Studying the synthesis of new selenium-nitrogene-heterocycles as a part of our medicinal chem. program for the treatment of oxidative stress-related diseases, we uncovered a mild, copper(I)-assisted reaction of selenocyanate with suitably substituted non-activated aromatic bromides.This paper will discuss the scope and limitations of the new copper(I)-assisted synthesis of arylisoselenazolines and azines in terms of (1) the role of the metal salt and (2) the compatibility with amine-, amide-, ester- and nitro-substituents.Like the natural selenium containing enzyme Glutathion Peroxidase, these new low-mol.-weight mimics are able to catalyze the thiol-mediated reduction of hydrogen peroxide and organic peroxides, as will be shown by the comparison of their GPx-activities with the sulfur-analogs and the reference compound Ebselen.Direct competition experiments between the lead compound 4,4-dimethylbenzisoselenazine and Ebselen will be presented to illustrate the significantly higher reactivity as well with thiols as with peroxides, modeling isolated reaction steps of the catalytic cycle.