Bis(trimethylsilyl)selenide (HMDSS) acts as an efficient reagent in the TBAF catalyzedreaction with different substituted epoxides, episulfides, and aziridines, leading to β -functionalized diselenides in a highly regio- and stereoselective way. When using α -bromo alkyl ethers as trapping agent, 1,3-oxaselenolanes and 1,3-thiaselenolanes can be isolated, while 1,3-selenazolidines could be obtained