From Heteropolycyclic Derivatives as Substrates

Also many other examples of both types. 

The conversion of these substrates into phthalazines is interesting rather than useful in its present state of development. The lead tetracetate oxidation of 4,7-diphenyl-17/-1,2,3-triazolo[4,5-tf]pyridazin-l-amine (301) in the presence of 2,3,4,5-tetraphenyl-l-cyclopentadienone (302) gave 1,4,5,6,7,8-hexaphenylphtha-lazine (303) [reactants, CaO, CH2CI2, Pb(OAc)4 portionwise, 20°C, min 20% see original with respect to mechanism].  

Derivatives of 16 heteropolycyclic systems have been used as substrates for the preparation of phthalazines, but none extensively. Accordingly, each such procedure is illustrated by one or more examples that are arranged alphabetically according to parent system used as substrate. 

7-Dihydro-lf/,3//-benzo[l,2-c 4,5-c ]difuran-l,3,5,7-tetrone (304) gave 1,4-dioxo-l,2,3,4-tetrahydrophthalazine-6,7-dicarboxylic acid as its dihydrazi-nium salt (305) (substrate, H2NNH2 H2O, Me2NCHO, N2, reflux, 12 h  

Dimethyl 6,7-dihydro-5,8-epidioxyphthalazme-l,4-dicarboxylate (308) underwent reductive fission of its 9,10-bond by thiourea to afford dimethyl 

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From Heteropolycyclic Derivatives as Substrates Furo- or Thieno[3,4- ]phthalazines as Substrates... 

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