Dimethylphenol reactions

Dimethylphenol, photooxidation of 1017 2,6-Dimethylphenol, reactions with 1-bromoadamantane 606, 607 Dinaphthyl ketones, electron transfer reactions of 1019... 

Treatment of 3 5 dimethylphenol with dilute nitnc acid followed by steam distillation of the reaction mixture gave a compound A (CgH9N03 mp 66°C) in 36% yield The nonvolatile residue from the steam distillation gave a compound B (CsHpNOs mp 108°C) in 25% yield on extraction with chloroform Identify compounds A and B... 

Halogen Displacement. Poly(phenylene oxide)s can also be prepared from 4-halo-2,6-disubstituted phenols by displacement of the halogen to form the ether linkage (48). A trace of an oxidizing agent or free radical initiates the displacement reaction. With 4-bromo-2,6-dimethylphenol, the reaction can be represented as in equation 10 ... 

The most recent, and probably most elegant, process for the asymmetric synthesis of (+)-estrone appHes a tandem Claisen rearrangement and intramolecular ene-reaction (Eig. 23). StereochemicaHy pure (185) is synthesized from (2R)-l,2-0-isopropyhdene-3-butanone in an overall yield of 86% in four chemical steps. Heating a toluene solution of (185), enol ether (187), and 2,6-dimethylphenol to 180°C in a sealed tube for 60 h produces (190) in 76% yield after purification. Ozonolysis of (190) followed by base-catalyzed epimerization of the C8a-hydrogen to a C8P-hydrogen (again similar to conversion of (175) to (176)) produces (184) in 46% yield from (190). Aldehyde (184) was converted to 9,11-dehydroestrone methyl ether (177) as discussed above. The overall yield of 9,11-dehydroestrone methyl ether (177) was 17% in five steps from 6-methoxy-l-tetralone (186) and (185) (201). 

Polyphenylene oxide (PPO) is produced by the condensation of 2,6-dimethylphenol. The reaction occurs by passing oxygen in the phenol solution in presence of CU2CI2 and pyridine ... 

Katritzky et a/.511 have measured rate coefficients for deuteration of 3,5-dimethylphenol and heterocyclic analogues. As in all of the deuteration work of this group, rates of exchange were measured by the nmr method, which is useful for following exchanges at more than one position in the molecule but is, of course, much less accurate than detritiation techniques. In this study, the chemical shift for the ortho and para protons for the parent compound was too small to allow separate integration, but it was apparent that rates of exchange at these two positions did not differ by a factor > 4. From the rate-acidity profile (Table 149) reaction clearly occurs on the neutral species at pD < 3.5 (the log kl versus pD slope was 0.96) and upon the anion at pD > 3.5 (slope zero), and the reactivity of the anion to the neutral molecule was estimated as 107-8, close to the value of 107 noted above. 

TABLE 7.7 Percent Yield of Methylene and Ether Linkages of 2-Hydroxylmethyl-4,6-Dimethylphenol Self-reaction, 1 1 with 2,4-Xylenol, and 1 1 with 2,6-Xylenol... 

Hydroxymethyl-4,6-dimethylphenol, 406 Hydroxymethylphenol. See also Hydroxymethylated phenol reaction with melamine, 411 reaction with urea, 410 Hydroxymethyl substituents, condensation reactions of, 403... 

This reaction is similar to 13-1 and, like that one, generally requires activated substrates. With unactivated substrates, side reactions predominate, though aryl methyl ethers have been prepared from unactivated chlorides by treatment with MeO in HMPA. This reaction gives better yields than 13-1 and is used more often. A good solvent is liquid ammonia. The compound NaOMe reacted with o- and p-fluoronitrobenzenes 10 times faster in NH3 at — 70°C than in MeOH. Phase-transfer catalysis has also been used. The reaction of 4-iodotoluene and 3,4-dimethylphenol, in the presence of a copper catalyst and cesium carbonate, gave the diaryl ether (Ar—O—Ar ). Alcohols were coupled with aryl halides in the presence of palladium catalysts to give the Ar—O—R ether. Nickel catalysts have also been used. ... 

The literature on basic- and acid-catalyzed alkylation of phenol and of its derivatives is wide [1,2], since this class of reactions finds industrial application for the synthesis of several intermediates 2-methylphenol as a monomer for the synthesis of epoxy cresol novolac resin 2,5-dimethylphenol as an intermediate for the synthesis of antiseptics, dyes and antioxidants 2,6-dimethylphenol used for the manufacture of polyphenylenoxide resins, and 2,3,6-trimethylphenol as a starting material for the synthesis of vitamin E. The nature of the products obtained in phenol methylation is affected by the surface characteristics of the catalyst, since catalysts having acid features address the electrophilic substitution in the ortho and para positions with respect to the hydroxy group (steric effects in confined environments may however affect the ortho/para-C-alkylation ratio), while with basic catalysts the ortho positions become the... 

The catalytic activity of Mg/Al/O sample in m-cresol gas-phase methylation is summarized in Figure 1, where the conversion of m-cresol, and the selectivity to the products are reported as a function of the reaction temperature. Products were 3-methylanisole (3-MA, the product of O-methylation), 2,3-dimethylphenol and 2,5-dimethylphenol (2,3-DMP and 2,5-DMP, the products of ortho-C-methylation), 3,4-dimethylphenol (3,4-DMP, the product of para-C-methylation), and poly-C-methylated compounds. Other by-products which formed in minor amounts were dimethylanisoles, toluene, benzene and anisole (not reported in the Figure). 

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. 

Preparation of 3.5-dimethvl-4-hvdroxvbenzaldehvde. A mixture of 40.6g (0.33 mole) of 2-6-dimethylphenol and 46.2g (0.33 mole) of hexamethylene tetramine was covered with 500ml trifluoroacetic acid and the reaction mixture was refluxed overnight. After evaporation of the trifluoroacetic acid the residue was poured into 3L water and neutralized slowly with sodium carbonate. A brown oily solid was... 

Isaacson and Sawhney (60) studied the reactions of a number of phenols and smectite with transition metal (Cu, FeJ+) and nontransition metal exchangeable cations. IR spectra of the clay-phenol complexes showed that all the clays studied transformed the sorbed phenols. The transformation occurred to a much greater extent in clays with transition metal cations than in those with the non-transition metal cations. In a subsequent study, Sawhney et al. (61) studied the polymerization of 2,6-dimethylphenol on air-dried homoionic Na-, Ca-, A1-, and Fe-smectite at 50°C. A portion of the adsorbed 2,6-dimethylphenol was transformed into dimers, trimers, tetramers, and quinone-type compounds. The nature of the exchange cations had an effect on both sorption and transformation and decreased in the order Fe Al > Ca > Na. 

The study of the molecular weight of the intermediate course is an effective method for the classification of polymerization as chain or stepwise reaction. In Figure 3, the molecular weight of the obtained polymer is plotted against the yield, for the oxidative polymerization of dimethylphenol with the copper catalyst and for the electro-oxidative polymerization. The molecular weight rises sharply in the last stage of the reaction for the copper-catalyzed polymerization. This behavior is explained by a stepwise growth mechanism. 

The O-alkylation reactions of hindered phenols are normally sluggish reactions and attempts to improve reactivity have received considerable attention from synthetic organic chemists. Ultrasonic irradiation has been used to greatly enhance the rate of alkylation of 2,6-dimethylphenol with several different primary halides under heterogeneous conditions using KjCOj in N-methylpyrrolidinone (NMP) (Eq. 3.26) [126]. 

Chemical/Physical. Under atmospheric conditions, the gas-phase reaction of o-xylene with OH radicals and nitrogen oxides resulted in the formation of o-tolualdehyde, o-methylbenzyl nitrate, nitro-o-xylenes, 2,3-and 3,4-dimethylphenol (Atkinson, 1990). Kanno et al. (1982) studied the aqueous reaction of o-xylene and other aromatic hydrocarbons (benzene, toluene, w and p-xylene, and naphthalene) with hypochlorous acid in the presence of ammonium ion. They reported that the aromatic ring was not chlorinated as expected but was cleaved by chloramine forming cyanogen chloride. The amount of cyanogen chloride formed increased at lower pHs (Kanno et al., 1982). In the gas phase, o-xylene reacted with nitrate radicals in purified air forming the following products 5-nitro-2-methyltoluene and 6-nitro-2-methyltoluene, o-methylbenzaldehyde, and an aryl nitrate (Chiodini et ah, 1993). 

The phenol, the cresol isomers, and the dimethylphenols, major pyrolysis products in e Moscow wood sample, are probably also derived frt>m lignin precursors that have been altered through coalification reactions. Hatcher [fr] have shown that an increase is observed in the relative proportion of phenols and cresols as rank of coaHfred wood samples increases to subbituminous coal. Comparing the distribution of pyrolysis products from the Moscow wood to that of other coalified wood samples of Hatcher allows us to deduce that the... 

OxymetazoUne Oxymetazoline, 6-fert-butyl-3 (2-imidazolin-2-ilmethyl)-2,4-dimethylphe-nol (11.1.39), is synthesized by chloromethylation of 6-tert-butyT2,4-dimethylphenol and the further transformation of the resulting chloromethyl derivative (11.1.37) into a nitrile (11.1.38). The reaction of this with ethylendiamine gives oxymetazoline (11.1.39) [41,42]. 

The arylamine 780b required for the total synthesis of carbazomycin B (261) was obtained by catalytic hydrogenation, using 10% palladium on activated carbon, of the nitroaryl derivative 784 which was obtained in six steps and 33% overall yield starting from 2,3-dimethylphenol 781 (see Scheme 5.85). Electrophilic substitution of the arylamine 780b with the iron-complex salt 602 provided the iron complex 787 in quantitative yield. The direct, one-pot transformation of the iron complex 787 to carbazomycin B 261 by an iron-mediated arylamine cyclization was unsuccessful, probably because the unprotected hydroxyarylamine moiety is too sensitive towards the oxidizing reaction conditions. However, the corresponding 0-acetyl derivative... 

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