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Mechanistically Driven Development Of Iridium Catalysts For Asymmetric Allylic Substitution, John F. Hartwig, Levi M. Stanley
Mechanistically Driven Development Of Iridium Catalysts For Asymmetric Allylic Substitution, John F. Hartwig, Levi M. Stanley
Levi M. Stanley
Enantioselective allylic substitution reactions comprise some of the most versatile methods for preparing enantiomerically enriched materials. These reactions form products that contain multiple functionalities by creating carbon−nitrogen, carbon−oxygen, carbon−carbon, and carbon−sulfur bonds. For many years, the development of catalysts for allylic substitution focused on palladium complexes. However, studies of complexes of other metals have revealed selectivities that often complement those of palladium systems. Most striking is the observation that reactions with unsymmetrical allylic electrophiles that typically occur with palladium catalysts at the less hindered site of an allylic electrophile occur at the more hindered site with catalysts based on other …
Iridium-Catalyzed Kinetic Asymmetric Transformations Of Racemic Allylic Benzoates, Levi M. Stanley, Chen Bai, Mitsuhiro Ueda, John F. Hartwig
Iridium-Catalyzed Kinetic Asymmetric Transformations Of Racemic Allylic Benzoates, Levi M. Stanley, Chen Bai, Mitsuhiro Ueda, John F. Hartwig
Levi M. Stanley
Versatile methods for iridium-catalyzed, kinetic asymmetric substitution of racemic, branched allylic esters are reported. These reactions occur with a variety of aliphatic, aryl, and heteroaryl allylic benzoates to form the corresponding allylic substitution products in high yields (74−96%) with good to excellent enantioselectivity (84−98% ee) with a scope that encompasses a range of anionic carbon and heteroatom nucleophiles. These kinetic asymmetric processes occur with distinct stereochemical courses for racemic aliphatic and aromatic allylic benzoates, and the high reactivity of branched allylic benzoates enables enantioselective allylic substitutions that are slow or poorly selective with linear allylic electrophiles.