[Br:1][C:2]1[CH:3]=[CH:4][C:5]([OH:18])=[C:6]([C:8](=[O:17])[CH2:9][C:10]2[CH:15]=[CH:14][CH:13]=[CH:12][C:11]=2[CH3:16])[CH:7]=1.[C:19](OC(=O)CC)(=O)[CH2:20][CH3:21].Cl>C(N(CC)CC)C>[Br:1][C:2]1[CH:7]=[C:6]2[C:5](=[CH:4][CH:3]=1)[O:18][C:19]([CH2:20][CH3:21])=[C:9]([C:10]1[CH:15]=[CH:14][CH:13]=[CH:12][C:11]=1[CH3:16])[C:8]2=[O:17]Intermediate 11 (3.0 g, 9.83 mmoles) was taken in a RB flask and to this triethylamine (25 ml) and propionic anhydride (4.00 g, 30.76 mmoles) were added and the mixture was refluxed for 24 h. After cooling to RT, the reaction mixture was acidified by the addition of 1N HCl solution, extracted with ethyl acetate, washed with sodium bicarbonate solution, dried with sodium sulphate and concentrated. The crude product was purified by column chromatography with ethyl acetate:petroleum ether to afford the title compound as colourless liquid (0.700 g, 20% yield). 1H-NMR (δ ppm, DMSO-d6, 400 MHz): δ 7.73 (d, J=2.5 Hz, 1H), 7.63 (dd, J=8.7, 2.5 Hz, 1H), 7.34 (t, J=4.8 Hz, 1H), 7.22-7.14 (m, 4H), 2.63 (q, J=7.5 Hz, 2H), 0.94 (t, J=7.5 Hz, 3H).
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