Furo[3,4-b]benzodioxin Cycloadditions - A One-Pot Synthesis of Functionalized Bis-Adducts

Furo[3,4-b]benzodioxin 1 was found to undergo a doubleDiels–Alder reaction with several dienophiles. The diene reacts directly with the suitable dienophile to give the mono-adduct intermediate that unexpectedly leads to a second cycloaddition at the internal, electron-rich, oxabicyclic C4a–C10a double bond. The resulting bis-adducts were formed under relatively mild conditions with dienophiles ranging from maleic anhydride and dimethyl acetylenedicarboxylate to the extremely reactive arynes. With this methodology of two uninterrupted sequential cycloaddition reactions, interesting formation of stable bis-adducts was observed. The dienophile behavior of 1,4-benzodioxin is described for the first time in this work.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)