The first synthesis of cyclopropanone acetals from the reaction of Fischer carbene complexes with ketene acetals

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作者：

SLB Wang，DR Goldberg，X Liu，S Jing，QH Zheng，V Liptak，WD Wulff

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摘要：

The reaction of iso-propoxy stabilized Fischer carbene complexes with ketene acetals gives moderate to excellent yields of cyclopropanone acetals when carried out under a carbon monoxide atmosphere. This is in contrast to the known reaction of methoxy substituted complexes which give cyclic ortho esters under the same conditions. A mechanism is proposed which involves a branch point between the two products as the zwitterionic intermediate resulting from nucleophilic addition of the ketene acetal to the carbene carbon. A 1,3-migration of the methoxyl group to the cationic center leads to the ortho ester and a ring closure by backside attack leads to the cyclopropanone acetal. A double-labeling experiment shows that the 1,3-migration occurs by an intramolecular process that is proposed to involve a bridging oxonium ion. The effect of the isopropoxy group is thus interpreted to be to sterically hinder the formation of a bridged oxonium ion.

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关键词：

cyclopropane derivatives cyclopropanation reactions reactions of organo-metal compounds cycloalkylphenyl derivatives

DOI：

10.1016/j.jorganchem.2005.08.025

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年份：

2006