New cyclic dichalcogenonio-selenuranes induced by transannular multichalcogenides participation

Article abstract of DOI:10.1016/0040-4020(96)00583-2

The significant conformational changes was found when cyclic chalcogenides, 1,11-(methanoselenomethano)-5H,7H-dibenzo[b,g][1,5]diselenocin (1) and 1,11-(methanothiomethano)-5H,7H-dibenzo[b,g][1,5]selenathiocin (3), were dissolved in concentrated H₂SO₄; i.e., the twin-chair forms of 1 and 3 in CHCl₃ were converted completely into the twin-boat forms of the selenurane dications 2 and 4 in H₂SO₄. Two-electron oxidation of 1 or 3 with 2 equiv of NOPF₆ gave the cyclic selenurane dication 2PF₆^- salt 2a or 4a which contains two selenonium or two sulfonium cations at the apical positions. The selenurane 2a or 4a could be reduced readily to neutral 1 or 3 upon treatment with PhSH, Ph₃P, phenothiazine, or SmI₂; that is, 2a or 4a acts as an oxidizing agent.