One-Pot Allylation–Intramolecular Vinylogous Michael Addition–Isomerization Cascade of<i>o</i>-Hydroxycinnamates and Congeners: Synthesis of Substituted Benzofuran Derivatives

Abstract

A unique intramolecular vinylogous Michael addition leading to the synthesis of heterocycles has been disclosed. Base-promoted one-pot sequential O-allylation of o-hydroxy-cinnamates or -cinnamonitrile or -chalcones with γ-bromocrotonates followed by an intramolecular conjugate addition of vinylogous Michael donors resulted in the formation of highly substituted benzofuran derivatives in good to excellent yields. The intramolecular event followed by two [1,3]-H shifts leading to aromatization appears to be the key to the success of this unprecedented transformation.