Efficient methods have been disclosed for the construction of nitrogen and oxygen containing heterocyclic systems attached to selenocysteine or selenoglutathione. An inorganic oxidant (K2S2O8) or a mild Lewis acid (CuBr2) was employed for the generation of selanyl electrophiles that were further trapped with phenyl propiolates, methyl 2-(phenylethynyl)benzoate,N-phenyl propiolamides and 2-(phenylethynyl)benzamide thus providing the respective coumarins, isocoumarins, quinolin-2-ones and isoquinolin-2-onesvia6-endo-digcyclization. The use of visible light resulted in divergent reactivity providing triple bond addition products or spirocyclic compounds bearing selenocysteine moieties.