Lysinol: a renewably resourced alternative to petrochemical polyamines and aminoalcohols†
This paper reports the preparation of lysinol (2,6-diamino-1-hexanol) by the hydrogenation of lysine and an example of its use as a replacement for petrochemical-derived amines. Lysine is presently manufactured by fermentation of sugars and other carbon sources at scale exceeding 109 kg per year. Therefore, lysinol is potentially a renewable, platform aminoalcohol of previously unrecognized potential. Lysine hydrogenation proceeds under relatively modest conditions with Ru/C catalyst in water (100–150 °C, 48–70 bar, pH 1.5–2) to give lysinol in good yield (100% conversion, >90% selectivity; 50–70% isolated yield after purification by distillation). The impact of the various reaction parameters on conversion and selectivity are presented and discussed. Lysine hydrogenation at higher temperatures provides a pathway to piperidines and other products via further reduction and elimination of lysinol. The feasibility of lysinol synthesis from commodity, animal feed-grade lysine sources is presented as well. An example of the potential utility of lysinol is demonstrated by its use as a diamine curing agent with a standard epoxy resin. The properties of the resulting thermoset are contrasted with that obtained with a typical petrochemical amine used in this application (diethylenetriamine, DETA).