Hypofluorous acid-acetonitrile complex

Universite Laval, Quebec City, Quebec, Canada 

InChl = lS/C2H3N.FHO/cl-2-3 l-2/hlH3 2H InChIKey = MHXSJBXDLWNIAN-UHFFFAOYSA-N 

Epoxidations. The reagent is able to epoxidize practically any type of olefin (eq 2) including very deactivated ones which cannot be directly epoxidized by any other method (eqs 3 and 4).  

Handling, Storage, and Precautions while HOF is a very unstable substance and of little use in synthetic chemistry, its acetonitrile complex is much more stable. Nevertheless, it has to be prepared in situ and for all practical purposes reacted soon after its formation. The concentration of the reagent is determined iodometrically (HOF+2KI l2+KF+KOH). The reagent may be toxic and should be treated accordingly. Still, since it is an heavy metal-free agent, and its only side product is aqueous 

Since it is a very powerful oxygen transfer agent, short reaction times and low temperatures are sufficient for most epoxidations. As a result, sensitive substrates such as polyaromatics could also be epoxidized with much higher yield compared to other routes. Thus, for example, pyrene was allowed to react with HOF MeCN for 5 s at —15 °C, forming pyrene-4,5-oxide in 80% yield (eq 5). Unlike other epoxidation reagents, HOF MeCN was also able to epoxidize unsaturated free carboxylic acids in excellent yields (eq 6).  

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A terminal 1,13 diene with interstitial deka(difluoromethylene) chain is converted to the corresponding diepoxide by repeated reacUon with a very large excess of hypofluorous acid-acetonitrile complex [22](equation 14)... 

The hypofluorous acid/acetonitrile complex has also been used for the oxidation of secondary alcohols and for the Baeyer Villiger oxidation of ketones.24-25... 

A more efficient agent than peroxy compounds for the epoxidation of fluoro-oletins with nonfluonnated double bond is the hypofluorous acid-acetonitrile complex [22] Perfluoroalkylethenes react with this agent at room temperature within 2-3 h with moderate yields (equation 13), whereas olefins with strongly electron-deficient double bond or electron-poor, stencally hindered olefins, for example l,2-bis(perfluorobutyl)ethene and perfluoro-(l-allcylethyl)ethenes, are practically inert [22] Epoxidation of a mixture of 3 perfluoroalkyl-1-propenes at 0 °C is finished after 10 min in 80% yield [22] The tnfluorovinyl group in partially fluonnated dienes is not affected by this agent [22] (equation 13)... 

It is possible that the iodine and base could be generated in the way cited earlier for the oxidation of 2-methylnaphtho-quinone. Fluorine forms a hypofluorous acid-acetonitrile complex when it is passed into wet acetonitrile. This complex has been used to convert olefins, such as undecylenic acid, oleic, and cinnamic acid to the corresponding epoxides in 90% yields.294 The disadvantages of the process are the need to handle the very reactive fluorine and the need to recycle the by-product hydrogen fluoride. 

Though it requires vigorous conditions and is less common than nucleophilic epoxidation, electrophilic epoxidation of aperfluoroalkene is possible with the potent combination of chromic oxide and fluorosulfonic acid, providing another route to hexafluoropropylene oxide (1). As a further example of electrophilic attack, hexa-fluoro Dewar benzene (3) is transformed into either a mono- or a diepoxide by the powerful hypofluorous acid-acetonitrile complex.The fact that the much weaker electrophile MCPBA readily epoxides such electron-deficient alkenes as ethyl pentafiuoromethacrylate (4) suggests that it actually reacts via nucleophilic attack at the [3-carbon. 

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