Addition of trifluoromethanes to fluoroolefins and...

Details Addition of trifluoromethanes to fluoroolefins and... Addition of trifluoromethanes to fluoroolefins and...

2000-03-29

2001-07-17

Siegel, Alan (Department: 1621)

Organic compounds -- part of the class 532-570 series

Organic compounds

Halogen containing

Reexamination Certificate

active

06262320

ABSTRACT:

FIELD OF THE INVENTION
This invention concerns a process for the Lewis acid catalyzed addition of trifluoromethanes across the carbon-carbon double bond of fluoroolefins.
TECHNICAL BACKGROUND
U.S. Pat. No. 5,157,171 discloses a process for the preparation of chlorofluoropropanes of the formula C
3
HCl
2
F
5
by contacting monofluorodichloromethane with tetrafluoroethylene in the presence of modified aluminum chloride catalyst.
U.S. Pat. No. 5,416,246 discloses the rearrangement of dichlorofluorocarbons to gem-dichloro chlorofluorocarbons in the presence of a mixed aluminum halide catalyst.
U.S. Pat. No. 2,462,402 discloses a process for the production of highly halogenated fluoroalkanes which comprises contacting TFE with a polyhalogenated alkane, preferably a methane, containing at least one chlorine atom and no more than two fluorine atoms, in the presence of a polyvalent metal halide catalyst, preferably aluminum chloride.
U.S. Pat. No. 2,462,402 is referred to in the Journal of the American Chemical Society, Vol. 71, pages 979-980 (1949) which discloses reacting CHClF
2
(chlorodifluoromethane) while in the presence of aluminum chloride with TFE produces C
3
HCl
2
F
5
having one less F atom than the sum of fluorine atoms in the reactants. Likewise, CHClF
2
reacting with CTFE yields C
3
HCl
3
F
4
.
Paleta, in a review article “Fluorine Chemistry Reviews”, Vol. 8, page 51 (1977) states: “The ionic addition reactions of fluoromethanes in the presence of aluminum chloride are limited to the monofluoro derivatives only. When in contact with aluminum chloride, both difluorodichloromethane and difluorochloromethane were found to undergo a rapid disproportionation with the formation of monofluorochloromethanes (along with some further compounds) that are able to add to fluoroethylenes”.
The disclosure of each of the previously identified references is hereby incorporated by reference.
SUMMARY OF THE INVENTION
This invention provides a process for the addition of trifluoromethanes of the structure CF
3
X, where X is I, Br, Cl, or H to olefins of the structure YFC═CF
2
, where Y is H, F, Cl or OC
n
F
2n
F, where n is 1,2 or 3 in the presence of Lewis acid catalyst. The process is conducted optionally with agitation, and optionally in the presence of a solvent or diluent that is not reactive in the process. The process affords adducts of the structure CF
3
CFYCF
2
X, if Y is H, F or Cl or its isomer, YCF
2
CF
2
CF
2
X, if Y is OC
n
F
2n
F, where n is 1,2 or 3. Products may further isomerize in the presence of a Lewis Acid catalyst. A preferred Lewis acid catalyst is aluminum chlorofluoride.
This invention further provides a process for the isomerization of R
f
CF
2
CF
2
X′, where R
f
is C
1
-C
12
and where X′ is I or Br, to R
f
CFX′CF
3
, in the presence of a Lewis acid/fluoroolefin catalyst system. A preferred Lewis acid in the catalyst system is aluminum chlorofluoride. The fluoroolefin is C
3
to C
12
and may be cylic or linear.
DETAILED DESCRIPTION OF THE INVENTION
For the compound CF
3
X, where X is selected from the group consisting of I, Br, Cl, and H, the preferred X's are I, Br or H.
In the olefin of the structure YFC═CF
2
, it is preferred that Y is H or F.
Solvents or diluents may be employed in the process of the present invention. The solvent or diluent is selected so that it will not be reactive in the process or lead to the deactivation of the aluminum chlorofluoride catalyst. Suitable solvents or diluents are selected from the group consisting of perfluoroalkanes or perfluorocycloalkanes, for example, perfluorocyclobutane; the cyclic dimer of hexafluoropropene, i.e., the isomeric perfluorodimethylcyclobutanes; perfluoroethers; or perfluoro tertiary amines. Preferred on the basis of its ready availability to those skilled in the art is the cyclic dimer of hexafluoropropene.
The temperature employed in the process of the present invention ranges from about −10° C. to about 180° C. The preferred temperature range is about 0° C. to 150° C.
Reaction time is not critical and ranges from about several minutes to about 24 hours. About 1 to 16 hours, are usually sufficient.
The pressure employed in the reaction is not critical. Autogenous pressures are usually employed.
Where the reaction conditions are heterogeneous, some degree of agitation is often desirable.
The reaction is preferably carried out in the presence of an aluminum halide Lewis acid catalyst, wherein the aluminum halide is a mixed halide containing fluorine and at least one of Cl, Br or I. Preferred catalysts are of the structure AlF
n
Cl
3-n
, wherein n is from 0.05 to 2.95. Preferably n is from 2.5 to 2.95. Fluorinated aluminum chloride catalysts can be prepared by the reaction of AlCl
3
with a fluoroalkane such as CFCl
3
according to the method described in U.S. Pat. No. 5,162,594, column 4, lines 35-57, which is hereby incorporated by reference. Catalysts may be preformed or may be generated in situ.
Since the catalyst is water sensitive, reagents and equipment should be dried before use.
The proportion of catalyst to CF
3
X is preferably about 0.05 to 0.20 mole catalyst per mole CF
3
X.
The process is used to prepare useful chemical intermediates, for example, CF
3
CF
2
CF
2
I by the reaction of CF
3
I with CF
2
═CF
2
. This process offers a particularly straightforward and economical synthesis of this compound. Propyl iodide is useful as an intermediate for preparing higher fluoroalkyl iodides, for example by further reacting them with TFE or, after the elinination of HI from said perfluoroalkyl iodides, the preparation of perfluoroolefins.
Previous syntheses of this compound involved the expensive conversion CF
3
CF
2
CF
2
C(O)OAg+I
2
CF
3
CF
2
CF
2
I.
Primary halides including some of the products of the process of the present invention, i.e., R
f
CF
2
CF
2
X′, where R
f
is C
1
-C
12
and X′ is I or Br, may be rearranged to isomers under some reaction conditions i.e., in the presence of Lewis acid catalyst, preferably aluminum chlorofluoride catalyst plus fluoroolefin co-catalyst, at appropriately high temperatures and residence times to compounds of the type R
f
CFX′CF
3
.


REFERENCES:
patent: 5416246 (1995-05-01), Krespan et al.

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