Friedel-Crafts Type Benzylation Research Articles

GaAlCl -grafted Mont.K-10 clay: Highly active and stable solid catalyst for the Friedel-Crafts type benzylation and acylation reactions

A liquid phase reaction of anhydrous GaCl 3 and AlCl 3 with the surface hydroxyl groups (with HCl evolution) of Mont.K-10 clay in dry CCL 4 under reflux resulted in a novel GaAlCl x -grafted Mont.K-10 catalyst [with Cl/(Ga + Al) = 1]. The catalyst showed high activity and stability in the Freidel-Crafts type benzylation and benzoylation (by benzyl chloride and benzoyl chloride, respectively) of benzene, naphthalene and substituted benzenes, even in the presence of moisture. It also showed good activity for the benzoylation of nitrobenzene (i.e. even in the presence of strong electron withdrawing group, like nitro group, attached to the benzene ring). The catalytically active surface species in the catalyst are –(O) 2 –Ga(or Al)Cl.

Gold-Catalyzed Benzylation of Arenes and Heteroarenes.

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Gold-Catalyzed Benzylation of Arenes and Heteroarenes

Friedel–Crafts type benzylation of arenes and heteroarenes with benzylic acetates, alcohols, and carbonates is effectively promoted under mild reaction conditions using catalytic amounts of gold salts. The resulting 1,1-diarylalkanes and 1-aryl-1-heteroarylalkanes are obtained in high yields and with high selectivity. The utility of the method is demonstrated by a short synthesis of beclobrate {ethyl 2-[4-(4-chlorobenzyl)-phenoxy]-2-methylbutyrate (3)}, a fibric acid derivative.

Highly active and reusable catalyst from Fe-Mg-hydrotalcite anionic clay for Friedel-Crafts type benzylation reactions

Fe-Mg-hydrotalcite (Mg/Fe = 3) anionic clay with or without calcination (at 200–800‡C) has been used for the benzylation of toluene and other aromatic compounds by benzyl chloride. Hydrotalcite before and after its calcination was characterized for surface area, crystalline phases and basicity. Both the hydrotalcite, particularly after its use in the benzylation reaction, and the catalyst derived from it by its calcination at 200–800‡C show high catalytic activity for the benzylation of toluene and other aromatic compounds. The catalytically active species present in the catalyst in its most active form are the chlorides and oxides of iron on the catalyst surface.

In-Mg-hydrotalcite anionic clay as catalyst or catalyst precursor for Friedel–Crafts type benzylation reactions

In-Mg-hydrotalcite (Mg/In = 3) anionic clay with or without calcination (at 200–800 °C) or HCl pretreatment at different temperatures (26 and 80 °C) and periods (0.1 or 1.0 h) has been used for the benzylation of benzene and/or substituted benzenes by benzyl chloride. The hydrotalcite before and after its calcination or HCl pretreatment was characterized for its surface area, crystalline phases and basicity. The hydrotalcite particularly after its use in the benzylation reaction, and the catalyst derived from it by its calcination at 800 °C followed by HCl pretreatment (at 80 °C for 1.0 h), shows high catalytic activity even for the benzylation of benzene. The catalytically active species present in the catalyst in its most active form are the chlorides and oxides of indium on the catalyst surface.

Recent developments of heterogeneous solid catalysts for liquid-phase Friedel–Crafts type benzylation reaction

Liquid-phase Friedel–Crafts type benzylation of aromatics has been effected traditionally with catalysis by homogeneous protonic acid or Lewis acid. However, heterogeneous catalysts have the advantages, compared to their homogeneous counterparts, of facile recovering and recycling. This short article describes the recent advances in the liquid-phase Friedel–Crafts type benzylation by benzyl chloride of aromatics over redox metal: gallium (Ga), indium (In) and thallium (Tl) containing novel heterogeneous solid catalysts. Unlike conventional acidic catalyst, the benzylation activity of the Ga-, In- or Tl-based solids does not depend solely on their acidic properties, even present; these solids in their non-acidic or basic form also shows high benzylation activity. The catalytic activity order of Ga, In and Tl containing solid catalysts supported on chemically similar inert catalyst carrier is as follows: thallium/support > indium/support > gallium/support, which is quite similar to their redox potential values indicating the role of redox function in the benzylation process. A plausible reaction mechanism for the benzylation reaction over these catalysts is proposed. These heterogeneous solids are highly efficient for the Friedel–Crafts type benzylation, even in the presence of moisture, than the conventional strongly acidic solid acid catalysts.

Friedel–Crafts type benzylation and benzoylation of aromatic compounds over Hβ zeolite modified by oxides or chlorides of gallium and indium

Liquid phase benzylation (by benzyl chloride) and benzoylation (by benzoyl chloride) of benzene and other aromatic compounds over different Ga- and In-modified Hβ zeolite catalysts at 80 °C have been investigated. An impregnation of the zeolite by oxides or chlorides of Ga and In makes the zeolite highly active in the benzylation process but it results in a decrease in the acidity, particularly the strong acid sites (measured in terms of the ammonia chemisorbed at 250 °C) of the zeolite. Both the redox function, created due to the modification of the Hβ zeolite by Ga or In, and the zeolitic acidity seem to play important role in the benzylation or benzoylation process. Among the different Ga- and In-modified Hβ zeolite catalysts, the In 2O 3/Hβ showed highest activity for the benzene benzylation. This catalyst also showed high activity for both the benzylation and benzoylation of other aromatic compounds, even in the presence of moisture in the reaction mixture; in case of the benzoylation, the moisture has beneficial effect. The In 2O 3/Hβ catalyst can be reused in the benzylation for several times. Kinetics of benzene benzylation (using excess of benzene) over the different Ga- and In-modified Hβ zeolite catalysts has also been investigated. A plausible mechanism for the activation of both the reactants (aromatic substrate and benzyl or benzoyl chloride, forming corresponding carbocation) over the catalyst and also for the reaction between the carbocation and the activated and/or non-activated aromatic substrate is proposed.

AlCl x-grafted Si-MCM-41 prepared by reacting anhydrous AlCl 3 with terminal Si–OH groups: an active solid catalyst for benzylation and acylation reactions

A liquid phase reaction between anhydrous AlCl 3 and terminal Si–OH groups of mesoporous Si-MCM-41 in dry CCl 4 results in a AlCl x -grafted Si-MCM-41 (with Cl/Al ratio=1.43, Al (tetrahedral)/Al (octahedral)=ratio=0.84 and Al/Si ratio=0.17). This catalyst shows high catalytic activity in Friedel–Crafts type benzylation (by benzyl chloride) and acylation (by benzoyl chloride) of benzene and toluene.

Highly active, reusable and moisture insensitive catalyst obtained from basic Ga-Mg-hydrotalcite anionic clay for Friedel-Crafts type benzylation and acylation reactions

Liquid phase benzylation (by benzyl chloride) and acylation (by benzoyl chloride) of benzene and toluene over a Ga–Mg hydrotalcite (which is a basic anionic clay) with or without HCl gas pretreatment and also over the hydrotalcite used earlier in the toluene benzylation (at 110 °C) have been investigated. The fresh, used and HCl-gas-pretreated hydrotalcite catalysts were characterized for their surface area, basicity, crystalline structure and phases and also for their surface composition. The fresh hydrotalcite showed no catalytic activity for both the benzylation and benzoylation reactions for a long period. However, after a long induction period (2.7 h), the catalyst showed a very high activity in the toluene benzylation (at 110 °C). Whereas, the catalyst after its use in the toluene benzylation or after its HCl gas pretreatment showed very high activity for both the reactions with a much shorter induction period. The hydrotalcite-derived catalyst consists essentially highly dispersed gallium and magnesium chlorides on MgO. The presence of moisture in the reaction mixture has beneficial effects on the acylation reactions over the used catalyst.

Catalytic activity of iron sulfates for friedel-crafts type benzylation of toluene with benzyl chloride

Ferrous and ferric sulfates prepared by calcining their hydrates in air from 200 to 700 °C showed surprisingly high catalytic activity and selectivity for the title reaction. The activities observed at 45 and 53.5 °C showed the higher calcination temperature, the higher catalytic activity, and the shorter induction period. Ferrous sulfate heat treated at 500 °C in vacuo showed the maximum activity. The activation energies over FeSO 4, calcined at 400 and 600 °C were quite small, 2.7 and 5.1 kcal mol −1, respectively. The products were 42% ortho-, 6% meta-, and 51% para-benzyltoluene with an almost negligible amount of polymer in all the analyzed runs. The ratios of rates in toluene and benzene, k T k B , were 6.29 and 6.60 for FeSO 4 and Fe 2(SO 4) 3 calcined at 700 °C, respectively. From these values, the positional reactivities of toluene, o f , m f , and p f were obtained as 9, 1, and 20, respectively. Hammett's constant, ρ, was also estimated to be −4 ~ −5. From these observations, the high catalytic activity and selectivity were tentatively explained by a concept that the catalyst surface deformed by complicated interactions with sulfur remained slightly on the oxide upon the decomposition of sulfate salts, and adsorbed HCl acted catalytically as a push-pull to the reactant.

ChemInform Abstract: FRIEDEL‐CRAFTS BENZYLATION OF TOLUENE WITH BENZYL CHLORIDE CATALYZED BY METAL OXIDES

Metal oxides were found to catalyze significantly the Friedel-Crafts type benzylation of toluene with benzyl chloride with a selectivity similar to that occurring with metal sulfates.

Friedel-Crafts Benzylation of Toluene with Benzyl Chloride Catalyzed by Metal Oxides

Abstract Metal oxides were found to catalyze significantly the Friedel-Crafts type benzylation of toluene with benzyl chloride with a selectivity similar to that occurring with metal sulfates.