Nickel-Catalyzed Asymmetric\n(3 + 2) Annulations of\nPropargylic Carbonates and Vinylogous Donors via an Alkenylation Pathway

The transition-metal-catalyzed alkenylation strategy\nof propargylic\nalcohol derivatives provides an efficient protocol to access multifunctional\nproducts in a double-nucleophilic attack pattern. While limited relevant\nasymmetric examples have been reported via palladium catalysis, here\nwe first demonstrate that a nonprecious Ni(0)-based chiral complex\ncan efficiently promote the tandem substitution process between propargylic\ncarbonates and <i>N</i>-trifluoroethyl ketimines via consecutive\naza-vinylogous activations, finally accomplishing a (3 + 2) annulation\nreaction to afford products embedding a 4-methylene-3,4-dihydro-2<i>H</i>-pyrrole framework with high regio-, diastereo-, and enantiocontrol.\nTheir assemblies with a few all-carbon-based vinylogous precursors\nare also successful, and enantioenriched adducts containing a 3-methylenecyclopentene\nscaffold are furnished effectively. The substitution patterns for\nboth types of substrates are substantial, and an array of synthetic\nelaborations is conducted to deliver more versatile architectures\nwith high application potential. In addition, density functional theory\ncalculations and control experiments have been conducted to rationalize\nthe catalytic pathways and regio- and enantioselectivity control.