Radical-Based Route to 2-(Trifluoromethyl)-1,3,4-oxadiazoles and Trifluoromethyl-Substituted Polycyclic 1,2,4-Triazoles and Dihydrofurans

O-Ethyl S-[5-(trifluoromethyl)-1,3,4-oxadiazol-2-yl]methyl xanthate was readily prepared on a large scale and shown to undergo very efficient intermolecular radical additions to unactivated alkenes. The products were further elaborated by exploiting both radical and ionic processes to provide a variety of trifluoromethyl-substituted derivatives, including medicinally relevant triazoles. In particular, the application of a radical allylation on the initial adducts leads to structures that are able to undergo intramolecular [4 + 2] cycloaddition reactions.