Synthesis of bis(2-haloalkyl) selanes and selenides based on selenium dioxide and terminal alkenes

Selenium tetrahalides generated from selenium dioxide and hydrogen halides (HCl, HBr) reacted with hex-1-ene, hept-1-ene, and oct-1-ene at a SeO₂?alkene molar ratio of 1: 2 to give mixtures of dihalobis-(2-haloalkyl)-λ⁴-selanes (yield 80?90%) and bis(2-haloalkyl) selenides (yield 5?12%). Halogenation of the resulting mixtures afforded 85?93% (calculated on the initial SeO₂) of the corresponding dihalobis(2-haloalkyl)-λ⁴-selanes, and the reduction of the same mixtures with Na₂S₂O₅ gave bis(2-haloalkyl) selenides in 80?86% yield. In the reaction with a SeO₂?alkene ratio of 5: 8, pure dihalobis(2-haloalkyl)-λ⁴-selanes were formed in 84?93% yield. Dichlorobis(2-chloro-2-phenylethyl)-λ⁴-selane was obtained in 72% yield in the reaction of SeO₂?HCl with styrene.