STEREOSELECTIVE SYNTHESIS OF 3a,4,5,7a-TETRAHYDRO-5,7a-ETHANOPHTHALIDE DERIVATIVES USING SUCCESIVE INTRA- AND INTERMOLECULAR DIELS-ALDER REACTIONS

Article abstract of DOI:10.1246/cl.1985.151

Some 2-pyrone-6-carboxylic acid esters bearing appropriate dienophiles at ester moieties underwent the intramolecular Diels-Alder reaction followed by the extrusion of carbon dioxide to give 3a,4-dihydrophthalide derivatives.The dihydrophthalides added to the second dienophiles intermolecularly to give 3a,4,5,7a-tetrahydro-5,7a-ethanophthalide derivatives.The stereoselectivity of the 5,7a-ethanophthalides was liable for the two successive reactions.