Phosphonium tetramethyl

The olefin metathesis of 3-hydroxy-4-vinyl-l,2,5-thiadiazole 112 and a McMurry coupling reaction (Ti3+ under reductive conditions) of the aldehyde 114 were both unsuccessful <2004TL5441>. An alternative approach via a Wittig reaction was successful. With the use of the mild heterogenous oxidant 4-acetylamino-2,2,6,6-tetramethyl-piperidine-l-oxoammonium perfluoroborate (Bobbitt s reagent), the alcohol 113 was converted into the aldehyde 114. The phosphonium salt 115 also obtained from the alcohol 113 was treated with the aldehyde 114 to give the symmetrical alkene 116 (Scheme 16) <2004TL5441>. 

The reaction of phosphines and alkyl halides presents an alternative way to generate phosphonium electrophiles (Scheme 3.8). In particular, the combination of a phosphine and carbon tetrabromide (the Appel reaction) allows for in situ formation of a phosphonium dibromide salt (48, X = Br). Treatment of a hemiacetal donor 1 with the phosphonium halide 48 initially provides the oxophosphonium intermediate 38 (X = Br). However, the oxophosphonium intermediate 38 can react with bromide ion to form the anomeric bromide intermediate 49 (X = Br) with concomitant generation of phosphine oxide. With the aid of bromide ion catalysis (i.e. reversible, catalytic formation of the more reactive P-anomeric bromide 50) [98], the nucleophile displaces the anomeric bromide to form the desired glycoside product 3. The hydrobromic add by-product is typically buffered by the presence of tetramethyl urea (TMU). 

The complex formed on addition of cuprous iodide to a solution of a lithium dialkylamide in ether or tetrahydrofuran is effective in the reductive coupling of allylic halides to give 1,5-dienes with preservation of stereochemistry. This method has been used5 for the stereospecific synthesis of all-trans-squalene and (E,Z,Z,E) squalene from (E,E)- and (Z,JE)-farnesyl bromides, respectively. In an attempted synthesis of (3S)-squalene-2,3-epoxide, 4-[(4R)-2,2,5,5-tetramethyl-l,3-dioxolan-4-yl]butan-2-one (1) and the phosphonium iodide (2) were prepared.6 Unfortu-... 

Tetramethyl- and tetraethyl-ammonium or -phosphonium can take the place of an alkali metal 54)- These compounds are formed at graphite anodes on electrolyzing solutions of the corresponding salts in liquid ammonia. The tetraethyl ammonium compound is best prepared by allowing the blue solution obtained by electrolysis of the azide in liquid ammonia to react with finely powdered graphite. In this case intercalation leads only to stage 2, as, m ay be seen from the ratio 1(C2H5)4N 25C determined by analysis. Whereas the blue solution starts... 

This is the reason why peptide chemists, to decrease the problems of purification prefer for long peptides to use protecting groups (tert-butyloxycarbonyl (t-Boc), benzyloxycarbonyl (Z), fluorenylmethyloxycarbonyl (FMOC).) and classical reagents such as T.B.T.U. (0-lH-benzotriazol-l-yl)-l,l,3,3-tetramethyl uronium tetrafluoroborate), B.O.P.(benzotriazol-l-yl-oxy-tris (dimethylamino) phosphonium hexafluorophosphate and so on in polar solvents such as N,N-dimethylformamide or N-methylpyrrolidone. But this solvents are not compatible with the acidic deprotection reagents such as trifluoroacetic acid and... 

The carbon skeleton structure has a determinate role in the efficiency of the reagent for the activation step. Thus, the pyrrolidino (HAPyU) derivative is much more reactive than the piperidino (HAPipU), which is more reactive than tetramethyl (HATU). The same phenomenon occurs with the phosphonium salts (PyXOP is preferred to XOP). 

Bis tetrakis (hydroxymethyl) phosphonium sulfate. See Tetrakis (hydroxymethyl) phosphonium sulfate Bis (2,2,6,6-tetramethyl-4-plperidinyl) decanedloate. See Bis (2,2,6,6-tetramethyl-4-plperldlnyl) sebacate... 

TMEDA. See 1,3-Diaminopropane N,N,N, N -Tetramethylethylenediamine TMG. See Tetramethyl guanidine TMG acid. See 3,3-Tetramethylene glutaric acid TMI. See p-Tolyl isocyanate m-TMI. Seem-Tolyl isocyanate 3-[(Prop-1-en-2-yl) phenyl] prop-2-yl isocyanate o-TMI. See o-Tolyl isocyanate p-TMI. See p-Tolyl isocyanate TMi (Meta). See 3-[(Prop-1-en-2-yl) phenyl] prop-2-yl isocyanate TML. See Tetramethyl lead TMOS. See Tetramethoxysilane TMP. See Trimethylolpropane 2,3,6-TMP. See 2,3,6-Trimethylphenol 2,4,-TMP. See Isooctane TMPC. See Tetrakis (hydroxymethyl) phosphonium chloride... 

Benzyl trimethyl ammonium hydroxide Cetrimonium bromide Dimethyl diallyl ammonium chloride Laurtrimonium bromide Laurtrimonium chloride Methyl tributyl ammonium chloride Tetrabutyl ammonium bromide Tetrabutyl ammonium chloride Tetrabutyl ammonium fluoride Tetra-n-butyl ammonium hydrogen sulfate Tetra-n-butyl ammonium hydroxide Tetrabutyl ammonium iodide Tetrabutylphosphonium acetate, monoacetic acid Tetrabutylphosphonium bromide Tetrabutylphosphonium chloride Tetraethylammonium bromide Tetraethylammonium hydroxide Tetrakis (hydroxymethyl) phosphonium chloride Tetramethylammonium bromide Tetramethylammonium chloride Tetramethylammonium hydroxide Tetramethyl ammonium iodide Tetraphenyl phosphonium bromide Tetrapropyl ammonium bromide Tetrapropyl ammonium iodide Tributylamine Tributyl phosphine Tributyl (tetradecyl) phosphonium chloride Trioctyl (octadecyl) phosphonium iodide catalyst, phase-transfer Tetraethylammonium chloride Tetraoctylphosphonium bromide Tri-n-butyl methyl ammonium chloride Tri methyl phenyl ammonium hydroxide catalyst, phenolics Triethylamine... 

In this technique, two types of reactants are placed separately in two immiscible solvents, one of which is water. Polymerisation takes place at the interface in the presence or absence of a phase transfer catalyst (PTC) such cetyl tributyl ammonium bromide (CTAB), benzyl dimethyl hexadecyl ammonium chloride (BDMHDAC), tetramethyl ammonium bromide or tetraphenyl phosphonium bromide. This process is carried out by agitation or under static conditions. This technique is effective for condensation polymers or for the formation of polyaniline nanofibre. The advantages of the interfacial polymerisation technique include the use of simple equipment, nfild reaction conditions and flexibility in the ratio or purity of reac-... 

Unprotected glycosylamines could be directly coupled to carbojg l groups of protected aminoacids. The most commonly used reagents include benzotriazo-l-yl-oxytris (dimethylamino) phosphonium hexa-fluorophosphate (BOP), 0-[lH- benzotriazo-l-yl)- N, N, M // -tetramethyl-uronium tetrafluoroborate (TBTU), hexafluorophosphate (HBTU), l-hydrojybenzotriazole (HOBt) and 3,4-dihydro-3-hydro g -4-one-l,2,3-triazine. Unprotected glycosylamines could also be coupled to the pentafluoro activated ester of FmocAspO Bu. 

The following chemicals were used as received (from Aldrich unless otherwise noted) 2,6-diaminoanthraquinone, 2,5-dichloro-p-phenylenediamine, 2,6-diamino-5-nitropyrimidine, 2,3,5,6-tetra-methyl phenylenediamine, 2,6-diamino-8-purinol hemisulfate monohydrate, adenine (Chemalog Chemical Dynamics Corp.), 1,9-diamino-nonane, 4,4 -diaminodiphenyl sulfon (Fluka AG), 4,4 -methylene-dianiline, tetraphenyl phosphonium iodide, tetrabutyl ammonium iodide, tetramethyl ammonium bromide, dibenzo-l8-crown-6, 15-crown-5, triphenylantimony dichloride and triethylamine (Eastman Kodak Co.). 

Tetrabutyl Tetraphenyl Tetramethyl Ammonium Phosphonium Ammonium Iodide Iodide Bromide... 

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