Arno Behr

Improved utilisation of renewable resources: New important derivatives of glycerol

Although glycerol has been a well-known renewable chemical for centuries, its commercial relevance has increased considerably in the last few years because of its rising inevitable formation as a by-product of biodiesel production. The present review gives a broad overview on the chemistry of glycerol starting from the classic esters and oligomers to new products like glycerol carbonate, telomers, branched alkyl ethers, propanediols and epoxides. In particular, the novel possibilities to control the numerous addition, reduction and oxidation reactions via heterogeneous, homogeneous and biocatalysis will be presented. A benchmark will be given to determine the products which will have the best chances of entering the market and which processes are currently most developed.

Towards resource efficient chemistry: tandem reactions with renewables

In an economically expanding world new sustainable concepts have to be developed in order to overcome growing problems of resource availability. Merging different “Green principles” is a promising concept in this respect, e.g. the combination of tandem reactions and renewables. This review summarizes the trends in this field and demonstrates advantages and future demands. Four reactions, namely metathesis, hydroformylation, defunctionalisation and isomerisation, have been identified for transforming renewables in tandem reactions. Every reaction yields a reactive intermediate or secures a tailored selectivity in order to use the natural molecular structure of renewables.

Telomerization: Advances and Applications of a Versatile Reaction

The transition-metal catalyzed telomerization of 1,3-dienes with different nucleophiles leads to the synthesis of numerous products, such as sugar ethers, substituted lactones, or terpene derivatives, which can be applied in the cosmetic and pharmaceutical industry as well as in polymers and flavors. The reaction can be controlled by the choice of the catalytic system, the feedstock, and the reaction conditions. Since telomerization was developed in 1967, there have been many efforts to utilize this reaction. Herein we give an overview of the versatility of telomerization based on examples from research and industry, particular emphasis is placed on catalyst and process development as well as mechanistic aspects.

Use of carbon dioxide in chemical syntheses via a lactone intermediate

Carbon dioxide (CO2) is available in almost infinite amounts in our atmosphere and oceans, but its utilisation as feedstock for the chemical industry is often prevented by its thermodynamic stability. Only a few processes based on CO2 as a raw material were realised in a technical scale so far, like the production of urea, methanol or salicylic acid. In the present review mainly catalytic reactions of a lactone platform chemical are described whose production is based on CO2 as a feedstock. The synthesis of this highly functionalised 1 was already invented in the 1970s and was optimised into miniplant‑scale in the meantime. Based on its different functional groups numerous reactions can be carried out starting from this molecule leading to versatile, interesting products: Acids, alcohols or diols as well as aldehydes, amino acids or amines are formed in high yields. Furthermore, esters, silanes or even polymers are obtained using the δ‑lactone as a building block. Thus, by applying efficient catalytic systems which lead to high selectivities a new approach for the utilisation of CO2 as a reasonable feedstock for chemical reactions is described.

Telomerization of Butadiene with Glycerol: Reaction Control through Process Engineering, Solvents, and Additives

Owing to the large amount of glycerol that is formed as a by-product during biodiesel production, there have been great efforts to develop new reactions and processes based on glycerol as a renewable feedstock. One example is the telomerization of butadiene with glycerol which provides an atom-economic route to amphiphilic molecules. The reaction is catalyzed by homogeneous palladium catalysts which necessitates efficient catalyst recycling. By employing an aqueous biphasic system, an increased selectivity towards the desired mono-ethers was observed in the telomerization reaction. The performance of the reaction and separation and recycling of the catalyst were optimized by the addition of organic solvents as well as cyclodextrins. By adding cyclodextrins, the conversion of glycerol could be increased and the leaching of palladium could be reduced. Leaching of palladium into the organic phase could be lowered also by using 2-octanol or 2-propanol as additional solvents. Furthermore, the catalyst system could be stabilized by adding nitriles or phosphonium salts, and radical polymerization, which leads to fouling, could be inhibited successfully.

Palladium-catalyzed telomerization of butadiene with ethylene glycol in liquid single phase and biphasic systems: control of selectivity and catalyst recycling

Abstract The palladium-catalyzed telomerization of 1,3-butadiene (Bu) with ethylene gylcol (EG) has been studied in liquid single phase and aqueous biphasic systems. All important parameters have been examined, including temperature, catalyst system, catalyst concentration, Bu/EG ratio, P/Pd ratio, solvent and reaction time. In homogeneous phase mixtures of 2-(2,7-octadienyloxy)ethanol ( 1a ) and 2-(1-ethenyl-5-hexenyloxy)ethanol ( 1b ) were formed in yields up to 60%, but also ditelomers ( 2 ) and butadiene dimers ( 3 ) were produced in significant amounts. In aqueous biphasic systems, however, using a palladium catalyst with the triphenylphosphinetrisulfonate (TPPTS) ligand, the monotelomers 1a and 1b were obtained in 80% yield with more than 95% selectivity. A mechanism is proposed explaining the observed differences in selectivity. The aqueous catalyst phase could be recycled six times resulting only in a slight decrease of activity. The products 1a and 1b were hydrogenated in quantitative yield to the corresponding saturated compounds 2-octyloxyethanol ( 6a ) and 2-(1-ethyl-hexyloxy)ethanol ( 6b ) using a Pd/Al 2 O 3 catalyst under mild conditions. The products can be used for a variety of applications like plasticizers, cosmetics and solvents.

Influences of olefinic and diketonate ligands in the nickel-catalyzed linear oligomerization of 1-butene

Abstract Cyclooctenyl nickel complexes which contain cyclic 1,2-diketones, α-acyl cycloalkanones, or substituted 1,3-propanediones as chelating ligands have been shown to be active catalysts for the homogeneous linear oligomerization of 1-butene. An almost linear correlation between acidity and activity of the ligands was observed. Three new η 1 ,η 2 -cyclooctenyl diketonate complexes, containing dibenzoylmethane, furoylbenzoylmethane and di-( para -fluorobenzoyl)methane, respectively, as the chelating ligand were prepared, and shown to be active catalysts. Nickel diketonate complexes containing η 3 -cyclooctenyl, η 3 -allyl, and η 3 -butenyl ligands confirmed that η 3 -allyl species are less active than their η 1 ,η 2 -analogues. This may be attributed to the ease of nickel hydride formation in η 1 ,η 2 -olefin complexes.

Hydroaminomethylation of fatty acids with primary and secondary amines — A new route to interesting surfactant substrates

The rhodium catalysed hydroaminomethylation of the unsaturated fatty acid derivatives oleic acid ethyl ester (1) and oleyl alcohol (2) with the primary amines hexylamine (3), benzylamine (4), aspartic acid diethyl ester (5) and valinol (6), and with the secondary amine morpholine (7), respectively, proceeds with good to excellent yields. Using primary amines the structure of the reaction products depends on the stoichiometry of the reactants. Performing the reaction of (1) with (3) with an excess of the amine compound the corresponding secondary amine (9) (1:1-adduct) was observed. Working with a 2-fold excess of (1) the tertiary amine (16) (2:1-adduct) was the main product.

Selection process of new solvents in temperature-dependent multi-component solvent systems and its application in isomerising hydroformylation

The rhodium–BIPHEPHOS catalysed hydroformylation of trans-4-octene yields n-nonanal at high selectivity under mild reaction conditions. In this contribution a new method for an efficient product and catalyst separation in hydroformylation reactions is presented. By application of a temperature-dependent multi-component solvent (TMS) system, classical extraction process steps can be omitted and catalyst leaching reduced. The Hansen solubility parameter concept of solvent selection is presented to determine in general TMS systems for homogeneous catalysed reactions.

Platinum-Catalysed Hydrosilylation of Unsaturated Fatty Acid Esters

Different Pt(IV), Pt(II) and Pt(0) catalysts were screened for the hydrosilylation of fatty acid esters containing terminal as well as internal double bonds. The reaction of terminally unsaturated fatty acid esters proceeded smoothly with short reaction times for nearly all examined catalysts, whereas Pt(IV) species and Pt(II) or Pt(0) species with labile ligands were sufficiently active in the reaction of internally unsaturated compounds. For methyl linoleate, a conjugation of the two internal double bonds before the hydrosilylation was observed. The reaction was carried out in substance as well as in solvent systems permitting a catalyst recycling and reuse. In these systems, however, hydrogenation and double bond isomerisation were found as side reactions.