Halogen fluorides, addition

The combination of A/-halosuccinimides with polyfluorinated ammonium salts, in particular A/-halosuccinimide-triethylamine trisfhydrogen fluoride)42 (Method C), is convenient and effective for the halofluorination of alkenes. These easy-to-handle reagents allow work to be carried out at room temperature in conventional glass apparatus, while Olah s reagent requires polyethylene equipment. The reaction of various alkenes with A -halosuccinimide-triethylamine trisfhydrogen fluoride) in dichloromethane or diethyl ether at 0 C is complete within 3-5 hours giving the halogen fluoride addition products in 70-95% yield. 

There are many examples of halogen fluoride addition to double bonds in steroids, but primarily the addition of bromine fluoride has been investigated (see Section 1.2.1.3.2.)- Nevertheless, there are some examples of the addition of chlorine fluoride in the preparation of fluorinated pregnane systems, " " ° ° e.g. the chlorofluorination of pregna-1.4,9(l l)-triene-3,20-dionc (5). ... 

Water reacts violently with aH halogen fluorides. The hydrolysis process can be moderate by cooling or dilution. In addition to HF, the products may include oxygen, free halogens (except for fluorine), and oxyhalogen acids. 

Addition of Halogen Fluorides to Unsaturated Systems by Andrew E. Feiring... 

Reagent combinations lor additions of the halogen fluorides to cyclohexene to form trans 1 halo 2 fluorocyclohcxane (equation 1) are shown in Table 1... 

Table 2. Products of Addition of Halogen Fluorides to Norbomene...

Additions of the halogen fluorides to unsaturated steroids [62, 95, 96, 97, 98, 99] and carbohydrates [62, 75] are well known Typical reagent combinations include l,3-dibromo-5,5-dimethylhydantoin (DBH) or the Af-halosuccinimides with hydrogen fluoride Reversal of the expected regiochemistry can be observed with certain steroidal olefins [JOO, 101] (equation 7)... 

Additions of halogen fluorides to the more electrophilic perfluonnated olefins generally require different conditions Reactions of iodine fluoride, generated in situ from iodine and iodine pentafluoride [62 102 103, /05] or iodine, hydrogen fluoride, and parapeiiodic aud [104], with fluormated olefins (equations 8-10) are especially well studied because the perfluoroalkyl iodide products are useful precursors of surfactants and other fluorochemicals Somewhat higher temperatures are required compared with reactions with hydrocarbon olefins Additions of bromine fluoride, from bromine and bromine trifluonde, to perfluonnated olefins are also known [lOti]... 

More general procedures for additions of halogen fluorides to highly fluori-nated olefins involve reactions with a source of nucleophilic fluoride ion, such as an alkali metal fluoride, in the presence of aposttive halogen donor [62 107, lOff, 109, 110, 111] (equations 11 and 12) These processes are likely to occur by the generation and capture of perfluorocarbamonic intermediates Tertiary fluormated carbanions can be isolated as cesium [112], silver [113], or tns(dimethylamino)sul-... 

With nitriles, products from addition of one or two equivalents of halogen fluoride can be obtained [725, 726, 127, 128] (equations 25 and 26) on reaction with chlorine fluoride or bromine and an alkali metal fluoride. 

Blends of perchloryl fluoride with halogen fluorides are homogeneous and stable. When these are used as storable liquid oxidizers for rocket propulsion, the halogen fluoride usually confers hypergolicity, increased density, and lowered vapor pressure whereas the perchloryl fluoride provides oxygen needed for efficient combustion of carbon in the fuel or of certain metal additives. The mixtures are thermally stable and their... 

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 addition of halogen fluorides to C = C bonds in steroids is affected by steric crowding to a greater extent than by electronic factors so that the products may be of the anti-Mar-kovnikov type. In several instances the orientation of the bromine monofluoride addition was shown to depend on reaction conditions resulting cither in 6/ -bromo-5a-fluoro- or 5a-bromo-6/i-fluorosteroids.33... 

In contrast to other halogens, the addition of fluorine is predominantly syn. This is compatible with the formation and rapid collapse of a 2-fluorocarbocation-fluoride tight ion pair [Eq. (6.31)]. Extra stabilization for the 2-fluorocarbocation, as in stilbene, decreases stereoselectivity this mechanism also accounts for the formation of 1,1,2-trifluoro compounds [Eq. (6.32)] and solvent incorporation ... 

Reactions of the halogen fluorides with other unsaturated functional groups are generally reported only with highly fluonnated substrates Hexafluorobenzene and derivatives [ 1)8] and octafluoronaphthalene [119] react with mixtures of bromine and bromine trifluoride by 1,4 addition of fluorine followed by addition of bromine fluonde across a remaining double bond (equation 22)... 

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