Alkylation using supported aluminium chloride

Bound reagents are an excellent alternative in cases where the reagent is used in excess and can be difficult to remove. Purification is now a simple process of filtration and evaporation. For example, silica-supported aluminium chloride is a Lewis acid and an effective catalyst for Friedel-Crafts alkylations (Figure 3.15). 

The activity of the catalyst shown in Figure 4.10 in the alkylation of benzene with alkenes is comparable to that of aluminium chloride, but it shows improved selectivity towards monoalkylation compared to A1C13 itself and is readily recoverable and reusable (unlike A1C13, which needs to be removed from the reaction after one use, typically by a water quench). The alkylation of alkylbenzenes, and to a lesser extent halobenzenes, can also be carried out using supported aluminum chloride (Table 4.11). 

Different methods for the preparation of Novel Lewis-Acid Catalysts (NLACs) consisting of ionic liquids immobilised on mesoporous support materials are presented. The focus will be placed on materials bound to the carrier via the organic cation of the ionic liquid, either by grafting or by the preparation of organically modified HMS. After addition of aluminium(III)chloride the materials were used as catalysts e.g. in Friedel-Crafts alkylations, in which they displayed high activities and selectivities. 

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