Medium-Ring Effects on the Endo/Exo Selectivity of the Organocatalytic Intramolecular Diels-Alder Reaction

摘要: The intramolecular Diels-Alder reaction has been used as a powerful method to access the tricyclic core of eunicellin natural products from number 9-membered-ring precursors. endo/exo selectivity this can be controlled through remarkable organocatalytic approach, employing MacMillan's imidazolidinone catalysts, although mechanistic origin remains unclear. We present combined experimental and density functional theory investigation, providing insight into effects medium-ring constraints on organocatalyzed form isobenzofuran eunicellins.