New synthesis of hydrofluoroethers

Article abstract of DOI:10.1016/S0022-1139(01)00476-6

Polyfluorinated ethers R_fCH₂OR_f react with fluoroethylenes in the presence of SbF₅ catalyst under mild conditions. The reaction of CF₃CH₂OCF₂CF₂H (1a) with terafluoroe

Full text of DOI:10.1016/S0022-1139(01)00476-6

Journal of Fluorine Chemistry 112 &2001) 117±121
New synthesis of hydro¯uoroethers
Viacheslav A. Petrov*
DuPont Central Research and Development, Experimental Station, P.O. Box 80328, Wilmington, DE 19880-0328, USA
Abstract
Poly¯uorinated ethers RfCH2ORf react with ¯uoroethylenes in the presence of SbF5 catalyst under mild conditions. The reaction of
CF3CH2OCF2CF2H &1a) with tera¯uoroethylene rapidly proceeds at ambient temperature and results in high yield formation of
CF3CH2OCF&C2F5)CF2H, along with small amount of CF3CH2OC&C2F5)2CF2H. On the other hand, the condensation of 1a with
tri¯uoroethylene proceeds with formation of CF3CH2OC&CFHCF3)2CF2H as a major product. # 2001 Elsevier Science B.V. All rights
reserved.
Keywords: Hydro¯uoroethers; Electrophilic condensation; Fluoroole®ns; Antimony penta¯uoride
1. Introduction
Lewis acids &AlCl3 or SbF5) only at high temperature [9]. On
the other hand, partially ¯uorinated compounds RfCF2OR
interact with SbF5 under mild conditions. The reaction of
CF3CFHCF2OCH3 with antimony penta¯uoride, results in
rapid decomposition of ether with formation of
CF3CFHC&O)F and methyl ¯uoride [10].
In this study, it is found that ethers RfCH2ORf have much
higher stability towards SbF5 compare to RfCF2OR. For
example, the addition of SbF5 to CF3CH2OCF2CF2H &1a) at
ambient temperature does not result in cleavage of ether, but
leads to the formation of clear homogeneous solution. The
reaction of solution SbF5 in ethers 1a±d and ole®n 2
proceeds under mild conditions resulting in insertion of
¯uoroole®n in C±F bond of di¯uoromethyl group of ether
and formation of compounds 3a±d [11]:
Hydro¯uoroethers became of signi®cant importance in
last few years. Potential commercial applications of these
materials include use as refrigerants, heat transfer ¯uids and
polymerization media [1±3]. Several materials of this type
have been commercialized recently. In general, the synthetic
methods of preparation of hydro¯uoroethers either are based
on either ¯uorination of ethers or utilization of ``building
blocks'' approach. The former includes nucleophilic addi-
tion of alcohols to ¯uoroole®ns [4], electrophilic alkylation
of poly¯uorinated alkoxy anions by reagents such as
&CH3)2SO4 [3,5], radical addition of ethers to ¯uoroole®ns
[6], Lewis acid catalyzed tri¯uoromethylation of poly¯uori-
nated alcohols using CCl4 in anhydrous HF [7] and electro-
philic alkylation of per¯uorinated carbonyl compounds by
alkyl ¯uorides [8].
This paper report a new method of preparation of hydro-
¯uoroethers, based on the condensation poly¯uorinated
ethers and ¯uoroethylenes catalyzed by antimony penta-
¯uoride.
&1)
2. Results and discussion
Detailed analysis of the crude product of the reaction ether
1a and olefin 2 revealed the presence of a few percent of
compound 4. The formation of 4 is result of insertion of
2 mol of olefin into molecule of ether 1a:
The stability of poly¯uorinated ethers towards the action
of strong Lewis acids varies signi®cantly and in general
depends on the degree of ¯uorination and the structure of
ether. For example, per¯uorinated ethers are quite stable to
the action of acids at ambient temperature and react with
* Tel.: ‡1-302-695-1958; fax: ‡1-302-695-8281.
&2)
E-mail address: viacheslav.a.petrov@usa.dupont.com &V.A. Petrov).
0022-1139/01/$ ± see front matter # 2001 Elsevier Science B.V. All rights reserved.
PII: S 0 0 2 2 - 1 1 3 9 & 0 1 ) 0 0 4 7 6 - 6

118
V.A. Petrov / Journal of Fluorine Chemistry 112 02001) 117±121
Table 1
Condensation of polyfluorinated ethers with fluoroethylenes catalyzed by antimony pentafluoride
Entry
no.
Ratio of reactants
&mol)
SbF5
Temperature
Products &yield, %)a
Boiling point &8C)
&mmHg)
&mol%)
&8C) &time, h)
1
2
1a, 2 &3:2)
1a, 2 &1:2)
1b, 2 &1:1)
1c, 2 &1:1)
1d, 2 &1:1)
1e, 2 &1:1)
6a, 2 &3:2)
7a, 2 &1:2)
8a, 2 &3:2)
1a, 9 &1:2)
1b, 9 &1:2)
1a, 11 &2:1)
1b, 11 &2:1)
8a, 11 &3:2)
12b, Zn, C2H5OH
17
17
13
7
25 &12)
25 &12)
3a &76), 4 &trace)
3a &70)b, 4 &7.4)
3b &57.5)
3a 65.2±65.8
4,112±115
90.3±91
3
25 &14)
4
25 &14)
3c &22)
122±126
5
16
6
25 &14)
25 &14)
3d &62)
106±109
98±99, 112
6
3e &42)c, 5 &6.2)
6b &5), 6c &9)
7b &41), 7c &57)
8b &52), 8c &33)
10a &61)
7
5
25 &12)
8
13
17
20
22
10
10
10
±
25 &12)
25 &12)
77.5±77.9, 113.5±114.5
74.8, 99.2
9
10
11
12
13
14
10
25±30 &4)
25±30 &5)
10±35 &4)
10±25 &4)
10±25 &4)
Reflux &2)
114±120
10b &51)
12a &53)
136±143
50±51 &20)
55±56.5 &25)
56±58 &25)
108±110
12b &42)
12c &43)
13 &83)
a Isolated yields.
b Ratio of 3a:4 in crude product 9:1.
c Ratio of 3e:5 in crude product 84:16.
All attempts to increase the yield of this material by increas-
ing the amount of 2 in the reaction mixture failed. The
amount of 4 in all reaction mixtures never exceeded 10%
&see Table 1).
The condensation of ether 1e and 2 leading to the for-
mation of compound 3e as a major product, is accompanied
by formation of noticeable amount of another material,
identi®ed as cyclic ether 5 &NMR and GC±MS):
On the other hand, CF3CH2OCF2H &8a) is more active in the
reaction with 2 giving a mixture of 8b, c in high yield
&Table 1).
The condensation of ethers 1a and b and tri¯uoroethylene
&9) proceeds regioselective, with exclusive attack on CFH±
group of ole®n. The orientation of addition is in a good
agreement with the electrophilic mechanism of the reaction
[12]. However, in both cases the major products are 1:2
adduct of ether and ole®n 9:
&5)
The reaction of ethers 1a and b and 8a with 1,2-dichlorodi-
fluoroethylene &11) rapidly proceeds at ambient temperature
and atmospheric pressure producing corresponding 1:1
adducts &12a±c) in moderate to high yield:
&3)
In general, ethers containing ±OCF3 fragment have lower
reactivity towards 2. The reaction proceeds with formation
of products 6b, c and 7a, c, respectively, although formation
of significant amount polytetrafluoroethylene is observed in
both reactions:1
&6)
Dehalogenation of compound 12b by Zn in ethanol affords
allylic ether 13:
&7)
&4)
It should be pointed out, the reaction of hydrofluoroethers is
limited to fluoroethylenes and hexafluoropropylene does not
interact with either 1a or 1b even at elevated temperature
&508C, 12 h). On the other hand, only ethers containing ±
1 The formation of polytetrafluoroethylene often observed in electro-
philic reactions of tetrafluoroethylene catalyzed by SbF5 proceeds
probably, as a radical process, initiated by oxidative fluorination of olefin
by SbF5.

V.A. Petrov / Journal of Fluorine Chemistry 112 02001) 117±121
119
CH2O± spacer are active in condensation reaction and no
evidence for the formation of condensation product was
found in reaction of C3F7OCFHCF3 and 2 at ambient
temperature in the presence of SbF5.
3. Mechanistic considerations
The regiochemistry of addition poly¯uorinated ethers to
tri¯uoroethylene and chlorotri¯uoroethylene [11] is indica-
tiveofcarbocationicmechanismoftheprocess.Theformation
of corresponding oxonium cations under action of SbF5 on
corresponding ethers has been reported earlier [13]. However,
it should be pointed out that the formation of product 4 was
observedonlyinthereactionof1aand2,butnotinthereaction
between 3a and 2. It may be an indication that compounds 3a
and 4 are formed as a result of consecutive rather then
independent processes. The ®rst step probably, involves the
formation of cation 14 [13]. This step is followed by electro-
philic attack on ole®n to give intermediate 15 &Scheme 1).
Cation 15 can be stabilized by addition of ¯uoride anion
producing 3a or it may rearrange into 16 through 1,3-
migration of ¯uorine [14]. The compound 16 may either
produce 3a through the addition of FÀ or it may react with
second mole of ole®n to give 4 as a ®nal product.
The formation of compound 5 in the reaction of 1e and 2 is
a result of another process. Intermediate 17a &formed as a
Scheme 2.
result of attack of cation 17 [13] on 2) may undergo
cyclization through the electrophilic attack of cationic center
on oxygen of tri¯uoromethoxy group with formation of
‡
cyclic ether 18 and CF3 . Further reaction of 18 with a
second mole of 2 &through the formation of intermediate
cation 19) leads to cyclic ether 5 &Scheme 2).
4. Experimental
4.1. Starting materials
Fluorinated alcohols &used for preparation of 1a±e, 6a, 7a)
tri¯uoroethylene, 1,2-dichlorodi¯uoroethylene ether 8a,
&PCR), tetra¯uoroethylene, hexa¯uoropropene &DuPont)
were commercially available and used without further pur-
i®cation. Poly¯uorinated ethers 1a±e, were prepared using
procedures described in [4,7,13]. SbF5 &Ozark-Mahoning,
99%) was handled inside of dry-box and used without
further puri®cation.
Caution: Both tri¯uoroethylene and tetra¯uoroethylene
are hazardous materials and should be handled by properly
trained personnel. All reactions with these materials should
be carried out inside of barricade!
19F and 1H NMR spectra were recorded on QE-300
&General Electric, 200 MHz) using CFCl3 or &CH3)4Si as
internalstandardandCDCl3 aslocksolvent. Allnewmaterials
were characterized by 19F and 1H NMR. Satisfactory HRMS
Scheme 1.

120
V.A. Petrov / Journal of Fluorine Chemistry 112 02001) 117±121
Table 2
Analytical data for selected products
Compound
19F NMR d &ppm) &J, Hz)
1H NMR d &ppm) &J, Hz)
Analysis or MS found
&calculated)
3a
À75.40 &3F, t, 7); À80.53 &3F, d, 8); À125.51 &1F, dt, 296);
4.50 &2H, q, 8); 6.38 &1H, t, 55)
C, 23.81 &24.02); H, 0.99
&1.01); F, 69.97 &69.64)
À126.23 &1F, dd, 296); À132.31 &1F, dd, 312, 55); À133.54
&1F, dd, 312, 55); À144.00 &1F, br. s)
4
À75.90 &3F, t, 8); À80.07 &6F, m); À116.30 &A:B pattern, 4F,
ddm, 290); À125.60 &2F, dm, 51)
4.37 &2H, q, 8); 6.38 &1H, t, 51)
4.33 &2H, m); 6.21 &1H, dm, 55)
4.32 &2H, m); 4.78 &1H, m)
C, 23.49 &24.02); H, 0.75
&0.76); F, 70.75 &71.23)
C, 21.71 &22.97); H, 0.90
&0.83); F, 67.67 &67.47)
m/e &mixture of isomers):
377.9883 &377.9925)
3ea
5a
À60.75 &2 signals, 3F); À76.12 &3F, t, 8); À81.10 &3F, m);
À124.90 to 127.20 &4 signals, 2F); À141 to 143.5 &4 signals, 2F)
Major isomer: À74.98 &3F); À79.40 &1F, dm, 130); À83.80 &3F, s);
À90.80 &1F, dm, 130); À126.90 &1F, dm, 245); À127.80 &2F, m);
À131.85 &1F, dm, 245); À141.35 &1F, m). Minor isomer: À75.10
&3F); À82.00 &1F, dm, 146); À82.80 &3F, s); À86.75
&1F, dm, 146); À127.80 &1F, dm); À128.80 &2F, m);
À131.85 &1F, dm, 245); À141.85 &1F, m)
7b
À81.92 &3F, t, 10); À88.09 &2F, s); À124.60 &2F, pent, 8); À129.80 4.39 &2H, t, 11); 5.88 &1H, tt, 52, 4)
&2F, s); À138.31 &2F, d, 52)
C, 23.13 &24.02); H, 0.99
&1.01); F, 69.85 &69.64)
m/e: 380.9926
7c
À80.55 &6F, br. s); À122.30 &2F, dd, 290); À123.48 &2F, dd, 290);
À125.20 &2F, s); À138.50 &2F, d, 52); À138.78 &1F, s)
À74.86 &3F, s); À82.28 &3F, s); À129.5 &2F, d, 259);
À145.71 &1F, dm, 60)
4.35 &2H, t, 12); 5.86 &1H, tt, 52, 4)
4.18 &2H, m); 5.65 &1H, dm, 59, 5)
4.14 &2H, q, 10); 4.39 &1H, m, 7)
4.20 &2H, m); 5.0±5.6 &3H, m)
4.15 &2H, m); 5.1 &1H, m)
‡
[380.9960, &M±F) ]
8b
C, 23.34 &24.02); H, 1.19
&1.21); F, 69.78 &68.38)
m/e: 330.9978
8c
À75.11 &3F, t); À82.40 &6F, br. s); À119.10 &2F, dm, 300);
À123.15 &2F, dm, 300)
‡
[330.9992, &M±F) ]
10ba
12ba
12ca
13a
À71 to À73.5 &4 signals, 9F); À75.50 &3F); À204 to À210.50
&4 signals, 3F)
m/e: 395.0114
‡
[395.0117, &M±F) ]
À55 to À66 &2F, m); À72.70 to ±73.90 &4 signals, 6F); À125 to
138 &8 signals, 2F); À125.30; À198.10 &2 signals, 1F)
À64.60 to À65.28 &2F, dm, 173); À74.78; À74.83 &3F);
À131.52; À132.71 &1F, m); À135.03; À139.08 &1F dm)
À73.54; À74.10; À74.85 &6F, m); À88.53 &1F, m); À106.12
&1F, m); À126.15; À137.18 &1F, m); À128.50 &1F dm, 156);
À208.56; À210.12 &1F, m)
C, 21.15 &21.95); H, 0.82
&0.79); F, 54.34 &54.57)
C, 20.98 &21.22); H, 0.90
&1.07); F, 47.11 &47.00)
C, 26.72 &26.94); H, 1.09
&0.97); F, 66.63 &66.96)
4.15 &2H, m); 5.63 &1H, dm)
4.20 &2H, m); 4.92 &1H, dm, 45)
a Mixture of diastereomers.
or elemental analysis were obtained for all new materials.
The ratio of reactants and reaction conditions are given in
Table 1. NMR spectra and analytical data for selected
products are given in Table 2.
ing ether to maintain the temperature inside of reactor at
10±358C. In the end, the reaction mixture is diluted with a
cold 20% solution of HCl; organic layer is separated,
dried over MgSO4 and distilled using a spinning-band
column.
5. General procedure for reaction of ethers with
fluoroolefins
Acknowledgements
5.1. Method A 0tetrafluoroethylene)
The author thanks Dr. F. Davidson for recording and help
in the interpretation of NMR spectra of compound 5 and Dr.
D.D. Khasnis for technical assistance.
A 400 ml Hastelloy shaker tube was charged with 0.2±
0.7 mol of ether 1a±e, 6a, or 7a, 5±17 mol% of SbF5 and
0.1±0.5 mol of 2 and reaction mixture was maintained at
ambient temperature 12±14 h. The reactor was vented. To
remove SbF5 the crude reaction mixture was washed with
cold water. It was dried over MgSO4 and distilled using a
spinning-band column.
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