A Cheap Metal for a "Noble" Task: Preparative and Mechanistic Aspects of Cycloisomerization and Cycloaddition Reactions Catalyzed by Low-Valent Iron Complexes

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• 作者：Alois Fü ; rstner ; Keisuke Majima ; Rubé ; n Mart&iacute ; n ; Helga Krause ; Egmont Kattnig ; Richard Goddard ; Christian W. Lehmann
• 刊名：Journal of the American Chemical Society
• 出版年：2008
• 出版时间：February 13, 2008
• 年：2008
• 卷：130
• 期：6
• 页码：1992 - 2004
• 全文大小：329K
• 年卷期：v.130,no.6(February 13, 2008)
• ISSN：1520-5126

文摘

Reaction of ferrocene with lithium in the presence of either ethylene or COD allows the Fe(0)-ate complexes 1 and 4 to be prepared on a large scale, which turned out to be excellent catalysts for avariety of Alder-ene, [4+2], [5+2], and [2+2+2] cycloadditon and cycloisomerization reactions ofpolyunsaturated substrates. The structures of ferrates 1 and 4 in the solid-state reveal the capacity of thereduced iron center to share electron density with the ligand sphere. This feature, coupled with the kineticlability of the bound olefins, is thought to be responsible for the ease with which different enyne or diynesubstrates undergo oxidative cyclization as the triggering event of the observed skeletal reorganizations.This mechanistic proposal is corroborated by highly indicative deuterium labeling experiments. Moreover,it was possible to intercept two different products of an oxidative cyclization manifold with the aid of theFe(+1) complex 6, which, despite its 17-electron count, also turned out to be catalytically competent incertain cases. The unusual cyclobutadiene complex 38 derived from 6 and tolane was characterized byX-ray crystallography.