3.7. Palladium Nanoparticles as Catalysts 888 3.8. Other Transition-Metal Complexes 888 3.9. Transition-Metal-Free Reactions 889 4. Applications 889 4.1. Alkynylation of Arenes 889 4.2. Alkynylation of Heterocycles 891 4.3. Synthesis of Enynes and Enediynes 894 4.4. Synthesis of Ynones 896 4.5. Synthesis of Carbocyclic Systems 897 4.6. Synthesis of Heterocyclic Systems 898 4.7. Synthesis of Natural Products 903 4.8. Synthesis of Electronic and Electrooptical Molecules 906

https://www.chem.ccu.edu.tw/~joyce/referance/ericyang/Chem.%20Rev/Chem.%20Rev.%202007,%20107,%20874-922.pdf

The Sonogashira Reaction: A Booming Methodology in Synthetic Organic Chemistry†

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

Conjugated alkynes are recurring building blocks in natural products, a wide range of industrial intermediates, pharmaceuticals and agrochemicals, and molecular materials for optics and electronics. The palladium-catalyzed cross-coupling between sp2-hybridized carbon atoms of aryl, heteroaryl, and vinyl halides with sp-hybridized carbon atoms of terminal acetylenes is one of the most important developments in the field of alkyne chemistry over the past 50 years. The seminal work of the 1970s has initiated an intense search for more general and reliable reaction conditions. The interest in the catalytic activation of demanding substrates, the need to minimize the consumption of depletive resources, and the search for easy access to an increased variety of functionalized enynes has led to the current generations of high-turnover catalysts. This Review gives an overview of the highly efficient palladium catalyst systems for the direct alkynylation of C(sp2) halides with terminal alkynes, both in homogeneous and heterogeneous phases.

Palladium-based catalytic systems for the synthesis of conjugated enynes by Sonogashira reactions and related alkynylations

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Chemicals from Alkynes with Palladium Catalysts

This review discusses the problems associated with developing high-turnover catalysts for the cross-coupling and Heck reactions. New developments in the area, principally constituted by palladacycles and coordinatively unsaturated Pd catalysts featuring bulky phosphanes of high donicity, are reviewed from a mechanistic and synthetic standpoint, and compared with more traditional catalysts obtained from conventional mono- and polydentate N- and P-based ligands, as well as Pd catalysts without strong ligands, such as Pd colloids or heterogeneous catalysts. Carbene ligands are also briefly presented. Whereas a single, most promising approach to high-turnover Pd catalysis cannot presently be defined, it is clear that the new “PdL1” catalysts (where L1 is a monodentate bulky P ligand of high donicity) represent the latest, most important development in Pd research, certainly from the standpoint of scope and probably also from the standpoint of efficiency. High turnovers with these catalysts have been described and their use will certainly increase in the next few years. The review ends with a brief discussion containing practical considerations on how to choose a high TON catalyst for a given Heck or cross-coupling reaction of interest.

High‐Turnover Palladium Catalysts in Cross‐Coupling and Heck Chemistry: A Critical Overview

Di-2-pyridylmethylamine-Based Palladium Complexes as New Catalysts for Heck, Suzuki, and Sonogashira Reactions in Organic and Aqueous Solvents†

Palladium(II) Chloride and a (Dipyridin‐2‐ylmethyl)amine‐Derived Palladium(II) Chloride Complex as Highly Efficient Catalysts for the Synthesis of Alkynes in Water or in NMP and of Diynes in the Absence of Reoxidant

Symmetrical internal alkynes can be prepared either by diarylation of mono- and bis(trimethylsilyl)acetylene (TMSA and BTMSA) catalyzed by ligand-less palladium(II) chloride or by a di(2-pyridyl)methylamine-derived palladium(II) chloride complex 1 (typical 0.1–1 mol % of Pd loading) in water using pyrrolidine as base and tetra-n-butylammonium bromide as additive. Alternatively, this same process is performed in NMP in the presence of tetra-n-butylammonium acetate (TBAA) as base with even lower Pd loadings (0.001–1 mol % Pd). The same reaction conditions are applied to the synthesis of unsymmetrical internal alkynes by monoarylation of silylated terminal alkynes. Aryl iodides can be coupled with TMSA, BTMSA and silylated terminal alkynes under heating or at room temperature, whereas for aryl bromides couplings are performed under water reflux or at 110 °C in the case of NMP. Complex 1 can be reused during several cycles either in water or in NMP without loss of catalytic activity. These simple reaction conditions allow the preparation of internal alkynes without secondary products, most probably by succesive protiodesilylation-Sonogashira coupling.

Direct Coupling Reactions of Alkynylsilanes Catalyzed by Palladium(II) Chloride and a Di(2-pyridyl)methylamine-Derived Palladium(II) Chloride Complex in Water and in NMP

The (dipyridin-2-ylmethyl)amine-derived palladium chloride complex 1 and PdCl2 are efficient catalysts for cross-coupling reactions between terminal alkynes and aryl iodides or bromides under modified Sonogashira–Cassar–Heck conditions. The alkynylation can be performed under copper-free conditions in water at reflux or at room temperature under air with pyrrolidine as base and tetra-n-butylammonium bromide (TBAB) as additive, with TONs of up to 7 × 104 and TOFs(h–1) of up to 6666. Terminal alkynes can be arylated in NMP as well under copper- and amine-free conditions at 110 °C or room temperature, with tetra-n-butylammonium acetate (TBAA) acting as base with TONs up to 2 × 105 and TOFs (h–1) up to 66 666. In general, complex 1 displays a slightly higher efficiency than PdCl2 as catalyst and maintains the same activity after five consecutive runs. Alternatively, these alkynylation processes can be carried out under microwave heating conditions. The homocoupling of terminal alkynes to the corresponding 1,3-diynes proceeds under phosphane-free conditions with the (dipyridin-2-ylmethyl)amine-derived palladium chloride complex 1 or with PdCl2 as catalysts and with CuI as cocatalyst in NMP with use of either TBAA or pyrrolidine as bases. This Glaser-type reaction can be performed at 110 °C or at room temp. in the presence of air without the use of a reoxidant. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)

Palladium(II) Chloride and a (Dipyridin-2-ylmethyl)amine-Derived Palladium(II) Chloride Complex as Highly Efficient Catalysts for the Synthesis of Alkynes in Water or in NMP and of Diynes in the Absence of Reoxidant.

Direct Coupling Reactions of Alkynylsilanes Catalyzed by Palladium(II) Chloride and a Di(2‐pyridyl)methylamine‐Derived Palladium(II) Chloride Complex in Water and in NMP.

Juan Gil‐Molto

Papers

Di-2-pyridylmethylamine-Based Palladium Complexes as New Catalysts for Heck, Suzuki, and Sonogashira Reactions in Organic and Aqueous Solvents†

Palladium(II) Chloride and a (Dipyridin‐2‐ylmethyl)amine‐Derived Palladium(II) Chloride Complex as Highly Efficient Catalysts for the Synthesis of Alkynes in Water or in NMP and of Diynes in the Absence of Reoxidant

Direct Coupling Reactions of Alkynylsilanes Catalyzed by Palladium(II) Chloride and a Di(2-pyridyl)methylamine-Derived Palladium(II) Chloride Complex in Water and in NMP

Palladium(II) Chloride and a (Dipyridin-2-ylmethyl)amine-Derived Palladium(II) Chloride Complex as Highly Efficient Catalysts for the Synthesis of Alkynes in Water or in NMP and of Diynes in the Absence of Reoxidant.

Direct Coupling Reactions of Alkynylsilanes Catalyzed by Palladium(II) Chloride and a Di(2‐pyridyl)methylamine‐Derived Palladium(II) Chloride Complex in Water and in NMP.