Naphthol 2,3-£ quinolines

Electrolyte-sulphuric acid (5% wt.%) plus an inhibitor (0-5kgm ) such as diorthotolyl thiourea, quinoline ethiodide or /3-naphthol quinoline. The temperature should be 75°C, the cathode current density 2000 Am and the time of cathodic polarisation 3 min. The anode should be carbon or lead. If lead anodes are used, lead may deposit on the specimens and cause an error in the weight loss. If the specimen is resistant to nitric acid the lead may be removed by a flash dip in 1 1 nitric acid. Except for this possible source of error, lead is preferred as an anode, as it gives more efficient corrosion product removal. 

Commonly used aromatic frothers are phenols, cresols, pyridines. These are mixtures of various methylphenols, naphthols, quinolines, anilines, naphthalene, amines, etc. extracted from coal tars. These frothers have been widely used in the flotation of coal. Apart from the frothability, these reagents have certain ability as collector especially with the increase in their molecular size. 

Noteworthy among the yellow lakes are those of yellow wood, quercitron, Persian berries, naphthol yellow, auramine, thioflavine, chrysoidine, quinoline yellow, met anil yellow and its analogues. 

A route involving 1,4-dihydroxybenzene intermediates has been suggested for the oxidation of several naphthols and naphthylamines, and also hydroxy- and amino-quinolines and isoquinolines. 

Coal-tar creosote is a mixture of aromatic hydrocarbons containing appreciable amounts of tar acids and bases (up to about 5% of each), and has a boiling range between 200 and 355°C. The important hydrocarbons present include fluorene, anthracene, phenan-threne, and some naphthalene. The tar acids are mainly phenols, creosols, xylenols, and naphthols the tar bases consist of pyridines, quinolines, and acridines. 

Substituents directly attached to fused benzene rings or aryl groups mostly show the reactions of those on benzenoid rings. Thus, a substituent on the benzenoid ring in quinoline or isoquinoline should be compared with that on a naphthalene rather than with a benzene nucleus for example, such hydroxy derivatives undergo the Bucherer reaction, ArOH + (NH4)2S03 ArNH2, typical for naphthols (see also Section 3.2.3.2.2). 

NOTE For ligand identity, see references. Abbreviations used in descriptions of coordination sphere py, pyridine im, imine qu, 8-quinolinate imid, imidazolate pz, pyrazole amm, ammine am, amidate nap, naphtholate phe, phenolate cat, catecholate aq, aquo. 

All these substrates behave very similarly to phenols, as the hydroxy group u.sually drives the reaction toward the ortho position. When two unequivalent ortho positions are present, the preferred reaction site is at the C atom vicinal to N (A attack), unless the substrate has a fused ring. structure. - - In this latter case, as in quinoline derivatives, for example, the prevailing attack is of type B (89), similar to that observed in the case of naphthols. 

A number of cases are known of ring contraction of tropolones to phenols, with extrusion of the carbonyl group as carboxylate or carbon dioxide. Examples are the conversions of the benzotropolone (216) to the naphthol ester (217 73%) with methanolic potash the pyridinotropolone (218) to the quinoline (219 50%) in dilute alkali the aminotropolone (220) to the methylsalicyclic acid (221 82%) on diazotization and the tropolonecarboxylate (222) to the dicarboxylic acid (223 78%) on brief alkali fu-... 

According to their chemical structures and the Cl system, dyes can be classified into 17 groups nitro dyes, triphenylmethane derivatives, xanthenes, acridine derivatives, quinoline derivatives, azines, ant-hraquinones, indigoid dyes, phthalocyanines dyes, oxydation bases, insoluble azo dye precursors, and azo dyes (classes XII-XVII). In practice, dyes are classified into different application classes disperse, acid, basic, direct, vat, fiber-reactive, sulfur, preme-tallic, solvent dyes, and naphthols. 

Many aromatic systems have been oxidized by Fremy s salt, including phenols, naphthols, anilines, quinolines, indoles, carbazoles, and polyaromatic systems. The review articles by Zimmer and Parker can be consulted for specific examples. Slight modifications of the mechanism presented in Scheme 20 explain the oxidation of most of these classes of compounds [63], Oxidations by Fremy s salt and related nitroxides have been used in the total synthesis of several biologically active compounds [64], Recent examples can be found in the syntheses of the antitumor antibiotic streptonigrone (34), the antitumor agent EO-9 (35), the anti-rheumatic agent epoxyquinomicin B (36), and the antineoplastic agent makaluvamine C (37) (Scheme 21) [65]. 

Quinolinols and isoquinolinols in which the oxygen is at any position other than 2-and 4- for quinolines and 1- and 3- for isoquinolines are true phenols i.e. have an hydroxyl group, though they exist in equilibrium with variable concentrations of zwitterionic structures with the nitrogen protonated and the oxygen deprotonated. They show the typical reactivity of naphthols. 8-Quinolinol has long been used in... 

A solution of 5.91 g 4,6-dibromo-2-nitroaniline in 15 mL quinoline was diazotized with a mixture of 3 g NaN02 in 40 mL cone. H2SO4 and 15 mL water. Coupling took place when to the clear diazonium salt solution was added a solution of 2.88 g )0-naphthol in 10 mL quinoline. The coupled product was filtered, washed, and digested with 25% alcohol. The yield was quantitative. Recrystallization of the 4,6-dibromo-2-nitrobenzene-azo-)0-naphthol from toluene gave red crystals, m.p., 250°C. 

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