Chemoselective tandem SN2′/SN2′′/inter- or intramolecular Diels–Alder reaction of γ-vinyl MBH carbonates with phenols and o-hydroxychalcones

Abstract

An unprecedented consecutive S_N2′/S_N2′′ addition of phenol to γ-vinyl MBH carbonate forms a reactive diene intermediate, followed by a dimerization/elimination process to give functionalized exocyclohexenes with excellent chemoselectivity. When using o-hydroxychalcones as pronucleophiles, an S_N2′/S_N2′′/intramolecular Diels–Alder reaction sequence occurs, selectively producing a series of pharmaceutically intriguing tricyclic chromane derivatives with good diastereoselectivity. The good nucleophilicity and fair nucleofugicity exhibited by phenoxy anion play a pivotal role in the S_N2′′ addition step.