Using l-Aldehydo-2-alkoxycarbonylbenzenes as Substrates

Although seldom used, such substrates also give l(2//)-phthalazinones. Thus diethyl 4-formyl-2,6-dimethylisophthalate (50) with hydrazine hydrate gave ethyl 5,7-dimethyl-4-oxo-3,4-dihydro-6-phthalazmecarboxylate (51) (EtOH, reflux, 3h  

Such substrates clearly should afford 1-phthalazinamines, but the only reported examples underwent concomitant or subsequent hydrolysis under the conditions of cyclocondensation to give the corresponding phthalazinones 3-formylphthalonitrile (52) gave 4-oxo-3,4-dihydro-5-phthalazinecarbonitrile (53) (H2NNH2 H2O, 12M HCl, PhH, reflux, 6h 66%).  

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