Dimerization reactions carbopalladation

While the PNP dimer was an efficient catalyst for the ort/toalkylation/ Mizoroki-Heck reaction, the practicality of the transformation is lessened by the fact that the PNP dimer is not commercially available, and can be quite difficult to prepare. Thus, Catellani adapted the reaction conditions to include commercially available and air-stable Pd(OAc)2 as the catalyst source [46], Under these conditions, the ortho-u kylation/Mizoroki-I Ieck coupling of aryl iodides containing a pre-existing ortho substituent could be carried out. The reaction required higher temperatures, and the addition of KOAc to promote the carbopalladation of norbomene [47] and encourage the o/t/zo-alkylation pathway vs a direct Mizoroki-Heck coupling. 

There are only a few cases of an intermolecular reaction of a 7r-allylpalladium complex with an alkene. The carbopalladation of norbomadiene with a stoichiometric amount of a TT-allylpalladium complex to yield an allyl-substituted a--norbomenylpalladium species has been reported In the context of mechanistic studies of Pd-catalyzed alkene dimerization, the insertion of ethylene into a cationic 7r-allylpalladium complex was also reported as a stoichiometric reaction in 1996 (Scheme... 

Catalytic carbopalladation is a ubiquitous process and alkynes are viable substrates. Alkenyl tellurides couple efficiently with alkynes with retention of the double bond geometry. Relatively large amounts of palladium catalyst are required.Oxidative dimerization of monoterpenes has been assumed to involve alkenylpalladium(ii) intermediates. Alkenylpalladium(ii) and di(alkenyl)palladium(iv) complexes have been put forward as intermediates in a similar reaction of halogenoterpenes. The subject has been reviewed concerning the formation of heterocycles by intramolecular cyclization of intermediate alkenylpalladium intermediates. ... 

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