Chiral spirosiladiphosphines: ligand development and applications in Rh-catalyzed asymmetric hydrosilylation/cyclization of 1,6-enynes with enhanced reactivity

Abstract

Spirodiphosphines have been successfully applied in various asymmetric catalytic transformations. However, controlling the coordinating conformations by the direct displacement of the spiro atom remains elusive. Herein, we report the application of Si-centered spirodiphosphine (Si-SDP) ligands in the enantioselective hydrosilylation/cyclization of 1,6-enynes. The Si-SDPs showed superior reactivity to existing C2-symmetric diphosphines, allowing the generation of a range of chiral pyrrolidines with high yields and enantioselectivity (up to 96% yield and 92% ee) at room temperature with low catalyst loading. The mechanistic observations were consistent with the modified Chalk–Harrod mechanism, and the high reactivity of Si-SDPs was further leveraged for the room-temperature Rh-catalyzed hydrosilylation of alkynes.