Friedel-Crafts acylation reactions graphite

Graphite can promote the Friedel-Crafts acylation reaction of active aromatic compounds such as anisoles and polymethylbenzenes with acyl halides to afford the corresponding aromatic ketones [101]. In a typical experiment, graphite is added to a mixture of anisole and benzoyl bromide in benzene, and the mixture is heated under reflux for 8h to afford para-methoxybenzophenone in 80% yield. Different acyl halides and several anisoles and polymethylbenzenes are utilized to give the corresponding products in high yields (60-92%). 

Use of graphite-supported methodology has been reported for three types of reaction - the Friedel-Crafts acylation [15, 16, 27, 66], the acylative cleavage of ethers [15, 16], and the ketodecarboxylation of carboxylic diacids [67, 68], either with conventional heating (GS/A) or MW irradiation (GS/MW coupling) these are discussed below. First, however, we describe the analysis of two commercial graphites of different purity which are used for these experiments. 

Consequently, a lot of research has been carried out in this area in order to find convenient catalysts, i.e. those able to activate the acylating reagent while giving labile complexes with ketones, in particular in hot conditions. Ferric chloride is the most common catalyst when the reaction is achieved in this manner (refs. 7, 8). With this same view, Friedel-Crafts acylation in the presence of small quantities of catalysts (for example FeCl3), is strongly activated by microwave irradiation, in particular when the catalyst is on a graphite substrate (ref. 9). 

In retrospect, it is ironic to it that when I met Ernst Schumacher in 1969 (he was then Professor at the University of Bern in Switzerland) we did not talk about the experiments he did at Zurich in the same building where I was at that time. Instead, his interest focussed on our work on borazine transition metal compounds and we discussed in some detail whether it would be possible to incorporate metal atoms like chromium or molybdenum between the layers of hexagonal boron nitride (BN) in a similar way as it can be done with graphite. In the course of these discussions I did not mention that, after I had moved to Zurich, we had begun to investigate the reactivity of nickelocene towards both nucleophilic and electrophilic substrates. The reason was that we were still at the beginning, and while we had been able to prepare a series of monocyclopentadienyl nickel complexes from Ni(C5H5)2 and Lewis bases, our attempts to obtain alkyl- or acyl-substituted nickelocenes by the Friedel-Crafts reaction failed. 

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