[Baeyer-Villiger reaction of benzaldehydes possessing oxygen functions with SeO2-H2O2]

[Novel reactions using organoselenium compounds]

Organoselenium compounds are important tools in the field of synthetic chemistry because their specific reactivities have been used as the key reactions in the synthesis of various organic compounds. Nucleophilic organoselenium reagents are frequently utilized to introduce a selenium atom into organic molecules. However, there is no method available for the direct transformation of a hydroxy group into a selenayl group, except for the Grieco-Nishizawa reaction. In this review, novel methods for the conversion of alcohols into selenides in one step are described: both selenolate-aluminum chloride and TMSSePh-aluminum bromide are effective reagent systems for this transformation. Although benzylic alcohols could be efficiently converted to the corresponding selenides, these reagent systems were not applicable to non-benzylic alcohols. On the other hand, the reaction of cinnamyl alcohol with TMSSePh-aluminum bromide afforded 4-phenylselenochroman as a main product. The scope and limitations of this selenochroman formation were investigated using several types of allyl alcohols. To clarify the reaction path, the reaction of cinnamyl phenyl selenide with aluminum bromide was carried out. As expected, 4-phenylselenochroman was obtained in high yield. The transformation of various cinnamyl selenides was also successful in generating the corresponding selenochroman derivatives. Consequently, we developed a novel method for selenochroman synthesis.

Selenium-catalyzed oxidations with aqueous hydrogen peroxide. 2. Baeyer-Villiger reactions in homogeneous solution

Several diselenides were tested for catalytic activity in Baeyer-Villiger reactions with 60% aqueous hydrogen peroxide. Bis[3,5-bis(trifluoromethyl)phenyl] diselenide forms the corresponding 3,5-bis(trifluoromethyl)benzene seleninic acid in situ, which is a highly reactive and selective catalyst for the oxidation of carbonyl compounds in 1,1,1,3,3,3-hexafluoro-2-propanol, 2,2,2-trifluoroethanol, or dichloromethane.