2
Y. Zhai et al. / Tetrahedron Letters xxx (2015) xxx–xxx
Table 1
Table 3
TFP reaction with HCl in [Bmim]Cl
TFP with HCl reactions by different catalysts
Entry Catalyst
Temperature
°C)
N
2
flow
Yield
(%)
Ratio
2
M
F
3
C
+
HCl
F
3
C
Cl
(
(ml/m)
[
Bmim]Cl
1
1
2
3
CuCl
CuCl
2
/AC
/AC
250
300
250
25–30
25–30
25–30
85
92.3
70.2
91.4 4.2
74.1 22.4
Entry
HCl/TFP ratio
Catalyst
T (°C)
Yield (%)
2
Fluorinated
Cr
Fluorinated
Cr
6.2
61.3
1
2
3
4
5
6
8
9
1.5/1
1.5/1
10% CuCl
10% CuCl
10% CuCl
10% CuCl
10% CuCl
10% CuCl
10% CuCl
10% FeCl
10% SbCl
10% Ru(PPh
160
175
172
172
210
210
210
210
180
210
3.6
7.8
9.0
6.8
2 3
O
4
300
25–30
81.1
9.4
77.1
a
1.96/1
2 3
O
b
3/1
5
6
7
FeCl
FeCl
3
/AC
/AC
300
300 (reuse)
250
25–30
25–30
25–30
4.5
TFP
TFP
28.1 7.3
c
3/1
16.3
—
0.77
—
—
d
3
1.75/1
17.4
13.6
1.1
8.7
1.5
SbCl
5
/Al
2
O
3
1.56/1e
1.98/1
1.98/1
2.02/1
97%
f
2
g
1
1
0
1
5
h
3
)Cl
2
a
b
c
thermal isomerization of the cis isomer. Decreasing the contact
times by adding a carrier gas and lowering the reaction tempera-
ture prevents the undesired thermal isomerization. Indeed, the
selectivity of cis-1233zd steadily increased from 66.0% at 300 °C
to 98.2% at 225 °C, while the total side products decreased from
12.6% to 1.1% (entry 6).
The ionic liquid was reused from entry 2.
Ionic liquid was reused from entry 3.
Ionic liquid was reused from entry 4, trace amount of CF CHCl@CH was
3 2
observed.
d
Ionic liquid was reused from entry 5.
Ionic liquid was reused from entry 6.
Product was determined by GC.
e
f
g
h
1
1
.04% trans-1233zd.
.5% trans-1233zd.
Other catalysts, such as CuCl
FeCl , were investigated, and the results are summarized in Table 3.
Copper(II) chloride performed similarly to copper(I) chloride,
whereas SbCl on aluminum oxide was virtually inactive as a cat-
2 2 3 5
, fluorinated Cr O , SbCl , and
3
5
3
,3,3-trifluoropropene (1223xd), was observed when the HCl to
TFP ratio was increased to 3/1 at 210 °C.
Other metal catalysts such as FeCl , SbCl
much less effective, yielding cis-1233zd and the undesired trans
isomer. The use of Ru(PPh )Cl catalyst gave only trans-1233zd.
Antimony pentachloride gave about 8.7% of cis product along with
alyst for this reaction. Fluorinated chromium oxide gave mostly
trans-1233zd isomers. Iron(III) chloride gave predominately the
cis-1233zd product in low yield, and the catalyst’s reactivity
degraded sharply after 2 min.
In conclusion, we have found the stereoselective addition of HCl
to 3,3,3-trifluoropropyne to yield exclusively cis-1-chloro-3,3,3-tri-
fluoropropene. This reaction can be conducted over a catalyst in
either the gas phase or an ionic liquid. We are currently investigat-
ing the scope of this reaction with various alkynes and HX such as
HF, HBr, HI, HCN. Further studies to elaborate the reaction mecha-
nism are in progress.
2
5 3 2
and Ru(PPh )Cl were
3
2
other multi-chlorinated products. It is known that SbCl
used as a chlorinating reagent for alkynes.
5
can be
9
1
0
Liu and Chang demonstrated the gas phase transformation of
methanol and carbon monoxide over CuCl on activated carbon to
dimethyl carbonate in 63% selectivity. Thus, 10 wt % of CuCl on
activated carbon was prepared using the literature procedure of
Liu and calcined at 300 °C for 4 h. Trifluoropropene and HCl were
mixed in a stainless cylinder in calculated ratios and passed
through the catalyst bed at different temperatures. The results
are summarized in Table 2.
10
Acknowledgments
We gratefully acknowledge the help from Dr. David Nalewajek
and the support from Analytical Group of Honeywell International
Inc. in Buffalo, NY.
In the absence of a carrier gas, the reaction of TFP and HCl
afforded 24.1% of trans-1233zd along with other side products
(
12.6%) at 300 °C (entry 1). The major impurities besides the
trans-1233zd were cis/trans-1,2-dichloro-3,3,3-trifluoropropene
1223xd) and 2-chloro-3,3,3-trifluoropropene (1233xf). Since
References and notes
(
1. (a) Nair, H. K.; Poss, A. J. US Patent 6958424 B1, Oct. 25, 2005; (b) Boyce, C. B.;
Belter, R. K. US Patent 5616819, Apr. 1, 1997; (c) Wang, H.; Tung, H. S. US Patent
Appl. 2008/0103342, May 1, 2008; (d) Elsheikh, M. Y.; Bonnet, P.; Wismer, J. A.
WO 2010/059496 A1, May 27, 2010.
trans-1233zd is the thermo-dynamically favored product com-
pared to the cis isomer, the trans product could be derived from
Table 2
TFP reactions with HCl over CuCl on activated carbon
CuCl
F C
activated carbon
F
C
F
C
F C
3
F3C
+ HCl
3
Cl
3
3
+
+
+
Cl
Cl
Cl
Cl
1
2
3
4
Entry
HCl/SM ratio
Temperature (°C)
N
2
flow (ml/m)
Yield (%)
Distribution
1
2
3
4
1
2
3
4
5
6
2.09/1
1.96/1
2.05/1
1.90/1
2.15/1
2.10/1
300
300
300
300
250
225
0
85
66.0
24.1
14.0
3.5
6.7
1.8
5.9
1.5
0.8
0.5
0.2
0.5
3.9
5.19
6.7
3.2
1.3
0.6
5–10
98.4
98.8
97.1
97.6
78
75.9
85.3
89.5
96.9
98.2
15–20
25–30
25–30
25–30
0.7
The reactions from entry 1 to entry 6 used the same 10% CuCl on AC catalyst in a row; the numbers were analyzed by NMR.