Ultra Long-chain α,ω-difunctional building blocks represent an interesting class of substrates and are often found in nature as structure-bearing elements. For instance, they occur as ceramide – a major component of the stratum corneum of the epidermis layer of the human skin, and they are part of the cellular walls of several algae species (algaenans) but also of plants (cutin and suberin). Further, such chain lengths correspond to the typical lamella thickness of polymer crystals, rendering them relevant for convenient access to nanocrystals and to high-melting polymers. The preparation of long-chain α,ω-difunctional building blocks is possible by various approaches to date. However, conventional routes via traditional organic synthesis require elaborate multi-step reactions and involve stoichiometric side products. A more straightforward approach is the utilization of fatty acids from plant oils as they inherently provide a long aliphatic methylene sequence. A major drawback of most state-of-the art techniques though is that the maximum chain length accessible is in the same range as the fatty acid used. We report a novel approach for the chain-length multiplication of monounsaturated fatty acids by a combination of two catalytic transformations, namely olefin metathesis and double-bond isomerization. With this unique process, ultra long-chain α,ω-difunctional building blocks with a doubled methylene sequence are obtained. Starting from readily available oleic acid (18:1) and erucic acid (22:1) this translates to the formation of C32 or C48 building blocks. As a possible application of such ultra long-chain compounds the preparation of high-melting polyesters (up to Tm = 120 °C) is reported. Furthermore such well-crystallizable compounds offer themselves for the preparation of thermoplastic elastomers or polymer nanocrystals.

Chain multiplication of fatty acids

253rd National Meeting (2017)

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