Quinolines basicity

Pyrazolo[3,4-Z)]pyridines, the 7-chloro-6-fluoro-2,4-dimethylquinoline and its mercapto-thiadiazolyl or oxadiazolyl quinolines 21 were prepared via Diels-Alder reaction conversion of methyl 2-(3-oxo-3-phenylpropenylamino)benzoate into 3-benzoyl-l.S -quinolin-4-one 22 . A mixture of aniline derivatives and malonic ester gave a variety of 3-aryl-4-hydroxyquinolin-2(l//)-ones 23. Condensation of isatins with ketones afforded quinoline-4-carboxylic acids. 2-Aryl-l,2,3,4-tetrahydro-4-quinolinones 22 and carbazolylquinolone were also prepared. The substitution of 2-chloroquinoline gave the 2-substituted quinolines. Basic alumina has catalyzed the C-C bond formation between 2-hydroxy-1,4-naphthoquinone and 2-chloroquinoline derivative to give 21. Reaction of organic halides with 8-hydroxyquinolines gave the respective ethers. The azodye derivatives of 21 were prepared in the absence of solvent. Silica gel catalyzed the formation of 2-ketomethylquinolines from reaction of 2-methylquinolines with acyl chlorides. 

On acetylation it gives acetanilide. Nitrated with some decomposition to a mixture of 2-and 4-nitroanilines. It is basic and gives water-soluble salts with mineral acids. Heating aniline sulphate at 190 C gives sulphanilic add. When heated with alkyl chlorides or aliphatic alcohols mono- and di-alkyl derivatives are obtained, e.g. dimethylaniline. Treatment with trichloroethylene gives phenylglycine. With glycerol and sulphuric acid (Skraup s reaction) quinoline is obtained, while quinaldine can be prepared by the reaction between aniline, paraldehyde and hydrochloric acid. 

Crude oils contain nitrogen compounds in the form of basic substances such as quinoline, isoquinoline, and pyridine, or neutral materials such as pyrrole, indole, and carbazole. 

The presence of certain substituents e.g., the amino group) may markedly affect the solubibty and other properties of the sulphonic acid or carboxylic acid. Thus such sulphonic acids as the aminobenzenesul-phonic acids, pyridine- and quinoline-sulphonic acids exist in the form of inner salts or zwitter-ions that result from the interaction of the basic amino group and the acidic sulphonic acid. Sulphanilic acid, for example, is more accurately represented by formula (I) than by formula (II) ... 

Because of these difficulties, special mechanisms were proposed for the 4-nitrations of 2,6-lutidine i-oxide and quinoline i-oxide, and for the nitration of the weakly basic anilines.However, recent remeasurements of the temperature coefficient of Hq, and use of the new values in the above calculations reconciles experimental and calculated activation parameters and so removes difficulties in the way of accepting the mechanisms of nitration as involving the very small equilibrium concentrations of the free bases. Despite this resolution of the difficulty some problems about these reactions do remain, especially when the very short life times of the molecules of unprotonated amines in nitration solutions are considered... 

The easier elimination of pyridine compared to quinoline-4 may be related to the pK value of 4-methylthiazole, which is between those of lepidine and 2-picoline (25. 55). This reaction explains also why a neutrodimethine cyanine is obtained with such good yields when reacting together a quaternary salt, ketomethylene, and o-ester in a basic medium. As the reaction proceeds, the trimethine cyanine is attacked by the ketomethylene. The resulting 2-methyl quaternary salt is transformed into trimethine cyanine, consuming the totality of the ketomethylene (1, p. 512 661). The mesosubstituted neutrodimethine cyanine is practically pure. 

As early as 1889 Walker (320), using samples of thiazole, 2,4-dimethylthiazoie, pyridine, and 2,6-dimethylpyridine obtained from Hantzsch s laboratory, measured the electrical conductivity of their chlorhydrates and compared them with those of salts of other weak bases, especially quinoline and 2-methylquinoline. He observed the following order of decreasing proton affinity (basicity) quinaldine>2,6-dimethyl-pyridine>quinoline>pyridine>2,4-dimethylthiazole> thiazole, and concluded that the replacement of a nuclear H-atom by a methyl group enhanced the basicity of the aza-aromatic substrates. 

Although only ppm levels of nitrogen are found in the mid-distillates, both neutral and basic nitrogen compounds have been isolated and identified in fractions boiling below 345°C (12). Pyrroles and indoles account for about two-thirds of the nitrogen. The remaining nitrogen is found in the basic pyridine and quinoline compounds. Most of these compounds are alkylated. 

The piC values of polymethine dyes depend on terminal group basicity (64) thus the protonation abHity diminishes if the basic properties of the residues decrease, passing from benzimidazole, quinoline, benzothiazole, to indolenine. On the other hand, the piC of higher homologues increases with chain lengthening. The rate constant of protonation is sensitive to other features, for example, substituents and rings in the chain and steric hindrance for short-chain dyes. 

Polymers. Quinoline and its derivatives may be added to or incorporated in polymers to introduce ion-exchange properties (see Ion exchange). For example, phenol—formaldehyde polymers have been treated with quinoline, quinaldine, or lepidine (81) (see Phenolic resins). Resins with variable basic exchange capacities have been prepared by treating Amherlites with 2-methylquinoline (82). 

Polymers containing 8-hydroxyquinoline appear to be selective adsorbents for tungsten in alkaline brines (95). In the presence of tartrate and citrate, quinaldic acid [93-10-7] allows the separation of zinc from gallium and indium (96). Either of these compounds can selectively separate lead and zinc from oxide ores as complexes (97). It is also possible to separate by extraction micro quantities of rhenium(VII), using quinoline in basic solution (98). The... 

Of the total tar bases in U.K. coke-oven and CVR tars, pyridine makes up about 2%, 2-methyl pyridine 1.5%, 3- and 4-methylpyridines about 2%, and ethylpyridine and dimethylpyridines 6%. Primary bases, anilines and methylanilines, account for about 2% of the bases in coke-oven and CVR tars and 3.5% of the bases in low temperature tars. The main basic components in coke-oven tars are quinoline (16—20% of the total), isoquinoline (4—5%), and methyl quinolines. These dicycHc bases are less prominent in CVR and low temperature tars, in which only a minority of the basic constituents have been identified. 

Phenols. Phenols are unreactive toward chloroformates at room temperature and at elevated temperatures the yields of carbonates are relatively poor (< 10%) in the absence of catalysis. Many catalysts have been claimed in the patent Hterature that lead to high yields of carbonates from phenol and chloroformates. The use of catalyst is even more essential in the reaction of phenols and aryl chloroformates. Among the catalysts claimed are amphoteric metals or thek haUdes (16), magnesium haUdes (17), magnesium or manganese (18), secondary or tertiary amines such as imidazole (19), pyridine, quinoline, picoline (20—22), heterocycHc basic compounds (23) and carbonamides, thiocarbonamides, phosphoroamides, and sulfonamides (24). 

Reactions involving quinoline hydrazide derivatives have been noted in the pyridazino-[4,3-c]- (64MI21500), -[4,5-f ]- (31M(58)238) and -[4,5-c]-quinoline (71CB3341) series, whilst the double cyclization of (358) to the pyridazino[4,5-f ]quinoline (359) (80CPB3457) and related cyclizations in the same series (80H(14)267) are of a basically similar type. A lone cyclization of this type from cinnoline intermediates involves the o-acetonylcarboxamide type formation of the pyridine ring to give the pyrido[3,4-c]cinnoline (360) (76JCS(Pl)592). 

Friedel-Crafts acylation, 2, 322 Quinoline, methyl-basicity, 2, 172 NMR, 2, 120 radical cations... 

Dried with Linde type 5A molecular sieves or Na2S04 and fractionally distd at reduced pressure. Alternatively, it was refluxed with, and distd from, BaO. Also purified by fractional crystn from the melt and distd from zinc dust. Converted to its phosphate (m 135°) or picrate (m 223°), which were purified by crystn and the free base recovered and distd. [Packer, Vaughn and Wong J Am Chem Soc 80 905 1958.] The procedure for purifying via the picrate comprises the addition of quinoline to picric acid dissolved in the minimum volume of 95% EtOH to yield yellow crystals which are washed with EtOH and air dried before recrystn from acetonitrile. The crystals are dissolved in dimethyl sulfoxide (previously dried over 4A molecular sieves) and passed through a basic alumina column, on which picric acid is adsorbed. The free base in the effluent is extracted with n-pentane and distd under vacuum. Traces of solvent are removed by vapour phase chromatography. [Mooman and Anton J Phys Chem 80 2243 1976.]... 

In one process the naphtha fraction boiling between 160 and 180°C is washed with caustic soda to remove the acids and then with suilphuric acid to remove basic constituents such as pyridine and quinoline. The naphtha is then frozen to remove naphthalene, and agitated with sulphuric acid, then with caustic soda and finally with water. Concentrated sulphuric acid is then run into the purified naphtha at a temperature below 0°C. The reaction is stopped by addition of water after 5-10 minutes, any sediment is removed, and the solution is neutralised and then washed with water. Residual naphtha is distilled off under vacuum, leaving behind the resin, which is run into trays for cooling. 

These substances differ structurally from niquidine (VI) by the substitution in the latter of a propylidene chain at C. Ainley and King having already found that d- and Z-dihydroquinicinols (VIII) which are y-substituted piperidine derivatives, were inactive, it appeared from these two sets of results that the strongly basic centre should not be separated by more than two carbon atoms frorn the point of attachment to the quinoline nucleus. King and Work therefore prepared a series of... 

The first condensation is conducted selectively on a variety of 3-ketoesters and a-formylesters. The first step works well on most simple anilines even when sterically congested and is mostly affected by basicity. Formation of intermediate 3 is problematic when strong electron-withdrawing groups (EWG) are attached to the aniline (e.g., nitro). The cyclization step is promoted thermally in inert solvents as well as using acidic solvents at elevated temperature. When there exists an opportunity to form isomers on cyclization (e.g., m-substituted anilines) a mixture of the 5- and 7-substituted quinolines usually results. 

Faced with the inapplicability of the standard basic conditions required for the Pfitzinger condensation in the context of their study, Lackey and Stembach developed a modified protocol which allows for the formation of quinolinic acids under acidic conditions. ... 

They report that in the reaction between 5-chlorisatin 19 and 5,6-dimethoxindanone 20 under basic conditions at reflux for 16 hours, the desired quinolinic acid 22 is obtained in 38% yield with an unavoidable competing amount of the aldol product 21. However, if the same reaction is carried out using aqueous acid conditions, the quinolinic acid is obtained in a reproducible 86% yield. ... 

Carboxylic acids with labile a-methylene protons react with isatin in the presence of strong aqueous base. In the total synthesis of methoxatin, the coenzyme of methanol dehydrogenase and glucose dehydrogenase, Weinreb employs a Pfitzinger condensation of an isatin 37 and pyruvic acid as a key step to provide the 4-quinolinic acid 38 in 50% yield under the standard basic conditions. ... 

One of the drawbacks of the Skraup/Doebner-von Miller reaction is the isolation of the desired product from the starting aniline and co-formed alkyl anilines and 1,2,3,4-tetrahydroquinaldine. Isolation can be simplified greatly by addition of one equivalent of zinc chloride at the end of the reaction all of the basic products were precipitated. Washing the brown solids with 2-propanol removed all impurities and left the desired quinoline as a 2 1 complex with zinc chloride in yields of 42-55%. 

Quinoline,like pyridine, and the ester give a 1 2 molar labile adduct (117) which is not basic and isomerizes on heating or with acids to a stable isomer (118) as in the pyridine series. It has been... 

Attempts have been made to deduce the structure of the predominant form of a potentially tautomeric compound from the shifts which occur in the ultraviolet spectrum of the compound in question on passing from neutral to basic or acidic solutions. The fact that no bathochromic shifts were observed for 2- and 4-hydroxy quinoline and 1-hydroxyisoquinoline under these conditions was taken as evidence that they existed in the oxo form [similar work on substituted quinol-4-ones led to no definite conclusions ]. A knowledge of the dissociation constants is essential to studies of this type, and the conclusions can, in any case, be only very tentative. A further dif-... 

The idea that dichlorocarbene is an intermediate in the basic hydrolysis of chloroform is now one hundred years old. It was first suggested by Geuther in 1862 to explain the formation of carbon monoxide, in addition to formate ions, in the reaction of chloroform (and similarly, bromoform) with alkali. At the end of the last century Nef interpreted several well-known reactions involving chloroform and a base in terms of the intermediate formation of dichlorocarbene. These reactions included the ring expansion of pyrroles to pyridines and of indoles to quinolines, as well as the Hofmann carbylamine test for primary amines and the Reimer-Tiemann formylation of phenols. 

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