Alkene derivatives acylpalladation

All of the acylpalladation processes discussed above involve interaction of acylpalladium bonds with C=C bonds. The corresponding acylpalladation of C C bonds proved to be rather elusive. Thus, for example, attempts to observe cyclic acylpalladation of alkyne-containing iodobenzenes totally failed, even though the corresponding alkene derivatives undergo cyclic acylpalladationt (Scheme 23). The contrasting behavior of alkene and alkyne substrates is also schematically summarized in Scheme 23. 

The complexity of this reaction scheme already points out the necessary time-balance between oxidative addition, CO insertion versus deinsertion (decarbonylation), acylpalladation, carbopaUadation, and dehydropalladation events to have a selective acylpallada-tion-type reaction. This has been more recently addressed by selecting acyl chlorides that could not readily undergo dehydropalladation, hence stabilizing the organopalladium intermediates to favor their intramolecular reaction with alkenes. For instance, Pd(OAc)2 catalyzes the reaction of benzoyl chloride derivatives with enol ethers (R = OEt, Scheme 3) to give the corresponding acylpalladation products typically in 40-77% yields. " ... 

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