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  • Developing ligands for palladium(II)-catalyzed C-H functionalization: intimate dialogue between ligand and substrate.

Developing ligands for palladium(II)-catalyzed C-H functionalization: intimate dialogue between ligand and substrate.

The Journal of organic chemistry (2013-04-10)
Keary M Engle, Jin-Quan Yu
ABSTRACT

Homogeneous transition-metal-catalyzed reactions are indispensable to all facets of modern chemical synthesis. It is thus difficult to imagine that for much of the early 20th century, the reactivity and selectivity of all known homogeneous metal catalysts paled in comparison to their heterogeneous and biological counterparts. In the intervening decades, advances in ligand design bridged this divide, such that today some of the most demanding bond-forming events are mediated by ligand-supported homogeneous metal species. While ligand design has propelled many areas of homogeneous catalysis, in the field of Pd(II)-catalyzed C-H functionalization, suitable ligand scaffolds are lacking, which has hampered the development of broadly practical transformations based on C-H functionalization logic. In this Perspective, we offer an account of our research employing three ligand scaffolds, mono-N-protected amino acids, 2,6-disubstituted pyridines, and 2,2'-bipyridines, to address challenges posed by several synthetically versatile substrate classes. Drawing on this work, we discuss principles of ligand design, such as the need to match a ligand to a particular substrate class, and how ligand traits such as tunability and modularity can be advantageous in reaction discovery.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
Palladium, wire, diam. 0.5 mm, 99.9% trace metals basis
Sigma-Aldrich
Palladium, powder, <75 μm, 99.9% trace metals basis
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Palladium, powder or granules, 99.99% trace metals basis
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Palladium, powder, 99.995% trace metals basis
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Palladium, foil, thickness 0.5 mm, 99.9% trace metals basis
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Palladium, foil, thickness 0.025 mm, 99.9% trace metals basis
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Palladium, sponge, 99.9% trace metals basis
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Palladium, wire, diam. 1.0 mm, 99.9% trace metals basis
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Palladium, foil, thickness 1.0 mm, 99.9% trace metals basis
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Palladium, foil, thickness 0.25 mm, 99.98% trace metals basis
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Palladium, nanopowder, <25 nm particle size (TEM), ≥99.5%
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Palladium, evaporation slug, diam. × L 0.6 cm × 0.6 cm, 99.95% trace metals basis
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Palladium, powder, <1 μm, ≥99.9% trace metals basis
Palladium, foil, light tested, 100x100mm, thickness 0.025mm, as rolled, 99.99+%
Palladium, foil, light tested, 100x100mm, thickness 0.075mm, as rolled, 99.95%
Palladium, foil, 8mm disks, thickness 0.50mm, as rolled, 99.95%
Palladium, foil, 8mm disks, thickness 0.25mm, as rolled, 99.95%
Palladium, foil, light tested, 100x100mm, thickness 0.025mm, as rolled, 99.95%
Palladium, foil, light tested, 100x100mm, thickness 0.047mm, as rolled, 99.95%
Palladium, foil, not light tested, 25x25mm, thickness 0.003mm, 99.95%
Palladium, foil, light tested, 25x25mm, thickness 0.004mm, 99.95%
Palladium, foil, 15mm disks, thickness 0.025mm, as rolled, 99.99+%
Palladium, foil, 0.2m coil, thickness 0.1mm, coil width 2mm, as rolled, 99.95%
Palladium, foil, 6mm disks, thickness 0.025mm, as rolled, 99.95%
Palladium, foil, 25mm disks, thickness 0.02mm, as rolled, 99.95%
Palladium, foil, 10mm disks, thickness 0.075mm, as rolled, 99.95%
Palladium, foil, 4mm disks, thickness 0.03mm, as rolled, 99.95%
Palladium, foil, 25x25mm, thickness 0.1mm, as rolled, 99.95%
Palladium, foil, 6mm disks, thickness 0.02mm, as rolled, 99.95%
Palladium, foil, 10mm disks, thickness 0.25mm, as rolled, 99.95%