A wide array of forms of palladium has been utilized as precatalysts for Heck and Suzuki coupling reactions over the last 15 years. Historically, nearly every form of palladium used has been described as the active catalytic species. However, recent research has begun to shed light on the in situ transformations that many palladium precatalysts undergo during and before the catalytic reaction, and there are now many suggestions in the literature that narrow the scope of types of palladium that may be considered true “catalysts” in these coupling reactions. In this work, for each type of precatalyst, the recent literature is summarized and the type(s) of palladium that are proposed to be truly active are enumerated. All forms of palladium, including discrete soluble palladium complexes, solid-supported metal ligand complexes, supported palladium nano- and macroparticles, soluble palladium nanoparticles, soluble ligand-free palladium, and palladium-exchanged oxides are considered and reviewed here. A considerable focus is placed on solid precatalysts and on evidence for and against catalysis by solid surfaces vs. soluble species when starting with various precatalysts. The review closes with a critical overview of various control experiments or tests that have been used by authors to assess the homogeneity or heterogeneity of catalyst systems.

On the Nature of the Active Species in Palladium Catalyzed Mizoroki–Heck and Suzuki–Miyaura Couplings – Homogeneous or Heterogeneous Catalysis, A Critical Review

Hydrogenation is a core technology in chemical synthesis. High rates and selectivities are attainable only by the coordination of structurally well-designed catalysts and suitable reaction conditions. The newly devised [RuCl(2)(phosphane)(2)(1,2-diamine)] complexes are excellent precatalysts for homogeneous hydrogenation of simple ketones which lack any functionality capable of interacting with the metal center. This catalyst system allows for the preferential reduction of a C=O function over a coexisting C=C linkage in a 2-propanol solution containing an alkaline base. The hydrogenation tolerates many substituents including F, Cl, Br, I, CF(3), OCH(3), OCH(2)C(6)H(5), COOCH(CH(3))(2), NO(2), NH(2), and NRCOR as well as various electron-rich and -deficient heterocycles. Furthermore, stereoselectivity is easily controlled by the electronic and steric properties (bulkiness and chirality) of the ligands as well as the reaction conditions. Diastereoselectivities observed in the catalytic hydrogenation of cyclic and acyclic ketones with the standard triphenylphosphane/ethylenediamine combination compare well with the best conventional hydride reductions. The use of appropriate chiral diphosphanes, particularly BINAP compounds, and chiral diamines results in rapid and productive asymmetric hydrogenation of a range of aromatic and heteroaromatic ketones and gives a consistently high enantioselectivity. Certain amino and alkoxy ketones can be used as substrates. Cyclic and acyclic alpha,beta-unsaturated ketones can be converted into chiral allyl alcohols of high enantiomeric purity. Hydrogenation of configurationally labile ketones allows for the dynamic kinetic discrimination of diastereomers, epimers, and enantiomers. This new method shows promise in the practical synthesis of a wide variety of chiral alcohols from achiral and chiral ketone substrates. Its versatility is manifested by the asymmetric synthesis of some biologically significant chiral compounds. The high rate and carbonyl selectivity are based on nonclassical metal-ligand bifunctional catalysis involving an 18-electron amino ruthenium hydride complex and a 16-electron amido ruthenium species.

https://onlinelibrary.wiley.com/doi/pdf/10.1002/1521-3773%2820010105%2940%3A1%3C40%3A%3AAID-ANIE40%3E3.0.CO%3B2-5

Asymmetric Catalysis by Architectural and Functional Molecular Engineering: Practical Chemo‐ and Stereoselective Hydrogenation of Ketones

Selected patented cross-coupling reaction technologies.

3.1. C-M and X-H as Nucleophiles 1806 3.2. C-H and X-M as Nucleophiles 1809 3.2.1. C-Halogen Bond Formations 1809 3.2.2. C-O Bond Formations 1812 3.3. C-H and X-H as Nucleophiles 1812 3.3.1. C-O Bond Formations 1812 3.3.2. C-N Bond Formations 1815 4. Oxidative X-X Bond Formations between Two Nucleophiles 1819 5. Conclusions 1819 Author Information 1819 Biographies 1819 Acknowledgment 1820 References 1820

Bond Formations between Two Nucleophiles: Transition Metal Catalyzed Oxidative Cross-Coupling Reactions

1,2-Amino Alcohols and Their Heterocyclic Derivatives as Chiral Auxiliaries in Asymmetric Synthesis

A practical enantioselective synthesis of .alpha.,.alpha.-diaryl-2-pyrrolidinemethanol. Preparation and chemistry of the corresponding oxazaborolidines

An asymmetric synthesis of MK-0417. Observations on oxazaborolidine-catalyzed reductions

A specific combination, linked pro-drug or a compound of an angiotensin receptor antagonist and a NEPi are used in the treatment of hypertension.

Pharmaceutical combinations of an angiotensin receptor antagonist and an nep inhibitor

Reduction of nitroarenes to anilines using activated iron generated by Fe/HCl or Zn/FeSO 4 is described. A variety of functional groups such as alkyne, ketone, enone, nitrile, lactone, and aromatic halide are well tolerated under these conditions.

Thomas J. Blacklock

Papers

A practical enantioselective synthesis of .alpha.,.alpha.-diaryl-2-pyrrolidinemethanol. Preparation and chemistry of the corresponding oxazaborolidines

An asymmetric synthesis of MK-0417. Observations on oxazaborolidine-catalyzed reductions

Pharmaceutical combinations of an angiotensin receptor antagonist and an nep inhibitor

A Practical and Chemoselective Reduction of Nitroarenes to Anilines Using Activated Iron

LCZ696: a dual-acting sodium supramolecular complex