Friedel Crafts reaction using bismuth salts

The Friedel-Crafts reaction was discovered at the end of the nineteenth century, and despite intensive studies a general solution to this initial drawback has not been found.3 Studies have been carried out to find mild Lewis acids forming less stable complexes with the ketone and still able to catalyze the reaction. Some successes have been obtained using rare earth triflate4 or bismuth HI salts.5 These methods, if they proved to be catalytic, still require significant quantities of catalysts (a few percent) and the recycling of the catalyst is not simple. 

Water-stable ionic liquids were later used for Friedel-Crafts acylations, using a metal triflate catalyst. Cu(0Tf)2 proved to be the most efficient catalyst for this transformation, and acylation of anisole by benzoyl chloride in [bmim][BF4] gave almost exclusively the para adduct 68 (Scheme 24). This reaction can also be performed in organic solvents, but an accelerated rate is observed in ionic liquids.Catalyst loading can be decreased (up to 1 mol%) using bismuth(m) salts as catalysts. ... 

Friedel-Crafts (FC) alkylation, acylation, and sulfonylation reactions are important C-C or C-S bond forming reactions in organic chemistry [48]. Since the seminal works of Charles Friedel and James Mason Crafts published in 1877 in which they report the use of AICI3 for alkylation reactions [49], the search for more active catalysts especially for acylation reactions continues. Owing to increasing environmental concerns, the need for green catalysts and processes for the FC reaction has assumed significant importance. Bismuth(III) salts have shown to be efficient and recoverable catalysts in this area [50]. 

---