Guido Walther

α,ω-Functionalized C19 Monomers

With the increasing efforts to substitute fossil resources by renewable ones, there is a strong demand for the establishment of both new basic chemicals and innovative synthesis methods. Meeting the high degree of purity needed for monomers that are used for polymer synthesis is challenging. Intelligent processing methods are necessary because available feedstocks often are mixtures of different components. Linear molecules are favored for the synthesis of high-grade polymers such as polyamides or polyesters, but applications of monomers with chain lengths beyond 13 carbons are scarce. Monoenic fatty acid derivatives might comprise a well-suited raw material base because of their preformed linear structure. The isomerization of the internal double bond to the end of the chain, which is thermodynamically unfavorable, and further selective reaction at this position to a,w-functionalized monomers seems to be the bottle neck. Only a few successful ideas have been developed so far. Behr and co-workers obtained only 36 % of the linear product in the hydroformylation of methyl oleate. A more convincing concept was presented by Cole-Hamilton and co-workers. The authors reported a highly selective isomerizing methoxycarbonylation of methyl oleate to dimethyl 1,19 nonadecanedioate. In the presence of CH3SO3H and a sterically strongly hindered Pd bisphosphine catalyst the double bond was shifted initially to the terminal position in the chain. This reaction step was followed by the addition of CO and the insertion of a methoxy group, which proceeded exclusively at the C18 carbon for sterical reasons. Mecking et al. used this methoxycarbonylation recently for the synthesis of new polyester types. In this contribution, a more global approach is presented, involving i) catalytic reactions of high selectivity ; and ii) the use of a high-oleic sunflower oil (HOSO) as a vegetable oil (1), instead of fatty esters, in a simplified one-pot procedure (Scheme 1). Such processing may be advantageous for technical applications. Thus, the 1,19-diester 2 is utilized as a platform chemical for 1,19-building blocks, leading to novel polymers. During the last years, intensive studies on the methoxycarbonylation of lower olefins and of unsaturated carboxylic acids and esters have been published in the literature. 3, 5] According to our investigations, the formerly used catalytic system Pd/ bis(di-tert-butylphosphinomethyl)-benzene/CH3SO3H [2] is surprisingly capable of a three-stage reaction in one batch. Consequently, 1 was converted directly into 2 via a parallel and/or subsequent sequence of transesterification/isomerization, and methoxycarbonylation. The highly selective reaction towards 2 was neither affected by the formation of glycerol nor by minor components in the technical grade oil 1, such as free fatty acids (approx. 0.1 %) or unsaponifiables (approx. 1.5 % lecithin, sterols). Moreover, an up-scaling of the reaction over several orders of magnitude was possible without any significant loss in yield and selectivity. The reaction conditions were optimized on microliter scale (0.3 mL 1) with variation of the catalyst concentration, the volumetric ratio of MeOH to 1, and the partial pressure of CO. The one-pot reaction proceeded well over wide ranges of these parameters (Table 1). The highest yield of 2 (97 %) was achieved in run 3a. In presence of half the amount of catalyst, the product yield and selectivity did not significantly decrease (cf. run 1b and run 3e). The catalyst revealed a limited stability under reaction conditions. With proceeding reaction, Pd was precipitated in a significant amount. The observed decomposition of the Pd bisphosphine complex probably resulted from the protonation of phosphine functions by methanesulfonic acid, followed by reduction of Pd by MeOH. The methoxycarScheme 1. Reaction scheme of a novel synthesis concept to obtain a,wfunctionalized C19 monomers via 1,19-diester 2 from high-oleic sunflower oil (1; besides oleic acid radicals, 1 does also contain other fatty acid radicals to a minor degree).

High-performance polymers from nature: catalytic routes and processes for industry.

It is difficult to imagine life today without polymers. However, most chemicals are almost exclusively synthesized from petroleum. With diminishing oil reserves, establishing an industrial process to transform renewables into high-value chemicals may be more challenging than running a car without gasoline. This is due to the difficulty in setting up processes that are novel, profitable, and environmentally benign at the same time. Additionally, the quest for sustainability of renewable resources should be based on incorporating ethical considerations in the development of plans that utilize feedstocks intended for human nutrition and health. Thus, it is important to use bio-energy containing renewable resources in the most efficient way. This Concept goes beyond the synthesis of monomers and provides insights for establishing an industrial process that transforms renewable resources into high-value chemicals, and it describes careful investigations that are of paramount importance, including evaluations from an economical and an ecological perspective. The synthesis of monomers suitable for polymer production from renewable resources would ideally be accompanied by a reduction in CO2 emission and waste, through the complete molecular utilization of the feedstock. This Concept advocates the drop-in strategy, and is guided by the example of catalytically synthesized dimethyl 1,19-nonadecanedioate and its α,ω-functionalized derivatives. With respect to the Twelve Principles of Green Chemistry, this Concept describes a technological leap forward for a sustainable green chemical industry.