Cesium carbonate → 4-(Cyclopropanecarbonyl-amino)-3-methyl-benzofuran-2-carboxylic acid ethyl ester

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To 3-methyl-4-trifluoromethanesulfonyloxy-benzofuran-2-carboxylic acid ethyl ester (300 mg, 0.85 mmol, 1 eq, prepared according to Example 20, Step 1) in 8 mL of dioxane under nitrogen were added cyclopropyl carboxamide (87 mg, 1.02 mmol, 1.2 eq), Pd2 (dba)3 (16 mg, 0.017 mmol, 0.02 eq), 4,5-bis(diphenylphosphino)-9,9-dimethylxanthene (30 mg, 0.051 mmol, 0.06 eq), and cesium carbonate (390 mg, 1.19 mmol, 1.4 eq). The reaction mixture was heated at reflux for 72 h. After work up and column chromatography (dichloromethane/hexanes), 4-(cyclopropanecarbonyl-amino)-3-methyl-benzofuran-2-carboxylic acid ethyl ester was obtained in 98% yield (238 mg). 1H NMR (400 MHz, DMSO-d6) δ ppm 0.8 (m, 4 H) 1.3 (t, J=7.1 Hz, 3 H) 1.8 (s, 1 H) 2.6 (s, 3 H) 4.4 (q, J=7.2 Hz, 2 H) 7.2 (d, J=7.1 Hz, 1 H) 7.5 (m, 1 H) 7.5 (m, 1 H) 10.1 (s, 1 H).

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