Reaction Steps
A solution of (E)-2-[[3-(3-methoxy-4-propargyloxyphenyl)-1-oxo-2-propenyl]amino]benzoic acid (0.5 g, 1.4 mmol) in acetic anhydride (3 mL) was −5 heated to reflux and stirred for 3 h. The reaction was cooled to rt and the resulting suspension was diluted with water. The suspension was stirred at rt for 1 h and the precipitate was collected by filtration, providing (E)-2-(3-methoxy-4-propargyloxystyryl)-4H-benzo[d][1,3]oxazin-4-one (0.44 g, 93%) as a yellow crystalline solid; mp 177-178° C.; δH (500 MHz, DMSO-d) 3.59 (m, 1H, C≡CH), 3.85 (s, 3H, OCH3), 4.85 (s, 2H, OCH2), 6.96 (d, J=16.0 Hz, 1H, CH═CHCO), 7.07 (d, J5,6=8.0 Hz, 1H, H5′), 7.34 (d, J5′,6=8.0, 1H, H6′), 7.49 (s, 1H, H2′), 7.57 (t, J3,4=J4,5=8.0 Hz, 1H, H4), 7.60 (d, J3,4=8.0 Hz, 1H, H3), 7.72 (d, J=16.0 Hz, 1H, CH═CHCO), 7.91 (t, J4,5=J5,6=8.0 Hz, 1H, H5), 8.11 (d, J5,6=8.0 Hz, 1H, H6); νC (125 MHz, DMSO-d6) 55.7, 55.9, 78.5, 79.0, 110.8, 113.6, 117.0, 117.2, 122.3, 126.5, 128.0, 128.1, 128.3, 136.8, 141.2, 146.8, 148.5, 149.4, 157.2, 158.8; HRMS (ESI) calculated for C20H15NO4 [M+H]+ 334.1074, found 334.1074; νmax 970, 1136, 1270, 1471, 1743, 2135, 3268 cm−1.
