Phosphonium tetramethyl-, bromide

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-... 

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-... 

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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