Phenols C-alkylation

Experiments carried out by feeding TBPE only over H-MWW, showed that the O-alkylated product do not rearrange to C-alkylated phenol derivatives in our conditions, but it is hydrolysed to phenol. So, TBPE is not a reaction intermediate and perforce O-and C-alkylation are parallel reactions. Also o-TBP and p-TBP were fed each of them alone over our catalysts. As it could be observed in Fig. lb, o-TBP convert to p-TBP (by transalkylation) and in minor extent 2,4-DTBP (by disproportionation), while p-TBP (results not shown here) convert to 2,4-DTBP (by disproportionation). Because the transalkylation and disproportionation are bimolecular reactions and need large spaces, it is plausible to suppose that the alkylation could not take place in the pores, but on the external surface of H-MWW zeolites. 

And what about an alternative product There are two lines of thought, and the most obvious is that the reaction is repeated, since we are using a dibromide as substrate. Alternatively, we could consider one of the other resonance forms of the phenolate anion as nucleophile. This would generate a C-alkylated phenol. In the majority of cases, C-alkylation is not observed, in that the preferred resonance structure has charge on the electronegative oxygen. 

The palladium(0)-catalyzed asymmetric O-allylation of phenols has been described using five-, six- and seven-membered ring allylic carbonates and acyclic allylic carbonates (eq 9). The products from these reactions were subjected to a Claisen rearrangement to provide C-alkylated phenols. A study of various ligands for the reaction of phenol with 2-cyclohexenyl-l-methyl carbonate clearly showed that the Trost ligand is superior. ... 

The third family (c. in Figure 9.1) less widespread, derived from the alkylphenols, offers as with the succinimides several possibilities of modification to the ratio of hydrophilic and lipophilic groups. Mannich s reaction of the alkyl-phenols also provides additives for lubricating oils. 

The in situ process is simpler because it requires less material handling (35) however, this process has been used only for resole resins. When phenol is used, the reaction system is initially one-phase alkylated phenols and bisphenol A present special problems. As the reaction with formaldehyde progresses at 80—100°C, the resin becomes water-insoluble and phase separation takes place. Catalysts such as hexa produce an early phase separation, whereas NaOH-based resins retain water solubiUty to a higher molecular weight. If the reaction medium contains a protective coUoid at phase separation, a resin-in-water dispersion forms. Alternatively, the protective coUoid can be added later in the reaction sequence, in which case the reaction mass may temporarily be a water-in-resin dispersion. The protective coUoid serves to assist particle formation and stabUizes the final particles against coalescence. Some examples of protective coUoids are poly(vinyl alcohol), gum arabic, and hydroxyethjlceUulose. 

Laminates. Laminate manufacture involves the impregnation of a web with a Hquid phenoHc resin in a dip-coating operation. Solvent type, resin concentration, and viscosity determine the degree of fiber penetration. The treated web is dried in an oven and the resin cures, sometimes to the B-stage (semicured). Final resin content is between 30 and 70%. The dry sheet is cut and stacked, ready for lamination. In the curing step, multilayers of laminate are stacked or laid up in a press and cured at 150—175°C for several hours. The resins are generally low molecular weight resoles, which have been neutralized with the salt removed. Common carrier solvents for the varnish include acetone, alcohol, and toluene. Alkylated phenols such as cresols improve flexibiUty and moisture resistance in the fused products. 

Polyfluorinated a-diketones react with 1,2-diainino compounds, such as ortlio-phenylenediamine, to give 2,3-substituted quinoxalmes [103] Furthermore, the carboxyl function of trifluoropyruvates offers an additional electrophilic center. Cyclic products are obtained with binucleophiles [13, 104] With aliphatic or aromatic 1,2-diamines, six-memhered heterocycles are formed Anilines and phenols undergo C-alkylation with trifluoropyruvates in the ortho position followed by ring closure to form y-lactams and y-lactones [11, 13, 52, 53, 54] (equation 23). 

Sulfur cross-links have limited stability at elevated temperatures and can rearrange to form new cross-links. These results in poor permanent set and creep for vulcanizates when exposed for long periods of time at high temperatures. Resin cure systems provide C-C cross-links and heat stability. Alkyl phenol-formaldehyde derivatives are usually employed for tire bladder application. Typical vulcanization system is shown in Table 14.24. The properties are summarized in Tables 14.25 and 14.26. 

Sun, C. and Baird, M. (1998). The determination of alkyl phenol ethoxylates in wool-scouring effluent. Journal of the Textile Institute 89, 677-685. 

The solvent can also affect regioselectivity. Consider O- vs C-alkylation of phenoxide ion with allyl chloride or bromide. In water, with allyl chloride the O- to C-alkylation ratio is 49 41 with phenol as a solvent it is 22 78 with methanol, dimethylformamide, and dioxane 100% O-alkylation is achieved. The selective solvation of the more electronegative O by the more protic solvents perhaps leads to some C-alkylations. 

Mg/Me (Me=Al, Fe) mixed oxides prepared from hydrotalcite precursors were compared in the gas-phase m-cresol methylation in order to find out a relationship between catalytic activity and physico-chemical properties. It was found that the regio-selectivity in the methylation is considerably affected by the surface acid-basic properties of the catalysts. The co-existence of Lewis acid sites and basic sites leads to an enhancement of the selectivity to the product of ortho-C-alkylation with respect to the sole presence of basic sites. This derives from the combination of two effects, (i) The H+-abstraction properties of the basic site lead to the generation of the phenolate anion, (ii) The coordinative properties of Lewis acid sites, through their interaction with the aromatic ring, make the mesomeric effect less efficient, with predominance of the inductive effect of the -O species in directing the regio-selectivity of the C-methylation into the ortho position. 

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... 

A A liquid soluble in pentane 65 Mostly aliphatic material with some mono-aromatic parts broken off the coal by C-C cleavage. Apart from combined-phenol it has negligible polar material It contains some free paraffinic material, but exists mostly as alkyl phenols and alkyl-aryl ethers... 

The present work deals with the study of the liquid phase phenol alkylation by (-butanol over the three types of catalysts derived from MWW-precursor MCM-22, MCM-36 and ITQ-2. It was assumed that by pillaring and/or delamination the contribution of acid sites located on the hemicages will increase and it could be evidenced during the alkylation of phenol by (-butanol, process involving large reaction intermediates and products which are difficult to be accommodated within sinusoidal channels. The reaction pathway involves many parallel and/or successive steps, the main reactions being O-alkylation and C-alkylation. The catalytic activity and selectivity of these materials are discussed. A general scheme of the process is proposed on the basis of the structural and acidic features of the catalysts. 

Another problem with the reaction of phenols with aziridines is the selectivity between O-alkylation vs C-alkylation. A recent report has identified that the use of (ArO)3B selects for C-alkylation <06OL2627>. Most of the examples reported in this paper showed less than 5% of the O-alkylation product. What is interesting about this report is the stereochemistry of the product. While the mechanism is not known, the product is formally an SNl type product. Generally less than 5% was the product of inversion of configuration (the Sn2 product). In addition to the A-tosyl, both the A-Cbz and A-Dpp aziridines gave excellent yields of aziridine-opened product. 

Still another possibility in the base-catalyzed reactions of carbonyl compounds is alkylation or similar reaction at the oxygen atom. This is the predominant reaction of phenoxide ion, of course, but for enolates with less resonance stabilization it is exceptional and requires special conditions. Even phenolates react at carbon when the reagent is carbon dioxide, but this may be due merely to the instability of the alternative carbonic half ester. The association of enolate ions with a proton is evidently not very different from the association with metallic cations. Although the equilibrium mixture is about 92 % ketone, the sodium derivative of acetoacetic ester reacts with acetic acid in cold petroleum ether to give the enol. The Perkin ring closure reaction, which depends on C-alkylation, gives the alternative O-alkylation only when it is applied to the synthesis of a four membered ring ... 

Phenoxides undergo O-alkylation in solvents such as DMSO, DMF, ethers, and alcohols. In water and trifluoroethanol, however, extensive C-alkylation occurs.54 These latter solvents form particularly strong hydrogen bonds with the oxygen atom of the phenolate... 

GC of fraction 7 (Figure 5" I) has alkanes as small as The ratio of peak heights of pristane to C. increases in the uC of this fraction compared to previous fractions as expected from its shorter linear molecular size. The smaller peaks between n-alkane peaks are alkylated phenols and branched alkanes. 

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