Journal of Organic Chemistry 2002-10-04

Direct addition of Zr-C bonds of alkylzirconocenes to activated alkenes.

Yuanhong Liu, Baojian Shen, Martin Kotora, Kiyohiko Nakajima, Tamotsu Takahashi

Index: J. Org. Chem. 67(20) , 7019-28, (2002)

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Abstract

Direct addition of alkylzirconocenes to activated alkenes was found, for the first time. Octyl- and decylzirconocene chloride reacted with benzylidenemalononitrile to give the corresponding addition products after hydrolysis in 86% and 79% yield, respectively. Zirconacyclopentanes showed a similar reactivity toward activated alkenes with a two-electron-withdrawing group. On the other hand, treatment of the reaction mixture of zirconacyclopentanes and ylidenemalononitriles with iodine afforded six-membered cyclic compounds in high yields. The diastereoselectivity of the cyclized compound was remarkably high and the high selectivity originated from the Zr-promoted cyclization. The structures of cyclic compounds 10b and the major diastereoisomer of 10d were determined by X-ray analysis. Zirconacyclopentenes reacted with ylidenemalononitrile with high chemoselectivity in which the sp(3)-carbon attached to zirconium reacted with ylidenemalononitrile.