Thermally Induced Intramolecular Diels–Alder Reaction of Furan-Tethered Methylenecyclopropanes

The substantial ring strain and activated double bonds render methylenecyclopropanes (MCPs) potential substrates for Diels-Alder (DA) reactions. In this work, we present a thermally induced intramolecular Diels-Alder (IMDA) reaction utilizing furan-tethered MCPs. The reactions were carried out smoothly with respect to a wide variety of substrates with good functional group compatibility, affording the desired products in moderate to excellent yields. The synthetic utility of these products was successfully demonstrated. Mechanistic studies involving radical scavenger control experiments and density functional theory (DFT) calculations revealed a concerted mechanism involving an asynchronous one-step pathway.