Perfluoroalkyl ethyl alcohols via perfluoroalkyl acetaldehydes

Article abstract of DOI:10.1016/j.jfluchem.2017.07.013

A new route to commercially important perfluoroalkyl ethyl alcohols (RfCH₂CH₂OH) is described. This route involves the addition of perfluoroalkyl iodides to alkyl vinyl ethers using sulfinatodehalogenation chemistry, followed by catalytic hydrogenation of the intermediate mixture of perfluoroalkylacetaldehyde and perfluoroalkylacetaldehyde hemiacetal to the desired alcohol.

Full text of DOI:10.1016/j.jfluchem.2017.07.013

Accepted Manuscript
Title: Perfluoroalkyl Ethyl Alcohols via Perfluoroalkyl
Acetaldehydes
Authors: Sheng Peng, Kenneth G. Moloy
PII:
S0022-1139(17)30305-6
DOI:
Reference:
http://dx.doi.org/doi:10.1016/j.jfluchem.2017.07.013
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9-7-2017
23-7-2017
23-7-2017
Please cite this article as: Sheng Peng, Kenneth G.Moloy, Perfluoroalkyl
Ethyl Alcohols via Perfluoroalkyl Acetaldehydes, Journal of Fluorine
Chemistryhttp://dx.doi.org/10.1016/j.jfluchem.2017.07.013
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Perfluoroalkyl Ethyl Alcohols via Perfluoroalkyl Acetaldehydes
Sheng Penga* and Kenneth G. Moloyb
a Chemours Company, Fluoroproducts, Experimental Station, PO Box 80262, Wilmington, DE 19880-0262
USA
b DuPont Central Research and Development, Experimental Station, PO Box 80328, Wilmington, DE 19880-
0328 USA
* Corresponding author
Graphical Abstract for Peng & Moloy, Perfluoroethyl Alcohols via Perfluoroacetaldehydes, submitted to J
Fluorine Chem.
Highlights

Sulfinitodehalogenation reaction of RfI and ethyl vinyl ether gives aldehyde and hemiacetal addition
products.


Catalytic hydrogenation of this mixture gives the perfluoroalkylethanol in high overall yield.
These alcohols are important intermediates in the commercial production of surfactants and
polymers.
Abstract
A new route to commercially important perfluoroalkyl ethyl alcohols (RfCH2CH2OH) is described. This
route involves the addition of perfluoroalkyl iodides to alkyl vinyl ethers using sulfinatodehalogenation
chemistry, followed by catalytic hydrogenation of the intermediate mixture of perfluoroalkylacetaldehyde
and perfluoroalkylacetal to the desired alcohol.
1. Introduction
Fluorinated alcohols are important intermediates used to manufacture many commercial
products. Among them, fluorinated sulfonamido alcohols of the type RfSO2NHCH2CH2OH (Rf = C8F17) and
perfluoroalkyl ethyl alcohols of the type RfCH2CH2OH (Rf = C4F9 to C14F29) are the most important
commercially available materials of this class[1-5]. For several decades they have been used to
manufacture well-known commercial products such as Scotchguard® and Zonyl® surfactants, and soil,
1

water, and oil repellents. Because products made with perfluorinated chains of length ≥ C8F17 are being
phased out of the commerce, shorter chain alcohols, for example C6F13CH2CH2OH, have become
increasingly important.
Methods to prepare perfluoroalkyl ethyl alcohols are rather limited. Currently, all commercial
methods of preparation use perfluoroalkyl ethyl iodide intermediates, as shown in Scheme 1. The most
common process to convert these iodides to the alcohols uses oleum, wherein the perfluoroalkyl ethyl
iodide is converted to the sulfate ester, which is then hydrolyzed with aqueous sodium sulfite to generate
the alcohol[6].
Scheme 1. Commercial routes to perfluoroalkyl ethyl alcohols.
Solvolysis with formamides is an alternative process, also used commercially, where the
perfluoroalkyl ethyl iodide is treated with N-methylformamide to form an intermediate formate ester that
is then hydrolyzed to give the desired alcohol. Relatively mild conditions are employed for the hydrolysis
process, but the reaction times are long unless forcing conditions are applied. The process also requires
solvent and generates up to ca. 10 mol% olefin (RfCH=CH2) by-product[7,8]. A recently reported route
involves conversion of RfI to a Grignard reagent, followed by reaction with ethylene sulfate at -40 °C[9].
While such a route is obviously not commercially viable, it does perhaps indicate a desire for improved
routes to these valuable alcohols.
Improvements in the overall process could potentially result if a more direct route to these
alcohols from the perfluoroalkyl iodide (RfI) were developed. Additional improvements, such as faster
reaction rates, improved selectivity, and decreased use of hazardous reagents would also be of practical
utility. An alternative process that addresses many of these considerations is depicted in Scheme 2, where
the alcohol is produced by simple hydrogenation of the aldehyde intermediate shown. Catalytic
2

hydrogenation of the aldehyde would be expected to proceed with very high selectivity and at high rates
under mild conditions, and catalysts for this transformation are readily available[10,11].
Scheme 2. Proposed perfluoroalkyl acetaldehyde route to perfluoroalkyl ethyl alcohols.
The key step in this process, then, would appear to be production of the intermediate fluoroalkyl
acetaldehyde. There is literature precedent for the conversion of RfI to RfCH2CHO, for example fluoroalkyl
acetaldehydes of the type CnF2n+1CH2CHO (n > 1) were prepared photochemically from perfluoroalkyl
iodides and enamines in 10-40% yield (Scheme 3)[12].
Scheme 3. Enamine route to perfluoroalkyl acetaldehydes.
These fluoroalkyl acetaldehydes have also been prepared by radical addition of RfI to vinyl acetate,
mediated by zinc or AIBN, giving 1-acetoxy-1-iodo-2-perfluoroalkylethanes in moderate to good
yields[13-16]. This chemistry has been further modified and improved by using either alkali halides or
metal oxides to convert the intermediate 1-acetoxy-1-iodo-2-perfluoroalkylethanes (RfCH2CHIOAc) to the
desired aldehydes in 50-70% yield (Scheme 4)[17].
Scheme 4. Perfluoroalkyl acetaldehydes via radical addition to vinyl acetate.
Radical addition of RfI to vinyl alkyl ethers has also been reported as a route to these fluoroalkyl
acetaldehydes. For example, reaction of RfI with ethyl vinyl ether in the presence of arenesulfides or
areneselenides gives the 1,1-disubstituted intermediates shown in Scheme 5; subsequent treatment with
NBS then provides the desired fluoroalkyl acetaldehydes (Scheme 8)[18]. Another reported method is the
3

reaction of RfI with ethyl vinyl ether in the presence of sodium sulfite and sodium bicarbonate
(sulfinatodehalogenation, Scheme 6)[19-24]. Indeed, quantitative yields in this reaction have been
demonstrated by the in situ conversion to, and isolation of, the hydrazone derivatives. It is notable that
these authors further report the conversion of these aldehydes to the alcohols using NaBH4 reduction[24].
Scheme 5. Perfluoroalkyl acetaldehydes via addition to vinyl ethers.
Scheme 6. Sulfinitodehalogenation route to perfluoroalkyl acetaldehydes.
Comparing these literature methods, photochemistry is not attractive for a large scale
commercial process. The routes using vinyl esters are potentially of interest, but they require two
reactions steps to obtain the aldehyde. In contrast, the sulfinatodehalogenation reaction possesses
some attractive features: direct and high yield aldehyde generation, mild reaction conditions, and
inexpensive reagents. Coupled with the anticipated ease and simplicity of the subsequent
hydrogenation step, the sulfinatodehalogenation route was therefore considered for further
investigation. Herein we report our initial results on this route.
2. Results and Discussion
We first investigated the addition of PFHI (perfluorohexyl iodide, C6F13I) to EVE (ethyl vinyl ether)
following the procedure described by Huang and Lü[21-23]. Thus, PFHI, ethyl vinyl ether, Na2S2O4, and
NaHCO3 in 1:1 CH3CN/H2O were combined and the reaction was monitored by GC and NMR. Consistent
with the literature, GC analysis showed that complete PFHI conversion was achieved within 20 min at 5-
4

10 °C. The original literature report did not report the direct observation or isolation of the aldehyde
products, but instead the isolation of the 2,4-dinitrophenylhydrazone derivatives. In our hands, NMR
analysis of the crude product shows two products, assigned as the desired aldehyde C6F13CH2CHO and the
hemiacetal C6F13CH2CH(OH)(OEt) (Scheme 7); the combined yield of these two species, based on PFHI, is
nearly quantitative. Assuming that the hemiacetal reacts as an aldehyde equivalent, the NMR results are
consistent with the earlier report, where the hydrazones were obtained in 85-97 % isolated yields.
Scheme 7. Sulfinitodehalogenation of vinyl ethers produces aldehyde and hemiacetal mixture.
Crude aldehyde/hemiacetal was isolated from this reaction mixture by solids removal (filtration)
and then simple distillation (vacuum transfer) of the volatiles. This product was then hydrogenated with
5% Ru/C catalyst (3.1 MPa, 85 °C; non-optimized screening conditions). GC analysis showed conversion
of the aldehyde to the desired alcohol C6F13CH2CH2OH, as expected. Surprisingly, however, GC-MS analysis
also showed clear evidence of CH3CN hydrogenation, as shown by the presence of EtNH2, Et2NH, Et3N, and
C6F13CH2CH2NH2. Alkyl redistribution and scrambling is commonly encountered in nitrile hydrogenation.
However, nitrile hydrogenation typically requires much higher temperatures than those employed
here[25]. In addition, supported ruthenium catalysts are preferred for the reduction of aldehydes to
alcohols but are typically not preferred for nitrile hydrogenation. Palladium-, platinum-, and rhodium-
based catalysts are reported to be active for nitrile hydrogenation, but the base metal catalysts nickel and
cobalt are the most commonly used. Nitrile hydrogenation is reported to be effective in the temperature
range 5-100 °C but most literature suggests more forcing conditions and thus a practical range of 80-150
°C[26]. Regardless, our experimental results indicate that acetonitrile is an incompatible solvent for this
hydrogenation. This conclusion led us to investigate alternative solvents in which to conduct the
sulfinatodehalogenation step.
5

Prior reports suggest that appropriate cosolvents for the sulfinatodehalogenation reaction do not
necessarily need to be soluble in or miscible with water. For example, both diethyl ether and
dichloromethane have been reported as solvents for this reaction[19-24]. However, these were not
considered due to their volatility, flammability, and/or toxicity properties[27,28]. The addition of PFHI to
EVE was investigated using methyl t-butyl ether (MTBE) as solvent but this was unsuccessful, giving
recovery only of unreacted PFHI. Ethanol was found to be a good solvent for the sulfinatodehalogenation
step. As observed in with acetonitrile, monitoring the reaction by GC analysis showed rapid and complete
PFHI conversion. The resulting product mixture was filtered and the filtrate was subjected to simple
vacuum distillation. However, in this case NMR (19F, 1H) analysis of the crude, distilled product showed
three, rather than two, fluorine-containing products. Two of these were identified as the expected
aldehyde (C6F13CH2CHO) and hemiacetal (C6F13CH2CH(OH)(OEt)) products already discussed. The third
product was identified as the diethyl acetal C6F13CH2CH(OEt)2[29]. Hydrogenation of this mixture gave the
desired alcohol and complete aldehyde and hemiacetal conversion, but unreacted C6F13CH2CH(OEt)2
remained; the results of multiple experiments indicate that the acetal is inert to hydrogenation under the
conditions tested. Conducting the hydrogenation in the presence of added aqueous H2SO4 in an attempt
to convert the diethyl acetal in situ to hemiacetal and/or aldehyde, followed by subsequent hydrogenation
to the alcohol, was not successful. These results necessitated the further search for a solvent.
THF was next investigated and found to be a suitable co-solvent for both the
sulfinatodehalogenation and hydrogenation reactions.
Replacing CH3CN with THF in the
sulfinatodehalogenation procedure described above gave rapid and quantitative PFHI conversion to the
expected aldehyde and hemiacetal mixture, with no apparent loss of rate or yield. Similarly,
hydrogenation of this crude product (filtration and simple vacuum distillation, then 5% Ru/C) gave smooth
conversion to the alcohol with no by-products.
With these positive results in hand, preliminary improvements were investigated. With respect
to the sulfinatodehalogenation step, it was found that low temperature is essential. As the temperature
6

was raised above 5-10 °C, increasing amounts of a by-product, identified as C6F13H were observed. This
species was not detected (< ca. 1 mol %) at 5-10 °C, but at ambient temperatures (20-30 °C) increased to
represent a 3-4 % yield loss. To minimize solvent use, experiments at higher PFHI/EVE concentrations
were conducted. The previous literature reports used dilute solutions, 0.125 M[23]. We find that the
concentrations can be increased ten-fold (1.25 M) with no detrimental impact on yield. However, reaction
times to complete PFHI conversion increased significantly with increasing concentration, from ca. 20 min
to ca. 5 h for quantitative PFHI conversion at these concentration extremes. In addition, the resulting
product mixture was shifted nearly entirely to the hemiacetal (> 90 mol% hemiacetal, < 10 mol% aldehyde)
at higher starting reagent concentration.
The initial hydrogenation experiments were cursory in nature, and designed simply to
demonstrate the desired conversion of the aldehyde/hemiacetal mixture to the target alcohol. With an
improved preparation of the aldehyde/hemiacetal in hand, the hydrogenation was similarly studied in
further detail. First, detailed analysis of the hydrogenation product showed two impurities, identified as
C5F11CFHCH2CH2OH and C6F13CH2CH2OEt. The partially defluorinated alcohol is likely derived by the formal
elimination of HF from the aldehyde/hemiacetal to give olefin, followed by hydrogenation, as shown in
Scheme 8. Elimination of HF from aldehydes RfCH2CHO has been reported with bases as weak as
pyridine[18]. Our investigations did not show evidence of the formation of olefinic species during the
sulfinatodehalogenation step but small amounts of olefin resonances were observed in the 1H NMR of the
distilled product prior to hydrogenation. Apparently, the combination of elevated temperature and base
(e.g., NaHCO3) are sufficient to give rise to this undesirable species. Removal of excess NaHCO3 and other
salts by water extraction sufficed to eliminate this problem.
Scheme 8. Pathway for products resulting from formal HF elimination.
7

The ether C6F13CH2CH2OEt likely results from hydrogenation of the hemiacetal. Hydrogenation of
hemiacetals to ethers is known and is more prone to occur with supported palladium catalysts, which is
one reason why we originally chose Ru/C catalyst[30,31]. In an attempt to eliminate, or at least reduce,
this undesired product, the hydrogenation was tested in the presence of acid and additional water to
ensure rapid equilibration of the hemiacetal and the aldehyde. Assuming that aldehyde hydrogenation is
faster than hemiacetal hydrogenation, this strategy should shift the product to the target alcohol. This
effort proved successful; hydrogenation of the aldehyde/hemiacetal mixture in the presence of dilute
aqueous H2SO4 (soluble acid) or water plus Amberlyst® 15 (solid acid) resulted in complete hydrogenation
of the mixture to the alcohol and elimination of the ether byproduct.
With the solvent issues seemingly resolved other parameters were briefly investigated. First
examined was the use of nickel catalysts. Raney nickel is commonly used for aldehyde hydrogenation.
However, Raney nickel is very basic and this is borne out by the formation of products resulting from
formal elimination of HF such as C5F11CF=CHCH2OH and C5F11CFHCH2CH2OH. Raney nickel also produced
substantial amounts of the ether C6F13CH2CH2OCH2CH3. Because Raney nickel is incompatible with
aqueous acid, which eliminated the ether formation in the case of the Ru/C catalyst, it was dropped from
consideration. Raney cobalt catalysts are also used for aldehyde hydrogenation but will likely suffer from
the same issues as with Raney nickel, and we have not yet examined them in this system. Finally, although
the initial scouting experiments were conducted at 3 MPa, we have found that with Ru/C catalyst the
hydrogenation proceeds quickly and in high yield at pressures and temperatures as low as 1 MPa and 22
°C, respectively.
In summary, we have demonstrated a new route to commercially important perfluoroalkyl ethyl
alcohols. Further work is obviously required to translate these findings to a true commercial process.
However, at this point the optimum conditions appear to involve the following steps: 1)
sulfinatodehalogenation at 5-10 °C in THF/H2O and 1-1.5 M reagent concentration; 2) water extraction
and optional distillation of the intermediate perfluoroacetaldehyde/hemiacetal mixture; 3) low
8

pressure/low temperature (0.9 MPa, 20-30 °C) hydrogenation in the presence of aqueous acid; 4) recovery
of the product perfluoroalkyl ethyl alcohol in excellent yield by distillation. Further studies are in progress.
For example, we have extended this chemistry to other perfluoroalkyl ethyl alcohols such as
C3F7OCF2CF2CH2CH2OH.
3. Experimental
3.1 General Considerations.
The reagents Na2S2O4, NaHCO3, solvents, Ru/C (5%) and Amberlyst® 15 were obtained from
Aldrich Chemical Company, Milwaukee, Wisconsin. Perfluorohexyliodide (C6F13I) was obtained from the
Chemours Company, Wilmington, DE. Hydrogenation reactions were conducted in a custom reactor of
Hastelloy C construction. A magnetic stir bar of length matching that of the diameter of the reactor
bottom was used for mixing. This design ensured to the greatest degree possible that the heterogeneous
catalyst would be fluidized during the experiment. After loading with reagents and sealing the reactor
was pressure tested with nitrogen and then pressurized with hydrogen. The reactor was brought to the
target reaction temperature using an external heating block with integrated magnetic stirrer. Upon
reaching the target temperature additional hydrogen was added as required for the experiment. Reaction
progress was monitored by pressure drop using a pressure transducer with digital readout. Products were
analyzed by gas chromatography (GC) using flame ionization (FID) and mass spectral (MS) detection.
Product distributions are given as area percent from the FID and are not corrected for response factors.
3.2 Sulfinatodehalogenation: General Procedure.
The perfluoroalkyliodide (RfI, 1 equiv.) and ethyl vinyl ether (1.3 equiv.) are added to a mixed
solvent of water and THF (6:10 volume ratio of water to THF) at 5-10 °C. NaHCO3 (1.4 equiv.)
is added to the reaction mixture, followed by addition of Na2S2O4 (1.4 equiv). Reaction progress
19
is monitored by GC and/or F NMR, and is generally complete in 3-5 hours as judged by the
complete disappearance of RfI. The reaction mixture was filtered while cold. Water is added to
9

the filtrate, the lower layer is separated. This layer consists primarily of a mixture of aldehyde
C6F13CH2CHO and hemiacetal C6F13CH2CH(OH)(OEt), containing THF and some water. This
crude product can be directly hydrogenated or, optionally, it can be vacuum distilled and the
distillate subjected to hydrogenation.
C6F13CH2CHO: 1H NMR (400 MHz, CDCl3) δ 9.81 (1H, s), 3.16 (2H, t, 18 Hz). 19FNMR (376 MHz, CDCl3) δ -
81.3 (3F, t-t, 10.4, 2.2 Hz), -110.5 (2F, m), -122.3 (2F, s), -123.3 (2F, s), -123.5 (2F, m), - 126.6 (2F, m).
1
C6F13CH2CH(OH)(OEt): H NMR (400 MHz, CDCl3) δ 5.08 (1H, t, 5.2 Hz), 3.89-3.81 (1H, m), 3.59-3.52 (1H,
m), 2.56-2.37 (2H, m), 1.23 (3H, t, 6.9 Hz). 19F NMR (376 MHz, CDCl3) δ -81.4 (3F, t, 81.4 Hz), -113.3 (2F,
m), -122.28 (2F, s), -123.3 (2F, s), -124.2 (2F, m), - 126.6 (2F, m)
3.3 Preparation of C6F13CH2CH(OEt)2.
A three neck flask fitted with a stir bar, condenser, and thermocouple was purged with nitrogen and then
charged with C6F13I (8.92 g, 20.0 mmol), ethanol (32 mL), and ethyl vinyl ether (1.8 g, 25 mmol). After
cooling with ice, Na2CO3 (2.35 g, 28 mmol) and then Na2S2O4 (7.32 g, 42 mmol) were added. The reaction
was warmed to room temperature for 15 min and then heated at 60 C for 1.5 h, whereupon complete
conversion of C6F13I was achieved. NMR of the crude product showed ca. 80 mol % diethyl acetal
C6F13CH2CH(OEt)2 and 20 mol % C6F13H. The mixture was filtered and solvent removed from the filtrate by
vacuum. The crude product was vacuum transferred to give 3.33 g product, shown by NMR to consist of
C6F13CH2CH(OEt)2 (91 mol%) and C6F13H (9 mol%).
1
MS (EI): 435 (M+-1), 391 (M+-OEt). H NMR (400 MHz, CDCl3) δ 4.84 (1H, t, 5.2 Hz), 3.64-3.45 (4H, AB),
2.36 (2H, t-d, 18.9 Hz, 5.2 Hz), 1.14 (3H, t, 7.1 Hz). 19F NMR (376 MHz, CDCl3) δ -81.8 (3F, tt, 10.1 Hz, 2.5
Hz), -113.9 (2F, m), -122.5 (2F, s), -123.6 (2F, s), -124.4 (2F, s), - 126.9 (2F, m).
3.4 Hydrogenation of C6F13CH2CHO and C6F13CH2CH(OH)(OEt) in the absence of acid.
10

The hydrogenation reactor was charged with 0.5 g of Ru/C catalyst and 15.0 g of a mixture of C6F13CH2CHO
and C6F13CH2CH(OH)(OEt) in THF. The reactor was brought to 80 °C and 2.1 MPa. After 3.5 h the reaction
was halted and the reaction analyzed by GC and GCMS which showed quantitative conversion to a mixture
of alcohol C6F13CH2CH2OH (74 %), ether C6F13CH2CH2OEt (23 %), and acetal C6F13CH2CH(OEt)2 (3 %).
3.5 Hydrogenation of C6F13CH2CHO and C6F13CH2CH(OH)(OEt) in the presence of Amberlyst® 15 resin.
The reactor was charged with 0.25 g 5% Ru/C, 0.25 g of Amberlyst® 15, 5 mL of water, 5 mL of THF, and
1.0 g of a mixture of C6F13CH2CHO and C6F13CH2CH(OH)(OEt). The hydrogenation was conducted at 80 °C
and 3.1 MPa for 3.5 h. GC analysis showed quantitative conversion to the desired alcohol C6F13CH2CH2OH.
1-butanol and 1,4-butanediol, resulting from hydrolysis and hydrogenation of the THF, were also
observed.
3.6 Hydrogenation of C6F13CH2CHO and C6F13CH2CH(OH)(OEt) in the presence of dilute aqueous H2SO4.
The reactor was charged with 0.25 g of 5% Ru/C, 1.0 g of a mixture of C6F13CH2CHO and
C6F13CH2CH(OH)(OEt), 5 mL of THF, and 5 mL of dilute H2SO4 (pH = 2.2). The hydrogenation was conducted
at 80 °C and 3.1 MPa for 3.5 h. GC analysis showed nearly quantitative formation of the desired alcohol
C6F13CH2CH2OH and only traces of other fluorinated products or products resulting from reaction of the
THF solvent.
3.7 Hydrogenation of C6F13CH2CHO at low pressure
The reactor was charged with 5.0 grams of C6F13CH2CHO (containing < 10 % THF and EtOH) and 0.5 g of
5% Ru/C. The sample was hydrogenated at 50 °C and 0.97 MPa for 7 hours. GC analysis showed 97 %
conversion and 95 % selectivity to C6F13CH2CH2OH.
4. References
[1]
R. E. Banks, B. E. Smart, J. C. Tatlow, Editors, Organofluorine Chemistry:
Principles and Commercial Applications; Springer, 1994.
[2]
T. P. Knepper, F. T. FLange, Editors, Polyfluorinated Chemicals
11

and Transformation Products; ; Springer-Verlag Berlin Heidelberg, 2012.
[3]
[4]
H.-J. Lehmler, Chemosphere 58 (2005) 1471-1496.
R. C. Buck, J. Franklin, U. Berger, J. M. Conder, I. T. Cousins, P. de Voogt,
A. A. Jensen, K. Kannan, S. A. Mabury, S. P. J. van Leeuwen, Integr. Environ. Assess.
Manage. 7 (2011) 513-541.
[5]
[6]
[7]
[8]
[9]
M. P. Krafft, J. G. Riess, Chemosphere 129 (2015) 4-19.
E. Kissa, Surfactant Sci. Ser. 97 (2001) 1-615.
N. O. Brace, J. Fluorine Chem. 31 (1986) 151-174.
N. O. Brace, J. Org. Chem. 58 (1993) 1804-1811.
J. Paterova, M. Skalicky, M. Rybackova, M. Kvicalova, J. Cvacka, J.
Kvicala, J. Fluorine Chem. 131 (2010) 1338-1343.
[10] P. N. Rylander, Catalytic Hydrogenation over Platinum Metals; Elsevier,
2012.
[11] P. N. Rylander, Best Synthetic Methods: Hydrogenation Methods;
Academic Press, 1985.
[12] D. Cantacuzene, C. Wakselman, R. Dorme, J. Chem. Soc., Perkin Trans. 1
(1977) 1365-1371.
[13] N. O. Brace, J. Fluorine Chem. 20 (1982) 313-327.
[14] P. Laurent, H. Blancou, A. Commeyras, Tetrahedron Lett. 33 (1992) 2489-
2492.
[15] P. Laurent, H. Blancou, A. Commeyras, J. Fluorine Chem. 62 (1993) 161-
171.
[16] M. Napoli, A. Scipioni, L. Conte, E. Legnaro, L. N. Krotz, J. Fluorine Chem.
66 (1994) 249-252.
[17] S. Calleja, P. Laurent, H. Blancou, J. Fluorine Chem. 126 (2005) 1493-
1495.
[18] K. Uneyama, K. Kitagawa, Tetrahedron Lett. 32 (1991) 3385-3386.
[19] C.-P. Zhang, Q.-Y. Chen, Y. Guo, J.-C. Xiao, Y.-C. Gu, Chem. Soc. Rev.
41 (2012) 4536-4559.
[20] W. Huang, J. Fluorine Chem. 58 (1992) 1-8.
[21] W. Huang, L. Lu, Y. Zhang, Chin. J. Chem. (1990) 281-288.
[22] W. Huang, L. Lu, Chin. J. Chem. 9 (1991) 174-180.
[23] W. Huang, L. Lu, Y. Zhang, Chin. J. Chem. (1990) 68-74.
[24] J.-Q. Huang, W.-D. Meng, F.-L. Qing, J. Fluorine Chem. 128 (2007) 1469-
1477.
[25] S. Nishimura, Handbook of Heterogeneous Catalytic Hydrogenation for
Organic Synthesis; John Wiley & Sons, 2001.
[26] D. B. Bagal, B. M. Bhanage, Adv. Synth. Catal. 357 (2015) 883-900.
[27] D. Prat, O. Pardigon, H.-W. Flemming, S. Letestu, V. Ducandas, P. Isnard,
E. Guntrum, T. Senac, S. Ruisseau, P. Cruciani, P. Hosek, Org. Process Res. Dev. 17
(2013) 1517-1525.
[28] D. Prat, J. Hayler, A. Wells, Green Chem. 16 (2014) 4546-4551.
[29] H. Zoghlami, I. Chehidi, M. M. Chaabouni, A. Baklouti, J. Fluorine Chem.
125 (2004) 1887-1892.
[30] P. Rylander, Catalytic Hydrogenation in Organic Syntheses; Academic
Press, 1979.
[31] C. J. Forsyth, Editor, Science of Synthesis: Houben-Weyl Methods of
Molecular Transformations; Ethers, 2014; Vol. Vol. 37.
12

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