Benzo cinnolines salts

When 2,2 -biphenyldiamines are tetrazotized and the resulting salts are heated, benzofurans are obtained, but benzo[c]cinnolines may be byproducts. This method has been litttle used. 2,3,7,8-Tetramethyldibenzo-furan (47) has been obtained in 40% yield from 4,4, 5,5 -tetramethyl-2,2 -biphenyldiamine by this method. " ... 

Although no new method for formation of simple pyridazino[3,4-f]pyridazines has appeared since the publication of CHEC-II(1996), a further method for the construction of benzo-fused derivatives has been described <1997CHE750>. Electrophilic attack of the diazonium salts formed from aromatic amines 5, with sodium nitrite in acetic acid, upon the neighboring methoxyarene results in formation of pyridazino[3,4-f]cinnolines 1. 

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,... 

The preparation of fluorobenzo[e]cinnolines 15 from the corresponding benzo[z]cinnolinamines 14 constitutes an example of the thermal Balz-Schiemann reaction in which the diazonium tetrafluoroborate intermediate is obtained from another previously formed diazonium salt.58... 

Benzo[c]cinnolines are often found as by-products of diazotization reactions of 2,2 -diaminobiphenyls. Reduction of the bisdiazonium salts from the diamines with sodium arsenite" or hypophosphorous acid ° increases the amounts obtained, although yields are usually low e.g., 10 is formed from 9 in 22% yield by this method. Alternative ionic and homolytic" mechanisms have been suggested for the process, each involving elimination of one of the diazonium groups as nitrogen. However, recent work by Rees and his co-workers has shown that at least part of the benzo[c]cinnolines... 

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. 

Like other cyclic compounds having a cis-azo linkage, benzo[c]cinnoline forms fairly stable complexes with many transition metal salts.These all have a 1 1 ligand metal ratio except in the case of palladium(II) chloride, where a 2 1 complex has been isolated.Benzo[c]cinnoline 5-oxide also gives 2 1 complexes with palladium(ll) chloride and with silver nitrate. " A nickel(O) complex, Ni(PEt3)2(benzo[c]cinnoline)2, has been obtained by reaction with biscyclooctadiene nickel and triethylphosphine in hexane. " ... 

The quaternization of (benzo)pyridazines by alkyl halides (these systems are not readily susceptible to arylation) was reviewed in CHEC-I <84CHEC-l(3B)l>. Monoquaternization of pyridazines occurs more readily than other diazines but less readily than pyridine, reflecting the intermediate basicity/nucleophilicity of pyridazine. Diquaternization of pyridazine can only be achieved with oxonium salts, particularly Me30 BF4 . As with protonation and A-oxidation, mixtures of products are often obtained on quaternization of unsymmetrical pyridazines and have been the subject of theoretical studies. A number of 2-(ribofuranosyl)-3(2//)-pyridazinones have been prepared by stannic chloride catalyzed alkylation of 3-(trimethylsilyloxy)pyridazines with protected 1-0-ace-tylribofuranose <83JHC369>. The quaternization behavior of phthalazines is similar to that of pyridazines, but with cinnolines alkylation usually occurs at N-2, unless there is a particularly bulky substituent at C-3. 

The N -unsubstituted N-imines are usually generated in situ by treatment of the N-aminoazonium salts with base and used directly for subsequent reactions because of the instability of the N-imines (Eq. 1). Some N-imines such as quinoline, isoquinoline, and phenanthridine N-imines are known to form crystalline dimers,17 which are in equilibrium with the N-imines in solutions.29 The only exception is benzo[c]cinnoline N-imine which is isolable as a stable crystalline solid.44... 

Early reports indicate that N-aminopyridinium salts react with aromatic aldehydes in the presence of base to give nitriles as the major products.1 Completely different reaction courses emerge when the l-methyl-3-amino-benzimidazolium salt 23 and 2-methyl-3-aminobenzothiazolium salt 25 are allowed to react with benzaldehyde under the similar conditions, affording a benzaldehyde phenylhydrazone 24151 and a 2,3-dihydro-1,3,4-benzothia-diazine 26,152 respectively likely reaction pathways are suggested in Eqs. (16) and (17). Benzo[c]cinnoline JV-imine reacts with p-anisaldehyde to give the bis-lV-imine 27.44... 

Cinnolines, one of the two benzo derivatives of pyridazines, received considerable attention due to the pharmacological activities exhibited by these hcterocycles. Hydrazones 152, prepared by coupling aryl diazonium salts with the enaminones 151 <01T1609>, were... 

As illustrated in eqs. 1 and 2, azobenzene, azotoluene, and benzo[c]cinnoline have been found to undergo net [2+2] cycloaddition of their N=N double bond across the R C triple bond of the BPh4 salt of carbyne complex 1 [3]. These reactions represent the... 

Benzo[c]cinnolines from 9,10-dihydro-9-aza-10-boraphenanthrenes s. 19, 541 Sodium salt Na ... 

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