1- Ethoxy-4- phthalazine

Quinoxalinyl, 4-cinnolinyl, and 1-phthalazinyl derivatives, which are all activated by a combination of induction and resonance, have very similar kinetic characteristics (Table XV, p. 352) in ethoxylation and piperidination, but 2-chloroquinoxaline is stated (no data) to be more slowly phenoxylated. In nucleophilic substitution of methoxy groups with ethoxy or isopropoxy groups, the quinoxaline compound is less reactive than the cinnoline and phthalazine derivatives and more reactive than the quinoline and isoquinoline analogs. 2-Chloroquinoxaline is more reactive than its monocyclic analog, 2-chloropyrazine, with thiourea or with piperidine (Scheme VI, p. 350). 

Phthalazine (59) with benzoyl chloride and potassium cyanide in aqueous methylene chloride (classical conditions) gave a mixture of 2-benzoyl-1, 2-dihydro-1-phthalazinecarbonitrile (60) and 2-benzoyl-1,2-dihydro-1-phtha-lazinol (61, R = H) [the latter isolated as 2-benzoyl-1-ethoxy-1,2-dihy-drophthalazine (61, R = Et) after recrystallization from ethanol] in variable ratio. 39,568 jjowever, only the nitrile (60) resulted when phthalazine and benzoyl chloride were treated in several improved ways [reactants, KCN, (PhCH2)Me3NCl, H2O, CH2CI2, 20°C, 3 h reactants, KCN,... 

A freshly prepared acetonic solution of 1,4-phthalazinequinone (171) with ethyl 2-amino-5-methyl-4,5-dihydro-3-furancarboxylate (172) gave 2-(3-ethoxy-carbonyl-2-imino-5-methyltetrahydrofuran-3-yl)-1,4(2//,370-phthalazined-ione (173) (AcOMe, -30°C 20°C, 30 min 76%). ... 

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