Action of pheynlmagnesium bromide on 4, 5, 6-trisubstituted pyridazin-3 [2H] -ones

ABSTRACT

BADDAR et al. studied the action of Grignard reagents on 6-aryl[1,2] and 6-methyl [3] pyridazln-3 [2H]-ones and reported that the reaction proceeds mainly by 1,4-addition to the C=-C-C=N system to give 4-suhstituted-4, 5 dihydropyridazin-3 [2H]-ones which, in most cases, undergo dehydrogenation to 4-substituted pyridazin-3[2H]-ones. In the present investigation the effect of introducing substituents in both 4-and 5-positions in the pyridazinone nucleus on the mode of addition of the Grignard reagent is studied. Some compounds of this type are now prepared by the base-catalysed condensation of 6-aryl-4, 5-dihydro-5-phen,ylpyridazin-3[2H]-ones [1] with formaldehyde and benzaldehyde to give the trisubstituled pyridazin-3 [2H]-ones [3]. These products are formed through aprototropic rearrangement of the originally formed product [2]. Similar results were previously reported for the reaction of aldehydes with 6-aryl-4,5 dihydropyri-dazin-3 [2H]ones [4,5]