Cédric Fischmeister

Phosphole‐Containing π‐Conjugated Systems: From Model Molecules to Polymer Films on Electrodes

Two series of 2,5-dipyridyl- and 2,5-dithienylphosphole derivatives containing sigma3- or sigma4-P atoms were prepared, and their optical (UV/Vis absorption, fluorescence spectra) and electrochemical properties were systematically evaluated. These physical properties depend mainly on the natures of the 2,5-substituents and of the phosphorus moiety, and they revealed that these compounds contain extended pi-conjugated systems. Structure-property relationships were established on the basis of these experimental data and ab initio calculations on the parent molecules. The limited aromatic character and low-lying LUMO of the phosphole ring appear to be crucial for achieving a highly delocalised pi system. Electrooxidation of 2,5-dithienylphosphole derivatives affords electroactive films with low optical band gaps. As observed for the corresponding monomers, the optical and electrochemical properties of the polymers can be varied over a wide range by modifying the nature of the phosphorus moiety.

Greener solvents for ruthenium and palladium-catalysed aromatic C–H bond functionalisation

The formation of carbon-carbon bonds by transition metal-catalysed direct functionalisation of C–H bonds has recently emerged as a greener alternative to traditional cross-coupling reactions. Despite tremendous improvement of the catalytic efficiency allowing reactions under milder conditions or lower catalyst loadings, this type of transformation still suffers from a major limitation with regards to green chemistry concerning the reaction media since the preferred solvents for these transformations are the undesirable and toxic, high boiling point, polar, aprotic, N-methylpyrrolidinone (NMP), dimethylformamide (DMF) or dimethylacetamide (DMAc). Recently, efforts have been made to perform these reactions in greener or more environmentally acceptable media. This review summarises the contributions made in this direction during the past few years.

Direct amination of aryl halides with ammonia

The traditional homogeneous access to aromatic amine derivatives is a nucleophilic aromatic substitution of the corresponding aryl halides. The halogen atom is usually relatively inert to amination reaction unless it is activated by the presence of electron withdrawing groups. Consequently, there has been particular emphasis over the past decade on the synthesis of metal complexes that are active catalysts for the preparation of aromatic amines. This tutorial review focuses on the use of metal-based complexes for the direct amination of aryl halides with ammonia.

Renewable materials as precursors of linear nitrile-acid derivatives via cross-metathesis of fatty esters and acids with acrylonitrile and fumaronitrile

The cross-metathesis of fatty acids and esters, as renewable raw materials, with acrylonitrile and fumaronitrile is presented. The cross-metathesis reactions of both terminal and internal double bond containing compounds were performed using a ruthenium catalyst and led to bifunctional nitrile-esters or nitrile-acids with high conversions. The tandem ruthenium catalysed cross-metathesis and hydrogenation provide precursors of aminoacid monomers for the production of polyamides from renewable resources.

First ring-opening metathesis polymerization in an ionic liquid. Efficient recycling of a catalyst generated from a cationic ruthenium allenylidene complex

Ring-opening metathesis polymerization (ROMP) of norbornene was carried out in a biphasic medium consisting of the ionic liquid [bdmim][PF6] and toluene with a cationic ruthenium allenylidene precatalyst. The ionic liquid contained the ruthenium allenylidene complex and toluene dissolved the formed polymer. Both the catalyst and the ionic liquid were reused several times and led to very good polymer yields.

Diethyl carbonate as a solvent for ruthenium catalysed C–H bond functionalisation

The ruthenium catalysed direct functionalisation of arene C–H bonds by aryl halides is reported. Reactions were performed in diethyl carbonate (DEC) instead of N-methylpyrrolidone (NMP), the solvent of choice used in most ruthenium catalysed C–H bond transformations. The use of diethyl carbonate facilitates the workup procedure thus reducing the amount of waste water. The slight loss of activity due to the use of diethyl carbonate is counterbalanced by the improvement of the catalyst efficiency achieved by a judicious choice of additives. Several arenes containing an N-heterocycle as a directing group have been diarylated.

Ruthenium–alkylidene catalysed cross-metathesis of fatty acid derivatives with acrylonitrile and methyl acrylate: a key step toward long-chain bifunctional and amino acid compounds

The ruthenium catalysed cross-metathesis of fatty-esters arising from plant oils with acrylonitrile is presented. The resulting linear nitrile ester products have potential as new intermediates for polyamides synthesis. A series of commercially available catalysts are able to promote the transformation of methyl 10-undecenoate 1, dimethyl octadec-9-en-1,18-dioate 5 and methyl ricinoleate 9 with acrylonitrile and a protocol based on the slow addition of catalyst allowed TONs as high as 1900 (92% yield) to be reached for cross-metathesis with acrylonitrile. These cross-metathesis conditions have been applied to methyl acrylate and TONs up to 7600 were obtained.

Synthesis and properties of chiral imidazolium ionic liquids with a (1R, 2S, 5R)-(-)-menthoxymethyl substituent

A series of 1-[(1R,2S,5R)-(−)-menthoxymethyl]-3-alkylimidazolium salts have been synthesized, producing both hydrophilic and hydrophobic chiral imidazolium ionic liquids. Their physicochemical properties, single-crystal X-ray structures, antimicrobial activities, and antielectrostatic effects were determined and these compounds have proven to represent not only potential new solvents in asymmetric synthesis, but also effective, disinfectants with antielectrostatic activity. Given the number and diversities of the possible conformations and interionic interactions, coupled with the chiral nature of the cations, it should come as no surprise that these salts exhibit ionic liquid behavior and are so difficult to crystallize.

Polyamide precursors from renewable 10-undecenenitrile and methyl acrylate via olefin cross-metathesis

The ruthenium-catalyzed cross-metathesis of the unsaturated fatty acid derivative 10-undecenenitrile 1 arising from castor oil with methyl acrylate produces a C12 nitrile ester with high turnover number. This product has potential as a new bio-sourced intermediate for the production of polyamides. This route competes favourably with the reverse cross-metathesis of methyl 10-undecenoate with acrylonitrile leading to the same C12 α,ω-amino ester 7 after hydrogenation of the carbon–carbon double bond and the nitrile functionality.

Ruthenium(II)-catalyzed selective monoarylation in water and sequential functionalisations of C–H bonds

The ruthenium(II)-phosphine catalyst RuCl2(PPh3)(p-cymene) operating water selectively leads to ortho monoarylation, with arylchlorides and heteroarylhalides, of functional arenes. Further catalytic heteroarylation with Ru(OAc)2(p-cymene) in water produces mixed bifunctional derivatives.