2-(6-cyano-3,4-dihydro-2,2-dimethyl-2H-1-benzopyran-4-yl)pyrimidine 1-oxide → 4-[1,1-Dimethyl-3-(2-pyrimidinyl)-2-propynyloxy]benzonitrile

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The 3,4-dihydro-2,2-dimethyl-4-(2-pyrimidinyl)-2H-1-benzopyran-6-carbonitrile used as the starting material was prepared as follows: (A) 0.63 g of 4-(1,1-dimethyl-2-propynyloxy)benzonitrile, 0.75 g of 2-iodopyrimidine, 18 mg of triphenylphosphine, 12 mg of palladium(II) chloride and 3.5 mg of copper(I) iodide were stirred overnight in 20 ml of triethylamine under nitrogen. The mixture was evaporated to dryness and then ethyl acetate and water were added. The organic phase was dried over sodium sulphate and evaporated. The residue was chromatographed on silica gel using ethyl acetate/petroleum ether (1:3) and subsequently ethyl acetate/petroleum ether (1:1) for the elution. There were obtained 580 mg of 4-[1,1-dimethyl-3-(2-pyrimidinyl)-2-propynyloxy]benzonitrile as an oil. (B) 580 mg of 4-[1,1-dimethyl-3-(2-pyrimidinyl)-2-propynyloxy]benzonitrile were heated at reflux for 3 hours in 20 ml of dichlorobenzene. The solution was allowed to cool and was then evaporated to dryness. The residue was chromatographed on silica gel using ethyl acetate/petroleum ether (1:2) and subsequently ethyl acetate/petroleum ether (1:1) for the elution. There was obtained 361 mg of 2,2-dimethyl-4-(2-pyrimidinyl)-2H-1-benzopyran-6-carbonitrile which melted at 108°-109.5° C. after recrystallization from tert-butyl methyl ether. (C) 1.0 g of 2,2-dimethyl-4-(2-pyrimidinyl)-2H-1-benzopyran-6-carbonitrile was dissolved in 100 ml of ethanol, added to 10% palladium-on-charcoal and shaken under an atmosphere of hydrogen at room temperature. After 2 hours the catalyst was filtered off and the filtrate was evaporated. The residue was chromatographed on silica gel using ethyl acetate/petroleum ether (1:1) for the elution. The product was recrystallized from cyclohexane to give 0.5 g of 3,4-dihydro-2,2-dimethyl-4-(2-pyrimidinyl)-2H-1-benzopyran-6-carbonitrile of melting point 109°-111° C.

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