Acetylation Of Anisole Research Articles

Catalytic Acetylation of Aromatics with Metal Chlorides and Solid Acids − a Comparative Study

<p>Evaluation of catalytic performances of selected metal chlorides such as AlCl<sub>3</sub>, SnCl<sub>4</sub>, ZnCl<sub>2</sub>, FeCl<sub>3</sub>, InCl<sub>3</sub> and GaCl<sub>3</sub> with solid acids such as sulfated zirconia, and zeolite beta was accomplished for acetylation of anisole, toluene and naphthalene. Presence of super acidity (Lewis or Bronsted acid) is found to be indispensable for activation of substrates towards acetylation reactions. In addition, presence of redox centers would further complement with the Lewis acid sites rendering catalytic stamina against deactivation. Strength of Lewis acid basically determines the activity of the metal chlorides towards acetylation. Among the Lewis acids investigated, FeCl<sub>3</sub>, InCl<sub>3</sub> and GaCl<sub>3</sub> exhibit their catalytic behaviour mostly through redox property as is evident from the conservation of Turn over number even after first cycle. Sulfated zirconia surpasses all the acid catalysts including metal chlorides and exhibits extended catalytic activity in acetylation of anisole. The pre-eminence of sulphated zirconia over other catalytic systems is owing to the synergistic effect of Lewis and Bronsted acidity.</p>

Chemical exploitation of metal contaminated biomass produced in phytoextraction

This article describes some aspects of the chemical recovery of the metal contaminated biomass produced in phytoextraction technologies. Taking advantage of the adaptive capacity of certain plants to hyperaccumulate metallic cations in their aerial parts, phytoextraction could be a sustainable way to remediate trace metals pollution. A possible exploitation of the metal contaminated biomass produced in phytoextraction is the direct use of metallic cations derived from plants as Lewis acid catalysts for organic chemistry. These original polymetallic systems serve as heterogeneous catalysts in chemical transformations enabling the synthesis of molecules with high added value. Results for Friedel-Crafts acylations and alkylations are presented in this paper: the acetylation of anisole and benzylation reactions are considered in more detail. The use of mine tailings as catalytic supports is also investigated: it could represent a new integrated outlet for tailings and phytoextraction products. Each step of the process is designed to minimise environmental impacts in accord with the principles of Green Chemistry. The process seeks to be an incentive for the economic development of phytoextraction. As phytoremediation gains momentum, it could also prove a concrete solution to the criticality of non-renewable mineral materials with new sources of zinc, nickel and other metals.

ACETYLATION OF ANISOLE IN GREEN CHEMISTRY CONDITIONS

In this study, acetylation of anisole by acetic anhydride, catalyzed by bismuth triflate are described. The reaction was taken place under new generation monomode microwave irradiation (Discover oven), solvent-free condition. High yield was obtainted in short time. Good selectivities for the para- products were observed. Bismuth(III) triflate could be recycled and reused effectively.

Silica functionalised sulphonic acid groups: synthesis, characterization and catalytic activity in acetalization and acetylation reactions

Abstract A simple synthesis procedure for the immobilization of propyl thiol groups on silica is investigated using various concentrations of 3-mercapto propyl trimethoxy silane (3-MPTS) in the range of 5–40%. The thiol group functionalised silicas (SiO2–SH) were then oxidized to Bronsted sulphonic acid silica materials (SiO2–SO3H) using aqueous H2O2 as oxidizing agent. The surface structures of the functionalized catalysts were analyzed by a series of characterization techniques like elemental analysis, FTIR, TG-DTA, Surface area measurements, XPS, 13 C CP MAS NMR and 29 Si MAS NMR. The 13 C CP MAS NMR analyses confirm that disulphide species are not formed under the present preparation condition of catalysts. The acidity of the synthesized catalysts were further confirmed by the temperature programmed desorption of ammonia. The catalytic activity of the sulphonic acid functionalized silicas was evaluated in the liquid phase acetalization of ethyl acetoacetate with ethylene glycol and in the acetylation of anisole with acetic anhydride. The catalysts were found to be active in the acetalization reaction, which needs mild acidic sites, while the acetylation reactions gave lower activity, probably it needs stronger acid sites. A 30 wt.% SO3H loaded silica (SiO2–SO3H30) was recycled two times in the acetalization of ethyl acetoacetate and no major change in the conversion of EAA and selectivity to fructone is seen, which further argue against the possibility of leaching of the anchored sulphur containing species during reactions.

Acetylation of anisole by acetic anhydride over a HBEA zeolite—Origin of deactivation of the catalyst

The liquid phase acetylation over a HBEA zeolite (Si/Al=10) of anisole with acetic anhydride in equimolar amounts was carried out in a batch reactor at 60°C. p-Methoxyacetophenone is selectively and rapidly formed on the fresh catalyst. However, a rapid deactivation occurs which could be attributed to a large extent to the pronounced inhibiting effect that p-methoxyacetophenone has on the acetylation. In a flow reactor and at a higher temperature (90°C), the catalyst deactivation is much slower particularly when an anisole rich mixture (anisole/acetic anhydride molar ratio of 5) is used as a reactant. Catalyst samples were recovered after various times on stream and the organic material which was retained in significant amounts on the zeolite was analysed by GC and GC/MS. The major part of this material, which consists of p-methoxyacetophenone, can be recovered by soxhlet extraction in methylene chloride. Due to its high polarity, this reaction product is strongly retained in the large mesopore volume of the HBEA zeolite. The minor part can only be recovered after dissolution of the zeolite in a hydrofluoric acid solution. It consists mainly of di- and triacetylated anisole entrapped in the zeolite micropores. As shown by nitrogen adsorption, these compounds cause pore blockage. The latter is responsible for part of the catalyst deactivation, the other part being due to p-methoxyacetophenone located in the mesopores. The use of an excess of anisole enhances catalyst stability as it limits both the retention of p-methoxyacetophenone and the formation of the polyacetylated anisoles.

Trifluoroacetic acid-catalysed transacylation of arenes by acylpentamethylbenzene

Facile transacylation between acylpentamethylbenzene and activated arenes such as anisole was found to occur in boiling trifluoroacetic acid (TFA). The mechanism for the transacylation between acetylpentamethylbenzene (AcPMB) and anisole with TFA was elucidated by means of product isolation and kinetics. The reaction proceeds via reversible protodeacetylation of AcPMB involving an ipso-protonated intermediate B to give pentamethylbenzene and acetic trifluoroacetic anhydride followed by irreversible acetylation of anisole by the mixed anhydride. The mechanism resulting in an ipso-protonated intermediate B was deduced from the reaction of acetylmesitylene with [2H]TFA as well as from the rate of deacetylation of 3,5-dideuterioacetylmesitylene with TFA. The formation of such an intermediate was also independently confirmed by 13C n.m.r. spectroscopic studies on AcPMB in superacid solutions under stable ion conditions.