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New chemical structures built on unreactive bonds

Date:
July 27, 2017
Source:
Osaka University
Summary:
Organic chemists have transformed strong carbon fluorine bonds into crowded quaternary carbon centers with cobalt catalyzed Grignard chemistry.
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Osaka University research team develops new synthetic tool for building complex carbon frameworks by reacting strong carbon-fluorine bonds Osaka, Japan -- Making complicated organic molecules is like solving a Rubik's cube. Organic chemists need to design sequences of reactions to carefully build up parts of a molecule, while maintaining the structure at other sites. Although chemists have developed many ingenious ways of performing chemical transformations, some chemical reactions remain out of reach.

At Osaka University, a team of organic chemists has now developed and enhanced a chemical reaction that allows controlled transformations of one of the toughest chemical bonds.

"We previously developed a cobalt catalyzed Grignard reaction for making hindered quaternary carbon centers. But that reaction also showed potential for modifying carbon-fluorine bonds. We tried many different additives and eventually found one that let us selectively build the same quaternary carbon-carbon bonds at carbon-fluorine sites," says first author Takanori Iwasaki.

The Grignard reaction is a classic reaction in organic chemistry, useful for building the carbon skeleton of molecules by transforming carbon-halogen bonds into carbon-carbon bonds. Fluorine is also considered to be a halogen but the carbon-fluorine bond is among the strongest known and is usually unreactive to Grignard chemistry. Performing any kind of chemical reaction at carbon-fluorine bonds is difficult without affecting the rest of the molecule.

The Osaka team enhanced their catalytic system for performing difficult Grignard chemistry at very crowded, so-called quaternary carbon atoms. By adding a carefully selected additive to this catalytic system, they boosted its ability to work selectively on carbon-fluorine bonds.

"We have shown that this reaction is a very useful tool for sequentially changing parts of a molecule with great control," says Group leader, Nobuaki Kambe. "Our control over the chemistry of carbon-fluorine bonds should enable much more synthetic freedom for building complex carbon structures."


Story Source:

Materials provided by Osaka University. Note: Content may be edited for style and length.


Journal Reference:

  1. Takanori Iwasaki, Koji Yamashita, Hitoshi Kuniyasu, Nobuaki Kambe. Co-Catalyzed Cross-Coupling Reaction of Alkyl Fluorides with Alkyl Grignard Reagents. Organic Letters, 2017; 19 (14): 3691 DOI: 10.1021/acs.orglett.7b01370

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Osaka University. "New chemical structures built on unreactive bonds." ScienceDaily. ScienceDaily, 27 July 2017. <www.sciencedaily.com/releases/2017/07/170727102920.htm>.
Osaka University. (2017, July 27). New chemical structures built on unreactive bonds. ScienceDaily. Retrieved May 27, 2024 from www.sciencedaily.com/releases/2017/07/170727102920.htm
Osaka University. "New chemical structures built on unreactive bonds." ScienceDaily. www.sciencedaily.com/releases/2017/07/170727102920.htm (accessed May 27, 2024).

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