4.6- Diphenyl-2- -pyridazinone

IV-Methylation of polysubstituted pyridazinones is frequently accompanied by some side reactions, mainly substitutions. For example, methylation of 4-nitro-5,6-diphenyl-pyridazin-3(2//)-one with methyl iodide in the presence of sodium methoxide affords... 

Recently, several 5,6-diphenyl-3(2//)-pyridazinones (80, R = F, Cl) have been found to be active against murine P-388 leukaemia [287],... 

Reaction of the 2-acetoxy-3(2//)-furanones (526) with monosubstituted hydrazines gives good yields of the pyridazinium-5-olates (527) together with varying amounts of isomeric products. Alkyl derivatives (527 R = alkyl) have also been prepared by base-catalyzed alkylation (Mel, Me2SO4, PhCH2Cl) of 3-methyl-6-phenyl-5-ethoxycarbonyl-4( 1 //)-pyridazinone. Reduction of the diphenyl compound 527 (R = Ar = Ph) by zinc and hydrochloric acid gives 3-ethoxycarbonyl-5-hydroxy-5-methyl-l,2-diphenyl-2-pyrrolin-4-one (528 R = Ar = Ph) (Scheme 21... 

Several diazoalkanes have been shown to add as 1,3-dipoles to cyclopropenones. Diazomethane, diazoethane and diazopropane all add in this way to diphenylcyclopropenone to give the corresponding 3,5-diphenyl-4-pyridazinones (equation 66). An exception is 2-diazopropane which yields the diazoketone 73 ... 

Phenylpiperazine gave 4,6-diphenyl-2-(4-phenylpiperazm-l-yl) methyl-3(2//)-pyridazinone (216) [CH2O, 4,6-diphcnyl-3(277)-pyridazirione, EtOH—H2O, reflux, 12 h 79%]. ° ... 

Bicyclic lactams are uniquely suited as precursors for the synthesis of chiral substituted 4,5-dihydro-2H-pyridazinones. Thus, bicyclic lactams 112 with hydrazine dichloride in a dioxan/water mixture produced the desired 6-phenyl-4,5-dihydropyridazin-3-ones 113. However, reacting the bicyclic lactam with phenylhydrazine hydrochloride yields 2,6-diphenyl-4,5-dihydropyridazin-3-one 115 as a sole product (2004TL7799 Scheme 20). 

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