(604z) A New “Cross Metathesis” Synthesis Route for Producing Nylon 12 and Nylon 13 Precursors from Methyl Oleate

Due to the concerns related to limited fossil resources and increasing CO₂ emissions, there is a strong interest in use of renewable resources in production of valuable synthetic materials.  Nylon 11, 12 and 13 are high-strength polymers that find use in various industrial sectors and are traditionally produced from petroleum-derived material or exotic fatty acids using reaction sequences that involve 4–6 steps. We have developed a simple two-step synthetic process for production of Nylon 12 and Nylon 13 precursors using a cross-metathesis reaction approach that allows for high carbon efficiency and mild reaction conditions. In contrast to other reported methods,, our method uses methyl oleate, an abundantly available and natural fatty acid derivative that can be obtained from most plant oils or oleaginous organisms including microalgae, as the feed material. 

Our general strategy involve cross-metathesis of methyl oleate with allyl cyanide or 4-pentenitrile, followed by hydrogenation of the unsaturation of olefin and nitrile functionalities to produce methyl esters of C12 and C13 amino acids, which are precursors for Nylon 12 and 13, respectively.

Although conceptually straightforward, both steps require significant reaction tuning in order to obtain a high level of conversion and yield.  When the cross-metathesis reactions were performed in the absence of additives, undesirable isomerization of the reagents and/or product occurred, resulting in the formation of many side-products with truncated carbon chains. We discovered that the addition of quinones, an isomerization supressor, into the reaction mixture, significantly reduced the side reaction and resulted in higher selectivity towards the desired products.  Upon screening and optimization of other reaction parameters, such as temperature, solvent, reaction time, catalyst loading, and mode of catalyst addition, we were able to achieve good to excellent yield of the desired nitrile esters from these reactions. The second hydrogenation step was conducted using the same catalyst used for metathesis reaction to improve the overall efficiency of catalyst use. 

In conclusion, our two-step approach from methyl oleate to Nylon 12 and 13 precursors represents the shortest synthesis to date.  The full details of our efforts on reaction optimization will be discussed in our poster presentation.