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The search for more sustainable solutions for plastics production, moving away from petrochemical feedstocks as today's major raw material basis, is a research area of increasing interest. This task goes far beyond the issue of designing greener polymers and their related monomers as tailor-made plastics require, besides the polymer itself, further components. These additives also need to be switched from typically fossil-based to bio-renewable raw materials. One of such necessary components for many applications are plasticizers, and a major application of them is related to polyvinyl chloride (PVC) as one of the leading polymers with a wide range of applications. Typically today‘s plasticizers are based on fossil feedstocks, and some of them such as specific ortho-phthalates as the most important product class of plasticizers are now subject to restrictions and authorization by the EU's REACH legislation due to their toxicological profile. In this contribution, we report the synthesis and technical evaluation of alternative, novel bicyclic plasticizer candidates, which are fully accessible from renewable feedstocks. In detail, these new plasticizer target molecules are based on the use of the furan-derivative 2-methylfuran, maleic anhydride and 2-ethylhexanol as bio-based starting materials. The synthetic concept consists of an initial Diels-Alder reaction with 2-methylfuran and a subsequent hydrogenation and optional esterification step. The applied reactions are well-known as economic and sustainable technologies. Thus, not only the starting materials (being of bio-based origin) but also the selected reaction technologies for the syntheses of the target molecules are sustainable. Furthermore, a range of performance tests enabled an insight into structure-performance relationships and revealed promising plasticizing properties of this new bio-based plasticizer generation with, e. g., an attractive solution temperature fulfilling the criterium for a “fast fuser” as well as good compatibility with PVC. Bundesministerium für Bildung und Forschung (BMBF)

A current challenge in catalysis is the development of methodologies for the production of bulk chemicals needed at levels of tens and hundreds of thousands of tons per year with the requirement to be produced at very low costs often being in the single-digit US dollar range. At the same time, such methodologies should address challenges raised by current manufacturing processes. Within this research area, a cyanide-free approach toward aliphatic nitriles used as industrial chemicals was developed starting from readily accessible n-alkenes as starting materials available in bulk quantities. This chemoenzymatic process concept is exemplified for the synthesis of nonanenitrile (as an n-/iso-mixture) and runs in water at low to moderate temperatures without the need for any types of cyanide sources. The process is based on a combination of a metal-catalyzed hydroformylation as the world-leading production technology for alkyl aldehydes with an emerging enzyme technology, namely, the recently developed transformation of aldoximes into nitriles through dehydration by means of aldoxime dehydratases. As a missing link, an efficient aldoxime formation with subsequent removal of remaining traces of hydroxylamine as an enzyme-deactivating component was found, which enabled the merging of these three steps, hydroformylation, aldoxime formation, and enzymatic dehydration, toward a nitrile synthesis without the need for purification of intermediates.

Aldoxime synthesis directly starting from alkenes was successfully achieved through the combination of hydroformylation and subsequent condensation of the aldehyde intermediate with aqueous hydroxylamine in a one-pot process. The metal complex Rh(acac)(CO)(2) and the water-soluble ligand sulfoxantphos were used as the catalyst system, providing high regioselectivities in the initial hydroformylation. A mixture of water and 1-butanol was used as an environmentally benign solvent system, ensuring sufficient contact of the aqueous catalyst phase and the organic substrate phase. The reaction conditions were systematically optimised by Design of Experiments (DoE) using 1-octene as a model substrate. A yield of 85% of the desired linear, terminal aldoxime ((E/Z)-nonanal oxime) at 95% regioselectivity was achieved. Other terminal alkenes were also converted successfully under the optimised conditions to the corresponding linear aldoximes, including renewable substrates. Differences of the reaction rate have been investigated by recording the gas consumption, whereby turnover frequencies (TOFs) >2000 h(-1) were observed for 4-vinylcyclohexene and styrene, respectively. The high potential of aldoximes as platform intermediates was shown by their subsequent transformation into the corresponding linear nitriles using aldoxime dehydratases as biocatalysts. The overall reaction sequence thus allows for a straightforward synthesis of linear nitriles from alkenes with water being the only by-product, which formally represents an anti-Markovnikov hydrocyanation of readily available 1-alkenes.

As a very durable material, soft polyvinyl chloride (PVC) is used for many applications in the field of consumer products. To enable the desired properties, for example for medical devices, the addition of plasticizers is required. For this purpose, mostly dialkyl phthalates are used being produced on a multi-million tons scale annually. Since some of these are associated with human health effects, there is an increasing demand for the search of alternatives. Besides reduced toxicity while maintaining excellent performance features, an economic access as well as biorenewable starting materials are further criteria, which should be ideally fulfilled by such a new plasticizer generation. Targeting these demands and in contrast to most available substitutes being based on petrochemical feedstock, we developed a synthetic route starting from bio-renewable platform chemicals. In detail, a Diels-Alder reaction of 2-methylfuran and maleic anhydride and subsequent dehydration leads to three phthalate derivatives with different alcohol components bearing a methyl group at the aromatic ring. As a representative substance, di(2-ethylhexyl) 3-methylphthalate was chosen for performance tests, and this new bio-based alternative offers properties similar to known plasticizers in such initial studies.

A continuous-flow dynamic kinetic resolution of racemic secondary alcohols was carried out using a single column reactor packed with a mixture of immobilized lipase and an immobilized oxovanadium species, VMPS4. As a result, optically pure esters were produced in 88-92 % yields. Problems encountered in this study were overcome by using fillers that efficiently maintained the initial distribution of the catalysts in the reactor and by using a packing method in which the mixing ratio of the two catalysts was varied in a stepwise fashion. The flow process led to an increased turnover number of each catalyst compared to those of batch reactions.