[CH3:1][C:2]1[O:3][C:4]2[C:9]([C:10](=[O:12])[CH:11]=1)=[CH:8][CH:7]=[CH:6][C:5]=2[CH:13]=O.[O:15]=[C:16]([CH3:22])[CH2:17][C:18]([O:20][CH3:21])=[O:19].C(O)(=O)C.N1CCCCC1>ClCCl>[CH3:1][C:2]1[O:3][C:4]2[C:9]([C:10](=[O:12])[CH:11]=1)=[CH:8][CH:7]=[CH:6][C:5]=2[CH:13]=[C:17]([C:16](=[O:15])[CH3:22])[C:18]([O:20][CH3:21])=[O:19]1 g (5.31 mmol) of 2-methyl-4-oxo-4H-chromene-8-carbaldehyde, 680 mg (5.84 mmol) of methyl 3-oxobutanoate, 456 μl (7.97 mmol) of acetic acid and 105 μl (1.06 mmol) of piperidine in 50 ml of anhydrous dichloromethane are stirred under reflux with a water trap for 24 h. After cooling, the reaction solution is diluted with dichloromethane (100 ml) and washed successively with saturated sodium bicarbonate solution and saturated sodium chloride solution. The organic phase is dried over magnesium sulfate and concentrated. The residue is recrystallized from isopropanol. 1.43 g (94% of theory) of the title compound are obtained as an E/Z mixture.
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