7- Nitro-2-phenyl-1 -phthalazinone

Morpholino-l//-2-benzopyran-l-one (177) with p-nitrobenzenediazonium tet-rafluoroborate gave a separable mixture of 4-morpholinoformyl-2-p-nitro-phenyl-l(27/)-phthalazinone [178, R = C0N(CH2CH2)20] and 2-p-nitro-phenyl-l(27/)-phthalazinone (178, R = H) (reactants, Et3N, MeCN, 20°C,... 

When large groups, such as phenyl, bromo, ethoxycarbonyl or nitro are attached at position 3, the principal products are l-alkylcinnolin-4(l/f)-ones. Cyanoethylation and acetylation of cinnolin-4(l/f)-one takes place exclusively at N-1. Phthalazin-l(2/f)-ones give 2-substituted derivatives on alkylation and acylation. Alkylation of 4-hydroxyphthala2in-l(2/f)-one with an equimolar amount of primary halide in the presence of a base leads to 2-alkyl-4-hydroxyphthalazin-l(2/f)-one and further alkylation results in the formation of 4-alkoxy-2-alkylphthalazinone. Methylation of 4-hydroxy-2-methyl-phthalazinone with dimethyl sulfate in aqueous alkali gives a mixture of 4-methoxy-2-methylphthalazin-l(2/f)-one and 2,3-dimethylphthalazine-l,4(2//,3//)-dione, whereas methylation of 4-methoxyphthalazin-l(2/f)-one under similar conditions affords only 4-methoxy-2-methylphthalazinone. 

Bromo-6-nitro-l,3-dihydro-l-isobenzofuranone (213) gave 7-nitro-2-phenyl-l(2//)-phthalazinone (214) (3M HCl, reflux, briefly then PhNHNHai, 20°C, 1 h 73%) analogs likewise." "... 

Methyl-2-[2-nitro-5-(pyrrolidin-l-yl)phenyl]-l(2//)-phthalazinone (14, R = NO2) underwent a one-pot reduction to the corresponding amino analog (14, R = NH2) and dehydrative cyclization to give 5-methyl-9-(pyrrolidin-l-yl)benzimidazo[2,l-fl]phthalazine (15) (substrate, polyphosphoric acid, 100°C Fe powderj, portionwise then 140°C briefly 25%). ... 

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