[CH2:1](O)[CH:2]=[CH:3][C:4]1[CH:9]=[CH:8][CH:7]=[CH:6][CH:5]=1.C([O:13]/[C:14](/[CH3:21])=[CH:15]\[C:16]([O:18][CH2:19][CH3:20])=[O:17])C>P(=O)(O)(O)O.C(O)C>[C:14]([CH:15]([CH:3]([C:4]1[CH:9]=[CH:8][CH:7]=[CH:6][CH:5]=1)[CH:2]=[CH2:1])[C:16]([O:18][CH2:19][CH3:20])=[O:17])(=[O:13])[CH3:21]The starting material was prepared as follows. To a mixture of 4.02 g of cinnamyl alcohol and 6.6 g of ethyl β-ethoxycrotonate was added 10 mg of phosphoric acid. The resulting mixture was heated to a temperature of 150° C. over a period of about 40 minutes and then heated at 150° C. for 4 hours with stirring while the ethanol formed during the reaction was distilled off. Thereafter, the reaction mixture was distilled to give 6.3 g (81% yield) of ethyl 2-acetyl-3-phenyl-4-pentenoate, boiling point 170°-174° C./20 mmHg.
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