著者

町口 孝久 山辺 信一

出版者

The Society of Synthetic Organic Chemistry, Japan

雑誌

有機合成化学協会誌 (ISSN:00379980)

巻号頁・発行日

vol.55, no.1, pp.56-64, 1997-01-01 (Released:2009-11-16)

参考文献数

48

被引用文献数

2

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Non-recognition for dienes in ketene reactions has long been an important problem in organic chemistry since the diphenylketene-cyclopentadiene reaction was found by Staudinger in 1920. Recently, we have discovered that the ketene recognizes conjugated dienes. The ketene is a dienophile not for well-known [2+2] cycloadditions but for [4+2] (Diels-Alder) reactions across its C=O bond. This paper outlines the long history of ketene chemistry and describes the way of how the problem has been tackled. The frontier-orbital theory and ab initio calculations have predicted that ketene should react with cyclopentadiene via the [4+2] cycloaddition and a subsequent Claisen rearrangement. Careful low-temperature experiments and NMR spectroscopy of the reaction have demonstrated the first detection of the [4+2] -type cycloadduct and the conversion to the final product, cyclobutanone, by the rearrangement.