Naphthol alkylation

Phenol Ethers. The phenol ethers are prepared similarly to the aliphatic ethers. An alkyl halide, a sodium alkyl sulfate, dialkyl sulfate, or alkyl toluenesulfonate is treated with a phenol in an alkaline medium (sodium ethylate) or in the presence of metal halides (cf. Anisole, Acetophenetidine, and vanillin). Naphthols alkylated more easily than phenols, heating of naphthol with methanol in the presence of sulfuric acid or alumina being sufficient to give satisfactory yields. 

Alkyl and aryl-alkyl halides form 2-naphthyl ethers with 2-naphthol. 

Picrates of p-naphthyl alkyl ethers. Alkyl halides react with the sodium or potassium derivative of p-naphthol in alcoholic solution to yield the corresponding alkyl p-naphthyl ethers (which are usually low m.p. solids) and the latter are converted by alcoholic picric acid into the crystalline picrates ... 

Mix together 1 0 g. of pure p-naphthol and the theoretical quantity of 50 per cent, potassium hydroxide solution, add 0-5 g. of the halide, followed by sufficient rectified spirit to produce a clear solution. For alkyl chlorides, the addition of a little potassium iodide is recommended. Heat the mixture under reflux for 15 minutes, and dissolve any potassium halide by the addition of a few drops of water. The p-naphthyl ether usually crystallises out on cooling if it does not, dilute the solution with 10 per cent, sodium hydroxide solution untU precipitation occurs. Dissolve the p-naphthyl ether in the minimum volume of hot alcohol and add the calculated quantity of picric acid dissolved in hot alcohol. The picrate separates out on cooling. Recrystallise it from rectified spirit. 

They are usually poisonous and can be identified by using them to alkylate naphthol (compare Section IV,104). 

Dienes can also be used ia Friedel-Crafts cyclo alkylations. For example, treatment of phenol with 2,5-dimethyl-2,4 hexadiene gives 5,5,8,8-tetramethyl,6,7-dihydro-2-naphthol. 

Isopropylnaphthalenes can be prepared readily by the catalytic alkylation of naphthalene with propjiene. 2-lsopropylnaphthalene [2027-17-0] is an important intermediate used in the manufacture of 2-naphthol (see Naphthalenederivatives). The alkylation of naphthalene with propjiene, preferably in an inert solvent at 40—100°C with an aluminum chloride, hydrogen fluoride, or boron trifluoride—phosphoric acid catalyst, gives 90—95% wt % 2-isopropylnaphthalene however, a considerable amount of polyalkylate also is produced. Preferably, the propylation of naphthalene is carried out in the vapor phase in a continuous manner, over a phosphoric acid on kieselguhr catalyst under pressure at ca 220—250°C. The alkylate, which is low in di- and polyisopropylnaphthalenes, then is isomerized by recycling over the same catalyst at 240°C or by using aluminum chloride catalyst at 80°C. After distillation, a product containing >90 wt % 2-isopropylnaphthalene is obtained (47). 

Naphthol is mainly used in the manufacture of the insecticide carbaryl (59), l-naphthyl A/-methyicarbamate/ iJ-2j5 - (Sevin) (22), which is produced by the reaction of 1-naphthol with methyl isocyanate. Methyl isocyanate is usually prepared by treating methylamine with phosgene. Methyl isocyanate is a very toxic Hquid, boiling at 38°C, and should not be stored for long periods of time (Bhopal accident, India). India has developed a process for the preparation of aryl esters of A/-alkyl carbamic acids. Thus l-naphthyl methylcarbamate is prepared by refluxing 1-naphthol with ethyl methylcarbamate and POCl in toluene (60). In 1992, carbaryl production totaled > 11.4 x 10 t(35). Rhc ne-Poulenc, at its Institute, W. Va., facihty is the only carbaryl producer in United States. 

Naphthalenol also is used ia the preparation of azo, iadigoid, and nitro, eg, 2,4-dinitro-l-naphthol, dyes, and ia making dye iatermediates, eg, naphtholsulfonic acids, 4-chloro-1-naphthalenol, and l-hydroxy-2-naphthoic acid. 1-Naphthalenol is an antioxidant for gasoline, and some of its alkylated derivatives are stabilizers for plastics and mbber (68). 

The azo coupling reaction proceeds by the electrophilic aromatic substitution mechanism. In the case of 4-chlorobenzenediazonium compound with l-naphthol-4-sulfonic acid [84-87-7] the reaction is not base-catalyzed, but that with l-naphthol-3-sulfonic acid and 2-naphthol-8-sulfonic acid [92-40-0] is moderately and strongly base-catalyzed, respectively. The different rates of reaction agree with kinetic studies of hydrogen isotope effects in coupling components. The magnitude of the isotope effect increases with increased steric hindrance at the coupler reaction site. The addition of bases, even if pH is not changed, can affect the reaction rate. In polar aprotic media, reaction rate is different with alkyl-ammonium ions. Cationic, anionic, and nonionic surfactants can also influence the reaction rate (27). 

O- Alkylation is comparable to A/-alkylation, but since the sodium salts are water-soluble it is most convenient to treat the phenol or naphthol in aqueous caustic solution with dimethyl sulfate or diethyl sulfate. These are comparatively expensive reagents, and therefore, alkoxy groups are introduced at a prior stage by a nucleophilic displacement reaction whenever possible. 

In a related reaction, a number of aryloic compounds, behaving as ketonic moieties in the Fischer indolisation, have been shown to afford carbazoles in the Japp-Maitland condensation. For example, when either I-naphthol, 2-naphthol, 6-alkyl-2-naphthol, ... 

With secondary and tertiary alkyl halides an Ea-elimination is often observed as a side-reaction. As the alkyl halide reactant an iodide is most often employed, since alkyl iodides are more reactive than the corresponding bromides or chlorides. With phenoxides as nucleophiles a C-alkylation can take place as a competing reaction. The ratio of 0-alkylation versus C-alkylation strongly depends on the solvent used. For example reaction of benzylbromide 4 with /3-naphth-oxide 5 in yV,A-dimethylformamide (DMF) as solvent yields almost exclusively the /3-naphthyl benzylether 6, while the reaction in water as solvent leads via intermediate 7 to formation of the C-benzylated product—l-benzyl-2-naphthol 8—as the major product ... 

Indole and 2-naphthol undergo alkylation on the nitrogen and oxygen atoms, respectively (Scheme 5.1-22), when treated with an alkyl halide and base (usually NaOH or KOH) in [BMIM][PF6] [51]. 

The transformation of arenes in the troposphere has been discussed in detail (Arey 1998). Their destruction can be mediated by reaction with hydroxyl radicals, and from naphthalene a wide range of compounds is produced, including 1- and 2-naphthols, 2-formylcinnamaldehyde, phthalic anhydride, and with less certainty 1,4-naphthoquinone and 2,3-epoxynaphthoquinone. Both 1- and 2-nitronaphthalene were formed through the intervention of NO2 (Bunce et al. 1997). Attention has also been directed to the composition of secondary organic aerosols from the photooxidation of monocyclic aromatic hydrocarbons in the presence of NO (Eorstner et al. 1997) the main products from a range of alkylated aromatics were 2,5-furandione and the 3-methyl and 3-ethyl congeners. 

Dehmlow and Klauck (1994) have shown how O- vs C-alkylations of 2-naphtholate, with benzyl bromide in toluene, in solid-liquid mode can be influenced by the PT catalyst (benzyltriethylammonium chloride) concentration. The ratio of O- to C-alkylated product could be varied from 0.02 to 7.5 depending on the catalyst concentration, temperature, etc. 

Tab. 3.17 C-alkylation of/J-naphthol in the presence of lithiated base under so Ivent-free conditions.

Bhat et al. [199] used complexation with the bis(ethylenediamine) copper (II) cation as the basis of a method for estimating anionic surfactants in fresh estuarine and seawater samples. The complex is extracted into chloroform, and copper is measured spectrophotometrically in the extract using l,2(pyridyl azo)-2-naphthol. Using the same extraction system these workers were able to improve the detection limit of the method to 5 pg/1 (as linear alkyl sulfonic acid) in fresh estuarine and seawater samples. 

As the reaction temperature increases, the equilibrium constant diminishes, since complex formation is accompanied by heat liberation. Sterically hindered phenols form loose complexes because of the impeding effect of voluminous alkyl substituents in the ortho-position. Hydrogen bonding reduces the activity of phenols, which was first observed in the studies of the effects of cyclohexanol and butanol on the inhibitory activity of a-naphthol in cyclohexane [9]. This phenomenon was investigated in detail with reference to the oxidation of methylethylketone [10]. The k7 values for some inhibitors of the oxidation of ethylbenzene and methylethylketone are given below (333 K) [10,46] ... 

Morken and co-worker (57) recently reported using a visual colorimetric assay to evaluate a variety of catalyst systems for allylic alkylation. This method uses the reaction of naphthol with Fast Red diazonium salt as a method for determination of catalyst activity. Reaction of the naphthyl allyl carbonate (222) with palladium gives the naphthoxide (223) after loss of C02. The naphthoxide then deprotonates... 

Early studies of the affinity of acid dyes for wool revealed noteworthy correlations with dye structure. For example, in four pairs of monoazo dyes differing only by replacement of a benzene by a naphthalene nucleus, the affinity increase in each pair was consistently within the range -4-6 to -6.3 kj/mol. In three related pairs of dyes, an additional sulpho group reduced the affinity by about -4 kj/mol. In a series of alkylsulphuric acids (ethyl, octyl, dodecyl) and in two series of monoazo dyes containing alkyl chains of increasing length, the increment per methylene group was consistently about -1.66 kj/mol. A close correlation between affinity and Mr was also obtained for a series of substituted phenylazo-l-naphthol-4- sulphonic acid dyes [115]. 

The increase in affinity for wool imparted to acid dye structures by the inclusion of long-chain alkyl groups has a noteworthy effect on wet fastness. Thus the incorporation of such a group into the levelling acid dye Cl Acid Red 1 (3.129 R = H) to form the super-milling acid dye Red 138 (3.129 R = n-dodecyl) raises the fastness to washing at 50 °C (effect on pattern) from 2-3 to 4-5. Similar effects for a series of alkylated phenylazo-2-naphthol-6-sulphonate dyes are recorded in Table 3.41. 

These unexacting requirements make the simplest unsulphonated azo structures, often monoazo types, quite acceptable [80]. Typical of the least polar members of this class are Cl Solvent Yellow 2 (4-68), Cl Solvent Orange 1 (4.69) and Cl Solvent Red 17 (4.70). Simple azo structures carrying sulphonamide, sulphone or carboxylate ester groups are used where a somewhat more polar, less soluble dye is needed. Simple disazo compounds (4-amino-azobenzene— 2-naphthol, for example) are used as red solvent dyes. Probably the only structural feature worthy of note in this class is the occasional adoption of structures carrying long alkyl chains to enhance solubility, as in the case of the disazo dye Cl Solvent Yellow 107 (4.71). 

The three-component synthesis of benzo and naphthofuran-2(3H)-ones from the corresponding aromatic alcohol (phenols or naphthols) with aldehydes and CO (5 bar) can be performed under palladium catalysis (Scheme 16) [59,60]. The mechanism involves consecutive Friedel-Crafts-type aromatic alkylation and carbonylation of an intermediate benzylpalla-dium species. The presence of acidic cocatalysts such as TFA and electron-donating substituents in ortho-position (no reaction with benzyl alcohol ) proved beneficial for both reaction steps. 

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