Selenium chemistry became, over the last 30 years, particularly useful for
synthetic organic chemistry [1]. Inorganic as well as organic selenium comp
ounds allow transformation which otherwise cannot be done or require much m
ore drastic conditions to proceed. We have over the last 25 years explored
the reactivity of elemental selenium as well as its inorganic and organic d
erivatives. We report here our recent finding concerning (i) organic disele
nols and -diselenolates and (ii) the role of selenoxides in the enantiosele
ctive dihydroxylation of C,C double bonds using catalytic amounts of osmium
tetroxide.