| Abstract
| - Thianthrene cation radical tetrafluoroborate (Th•+BF4-) added to 2-butyne, 3-hexyne, 4-octyne, and5-decyne in MeCN to form trans bisadducts R(Th+)CC(Th+)R, where R = Me, Et, Pr, Bu (7a−d).Phenoxathiin cation radical tetrafluoroborate (PO•+BF4-) added similarly to the last three alkynesto form adducts R(PO+)CC(PO+)R, 8b−d. Cyclic monoadducts were not found. The trans structuresof 7 and 8 were deduced with X-ray crystallography (7c) and NMR spectroscopy. When solutionsof adducts in CHCl3 and MeCN were deposited on activated alumina, elimination of thianthrene(Th) and phenoxathiin (PO) occurred almost quantitatively. Detailed studies with (7b−d) indicatedthat a cumulene (15) was formed by the elimination of Th and that 15 was subsequently convertedinto small amounts of other products. In CHCl3, these products were the respective alkyne,thianthrene 5-oxide, an α-diketone (11), an α-hydroxyalkyne (12), and hydrogen. The same productswere formed in MeCN along with an α-acetamidoalkyne (13). The formation of 15 and productsderived from it is explained and was confirmed by preparation and reactions of 2,3,4-hexatriene.
|
