Highly Regio- and Stereoselective [3+2] Cyclopentanone Annulation Using a 3-(Alkylthio)-2-siloxyallyl Cationic Species

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• 作者：Keiichi Masuya ; Kei Domon ; Keiji Tanino ; and Isao Kuwajima
• 刊名：Journal of the American Chemical Society
• 出版年：1998
• 出版时间：March 4, 1998
• 年：1998
• 卷：120
• 期：8
• 页码：1724 - 1731
• 全文大小：439K
• 年卷期：v.120,no.8(March 4, 1998)
• ISSN：1520-5126

文摘

A new synthetic method for functionalized cyclopentanones wasdeveloped on the basis of a [3+2]cycloaddition reaction of a 1-(methylthio)-2-siloxyallyl cationicspecies and olefins. Allyl acetates 1a and1b,which are the precursors of the allyl cationic species, are easilyprepared in three or four steps from commerciallyavailable compounds. Under the influence of EtAlCl₂ orAlCl₃, 1a or 1b reacted with variouskinds of olefinssuch as enol ethers, vinyl sulfides, styrenes, and trialkylolefins toafford the corresponding cyclopentanones ingood yields. It is noteworthy that the sterically more hinderedregioisomer was predominantly formed inevery case. Furthermore, the reactions of 1b with vinylsulfides exhibited surprisingly high stereoselectivity,which can be rationalized by the six-membered transition state modelsinvolving an orbital interaction betweenthe sulfur atom of the vinyl sulfide and the -carbon of the allylcation.