A New Synthetic Method for Cyclopentanones via Formal [3+2] Cycloaddition Reaction

Abstract

A new synthetic method for cyclopentanone derivatives via formal [3+2] cycloaddition reaction of 2-oxyallyl cation and an alkene was developed. Under the influence of EtAlCl2 or AlCl3, 3-acetoxy-1-(methylthio)-2-(triisopropylsiloxy)-2-tridecene reacted with various kinds of alkenes to afford 2-(methylthio)cyclopentanone derivatives in good yield. The reaction was highly regioselective to yield the sterically more hindered regioisomer, which indicates that the initial C-C bond formation reaction between an alkene and the (1-(methylthio)-2-siloxy)allyl cation intermediate occurs at the γ-position of sulfur.