Iodine monofluoride, addition

The direction of iodine monofluoride addition to hexafluoropropene and, 1,1-di-fluoroethene suggests an electrophilic reaction mechanism. However, chlorotrifluoroethene gives a mixture of isomers both with iodine monofluoridc and with bromine monofluoride .1 0 The reactions of fluoroalkenes with bromine monofluoride proceed too quickly and for this reason they are conducted in l,l,2-trichloro-l,2,2-trifluoroethane though this hampers the isolation of addition products. 

Bromine monofluoride or iodine monofluoride can be prepared from the corresponding elements in trichlorofluoromethane at — 781 and — 45 C,2,3 respectively. The compounds are unstable and decompose at low temperatures, iodine monofluoridc at — 14 C2,3 and bromine monofluoride, in part, even at — 78 C.1 Therefore, they are used, without separation and purification, in Freon solutions at low temperatures or, most frequently, as stoichiometric mixtures bromine trifluoride/bromine and iodine pentafluoride/iodine. A solution of iodine monofluoride, obtained by bubbling nitrogen-diluted fluorine gas into a suspension of iodine in trichlorofluoromethane at — 75 C, was used for addition to alkene C = C bonds. The reaction is regioselective and in most cases obeys the Markovnikov rule.4 Iodine monofiuoride prepared in situ reacts quite efficiently with steroidal alkenes.4... 

C), has proven to be too reactive and nonselective towards alkenes. In the presence of 2 % ethanol, bromine monofluoride adds to C = C bonds at controllable rates but bromo ether byproducts arc formed that make the isolation of the desired bromofluoroalkanes difficult. The addition of bromine monofluoride is less regioselective compared to the addition of iodine monofluoride positional isomers are always present in the reaction mixture together with the major Markovnikov-typc addition products. 

When diphenylacetylene dissolved in cold chloroform reacts with iodine monofluoride suspended in trichlorofluoromethane, the iodine atoms in the primary addition product are easily replaced by fluorine to give l,1,2,2-tetrafluoro-1,2-diphenylethane (60%) along with benzil (10%). Since the C —Br bond is stronger than the C —I bond, the reaction of bromine monofluoride with diphenylacetylene gives 1,1-dibromo-2,2-difluoro-1,2-diphenylethane (65%) and benzil (15%). 

The aluminum/aluminum triiodide catalyzed addition of iodine monofluoride to perhaloal-kenes with terminal CF2 groups provides high yields of the products in the case of tetra-lluoroethene, chlorotrifluoroethene, hexafluoropropene, and 1,1-dichloro-2,2-difluoroethcne, but rather moderate or low yields for 1,2-dichloro-l,2-difluoroethene, 1-chloro-2,2-di-fluoroethene, and trifluoroethene.9... 

The stoichiometric equivalents of halogen fluorides, i.e. chlorine monofluoride, bromine monofluoride and iodine monofluoride, have found a wide application in addition reactions to double bonds. The equivalents are obtained by reacting A -haloamides or free halogens in combination with hydrogen fluoride or its salts as the source of fluoride ions. The reactions proceed under mild conditions at — 80 to 20 "C in anhydrous hydrofluoric acid or diethyl ether, tetrahydro-furan, dichloromethane or chloroform mainly by electrophilic addition with Markovnikov-type regioselectivity (anti addition).26-28... 

The silver(I) fluoride/bromine and silver(I) fluoride/iodine systems can be exploited for generation in situ and electrophilic addition of "bromine monofluoride and iodine monofluoride to cyclohexene, mcthylenecyclohcxane, styrene, indene, and acenaphthylene.55... 

The reagents for iodine fluoride addition to unsaturated centers are iodine229 or A -iodosuc-cinimide (NIS),221 258 and iodine pentafluoride, hydrogen fluoride,221,258 potassium fluoride, silver(I) fluoride229 278 or ammonium hydrogen difluoride/aluminum trifluoride220 as fluoride ion sources. In addition to the in situ iodofluorinations with iodine monofluoride,l96,22< 227 and (difluoroiodo)methane,194,19 iodofluorination with bis(pyridine)iodonium tetrafluoro-borate219 is described. 

A disadvantage of IC1 is its high oxidation potential and the necessity for carrier iodide addition. Iodine monofluoride ( IF), obtained by reaction of F2 gas with Na I in perfluorinated solvents (Goenen et ai, 1995), seems to be a good alternative, since it can be used directly, without further purification or isolation procedures. 

Aluminum/aluminum iodide Addition of iodine monofluoride to carbon-carbon double bonds... 

Chlorine monofluoride (which is commercially available) acts as a powerful fluorinating and oxidizing agent (e.g. reaction 17.22) oxidative addition to SF4 was shown in Figure 16.13. It may behave as a fluoride donor (equation 17.23) or as a fluoride acceptor (equation 17.24). The structures of [C12F] (17.9) and [C1F2] (17.10) can be rationalized using the VSEPR model. Iodine monochloride and monobromide are less reactive than CIF, but of importance is the fact that, in polar solvents, ICl is a source of I" " and iodinates aromatic compounds. 

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