Addition of hydrogen fluoride to double bonds

Boron trifluoride-diethyl ether complex is used as catalyst in addition reactions of hydrogen fluoride to double bonds. If the alkene is halogenated on the C = C bond, fluorine adds to the carbon that bears the halogen.51... 

In 1959 Bowers176 and Robinson and co-workers 177 independently reported the addition of halogen fluorides to double bonds in steroids.316 The addition of bromine fluoride leads to C6, Cll, and C16 fluorinated steroids.173 Further publications describe many examples of the addition of bromine fluoride to 5,6-unsaturated steroids178 200,212 262,265 270 284-287-309 314 and to 9.11 -, 6,7- or 11,12-unsaturated steroids.209 210 281,695 An example is the bromofluorination of 3/ -acetoxyandrost-5-en-17-one (15) with aqueous hydrogen fluoride and A-bromosuc-cinimide.262 In addition to the main product, the 5a-bromo-6/I-fluoro derivative (58%), three... 

The addition of hydrogen fluoride to the double bonds of chlorinated alkenes in the presence of an aluminum trifluoride catalyst is effective and has found broad synthetic application (Table 2). It proceeds so effectively that it is sometimes used to remove fluoroalkenes in crude product mixtures by adding hydrogen fluoride in this way.27 28... 

These compounds are usually prepared by addition of hydrogen fluoride to a double bond or by the replacement of chlorine by fluorine in the presence of a metal fluoride catalyst.146 The trick is finding the catalyst and conditions that will give the desired selectively in high yield. An outstanding example is (3.1) ... 

Exercise 10-25 Calculate the AH° values for initiation and chain-propagation steps of radical addition of hydrogen fluoride, hydrogen chloride, and hydrogen iodide to an alkene. Would you expect these reagents to add easily to double bonds by such a mechanism ... 

Oxidation and hydrolysis of nitroso compound 5, readily available from the addition of nitrosyl fluoride to perfluoro(2-methylprop-2-enoyl) fluoride, leads to the corresponding alcohol 6.7 Alternatively, double bonds arc hydroborated and subsequently treated w ith hydrogen peroxide to yield the alcohol, c. g. conversion of compound 7 into Ihc two-product 8 (exoiendo 86 14).8... 

Any of the four hydrogen halides can be added to double bonds.The compounds HI, HBr, and HF add at room temperature. The addition of HCl is more difficult and usually requires heat, although HCl adds easily in the presence of silica gel. The reaction has been carried out with a large variety of double-bond compounds, including conjugated systems, where both 1,2 and 1,4 addition are possible. A convenient method for the addition of HF involves the use of a polyhydrogen fluoride-pyridine solution.When the substrate is mixed with this solution in a solvent such as THF at 0°C, alkyl fluorides are obtained in moderate-to-high yields. 

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... 

When chlorine is added to olefinic double bonds in the presence of hydrogen fluoride and aluminum trifluoride as catalyst addition, substitution and isomerization occurs17-25-26. Detailed investigations have been undertaken to elucidate the reaction pathways and the influence of the catalyst system on the prod uct distribution in the case of tetrachloroethene and chlorine.17... 

Terminal alkenes with at least three fluorine atoms attached to the double bond react with ammonia to yield carbonitriles. This proceeds via addition of ammonia and subsequent elimination of two equivalents of hydrogen fluoride. In the case of trifluoroethene or halotri-fluoroethencs the resulting monofluoroacctonitriles trimerize to give the respective... 

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