The catalytic enantioselective synthesis of α‐chiral alkenes and alkynes represents a powerful strategy for rapid generation of molecular complexity. Herein, we report a transient directing group (TDG) strategy to facilitate site‐selective palladium‐catalyzed reductive Heck‐type hydroalkenylation and hydroalkynylation of alkenylaldehyes using alkenyl and alkynyl bromides, respectively, allowing for construction of a stereocenter at the δ‐position with respect to the aldehyde. Computational studies reveal the dual beneficial roles of rigid TDGs, such as L‐
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Abstract tert ‐leucine, in promoting TDG binding and inducing high levels of enantioselectivity in alkene insertion with a variety of migrating groups. -
Abstract The site‐selective palladium‐catalyzed three‐component coupling of unactivated alkenyl carbonyl compounds, aryl‐ or alkenylboronic acids, and
N ‐fluorobenzenesulfonimide is described herein. Tuning of the steric environment on the bidentate directing auxiliary enhances regioselectivity and facilitates challenging C(sp3)−F reductive elimination from a PdIVintermediate to afford 1,2‐carbofluorination products in moderate to good yields. -
Abstract The site‐selective palladium‐catalyzed three‐component coupling of unactivated alkenyl carbonyl compounds, aryl‐ or alkenylboronic acids, and
N ‐fluorobenzenesulfonimide is described herein. Tuning of the steric environment on the bidentate directing auxiliary enhances regioselectivity and facilitates challenging C(sp3)−F reductive elimination from a PdIVintermediate to afford 1,2‐carbofluorination products in moderate to good yields. -
Abstract Metal‐coordinating directing groups have seen extensive use in the field of transition‐metal‐catalyzed alkene functionalization; however, their waste‐generating installation and removal steps limit the efficiency and practicality of reactions that rely on their use. Inspired by developments in asymmetric organocatalysis, where reactions rely on reversible covalent interactions between an organic substrate and a chiral mediator, we have developed a transient‐directing‐group approach to reductive Heck hydroarylation of alkenyl benzaldehyde substrates that proceeds under mild conditions. Highly stereoselective migratory insertion is facilitated by in situ formation of an imine from catalytic amounts of a commercially available amino acid additive. Computational studies reveal an unusual mode of enantioinduction by the remote chiral center in the transient directing group.
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Abstract Metal‐coordinating directing groups have seen extensive use in the field of transition‐metal‐catalyzed alkene functionalization; however, their waste‐generating installation and removal steps limit the efficiency and practicality of reactions that rely on their use. Inspired by developments in asymmetric organocatalysis, where reactions rely on reversible covalent interactions between an organic substrate and a chiral mediator, we have developed a transient‐directing‐group approach to reductive Heck hydroarylation of alkenyl benzaldehyde substrates that proceeds under mild conditions. Highly stereoselective migratory insertion is facilitated by in situ formation of an imine from catalytic amounts of a commercially available amino acid additive. Computational studies reveal an unusual mode of enantioinduction by the remote chiral center in the transient directing group.