Triphenylphosphine dibromide

Alternate Names bromotriphenylphosphonium bromide dibro-motriphenylphosphorane. 

Solubility adduct sol CH2CI2, MeCN, PhCN, DMF less sol PhH, PhCl. PhsP sol ether, PhH, CHCI3, AcOH less sol alcohol pract. insol. H2O. Br2i sol H2O (3.58 g/100 mL) very sol. alcohol, ether, CHCI3, CCU, CS2. 

Form Supplied in adduct hygroscopic solid commercially available purity 95-%%. Both parent compounds, PhsP and Br2, are widely available. PhsP odorless platelets or prisms purity s99% typical impurity Ph3PO 1%. Br2. dark reddish liquid, volatile, with suffocating odor vaporizes rapidly at rt purity 99.5%. 

Analysis of Reagent Purity adduct P NMR (CH2CI2) -i-49 ppm (ionic form) Raman (solid phase) 239 cm (P-Br). Typical impurities, Ph3P and Ph3PO P NMR (various solvents) -5 to -8 ppm and -i-25 to -i-29 ppm, respectively. 

Preparative Methods several preparations are described, - but in most cases the hygroscopic reagent is prepared just before use by addition of Bromine to Triphenylphosphine in a dry solvent with cooling. 

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By the procedure described in the preceding experiment, 30 g (0.11 mole) of tri-phenylphosphine dissolved in 100 ml of acetonitrile is converted to triphenylphosphine dibromide. After the addition of the bromine has been completed, the cooling bath is removed, the flask is set up for vacuum distillation, and the solvent is removed. To the residue is added /7-chlorophenol (10.3 g, 0.08 mole), and the flask is heated at 200° (mantle, wax bath, or sand bath) until HBr ceases to be evolved (about 2 hours). The flask is cooled and the contents are steam distilled affording crude / -chlorobromo-benzene in about 90% yield. Recrystallization from benzene gives the pure product, mp 65-66°. 

Disubstituted-amino)triphenylphosphonium bromides (72) have been obtained from the reaction of triphenylphosphine dibromide and secondary amines in the presence of triethylamine. ... 

Since hydrogen peroxide, like alkyl hydroperoxides, can be alkylated by alkyl bromide plus silver trifluoroacetate (Eq. 19, R = H),35) an attractive variation of the silver-salt-induced dioxabicyclization uses cis- 1,3-dibromocycloalkane 43 as starting material. Thus Porter and Gilmore obtained 2,3-dioxabicyclo[2.2.1]heptane 9 in 30-40% yield from c s-l,3-dibromocyclopentane, which was itself obtained from the corresponding c/s-diol by reaction with triphenylphosphine dibromide (Eq. 31 R = R = H)36). 

Several papers have been devoted to the subject of reactions of phosphoranes with carboxylic acids and their derivatives. Thus triphenylphosphine dibromide (111) in acetonitrile cleaves lactones,93 while the corresponding dichloride (112) converts esters into acid chlorides.94 The reactions of esters with phosphorus pentachloride (101) have been studied further,95 and the influence of structural changes on the yields of products (113) and (114) has resulted in minor modifications to the mechanism previously96 outlined. 

There are many heterocyclic molecules in which 1,3,4-thiadiazoles are fused to other ring systems. For example, Molina et al. developed a procedure for building a thiadiazole ring on to a properly substituted imidazole moiety (Scheme 29). Reaction of l-amino-2-methylthio-4-phenylimidazole (161) with triphenylphosphine dibromide in dry benzene furnished the 2-methylthio-4-phenyl-l-triphenylphosphoranylidenamino imidazole (162) in a 95% yield. With aroyl chlorides at elevated temperature, this gave the 2-aryl-6-phenylimidazo[2,l-Z ][l,3,4]thiadiazoles (164) in yields between 50% and 70% via the imidoyl chloride intermediate (163) which could be isolated and shown to cyclize to the thiadiazole. The method developed for the imidazole ring was also applicable to the thiadiazolotriazine ring system <88H(27)1935). 

The following procedure is an operatively simple route for the synthesis of bromotrimethylsilane on a preparative laboratory scale from reagents that are readily accessible and inexpensive. This could be a method of choice in some laboratories despite the fact that bromotrimethylsilane is now commercially available (Petrach Systems, Aldrich, or Alpha). Moreover, the procedure also serves as a suitable method for the synthesis of azidotrimethylsilane and isocyanatotrimethylsilane, and is specially useful for the preparation of cyanotrimethylsilane. Thus a mixture of triphenylphosphine dibromide, hexamethyldisiloxane, and a catalytic amount of powdered metal zinc in 1,2-dichlorobenzene is heated under reflux to produce bromotrimethylsilane in nearly quantitative yield, which is simultaneously distilled over a suspension of the corresponding pseudohalogenoacid salt in N, /V-dimethylformamide as solvent.6... 

Bls(2,2,2-triflnoroethoxy)triphenylphosphorane, (C6H5)jP(OCH,CFj)2, (1). Mol. wt. 460.36, hygroscopic, stable in solution at 25 for several weeks. The phosphorane is prepared by reaction of triphenylphosphine dibromide with sodium 2,2,2-trifl uoroethoxide. 

Potassium t-butoxide, 252 Triphenylphosphine dibromide, 333 Triphenylphosphine-2,2 -Dipyridyl disulfide, 332 Zinc iodide, 350 y-Lactams... 

Table 2.2. lists activators used less commonly for Moffatt oxidations. The following activators, namely diphosgene,262 triphosgene,263 2-chloro-1,3-dimethylimidazolinium chloride,264 l-cyclohexyl-3-(2-morpholinoethyl)-carbodiimide metho-p-toluenesulfonate,265 triphenylphosphine dibromide and dichloride,266 and phenyl dichlorophosphate,267 have been the subject of scientific monographs, in which they are proposed as suitable and convenient alternatives to more routinely used activators, and can offer improved oxidation conditions in some substrates. 

Bromotrimethylsilane, 9, 73-74 II, 59. The silane can be prepared in high yield by reaction of triphenylphosphine dibromide and hexamethyldisiloxane catalyzed by powdered zinc (equation 1). 

This reaction can also be conducted with triphenylphosphine in the presence of carbon tetrachloride and triethylamine, or with triphenylphosphine dibromide in the presence of triethylamine. to give carbodiimides 40. 

The triphenylphosphine dibromide can also be attached to a polymeric substrate. ... 

Treatment of bis-alkylideneurea24 with triphenylphosphine dibromide gives bis(Q(-bromo)-carbodiimide 25. ... 

Substitution reactions involving 3/S-hydroxy-A -steroids and their derivatives require special mention. Cholesterol reacts with a variety of halogenating agents, including thionyl chloride / StJ, phosphorus pentachioride [81], haHdes of aluminium or titanium [82], 2-chloro-i,i,2 trifluoroethyl di-ethylamine [83] and triphenylphosphine dibromide [55], to... 

CarbodUmides. Triphenylphosphine dibromide reacts with N,N -disubstituted ureas in the presence of triethylamine to give carbodiimides. 

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