Alkylation Of Catechol Research Articles

Alkylation of catechol with cyclohexene. Novel sterically hindered o-quinones and catechols

A synthetic procedure for the preparation of sterically hindered catechols and o-quinones by the reaction of catechol with cyclohexene was developed. Novel cyclohexyl substituted catechols displayed remarkable stability during redox transformations and could be used as redoxactive ligands.

A Mild meta‐Selective C–H Alkylation of Catechol Mono‐Ethers

Catechol mono‐ethers are an important class of phenols. They are found in a number of pharmaceuticals, flavoring agents, perfumes, and are used for the preparation of numerous drugs. Herein, we report a mild meta‐selective C–H alkylation of these phenols, which is enabled by a cascade of oxidative dearomatization – radical addition – rearomatization process. The method is compatible with reactive functional groups on the parent arenol, such as olefins and halides. Primary, secondary, and teriary alkyl groups can be used, the source of which is most commonly an alkylborane. This process is operationally simple, does not require heating and generally proceeds in good yields.

Metal chlorides or sulfuric acid in ionic liquid solvents convert catechol to p-tert-Butylcatechol

A series of novel acidic ionic liquids (ILs) mediated in metal chloride or sulfuric acid (IL-RClx or IL-H2SO4, R=Na, K, Al, Ba, Ca) were investigated as catalysts in the alkylation of catechol and methyl tert-butyl ether to p-tert-Butylcatechol. Based on the ILs screening, it was found that N-(4-sulfonic acid butyl) pyridine hydrogen bisulfate (IL2) was the most efficient catalyst (in the reaction). Moreover IL2 modified by sulfuric acid showed the best performance with the yield of p-tert-Butylcatechol approximately 81.7% and the selectivity of 92.5%. For a clear perspective to the influence of H2SO4, IL2 ([C4SO3HPy]HSO4) was systematically studied by the Density Functional Theory at 6–31+G* level and the results showed that hydrogen bonds inside the ILs were probably the key for acidity enhancement of the modifications.

Alkylation of Catechol with Benzhydrol: Unusual Regioselectivity in the Synthesis of o‐Quinones and Catechols

AbstractUnusual regioselectivity occurs in the alkylation reaction of benzhydrol with catechol. The reaction proceeds to give catechols containing two vicinal diphenylmethyl substituents. 4,5‐Bis‐(diphenylmethyl)‐substituted catechol was found as the main product in more than 50 % yield. The reaction outcome is quite different to that of the reactions using bulky alkyl alcohols reported so far, in which 3,5‐ and 3,4,6‐disubstituted species were formed predominantly. The minor products this reaction are 3,5‐di‐ and 3,4,6‐trisubstituted species. Di‐ and trialkylated catechols were oxidized to give the corresponding o‐quinones. The reactivity and physicochemical properties of the new compounds were studied.

Study on Alkylation of Catechol with Ethanol by Al-P-Ti-O Oxides

Vapour-phase alkylation of catechol with ethanol has been investigated over Al-P-Ti-O oxides prepared by non-uniform precipitation method. The catalytic activities decrease with the increase of P content. The catalytic activities increase with increasing Ti content, while the selectivity to guathol decreases. The results of XRD characterization demonstrate that the increase of titanium and the addition of additive affects the structure of the catalysts. The addition of additive (cane sugar or citric acid) decrease the catalytic activities of the catalysts, while increase the stability of the catalyst. Both the conversion of catechol and the selectivity to guathol decrease by the addition of additive, and the C-alkylation products increase obviously. The results indicate that the appropriate pores and surface area are enough for the title reaction, lager pore and higher surface area are favorable to C-alkylation products and stability of catalyst.

Catalytic Synthesis of p-tert-Butylcatechol by Ionic Liquid

The alkylation of catechol with methyltertiarybutyl ether (MTBE) catalyzed by acid-functionalized ionic liquid gives p-tert-butylcatechol was investigated. The results indicated that under optimized reaction condition of 393K; 2h; n(catachol): n(MTBE): n (IL) =1:3:0.02, the conversion of catechol and the selectivity of p-tert-butyl catechol (4-TBC) were 87.4% and 65.3% respectively.

Alkylation of catechol with methanol to give guaiacol over sulphate-modified zirconia solid acid catalysts: The influence of structural modification of zirconia on catalytic performance

Sulphated zirconia catalysts were synthesized by wetness impregnation of Zr(OH)4 with (NH4)2SO4 solution. The samples were characterized by XRD, FTIR, BET and TPD (NH3 adsorption measurements). The catalysts were tested for the methylation of catechol in a fixed-bed reactor at 200 °C and 1 bar pressure. Calcination facilitated the transformation of ZrO2 from the tetragonal to monoclinic and addition of SO42- to Zr(OH)4 helped to retain the tetragonal phase through a surface complex phase. A direct correlation was observed between catechol activity and total acidity. The 5-wt% SO42-/ZrO2 catalyst showed the best conversion (∼80%) and selectivity for guaiacol (83%). Small addition of water in the feed improved the stability of the catalyst.

Cesium salt of a heteropolyacid in nanotubular channels and on the external surface of SBA-15 crystals: preparation and performance as acidic catalysts

The Cs-salt of heteropolyacid with stoichiometry Cs 2.5H 0.5PW 12O 40 (CsHPW) was deposited selectively at the external surface of the SBA-15 silica microcrystals, inside its mesoporous channels and simultaneously at both location modes. The structure, texture and performance of these CsHPW/SBA-15 composites were compared with that of a reference bulk salt of the same composition. Location of CsHPW salt on the external surface of SBA-15 microcrystals leads to disintegration of its agglomerates increasing acidity of the catalytic phase. A novel preparation strategy consisting of grafting the basic Cs-species at the internal pores surface of SBA-15 stabilized the CsHPW phase inside the channels in form of 5–8 nm nanocrystals at 30–70 wt.% loadings. The catalytic tests demonstrated that insertion of the CsHPW catalytic phase inside the nanotubular channels of SBA-15 in combination with location of an additional amount of this phase at the external surface of SBA-15 microcrystals allows to increase the specific activity of this phase in MTBE synthesis, propionylation of anisole and alkylation of catechol with t-butanol by a factor of 1.5–3. This level of specific activity in combination with high total loading of catalytic phase >60 wt.% permit to get composite catalytic materials with catalytic activity higher by a factor of 1.2–1.5 with respect to the bulk CsHPW catalyst and stabilizing the catalytic phase against colloidization in polar media.

Synthesis of polymeric crown ethers and thermoregulated ion complexation effects

AbstractThe alkylation of catechol with (chloromethyl)styrene–divinylbenzene copolymer 1 produces the polymer‐bound catechol 2, which upon reaction with a series of polyglycol dihalides affords macrocyclic polymeric benzo crown ethers 3, in fair yields. The alkylation of polybenzylamine 4 with polyglycol dihalides leads to diazapolymeric pseudocrown ethers 5. The degree of conversion of the catechol groups into macrocyclic ether groups and the residual concentration of diol groups were estimated from elemental analysis, weight‐gain data, and the analysis of bis‐2,4‐dinitrophenyl derivatives of the residual diol groups. The ion‐coordination patterns for the polymeric crowns were determined using distribution and column techniques. Equilibrium distribution values in methanol in the temperature range 20–60°C, for the perchlorate, thiocyanate, or bromide salts, have led to the following conclusions: (1) The spheric recognition patterns, typical of crown ethers in solution, are fully reproduced in the polymeric analogs. (2) The order of binding constants is K > Cs > Na > Li for polymeric benzocrown‐6 (3Hc) and benzocrown‐8 (3Hd) and K > Cs ≅ Na > Li for polymeric benzocrown‐4 (3Ha) and benzocrown‐5 (3Hb). (3) The polymers bind alkali metal cations by two mechanisms: the residual diol groups by ion exchange mechanism, and the crown groups by a salt‐coordination mechanism; the second mechanism is temperature‐dependent. Consequently, a thermal increase of 40°C causes a spontaneous elution, by “thermal shock,” and a three‐fold increase in the eluent of the original ion concentration. (4) Quantitative release of all the bound salt is observed.