Cinnolin-4-ones, formation

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. 

Cyclopent-2-en-l-one, 2-hydroxy-3-methyl-synthesis, 3, 693 Cyclopentenone, 4-methoxy-formation, 1, 423 Cyclopenthiazide as diuretic, 1, 174 Cyclopent[2,3-d]isoxazol-4-one structure, 6, 975 Cydophane conformation, 2, 115 photoelectron spectroscopy, 2, 140 [2,2]Cydophane conformation, 2, 115 Cyclophanes nomenclature, 1, 27 Cyclophosphamide as pharmaceutical, 1, 157 reviews, 1, 496 Cydopiloselloidin synthesis, 3, 743 Cydopolymerization heterocycle-forming, 1, 292-293 6 ff-Cy clopropa[5 a,6a]pyrazolo[ 1,5- a]pyrimidine pyrazoles from, S, 285 Cy dopropab enzopy ran synthesis, 3, 700 Cydopropachromenes synthesis, 3, 671 Cyclopropa[c]cinnolines synthesis, 7, 597 Cyclopropanation by carbenes... 

Another synthesis of pyrimido[5,4-c]cinnolin-4(3//)-ones (59) via 4-aminocinnolines (56) starts with arylhydrazono-cyanoacetic acid derivatives (58). Upon heating in the presence of A1C13 4-aminocinnolines (56) are formed. Cyclocondensation with formamide or triethyl ort/io-formate affords the pyrimido[5,4-c]cinnolin-4(3/7)-ones (59) (Scheme 10) <92JPS365>. 

Facile formation of hydrophilic derivatives of11-[2-(N,N-dimethylamino)ethyl]-2,3-dimethoxy-8,9-methylenedioxy-11H-isoquino[4,3-c]cinnolin-12-one (ARC-31) and its 11-deaza analog, ARC-111... 

Cinnolines are another relatively unfamiliar class of heterocycle. A synthesis employing tandem C—N bond formations has recently been reported by the Willis research group. Continuing their use of key 2-(2-haloalkenyl)aryl halide substrates, they demonstrated that when combined with diethyl hydrazine-1,2-dicarboxylate, these substrates could undergo tandem copper-catalyzed alkenylation and arylation processes to generate novel diethyl dihydrocinnoline-l,2-dicarboxylates such as 56 [108]. These intermediates could be isolated and then treated with aqueous sodium hydroxide to reveal cinnoline products, such as 57, in moderate to excellent yields as shown in Scheme 24.28. Alternatively, the aromatic products could be revealed by treatment with sodium hydroxide in situ in a one-pot process. 

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