Quinolines quinolinium salts

Pyrimido[4,5-6]quinolinium salts pseudo bases - ring opening, 3, 208 Pyrimido[4,5-6]quinolinium salts, 4-chloro-hydrolysis, 3, 214 Pyrimido[4,5-6]quinolinones synthesis, 3, 228 Pyrimido[4,5 -6]quinolin-5-ones synthesis, 3, 221-222 Pyrimidothiadi azoles reactions, 6, 533 Pyrimidothiazines synthesis, 4, 527 Pyrimidothiazinones mass spectra, 2, 23... 

Quinoline-5-sulfonic acid, 8-hydroxy-7-iodo-metal complexes absorptiometry, 1,549 Quinolinium salts in gravimetry, 1, 535 Quinolinol metal complexes color photography, 6,107 8-Quinolinol biological activity, 6, 771 gallium and indium complexes radiopharmacology, 6, 971 radionuclide complexes radiopharmacology, 6,994 8-Quinolyl sulfate hydrolysis metal catalysis, 6,465 Quinones... 

Quinolinium salts, in Mills reaction, 37.40 2.2 -Quinoline rnonomethine cyanine. 

Acids and Lewis acids react with quinoline at the basic nitrogen atom to form quinolinium salts, and there is a question over the nature of the substrate for electrophilic attack, i.e. is it quinoline or the quinolinium cation The answer is not a simple one and appears to depend upon the reagents and reaction conditions. Thus, whereas acetyl nitrate at 20 °C gives mainly 3-nitroquinoline (Scheme 3.2), fuming nitric acid in concentrated sulfuric acid containing sulfur trioxide at 15-20 °C yields a mixture of 5-nitroquinoline (35%) and 8-nitroquinoline (43%) (Scheme 3.3). In the case of acetyl nitrate, the reaction may proceed by the 1,4-addition of the reagent to quinoline, followed by electrophilic attack upon the 1,4-dihydro derivative. 

A By reacting quinoline with benzyl bromide in an inert solvent, such as diethyl ether, the corresponding quinolinium salt is obtained (Scheme 3,12), Treatment of this product with sodium... 

Phosphamethin-cyanines, like methin-cyanines, can be protonated by strong acids, forming colorless dications. These can be converted back to the original phosphamethin-cyanines by careful addition of weak bases such as tert.-butanol. This acid-base reaction is least successful in the case of the weakly basic bis-benzthiazole-phosphamethin-cyanine 6. For bis-quinoline-phosphamethin-cyanine 7 b, we obtained vnth perchloric acid in glacial acetic acid the absorption spectrum of the N-ethyl-quinolinium salt. 

IV. Complex Metal Hydride Reduction of Quinolines and Quinolinium Salts... 

The reduction of quinolinium salts or quinolines with lithium aluminum hydride gives predominantly the 1,2-dihydroquino-lines.78,92, 95- 97-103 The yield of product appears to depend upon the... 

Fig. 133. Formation of quinolines and quinolinium salts from P-arylamino ketones.

The reaction has been used to synthesize libraries of benzonaphthyridines 196, in high diastereoselectivity, from the cycloaddition of 1,4-dihydrop3Tidines with imines formed from aldehydes and anilines. When cyclic enol ethers were used as dienophUes, mixtures of diastereomers 197 were obtained. These compounds were oxidized to the corresponding quinolines 198 and were further transformed to the quinolinium salts 199 as shown in Scheme 36 [76]. Compounds 196 and 198 were tested for their ability to inhibit human propyl oligopeptidase (POP) and were found to have modest potencies. Much better results were obtained when the quinoline nitrogen was methylated to provide adducts 199. The cationic center improved the inhibitory activity of these compounds (Fig. 23). 

Heteroaromatic cations undergo reduction when treated with 1,4-dihydronicotinamide. An early study showed that the 10-methylacridinium ion (87) was rapidly reduced in a redox reaction to the 9,10-dihydro adduct by 1,4-dihydronicotinamides (M Scheme 18). A variety of systems including py-ridines, isoquinolines, quinolines and phenanthridines have been studied using this and related procedures. The selective reduction of pyridinium and quinolinium salts with 1-benzyl-1,2-dihydro-isonicotinamide (89) has been achieved. The selective conversion to the thermodynamically more stable 1,4-dihydro species (90 Scheme 18) is rationalized by the reversibility in the formation of the kinetic products (i.e. the 1,2-adducts) in the presence of pyridinium ions. In the pyridinium case 1,6-di-hydro adducts were also observed in some cases. Reactivity in such systems is sometimes hindered due to hydration of the dihydropyridine system. This is particularly so in aqueous systems designed to replicate biological activity. Dihydroazines derived from isoquinolines and 3,5-disubstituted pyridines have been reported to overcome some of these difficulties. ... 

N-Substituted acetanilides (69), the original substrates studied by Vilsmeier (see Scheme 1), are highly reactive compounds for quinoline formation. Thus, quinolinium salts (70) derive from the action of phosgene,55 while 2-quino-lones (71) are readily formed by Vilsmeier formylation of the same sub-strates." b 7 The formylation of IV-phenylacetanilides (69 R1 = Ph) was initially misinterpreted,58 but has now been shown to be a highly efficient route to l-phenyl-2-quinolones.57... 

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