Reaction Steps
To a suspension of (E)-8-tert-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 benzene (10 mL), added thionyl chloride (1.0 mL), was refluxed for 2 h. The resulting solution was evaporated to dryness under reduced pressure, and the residue was dispersed in benzene (10 mL). The solvent was eliminated under reduced pressure. Dispersion in solvent and solvent elimination was repeated twice. The residue was dissolved in organic solvent benzene (10 mL) and added with stirring to a solution of the diethyl amine (0.09 g, 1.28 mmol). After 30 min at room temperature, the solvent was removed by evaporation under reduced pressure and extracted 3-fold with CHCl3 (30 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-tert-butyl-N,N-diethyl-2-oxo-6-(3-oxo-3-p-tolylprop-1-enyl)-2H-chromene-3-carboxamide (General Formula VI). (0.37 g, 65% yield). White solid, m. p. 170-171° C.; 1H NMR (CDCl3 300 MHz): δ 7.94 (d, J=8.1 Hz, 2H), 7.81-7.76 (m, 3H), 7.64 (d, J=1.7 Hz, 1H), 7.52 (d, J=15.7 Hz, 1H), 7.32 (d, J=8.0 Hz, 2H), 3.57 (q, J=7.1 Hz, 2H), 3.34 (q, J=7.0 Hz, 2H), 2.45 (s, 3H), 1.55 (brs, 9H), 1.28 (t, J=7.1 Hz, 3H), 1.21 (t, J=7.1 Hz, 3H); 13C NMR (CDCl3, 75 MHz): δ 189.7, 164.3, 157.3, 153.8, 144.0, 142.8, 141.7, 138.9, 135.4, 131.3, 129.8, 129.5, 128.8, 126.6, 126.2, 122.8, 119.2, 43.4, 39.6, 35.2, 29.8, 21.8, 14.3, 12.8; ESI-MS (m/z): 446 (M+H)+.
