Palladium-ene reaction

Intramolecular insertion of alkenes into ir-allylpalladium complexes has been shown to proceed regio-selectively to yield five-membered rings.2621263 TTiis transformation is equivalent to a palladium ene reaction and is completed by a (3-hydride elimination. The C==C bond of ketenes is also capable of undergoing insertion into ir-allylpalladium intermediates.264 The final course of this reaction is dependent on the leaving group in the initial allyl-X precursor. For X = OAc, dienes are observed for X = Me0C02, a methoxycarbonyl adduct is obtained (equation 303).264... 

Additional regio- and stereo-chemical information was obtained from palladium-ene reactions of strained alkenes. An instructive example is the reaction of stoichiometric amounts of the allylpalladium species (52) which undergo rapid, reversible formation of the cr-allylpalladium-norbomadiene complexes (53) to give at 37 °C the cis insertion products (54) (Scheme 12). Carbon-carbon bond formation (at the least substituted allyl terminal) and palladium transfer from the same (exo) face of norbomadiene were ascribed" to a o-allypalladium alkene insertion. 

An analogous regio- and stereo-selectivity characterizes the palladium-ene reaction (55) + (56) (57)... 

As expected, Pd(PPh3)4 also proved to be a suitable catalyst for intramolecular palladium-ene reactions (Scheme 42). Conversion (201) -> (202) illustrates the feasibility of this method for six-membered ring formation. Acetoxydiene (203), containing a cyclic enophile unit, furnished stereoselectively the bicy-... 

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