Antimony halogen fluorides

The role of Lewis acids in the formation of oxazoles from diazocarbonyl compounds and nitriles has primarily been studied independently by two groups. Doyle et al. first reported the use of aluminium(III) chloride as a catalyst for the decomposition of diazoketones.<78TL2247> In a more detailed study, a range of Lewis acids was screened for catalytic activity, using diazoacetophenone la and acetonitrile as the test reaction.<80JOC3657> Of the catalysts employed, boron trifluoride etherate was found to be the catalyst of choice, due to the low yield of the 1-halogenated side-product 17 (X = Cl or F) compared to 2-methyI-5-phenyloxazole 18. Unfortunately, it was found that in the case of boron trifluoride etherate, the nitrile had to be used in a ten-fold excess, however the use of antimony(V) fluoride allowed the use of the nitrile in only a three fold excess (Table 1). 

The powder and dust of antimony are toxic and can cause damage to the lungs. The fumes of antimony halogens (chlorides and fluorides) are especially dangerous when inhaled or in contact the skin. 

The binding of the antimony lone pair of electrons in antimony(III) fluoride with a halogen molecule promotes the formation of the intermediate complex (B) and the fluorination reaction. 

Replacement of Halogens by Fluorine with Antimony(IIl) Fluoride 12.1.1. In the Absence of Catalysts... 

The reaction of 5-substituted l.l,3.3-tetrachloro-1.3-dihydroisoben7.ofui ans (R = H, MeO, halogen) with antimony(lll) fluoride is accompanied by partial isomerization of the starting substrates into 2-(trichloromethyl)-5-substituted benzoyl chlorides followed by fluorination of the cyclic and acyclic compounds. No such isomerization is observed when 1,1,3.3-tetrachloro-... 

In contrast to aryl trichloromethyl ethers (see Section 12.1.2.), the replacement of chlorine atoms by fluorine in aryl trichloromethyl sulfides using antimony(III) fluoride (or hydrogen fluoride) proceeds under milder conditions, without a catalyst. Various substituents in the aromatic ring have little effect on the halogen exchange. The yields of aryl trifluoromethyl sulfides are 60 to 90% (see Table 1). 

In cases where only difluorophosphanes are formed from dichlorophosphanes by halogen exchange with antimony(III) fluoride, the former can be converted into tetrafluoro-25-phosphanes by treatment with chlorine gas in the presence of antimony(III) fluoride.46,52... 

Replacement of Halogens by Fluorine and Addition of Fluorine to C = C Bonds with Antimony(V) Fluoride and Fluoroantimonates... 

Halogen exchange reactions, too, are valuable sources of fluorinated pyrimidines, especially 2-, 4-, and 6-fluoro derivatives. Sources of fluoride ion have included hydrogen, sodium, potassium, cesium, antimony, silver fluorides, and sulfur tetrafluoride. All of the reactions required heating. Prepared from nucleophilic fluorination processes have been... 

Halogen atoms in certain inorganic compounds may be replaced by fluorine by the use of antimony (III) fluoride without a catalyst. In other cases, varying amounts of different kinds of catalysts are required. For example, sometimes the addition of chlorine in the amount of 1 % of the antimony (III) fluoride will suffice. Molecules which are more difficult to fluorinate may require chlorine, bromine, or antimony(V) chloride in quantities amounting to as much as 5% of the weight of antimony (III) fluoride used. 

The reaction involves the replacement of the halogen atoms in nonpolar halide molecules by fluorine atoms. The fluorinating agent is usually resublimed antimony (III) fluoride. If necessary, a catalyst, such as antimony(V) chloride, chlorine, or bromine, may be used. 

Antimony(lll) fluoride, " antiinony(lll) fluoride activated with pentavalent antimony salts [anlimony(V) fluoride, antimony(V) chloride, antimony(V) bromide, or by the addition of bromine or chlorine to form pentavalent antimony salts in situ], SbFjX, and antimony(V) fluoride substitute active halogens. In general, antimony fluorides can substitute halogens in polyhalogenated compounds when more than one possible site of fluori-natioii is present, the following order of reactivity is observed (where X = Br or C ) ... 

Fluorinated ethenes react with halogenated alkanes by an electrophilic alkylation reaction in the presence of antimony(V) fluoride or hydrogen fluoride/antimony(V) fluoride. For example, the reaction of 1,1,1-trifluoroethane with tetrafluoroethene in the presence of antimony(V) fluoride yields 1.1,1,2,2,3,3-heptafluorobutane (8) in good yield. ... 

Some cycloaddition reactions of oxaziridine 59 with halogenated alkenes have been reported along with reactions with trimethylsilyl cyanide and antimony penta-fluoride. A related cycloaddition of oxaziridine 94 with hexafluoroacetone has been reported. 

Vinyl and phenyl mfluoromethyl groups are reactive in the presence of aluminum chloride [10] Replacement of fluorine by chlorine often occurs Polyfluori-nated trifluoromethylbenzenes form reactive a,a-difluorobenzyl cations in antimony pentafluoride [11] 1 Phenylperfluoropropene cyclizes in aluminum chloride to afford 1,1,3-trichloro 2 fluoroindene [10] (equation 10) The reaction IS hypothesized to proceed via an allylic carbocation, whose fluoride atoms undergo halogen exchange... 

The magnetic criterion is particularly valuable because it provides a basis for differentiating sharply between essentially ionic and essentially electron-pair bonds Experimental data have as yet been obtained for only a few of the interesting compounds, but these indicate that oxides and fluorides of most metals are ionic. Electron-pair bonds are formed by most of the transition elements with sulfur, selenium, tellurium, phosphorus, arsenic and antimony, as in the sulfide minerals (pyrite, molybdenite, skutterudite, etc.). The halogens other than fluorine form electron-pair bonds with metals of the palladium and platinum groups and sometimes, but not always, with iron-group metals. 

CsCl HgCl2=3 1, 2 1, 1 1, 2 3, 1 2, and 1 5 and five caesium antimonious fluorides where CsF SbF3=l 1, 3 4, 4 7, 1 2, and 1 3. According to I. Remsen s rale (1889) When a halide of any element combines with a halide of an alkali metal to form a double salt, the number of molecules of the alkali salt which are added to one molecule of the other halide is never greater, and is generally less than the number of halogen atoms contained in the latter—for instance, in the double fluoride of sodium and aluminium, where the negative halide has three fluorine atoms, no more than three molecules of sodium fluoride will be found united with one of aluminium fluoride. 

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