[CH3:1][C:2]1([CH3:20])[CH:7]=[C:6]([C:8]2[CH:13]=[CH:12][CH:11]=[CH:10][N:9]=2)[C:5]2[CH:14]=[C:15]([C:18]#[N:19])[CH:16]=[CH:17][C:4]=2[O:3]1>C(O)C.[Pd]>[CH3:1][C:2]1([CH3:20])[CH2:7][CH:6]([C:8]2[CH:13]=[CH:12][CH:11]=[CH:10][N:9]=2)[C:5]2[CH:14]=[C:15]([C:18]#[N:19])[CH:16]=[CH:17][C:4]=2[O:3]12.96 g of 2,2-dimethyl-4-(2-pyridyl)-2H-1-benzopyran-6-carbonitrile were dissolved in 100 ml of ethanol and added at room temperature to 100 mg of 10% palladium-on-charcoal. The mixture was shaken at room temperature under a hydrogen atmosphere for 2 hours. The catalyst was then removed by filtration and the filtrate was evaporated. The residue was chromatographed on silica gel using ethyl acetate/petroleum ether(1:2) for the elution. There were obtained 2.44 g of 3,4-dihydro-2,2-dimethyl-4-(2-pyridyl)-2H-1-benzopyran-6-carbonitrile of melting point 114°-115° C.
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