Asymmetric annulations based on cycloisomerization of cyclopropyl tethered allenyl ketones by bimetallic relay catalysis

IronIII-catalyzed asymmetric inverse-electron-demand hetero-Diels–Alder reaction of dioxopyrrolidines with simple olefins

“…HOMO-raising strategies, employing enamine 8 or enolate activation 9 with organocatalysts, further broaden the scope of dienophiles. The generation of active dienophiles in situ , exemplified by the conversion of 3-cyclopropylideneprop-2-enone into cyclobutene-fused furans 10 or the oxidation of ethers, 11 facilitates rapid and alternative access to cycloaddition products. In contrast, IEDHDA reaction of simple alkenes is generally challenging 12,14 and achievable only by lowering the LUMO of hetero-dienes.…”

Asymmetric Synthesis of Hydrodibenzofurans from Norcaradienes: Kinetic Resolution via [3 + 2] Cycloaddition with Quinones

“…Actually, there might be competitive cycloaddition processes, such as norcaradienes performing [4 + 2] cycloaddition, similar to the reaction of acyclic dienes or unsaturated aldehydes shown in path b of Scheme b, or [2 + 2] cycloaddition with fulvenes (Scheme b, path c) . Alternatively, the [2 + 2] adduct might follow an isomerization to give 2,3-dihydrobenzofurans. , Encouraged by our endeavor in developing chiral Lewis acids of N , N ′-dioxides, herein we report the catalytic asymmetric synthesis of cyclopropane-fused hydrodibenzofurans from racemic NCDs which acted as C 2 synthons with both quinones and naphthoquinones. Kinetic resolution of norcaradienes was successful, and reversal of enantioselectivity was realized by switching metal ions in the presence of the same ligand …”