The fascinating story of olefin (or alkene) metathesis (eq
1) began almost five decades ago, when Anderson and
Merckling reported the first carbon-carbon double-bond
rearrangement reaction in the titanium-catalyzed polymerization of norbornene. Nine years later, Banks and Bailey reported “a new disproportionation reaction . . . in which olefins are converted to homologues of shorter and longer carbon chains...”. In 1967, Calderon and co-workers named this metal-catalyzed redistribution of carbon-carbon double bonds olefin metathesis, from the Greek word “μeτάθeση”, which means change of position. These contributions have since served as the foundation for an amazing research field, and olefin metathesis currently represents a powerful transformation in chemical synthesis, attracting a vast amount of interest both in industry and academia.

https://core.ac.uk/download/pdf/4884240.pdf

Ruthenium-based heterocyclic carbene-coordinated olefin metathesis catalysts.

Molecular separation with organic solvent nanofiltration: a critical review.

HAL is a multi-disciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L’archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d’enseignement et de recherche français ou étrangers, des laboratoires publics ou privés. Synthetic Routes to N-Heterocyclic Carbene Precursors Laure Benhamou, Edith Chardon, Guy Lavigne, Stéphane Bellemin-Laponnaz, Vincent César

Synthetic routes to N-heterocyclic carbene precursors.

Much effort has gone into the immobilization of homogeneous catalysts based on the idea that in this way the catalysts could be not only separated more easily from the product but also reused several times, thus reducing the cost of the catalyst use. So far none of these immobilized catalysts have been used by industry. In this article we critically review the use of immobilized homogeneous catalysts from the point of view of process development for the pharmaceutical and fine chemical industry. The first and foremost question that needs to be answered is: will immobilizing a homogeneous catalyst really lead to lower costs? The answer is thus far always no. This is caused mostly by the fact that homogeneous catalysts are not stable and thus there is little point in immobilizing them. The second reason is the extra added cost that is incurred in immobilizing the catalysts. Other problems are lower rates, sometimes lower selectivities and metal leaching. Three different areas are discussed. The research on immobilized metathesis catalysts is analyzed in detail; in general the immobilized catalysts do not achieve sufficient turnovers to be interesting for industrial use. Very many publications have appeared on immobilized palladium catalysts that were used for C-C bond-forming reactions, such as Suzuki, Heck or Sonoga-shira reactions. These catalysts are invariably converted to nanoparticles after the first run. Although these catalysts can be reused, there is no reason to use an expensive support based on immobilized ligands. This also does not protect the product from palladium contamination. Even more effort has gone into the immobilization of homogeneous hydrogenation catalysts. Most of these catalysts suffer from the same problems as the other immobilized catalysts: catalyst deactivation, low turnover numbers, and leaching of the metal. In addition, the heterogenization adds complexity to the system, increasing risk and prolonging process development. 1 Introduction 2 Immobilized Catalysts in Metathesis Reactions 2.1 Immobilization via the "Fixed" Ligand 2.2 Immobilization via a Pseudo-Halide Substituent 2.3 "Boomerang" Catalysts 2.4. Soluble Polymers 2.5 Miscellaneous Strategies 3 Immobilized Palladium Complexes for Heck, Suzuki, Sonogashira and Other C-C Bond-Forming Reactions 3.1 Catalysts Based on Immobilized Nitrogen Ligands 3.2 Catalysts Based on Immobilized Thiol Ligands 3.3 Catalysts Based on Immobilized Phosphine Ligands 3.4 Catalysts Based on Immobilized NHC Ligands 3.5 Catalysts Based on Immobilized Palladacycles 3.6 Immobilized Palladium Catalysts in Flow 4 Hydrogenation with Immobilized Catalysts 4.1 Case Studies of Covalently Bound Complexes 4.2 Case Studies of Ionically Bound Complexes 4.3 Case Studies of Physisorbed Complexes 5 Conclusion and Outlook

Why Does Industry Not Use Immobilized Transition Metal Complexes as Catalysts

The strong electron-donation and the steric bulk of trialkylphosphines renders them as very useful ligands for palladium-catalyzed cross coupling reactions. This critical review reports on the synthesis of two families of trialkylphosphines (diadamantylalkylphosphines, fluorenyldialkylphosphines) and the properties of the respective palladium complexes in various cross coupling reactions, which evolved as alternatives to the classical Pd/PtBu3 system. In contrast to the latter phosphine the new classes of ligands are characterized by a highly flexible ligand design, which allows the fine tuning of catalytic properties to the specific needs of certain substrates and also enables the attachment of additional tags to impart certain useful properties onto the respective phosphines (179 references).

Sterically demanding trialkylphosphines for palladium-catalyzed cross coupling reactions—alternatives to PtBu3

A mass-tagged N-mesityl imidazolinium salt with four additional -CH(2)NCy(2) substituents was synthesized, leading to a molecular mass of nearly 1100 g mol(-1) in the corresponding carbene ligand. This mass-tagged ligand was used to generate the respective Grubbs II and Grubbs-Hoveyda type complexes. The catalytic activity of the latter complex was tested in several olefin metathesis reactions and found to be slightly superior to that of the related N-mesityl based complex. In batchwise solvent resistant nanofiltration experiments the ruthenium complex dissolved in toluene and following a metathesis reactions was efficiently retained (>99.8 %) by a single nanofiltration; the permeate contained less than 4 ppm of Ru. Equally efficient catalyst retention was observed in a membrane reactor utilized for the continuous synthesis of a RCM product.

Batchwise and continuous organophilic nanofiltration of Grubbs-type olefin metathesis catalysts.

Membranen: Grundlagen, Verfahren und industrielle Anwendungen

Solvent-Resistant Nanofiltration of Enlarged (NHC)Pd(allyl)Cl Complexes for Cross-Coupling Reactions

The invention relates to a composite membrane with a separation-active membrane layer and a supporting membrane, a process for the production of the same, and a process for using the same. The composite membrane according to the invention is distinguished by the fact that the separation-active membrane layer comprises a polymer hardened by electromagnetic radiation with a wavelength that is less than 800 nm and/or by electron beams. The process according to the invention is distinguished by the fact that a layer of a solution of a polymer that can be hardened by electromagnetic radiation with a wavelength that is less than 800 nm and/or by electron beams and an initiator substance is applied to a supporting membrane and subsequently is hardened by electromagnetic radiation and/or by electron beams. The use according to the invention serves to retain low-molecular substances from organic solutions.

Composite membrane and process

An increasing number of hybrid processes consisting of conventional unit operations and vapour permeation modules have been suggested in recent years. To facilitate accurate process design, rigorous models of this novel membrane process are essential. By comparing experimental results obtained from a pilot plant, it was shown that simply solving the material balances and assuming constant permeances is not sufficient to predict the operating behaviour of a vapour permeation module. In order to reflect the experimental results it was necessary to consider the concentration, temperature and pressure dependency of the permeation process through the membrane as well as the mass transfer restriction in the boundary layer on the feed side. The introduced model is capable of taking account of these effects and predicts the experimental results satisfactorily. The model was written using the commercial, equation-oriented process simulator Aspen Custom Modeler and hence can easily be integrated with commercial process simulation packages.

Improved simulation of a vapour permeation module

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