Transition metal catalyzed cycloaddition and related carbon-carbon bond forming reactions are described. Zerovalent palladium species catalyze the cyclocoupling between two molecules of electron-deficient alkynes or 1, 6-diynes and alkenes or alkynes. Intramolecular [2+2+2] cycloaddition of dimethyl 5, 10-dioxa-tetradeca-2, 7, 12-triynediolate induces bis-annulation of 2, 5-dihydrofuran to give the corresponding phthalate derivative involving two 2, 5-dihydrofuran moieties. In stoichiometric reaction with Pd
2 (dba)
3, the triyne furnishes a planar three-coordinated triyne complex of palladium. The cationic pentamethylcyclopentadienylruthenium (II) fragment, Cp
*Ru
+ (Cp
*=η
5-C
5Me
5) induces [4+4] cycloaddition of butadiene and isoprene. The pentamethylcyclopentadi-enylruthenium (II) chloride fragment, Cp
*RuCl, is a highly efficient catalyst to induce [2+2+2] cycloaddition of 1, 6-diynes with several carbon-carbon and carbon-nitrogen multiple bonds to furnish bicyclic arenes, cyclohexadienes, pyridines, 2, 2'-dipyridyl derivatives, and pyridones fused by cyclopentane, 2, 5-dihydrofuran or pyrrolidine moieties. An indenylchlororuthenium (II) fragment induces unprecedented catalytic bis-cyclopropanation in the reaction of 1, 6-diynes with strained bicycloalkenes.
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