ASKHAM FREDRIC (US)
| US3429935A | 1969-02-25 | |||
| US5233074A | 1993-08-03 |
| 1. | A method which comprises reacting C6F5MgY in which Y is F, Cl, Br, I with a halogenating agent to produce a halopentafluorobenzene which has the formula C6F5X in which X is a chlorine, bromine or iodine. |
| 2. | The claim 1 method in which the halogenating agent is bromine, chlorine, iodine, carbon tetrachloride, carbon tetrabromide, chloroform, bromoform, or an nbromo or nchloro succinamide. |
| 3. | A method which comprises reacting C6F5MgY in which Y is F, Cl, Br, I with bromine to produce bromopentafluorobenzene. |
| 4. | A method for converting hexafluorobenzene (C6F6) to bromopentafluorobenzene (C6F5Br) which comprises: (i) converting C6F6 to C6F5MgY in which Y is F, Cl, Br, I , and (ii) reacting saidC6F5MgY of step (i) with a halogenating agent in a noninterfering solvent, to provide a reaction mixture containing bromopentafluorobenzene in solution in said solvent. |
| 5. | The claim 4 method further comprising: (iii) isolating said bromopentafluorobenzene from said step (ii) reaction mixture. |
| 6. | The claim 4 or claim 5 method in which said step (ii) noninterfering solvent is a 2 to 10 carbon atom hydrocarbon or a halogenated hydrocarbon. |
| 7. | A method which comprises (i) reacting C6F6 with ethyl magnesium bromide in a medium comprising ethyl ether and tetrahydrofuran to produce C6F5MgBr in solution in said medium; (ii) reacting said C6F5MgBr with bromine wherein C6F5Br is produced. |
| 8. | The claim 7 method further comprising (iii) isolating said C6F5Br produced in step (ii). |
| 9. | The claim 8 method further comprising: (iv) reacting said C6F5Br isolated in step (iii) with nbutyl lithium to convert said C6F5Br to C6F5Li. |
FIELD OF THE INVENTION This invention relates to the preparation of certain fluoroaromatic compounds and to related boranes and borates.
More particularly, the invention relates to the preparation of bromopentafluorobenzene from hexafluorobenzene and to bromopentafluoro boranes and borates.
BACKGROUND OF THE INVENTION Various metallocene olefin polymerization catalysts comprise a pentafluorophenyl group frequently derived from expensive bromopentafluorobenzene. Accordingly, there is a need for a cost-effective method for converting readily available hexafluorobenzene to bromopentafluorobenzene.
Pentafluorobenzene magnesium halides (Grignard reagents) are known. Repress, et al. J. Orpanometallic Chem. (1969) 18:263-274 and Repress, et al., J.
Orpanometallic Chem. (1969) 18:191-195 and United States patent 5,362,423. This synthesis is illustrated by Equation 1: C6F6 + 2 EtMgBr FeCi2 THF/Et2O C6F5MgX + MgX2 + gases (1) (Prior Art) in which the three X's indicate two bromine atoms and one fluorine atom. The distribution of the bromine and fluorine atoms between the Grignard and the magnesium salt is not presently known.
SUMMARY OF THE INVENTION Pursuant to the invention bromopentafluorobenzene is synthesized by quenching a pentafluorobenzene magnesium halide with a halogenating agent, preferably bromine.
DETAILED DESCRIPTION OF THE INVENTION In a specific embodiment, this invention entails reaction of the C6F5MgX Grignard (see Equation 1) preferably in the vessel in which it is produced, with a halogenating agent, heat or in solution, in a non- interfering solvent to produce bromopentafluorobenzene.
In generic embodiments of the invention, any Grignard reactant is used in the Equation 1 reaction which has the formula RMgY in which R is a hydrocarbyl radical containing a beta-hydrogen and Y is any halogen, i.e., fluorine, chlorine, bromine or iodine. CF + 2 RMgY FeCi2 66 THF/Et2o THF/Et2 0 C6F5 MgY + MgY2 + gases (2) In the formula RMgY, Y is halogen, and preferably bromine or iodine and R is a C1 to C20, and preferably a C2 to C10, hydrocarbyl group such as, for example ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, including their branched chain isomers such as, for
example, isopropyl, sec-butyl, tert-butyl, isobutyl, isopentyl, and cyclic alkyls such as for example, cyclohexyl and the like. The C6F5 MgY product is quenched, preferably in the Equation 2 reaction mixture, with a halogenating agent, heat or in solution in non- interfering, preferably a hydrocarbon or chlorinated hydrocarbon solvent to produce a first reaction mixture containing bromopentafluorobenzene. Useful halogenating agents include elemental bromine chlorine and iodine, carbon tetrachloride, carbon tetrabromide, chloroform, bromoform, and n-bromo or n-chloro succinamide.
Elemental bromine is preferred.
The halogenating agent is added in an amount at least stoichiometric with respect to the pentafluorophenyl magnesium bromide. Preferably, the halogenating agent is added in an amount within ninety (90%) percent of the stoichiometric amount.
Suitable halogenating agent solvents are straight or branched chain, five to ten carbon atom, aliphatic hydrocarbons, benzene, toluene, and two to ten carbon atom halogenated aliphatic hydrocarbons. Methylene chloride is preferred.
EXAMPLE 1 In a 2 1, N2 purged flask were combined hexafluorobenzene (145 g), FeCl2 (0.8 g) and THF (600 ml).
The solution was cooled to 0-50C, and ethyl magnesium bromide (3.12 M in Et2O, 500 ml) was then added dropwise.
After the addition was complete, the reaction mixture was stirred for one-half hour. A solution of bromine (125 g) in methylene chloride (250 ml) was then added dropwise to the cold (0-5"C) reaction mixture. After stirring 15 minutes, 4 N HCl was added until all solids were dissolved. The two phases were separated and the organics were washed sequentially with water, aqueous sodium bicarbonate and brine. After drying over sodium sulfate, the mixture was distilled providing 160 g of C6F5Br (83% yield).
The reaction mixture may also be reacted directly after removal of methylene chloride and otherwise without isolation of the C6F5Br with butyl lithium to produce C6F5Li which, in turn, is reacted with BCl3 or BF3 to produce (C6F5) 3Br.
Next Patent: PROCESS FOR THE CONTINUOUS PRODUCTION OF NEOPENTYL GLYCOL