反应详情

By stirring 3.02 g of 4-cyanobenzaldehyde and 7.32 g of acetonylidene-triphenylphosphorane in 50 ml of dichloromethane and then recrystallizing from isopropanol, 3.15 g (80%) of 4-(3-oxobutenyl)-benzonitrile is obtained. 1.71 g of it is mixed in 20 ml of dichloromethane with 20 ml of a 0.5 M solution of bromine in dichloromethane. After decolorization, the solvent is drawn off in a vacuum. The remaining oil is refluxed with 0.95 g of imidazole and 7 ml of triethylamine in 40 ml of toluene for 2 hours. A precipitate is filtered off, the filtrate is distributed in ethyl acetate-2M hydrochloric acid, the hydrochloric acid phase is alkalized with potassium carbonate and extracted with ethyl acetate. 1.2 g of a crude product is obtained, which, after recrystallization from isopropanol, yields the Z-isomer with mp. 131°-135° C. After chromatography of the mother liquor on silica gel (eluant ethyl acetate), the E-isomer is obtained from ethyl acetate/ether as crystals of mp: 123°-126° C.

1. customrecrystallizing from isopropanol