Mannich reaction and cyanoethylation of some 6 [-styryl] pyridazinone derivatives

ABSTRACT

Many pyridazine derivatives are known to have marked biological effect being fungicides, herbicides, and central nerve depressants. Recently, 4-styrylpyridazines were found to inhibit choline acetyltransferase in vitro. The present investigation deals with the synthesis of some 2-substituted 6[infinity-styryl] pyridazinones. When 4, 5-dihydro-6 [alpha-styryl] pyridazin-3 [2H]-ones [1 a and b] were allowed to react with acrylonitrile they underwent cyanoethylation to give fairly good yields of 2- [2'-cyanoethyl]*4,5-dihydro-6 [infinity-styryl] pryidaœin-3 [2H]-ones [3 a and b], respectively. The structure of 3 was confirmed by [i] Microanalytical data [II] their infrared spectra lack the NH stretching frequencies while they show strong absorptions characteristic of vco and vC=N [Table 1]. These spectral features exclude the possibility of attack at C[4] leading to the formation of [2], [iii] the alkaline hydrolysis of these compounds gave the corresponding acids namely 2-[2-carboxyethyl]-4,5-dihydro-6 [infinity styryl]pyridazin-3 [2H]-ones [4a and b] whose infrared spectra lack the C=N stretching frequencies while they show the carbonyl stretching frequencies of both pyridazinone system and carboxylic acids in addition to broad absorptions in the 3 micro region characteristic of the polymeric hydroxyl groups of carboxylic acids