Light broaden the scope of alkene synthesis

Chemists from the National University of Singapore (NUS) have developed a straightforward method to convert common chemicals like carboxylic acids, alcohols, and alkanes directly into valuable alkenes.

Alkenes play a crucial role in producing everyday products such as plastics, synthetic rubber, and fine chemicals, making them indispensable in modern chemistry and industry. Despite significant advances in alkene production, a simple and flexible way to transform a wide variety of starting materials into alkenes has remained a major challenge. This difficulty arises as existing methods for olefin synthesis are limited using aldehydes/ketones or alkenes as the starting materials.

Recently, Associate Professor WU Jie and his research group from the Department of Chemistry at NUS, together with Professor ZHAO Yu, also from the same department, introduced a groundbreaking solution. This work was conducted in collaboration with Professor MA Jun-an from Tianjin University, China. Their new method combines two known chemical reactions—photocatalytic radical addition and Norrish type II reaction—into a single, seamless process powered by light. The researchers used an easily accessible and reusable chemical called vinyl ketone as the “olefination reagent” to help create alkenes. By fine-tuning the reaction parameters of the vinyl ketone, they were able to enhance the reaction while minimising unwanted side reactions.

These findings were published in the journal Nature Chemistry.

This versatile method simplifies the production of valuable alkenes from abundant feedstock chemicals including carboxylic acids, alcohols, and alkanes, which were previously difficult or impossible to create. Its uniqueness lies in its robust one-pot operation, the wide range of accessible starting materials, and its ability to simplify the synthesis of complex bioactive molecules. Moreover, late-stage on-demand olefination of multifunctional molecules can be achieved through selective radical generation from acids, alcohols or alkanes. This protocol presents a complementary approach to traditional olefination methods, making it a highly valuable addition to the research toolkit for alkene synthesis.

Prof Wu said, ” As detailed in the research paper, this method provides an easy way to create useful alkenes from many different starting materials. In the future, we plan to extend this method to work with even more types of feedstock chemicals and to explore the control of alkene geometry. We believe our work will become a valuable tool for research in the pharmaceutical and agricultural fields.”

Schematic showing the development of an integrated photochemical strategy that introduce alkene moieties from a vast collection of diverse substrates. It involves two key steps, the radical addition and Norrish type II reaction. [Credit: Nature Chemistry]

Reference

Zeng H; Ying RZ; Zhao Y*; Ma JA*; Wu J*, “Modular alkene synthesis from carboxylic acids, alcohols, and alkanes via integrated photocatalysis” Nature Chemistry, DOI: 10.1038/s41557-024-01642-6 Published: 2024.