Reaction Steps
To a suspension of (E)-8-sec-butyl-2-oxo-6-(3-oxo-3-p-tolylprop-1-enyl)-2H-chromene-3-carboxylic acid of the formula (V) (0.5 g, 1.28 mmol) in CCl4 (15 mL), added thionyl chloride (1.0 mL), was refluxed for 2.5 h. The resulting solution was evaporated to dryness under reduced pressure, and the residue was dispersed in CCl4 (10 mL). The solvent was eliminated under reduced pressure. Dispersion in CCl4 and solvent elimination was repeated twice. The residue was dissolved in CCl4(10 mL) and added with stirring to a solution of the methyl amine (0.04 g, 1.28 mmol). After 40 min at room temperature, the solvent was removed by evaporation under reduced pressure and extracted 3-fold with CHCl3 (25 mL). The combined organic layers were dried on Na2SO4, filtered, and concentrated to dryness under reduced pressure. The residue was chromatographed over silica gel (SiO2, 230-400 flash), eluting with a gradient of 20% ethyl acetate in hexane to 40% ethyl acetate in hexane, which upon concentration provides (E)-8-sec-butyl-N-methyl-2-oxo-6-(3-oxo-3-p-tolylprop-1-enyl)-2H-chromene-3-carboxamide (General Formula VI). (0.33 g, 65% yield). White solid, m. p. 215-216° C.; 1H NMR (CDCl3 300 MHz): δ 8.93 (s, 1H), 8.72, (brd, J=4.6 Hz, 1H) 7.96 (d, J=8.1 Hz, 2H), 7.83-7.77 (m, 3H), 7.55 (d, J=15.7 Hz, 1H), 7.33 (d, J=8.0 Hz, 2H), 3.49-3.37 (m, 1H), 3.04 (d, J=4.9 Hz, 3H), 2.45 (s, 3H), 1.80-1.71 (m, 2H), 1.35 (d, J=6.9 Hz, 3H), 0.94 (t, J=7.4 Hz, 3H); 13C NMR (CDCl3, 75 MHz): δ 189.5, 1610, 161.2, 153.1, 148.5, 144.1, 142.2, 136.5, 135.4, 132.2, 131.4, 129.5, 128.8, 127.1, 123.2, 119.0, 118.8, 33.6, 29.8, 26.7, 21.8, 20.6, 12.1; ESI-MS (m/z): 404 (M+H)+.
