1,3-Dithienium- und 1,3-Dithioleniumsalze. IX. Reaktionen von 1,3-Dithian-2-ylium-tetrafluoroboraten mitC-Nucleophilen

Abstract

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 obtained by variable methods, react in good to excellent yields with variable C‐nucleophiles to new geminal disubstituted 1,3‐dithianes. The latter 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 type of the 1,3‐dicarbonyl compounds 9. The reduction of 3‐oxo‐2‐(2‐phenyl‐1,3‐dithian‐2‐yl)‐ethoxybutanoat–following a diastereoselective pathway – leads to the Cram product 11. Further presented is the crystal structure of 2‐phenyl‐1,3‐dithiane‐2‐ylium tetrafluoroborate (1b).

Pot-Economy Autooxidative Condensation of 2-Aryl-2-lithio-1,3-dithianes

“…The solvent was filtered and evaporated. Flash chromatography (Hex:AcOEt, 95:5) yielded starting material 4a (20%, 39 mg, 0.20 mmol) and dimer 2 (27%, 53 mg, 0.14 mmol) as a white solid, with same spectral characterization as previously described …”

“…Flash chromatography (Hex:AcOEt, 95:5) yielded starting material 4a (20%, 39 mg, 0.20 mmol) and dimer 2 (27%, 53 mg, 0.14 mmol) as a white solid, with same spectral characterization as previously described. 49 2 : 1 H NMR (300 MHz, CDCl 3 ) δ ppm 7.54–7.15 (m, 10H), 2.70–2.49 (m, 8H), 2.01–1.75 (m, 4H). 13 C NMR (75 MHz, CDCl 3 ) δ ppm 135.0, 133.0, 127.6, 127.3, 70.9, 29.0, 24.7.…”

Addition of dithi(ol)anylium tetrafluoroborates to α,β-unsaturated ketones

“…Our recent approach to the synthesis of α-arylazo-carbonyl compounds showed that easily available dithi(ol)anylium tetrafluoroborates [27–28] (following shortened to TFBs) serve as stable precursors for ketene dithioacetals [29]. In accordance with previous work of others [30], they allow the addition of electrophiles in α-position independent of further presence of activating electron-withdrawing groups (EWGs). In the present study we will show the successful use of dithi(ol)anylium TFBs for the Michael-type addition to α,β-unsaturated ketones.…”