The Wittig condensation of 2-ethyl-2(E)-butenal (I) with triethyl phosphonoacetate (II) by means of NaH in benzene gives (2E,4E)-4-ethyl-2,4-hexadienoic acid ethyl ester (III), which is hydrolyzed with NaOH to the corresponding free acid (IV). The reaction of (IV) with ethyl chloroformate and then with ammonia affords the (2E,4E)-2-ethyl-2,4-hexadienamide (V), which is finally treated with NaNO2 in methanol adjusted at pH 3.0 with cond. HCl.