Inverse-electron-demand Diels–Alder reactions of masked o-benzoquinones with enol ethers and styrene

Regio- and stereoslective inverse-electron-demand Diels–Alder reactions of masked o-benzoquinones (MOBs) 1a–1h derived from the corresponding 2-methoxyphenols 2a–2h with benzyl vinyl ether, dihydrofuran and styrene to afford the highly functionalized bicyclo[2.2.2]octenone derivatives are described. The MOBs having electron-deficient substituents were found to undergo more facile Diels–Alder cycloadditions with these dienophiles. The electron-rich dienophile dihydropyran is not a suitable 2π-partner for MOBs. Attempts are made to explain the observed regiochemistry of these Diels–Alder cycloadditions in terms of frontier molecular orbital theory.