Fig. 1

Challenges in stereocontrolled Csp3 couplings. a Stereoselective couplings vs. stereospecific couplings. b Competing stereodivergent stereospecific transmetalation pathways. c Axial shielding—a ligand design principle for controlling stereochemistry in Csp3 couplings. Projecting steric bulk above and below the Pd (II) square plane should selectively inhibit stereoinvertive transmetalation, thus favoring stereoretention