Palladium-Catalyzed Stereo- and Regiospecific Allylation of Aryl Halides with Homoallyl Alcohols via Retro-Allylation:  Selective Generation and Use of σ-Allylpalladium

Treatment of tertiary homoallyl alcohol with aryl halide under palladium catalysis resulted in the transfer of the allyl moiety of the homoallyl alcohol to aryl halide and yielded the corresponding cross-coupling product stereo- and regiospecifically. The transfer process includes retro-allylation, which proceeds via a conformationally regulated six-membered transition state. The retro-allylation can be regarded as a method for the stereo- and regiospecific preparation of sigma-allylpalladium.