Triphenylphosphine-Carbon tetrabromid

French chemists have been able to increase the yields to 85-90% by use of a 40 60 mixture of THF—ether as solvent instead of pure THF. Note that Corey and Fuchs (4, 550) have prepared 1,1-dibromo-l-alkenes by the reaction of an aldehyde with triphenylphosphine, carbon tetrabromide, and zinc in methylene chloride. 

Conversion of -OH to -N3. Japanese chemists have converted the primary 5 -hydroxyl groups of nucleosides into azided groups in 50-90% yield by reaction with triphenylphosphine, carbon tetrabromide, and lithium azide in DMF at 20° (24 hr.). The mechanism in equation I is suggested. 

ALKYL AZIDES Triphenylphosphine-Carbon tetrabromide-Lithium azide. Zinc chloride. 

The reaction of triphenylphosphine with carbon tetrabromide in acetonitrile has been studied by conductimetric titration and found to be rapid, leading to the formation of the salt (87), which was isolated from the reaction mixture. Treatment of alcohols with the triphenylphosphine-carbon tetrabromide reagent in the presence of radiolabelled bromide ion gives a rapid, low-temperature procedure for the synthesis of radiolabelled bromoalkanes under neutral conditions. ... 

Several new methods for the preparation of 1-haloalkynes have been described. High yields of bromo compounds, e.g. 28, are obtained by treatment of alkynes with triphenylphosphine/carbon tetrabromide, or with a concentrated aqueous solution of potassium hypobromite and potassium hydroxide (equation 1). 1-Iodoalkynes are produced from terminal alkynes and bis(pyridine)iodine(I) tetrafluoroborate in methanol in the presence of sodium methoxide (equation 2) or from alkynes with a mixture of iodine, potassium carbonate, copper(I) iodide and tetrabutylammonium chloride under phase-transfer catalysis. Lithium acetylides 29 (R = Ph, t-Bu, HOCH2 etc.) react with zinc iodide and bis(trimethylsilyl) peroxide to yield 1-iodoalkynes. The method has been... 

Modifications of C6 of CyD other than by tosylation are very rare. However, a single-step quantitative-yield synthesis of CyD monoaldehydes has been published. The CyD was dissolved in an organic solvent, Dess-Martin perodinane was added, and the mixture was stirred for 1 h at room temperature. Addition of acetone and cooling allowed isolation of the crude product by filtration [16]. Another synthesis was performed by using IBX (l-hydroxy-l,2-benziodoxol-3(lH)-one 1-oxide) as oxidant in DMSO. Mono-oxidation of jS-CyD was performed along with its incorporation into chitosan by a reductive coupling reaction [17]. A direct azidation of CyDs with sodium azide in the presence of triphenylphosphine-carbon tetrabromide has also been reported [18]. 

Cyclodextrins monoazide 14a-b can also be synthesized by direct substitution reaction, using triphenylphosphine, carbon tetrabromide, and Hthium azide in DMF, but the yields are modest [24]. 

Triphenylphosphine/carbon tetrabromide lithium azide Azides from alcohols Preferential replacement... 

Related Reagents. A number of related reagents have been used for the conversion of alcohols to bromides. Other reagents for this purpose covered in this encyclopedia include l,2-Bis(diphenylphosphino)ethane Tetrabro-mide, Bromine-Triphenyl Phosphite, Hydrogen Bromide, Triphenylphosphine-Carbon Tetrabromide, and Triphenylphos-phine Dibromide. ... 

Triphenylphosphine-Carbon Tetrabromide Triphenylphosphine-Carbon Tetrachloride Triphenylphosphine-Diethyl Azodicarboxylate Triphenylphosphine-y V-Bromosuccinimi de... 

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