[CH:1](=O)[C:2]1[CH:7]=[CH:6][CH:5]=[CH:4][CH:3]=1.[C:9]([O:16][CH2:17][CH3:18])(=[O:15])[CH2:10][CH2:11][C:12]([CH3:14])=[O:13].C(O)(=O)C.N1CCCCC1>C1C=CC=CC=1.CCOCC>[CH2:17]([O:16][C:9](=[O:15])[CH2:10][CH2:11][C:12](=[O:13])[CH:14]=[CH:1][C:2]1[CH:7]=[CH:6][CH:5]=[CH:4][CH:3]=1)[CH3:18]Benzaldehyde 69a (5.40 g, 50 mmol) and ethyl levulinate 97 (7.21 g, 50 mmol) were dissolved in benzene (25 mL) then glacial acetic acid (6 mL) and piperidine (2 mL) were added. The solution was stirred and refluxed under a Dean-Stark trap under argon for 5 hr. The solution was cooled and diluted with ether and washed twice with 2M HCl, 5% NaHCO3 brine and evaporated to give an oil 11.0 g, 95%. 1H NMR (300 MHz, CDCl3) δ 1.27, 3H, t(J 7.1); 2.69, 2H, t(J 6.7); 3.02, 2H, t(J 6.7); 4.16, 2H, q(J 7.1); 6.77, 1H, d(J 16.2); 7.37-7.43, 3H, m; 7.51-7.60, 2H, m; 7.60, 1H, d(J 16.4). 13C NMR (CDCl3) 14.2, 28.2, 35.2, 60.7, 125.8, 128.3, 128.9, 130.5, 134.4, 142.9, 172.9, 198.1.
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