Selenides methoxylation

In contrast to the cathodic reduction of organic tellurium compounds, few studies on their anodic oxidation have been performed. No paper has reported on the electrolytic reactions of fluorinated tellurides up to date, which is probably due to the difficulty of the preparation of the partially fluorinated tellurides as starting material. Quite recently, Fuchigami et al. have investigated the anodic behavior of 2,2,2-trifluoroethyl and difluoroethyl phenyl tellurides (8 and 9) [54]. The telluride 8 does not undergo an anodic a-substitution, which is totally different to the eases of the corresponding sulfide and selenide. Even in the presence of fluoride ions, the anodic methoxylation does not take place at all. Instead, a selective difluorination occurs at the tellurium atom effectively to provide the hypervalent tellurium derivative in good yield as shown in Scheme 6.12. 

Related to these reacations is the anodic methoxylation of sulfides carrying an electron-withdrawing substituent, such as cyano [105], fluoromethyl [106], difluoromethyl [106], or trifluoromethyl [106-109] in the a-position [Eq. (41)]. Yields are typically between 50 and 90%. An analogous reaction has been reported for selenides carrying electron-withdrawing perfluoroalkyl or cyano substituents [110]. 

These methoxylated and acetoxylated selenides are a-perfluoroal-1 1 monoselenoacetals, which could serve as useful building blocks in a manner similar to that of their sulfur analogues. Thus far, only a limited number of methods have been developed for the preparation of monoselenoacetals and these require rather complicated procedures or specialized reagents. In this regard, the electrochemical method is advantageous as the monoselenoacetals can be prepared in a one-step reaction under mild conditions. 

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