1,2-Stereochemical Induction in the PdII-Catalyzed Conjugate Addition of Boronic Acids

Palladium(II) catalysis has been used in the substrate‐controlled 1,2‐chiral induction of the conjugate addition of boronic acids to enantiopure α,β‐unsaturated ketones and esters without competition from the Mirozoki–Heck reaction. Bedford's palladacycle was found to control the stereoselectivity without the need for additional chiral ligands. We report that the PdII‐catalyzed conjugate addition reaction between boronic acids and acyclic ketones or esters that bear a hydroxyl substituent at their γ‐position (glyceraldehyde derivatives) can afford high levels of anti stereoselection, comparable to those reported previously using more expensive RhI catalysts. On the other hand, high levels of syn stereoselectivity were observed with acyclic esters that bear an amino substituent at their γ‐position (serine derivatives). In this case, the levels of stereoselection could be enhanced by using cyclic derivatives derived from Garner's aldehyde. PdII catalysis has been used for substrate‐controlled 1,2‐stereoselective conjugate addition of boronic acids to enantiopure α,β‐acyclic unsaturated ketones and esters without competition from the Mirozoki–Heck reaction. Best results were found with Bedford's palladacycle. The reaction with cyclic derivatives of Garner's aldehyde also took place with high levels of trans diastereoselectivity.