Alternative synthetic routes to hydrofluoroolefins

Article abstract of DOI:10.1016/j.jfluchem.2015.08.001

A series of hydrofluoroolefins with -CF=CH₂, -CH=CHF and -CH=CF₂ groups were designed and prepared via various synthetic routes, including HX or BrF elimination, Wittig-type olefination or fluorination using SF₄.

Full text of DOI:10.1016/j.jfluchem.2015.08.001

Accepted Manuscript
Title: Alternative Synthetic Routes to Hydrofluoro Olefins
Author: Yu.L. Yagupolskii N.V. Pavlenko S.V. Shelyazhenko
A.A. Filatov M.M. Kremlev A.I. Mushta I.I. Gerus Sheng
Peng V.A. Petrov Mario Nappa
PII:
S0022-1139(15)00231-6
DOI:
Reference:
http://dx.doi.org/doi:10.1016/j.jfluchem.2015.08.001
FLUOR 8632
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FLUOR
Received date:
Revised date:
Accepted date:
29-4-2015
29-7-2015
1-8-2015
Please cite this article as: Yu.L. Yagupolskii, N.V. Pavlenko, S.V. Shelyazhenko, A.A.
Filatov, M.M. Kremlev, A.I. Mushta, I.I. Gerus, S. Peng, V.A. Petrov, M. Nappa,
Alternative Synthetic Routes to Hydrofluoro Olefins, Journal of Fluorine Chemistry
(2015), http://dx.doi.org/10.1016/j.jfluchem.2015.08.001
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Alternative Synthetic Routes to Hydrofluoro Olefins
Yu. L.Yagupolskii a*, N.V. Pavlenko a, S.V. Shelyazhenko a, A.A. Filatov a, M.M. Kremlev a,
A.I. Mushta a, I.I. Gerus b, Sheng Peng c, V. A. Petrov c, Mario Nappa c*
a Institute of Organic Chemistry, National Academy of Sciences of Ukraine, Murmanska St. 5,
Kiev 02660, Ukraine
b Institute of Bioorganic Chemistry and Petrochemistry National Academy of Sciences of
Ukraine, Murmanskaya St. 1, Kiev 02660, Ukraine.
c The Chemours Company, Experimental Station, Bldg. 262, Wilmington, DE 19880.
*Corresponding authors
E-mail addresses: Yagupolskii@ioch.kiev.ua;
Mario.J.Nappa@chemours.com
Keywords: olefins, fluorination, elimination, Wittig-type olefination, tosylates, β-diketones
Abstract
A series of hydrofluoroolefins with -CF=CH2, -CH=CHF and -CH=CF2 groups was designed
and prepared via various synthetic routes, including HX or BrF elimination, Wittig-type
olefination or fluorination using SF4.
 environment friendly hydrofluoroolefins with terminal -CF=CH2, -CH=CHF and -CH=CF2
groups have been designed and prepared
 HX or FBr elimination, Wittig-type olefination, fluorination with SF4
 novel fluoroalkenes with low boiling points
1. Introduction
1
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While it has not been proven, most climate scientists agree that global climate change is
the result of the release of large amounts of CO2 from the burning of fossil fuels with a
contribution from long lived man-made chemicals that accumulate in the upper atmosphere and
absorb infrared radiation from the Earth [1]. Traditional fluorochemicals have high global
warming potentials, and many are used in emissive applications. Hence, low global warming
alternatives are constantly being sought after that have the appropriate characteristics and
physical properties for end use applications such as refrigeration, air conditioning, foam
expansion, clean agent fire suppression, specialty fluids, propellants, and semiconductor chip
manufacture [2]. The industry has been targeting hydrofluoroolefins for these applications since
the unsaturation reduces atmospheric life by providing a point of attack for hydroxyl and nitroxyl
radicals [3]. Our efforts have been focused on identifying and developing synthetic schemes to
hydrofluoroolefin candidates that are economically viable, have low toxicity, low cost of
manufacture, appropriate level of flammability, and efficacy in use.
Traditional Swarts chemistry while useful is of limited utility in the synthesis of
functionalized olefins. The products of this type of reaction are usually saturated and have some
chlorine remaining in the molecule [4], which can lead to a high ozone depletion potential.
Herein we examine Br-F elimination reactions, fluorinations with SF4, Wittig-type olefinations,
and HX elimination as more selective methods to make hydrofluoroolefins.
2. Results and discussion
2.1. Polyfluoroalkenes with -CF=CH2 fragment
2.1.1. Elimination reactions
The elimination reaction is a common method to access olefins with -CF=CH2 fragment
by few ways.
2.1.1.1. BrF elimination
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Some olefins were obtained via this method from fluorinated alcohols RfCF2CH2OH,
which were activated with tosyl chloride to give tosylates [5], which were transformed into
appropriate bromides with KBr [6]; the last were treated with Zn to eliminate BrF [7] and afford
desired olefins. Three alkenes – 2,3,3-trifluoroprop-1-ene (4a), 2,3,4,4,4-pentafluorobut-1-ene
(4b) and 2,3,3,4,4,5,5,5-octafluoropent-1-ene (4c) were prepared in such a way according to
Scheme 1:
Scheme 1. Syntheses of alkenes 4a-c from appropriate alcohols, reagents and conditions: i) an
equimolar mixture of alcohol 1a-c, TsCl and base, rt, yields 75-90%; ii) excess KBr, diethylene
glycol, 200 °C, yields 70-80%; iii) 3-fold excess of activated Zn metal, iso-propanol or dioxane,
reflux, yields: 4a 81%, 4b 63%, 4c 82%.
2.1.1.2. HX elimination
This synthetic approach to terminal fluorinated alkenes is widely used. Tosylation of an
appropriate alcohol followed by a base-promoted elimination of p-toluenesulfonic acid (PTSA)
affords polyfluoroalkenes with good yields [8]. The preparation of 1-fluoro-1-
(pentafluoroethoxy)ethene (7) was performed with this strategy according to Scheme 2:
3
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Scheme 2. Synthesis of alkene 7 from alcohol 5 by subsequent tosylation and elimination of
PTSA. Reagents and conditions: i) equiv. of TsCl, Py, as a base and a solvent, 0 °C → rt, 12 h,
yield 82%; ii) equiv. of LiHMDS, DME, rt→100 °C, 4 h, yield 57%.
Alcohol 5 was converted into its tosylate 6 using a typical procedure [5] followed by
treatment with an equimolar amount of LiHMDS. We were not successful using either t-BuOK,
DBU or KF [8] for abstraction of PTSA. .
Starting compound 5 was prepared using two-step process depicted by Scheme 3:
Scheme 3. Synthesis of alcohol 5. Reagents and conditions: i) an equimolar mixture of 8 and 9,
DME, rt, overnight, then 50→80 °C, 4 h, yield 45%; ii) LiAlH4, ether, reflux, 1 h, yield 68%.
Ethyl bromofluoroacetate (8) was reacted with cesium alkoxide (9) [9] to produce the
ester 10 in a moderate yield, followed by the reduction using LiAlH4 to to afford alcohol 5.
It should be noted, that an alternative synthetic route to ester 10 using the reaction of 8
with N-fluoro(phenylsulfonyl)imide (NFSI) resulted in low yield formation of acetate 10 (NMR
data) in a mixture with starting ester 11 (Scheme 4).
4
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Scheme 4. An alternative synthesis of ester 10 via electrophilic fluorination with NFSI. Reagents
and conditions: i) an equimolar mixture of reagents, DME, rt overnight, then 50→80 °C, 4 h,
yield 63%; ii) an equimolar mixture of BuLi, NFSI and 11, THF/hexane, -90 °C, 4 h, -90 °C→rt,
overnight, yield ~30%, as a mixture 11/10 ≈ 2/1.
2.1.2. Fluorination of β-diketones with SF4
Inspired by the work of Lev Yagupolskii and coworkers [10] on the fluorination of β-
diketones with SF4, 2,3,3,4,4-pentafluorobut-1-ene (13) was prepared from β-diketone 12
(Scheme 5).
Scheme 5. Synthesis of alkene 13 via fluorination of β-diketone 12 with SF4. Reagents and
conditions: autoclave, 2-fold excess of SF4, without solvent, 80 °C, 20 h, yield 58%, impurity
CF3CH3 ~7 molar%.
β-Diketone 12 was obtained from ethyl 2,2,3,3-tetrafluoropropanoate and acetone
through a classic Claisen condensation [11]. Fluorination occurred in accordance with a scheme,
proposed by Yagupolskii to give the expected olefin 13 in a satisfactory yield. The isolated olefin
13 was contaminated by-product 1,1,1-trifluoroethane (~7 molar %, based on NMR and GLC).
In order to increase the number of alkenes, accessible by this approach, an attempt was
made to synthesize the aforementioned isomeric olefin 4b. (3Z)-5,6,6,6-Tetrafluoro-4-
5
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hydroxyhex-3-en-2-one (16) has been obtained previously in a moderate yield (≤40%) by
electrophilic acylation of trifluoroethene with acetyl fluoride using SbF5 catalyst [12]. Since
classical Claisen methodology cannot be used due to dehydrofluorination under basic conditions,
an alternative route was employed to prepare diketone 16 (Sheme 6).
Scheme 6. Synthesis of β-diketone 16 from chloroanhydride 14 and 2-methoxyprop-1-ene.
Reagents and conditions: i) an equimolar mixture of 14, methoxypropene and Py, CH2Cl2,
0 °C→rt, overnight, yield 58%; ii) equiv. H2O, traces HCl, 50 °C, 48 h, yield 89%.
Synthesis was carried out by the reaction of 2,3,3,3-tetrafluoropropanoyl chloride (14)
[13] and 2-methoxyprop-1-ene resulting in vinyl ether 15, followed by a hydrolysis step to give
the desired β-diketone 16 in a high yield. It should be noted that this ketone exists in solution
only in the enol form, which is typical for fluorinated β-diketones.
It turned out that the method of β-diketones fluorination with SF4 is inapplicable for the
synthesis of butene 4b. Fluorination of enole 16 occurred without cleavage of the chain, giving
a complex mixture of fluorinated products (Scheme 7).
Scheme 7. Fluorination of β-diketone 16 with SF4. Reagents and conditions: i) 2-fold excess of
SF4, without solvent, 80 °C, 20 h.
6
Page 6 of 28

It is reasonable to assume that fluorinated group in enole 16 is an insufficient electron
acceptor to break the C-C bond by analogy with reactions of nonfluorinated aliphatic β-diketones
with SF4 [10]. According to the NMR data main products in the crude reaction mixture were the
polyfluorohexane 17 and compound 18, (mostly Z-isomer), while the target olefin 4b was
present in trace amounts.
2.2. Polyfluoroalkenes with -CH=CHF fragment
2.2.1. Wittig-type olefination
The syntheses of terminal monofluoroalkenes through Wittig-type reactions have been
well studied by Burton and coworkers [14], however reaction of fluoromethylene ylide with
aliphatic fluorinated aldehydes was not reported We demponstrated that this route can be used to
prepare 1,4,4,4-tetrafluorobut-1-ene (19) and 1,3,4,4,4-pentafluorobut-1-ene (20) starting from
the corresponding aldehydes – 2,3,3,3-tetrafluoro- (21) or 3,3,3-trifluoro- (22).propanals
To the best of our knowledge, necessary aldehyde 21 is unavailable with published
preparative methods and has been only described as a byproduct, obtained under thermal
decomposition of the adduct of pentafluoropropene and methanol in a low yield and without any
details and NMR characterization [15]. Several methods have been developed for the preparation
of trifluoropropanal 22 [16]. According to the literature data, the best methods use enol esters
CF3CH=CHOR, as starting materials, usually prepared form trifluoropropyne [16a]. 2-Bromo-
3,3,3-trifluoropropene [16c] or 1-chloro-3,3,3- trifluoropropene [16d] have been used as starting
materials for the synthesis of these enol esters.
We developed a convenient method for the preparation of aldehydes 21 and 22 starting
from 1,2,3,3,3-pentafluoroprop-1-ene (HFO-1225ye) and 2,3,3,3-tetrafluoroprop-1-ene (HFO-
1234yf), respectively (Schemes 8 and 9).
7
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Scheme 8. Synthesis of tetrafluoropropanal 21 from HFC 1225ye. Reagents and conditions: i)
bubbling HFC 1225ye through a solution of equiv KOH in ethanol, 5–10 °C, 2-3 h, rt, overnight,
yields a mixture of 23:24:25 in a molar ratio ~13:2:1, based on 19F NMR; ii) heptanoic
acid/H2SO4, 110–120 °C, 6 h, yield 72%.
Scheme 9. Synthesis of trifluoropropanal 22 from HFO-1234yf. Reagents and conditions: i)
autoclave, 2-fold excess of KOH, ethanol, interphase transfer Bu4NCl, 125–130 °C, 5 h, yields a
mixture of 26 and 27 in a molar ratio ~11:2, based on 19F NMR; ii) heptanoic acid, admixed with
traces H2SO4, 110–120 °C, 6 h, yield 64%.
The corresponding olefin (HFO-1225ye or 1234yf, Scheme 8 and 9, respectively) were
reacted with ethanolic solution of potassium hydroxyde in the presence traces of water to give
reaction mixtures, consisting of the addition/elimination products described similarly to
transformations in [16c]. It should be noted, that NMR analyses of these mixtures showed a
8
Page 8 of 28

crucial distinction between the reactivity of the starting olefins; namely tetrafluoropropene
reacted with the elimination of the fluorine atom in the α-position to the CF3 group, while in the
case of pentafluoropropene this atom persisted. More reactive pentafluoropropene converted at
5–10 ˚C in an open system under bubbling through a solution of KOH in ethanol, whereas
tetrafluoropropene was reacted with ethoxy anion only at elevated temperature (130 ˚C). The
reaction mixture, obtained in accordance with Scheme 9, contained predominantly ether 26
(~60%), and the last could be easily transformed into the appropriate acetal 27 with ethanol in
standard conditions (PTSA catalysis) [16c] quantitatively.
It should be noted that conversion of enol esters (23, 26) or acetals (25, 27) into 21 and 22
was problematic, under condition described in in patent [16d]. However, when reaction
mixtures, obtained in accordance with Schemes 8 and 9, were treated with heptanoic acid in the
presence of sulfuric acid catalyst desired aldehydes were obtained in good yields (72% for 21
and 65% for 22). This procedure was more effective in comparison with standard hydrolysis with
diluted mineral acids described in the literature [16b, 17].
Fluorobutene 19 (Scheme 10) and 1,3,4,4,4-pentafluorobut-1-ene (20) were obtained from
propanals 21 and 22 appropriately using two Wittig reagents, presented on Scheme 10 (Method
A) and Scheme 11 (Method B), respectively.
Scheme 10. Synthesis of butene 19 via Wittig procedure (Method A). Reagents and conditions:
i) equiv LHMDS, THF, -78 °C, 0.5 h; ii) equiv 21, -78 °C, 1 h, 5 °C, overnight, yields a mixture
of 19 (~60%) and THF, based on GLC.
9
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In Method A (Scheme 10) tetrafluoropropanal 21 was reacted with ylide 29, generated in
situ from phosphonium tetrafluoroborate 28 according to Burton`s method [18]. We modified the
procedure for the generation of ylide 29 from salt 28, using LHMDS as a base to avoid the
destruction of starting aldehyde, sensitive to the action of traditional bases (t-BuOK, BuLi etc).
The reaction was carried out at ≤-78 °C in various solvents; products were condensed in a low
19
temperature trap and then analyzed with F NMR spectroscopy and GLC analysis. It should be
noted that only THF was suitable as a solvent for this transformation, and the target olefin 19
19
was formed in ~60% yield as a mixture of E/Z isomers in a ratio ~1/1, based on F NMR data.
Unfortunately, under distillation at atmospheric pressure butene 19 was obtained as a mixture
with THF in various proportions, and we failed to obtain a pure compound by this method.
We succeeded to prepare pure tetrafluorobutene 19 and trifluorobutene 20 using the
stable phosphoranium salt 30 [19] (Method B, Scheme 11):
Scheme 11. Syntheses of polyfluorobutenes 19 and 20 via Wittig procedure (Metod B). Reagents
and conditions: i) an equimolar mixture of 30 and 21 or 22, benzonitrile, ≤10 °C, 0.5 h; ii)
aqueous 10% NaOH, 10 °C→rt, overnight, yelds: 19 (61%), 20 (63%).
Wittig reaction of tetrafluoropropanal 21 and trifluoropropanal 22 with the stabilized
ylide 30 afforded the corresponding phosphonium salts 31 and 32 in high yields. Subsequent
cleavage of the P-C bond in these salts by alkaline hydrolysis led to the formation of the desired
olefins 19 and 20 stereospecifically as Z-isomers in satisfactory yields. The Z stereoselectivity
can be explained by the through-space, charge-transfer complex, in analogy with reaction
10
Page 10 of 28

mechanism proposed by Burton [19b] for aromatic aldehydes with electron-withdrawing
substituents and the stabilized ylide 30.
2.2.2. HX elimination
Polyfluoroalkylation of carbon-carbon double bonds is one of the most important and
general methods for the synthesis of a variety of organofluorine compounds containing
polyfluoroalkyl groups. For the conversion of vinyl fluoride into its polyfluorinated equivalent
with –CH=CHF fragment, the radical addition of perfluoroalkyl iodides followed by elimination
HI was elaborated [20]. We used this approach to obtain 1,3,3,4,4,5,5,5-octafluoropentene-1 (33)
(Scheme 12).
Scheme 12. Synthesis of octafluoropropene 33 via addition perfluoropropyl iodide to vinyl
fluoride followed by elimination HI. Reagents and conditions: i) excess of C3F7I, catalytic
amounts of benzoyl peroxide, autoclave, 110–120 °C, 4 h, yield 80%; ii) aqueous KOH,
interphase transfer agent Bu4NCl, 90–100 °C, 1 h, yield 68%, E/Z mixture ~3/1.
Perfluoropropyl iodide was reacted with vinyl fluoride in autoclave at 120 °C under
benzoyl peroxide promotion to give undeclared in the literature iodide 34 in 80% yield.
Elimination of HI with an aqueous KOH in the presence of interphase transfer agent led to the
desired pentene 33 in a good yield as a mixture of E/Z isomers in a ratio ~3/1.
2.3. Polyfluoroalkenes with –CH=CF2 fragment
2.3.1. Wittig-type olefination
Wittig reaction is a useful route to difluoromethylene olefins, in particular to olefins with
–CH=CF2 fragment [21]. We used this fruitful approach to obtain 1,1,3,4,4,4-hexafluorobut-1-
11
Page 11 of 28

ene (35) via interaction of tetrafluoropropanal 21 with ylide 36, which was generated in situ
(Scheme 13).
Scheme 13. Synthesis of hexafluorobutene 35 from tetrafluoropropanal 21 via Wittig protocol.
Yields and quality of butene 35, which was obtained in this manner, are largely
dependent on the method used for generation of ylide 36. The necessary Wittig reagent was
synthesized in situ via Burton`s method [19] from the readily available phosphonium salt 37 by
bromine abstraction with zinc metal (Method C) or a second equivalent of Ph3P (Method D)
(Scheme 14).
Scheme 14. Synthesis of butene 35 via the reaction of tetrafluoropropanal 21 with Wittig reagent
36, which was generated in situ from phosphonium salt 37 by two ways. Reagents and
conditions: i) method C: two-fold excess of Wittig reagent and Zn, DMAA, 110 C, 1 h, yield
37%; ii) method D: two-fold excess of Ph3P, diglyme, 110 C, 2 h; iii) equimol Br2, CHCl3,
irradiation with “sunlight” lamp, rt, 1 h, a mixture of two diastereoisomers in a ratio ~5/2, yield
69%; iv) two-fold excess of Zn dust, iso-PrOH, 35 C, 2 h, yield 50% in terms of 21.
12
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It turned out that under Wittig reagent generation with Zn metal, olefin 35 was formed in
a pure form in 37 % yield, while an action of a second equivalent Ph3P on phosphonium salt 37
gave butene 35 as an inseparable mixture with bromodifluoromethane. Bromination of this
mixture to a new mixture of dibromobutane 38 with CHF2Br followed by bromine abstraction
with zinc metal gave pure olefin 35 in 50% yield in terms of starting propanal 21.
3. Conclusions
A series of hydrofluoroolefins with -CF=CH2, -CH=CHF and -CH=CF2 fragments have
been prepared in moderate to good yields. These hydrofluoroolefins have boiling points in the
range 0-50 ºC. Compared to traditional saturated organofluorine chemicals, these
hydrofluoroolefins have low global warming potential, and may be useful in a wide range of
industrial applications.
4. Experimental
4.1. General information
NMR spectra were recorded on Varian VXR-300 or Bruker Avance DRX-500
1
13
spectrometers for H (TMS); on Bruker Avance DRX-500 spectrometer for C {H} (TMS); on
Varian Gemini-200 or Varian Unian Plus-400 spectrometers for 19F (CFCl3). Reactions with
moisture-sensitive materials were carried out under argon atmosphere. Standard vacuum
techniques were used for operations with gases and low boiling and highly volatile liquids. All
solvents and reagents, unless otherwise indicated, were purchased from commercial sources and
used directly as supplied. Alcohol 1a is commercially available product. Compound 1b was
prepared according to the literature procedure [5b]. Pentanol 1c was obtained via hydrogenetaion
of ethyl perfluorobutyrate with LiAlH4 by the standart method. Olefins HFC-1225ye and HFO-
1234yf were received from the Chemours Company.
4.2. Synthesis and characterization of products
13
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4.2.1. Synthesis of alkenes 4a-c.
4.2.1.1. Starting materials.
The procedures, utilized for the syntheses of tosylates 2a-c were described previously [5].
2,2,3,3-Tetrafluoropropyl 4-methylbenzenesulfonate (2a) was synthesized according to the
method [5a]; physical constants and NMR spectra conformed with published data [5a].
4.2.1.1.1. 2,2,3,4,4,4-Hexafluorobutyl 4-methylbenzenesulfonate (2b).
Tosilate 2b was synthesized according to the method [5b]. The product (yield 88%, NMR
purity 98%) was obtained as a colorless viscous liquid. 19F NMR (188 MHz, CDCl3) δ - 75.8 (m,
3F, CF3), -117.6 (AB, 1F, d, 2JFF = 279 Hz, CF2), -123.6 (AB, 1F, d, 2JFF = 279 Hz, CF2), -214.8
(m, 1F, 2JFH ≈ 40 Hz, CHF).
4.2.1.1.2. 2,2,3,3,4,4,5,5,5-Nonafluoropentyl 4-methylbenzenesulfonate (2c).
Tosilate 2c was synthesized according to the method [5c]. The product (75%) was
obtained as colorless crystals: mp 57 °C. 19F NMR (188 MHz, CDCl3): δ - 81.8 (s, 3F, CF3),
-120.4 (s, 2F, CF2), -124.6 (s, 2F, CF2), -127.0 (s, 2F, CF2).
4.2.1.1.3. 3-Bromo-1,1,2,2-tetrafluoropropane (3a) [5a] and 4-Bromo-1,1,1,2,3,3-
hexafluorobutane (3b) [6b] were prepared as described; physical constants and NMR spectra
conformed to the published data [5a, 6b].
4.2.1.1.4. 5-Bromo-1,1,1,2,2,3,3,4,4-nonafluoropentane (3c).
A mixture of 2c (7.77 g, 19 mmol), KBr (3.37 g, 0.028 mmol) and diethylene glycol (15
mL) was heated at 200–220 °C for 3 h with the simultaneous distillation of all volatiles. This
distillate was divided into 2 layers, and the bottom layer was distilled with a short column to give
3c as an azeotropic mixture with dibromoethane (5.96 g of azeotrop, bp 90–91 °C, content of 3c
~80% based on GLC). Yield of 3c 4.77 g (80%). This azeotropic mixture was used in the next
1
3
19
step without additional procedures. H NMR (300 MHz, CDCl3): δ 3.74 (tm, JHF = 16 Hz). F
NMR (188 MHz, CDCl3): δ -81.5 (s, 3F, CF3); -113.8 (m, 2F, CF2); -123.6 (s, 2F, CF2); -126.4
(s, 2F, CF2).
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4.2.1.2. General procedure for the synthesis of alkenes 4a-c from appropriated bromoalkanes via
BrF elimination.
An appropriate bromide 3a-c was slowly added under stirring to a suspension of threefold
excess Zn dust in a suitable solvent (25 mL per 50 mmol 3a-c, iso-propanol for 3a and dioxane
for 3b,c) at moderate reflux. Heating was continued for 1 h. All volatiles were collected through
a condenser in a Dry Ice cooled trap and then distilled. Repeated distillation gave pure olefins
4a-c. The purity of these compounds was confirmed with the NMR data and GLC analysis.
4.2.1.2.1. 2,3,3-Trifluoroprop-1-ene (4a).
1
3
Gas (81%): bp 5–6 °C. H NMR (300 MHz, CDCl3): δ 4.97 (dd, 1H, JHFtrans = 34.3 Hz,
2
3
2JHH = 4.2 Hz, CH2=); 5.07 (m, 1H, CH2=); 6.03 (td, 1H, JHF = 53.7 Hz, JHF.= 5.3 Hz, CHF2);
19F NMR (188 MHz, CDCl3): δ -122.4 (m, 1F, CF=); -124.7 (dm, 2F, 2JHF = 53.7 Hz, CF2H); 13C
1
2
1
(125 MHz, CDCl3): δ 156.5 (dt, JCF = 260.3 Hz, JCF = 26.2 Hz, CF=), 108.6 (td, JCF = 238.4
Hz, 2JCF = 39.8 Hz, CHF2), 95.5 (dt, 2JCF = 13 Hz, 3JCF = 5 Hz, CH2=).
4.2.1.2.2. 2,3,4,4,4-Pentafluorobut-1-ene (4b).
Highly volatile liquid (63%): bp 24–25 °C. 1H NMR (300 MHz, CDCl3): δ 5.16 (ddd, 1H,
3JHFcis = 17.0 Hz, 2JHH = 4.3 Hz, 4JHF = 1.6 Hz, CH2=), 5.05 (ddq, 1H, 2JHF = 43.6 Hz, 3JHF = 11.5
3
3
2
Hz, JHF(CF3) = 5.6 Hz, CHF), 4.98 (dd, 1H, JHFtrans = 45.8 Hz, JHH = 4.3 Hz, CH2=); 19F NMR
13
(188 MHz, CDCl3): δ -79.0 (m, 3F, CF3), -114.2 (m, 1F, =CF), -202.7 (m, 1F, CFH); C NMR
(125 MHz, CDCl3): δ 154.6 (dd, 1JCF = 260.8 Hz, 2JCF = 21.7 Hz, CF=), 120.9 (dq, 1JCF = 281.4
2
2
1
Hz, JCF = 27.8 Hz, CF3), 98.1 (d, JCF = 14.2 Hz, CH2=), 84.4 (d of quintets, JCF = 189.7 Hz,
2JCF = 36.3 Hz, CHF).
4.2.1.2.3. 2,3,3,4,4,5,5,5-Octafluoropent-1-ene (4c).
Highly volatile liquid (82%): bp 31–32 °C. 1H NMR (400 MHz, CDCl3): δ 5.30 (dd, 1H,
3JHFtrans = 47.2 Hz, 2JHH = 5.7 Hz, CH=), 5.40 (ddt, 1H, 3JHFcis = 17.0 Hz, 2JHH = 5.7 Hz, 4JHFtrans
= 1.7 Hz, CH=); 1H NMR (400 MHz, DMSO-D6): δ 5.81 (dd, 1H, 3JHFtrans = 47.3 Hz, 2JHH = 5.8
3
2
4
19
Hz, CH=), 5.91 (ddt, 1H, JHFcis = 17.2 Hz, JHH = 5.8 Hz, JHFtrans = 1.7 Hz, CH=); F NMR
15
Page 15 of 28

(376 MHz, CDCl3): δ -82.0 (s, 3F, CF3), -119.7 (dm, 1F, 3JFHtrans = 47.2 Hz, CF=), -120.1 (m, 2F,
CF2), -128.5 (s, 2F, CF2); 13C NMR (125 MHz, CDCl3): δ 152.1 (dt, 1JCF = 266.6 Hz, 2JCF = 30.2
1
2
1
Hz, FC=), 117.5 (qt, JCF = 286.7 Hz, JCF = 33.9 Hz, CF3), 109.6 (tm, JCF = 255.2 Hz, CF2),
108.3 (tm, 1JCF = 266.6 Hz, CF2), 99.2 (s, CH2=).
4.2.2. Synthesis of alkene 7.
4.2.2.1. Ethyl 2-fluoro-2-(pentafluoroethoxy)acetate (10).
CHBrFC(O)OEt (5.4 g, 29 mmol) was added through a syringe to a clear solution of
C2F5OCs [9] in 30 mL diglyme, obtained from CsF (4.50 g, 29.6 mmol) and CF3C(O)F (3.8 g,
32.7 mmol). The reaction mixture was stirred overnight at rt, then gradually heated up to 80 ºC
for 8 h, and the resulting precipitate was filtered off. The filtrate obtained was distilled at
atmospheric pressure, and all products that boiled up to 140 ºC were collected. This mixture was
twice fractionated with a short column to give ester 10 (3.1 g, 44.5%) as a colorless liquid: bp
97–102 ºC. 1H NMR (300 MHz, CDCl3): δ 1.34 (t, 3H, 3JHH = 8 Hz, CH3), 4.34 (q, 2H, 3JHH = 8
Hz, CH2), 6.05 (d, 1H, 2JHF = 54 Hz, CHF); 19F NMR (376 MHz, CDCl3): δ -86.9 (s, 3F, CF3),
-89.8 (AB, d, 1F, 2JFF = 146 Hz, CF2), -91.9 (AB, d, 1F, 2JFF = 146 Hz, CF2), -136.1 (d, 1F, 2JFH
= 54 Hz, CHF).
4.2.2.2. Electrophilyc fluorination of ethyl 2-(pentafluoroethoxy)acetate (11) with NFSI.
2.4 M solution of BuLi in hexane (18 mL, 44 mmol) was added to a solution of HMDS
(7.08 g, 44 mmol) in THF (30 mL) at -78 °C and the mixture was stirred at this temperature for
0.5 h. To the resulting solution of LHMDS was added the ester 11 [9] (8.70 g, 39 mmol), the
mixture was stirred for 1 h, cooled to -90 °C and the solution of NSIF (12.60 g, 40 mmol) in
THF (50 mL) was slowly added (~2 h). The reaction mixture was stirred at -90 °C for an
additional hour, allowed to warm to room temperature, stirred overnight and then partitioned
between ether and aqueous solution of saturated NH4Cl. The solids were filtered off and the
organic layer was separated, dried and concentrated. The residue was distilled at atmospheric
pressure and gave after repeated distillation an azeotropic mixture of acetates 10 and 11 in a ratio
16
Page 16 of 28

~2:1 (10.28 g, bp 121–122 °C), which could not be separated into its constituents by
redistillation.
4.2.2.3. 2-Fluoro-2-(pentafluoroethoxy)ethanol (5).
Ester 10 (3.84 g, 16 mmol) was slowly added to the 1M solution LiAlH4 in ether (15 mL,
15 mmol) under ice water cooling at such a rate to keep ether gently boiling. Then the reaction
mixture was boiled an additional 1 h. After cooling to 0 ºC 15 mL 1N HCl were cautiously
added, an organic layer was separated, washed with the solution of NaHCO3 and then dried with
MgSO4. Ether was distilled off at atmospheric pressure, and the residue was fractionated to give
1
alcohol 5 as a colorless liquid (2.15 g, 68%): bp 95–97 ºC. H NMR (300 MHz, CDCl3): δ 2.41
3
(bs, 1H, OH), 3.88-3.64 (AB, m, 2H, 2JHH = 9.3Hz, JHH = 4.7 Hz, CH2), 5.94 (dt, 1H, 2JHF = 57
3
19
Hz, JHH = 4.7 Hz, CHF); F NMR (188 MHz, CDCl3): δ -87.1 (s, 3F, CF3), -89.8 (AB, d, 1F,
2JFF = 154 Hz, CF2), -90.7 (AB, d, 1F, 2JFF = 154 Hz, CF2), -137.2 (dm, 1F, 2JFH = 57 Hz, CHF).
4.2.2.4. 2-Fluoro-2-(pentafluoroethoxy)ethyl 4-methylbenzenesulfonate (6).
TsCl (2.4 g, 12.6 mmol) suspended in Py (5 mL) at 0 ºC and 5 (2.15 g, 11.9 mmol) were
added dropwise under stirring. The reaction mixture was stirred at rt overnight, poured into ice,
acidified with HCl and extracted with ether. The organic layer was washed with an aqueous
solution of NaHCO3 and dried with MgSO4. All volatiles were distilled off in vacuo 10 mm Hg
1
to give 6 (3.44 g, 82 %) as a colorless semisolid. H NMR (300 MHz, CDCl3): δ 2.46 (s, 3H,
2
3
2
CH3), 4.08-4.35 (AB, 2H, JHH = 11.8 Hz, JHH = 4.8 Hz, CH2), 6.05 (dt, 1H, JHF = 55.6 Hz,
3JHH = 4.8 Hz, CHF), 7.36 (d, 2H, arom.H), 7.79 (d, 2H, arom.H); 19F NMR (188 MHz, CDCl3):
δ -87.0 (s, 3F, CF3), -89.8 (AB, d, 1F, 2JFF = 154 Hz, CF2), -91.0 (AB, d, 1F, 2JFF = 154 Hz, CF2),
-134.1 (dm, 1F, 2JFH = 56 Hz, CHF).
4.2.2.5. 1-Fluoro-1-(pentafluoroethoxy)ethylene (7).
A solution of freshly prepared LHMDS (5.18 g, 31.0 mmol) in diglyme (15 mL) was
added to 6 (10.75 g, 30.5 mmol) in diglyme (15 mL) under stirring at rt for 30 min. The reaction
mixture was stirred and gradually heated from 30 ºC to 100 ºC for 4 h. During this period, a
17
Page 17 of 28

slow current of Ar was allowed to stream through the system, and all volatiles were condensed in
a trap (-78 °C). This condensate was twice distilled to give pure olefin 7 (2.92 g, 53 %) as a gas:
1
3
2
bp 6–7 ºC. H NMR (300 MHz, CDCl3): δ 4.31 (dd, 1H, JHFtrans = 36.0 Hz, JHH = 4.6 Hz,
2
3
19
=CH2), 4.43 (dd, 1H, JHH = 4.6 Hz, JHFcis = 2.8 Hz, =CH2); F NMR (188 MHz, CDCl3): δ -
80.6 (dm, 1F, 3JFHtrans = 36.0 Hz, 4JFF = 8.1 Hz, =CF), -86.9 (s, 3F, CF3), -91.1 (d, 2F, 4JFF = 8.1
13
2
1
Hz, CF2); C NMR (125 MHz, CDCl3): δ 78.1 (d, JCF = 26 Hz, =CH2), 113.5 (tq, JCF = 279
Hz, 2JCF = 43 Hz, CF2), 116.2 (qt, 1JCF = 285 Hz, 2JCF = 43 Hz, CF3), 153.4 (d, 1JCF = 285.5 Hz,
=CF).
4.2.3. 2,3,3,4,4-Pentafluorobut-1-ene (13).
Synthesis was performed in 50-ml autoclave under autogenous pressure with agitation.
The autoclave was charged with diketone 12 [11] (7.44 g, 40 mmol), cooled to -196 °C,
evacuated and SF4 (8.6 g, 80 mmol) was then condensed. The autoclave was closed and allowed
to agitate at 80 °C for 20 h, then cooled to rt and volatile materials were carefully transferred in a
trap (-78 °C) through an ice water-cooled vessel with 20 % solution KOH to neutralize S(O)F2,
HF and an excess of SF4. At the end of the volatilization the autoclave and absorbing vessel were
kept at 40 °C to complete the evaporation of all volatiles. Olefin 13 was purified by trap-to-trap
distillation of condensate and obtained as a high volatile liquid (3.4 g, 58 %) with impurity of
1
CF3CH3 (7 molar % due to NMR): bp 27–28 °C. H NMR (500 MHz, CDCl3): δ 5.24 (dd, 1H,
3JHFtrans = 30.5 Hz, 2JHH = 4.5 Hz, =CH2), 5.3 (m, 1H, =CH2), 5.92 (tt, 1H, 2JHF = 53.0 Hz, 3JHF
=
3.5 Hz, CHF2); 19F NMR (376 MHz, CDCl3): δ -120.5 (dm, 1F, 3JFHtrans = 30.5 Hz, =CF), -122.6
(m, 2F, CF2), -137.1 (d, 2F, 2JFH = 53 Hz, CF2H); 13C NMR (125 MHz, CDCl3): δ 98.0 (dm, 2JCF
1
2
1
= 12.2 Hz, CH2=), 153.3 (dt, JCF = 260.0 Hz, JCF = 31.3 Hz, CF=), 109.1 (tt, JCF = 250.0 Hz,
2JCF = 37.5 Hz, CF2H), 109.9 (tq, 1JCF = 250.6 Hz, 2JCF = 30.0 Hz, CF2).
4.2.4. An approach to the synthesis of alkene 4b via fluorination with SF4 .
4.2.4.1. 5,6,6,6-Tetrafluoro-4-hydroxyhex-3-en-2-one (16).
18
Page 18 of 28

A solution of 14 [13] (17.25 g, 105 mmol) in CH2Cl2 (20 mL) was added to a solution of
2-methoxyprop-1-ene (7.55 g, 105 mmol) and Py (8.28 g, 105 mmol) in CH2Cl2 (50 mL) at 0 °C,
and the reaction was stirred at rt overnight. Resulting mixture was diluted with pentane and
washed with ice-cooled citric acid solution until pH~6 and then with water until neutral. Organic
layer was dried with MgSO4, solvents were removed at atmospheric pressure, and the residue
was distilled to give 1,1,1,2-tetrafluoro-5-methoxyhex-4-en-3-on (15) (12.2 g, 58%) as a
19
3
colorless liquid: bp 88–90 °C (40 mm Hg). F NMR (188 MHz, CDCl3): δ -77.2 (d, 3F, JFH
=
11 Hz, CF3), -203.2 (dm, 1F, 2JFH = 45.1 Hz, CFH). Enon 15 (8.64 g, 43 mmol) was hydrolyzed
with an equivalent H2O (0.8 mL, 43 mmol), slightly acidified with traces HCl at 50 °C for 48 h.
Reaction mixture was diluted with pentane, dried with MgSO4 and distilled to give 16 (7.1 g,
89%) as a colorless volatile liquid: bp 136–137 °C (lit. [12] 136–138 °C).
4.2.4.2. Fluorination of enone 16 with SF4.
Reaction was performed as it was described for the synthesis of alkene 13. Compound 16
(7.56 g, 40 mmol) was reacted with SF4 (9.0 g, 80 mmol) to give a complex mixture. Two
gaseous products, CF3CH3 and alkene 4b were collected in a trap (-78 ºC) (0.35 g). The residue
after evaporation of all volatiles products was washed with ice-cooled water, then aqueous
NaHCO3, dried with MgSO4 and fractionated to yield a main fraction (3.87 g, bp 62–68 °C) as a
mixture of 17 and 18 in a molar ratio ~1:3. 1,1,1,2,3,3,5,5,-Octafluorohexane (17). 1H NMR (500
MHz, CDCl3): δ 1.78 (t, 3H, 3JHF = 15.2 Hz, CH3), 2.71 (m, 2H, CH2), 4.90 (d of multiplets, 1H,
3
19
2JHF = 34.8 Hz, JHF ≈ 5 Hz, CHF); F NMR (376 MHz, CDCl3) δ -74.7 (m, 3F, CF3), -85.7
(AB, dm, 1F, 2JFF = 251.9 Hz, CF2), -87.5 (AB, dm, 1F, 2JFF = 251.9 Hz, CF2), -107.2 (AB, dm,
2
2
2
1F, JFF = 263.2 Hz, CF2), -108.3 (AB, dm, 1F, JFF = 263.2 Hz, CF2), -210.3 (dm, 1F, JFH
=
1
34.8 Hz, CHF). (3Z)-1,1,1,2,3,5,5-Heptafluorohex-3-ene (18). H NMR (500 MHz, CDCl3): δ
3
2
3
1.88 (t, 3H, JHF = 15.2 Hz, CH3), 5.11 (dm, 1H, JHF = 37.2 Hz, CHF), 5.62 (dt, 1H, JHFtrans
=
27.6 Hz, 3JHF = 7.6 Hz, =CH); 19F NMR (376 MHz, CDCl3): δ -78.3 (m, 3F, CF3), -83.2 (m, 2F,
CF2), -203.3 (m, 1F, =CF), -205.3 (dm, 1F, 2JFH = 37.2 Hz, CHF).
19
Page 19 of 28

4.2.5. Synthesis of alkenes 19 and 20 via Wittig-type olefination.
4.2.5.1. 3,3,3,2-Tetrafluoropropan-1-al (21).
Olefin HFC-1225y (13.2 g, 0.1 mol) was bubbled through a solution of KOH (6.72 g,
0.12 mol) in 96% ethanol (60 mL) at 5–10 °C for 2–3 h. The resulting mixture was stirred at rt
overnight, poured into ice (125 g), an organic layer was separated and washed with water (20
19
mL) to give a mixture of 23:24:25 in a molar ratio ~13:2:1, based on F NMR. (Z)-1-ethoxy-
3
2,3,3,3-tetrafluoroprop-1-ene (23). 19F NMR (188 MHz, CDCl3): δ -71.1 (d, 3F, JFF = 16 Hz,
19
CF3), -167.2 (m, 1F, =CF). 3-Ethoxy-1,1,1,2,3-pentafluoropropane (24). F NMR (188 MHz,
2
2
CDCl3): δ -76.7 (m, 3F, CF3), -137.6 (dm, 1F, JFH = 62 Hz, OCHF), -213.5 (dm, 1F, JFH = 44
19
Hz, CHF). 3,3-Diethoxy-1,1,1,2-tetrafluoropropane (25). F NMR (188 MHz, CDCl3): δ -75.4
2
(m, 3F, CF3), -208.6 (dm, 1F, JFH = 48.9 Hz, CHF). This mixture (14.3 g) without any
purification was added to heptanoic acid (20 g), admixed with 0.3 g H2SO4 and heated at 110–
120 °C for 6 h. Propanal 21 was distilled off resulting mixture (9.4 g, 72.3%) as a colorless
liquid: bp 46–48 °C. 1H NMR (300 MHz, CDCl3): δ 5.0 (dq, 1H, 2JHF = 47.1 Hz, 3JHF = 6.6 Hz,
CHF), 9.7 (d, 1H, 3JHF = 5.5 Hz, O=CH); 19F NMR (188 MHz, CDCl3): δ -75.1 (t, 3F, 3JFH = 6.6
Hz, CF3), -213.7 (dm, 1F, 2JFH = 47 Hz, CHF); 13C NMR (125 MHz, CDCl3): δ 88.4 (dq, 1JCF
=
193.5 Hz, 2JCF = 33.4 Hz, CHF), 119.8 ( qd, 1JCF = 280.6 Hz, 2JCF = 25.2 Hz, CF3), 189.1 (d, 2JCF
= 28.8 Hz, C=O). Aldehyde 21 gave 2,4-dinitrophenylhydrazone: mp 112–113 °C (hexane).
4.2.5.2. 3,3,3-Trifluoropropan-1-al (22).
Synthesis was performed in 100-ml autoclave under autogenous pressure with agitation.
The autoclave was charged with a mixture of KOH (11.2 g, 0.2 mol) and Bu4NCl (0.55 g, 20
mmol) in 96 % ethanol (40 mL), cooled to -196 °C, evacuated and olefin HFC-1234-yf (11.4 g,
0.1 mol) was then condensed. The autoclave was closed and allowed to agitate at 125–130 °C for
5 h, then cooled to rt and volatile materials were transferred in a trap (-78 °C) to give unchanged
starting olefin (1.3 g). The reaction mixture from autoclave was poured into ice, an organic layer
was separated, washed with water and dried to give a mixture of 26 [16b,c] and 27 [16b,c] (13.6
20
Page 20 of 28

g) in a molar ratio ~11:2, based on 19F NMR. Propanal 22 was isolated as it was described above
for propanal 21 (6,4 g, 64%) as a colorless liquid: bp 54–56 °C (Lit. 56–56.5 °C [22]; 56 °C
[23]). All NMR data were in accordance with published results [24].
4.2.5.3. (1Z)-1,3,4,4,4-Pentafluorobut-1-ene (19).
Method A. Modified Burton`s method [18] was used to prepare phosphonium salt 28 via
-
fluorination of [Ph3PCH2OH]+BF4 with DAST analogue – 4-(trifluoro-λ4-sulfanyl)morpholine.
The argon atmosphere was maintained throughout the system during experiment. A mixture of
28 (3.8 g, 10 mmol) and dry THF (25 mL) was cooled to -90 °C and to resulting slurry 1M
solution LHMDS in THF (10 mL, 10 mmol) was added dropwise under intensive stirring at such
a rate to maintain temperature ≤-80 °C. Resulting clear solution was stirred at -85 °C for 30 min
and then freshly distilled 21 (1.43 g, 11 mmol) was added via a syringe. The reaction was
allowed to proceed for 1 h at this temperature and then overnight at 5 °C. All volatile products
were distilled off in a trap (-78 °C) to give a solution of 19 in THF, based on NMR data.
Fractionation of this solution with an effective column gave fraction (1.5 g, bp 28–35 °C),
contained 19 (~60%) and THF (~40%), based on GLC analysis.
Method B. To monofluorinated ylide 30, obtained according to Burton`s method [19]
from Bu3P (18.2 g, 90 mmol) and CFCl3 (4.12 g, 30 mmol) in anhydrous benzonitrile (40 mL)
was added freshly distilled 21 (4.29 g, 33 mmol) via a syringe at 0-5 °C, and the mixture was
stirred for 30 min at ≤10 °C. At this temperature aqueous 10% NaOH (30 mL) was added to the
resulting solution, and the reaction was stirred at rt overnight. The organic layer was separated,
washed with brine and dried with MgSO4. All volatile products were distilled off in a trap
(-196 °C) in vacuo. The resulting condensate was then fractionated with a short column at
atmospheric pressure to give pure 19 (2.66 g, 61%) as a highly volatile liquid: bp 29.5–31 °C. 1H
3
3
3
NMR (300 MHz, CDCl3): δ 5.13 (dqd, 1H, JHFtrans = 37.2 Hz, JHF = 9.2 Hz, JHH = 5.0 Hz,
=CH), 5.57 (dm, 1H, 2JHF = 45.5 Hz, CHF), 6.78 (ddd, 1H, 2JHF = 80.6 Hz, 3JHH = 5.0 Hz, 4JHF
=
3
3.0 Hz, =CHF); 19F NMR (376 MHz, CDCl3): δ -80.4 (dm, 3F, JFF = 14.4 Hz, CF3), -116.9
21
Page 21 of 28

2
3
2
13
(ddm, 1F, JFH = 80.6 Hz, JFH = 37.2 Hz, =CFH), -194.5 (dm, 1F, JFH = 45.5 Hz, CHF); C
1
2
4
NMR (125 MHz, CDCl3): δ 80.5 (dqd, JCF = 181.0 Hz, JCF = 37.0 Hz, JCF = 8.5 Hz, CHF),
101.7 (d, 2JCF = 22.2 Hz, =CH), 122.0 (qd, 1JCF = 280.7 Hz, 2JCF = 28.5 Hz, CF3), 154.8 (dd, 1JCF
= 274.1 Hz, 3JCF = 10.8 Hz, =CFH). NMR spectra showed ~ 3% E-isomer: 1H NMR (300 MHz,
2
3
CDCl3): δ 6.99 (dd, 1H, JHF = 78.8 Hz, JHH = 11.3 Hz, CHF), other signals are overlapped by
19
2
3
Z-isomer signals; F NMR (376 MHz, CDCl3): δ -113.7 (ddm, 1F, JFH = 78.8 Hz, JFH = 15.5
Hz, =CFH), -191.3 (dm, 1F, 2JFH = 45.8 Hz, CHF), CF3 signal is overlapped by Z-isomer one.
4.2.5.4. (1Z)-1,4,4,4-Tetrafluorobut-1-ene (20).
Olefin 20 was prepared in analogy with the synthesis of butene 19 using Method B.
From propanal 22 (3.70 g, 33 mmol) pure olefin 20 (2.42 g, 63%) was obtained as a highly
1
volatile liquid: bp 24-26°C. H NMR (300 MHz, CDCl3): δ 2.94 (m, 2H, CH2), 4.87 (ddt, 1H,
3JHF = 39.2 Hz, 3JHH = 7.5 Hz, 3JHH = 4.1 Hz, =CH), 6.66 (dd, 1H, 2JHF = 83.2 Hz, 3JHH = 4.1 Hz,
=CHF); 19F NMR (376 MHz, CDCl3): δ -67.3 (t, 3F, 3JFH = 10.5 Hz, CF3), -125.0 (dd, 1F, 2JFH
83.2 Hz, 3JFH = 39.2 Hz, =CFH); 13C NMR (125 MHz, CDCl3): δ 28.3 (qd, 2JCF = 32.5 Hz, 3JCF
=
=
7.0 Hz, CH2), 99.6 (m, =CH), 125.5 (q, 1JCF = 276.0 Hz, CF3), 151.4 (d, 1JCF = 264.1 Hz, =CHF).
4.2.6. . Synthesis of alkene 33.
4.2.6.1. 1,1,1,2,2,3,3,5-Octafluoro-5-iodopentane (34).
Synthesis was performed in 100-ml autoclave under autogenous pressure with agitation.
The autoclave was charged with C3F7I (16.23 g, 54 mmol) and benzoyl peroxide (0.3 g), cooled
to -196 °C, evacuated, and fluoroethene (1.6 g, 32 mmol) was then condensed. The autoclave
was closed and allowed to agitate at 110–120 °C for 4 h, then cooled to rt and volatile materials
were collected in a trap (-50 °C) to give unchanged C3F7I (3 g). The reaction mixture from
autoclave was distilled with a short column to yield pentane 34 (8.76 g, 80 %) as a colorless
1
liquid: bp 118 °C. H NMR (400 MHz, CDCl3): δ 2.99 (m, 1H, CH2), 3.34 (AB, m, 1H, CH2),
2
3
3
7.12 (ddd, 1H, JHF = 50.4 Hz, JHHa = 9.4 Hz, JHHb = 2.0 Hz, CHFI); 19F NMR (376 MHz,
22
Page 22 of 28

4
2
CDCl3): δ -81.2 (t, 3F, JFF = 6.4 Hz, CF3), -114.0 (AB, dm, 1F, JFF = 268.3 Hz, CF2), -116.4
(AB, dm, 1F, 2JFF = 268.3 Hz, CF2), -128.6 (s, 2F, CF2), -142.1 (m, 1F, CFHI).
4.2.6.2. (1E/Z)-1,3,3,4,4,5,5,5-Octafluoropent-1-ene (33).
Iodide 34 (13 g, 38 mmol) was slowly added under stirring to the solution of KOH (24 g)
and Bu4NCl (0.6 g) in water (56 mL) at 90–100 °C. Heating was continued for 1 h. All volatiles
were collected through a condenser in a trap (-78 °C). Resulting condensate was dried with
MgSO4 and then distilled to give 33 (5.68 g, 68%) as a mixture of E/Z isomers in a ratio
~3/1, based on NMR. Olefin 33 was obtained as a colorless volatile liquid: bp 36–38 °C. E-
isomer: 1H NMR (300 MHz, CDCl3): δ 5.64 (ddt, 1H, 3JHFcis ≈ 3JHF ≈ 3JHHtrans ≈ 11-13 Hz, =CH),
2
3
4
7.24 (ddt, 1H, JHF = 77.5 Hz, JHH = 11.3 Hz, JHF = 2.2 Hz, =CHF); 19F NMR (376 MHz,
4
2
CDCl3): δ -80.9 (t, 3F, JFF = 9.5 Hz, CF3), -112.3 (m, 2F, =CCF2), -115.5 (dd, 1F, JFH = 77.5
Hz, 3JFH = 14.0 Hz, =CFH), -128.4 (s, 2F, CF2); 13C NMR (125 MHz, CDCl3): δ 102.7 (td, 2JCF
=
=
1
2
1
23 Hz and 19 Hz, =CH), 108.3 (tm, JCF = 264 Hz, JCF = 3JCF = 37 Hz, CF2), 113.9 (tm, JCF
250.0 Hz, CF2), 117.6 (qt, 1JCF = 287.3 Hz, 2JCF = 34.1 Hz, CF3), 157.7 (dt, 1JCF = 275.1 Hz, 3JCF
= 12.8 Hz, =CFH).
Z-isomer: 1H NMR (300 MHz, CDCl3): δ 5.09 (dtd, 1H, 3JHF = 36.3 Hz, 3JHF = 14.0 Hz, 3JHHcis
=
2
3
4
19
5.6 Hz, =CH), 6.82 (ddt, 1H, JHF = 76.7 Hz, JHH = 5.6 Hz, JHF = 1.7 Hz, =CHF); F NMR
4
(376 MHz, CDCl3): δ -81.1 (t, 3F, JFF = 9.5 Hz, CF3), -108.2 (m, 1F, =CFH), -109.7 (bs, 2F,
=CCF2), -128.8 (s, 2F, CF2); 13C NMR (125 MHz, CDCl3): δ 100.3 (t, 2JCF = 26 Hz, =CH),
1
106–122 (multiplied signals of C3F7 group are overlapped by those of E-isomer), 155.2 (dt, JCF
= 285.1 Hz, 3JCF = 7.0 Hz, =CFH).
4.2.7. 1,1,3,4,4,4-Hexafluorobut-1-ene (35).
Method C. The argon atmosphere was maintained throughout the system during the
experiment. Ph3P (10.5 g, 40 mmol) was dissolved in oxygen free anhydrous DMAA (20 mL),
and CF2Br2 (8.4 g, 40 mmol) was then added in one installment at 10 °C under intensive stirring.
A voluminous precipitate formed immediately. After stirring resulting mixture for 1 h at rt,
23
Page 23 of 28

propanal 21 (2.6 g, 20 mmol) was dropped in, and activated Zn powder (2.6 g, 40 mmol) was
then added in small dosages when immediately an exothermic reaction occurred, turning the
reaction mixture dark brown. Evolving gas was condensed in a trap (-40 °C). The reaction
mixture was heated at 100-110°C until the gas evolution stopped (~1 h). Fractional distillation of
a condensate gave in a trap -14 °C the pure olefin 35 (1.2 g, 37% in terms of propanal 21) as a
1
2
gas: bp 12–14 °C. H NMR (300 MHz, CDCl3): δ 4.6 (m, 1H, =CH), 5.3 (dm, 1H, JHF = 45.6
19
Hz, CHF); F NMR (376 MHz, CDCl3): δ -76.7 (m, 1F, =CF2), -79.6 (m, 1F, =CF2), -80.8 (m,
2
13
3F, CF3), -189.9 (dm, 1F, JFH = 45 Hz, CHF); C NMR (125 MHz, CDCl3): δ 72.0 (m, CH=),
1
2
4
1
81.5 (dqd, JCF = 182.8 Hz, JCF = 37.1 Hz, JCF = 10.4 Hz, CHF), 121.4 (qd, JCF = 278.6 Hz,
2JCF = 29.0 Hz, CF3), 159.5 (td, 1JCF = 295.0 Hz, 3JCF = 12.4 Hz, CF2=).
Method D. The argon atmosphere was maintained throughout the system during
experiment. Ph3P (42.0 g, 160 mmol) was dissolved in oxygen free anhydrous diglyme (220
mL) and CF2Br2 (16.8 g, 80 mmol) was then added in one installment at rt under intensive
stirring. A voluminous precipitate formed immediately. Resulting mixture was stirred at rt
overnight and then heated to 110 °C when the precipitate dissolved turning the reaction mixture
into a dark clear solution. Freshly distilled propanal 21 (10.4 g, 80 mmol) was added slowly to
this solution. Evolving gas was condensed in a trap (-40 °C). Resulting mixture was stirred at
110–115 °C for 2 h, cooled to rt and all volatile products were then condensed in a trap (-196 °C)
in vacuo. Combined condensates from both traps consisted of olefin 35 and CF2HBr in a ratio
19
~7/3 due to F NMR. Gases from these condensates were slowly bubbled through a solution of
Br2 (12.8 g, 80 mmol) in anhydrous CHCl3 (100 mL) at rt and “sun light” irradiation for 1 h.
Resulting mixture was worked up with aqueous Na2SO3 and water, dried with MgSO4 and
fractionated to afford 1,2-dibromo-1,1,3,4,4,4-hexafluorobutane (38) (17.8 g, 68.5 %), as a
mixture of two diastereoisomers in a ratio ~5/2: bp 124–125 °C. 1H NMR (400 MHz, CDCl3): δ
2
4.46 (m, 0.3H, CHBr), 4.58 (m, 0.7H, CHBr), 5.08 (dm, 0.3H, JHF = 45.6 Hz, CHF), 5.27 (dm,
0.7H, 2JHF = 46.0 Hz, CHF); 19F NMR (188 MHz, CDCl3): δ -45.9 (m, 0.6F, CF2), -47.8 (AB, d,
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0.7F, 2JFF = 165.2 Hz, CF2),-52.5 (AB, d, 0.7F, 2JFF = 165.2 Hz, CF2), -74.6 (s, 0.9F, CF3), -76.8
(s, 2.1F, CF3), -189.4 (m, 0.3F, CFH), -203.2 (m, 0.7F, CFH). A suspension of Zn dust (7.14 g,
110 mmol) in anhydrous iso-propanol (20 mL) was heated at 35 C under stirring and dibromide
38 (17.8 g, 55 mmol) was then dropwise added. Evolved gaseous products were trapped at -30
C (~2 h) and then fractionated to give olefin 35 (8.5 g, 50% in terms of aldehyde 21).
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Graphical abstract
Alternative Synthetic Routes to Hydrofluoro Olefins
Yu. L. Yagupolskii, N.V. Pavlenko, S.V. Shelyazhenko, A.A. Filatov, M.M. Kremlev, A.I.
Mushta, I.I. Gerus, Sheng Peng, V. A. Petrov, Mario Nappa
A series of novel low boiling
hydrofluoroolefins with terminal -
CF=CH2, -CH=CHF and -CH=CF2
groups have been prepared via
various synthetic routes
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