Synthesizing Chiral Hydrocarbazoles with a Tetrasubstituted Carbon Using Holmium-Catalyzed Enantioselective [4 + 2] Cycloaddition: Mechanistic Insights from Luminescence and DFT Studies.

This study analyzes the feasibility of utilizing the catalytic and enantioselective [4 + 2] cycloaddition of sterically demanding heterocycle-incorporated siloxydienes to yield polycyclic skeletons with a tetrasubstituted carbon. A catalyst derived from lanthanide triflimide enabled the reaction. The mechanistic investigations and transformations of the adducts are also discussed. The proposed approach facilitates the synthesis of intricate polysubstituted skeletons, each with multiple contiguous chiral centers, thereby aiding in the production of diverse hydrocarbazoles for drug discovery purposes.

Optically Active Helical Lanthanide Complexes: Storable Chiral Lewis Acidic Catalysts for Enantioselective Diels-Alder Reaction of Siloxydienes.

Lanthanide triflates and a series of hexadentate chiral ligand complexes were synthesized. X-ray-quality crystals were obtained from mixtures of the lanthanide complexes, which were helical in shape. The complexes showed Lewis acidity and catalyzed the enantioselective Diels-Alder reaction of electron-rich siloxydienes. The complexes were stable enough to be stored at ambient temperature on a laboratory bench and retained their Lewis acidity even after a month.