Nitrogen fertilizer manufacturing may be about to get a boost as synthetic organic chemists have developed a simple step for the production of nitrogen compounds. As well as potential use in making fertilizer, the simple process can also be applied in the manufacture of pesticides, pharmaceuticals, and a range of other chemical products.
The breakthrough was made at Rice University, when Zhe Zhou, a postdoctoral researcher, noticed how the chemical silyl enol ether reacted when mixed at room temperature with a nitrogen source in a common solvent (hexafluoroisopropanol). The chemist found that the ether combined with the nitrogen to mimic a chemical effect called ‘Rubottom oxidation’.
This observation led to the discovery of a more direct route for the synthetic construction of nitrogen compounds, specifically the versatile chemicals known as alpha-aminoketones. Not only did the new method save time and chemical feedstock, but it also gave higher yields. Additionally, the process’s novel approach provides a host of potential further discoveries.
“Oxygen is routinely put into the alpha position. But nitrogen, no.” Rice synthetic organic chemist László Kürti, and the study’s co-author, explains, “We are the first to show this is possible in a large number of substrates, and it's simple. It turns out that the solvent itself catalyzes the reaction.”
Alpha-aminoketones are a valuable group of molecules, useful in the production of chemical products for many different industries. As the online scientific journal Phys.org, explains, “Ketones are carbon-based compounds found in nature and important feedstocks for the chemical industry. The primary amino group (NH2) is a functional group present in many important chemical products. It contains one nitrogen atom and two hydrogen atoms. When a ketone is functionalized with a primary amino group at the alpha carbon, it forms a compound called a primary alpha-aminoketone.”
Adding that, “Zhou and co-author and postdoctoral researcher Qing-Qing Cheng refined the [original] method and subsequently tested it by making 19 aminoketones, including three synthetic amino acid precursors.”
The beauty of the new process is in its simplicity. As Zhou explains, “Before we had this process, it wasn't impossible to make these kinds of structures. It was just very complicated and took many steps.
“Our amination method promises to replace a common three-step process to make alpha-aminoketones, and the yield, comparably, is very good. In the standard process, each step cuts the yield, so a one-step process is still superior even if the yields are identical, because it takes less time and there's less risk of something going wrong.
“The last thing you want is to get eight steps from the beginning and then ruin it on the ninth because the conditions are not selective enough,” he said. “Cutting steps is always beneficial in organic synthesis.”
Rice University postdoctoral researcher Zhe Zhou at work
“These unnatural amino acids are significant for chemical design,” said Kürti, an associate professor of chemistry. “The enzymatic processes in living organisms are not going to attack them, because they don't fit in the enzymes' pockets.”
The technique has now been published in the Journal of the American Chemical Society.
Given the increasing cost of nitrogen fertilizer manufacturing, the discovery of a simplified process for the manufacture of synthetic organic nitrogen compounds could play an important role in the fertilizer industry’s future. While upscaling the method to an industrial scale required by fertilizer suppliers is a more distant plan, investors have already taken note of the process’s suitability for use in producing pharmaceuticals, while chemists are excited by the myriad of other compounds that are waiting to be discovered.
“There's a new trend toward late-stage functionalization, where companies with an existing library of compounds can take 100 of them and perform an additional step to make 100 new compounds,” notes Kürti. “So, from an intellectual property perspective, our discovery is a great gift to industry. This really is a gem of a find.”
AG CHEMI GROUP has been supplying fertilizer feedstock since 1994. It is also a global supplier of zinc oxide, potassium sulfate, potassium carbonate and other industrial ingredients.
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Photo credit: Zhe Zhou/Rice University, Jeff Fitlow/Rice University & Kukkman