Intramolecular Diels–Alder Reaction of Vinylsulfonic Acid Esters

The highly diastereoselective intramolecular Diels–Alder reaction of the vinylsulfonate esters of the hydroxyalkylfurans 1 (R = Me, Et, iPr) to give the sultones 2 occurs at room temperature. MNDO and MMPMI calculations indicate a thermodynamic control of the relative configurations of 2.