the reaction mixture was stirred at 160° C. for 4 h. After cooling to room temperature, water (>100 ml) was added and the aqueous phase was repeatedly extracted thoroughly with ethyl acetate. The combined organic phases were dried over magnesium sulphate, filtered off and concentrated under reduced pressure. Purification of the residue that remained by column chromatography (gradient ethyl acetate/n-heptane) gave 5′-ethoxy-2′-fluorobiphenyl-2-carbonitrile (150 mg, 76% of theory) in the form of a colourless solid. 5′-Ethoxy-2′-fluorobiphenyl-2-carbonitrile (150 mg, 0.62 mmol) was then dissolved in methanol (5 ml), finely powdered potassium hydroxide (174 mg, 3.10 mmol) was added and the mixture was stirred under reflux conditions for 2 h. After cooling to room temperature, the reaction mixture was concentrated under reduced pressure, water was added and the resulting precipitated solid was filtered off and dried. This gave 2-ethoxyphenanthridin-6(5H)-one (72 mg, 46% of theory) as a colourless solid. 1H-NMR (400 MHz, d6-DMSO δ, ppm) 11.58 (br. s, 1H, NH), 8.56 (d, 1H), 8.32 (d, 1H), 7.86 (d, 1H), 7.82 (dd, 1H), 7.64 (dd, 1H), 7.29 (d, 1H), 7.13 (dd, 1H), 4.17 (q, 2H), 1.39 (t, 3H).

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