Synthesis of Bifunctional Molecules for the Production of Polymers Based on Unsaturated Fatty Acids as Bioderived Raw Materials

Currently, investigations of polymer-building blocks made from biorenewable feedstocks such as, for example, fatty acids, are of high interest for the chemical industry. An alternative synthesis of nitrile-substituted aliphatic carboxylic acids as precursors for ω-amino acids, which are useful to produce polymers, was investigated starting from biorenewable fatty acids. By hydroformylation of unsaturated fatty acids or unsaturated acids being accessible from unsaturated fatty acids by cross-metathesis reactions, aldehydes are formed. In this work, the hydroformylation of such unsaturated acids led to the formation of the corresponding aldehydes, which were afterwards converted with hydroxylamine to aldoximes. Subsequent dehydration by an aldoxime dehydratase as a biocatalyst or by CuII acetate led to the desired nitriles. Within this work, C7-, C9- and C11-carboxylic acids with a terminal nitrile functionality as well as a branched nitrile-functionalized stearate derivative were synthesized by means of this approach. As these nitriles serve as precursors for amino acids being suitable for polymerization, this work represents an alternative synthetic access to polyamide precursors, which starts directly from unsaturated fatty acids as biorenewable resources and avoids harsh reaction conditions as well as and by-product formation.

Reaction of H2 with mitochondria-relevant metabolites using a multifunctional molecular catalyst

The Krebs cycle is the fuel/energy source for cellular activity and therefore of paramount importance for oxygen-based life. The cycle occurs in the mitochondrial matrix, where it produces and transfers electrons to generate energy-rich NADH and FADH2, as well as C4-, C5-, and C6-polycarboxylic acids as energy-poor metabolites. These metabolites are biorenewable resources that represent potential sustainable carbon feedstocks, provided that carbon-hydrogen bonds are restored to these molecules. In the present study, these polycarboxylic acids and other mitochondria-relevant metabolites underwent dehydration (alcohol-to-olefin and/or dehydrative cyclization) and reduction (hydrogenation and hydrogenolysis) to diols or triols upon reaction with H2, catalyzed by sterically confined iridium–bipyridyl complexes. The investigation of these single–metal site catalysts provides valuable molecular insights into the development of molecular technologies for the reduction and dehydration of highly functionalized carbon resources.

Lignin — a promising biomass resource

Lignin, the second most abundant component in plants, is a class of complex aromatic polymer. Industrial lignin is a major byproduct of pulp and paper production and biorefineries, with more than 50 megatons generated annually. However, more than 98% of industrial lignin is either burned as fuel or discharged as wastewater, causing serious environmental pollution. From a sustainable feedstock perspective, finding additional high-volume and high-value applications for lignin is an extremely important and long-term pursued objective. Thus, lignin resources deserve to be further exploited as biorenewable raw materials for energy-saving and lowcarbon polymer production. Inspired by the natural three-dimensional structure, excellent ultraviolet-blocking and antioxidant properties of lignins, the authors have focused their research on lignin-based biorenewable resources. This review summarizes research achievements of the recent decade. Progress has been made in several aspects, such as nonionic and amphoteric lignin-based surfactants, lignin-based functional materials, lignin-based photoelectric materials, lignin-based resins and polymer composites, and catalytic depolymerization of lignin.