Defluorination of homologous chlorofluoroethers to chlorofluoroacetates

Article abstract of DOI:10.1016/S0022-1139(02)00321-4

The research was focused on the defluorination of chlorofluoroethers to corresponding esters using porous aluminum fluoride (PAF) or MF_n/PAF. In the work up process, the product was easily separated from the reagent. Thus, the reaction would be a practical preparation method for polyfluorinated esters. Trifluoromethyl chlorodifluoroacetate was obtained by the reaction of 1,2-dichlorotrifluoroethyltrifluoromethyl ether with fuming sulfuric acid in 49% yield.

Full text of DOI:10.1016/S0022-1139(02)00321-4

Journal of Fluorine Chemistry 120 (2003) 131–134
Defluorination of homologous chlorofluoroethers to chlorofluoroacetates
Heng-dao Quana, Masanori Tamuraa, Ren-xiao Gaob, Akira Sekiyaa,*
aNational Institute of Advanced Industrial Science and Technology (AIST), Tsukuba Central 5, 1-1-1 Higashi, Tsukuba, Ibaraki 305-8565, Japan
bResearch Institute of Innovative Technology for the Earth (RITE), c/o AIST, Tsukuba Central 5, 1-1-1 Higashi, Tsukuba, Ibaraki 305-8565, Japan
Received 1 August 2002; received in revised form 29 October 2002; accepted 11 November 2002
Abstract
The research was focused on the defluorination of chlorofluoroethers to corresponding esters using porous aluminum fluoride (PAF) or
MFn/PAF. In the work up process, the product was easily separated from the reagent. Thus, the reaction would be a practical preparation
method for polyfluorinated esters. Trifluoromethyl chlorodifluoroacetate was obtained by the reaction of 1,2-dichlorotrifluoroethyltrifluor-
omethyl ether with fuming sulfuric acid in 49% yield.
# 2002 Elsevier Science B.V. All rights reserved.
Keywords: Porous aluminum fluoride; Defluorination; Chlorofluoroether
1. Introduction
Previously we reported that porous aluminum fluoride (PAF)
was used successfully in preparing methyl chlorodifluoroa-
cetate (3) from 1,2-dichloro-1,1,2-trifluoro-2-methoxyethane
(1) [8,9].
Here, we will report the detail investigation of the defluor-
ination using various types of ethers and reagents and show
the application scope of this method.
The polyfluorinated esters have been considered to be
possible substitutes of SF6 or CF4 in semiconductor man-
ufacture [1]. Also fluorinated esters are candidates for
electrolyte of lithium rechargeable battery [2].
To date, a few literatures have reported on their prepara-
tions. Mainly there are two ways. One is the preparation of
the esters of chlorofluoroacetic acid by treatment of corre-
sponding ethers, CHClFCF2OR, with concentrated sulfuric
acid or fuming nitric acid [3,4]. On this way, fluorine atoms
attached to carbon which also bears an alkoxy group are
known to be labile to electrophilic reagents. This kinds of
ethers are readily hydrolyzed in concentrated sulfuric acid,
thus would give a route to esters of fluorinated carboxylic
acids [5]. However, the separation of product is difficult to
handle in the process. The other is the reaction of fluorinated
carbonyl compounds with ethanol. The fluorinated carbonyl
compounds were obtained by treating polyfluoroalkyl ethers
with Lewis acid, such as ZnCl2, BF3–Et2O and AlCl3 [6,7].
In our research, we devised and prepared new reagents
based on their insolubility in water and in organic solvents
for exploiting the defluorination process of chlorofluor-
oethers. Though the reagents contains OH group on their
surface, they are inert for HF and HCl media, thus can
be easily separated from the reaction medium. The OH
group would be the source of oxygen in the defluorination.
2. Results and discussion
2.1. Defluorination of CH3OCFClCF2Cl (1) to
CF2ClCOOCH3 (3)
Based on our previous report about the defluorination of 1
to 3 on CrF3/PAF and CoF2/PAF [8], further we attempted to
use various metal fluorides supported on PAF to investigate
the defluorination of 1 to 3. The reaction scheme and results
of the reaction of 1 with different kinds of metal fluorides
were summarized in Scheme 1 and Table 1, respectively.
Although metal fluoride had an effect on this reaction, the
yield of 3 was less than 50%.
In order to investigate the effect of Lewis acid strength on
the surface of PAF to the reaction, PAF was treated by
gaseous fluorine in advance and used in the reaction to
replace PAF, the yield of 3 increased from 33 to 54%
(Table 1). This might be attributed to that fluorination
increases acid strength of residual hydroxyl groups on
PAF surface [10–12]. The possible mechanism is shown
in Scheme 2.
* Corresponding author. Tel.: þ81-298-61-4570; fax: þ81-298-61-4570.
E-mail address: akira-sekiya@aist.go.jp (A. Sekiya).
0022-1139/02/$ – see front matter # 2002 Elsevier Science B.V. All rights reserved.
PII: S 0 0 2 2 - 1 1 3 9 ( 0 2 ) 0 0 3 2 1 - 4

132
H.-d. Quan et al. / Journal of Fluorine Chemistry 120 (2003) 131–134
Scheme 1.
Table 1
Reaction of CH3OCFClCF2Cla
Entry Reagent
Reaction
Products yield (%)b Recovery
temperature
(8C)
of 1 (%)
2
3
Scheme 3.
1
2
NiF2/PAF
NiF2/PAF
FeF2/PAF
FeF2/PAF
ZnF2/PAF
MgF2/PAF
SbF3/PAF
SbF3/PAF
PAF
200
150
200
150
150
150
200
150
200
15
24
30
30
38
2
2
0
0
10
40
41
30
18
36
29
33
54
84
3
0
enhanced acid center strength. The reaction of 2 with
SbF5/PAF gave the ester 3 successfully although SbF5 itself
caused decomposition of 2. Compound 3 was obtained in
67% yield by the reaction at 200 8C. The process can be
explained that SbF5 impregnated on PAF increased the
strength of Lewis acid and is advantageous to abstracting
fluorine from a C–F bond to give intermediate hemiacetal.
Therefore, PAF absorbing SbF5 makes the transformation
from 2 to 3 possible. With above reagent, the defluorination
of chlorofluoroethers is now accomplished in one clean
step. However when reaction is carried out about 300 8C,
most of starting material decomposed to CH3Cl and
FCOCF2Cl.
4
24
11
63
1
5
6
7
46
58
12
5
8
10
0
9c
10d
11e
PAF treated by F2 200
AlFm(OH)3Àm 180
2
3
2
a From entries 1–8, reaction time 1 h, starting material (1) about
2 mmol, and reagent 2 g for each reaction, Ni, Sb, Fe, Zn and Mg in
catalyst 5 wt.%.
b From entries 1–11, the by-products are CH3Cl and FCOCF2Cl.
c Reaction time 1 h, (1) about 2.0 mmol, reagent 1.2 g.
d PAF (1.2 g) was treated by 2 mmol gaseous fluorine in advance.
e Reagent AlF3Á3H2O was treated under 300 8C for 10 h, and about 1 g
was used in each reaction.
2.3. Defluorination of CF3OCFClCF2Cl (5) to
CF3OCOCF2Cl (6)
As described in the previous paper [8], AlFm(OH)3Àm
gave 3 in much better yield than PAF (Table 3). Probably, the
amount of OH in AlFm(OH)3Àm is larger than in PAF, so
defluorination proceeded predominately to give 3 in good
yield.
To our knowledge, the defluorination of RfOCFClCF2Cl
to CF3OCOCF2Cl is not reported yet. In fact, the defluor-
ination of 1,2-dichlorotrifluoroethyltrifluoromethyl ether
(5), where –CH3 of 1 was replaced by –CF3, can not be
carried out using above reagents (Table 3). In our research, 6,
as a new compound, was obtained by reaction of 5 with
fuming sulfuric acid at 200 8C (Scheme 4). The results under
different temperature were shown in Table 4, which indi-
cated the substrate decomposed and the yield of 6 decreased
when reaction temperature is over 200 8C.
For promoting the yield of 6, the nitrogen was filled into
vessel with substrate to increase the reaction pressure. The
results were shown in Table 5 which indicated the yield of 6
increased from 38 to 49% with the pressure increasing from
0.1 to 3.9 MPa, but too high pressure is not advantageous to
the formation of product (entry 5 in Table 5). It is assumed
2.2. Defluorination of CH3OCF2CF2Cl (2) to
CF2ClCOOCH3 (3)
The defluorination of 2 to 3 was examined with various
reagents (Scheme 3) and the results were shown in Table 2.
When a-chlorine of 1 was replaced by fluorine to form 2,
the defluorination of 2 did not occur by using PAF, PAF
treated by gaseous fluorine, porous calcium fluoride (PCF),
AlFm(OH)3Àm and CoF2 þ CrF3/PAF (Table 2). In order to
prompt coordination of reagent with fluorine in a-position,
strong Lewis acid, SbF5, was impregnated on PAF to
Scheme 2.

H.-d. Quan et al. / Journal of Fluorine Chemistry 120 (2003) 131–134
133
Table 2
Reaction of CH3OCF2CF2Cla
Entry
Reagent
2 (mmol)
Reaction condition
Product yield of 3 (%)
Recovery of 2 (%)
Temperature (8C)
Time (h)
1
2
PAFb
2.0
2.9
2.0
2.0
2.1
2.1
2.1
2.1
2.0
2.6
2.0
200
200
200
200
100
200
300
300
200
200
300
2
2
2
1
2
2
1
3
2
2
2
0
0
100
100
100
100
100
97
48
20
0
PAF treated by F2
PCFc
3
0
4
AlFm(OH)3Àm
CoF2 þ CrF3/PAF
CoF2 þ CrF3/PAF
CoF2 þ CrF3/PAF
CoF2 þ CrF3/PAF
SbF5
0
5d
6d
7d
8
0
0
0
0
9
0
10d
11d
SbF5/PAF
67
1
3
SbF5/PAF
5
a Reaction reagent about 1 g for each reaction; by-products from entries 9–12: CH3Cl and FCOCF2Cl.
b Porous aluminum fluoride.
c Porous calcium fluoride.
d Co, Cr and Sb 5 wt.% in reagent, respectively.
Table 3
Reaction of CF3OCFClCF2Cl with different reagentsa
Entry
Substrate
Reagent
Reaction condition
Recovery of substrate (%)
Temperature (8C)
Time (h)
1
CF3OCFClCF2Cl
CF3OCFClCF2Cl
CF3OCFClCF2Cl
CF3OCFClCF2Cl
PAF (treated by F2)
SbF5/PAF
200
200
300
300
1
1
100
95
82
0
2
3
4b
SbF5/PAF
SbF5/PAF
2
10
a Substrate (2 mmol) and reagent (1.5 g) for each reaction; Sb in reagent 5 wt.%.
b Main products: CF2ClCOF, CF3H.
3. Experimental
3.1. Chemicals
Compounds 1 and 2 are prepared according to literature
[8]. Anhydrous hydrogen fluoride (AHF) was obtained from
Morita Chem. Ind. Co Ltd., Japan. SbCl5 was from Wako
Pure Chemical Industries Ltd., Japan. Trifluoromethyl tri-
fluorovinyl ether (4) purchased from SynQuest Lab. Inc.
Surface area and pore volume (Vs) of PAF were 75 m2/g and
0.3 cm3/g, respectively [8].
Scheme 4.
that the high pressure liquefies the substrate to enhance the
reaction, whereas the reaction occurs at the interface
between liquid fuming sulfuric acid and gaseous 5 under
low pressure.
Table 4
Yield of 6 under different reaction temperatures
Table 5
Yield of 6 under different reaction pressures
Entry
Reaction
Yield of
Recovery
By-product
(%)
temperature (8C)
6 (%)
of 5 (%)
Entry
Reaction
Yield of
Recovery of
By-product
(%)
pressure (MPa)
6 (%)
5 (%)
1
2
3
4
5
6
100
150
180
200
220
250
Trace
9
94
83
67
45
17
3
0
Trace
1
2
3
4
5
0.1
1.1
2.1
3.9
7.9
38
43
47
49
43
45
37
30
24
20
9
9
9
8
7
23
38
18
6
4
9
3
0
Reaction conditions: 1.3 mmol CF3OCFClCF2Cl; reaction time 5 h;
amount of fuming sulfuric acid: 3.2 g.
Reaction conditions: 1.3 mmol CF3OCFClCF2Cl; reaction time 5 h;
amount of fuming sulfuric acid: 3.2 g.

134
H.-d. Quan et al. / Journal of Fluorine Chemistry 120 (2003) 131–134
3.2. Instrument
1H NMR and 19F NMR. The amount of each product was
calculated from NMR results.
1H NMR and 19F NMR were recorded on JNM-EX270
(JEOL, 270 MHz) at 25 8C with (CH3)4Si and CFCl3,
respectively, as internal reference in CDCl3 as a solvent.
FT-IR spectrometer (FT/IR-620, Japan Spectroscopic Co
Ltd.) was used for measuring product in vacuum line.
GC–MS was a Hewlett-Packard 5790 series system
equipped with a Jet Separator for the 5890A GC. The
capillary column was Pora plot Q with 0.32 mm i.d. and
25 m length from J&W Scientific Inc. The operation con-
dition of GC is as follows; column temperature 80 8C for
2 min and heated for 20 min at a rate of 10 8C/min; detector
temperature 200 8C; carrier gas, ꢀ1 cm3 He/min; split ratio
45:1; sample size 1.2 ml; pressure 50 kPa.
3.3.4. Preparation of 5
Compound 5 was prepared by the reaction of 4 with
equimolar amount of gaseous chlorine. Twenty millimoles
of 4 and same amount of gaseous chlorine were introduced
to 500 ml glass reactor cooled to À196 8C. The reactor was
allowed to warm up from À196 8C to room temperature
during 5 h. The product (99% in yield) was determined
by GC–MS, 1H NMR and 19F NMR. The data of MS
and NMR chemical shifts of 1 are listed as follows; MS:
m/z: 69, (þ)CF3; 85, (þ)CClF2; 115, (þ)CF3OCFCl; 201,
(þ)CF3OCFClCF2. 19F NMR: d (ppm), –55.05 (d, 3F); d
(ppm), À71.00 (dd, 2F); d (ppm), À77.89 (m, F).
Products were handled in glass and metal vacuum line
system. Amounts and molecular weight of products were
determined by measuring the sample pressure under a
certain volume in the vacuum line.
3.3.5. Synthesis of 6
Fuming sulfuric acid (3.2 g) was placed in a stainless steel
vessel with 85 cm3 volume, the reactor was cooled to
À196 8C. Then 1.3 mmol of 5 was transferred to reactor
and heated to 200 8C and keep for 5 h at the temperature.
Products were transferred to a trap (À196 8C), and their
amount was measured using vacuum line after separation
(À90 and À196 8C). Finally the products were analyzed by
FT-IR and NMR, and the yield was determined by 19NMR.
For 6, a new compound, spectroscopic data were listed as
follows; 19F NMR: d (ppm), À58.73 (s, 3F); d (ppm),
3.3. Reaction procedure
3.3.1. Preparation of MFn/PAF
MFn/PAF with different metal fluorides supported on PAF
was prepared by following procedure: The PAF was dehy-
drated by heating at 300 8C for 10 h and then impregnated to
a sufficient amount of salt solution overnight. The amount
of metal chloride in the solution was adjusted to give final
metal loading to 5 wt.%. The saturated support was dried
at 120 8C for 2 h and 200 8C for 2 h. The dried pellets
were packed on Inconel alloy reactor and fluorinated by
N2/AHF ¼ 1 : 1 (100 ml:100 ml) at 200 8C for 2 h, then
pure AHF at 200 8C for 2 h and 300 8C for 2 h. Finally
remaining AHF on the MFn/PAF was washed by nitrogen.
The prepared MFn/PAF is used to fluorination procedure.
À65.55 (s, 2F). FT-IR data shows C¼O peak at 1847 cmÀ1
.
Acknowledgements
We gratefully acknowledge the support of this investiga-
tion by New Energy and Industrial Technology Development
Organization (NEDO) of Japan.
References
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with 80 cm3 volume, then reactor was cooled to À196 8C
and 2 mmol of gaseous fluorine was introduce to the reactor.
The reactor was allowed to warm up slowly to 20 8C over-
night. Unreacted gaseous fluorine was pumped out.
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