1,3-DITHIENIUM AND 1,3-DITHIOLENIUM SALTS - IX - REACTIONS OF 1,3-DITHIANE-2-YLIUM TETRAFLUOROBORATES WITH C-NUCLEOPHILES

1,3-Dithian-2-ylium tetrafluoroborates (1), which can be easily obtain ed by variable methods, react in good to excellent yields with variabl e C-nucleophiles to new geminal disubstituted 1,3-dithianes. The latte r compounds are potential precursors of interesting synthetic building blocks. Reactions are described with 2-lithio-1,3-dithianes 2, sodium cyanide 4, sodium salts of the nitro alkanes 7 and CH-acids of the ty pe of the 1,3-dicarbonyl compounds 9. The reduction of 3-oxo-2(2-pheny l-1,3-dithian-2-yl)-ethoxybutanoat - following a diastereoselective pa thway - leads to the Cram product 11. Further presented is the crystal structure of 2-phenyl-1,3-dithiane-2-ylium tetrafluoroborate (1b).