From Pyridazine Derivatives as Substrates

Pyridazine substrates have been used in at least four ways to synthesize phthalazines with one synthon to supply C6, with one or two synthons to supply C6 -I- Cl, or with one synthon to supply C5 - - C6 - - C7 - - C8 of the product. The following classified examples illustrate these procedures. 

Ethyl 5-cyano-4- -methoxystyryl-6-oxo-1 -phenyl-1,6-dihydro-3-pyridazinecar-boxylate (140) with malononitrile gave ethyl 5-amino-6-cyano-7-p-methoxy-phenyl-4-oxo-3-phenyl-3,4-dihydro-l-phthalazinecarboxylate (141) reactants, Na, dioxane, reflux, 4h 70%) several analogs likewise.  

Ethyl 5-cyano-6-methyl-4-oxo-3-phenyl-3,4-dihydro-l-pyridazinecarboxylate (142) and a-benzyUdenemalononitrile gave ethyl 5-amino-6-cyano-4-oxo-3,7-diphenyl-3,4-dihydro-l-phthalazinecarboxylate (143) (reactants, piperidine, EtOH, reflux, 3h analogs likewise) or with ethyl 

2-cyanoacetate gave ethyl 5-amino-6-cyano-7-hydroxy-4-oxo-3-phenyl-3,4-dihydro-l-phthalazinecarboxylate (144) (similar conditions 75%).  

Diethyl 4,5-pyridazinedicarboxylate (145) with diethyl succinate gave diethyl 5,8-dioxo-2,3,5,8-tetrahydro-6,7-phthalazinedicarboxylate (146) (NaH, THE, reactants dropwise, reflux, 6h 10%).  

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From Pyridazine Derivatives as Substrates Using One Synthon to Supply C6 + C7 of the Phthalazine... 

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