Phenyl selenides, oxidation with hydrogen peroxide

Other methods for the synthesis of cyanoacrylate monomers include pyrolysis of 3-alkoxy-2-cyanopropionates (1), transesterification of cyanoacrylates with alcohols (19,20), displacement of monomer from the corresponding anthracene Diels-Alder adduct by treatment with maleic anhydride (7,21), esterification of cyanoacrylic acid or cyanoacryloyl chloride with alcohols (22), and the oxidation of alkyl 2-cyanopropionate phenyl selenides with hydrogen peroxide (23). These alternative methods are particularly useful for the preparation of monomers not readily prepared by thermal decomposition of cyanoacrylate polymer. 

On p-hydroxyalkyl phenyl selenides, die oxidation-elimination is best achieved with an excess of 30% aqueous hydrogen peroxide according to die original description of Sharpless (Scheme 174, c and d). Although l-(l -hycyclohexyl phenyl selenide p uces under these conditions a hydroperoxide (Scheme 174, a), the sired elimination reaction has been successfully achieved with sodium periodate in ethanol (Scheme 174, b). 

The oxidation of (silatranyhnethyl)phenylselenide (116) with 30% hydrogen peroxide in ethanol affords the corresponding selenoxide (117a) in 91% yield (equation 146). The selenone 117b is formed by using 70% H202 . Unstable selenoxide is obtained from (2-silatranylethyl)phenyl selenide under the same conditions . ... 

Other perfluoroalkyl-phenyl analogues 561 proved difficult to prepare and handle, but 3,5-bis(perfluorooctyl)phenyl butyl selenide 562 was accessible as precursor for the identical active species 563. The catalyst 562 showed higher activity (turn over frequency) compared to diselenide 553 in the oxidation of aldehydes and ketones with aqueous hydrogen peroxide. Furthermore, 562 could be used to oxidize substrates under fluorous monophasic, biphasic, and triphasic conditions (Fig. 7.29) [360]. 

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