Acetic Acid → 2-(4-(Hydroxyimino)cyclohexa-2,5-dien-1-ylidene)-2-phenylacetonitrile

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60 g of KOH are dissolved in 300 ml of methanol and heated up to 55° C. To the solution are added 32.2 g (0.27 mol) of phenylacetonitrile followed by 30.8 g (0.25 mol) of nitrobenzene. The reaction mixture is stirred at 55° C. for 4 h. After cooling, 400 ml of water are added with stirring. The resulting solution is acidified by addition of 110 ml of acetic acid in 100 ml of water, leading to a yellow-orange precipitate. The mixture is then filtered, and the yellow solid is washed with a mixture of methanol and water. The crude product is dried in air, boiled with 150 ml of benzene for 15 min., cooled, filtered and dried under vacuum. 42.6 g (77%) of (4-hydroxyimino-cyclohexa-2,5-dienylidene)-phenyl-acetonitrile are obtained in the form of a yellow solid, having a melting point (mp) of 159-163° C. (dec.). The structure is confirmed by the 1H-NMR spectrum (CDCl3), δ [ppm]: 6.75(Z)/6.89(E) (dd, 1H), 7.08(Z)/7.15(E) (dd, 1H), 7.25-7.53 (m, 7H), 9.56 (br s, 1H). 1H-NMR reveals that the product is a 50:50 mixture of Z and E isomers. The signals are tentatively assigned to Z and E isomers. 1.2: (4-Diethoxyphosphoryloxyimino-cyclohexa-2,5-dienylidene)-phenyl-acetonitrile 8 g (36 mmol) of (4-hydroxyimino-cyclohexa-2,5-dienylidene)-phenyl-acetonitrile are dissolved in 90 ml of tetrahydrofuran (THF) and cooled in an ice bath. After adding 6.8 g (39 mmol) of diethylphosphoryl chloride to the solution, 5.4 g (54 mmol) of triethylamine are added dropwise, keeping the temperature below 5° C. The reaction mixture is gradually warmed to room temperature, and stirred for 1 h. The reaction mixture is poured into 100 ml of water, and extracted with ethyl acetate. The organic phase is washed with 0.1 N hydrochloric acid solution, water, and sodium chloride solution. The organic phase is dried over MgSO4, the solvent is distilled off, and the residue is purified by flash chromatography on silica gel with ethyl acetate—hexane (1:1) as eluent. The product is a brown liquid. The structure is confirmed by the 1H-NMR spectrum (CDCl3); δ [ppm]: 1.37-1.44 (m, 6H), 4.23-4.36 (m, 4H), 6.84(Z)/6.97(E) (dd, 1H), 7.17(Z)/7.21(E) (dd, 1H), 7.26(E)/7.38(Z) (dd, 1H), 7.46-7.55 (m, 6H). 1H-NMR reveals that the product is a 67:33 mixture of Z and E isomers. The signals are tentatively assigned to Z and E isomers.

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