Naphthol and derivs

The o/p-ratio is of primordial industrial importance for the synthesis of technical dyes, particularly for coupling components like 1-naphthol and derivatives of l-naphthpl-3-sulfonic acid. The dyes with an arylazo group in the 2-position form an intramolecular hydrogen bond (149) which is, of course, impossible for the 4-isomer. 

Biaryls. On treatment with TiCl4 in nitromethane, 2-naphthol and derivatives afford binaphthol derivatives. The oxidative coupling proceeds particularly well with substrates containing electron-donating groups. 

Kinetics of protolytic photoreactions in the vesicles was studied for naphthols in the vesicles. In aqueous solution 1-naphthol and derivatives are well known to dissociate in... 

Technologically, the most important examples of such couplers are 1-naphthylamine, 1-naphthol, and sulfonic acid derivatives of 1-naphthol (Fig. 2). Of great importance in the dyestuff industry are derivatives of l-naphthol-3-sulfonic acid, such as H-acid (8-amino-l-naphthol-3,6-disulfonic acid [90-20-0])... 

Some cyan dyes derived from both naphthols and phenols are reported to show thermochromism, a reversible shift in the dye hue as a function of temperature. This can occur in a negative while prints are being made (65). 

Hydroxy-2-naphthoic-2 -naphthylamide [136-64-8] M 305.3, m 243.5-244.5 , and other naphthol AS derivatives. Crystd from xylene [Schnopper, Broussard and La Forgia Anal Chem 31 1542 7959]. 

Mikami et al. have reported that the chiral titanium reagent 12 derived from bi-naphthol and TiCl2(0-i-Pr)2 catalyzes the Diels-Adder reaction of a-bromoacrolein or methacrolein with isoprene or 1-methoxy-l,3-butadiene to afford the cycloadducts with high enantioselectivity [18] (Scheme 1.25). 

Table 12-2. Rate constants (m-1 s-1) for azo coupling reactions of 1-naphthol and resorcinol, the corresponding anions, and some jnethoxy derivatives in water at 20 °C. Data from Kropacova et al., 1970 Kavalek et al., 1970 Sterba and Valter, 1972 Machackova et al., 1972a.

Hydroxyazo dyes fall into four main categories depending upon the nature of the coupling component used to make them, namely acyclics, phenols, heterocyclics, and naphthols. Those derived from naphthols comprise the largest and most important group commercially. 

The intermolecular reaction of phenols with propiolic esters occurs in the presence of a Pd(OAc)2 catalyst to afford coumarin derivatives directly.48,48a An exclusive formation of 5,6,7-trimethoxy-4-phenylcoumarin is observed in the Pd(OAc)2-catalyzed reaction of 3,4,5-trimethoxyphenol with ethyl phenylpropiolate in TFA (Equation (46)). Coumarin derivatives are obtained in high yields in the cases of electron-rich phenols, such as 3,4-methylenedioxyphenol, 3-methoxyphenol, 2-naphthol, and 3,5-dimethylphenol. A similar direct route to coumarin derivatives is accomplished by the reaction of phenols with propiolic acids (Equation (47)).49 A similar reaction proceeds in formic acid at room temperature for the synthesis of coumarins.50,50a Interestingly, Pd(0), rather than Pd(n), is involved in this reaction. 

This carboxylation reaction is of importance mainly for the manufacture from 2-naphthol of P-oxynaphthoic acid (BON) acid, the parent acid of sodium 3-hydroxy-2-naphthoate (4-35). The carboxylation is achieved by heating the sodium salt of 2-naphthol under pressure in an atmosphere of carbon dioxide (Scheme 4.25). Under these conditions an equilibrium mixture of the naphthol and its carboxylated derivative is established, the mixture containing about 30% of the carboxylic acid. The desired product is extracted from the reaction mixture and the unchanged 2-naphthol is recycled. 

The formation of the technically important 2 -hydroxy-3 -naphthoylanilines (Naphthol AS derivatives) is accomplished primarily by a condensation reaction between 2-hydroxy-3-naphthoic acid and an aromatic amine in the presence of phosphorus trichloride at 70 to 80°C. Appropriate reaction media are organic solvents, such as toluene or xylene. In stoichiometric terms, one mole of 2-hydroxy-3-naphthoic acid reacts with 0.4 to 0.5 moles of phosphorus trichloride. The solution is allowed to cool to room temperature, then neutralized with a sodium carbonate solution, and the Naphthol AS derivative is isolated by filtration. Mechanistically, the reaction is thought to proceed via the phosphoazo compound (11) ... 

Naphthol AS derivatives that have retained commercial importance are listed in Table 10, together with their name, constitution, and Colour Index number (Sec. 2.1.2, p. 195). 

The reaction sequence is the usual one. The hydrochloride of the aromatic amine is diazotized with sodium nitrite/hydrochloric acid and subsequently coupled onto a Naphthol AS derivative. 

Acetic acid or hydrochloric acid, possibly together with a tenside, reprecipitates the compound. This method affords the Naphthol AS derivative as a material with a very fine particle size, ready for coupling. A slightly acidic pH can be optimized and maintained by adding a sodium acetate buffer. 

Pigment synthesis follows the typical route to azo pigment lakes the aniline derivative or the aniline sulfonic acid is diazotized with sodium nitrite in an acidic medium (hydrochloric acid), followed by coupling on the Naphthol AS derivative, which is initially dissolved in an alkaline solution and then precipitated by adding inorganic or acetic acid. If a Naphthol AS sulfonic acid is used as a coupling component, it must be neutralized with alkali for dissolution and coupled directly. 

The coupling component 26 is prepared like a Naphthol AS derivative. 5-Ami-nobenzimidazolone is treated with 2-hydroxy-3-naphthoic acid chloride or with 2-hydroxy-3-naphthoic acid and phosphorus trichloride in an organic solvent (Sec. 2.1.2). 

What about jr-electron donor substituents on nitrosoarenes other than dimethylamino Pedley gives us the enthalpies of formation for three hydroxy derivatives the isomeric 4-nitroso-l-naphthol, 2-nitroso-l-naphthol and l-nitroso-2-naphthol, species 45-47 respectively. Of the three species, only the first cannot have an intramolecular hydrogen bond. By analogy to nitrophenols75 — there being no thermochemical data for the more related and hence relevant nitronaphthols—we expect that species 46 would be less stable than 45. After all, gaseous 2-nitrophenol is ca 20 kJ mol 1 less stable than its 4-isomer. We recall from the discussion of the isomeric naphthylamines that 1- and 2-naphthol are of almost identical stability. This suggests that species 46 and 47 should be of comparable stability. Both expectations are sorely violated by the literature results the enthalpies of formation of species 45, 46 and 47 increase in the order —20.3 4.9, —5.4 6.2 and 36.1 4.7 kJmol-1 respectively. If there is experimental error, where does the error lie ... 

Cychzation reactions have been realized by using 2-naphthol and various substituted aromatic and hetarylaldehydes in the presence of dry methanolic ammonia and napth-l,3-oxazine derivatives have been obtained [8-10]. 

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