Hypofluorous acid, epoxidation

A more efficient agent than peroxy compounds for the epoxidation of fluoro-olefins with nonfluonnated double bond is the hypofluorous acid-acetomtrile 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, sterically hindered olefins, for example l,2-bis(perfluorobutyl)ethene and perfluoro-(l-alkylethyl)ethenes, are practically inert [22] Epoxidation of a mixture of 3 perfluoroalkyl-1-propenes at 0 C IS finished after 10 mm in 80% yield [22] The trifluorovinyl group in partially fluorinated dienes is not affected by this agent [22] (equation 13)... 

The reaction of fluorine with water, producing hypofluorous acid (HOF) and subsequently oxygen difluoride (OF2), has been the subject of intensive study over the last fifty years.1 Additionally, hypofluorous acid in acetonitrile has been characterized.5 The reagents are potentially explosive and present a toxicity hazard similar to fluorine therefore, work should be carried out in an efficient hood and proper safety equipment is required. It was established in the earliest investigations that the reaction of hypofluorous acid with alkenes in nonpolar solvents gives fluoro hydrins, e.g. 1, in high yield.6 However, it is now clear that epoxides are initially formed in acetonitrile7 and 1,2-epoxycyclohexane (2) is formed in reactions with cyclohexene in various solvents.5... 

Stilbene is also converted into the epoxide and the preparation of the lsO-isomcr 3 in high isotopic purity can also be performed, while 1,1-diphenylethene is transformed to 1.1-di-phenylethane-l,2-diol (4),8 and (T)-stilbene to a mixture of benzophenone9 and //wo-2-fluoro-1.2-diphenylethanol. Fluoro-substituted alkenes can also be converted with a hypofluorous acid/acetonitrile mixture into epoxides 5 in high yield.10... 

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. 

Epoxidation of oleic and linoleic acid was readily achieved by treatment with the acetonitrile complex of hypofluorous acid (55). Phase-transfer-catalyzed biphasic epoxidation of unsaturated triglycerides was accomplished with ethylmethyldioxirane in 2-butanone (56). The enantioselective formation of an a,P-epoxy alcohol by reaction of methyl 13()S)-hydroperoxy-18 2(9Z,llfi) with titanium isopropoxide has been reported (57). An immobilized form of Candida antartica on acrylic resin (Novozyme 435) was used to catalyze the perhydrolysis and the interesterification of esters. Unsaturated alcohols were converted with an ester in the presence of hydrogen peroxide to esters of epoxidized alcohols (e.g., epoxystearylbutyrate) directly (58). Homoallyl ethers were obtained from olefinic fatty esters by the ethylaluminium-in-duced reactions with dimethyl acetals of formaldehyde, acetaldehyde, isobutyralde-hyde, and pivaldehyde (59). Reaction of 18 2(9Z, 12Z) with 50% BF3-methanol gave monomethoxy and dimethoxy derivatives (60). A bulky phosphite-modified rhodium catalyst was developed for the hydroformylation of methyl 18 1 (9Z)and 18 1(9 ), which furnished mixtures of formylstearate and diformylstearate (61). 

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