Trimethylsilyl polyphosphate

Trimethylsilyl esters of tris(thio)phosphonic acids 2070 are readily oxidized by DMSO in toluene at -30 °C to give the dimeric tetra(thia)diaphosphorinanes 2071 and HMDSO 7 [208] (cf. also the oxidation of silylated thiophenol via 2055 to diphenyl disulfide). The polymeric Se02 is depolymerized and activated by reaction with trimethylsilyl polyphosphate 195 to give the corresponding modified polymer... 

Cyclizations can also be carried out with an esterified oligomer of phosphoric acid called polyphosphate ester, which is chloroform soluble.55 Another reagent of this type is trimethylsilyl polyphosphate (Scheme 11.4, Entry 13).56 Neat methanesul-fonic acid is also an effective reagent for intramolecular Friedel-Crafts acylation (Scheme 11.4, Entry 14).57... 

Merriman and colleagues have reported the cydization of N-acyl-l,2-diaryl-l,2-ethanediamine derivatives, obtained by way of a solid-phase approach, to 4,5-diaryl-imidazolines by treatment with trimethylsilyl polyphosphate (TMS-PP) in dichloro-methane solution (Scheme 6.204) [367]. The best results were obtained by micro-... 

Trimethylsilyl polyphosphate (PPSE),1 The reagent is prepared from P205 and [(CHj),Si]20. It is a colorless, volatile liquid, soluble in the usual organic solvents. It is comparable to polyphosphate ester for the Beckmann rearrangement of oximes to amides (3, 230 231). but it is prepared more easily. 

BECKMAN REARRANGEMENT Poly-phosphoric acid. Trimethylsilyl polyphosphate. 

Ketoximes may be rearranged directly to amides under a wide variety of conditicms. Phosphorus pen-tachloride, phosphorus oxychloride, thionyl chloride, trimethylsilyl iodide (TMS-I), formic acid, poly-phosphoric acid, trimethylsilyl polyphosphate and mineral acids have all been successfully employed. Representative procedures using these and other reagent systems have been documented previously. - ... 

Trimethylsilyl iodide converts alcohols to iodides. The disadvantage of this method is the expensive reagent, which is avoided if trimethylsilyl chloride and sodium iodide are used instead (equation 27). Trimethylsilyl polyphosphate (PPSE), which is prepared from hexamethyldisiloxane and phosphorus pentoxide, also activates alcoholic hydroxy groups for substitutions with iodide anions (equation 28). ... 

The similar endo(B)-exo cyclizations have been effected with phosphorus pentoxide and more recently with trimethylsilyl polyphosphate (equation 32 and 33). The starting alkenic oximes are readily obtainable by the alkylation of the oxime dianion. Hence the overall process provides convenient access to the stereospecific synthesis of various heterocycles bearing substituents in the desired positions. 

Cyclocondensation of V-aryl-A -formylethylenediamines 5 6 with trimethylsilyl polyphosphate furnished l-aryl-l//-4,5-dihydroimidazoles 57 in good yields <04S851>. 1,2-Diaminoimidazoles 59 were obtained in good yields by reaction of l,2-diaza-l,3-butadienes 58 with cyanamide under solvent-free conditions <04SL549>. Thiazolium-catalyzed addition of the... 

PPSE trimethylsilyl polyphosphate (polyphosphoric acid trimethylsilyl ester)... 

PPSE = Trimethylsilyl polyphosphate Example 4, Intramolecular Friedel-Crafts acylation ... 

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