Synthesis of Furanophane Derivatives through [8+2]-Cycloaddition of Dienylisobenzofurans and Alkynes

The coupling of various dienylisobenzofurans with dimethyl acetylenedicarboxylate (DMAD) has been examined. In most cases, this reaction proceeds via [8+2]-cycloaddition to afford furan-bridged decatetraene ring systems. The major competing reaction pathway is [4+2]-cycloaddition between DMAD and the isobenzofuran nucleus. Isobenzofuran intermediates were generated using either a chromium carbene-based method or an acid-catalyzed method.