Atroposelective Pd-Catalyzed C(sp ²)-P Coupling Enabling Modular Assembly of Axially Chiral QUINAPO Ligands

QUINAP ligands have been widely employed in a broad range of synthetically valuable asymmetric transformations, and their oxidized analogues, QUINAPOs, serve as effective Lewis base catalysts. Yet, a general and modular synthesis of these scaffolds has remained elusive. Herein, we present a Pd-catalyzed asymmetric C-(sp ²)-P coupling reaction of racemic heterobiaryl triflates with secondary phosphine oxides that furnishes axially chiral QUINAPOs in 47-98% yields and up to 95% ee across a broad substrate scope. The platform is diversity-oriented, enabling rapid access to structurally varied QUINAPO frameworks; subsequent deoxygenation delivers the corresponding QUINAP ligands. Representative members exhibit high activity and enantioselectivity in the asymmetric allylic alkylation and alkynylation of chromones, highlighting how ligand substitution modulates catalytic performance.