Regio- and Stereoselective Synthesis of a Novel Family of Unsaturated Compounds with the S-Se Bond and Their Cyclization to 2,3-Dihydro-1,4-thiaselenines

Regio-and stereoselective ring-opening reaction of 2-bromomethyl- 1,3-thiaselenole with thiols proceeded as nucleophilic attack at the selenium atom of seleniranium intermediate affording unsaturated selanyl sulfides, (Z)-CH2= CHSCH= CHSeSR, in up to 93% yield. Dithiols were involved in this reaction giving symmetrical polyunsaturated compounds with two S-Se bonds in 70-75% yields. Efficient synthesis of 2( organylsulfanyl)-2,3-dihydro-1,4-thiaselenines in 69-96% yields was developed by the acid-catalyzed cyclization of the unsaturated selanyl sulfides. Mild reaction conditions (room temperature) and short reaction times are important features of this methodology.