2.6- Dimethylphenol, reaction with

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

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 ... 

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

Chemical/Physical. Under atmospheric conditions, the gas-phase reaction with OH radicals and nitrogen oxides resulted in the formation of p-tolualdehyde (Atkinson, 1990). Kanno et al. (1982) studied the aqueous reaction of p-xylene and other aromatic hydrocarbons (benzene, toluene, o-and /n-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). Products identified from the OH radical-initiated reaction of p-xylene in the presence of nitrogen dioxide were 3-hexene-2,5-dione, p-tolualdehyde, and 2,5-dimethylphenol (Bethel et al., 2000). 

Xylenol is an important starting material for insecticides, xylenol—formaldehyde resins, disinfectants, wood preservatives, and for synthesis of a-tocopherol (vitamin E) (258) and x//-CC-tocopherol acetate (USP 34-50/kg, October 1994). The Bayer insecticide Methiocarb is manufactured by reaction of 3,5-xylenol with methylsulfenyl chloride to yield 4-methylmercapto-3,5-xylenol, followed by reaction with methyl isocyanate (257). Disinfectants and preservatives are produced by chlorination to 4-chloro- and 2,4-dichloro-3,5-dimethylphenol (251). 

Fig. 2. Re-establishment of Hammett correlation for halogen-substituted phenols in the reaction with polyvinyl acetate radical. The straight line represents the Hammett equation found for 26 compounds (No. 12 in Table 3). Key o non-halogen substituted phenols including 2,6-dimethylphenols, excluding 2,6-t-Bu2-4-substituted-phenols halogen-substituted phenols.

Phenols are highly reactive toward the Friedel-Crafts alkylation reactions involving tertiary alkyl halides. Phenol, 2-methylphenol and 2,6-dimethylphenol react with tertiary alkyl halides such as 1-bromoadamantane in the absence of any external catalyst to give exclusively the para-(l-adamantyl)phenols (equation 1). These compounds have found... 

Photoelectron transfer oxidation of phenols, 3,5-dunethyl and 2,6-dunethylphenol, takes place using 2-nitrofluorene as the electron-accepting sensitizer in both acetonitrile and cyclohexane solution. In acetonitrile the anion radical of 2,6-dimethylphenol is observed as the final product . Other phenols such as the 2,4,6-trunethyl derivative also undergo electron transfer reactions with 1,1 -, 1,2 - and 2,2 -dinaphthyl ketones. Other sensitizers such as 1,4-dicyanonaphthalene with biphenyl as a co-sensitizer in acetonitrile have also been used. The resultant phenol radical cations (4a-h) have absorption maxima in the 410-460 nm region with the exception of 4i that absorbs at 580 nm. When the reactions are carried out in the presence of a trace of water, the radical cations are not observed. Instead, phenoxyl radicals are detected. This presumably is due to the reaction shown in equation 2. 

Mineral surfaces oxidize organics by sequential one-electron oxidation steps, such as that described for hydroquinone (reaction 10.80). Under certain reaction conditions, the single-electron oxidation products, which are radicals, may temporarily accumulate. These radicals are highly reactive, coupling among themselves to form dimers and polymers, or further oxidizing by reaction with dissolved O2. This may be the mechanism by which organics such as 2,6-dimethylphenol form dimers when adsorbed on air-dry smectites (Sawhney et al., 1984) ... 

In the case of 2,6-disubstituted phenols, the nature of the bismuth reagent, the nature of the alkyl substituents and the reaction conditions determined the outcome of the reactions. 2 Thus, in the reactions of 2,6-dimethylphenol (19) with pentaphenylbismuth (4) or with tetraphenylbismuthonium derivatives under basic conditions, ortho C-phenylation resulted in the formation of 6-phenylcyclo-hexadienone (20) in good yield. On the other hand, oxidative dimerisation took place in the reaction of 2,6-dimethylphenol with triphenylbismuth carbonate to afford the diphenoquinone (21) quantitatively 25... 

Reaction of a 2,6-dimethylphenol (4) with lead tetraacetate in the presence of an excess of acrylic acid leads to ortho-qainol acrylates (5) which then can lead to tricyclic lactones (6) by intramolecular Diels-Alder cyclisation. ... 

Phenol, the cresols, and the dimethylphenols are formed from the atmospheric degradation of benzene, toluene, and the xylenes, respectively, and data are available concerning the atmospheric reactions of these compounds. The potential atmospheric loss processes of phenolic compounds are reaction with N03, OH radicals, and 03, together with wet and dry deposition (these compounds are readily incorporated into rain- and cloud-water and fog). The OH radical reactions proceed by OH radical addition to the aromatic ring and by H-atom abstraction from the substituent -OH and -CH3 groups (Atkinson, 1989) ... 

Upon reaction with C-nucleophiles, such as phenol, 2,6-dimethylphenol, resorcinol, or A, A -dimethylaniline, in the presence of trifluoroacetic acid (TFA), 1,2,4-triazine 4-oxides 26 give rise to relatively stable C-5 adducts, for example,... 

Glycouril cyclic ethers 151 undergo a deprotection reaction with 3,5-dimethylphenol 152 in TFA (Equation 28). 

Phenols are reacted with aryllead(IV) tricarboxylates in the presence of pyridine to give, predominantly the ortho-, but also considerable amount of para-arylated products [66]. In this fashion, 4-methoxyphenyllead(IV) triacetate (484), upon reaction with 2,6-dimethylphenol (487), gave orf/io-arylated product 488 in 75-90% yield where no ara-arylation occured. Fully substituted phenol 458 bearing very bulky ort/zo-substituents furnished the /zara-arylated compound 489, as sole product in 30% yield, in both cases with the loss of aromaticity of phenolic ring [66], Scheme 34. Anilines can be arylated with aryllead(IV) tricarboxylates at nitrogen in the presence of copper(II) acetate under very mild conditions. However, the C-arylation has been effected upon previous treatment of unprotected aniline with ferf-butylmagnesium... 

Dimethylphenol, and 3-Hydroxyphenol Methanal Polymers Synthesized by Using a 3 -Methy Ipheno 1 3,5 -Dimethy Ipheno 1 3-Hydroxyphenol Ratio of 3 0.9 0.1 during Reaction with Methanal and Modified by Esterification with Acid Chlorides Selected from those Listed in Scheme 16 [147]. 

An important product from 3,5-dimethylphenol is the insecticide methiocarb (Bayer), which is manufactured by the reaction of 3,5-dimethylphenol with methylsulfenyl chloride to yield 4-methylmercapto-3,5-xylenol followed by reaction with methyl isocyanate. 

Sulfuric acid was initially thought to be the reagent to promote the Pechmann reaction to yield coumarins. However, it was subsequently found to provide in some cases good yields of the chromone. For example, reaction of chloro-dimethylphenol 31 with ethyl acetoacetate 6 with cone. H2SO4 gave a 35% yield of 32. ... 

The activation energy difference that we observed for the reaction with 2,4-dimethylphenol, and that with 2,6-dimethyIphenol, may be explained... 

Asymmetric Buchner reactions using chiral auxiliary have also been undertaken. The diazoketo substrate 126 for the chiral tethered Buchner reaction is prepared from optically pure (2/ ,4/f)-2,4-pentanediol in three steps the Mitsunobu reaction with 3,5-dimethylphenol, esterification with diketene, and diazo formation/deacetylation. Treatment of 126 with rhodium(II) acetate results in a quantitative yield of 127 with more than 99% ee. This compound is reduced with lithium aluminium hydride, and the resulting diol 128 undergoes epoxidation and concurrent acetal formation to give 129 as a single diastereomer. Hydrogenation of 129 with Raney nickel proceeds stereoselectively to yield saturated diol 130, which is converted to aldehyde 132 via acid hydrolysis followed by oxidation. Compound 132 is a versatile intermediate for natural product synthesis. 

The requisite enantiopure biphenol (5 )-BIPHEN-H2 can be purchased or it can be prepared in-house from 3,4-dimethylphenol by alkylation with isobutylene, followed by I<2Cr207-mediated oxidative coupling. The final resolution of diastere-omeric (-)-menthyl phosphates has been elaborated in 50 scale by Schrock and coworkers [51]. After reaction with PCI3, the produced phosphorchloridite was condensed with 2,2 -biphenol to produce (S.Si-Kelliphite. 

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