1 //-Benzo cinnolines synthesis

Cinnolin-4(lH)-one, 8-hydroxy-iodination, 3, 21 Cinnolin-4-ones synthesis, 3, 56 Circular dichroism indolizidines, 4, 450 pyridines and benzo derivatives, 2, 126... 

The annelation of benzo rings on pyridazines was covered in CHEC-II(1996) <1996CHEC-II(6)1>. Maes and Matyus reported new examples in their synthesis of the dibenzo[// ]phthalazin-l(27r)-one and dibenzo[//]cinnolin-3(27/)-one skeleton. Palladium-catalyzed intramolecular arylation of 2-benzyl-5-(2-bromophenyl)-4-phenylpyridazin-3(2//)-one yielded 2-benzyldibenzo[/,4]phthalazin-l(2//)-one. The synthesis of this new tetracyclic pyridazinone from 2-benzyl-5-(2-aminophenyl) -phenylpyridazin-3(2//)-one via a Pschorr-type reaction was also investigated. Similarly, the con-stmction of 2-methyldibenzo[/, ]cinnolin-3(2//)-one from 2-methyl-5-(2-bromophenyl)-6-phenylpyridazin-3(27T)-one and 2-methyl-5-(2-aminophenyl)-6-phenyl-pyridazin-3(2//)-one was performed <2003T5919>. 

In the synthesis of symmetrically 3,8-disubstituted benzo[c]cinnolines 52 from the corresponding 4,4-disubstituted 2,2-dinitrobiphenyls 51, acetophenone has been used as reductant in a basic solution (Scheme 26) 2-nitroso-2-hydroxylaminobiphenyls are assumed to be intermediates in this reaction <2004JOC7720, CHEC-III(8.01.9.1)73>. 

Benzo[c]cinnolines, 24, 151 1,5-Benzodiazepines, 17, 27 Benzo[l>]furan and derivatives, recent advances in chemistry of. Part 1, occurrence and synthesis, 18, 337 Benzo[c]furans, 26, 135 Benzofuroxans, 10, 1 29, 251 2//-l-Benzopyrans (chrom-3-enes), 18, 159 Benzo[c)pyrylium salts syntheses,... 

Pyridazine was first synthesized by Tauber, who oxidized benzo[c]cinnoline to 3,4,5,6-pyridazinetetracarboxylic acid which was subsequently decarboxylated. All other syntheses of pyridazine, however, involve nuclear synthesis and are in the main cumbersome and characterized by poor yields. The reaction between a 1,4-ketoacid... 

Benzo[c]cinnoline is a weak base with a of 2.2 in water and 1.6 in 50% aqueous ethanol.Cryoscopic measurements show that it is dipro-tonated to some extent in 100% sulfuric acid. Well-defined quaternary salts result from heating benzo[c]cinnoline with alkyl halides and sul-fates. These are reported to decompose on treatment with ammonia, regenerating benzo[c]cinnoline, but apparently nucleophilic displacements of halogen by amines have been carried out on certain highly substituted examples in the synthesis of cationic dyestuffs. Quaternizations of benzo[c]cinnoline with a,a)-dibromo-propane and -butane are accompanied by hydrogen bromide elimination to give the cyclic iminium salts 40 and 41. When 40 is dehydrogenated, or merely refluxed in ethanol. 

Benzo[c] cinnoline aldehydes are as yet unknown. The 2- and 3-acetyl derivatives have been prepared, but the majority of known compounds relevant to this section are mono- and dicarboxylic acid derivatives. These include the 2-, - - 3-, ° and 4. - o2.J55,i57 monoacids and esters, the lactone of 10-hydroxybenzo[c]cinnoline-l-carboxylic acid, some halogeno- and methyl-substituted 2- and 4. carboxylic acids, and the 2,9-, 3,8-, - - and 4,7- dicarboxylic acids and derivatives. These compounds have been obtained by ring synthesis, or, in the case of 2-methylbenzo[c]dnnoline-9-carboxylic acid, by side-chain oxidation, " rather than by the introduction of substituents into benzo[c] cinnoline. Benzo[c]cinnoline-l-carbonitrile has been prepared, albeit in low... 

Nitration of benzo[c]cinnoline (Section IV,B) gives the 1-nitro, 4-nitro, and 1,10-dinitro derivatives, the first being the most readily available. Others, such as 2- and 3-nitrobenzo[c]cinnolines, are obtainable by nonreductive ring synthesis methods. The 2-phenylazo compound has also been described. ... 

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