Benzene, reaction with metal-exchanged

Attempt to prepare Jt-complexes of triafulvenes and related methylene cyclopro-parenes285,427 428 directly by ligand exchange reaction with transition metal complexes resulted in metal insertion into the sigma bond, forming metallacyclic complexes. Thus reaction of the electron-poor triafulvene l,2-diphenyl-3-dicyanomethylenecyclopropene with (ethylene)bis(triphenylphosphine)platinum in refluxing benzene gave two crystalline products whose platinacyclobutene structure was confirmed by X-ray structure analysis (equation 364)429. 

A reaction that furans and thiophenes do particularly well and that fits well with these last two reactions is metallation, particularly lithiation, of a C-H group next to the heteroatom and we will discuss this next. Lithiation of benzene rings (Chapter 9) is carried out by lithium-halogen (Br or I) exchange—a method that works well for heterocycles too as... 

For the gas-phase acylation reaction of aromatics with anhydrides, metal-exchanged zeolites are also employed. In the presence of CeZSM-5, the acylation of benzene with AAN affords AP with 86% conversion of AAN and 95% selectivity on the contrary, unmodified ZSM-5 is found to be less active under the same reaction conditions (71% conversion of AAN, 86% selectivity to AP). If the reaction is carried out with AAC as acylating... 

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