Telluronium Tetrafluoroborate

This was the first-described, non-stabilized ylide, obtained by treatment of the corresponding telluronium tetrafluoroborate with hthium 2,2,6,6-tetramethylpiperidide (LiTMP). Epoxides are obtained by reaction with both aldehydes and ketones. ... 

Dimethyl tellurium in liquid hydrogen fluoride at — 70° was saturated with boron trifluoride. The dimethyl telluronium tetrafluoroborate was detected by 13C- and l25Te-NMR spectroscopy2. 

Similarly prepared were the following triorgano telluronium tetrafluoroborates ... 

Diphenyl Methyl Telluronium Tetrafluoroborate 0.5 g (1.2 mmol) of diphenyl methyl telluronium iodide are dissolved in water. An aqueous solution eontaining 0.23 g (1.2 mmol) of silver tetrafluoroborate is prepared by reacting equivalent amounts of silver oxide and tetrafluoroboric acid. The solutions are mixed, stirred for 1 h at 20°, heated under reflux for 4h, and concentrated. Silver iodide is filtered off and the product crystallized m.p. 135°. 

Reaction of telluronium methylide with carbonyl compounds (general procedure A solution of LiTMP (1.2 mmol) in THF is added to a solution of diphenyltelluronium methyl tetrafluoroborate (1.2 mmol) in THF (8 mL) at -78°C under Nj. The mixture is warmed to -70°C and stirred for 30 min. After cooling to -78°C, the carbonyl compound (1.0 mmol) in THF (2 mL) is added. The reaction mixture is then allowed to warm at room temperature. After the reaction is complete (monitored by TLC), the usual work-up and flash chromatography gives the product. 

---