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Development of a new method of synthesizing dialkyl ethers using three catalysts that hydroxylate alkenes

Three strikes and acid is out

Precise control of protons and electrons by photoredox/cobalt/Brønsted acid catalysis yields valuable dialkyl ethers from readily available alcohols and alkenes without strong acids. Credit: KyotoU/Hirohisa Ohmiya

Just when we thought that alkenes could only react with alcohol to yield ethers in the presence of strong acids, hydroalkoxylation may not be quite what we expected. Organic Chemistry 101 will never be the same again, but the pharmaceutical industry may see the light.

Researchers from Kyoto University have announced the development of a new method to synthesize dialkyl ethers. Rather than using conventional methods with strong acids — which pose practical challenges, such as using acid-sensitive functional groups — the team has devised a protocol using three catalysts that hydroxylate alkenes quickly and cheaply.

This triple catalysis consists of cobalt, organic photoredox and weak Brønsted acid catalysts.

“Our discovery allows us to synthesize pharmaceutically relevant and highly functional dialkyl ether backbones in just one quick step, using relatively inexpensive and accessible raw materials,” explains lead author Hirohisa Ohmiya.

The three catalysts allow the precise control of electrons and protons to convert unactivated alkenes to the corresponding reactive carbocation equivalents in ethers under mild reaction conditions.

As a bonus, this catalysis has been shown to be able to freely utilize internal alkene partners other than terminal ones, enabling secondary and tertiary alkylation of alcohol reactants.

The author adds that they were “also impressed that the valence of cobalt can fluctuate during the triple catalytic cycle to achieve valence-dependent functions.”

“Our three catalysts perform their independent functions in a single flask to efficiently and economically create value-added molecules, potentially accelerating new drug discovery.”

The research is published in the Journal of the American Chemical Society.

Light as an aid for the synthesis of complex molecules

More information:
Masanari Nakagawa et al, A Triple Photoredox/Cobalt/Brønsted Acid Catalysis Enabling Markovnikov Hydroalkoxylation of Unactivated Alkenes, Journal of the American Chemical Society (2022). DOI: 10.1021/jacs.2c00527

Provided by Kyoto University

Quote: Development of a New Method for Synthesizing Dialkyl Ethers Using Three Catalysts that Hydroxylate Alkenes (2022, Aug 4), retrieved Aug 4, 2022 from https://phys.org/news/2022-08-method-dialkyl- ethers-catalysts-hydroxylate .html

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