285 Cross- and Multi-Coupling Reactions Using Anionic Transition Metal Complexes

Thursday, November 5, 2009: 1:40 PM
Longhorn (Camino Real Hotel)
Jun Terao , Department of Energy and Hydrocarbon Chemistry, Graduate School of Engineering, Kyoto University, Kyoto, Japan
Anionic complexes formed by the reaction of neutral complexes with organometallic reagents possess high electron densities. Consequently, it is considered that the nucleophilicity at the metal center or π-carbon ligands, and the electron-donating ability of anionic complexes would be enhanced in comparison with the corresponding neutral complexes. We have developed new methodologies for carbon-carbon and carbon-silicon bond forming reactions using alkyl halides and/or chlorosilanes by drawing focus to these characteristics of an anionic complex. I) We developed new catalytic systems of cross-coupling reaction that do not involve the oxidative addition of alkyl halides toward M(0) complexes but proceeds via an anionic complex as key intermediate. A key to attain this new catalytic pathway is to use 1,3-butadiene derivatives instead of phosphine ligands as an additive. II) We proposed a new methodology for enhancing back-donation from metal by forming an anionic transition metal complex generated by the reaction of an olefin complex with organometallic reagents and succeeded in the development of Zr-catalyzed silylation of olefins via the process of nucleophilic activation of coordinate olefins as a key step. When we applied this method to Ni and Pd complexes having π-carbon ligands, such as allyl, 1,3-dienyl, and bis-π-allyl ligands, it was found that these ligands were also activated as nucleophiles which efficiently reacted with alkyl halides or chlorosilanes to achieve new C-C and C-Si bond forming reactions. III) We also found that anionic Ti and Ni complexes bear high ability of electron transfer to alkyl halides resulting in the formation of alkyl radical species and developed an unprecedented multi-component coupling reaction.