Development of Novel Synthetic Methods by Cooperative Use of Metalacycles and Late Transition Metal Catalysts

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In this work, we have developed novel synthetic methods of unsaturated organic compounds by metalacycles and late transition-metal catalysts. With zirconacyclopentadienes and nickel complexes, catalytic synthetic methods of benzene and polycyclic aromatic compounds were found and developed. Moreover, copper-catalyzed synthesis of diallenes from reactions of zirconacyclopentanes with propargyl halides was developed.It was found that a series of nickel-catalyzed cycloaddition reactions of zirconacyclopentadienes with alkenes and alkynes. In the presence of a catalytic amount of nickel(II) chloride bis(triphenylphosphine), a zirconacyclopentadiene reacted with 2 equiv of 1-haloalkyne or allyl halide to afford the corresponding alkynylbenzene or pentasubstituted benzene, respectively. This is striking contrast to the reaction with copper(I) chloride as a catalyst, which produced the corresponding bis(alkynyl)butadiene.It was developed that coupling reactions of zirconacyclopentadienes and … More 1,2-dihalobenzenens mediated or catalyzed by nickel complexes to afford the corresponding polycyclic compounds. By the precedent method of the coupling reaction which is mediated by copper(I) chloride, the applicable dihaloarenes were limited for the diiodo- or bromoiodoarenes. Substitution of copper(I) to nickel(0) complex, however, raised the reactivity of the zirconacycles toward dibromo- and even dichlorobenzenes. Furthermore, the use of 3-(trifluoromethyl)styrene improved the reaction for the nickel-catalyzed one. That is, in the presense of 10 mol% of Ni(cod)_2 and 20 mol% of PPh_3, the reaction of a zirconacyclopentadiene with 1,2-dihalobenzene afforded the corresponding naphthalene in a good yield. The method was applied for various zirconacyclopentadienes and dihalobenzenes.Reactions of zirconacyclopentanes with propargyl halides in the presence of copper(I) salt were investigated. In the presence of copper(I) chloride, zirconacyclopentanes reacted with two equivalents of a propargyl halide to give bisallenylation products in moderate to high yields. By controlling the amount of CuCl, stepwise allenylation was achieved and a variety of unsymmetrically substituted diallene derivatives were prepared as well. Less