A-Naphthol, III

To elucidate some enzymatic characteristics of the isolated laccases I, II, and III, substrate specificities for several simple phenols, electrophoresis patterns, ultraviolet spectra, electron spin resonance spectra, copper content, and immunological similarities were investigated. Tyrosine, tannic acid, g c acid, hydroquinone, catechol, pyrogallol, p-cresol, homocatechol, a-naphthol, -naphthol, p-phenylenediamine, and p-benzoquinone as substrates. No differences in the specificities of these substrates was found. The UV spectra for the laccases under stucfy are shown in Figure 4. Laccase III displays three adsorption bands (280, 405, and 600nm), laccase II shows one band 280nm), and laccase I shows two bands (280 and 405 nm). These data appear to indicate differences in chemical structure. The results of the copper content analysis (10) and two-dimensional electrophoresis also indicate that these fractions are completely different proteins (10), Therefore, we may expect differences in substrate specificities between the three laccase fractions for more lignin-like substrates, yet no difference for some simple phenolic substrates. 

Problem 19.30 (a) Give products, where formed, for reaction of PhN Cr with (i) a-naphthol, (ii) -naphthol, (iii) 4-methyl-l-naphthol, (iv) l-methyl-2-naphthol. (h) How can these products be used to make the corresponding aminonaphthols ... 

A Co(III)-Chelate [9], bis-2-(2-azopyridyl)-l-naphthol Co(III) has been interacted with polyacrylic acid and other polyelectrolytes (Fig. 5). 

Oxoniachrysenes 67 are simultaneously 2-benzopyrylium and 1-benzopyrylium salts, but maintain a distinct chemical behavior. 5-Oxoniachrysene salts 67 are interesting mainly as precursors of ben-zo[c]phenantridine derivatives 132, as mentioned in Section II,C,6. However, in contrast to 2-benzopyrylium salts (cf. Section III,C,4,a), compounds 67 react with nitrogen nucleophiles to form stable adducts 131 or products of anomalous ring-opening, namely a-naphthols 66 and esters 70 (77KGS1176). 

Similar to the reaction of 2-benzopyrylium salts with ammonia (Section III,C,4,a,i), an excess of competing nucleophiles in reactions with secondary amines is undesirable. Thus, the interactions of l-ethyl-3-methyl-substituted salt 183 with 40% aqueous solution of dimethylamine leads to a-naphthol 189 as the major product (79TH1). 

The formation of a-naphthols of type 189 from 1-alkyl-substituted salts 30, on heating with dimethylamine hydrochloride in ethanol, occurs by another mechanism and will be explained in Section III,C,4,b,i. The interaction of l-aryl-3-carboxy-substituted salts 62 with secondary amines in benzene is initiated probably as in the reaction of these salts with primary amines, and the attack by the secondary amine on position 3 is the primary step of this reaction. However, since protonation of the intermediate anion 190, a masked acyl anion, becomes difficult, an interaction of this anion with the carbonyl group of the benzophenone fragment occurs (86KGS125). The enamines 191 thus formed are usually hydrolyzed on purification, yielding five-membered cyclic acyloins 192. 

Contrary to the oxonium intermediate 115 (Section III,C,2), the intermediate 211 having the alkoxy leaving group readily opens its heterocyclic ring under these conditions. Diketones 205 (R3 is not H) thus formed are then cyclized into a-naphthols 204 (or /3-naphthols of type 209). If anhydro-bases 212 were formed, they would have to take part in the analogous conversions described previously. Obviously, the same mechanism may be applied to the scheme of formation of a-naphthols 204 from 2-benzopyrylium salts under the action of dimethylamine hydrochloride in ethanol (77KGS996) (cf. Section III,C,4,a,iv). 

Heating anhydrobases 212 without any external reagent at elevated temperature gives rise to a-naphthols 104 (86KGS276). Therefore, a real isomeric recyclization of 2-benzopyryIium salts (cf. Section III,C,4,a,ii) may occur and is carried out in two steps, with the last one requiring severe conditions. 

The cerium(IV) oxidation of lactyllactic acid49 and of 4-oxopentanoic acid50 in aqueous nitric acid solutions shows first-order dependence of the reaction on both cerium(IV) and substrate. A 1 1 complex formation between manganese(III) and amine, which later decomposes in the rate-limiting step, best explains the kinetics of oxidation of aliphatic amines by cerium(IV) in nitric acid medium in the presence of manganese(II).51 The kinetics of oxidation of naphthalene, 2-methyhiaphthalene, and a-naphthol with cerium(IV) in perchloric acid solutions have been studied.52 Use of a 50-fold molar excess of cerium(IV) perchlorate results in complete oxidation of fluorophenols to CO2, HCO2H, and HF in 48 h at 50 °C.53... 

Fig. 6. Acrylamide gel electrophoresis of glycoproteins separated by QAE-Sephadex column chromatography shown in Fig. 5. Strips of Whatman No. 3 filter paper, 1 mm X 1 cm, were dipped into 5% solutions of the glycoproteins and inserted into slots at the origin. The gel was stained for carbohydrate with a-naphthol and concentrated HjS04. The unlabeled fraction shows glycoproteins 1-5, which were chromatographed on the QAE-Sephadex column. Fraction III from Sephadex contained glycoprotein 3, fraction V contained glycoprotein 4, and fraction VII contained glycoprotein 5. From DeVries et al. (1970), reproduced with permission.

Reagents i, Brz-CHClj ii, NBS, hv, iii, EtOH-NaOH iv, a-naphthol sodium salt, phase-transfer conditions v, A... 

In 2006, Li and coworkers reported a Au-catalyzed aryl C(sp )-H functionalization of phenols and naphthols 3 with dienes toward the synthesis of benzofuran 4 (Scheme 12.2) [6]. This reaction proceeds via a Au(III)-catalyzed intermolecular addition of aryl C-H bond to dienes followed by the intramolecular addition of the phenol O-H bond to afford benzofuran 4. 

Gramstad, T. (1962) Hydrogen bonding. III. Intermolecular hydrogen bond association between nitrogen compounds and methanol, phenol, a-naphthol, and pentachlorophenol. Acta Chem. Scand., 16, 807-819. 

Bromo-2-pyridyla2o)-5-diethylamiQophenol (5-Br-PADAP) is a very sensitive reagent for certain metals and methods for cobalt have been developed (23). Nitroso-naphthol is an effective precipitant for cobalt(III) and is used in its gravimetric determination (24,25). Atomic absorption spectroscopy (26,27), x-ray fluorescence, polarography, and atomic emission spectroscopy are specific and sensitive methods for trace level cobalt analysis (see... 

Kobayashi et al. have reported the use of a chiral lanthanide(III) catalyst for the Diels-Alder reaction [51] (Scheme 1.63, Table 1.26). Catalyst 33 was prepared from bi-naphthol, lanthanide triflate, and ds-l,2,6-trimethylpiperidine (Scheme 1.62). When the chiral catalyst prepared from ytterbium triflate (Yb(OTf)3) and the lithium or sodium salt of binaphthol was used, less than 10% ee was obtained, so the amine exerts a great effect on the enantioselectivity. After extensive screening of amines, ds-1,2,6-... 

As previously described, a mixture of and J -octalins can be prepared by the reduction of naphthalene or Tetralin. Another route to this mixture is the dehydration of a mixture of 2-decalol isomers. This latter route has certain advantages in that one can avoid the handling of lithium metal and low-boiling amines. Moreover, 2-decalol is available commercially or can be prepared by the hydrogenation of 2-naphthol (5). In either case a comparable mixture of octalins is obtained, which can be purified by selective hydroboration to give the pure J -octalin (Chapter 4, Section III). 

Cobalt in steel Discussion. An alternative, but less sensitive, method utilises 2-nitroso-l-naphthol, and this can be used for the determination of cobalt in steel. The pink cobalt(III) complex is formed in a citrate medium at pH 2.5-5. Citrate serves as a buffer, prevents the precipitation of metallic hydroxides, and complexes iron(III) so that it does not form an extractable nitrosonaphtholate complex. The cobalt complex forms slowly (ca 30 minutes) and is extracted with chloroform. 

The specific detection of aromatic nitro compounds is a second example. These can be converted by reduction to primary amines, which are then diazotized and coupled to yield azo dyes (cf. reagent sequence Titanium(III) chloride — Bratton-Marshall reagent ). Sodium nitrite —naphthol reagent, diazotized sulfanilic acid and other reagents specific for amino groups (e.g. ninhydrin, fluorescamine, DOOB, NBD chloride [9]) can also be used in the second stage of the reaction (Fig. 21). 

In recent years, axially chiral binaphthalene derivatives have emerged as important ligands and chiraUty inducers in organic synthesis. Oxidative coupling of 2-naphthols represents a well estabhshed method for the preparation of binaphthols. The couplings are usually carried out by treating naphthols with more than an equimolar amount of a metal such as Fe(III), Mn(III),... 

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