PREPARATION OF SELENOXIDES FROM THE CATALYTIC AUTOXIDATION OF ORGANOSELENIDES WITH NITROGEN-OXIDES

Various alkyl, aryl and benzyl selenides (RSeR') are readily converted in high yields to the corresponding selenoxide in the presence of dio xygen and catalytic amounts of either nitrogen dioxide, nitrosonium ca tion or nitric oxide in acetic acid. The selenoxides are initially iso lated as the acetic acid adducts (from which the free selenoxides are readily liberated by treatment with base). Nitrogen dioxide is also ca pable of the stoichiometric oxidation of the selenoethers; and the ele ctron donor-acceptor or EDA complex with nitrosonium, i.e. [R(2)Se . N O+]NO3- is formed as the first intermediate by the selenoether-induced disproportionation of NO2. The critical role of the nitrosonium EDA c omplex is further demonstrated by the production of selenoxide by an a lternative (low-temperature) photochemical procedure involving the del iberate irradiation of the charge-transfer absorption band of [PhSeMe . NO+]NO3-. A scheme is shown that presents the sequence of redox chan ges of the nitrogen oxides involved in the catalytic conversion of sel enoethers to their selenoxides.