Highly selective synthesis of multi-substituted olefins mediated by zirconocene complexes

In this paper, the efficient methodology for the synthesis of multi-substituted olefins by using zirconocene complexes is described. The key step is regioselective formation of zirconacyclopen-tenes from alkynylboron and alkynylsilane compounds. The subsequent Negishi and Suzuki-Miyaura coupling reactions of C-B and C-Zr bonds give rise to multi-substituted olefins. The developed reaction can be applicable to the synthesis of various functional molecules, for example, an anti-cancer agent. In addition, the mechanism for a regioselective formation of zirconacyclopentenes is analyzed by reactions of alkynylboronates and a zirconocene (II) complex. As a result, it is disclosed that an electrostatic interaction effected the regioselective formation of zirconacyclopen-tenes. The synthesis of various unprecedented tri- and tetra-alkylated olefins using β-hydrogencontaining alkyl electrophiles and alkylzinc reagents as coupling partners in regio- and stereocontrolled manners is also described.