A solution of sodium hydroxide (0.8 g; 0.02 mol) in 30 ml of methanol is added to a suspension of 4-{4-[4-(3-cyano-propenyl)-benzyl]-phenyl}-but-3-enenitrile (3.0 g; 0.01 mol), prepared as described in example 6.2, in 20 ml of methanol. Methyl nitrite, generated from 2.07 g (0.03 mol) of sodium nitrite as described in example 2.2, is bubbled through the suspension at 2° C. for 25 min, and the mixture is then left at room temperature for 48 h. The solvent is then evaporated, the residue is dissolved in 200 ml of water, extracted with toluene (the extract is discarded), and acidified with conc. hydrochloric acid. The beige precipitate is taken up in ethyl acetate, washed neutral with water, dried (MgSO4) and concentrated by evaporation. 2.7 g (76%) of 4-{4-[4-(3-cyano-3-hydroxyimino-propenyl)-benzyl]-phenyl}-2-hydroxyimino-but-3-enenitrile are obtained as a light brown solid, melting point 142-145° C. (dec).
