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

Abstract

The transition-metal-catalyzed alkenylation strategy of propargylic alcohol derivatives provides an efficient protocol to access multifunctional products in a double-nucleophilic attack pattern. While limited relevant asymmetric examples have been reported via palladium catalysis, here we first demonstrate that a nonprecious Ni(0)-based chiral complex can efficiently promote the tandem substitution process between propargylic carbonates and N-trifluoroethyl ketimines via consecutive aza-vinylogous activations, finally accomplishing a (3 + 2) annulation reaction to afford products embedding a 4-methylene-3,4-dihydro-2H-pyrrole framework with high regio-, diastereo-, and enantiocontrol. Their assemblies with a few all-carbon-based vinylogous precursors are also successful, and enantioenriched adducts containing a 3-methylenecyclopentene scaffold are furnished effectively. The substitution patterns for both types of substrates are substantial, and an array of synthetic elaborations is conducted to deliver more versatile architectures with high application potential. In addition, density functional theory calculations and control experiments have been conducted to rationalize the catalytic pathways and regio- and enantioselectivity control.