Synthesis of trifluoromethylated heterocycles using partially fluorinated epoxides

Article abstract of DOI:10.1016/j.jfluchem.2010.11.003

Reaction of 2-trifluoromethyl- (1) and 2,2-bis(trifluoromethyl)- (2) oxiranes with a variety of sulfur nucleophiles proceeds rapidly and under mild conditions. For example, epoxide 2 reacts with aqueous solution of Na ₂S, producing S[CH₂

Full text of DOI:10.1016/j.jfluchem.2010.11.003

Journal of Fluorine Chemistry 132 (2011) 41–51
Contents lists available at ScienceDirect
Journal of Fluorine Chemistry
journal homepage: www.elsevier.com/locate/fluor
Synthesis of trifluoromethylated heterocycles using partially
fluorinated epoxides
b
Viacheslav A. Petrov a, , Will Marshall
*
a DuPont CR&D, Experimental Station, PO Box 80500, Wilmington, DE 19880-0500, United States1
b DuPont Corporate Center for Analytical Sciences, Experimental Station, PO Box 80500, Wilmington, DE 19880-0500, United States
A R T I C L E I N F O
A B S T R A C T
Article history:
Reaction of 2-trifluoromethyl- (1) and 2,2-bis(trifluoromethyl)- (2) oxiranes with a variety of sulfur
nucleophiles proceeds rapidly and under mild conditions. For example, epoxide 2 reacts with aqueous
solution of Na2S, producing S[CH2C(CF3)2OH]2. Reaction of 2 with Na2S2O3 leads to the formation of the
corresponding Bunte salt. Interaction of 2 with NaSCN in water proceeds exothermically and results in
high-yield formation of cyclic imine 5. Although this material can be isolated, it has limited stability and
undergoes cyclotrimerization at ambient temperature, giving the corresponding 1,3,5-triazine. A
number of heterocyclic compounds containing pendant –CH2C(CF3)2OH group were prepared by the
reaction of the corresponding thio-derivatives, such as pyridine-2-thiole with epoxide 2. It was found
that fluoride anion catalyzes the reaction of epoxides 1 and 2 with isothiocyanates carrying electron
withdrawing groups at nitrogen. The reaction results in nucleophilic cyclization and formation of the
corresponding exocyclic imines containing a 1,3-oxothiolane moiety. Carbon disulfide was also found to
be active in this process, reacting with epoxides 1 and 2 at ambient to give the corresponding
trifluoromethylated 1,3-oxathiolane-2-thiones in 58–65% yield.
Received 28 August 2010
Received in revised form 8 November 2010
Accepted 9 November 2010
Available online 16 November 2010
Keywords:
2-Trifluoromethyloxirane
2,2-Bis(trifluoromethyl)oxirane
Nucleophilic cyclization
Sodium thiocyanate
Aryl isothiocyanates
Carbon disulfide
ß 2010 Elsevier B.V. All rights reserved.
1. Introduction
2. Results and discussion
2-Trifluoromethyl- (1) and 2,2-bis(trifluoromethyl)- (2) oxi-
ranes have high reactivity towards nucleophilic reagents and were
reported to react under relatively mild conditions with a variety of
nucleophilic [1–6] and electrophilic reagents [1,5,7]. Although the
epoxide 2 under basic conditions undergoes polymerization [8]
and living co-polymerization with CH2(O)C(CF3)CF2OCH2CF3 [9] it
still is able to react with variety of nucleophiles. Sulfur
nucleophiles seem to have high reactivity towards this oxirane.
For example, 2 was reported to react with C6F13(CH2)2SH in the
absence of the catalyst at ambient temperature, producing
C6F13(CH2)2SCH2C(CF3)2OH [5].
2.1. Reaction of 2,2-bis(trifluoromethyl)oxirane (2) with Na2S,
Na2S2O3 and thiocyanates salts
The reaction of 2 with aqueous solution of Na2S proceeds
exothermally producing sulfide 3, isolated in 66% yield after
acidification of the reaction mixture (Scheme 1).
Parameters of 1H and 19F NMR spectral data for sulfide 3 are in a
good agreement with data reported by the Shreeve group [10] for
the material prepared through the photochemical reaction of
hexafluoroacetone and (CH3)2S (0 8C, 3d, 52% yield). We found that
the melting point of purified 3 (74–75 8C) is higher compared to
reported value (52 8C [10]), which may be attributed to higher
purity of material prepared in this study. The oxidation of 3 by
hydrogen peroxide proceeds under mild conditions, resulting in
selective formation of sulfoxide 3a (Scheme 2).
In this study high reactivity of epoxides 1 and 2 towards sulfur
nucleophiles was exploited and was applied for the synthesis of
different types of trifluoromethylated heterocycles and com-
pounds containing –S–CH2C(CF3)2OH groups.
The fact that the oxidation can be carried out under relatively
mild conditions may be attributed to the presence of –C(CF3)2OH
groups in sulfide 3, since the accelerating effect of hexafluoro-iso-
propanol on oxidation of hydrocarbon olefins and
sulfides by H2O2 was discovered and studied in details by the
Bonnet-Delpon group [11,12].
b-hydroxy
* Corresponding author. Tel.: +1 302 695 1958.
E-mail address: viacheslav.a.petrov@usa.dupont.com (V.A. Petrov).
1
Publication No. 2010-161.
0022-1139/$ – see front matter ß 2010 Elsevier B.V. All rights reserved.
doi:10.1016/j.jfluchem.2010.11.003

[
V.A. Petrov, W. Marshall / Journal of Fluorine Chemistry 132 (2011) 41–51
I
CF3
O
F3C
F3C
H2O
CF3
O
S[CH2C(CF3)2OH]2
F3C
+ Na2S
M
CN
F3C
H2O
20-28oC,
2h
2 + MSCN
N M
O
S
3, 66%
S
2
B
A
Scheme 1. Reaction of 2 with Na2S.
[()TD$FIG]
CF3
O
-OCN
F3C
F3C
F3C
30% H2O2
CN
3
O=S[CH2C(CF3)2OH]2
CH2Cl2
S
M
S
25oC, 48h
3a, 51%
D
C
Scheme 2. Preparation of sulfoxide 3a.
[()TD$FIG]
Scheme 5. Mechanism of the reaction of 2 with MSCN.
[)(TD$FIG]
H2O, cat.
25oC, 2h
2 + Na2S2O3
[NaOSO2SCH2C(CF3)2OH]
(C4H9)4N+ HSO4
CF3
-
F3C
O
H2O
SCH2C(CF3)2OH
5a
2
+NaSCN
(C4H9)4N+ -OSO2SCH2C(CF3)2OH
25oC,3d
N
,10%
4, 90%
Scheme 6. Reaction of 2 with KSCN in H2O.
+NaHSO4
[)(TD$FIG]
cat. - (C4H9)4N+ HSO4
-
THF
2 + NaSCN
Scheme 3. Reaction of 2 with Na2S2O3.
1) 25oC, 16h
2) H+
[()TD$FIG]
CF3
O
CF3
O
F3C
NH . [SCH2C(CF3)2OH]2
+ others
F3C
H2O
2
+ 3
+ NaSCN
NH
S
1) 25oC, 2h
2) H+
S
5b
,
5, 90%
yield 30%
5 : 3
ratio
- 95:5
Scheme 7. Reaction of 2 with NaSCN in THF solvent.
Scheme 4. Reaction of 2 with NaSCN in water (25 8C, 2 h).
Despite low solubility of 2 in water, it is an excellent solvent for
The formation of an intermediate, structurally similar to
the reaction of epoxide 2 with sulfur nucleophiles. For example, the
reaction of Na2S2O3 with 2 in the presence of phase transfer
catalyst proceeds exothermally giving insoluble Bunte salt 4,
(Scheme 3), using the procedure which was employed by
Middleton for preparation of Bunte salts of hexafluorothioacetone
[13].
compound 5, was previously postulated for the reactions of
hydrocarbon epoxides with thiocyanate salts [14,15]. However, in
this case the intermediate rapidly undergoes conversion into the
episulfide. The reaction of 2 with thiocyanates salts stops at stage
of cyclic imine salt. The formation of salt B (see Scheme 5) is the
result of intramolecular attack of alkoxy anion on the carbon of –
CN group. The salt B probably exists in equilibrium with A (see also
Scheme 9), however, the reason why B it is not converted into
episulfide D is not clear. It is possible, that the intermediate B for
some reasons does not undergo isomerization into cyanate C or
intramolecular attack of sulfide anion on this cyclization of C
leading to episulfide D for some reason is blocked.2
The reaction time has a significant effect on the outcome of this
process. When time for the reaction of 2 with aqueous solution of
NaSCN was extended to 2d, originally formed salt of 5 (in this
experiment the formation of salt B (M55Na) was confirmed by
NMR) underwent further transformations, leading to a mixture of
several products. Compound 5a was isolated in low yield from the
organic layer after ꢀ12 h (see Scheme 9 for mechanism of
formation of 5a). Isolated material was characterized by NMR
and IR spectroscopy and the structure 5a was supported by single
crystal X-ray diffraction data (Scheme 6).
The structure of compound 4 was firmly established by single
crystal X-ray diffraction data (Fig. 1).
An interesting result was obtained in the reaction of 2 with
ambivalent nucleophiles, such as thiocyanate salts. The reaction
was explored as a potential route to 2,2-bis(trifluoromethyl)epi-
sulfide, since this type of transformation is widely used for the
preparation of hydrocarbon thiiranes [14]. The addition of 2 to a
water solution of NaSCN was exothermic, resulted in fast
disappearance of epoxide layer and the formation of a homoge-
neous solution. Upon the acidification of the reaction mixture with
a saturated aqueous solution of ammonium chloride, followed by
extraction with ether or dichloromethane, the product 5 was
isolated in 90% yield. The crude product had a typical purity of
ꢀ95% and was contaminated by a small amount (ꢀ5%) of sulfide 3
(NMR, GC/MS) (Scheme 4).
Based on combined 1H and 19F NMR, IR and GC/MS data, the
structure of cyclic imine 5 was assigned to the major product of
this reaction and the structure was confirmed by single crystal X-
ray diffraction data (Fig. 2).
The choice of solvent is very important for the reaction of
epoxides with thiocyanate salts. While, the reaction of hydrocar-
bon epoxides with NH4SCN in CH3CN proceeds at elevated
The reaction of 2 with KSCN or NH4SCN also proceeds under
mild conditions and results in the formation of 5 as a principal
product, although the reaction with KSCN seems to be slower and
less exothermic. It should be also pointed out that the process is
limited to epoxide 2, since the reaction of 2-trifluoromethyloxirane
(1) and NaSCN resulted in rapid polymerization of epoxide.
2
The factors preventing the formation of episulfide in this process are not well
understood. The explanation involving steric hindrance of the carbon bearing two
bulky CF3-groups towards intramolecular attack of sulfide anion would be tempting
intramolecular backside attack by neighboring sulfur nucleophile is presumably
one of the most favorable setups for nucleophilic displacement.

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V.A. Petrov, W. Marshall / Journal of Fluorine Chemistry 132 (2011) 41–51
43
[
Fig. 1. Thermal ellipsoid drawing of 4 with ellipT soids drawn to the 50% probability level.
[()D$FIG]
SR
25oC,6 days
N
N
5
RS
SR
6, quant.
R= - CH2C(CF3)2OH
N
Scheme 8. Trimerization of imine 5.
d
= 165.3 ppm in 5). The IR spectrum of 6 exhibits a strong
absorption at 1661 cmÀ1. Data of 13C and IR-spectroscopy of 6 are
in good agreement with values reported for hydrocarbon triazines
of similar structure [19]. Final proof of the structure comes from
[)(TD$FIG]
single crystal X-ray diffraction (see Fig. 4).
+ M+ SCN-
2
CF3
F3C
O
N-M+
Fig. 2. Thermal ellipsoid drawing of 5 with ellipsoids drawn to the 20% probability
S
SR
level.
B
N
N
NCS-CH2C(CF3)2O-M+
H+
temperature and results in clean formation of
b-hydroxy
RS
SR
N
A
thiocyanates [16], the similar process involving 2 and NaSCN in
THF or DMF solvent leads to the formation of a rather complex
mixture, in which compound 5b was identified as major
component (Scheme 7). The structure of 5b was established by
single crystal X-ray diffraction. The identity of the crystal used for
structure determination and the bulk of isolated crystalline
material was confirmed by powder X-ray diffraction experiment.
Limited number of complexes between acidic fluoroalcohols is
known (see, for example, Refs. [17,18]) and compound 5b is
another example of the stable material formed as the result of
relatively strong intermolecular hydrogen bonding between the
acidic –C(CF3)2OH group and the basic 55N–H fragment (O–HÁ Á ÁN
5
6
[S=C=N-CH2C(CF3)2O-M+
E
CF3
F3C
O
S-M+
N
F
2
CF3
O
˚
F3C
distance of =2.64 A). The internal hydrogen bonding in 5b is
SCH2C(CF3)2O-M+
depicted in Fig. 3.
N
Isolated compound 5 has a limited stability and even at À25 8C
slowly undergoes cyclotrimerization. At ambient temperature this
process is much faster leading in several days to the quantitative
conversion of 5 into 6 (Scheme 8).
G
H+
Compound 5 was distilled under reduced pressure, but the
isolated yield did not exceed 40%, due to competitive formation of
6 at elevated temperature. 1H and 19F NMR of 5 and 6 are virtually
identical, although in 13C spectra of 6 the resonance of the carbon
5a
R= -CH2C(CF3)2OH
of triazine ring is shifted substantially downfield (
d
= 180.0 ppm vs.
Scheme 9. Mechanism of formation compounds 5a and 6.

[
V.A. Petrov, W. Marshall / Journal of Fluorine Chemistry 132 (2011) 41–51
Fig. 3. Thermal ellipsoid drawing of 5b with ellipsoids drawn to the 20% probability level.
[()TD$FIG]
Fig. 4. Thermal ellipsoid drawing of 6 with ellipsoids drawn to the 50% probability level.

V.A. Petrov, W. Marshall / Journal of Fluo
[
rine Chemistry 132 (2011) 41–51
45
THF or
DMF
The reaction of 2 with HSCN (generated by reaction of KSCN
with sulphuric acid [15] in ether) proceeds in the absence of
catalyst (0–25 8C, 16 h) leading to the formation of a mixture
containing compounds 3, 5 and 6 as major components (ratio
17:54:27, NMR, GC/MS).
The formation of compounds 5, 5a and 6 in reaction of 2 with
thiocyane salts can be explained by the existence of equilibrium
between salts A and B (Scheme 9).
HN
2 + S=C(NH2)2
SCH2C(CF3)2OH
H2N
8
9, 95%
t-BuOK
DMF
0-20oC
1) NaOH,
H2O
2) H+
Obviously, the trimerization of thiocyanate A is responsible for
the formation of triazine 6. The formation of compound 5a is the
result of consecutive transformations including thiocyanate–
isothiocyanate rearrangement of A into E, followed by reversible
intramolecular cyclization of E into F and the reaction of F with a
second mole of 2 leading to adduct G, which is getting converted
into 5a after acidification. The difference in the yields and rates of
formation of compounds 5 and 5a (2 h vs. 3 days) suggests that the
formation of salts A and B, is fast but the rate of the formation 5a is,
limited by relatively slow thiocyanate–isothiocyanate rearrange-
ment of A into E.
[K+ -SCH2C(CF3)2OK]
HSCH2C(CF3)2OH
10a
10, 90%
1)60oC, 12h
2)H+
C6F13
I
C6F13SCH2C(CF3)2OH
11, 60 %
Scheme 11. Reaction of 2 with thiourea.
[)(TD$FIG]
N
Indirect evidence for possible formation of the intermediate A
was obtained in a reaction of 2 and trimethylsilylisothiocyanate.
The reaction proceeds slowly at ambient temperature in the
absence of solvent, leading to a clean and selective formation of
thiocyanate 7 (see Scheme 10).
SR
18, 73%
O
O
N
13
N
S
12
16
RS
SR
14
2
17, 95%
The structure of thiocyanate 7 is consistent with data of both IR
(sharp absorption at 2163 cmÀ1 cf. 2140 cmÀ1 for alkyl thiocya-
19, 91%
15
nates [20]) and 13C NMR, spectroscopy (7, –S–CN,
d
= 110.16 ppm,
= 112.1 and 127.8 ppm for C2H5SCN and C2H5NCS, respectively
[21,22]). Interestingly, compound has significantly higher
N
SR
N
cf.
d
SR
N
20, 64%
7
21, 90%
stability compared to compound 5. It can be handled and stored
at ambient temperature and distilled under reduced pressure
without any signs of trimerization. A liquid sample of 7, stored in a
glass sample vial at ambient temperature for ꢀ6 months
underwent a partial conversion (ꢀ10 wt.% of sample) into a solid
material, which was filtered and identified by single crystal X-ray
diffraction as 7a, but was not further characterized.
Remarkably rapid conversion of isolated 5 into 6 probably,
should involve isomerization of 5 into CNSCH2C(CF3)2OH, followed
by its trimerization to form 6. It should be pointed out, that
trimerization of hydrocarbon thiocyanates usually requires a cataly-
sis. For example, as it was reported [19] CH3SCN undergoes
trimerization in the presence of triflic anhydride catalyst. It is
possible that the conversion of 5 into 6 is catalyzed by an acidic –
C(CF3)2OH group which is present in intermediate CNSCH2C(CF3)2
OH. Significantly higher stability of CNSCH2C(CF3)2OSi(CH3)3 (7)
towards trimerization agrees well with this hypothesis.
DMF, 25-30oC, 2-4h;
R=-CH2C(CF3)2OH
O
HS
N
X
SH
N
X
SH
N
13, X= O
14
12
15, X=CH
16, X=N
, X= S
Scheme 12. Preparation of heterocycles containing pendant –SCH2C(CF3)2OH
group.
10a and selective formation of sulfide 11. The mechanism of
perfluoroalkylation probably involves a single electron transfer
step, a process which is well established for the reaction of thiols
with RFI [28].
Perfluorinated epoxides were reported to react with thiourea
(8) to form heterocyclic products [23–27]. Epoxide 2 reacts with
8 in a different fashion, giving linear adduct 9 in 95% yield
(Scheme 11).
As expected the basic hydrolysis of 9 leads to thiol 10. The
treatment of 9 by t-BuOK in DMF solvent followed by reaction with
Epoxide 2 rapidly reacts with other sulfur nucleophiles. For
example, oxazolidine 12, benzoxa- (13) benzthia- (14) azoles,
pyridine 15 and pyrimidine 16 all react with epoxide 2 in the
absence of catalyst to form the corresponding sulfides 17–21
(Scheme 12).
CT F
13I at 50–80 8C results in perfluoroalkylation of intermediate
2.2. Reactions of epoxides 1 and 2 with aryl-, fluoroalkenyl-
isothiocyanates and carbon disulfide
6
25oC
Epoxides 1 or 2 were found to be inert towards aryl- and alkyl-
isothiocyanates in the absence of the catalyst at ambient
temperature. However, when the reaction of 2 and phenyl
isothiocyanate (22) was carried out in the presence of tetra-
butylammonium fluoride catalyst, it resulted in high yield
formation of imine 22a (Scheme 13).
The outcome of the reaction depends strongly on the choice of
the catalyst and the reactivity of isothiocyanate. While the use of
tetrabutylammonium fluoride catalyst led to a reasonable yield of
22a in the reaction of 2 with 22, – either triethylamine or CsF
catalyst caused rapid polymerization of epoxide 2. On the other
2 + SCNSi(CH3)3
NCS-CH2C(CF3)2OSi(CH3)3
THF or
DCM
25oC,
slow
7, 82%
S
CF3
O
CF3
N
F3C
O
S
CF3
CF3
S
N
O
CF3
7a
Scheme 10. Reaction of 2 with (CH3)3SiNCS.

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V.A. Petrov, W. Marshall / Journal of Fluo
F
rine Chemistry 132 (2011) 41–51
F3C
THF
cat.
C3F7
C2F5
CF3
O
N
C4F9
F3C
F3C
F
F
THF,
25oC,2h
2 + C6H5-NCS
N-C6H5
22a, 67%
4h, 25oC
22
S
+ KSCN
-KF
THF,
25oC,2h
+ KSCN
-KF
cat. - (C4H9)4N+F- . H2O
C3F7
F3C
F3C
C2F5
N
C4F9
Scheme 13. Reaction of 2 with C6H5NCS.
[()TD$FIG]
N=C=S
26
N=C=S
25
CH3CN
CsF
CF3
THF,
25oC,
16h
THF,
25oC,
16h
O
F3C
2
2
N-C6F5
, 70%
2
+ C6F5-NCS
S
23a
2h, 25-35oC
23
C4F9
N
F3C CF3
F3C
F3C
F3C
Scheme 14. Reaction of 2 with C6F5NCS catalyzed by CsF.
O
O
S
F3C
C3F7
C2F5
N
N
[()TD$FIG]
S
THF,
F3C
26a, 46%
25a, 45%
cat.
F3C
O
+ 23
N-C6F5
, 73%
25oC,
Scheme 17. Reaction of 2 with isothiocyanates 25 and 26.
O
1
S
1 week
23b
reaction with KSCN in DMF, Scheme 17) rapidly react with 2 giving
of the corresponding cyclic imines 25a and 26a, respectively.
The reactions were carried out as one-pot process, in the
absence of added catalyst, since required for this reaction KF was
generated in the first step of the process.
cat. - (C4H9)4N+F- . H2O
Scheme 15. Reaction of 1 with pentafluorophenylisothiocyanate.
The possible mechanism of the reaction of isothiocyanates 22a,
23a, b, 24a, b, 25 and 26 with fluorinated epoxides (Scheme 18)
involves attack of fluoride anion on isothiocyanate resulting in the
formation of delocalized anion H. The reaction of H withepoxide 1 or
2 leads to alkoxy anion I and is followed by its intramolecular
cyclization into J. The elimination of fluoride anion leads to the
formation of cyclic imines 22a, 23a, b, 24a, b, 25a or 26a. Fluoride
anion released at this step drives another catalytic cycle.
Experimental data indicate that the electrophilicity of the
starting isothiocyanate plays an important role since only
relatively electron deficient aryl- or fluoroalkenyl-isothiocyanates
were found to be active in this process. All attempts to involve 2 in
reaction with alkyl isothiocyanates failed.
Carbon disulfide been previously shown to undergo [3 + 2]
cycloaddition with hydrocarbon epoxides. These reactions usually
carried out either in organic solvent or water and are catalyzed by
alkoxides [49], aluminium complexes [50] or tertiary amines [51].
We have demonstrated that fluorinated epoxides 1 and 2 react
with CS2 selectively forming the corresponding cycloadducts 27
and 28. The reaction proceeds under mild conditions and is
catalyzed by fluoride anion. The addition of CS2 to a solution of
hand, for the reaction of more electrophilic C6F5NCS (23) with 2 CsF
was found to an effective catalyst (Scheme 14).
Despite its lower nucleophilicity epoxide 1 reacts with 23
giving imine 23b (Bu4N+FÀ catalyst, Scheme 15).
This reaction although was significantly slower (1 week at
25 8C) compared to similar process involving epoxide 2 (see
Scheme 14). The same trend was observed in the reaction of
epoxides 1 and 2 with isothiocyanate 24 (Scheme 16). While
product 24a was isolated in moderate yield after 24 h, analogous
process involving 1 took ꢀ4 days.
Perfluorinated isothiocyanates 25 [29–31] and 26 [32] readily
prepared by the reaction of perfluoro(2-methyl)pentene-2 [33,34]
or perfluoro-4-aza-nonene-3 [35,36] with sodium thiocyanate
were used for the synthesis of a variety of fluorinated heterocycles
(see Refs. [37–48] and [32] for reactions of 25 for 26, respectively).
[()D$FIG]
IT n this study it was shown that both 25 and 26 (generated in situ by
CF3
O
F3C
N-Ar
S
[)(TD$FIG]
24a, 75%
CF3
X
THF, CsF
25oC, 24h
O
S
2
R-N
22a, 23a-b,
24a-b, 25a,
26a
F-
R-N=C=S
R-N=C-S
3-CF3-C6H4-NCS
24
CF3
X
O
S
THF, cat.
25oC, 4d
1
R-N
F
F
H
J
F3C
X
F3C
O
S
O
1 or 2
N-Ar
R-N=C-S
F
24b, 35 %
I
Ar=3-CF3-C6H4-
cat. - (C4H9)4N+F- . H2O
X=H or CF3
Scheme 16. Reaction of 1 and 2 with 3-(trifluoromethyl)phenylisothiocyanate.
Scheme 18. Mechanism of reaction of epoxides 1 and 2 with isothiocyanates.

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V.A. Petrov, W. Marshall / Journal of Fluorine Chemistry 132 (2011) 41–51
47
THF, cat.
CS2
S
dry box. C4F9N55CFC3F7 was prepared using literature procedure
[36]. Due to a high ratio of sulfur to fluorine, elemental analysis was
not attemptedfornew materialsprepared inthisstudy. The purity of
all isolated compounds was established by GC/MS and NMR
spectroscopy and it was at least 97%.
F3C
X
+
S
X
O
O
4-16h,
25oC
F3C
1
2
X=H
27, 65 %
28, 58%
X=CF3
Crystallography. X-ray data for 4, 5, 5b, 6 and 7a were collected
at À1008C using a Bruker 1K CCD system equipped with a sealed
tube molybdenum source and a graphite monochromator.
The structures were solved and refined using the Shelxtl [52]
software package, refinement by full-matrix least squares on F2,
scattering factors from Int. Tab. Vol. C Tables 4.2.6.8 and 6.1.1.4.
Crystallographic data (excluding structure factors) for the structures
in this paper have been deposited with the Cambridge Crystallo-
graphic Data Centre as supplementary publication nos. CCDC
#787678–787682. Copies of the data can be obtained, free of
charge, on application to CCDC, 12 Union Road, Cambridge CB2 1EZ,
UK (fax: +44 1223 336033 or e-mail: deposit@ccdc.cam.ac.uk).
cat. - (C4H9)4N+F- . H2O
Scheme 19. Fluoride anion catalyzed reaction of 1 and 2 with CS2.
[()TD$FIG]
CF3
O
X
S
S
F-
S=C=S
27, 28
CF3
O
S
X
S
S=C-S
F
F
K
4.1. Preparation of compound 3
F3C
X
O
S=C-S
F
1
2
or
24 g (0.1 mol) of Na2SÁ9H2O was dissolved in 150 mL of DI
water. The solution was placed in 250 mL flask equipped with
thermocouple, addition funnel, dry-ice condenser and magnetic
stir bar. Epoxide 2 (36 g, 0.1 mol) was slowly added to vigorously
agitated solution (mildly exothermic), at sufficient rate to maintain
an internal temperature <30 8C. The reaction mixture was cooled
down to ambient temperature and was agitated for an additional
2 h. It was poured into 300 mL of aqueous saturated solution of
NH4Cl. The precipitate was filtered off and air dried. 26 g (66%) of
slightly yellow solid was isolated and identified as sulfide 3. The
isolated material had a limited solubility in acetone, chloroform,
acetonitrile, but was readily soluble in basic water. Data for
compound 3 are given in Tables 1 and 2.
X=H or CF3
Scheme 20. Mechanism of reaction of epoxides 1 and 2 with CS2.
tetrabutylammonium fluoride in THF results in immediate
appearance of deep red colour, which rapidly disappears after
addition of epoxide. The reaction of epoxide 2 with CS2 is fast and
typically is completed within 2–3 h, but it takes >12 h under
similar conditions with epoxide 1 (Scheme 19).
The mechanism of fluoride anion catalyzed reaction of CS2 with
fluorinated epoxides similar to the mechanism suggested for
analogous process reported for hydrocarbon epoxides and cata-
lyzed by sodium methoxide [49] is depicted by Scheme 20.
4.2. Preparation of compound 3a
Compound 3 (1 g, 0.026 mol) was dissolved in 100 mL of CH2Cl2
and 5 mL of 30% H2O2 was added. The reaction mixture was
agitated for 48 h at ambient temperature. Organic layer was
separated and washed by 1 N aqueous solution of sodium
thiosulfate (3Â 200 mL, peroxide test was negative), dried over
MgSO4 and solvent was removed under vacuum to leave 0.51 g
(51%) of white solid identified as 3a. Data for compound 3a are
given in Tables 1 and 2.
3. Conclusion
The fluoride anion catalyzed reaction of 2-trifluoromethyl- (1)
and 2,2-bis(trifluoromethyl)- (2) oxiranes with sulfur nucleophiles
provides a simple and efficient method for the preparation of a
variety of heterocycles containing a variable number of trifluor-
omethyl or a pendant S–CH2C(CF3)2OH group(s). Most of these
reactions proceed under mild conditions, selectively producing the
corresponding materials in acceptable yields.
4.3. Preparation of compound 4
To an agitated mixture of sodium thiosulfate (16 g, 0.1 mol), 0.1 g
of (C4H9)4N+ HSO4À (phase transfer catalyst) and 100 mL of DI water
(placed in a flask equipped with thermocouple, addition funnel, dry
ice condenser and magnetic stir bar) 18 g (0.1 mol) of 2 was added at
a rate, that maintained an internal temperature at 25–30 8C. After
the separate layer of 2 completely dissolved, the reaction mixture
was agitated for 1 h and then it was poured into an aqueous solution
4. Experimental
1HNMRand 19F NMRspectrawererecordedonaBrukerDRX-500
(499.87 MHz) instrument using CFCl3 or TMS as internal standards.
Unless stated otherwise, CDCl3 was used as a lock solvent. IR spectra
were recorded on a PerkinElmer 1600 FT spectrometer (KCl plates,
liquid film or in KBr for solids). Moisture sensitive materials were
handled in a glove box, under nitrogen atmosphere. GC and GC/MS
analyses were carried out on a HP-6890 instrument, using HP FFAP
capillary column and TCD (GC) or mass selective (GS/MS) detectors,
respectively. KSCN, NaSCN, NH4SCN, Na2SÁ9H2O, CS2, Na2S2O3,
phenyl-, pentafluorophenyl-, 3-CF3-phenyl-isothiocyanates, thio-
urea, (CH3)3SiNCS, (C4H9)4N+FÀÁH2O, (C4H9)4N+ÁHSO4À, compounds
12–16, THF, CH3CN (Aldrich), (CF3)2C55CFC2F5, 2-(trifluoromethy-
l)oxirane (1, Synquest), C6F13I, 2,2-bis(trifluoromethyl)oxirane (2,
DuPont) were obtained from commercial sources and used without
further purification. CsF (Aldrich) was dried at 100–120 8C under
dynamic vacuum for 4–8 h and was stored and handled inside of the
of (C4H9)4N+ HSO4 (34 g (0.1 mol) in 200 mL of H2O). The thick
À
reaction mixture was agitated for 10 min, water was drained, and
the semi-sold residue was dissolved in 200 mL of acetone. The
solutionwasdriedoverMgSO4 and thesolventwasremovedtoleave
48 g (90%) of 4, which crystallized upon storage at ambient
temperature. Data for compound 4 are given in Tables 1 and 2.
4.4. Preparation of compound 5
To an agitated solution of 5 g (0.052 mol) KSCN in 50 mL of DI
water 10 g (0.55 mol) of 2 was slowly added at 25–28 8C (slightly
exothermic). After 2 h the organic phase disappeared and reaction

48
V.A. Petrov, W. Marshall / Journal of Fluorine Chemistry 132 (2011) 41–51
Table 1
Yields, melting (boiling) points, IR and MS data for new materials.
Entry no.
Comp.
Yield (%)
M.p. (8C) (b.p., 8C/mm Hg)
IR (cmÀ1
)
MS (m/z)
1
2
3a
66
51
90
73–75
–
–
–
394 (M+, C8H6F12O2S+)
410 (M+, C8H6F12O3S+)
–
239 (M+, C5H3F6NOS+
420 [(M+1)+, C9H6F12NO2S+]
–
3aa
4a
113–114b
195–197b
ꢀ20d (46–47/2)c
46–48b
3
4
5a
95c
10
3228, 1667e (C5N)
5
5aa
5ba
6a
1627f (C5N)
6
30
–
3330f (OH), 3011 (NH), 1652 (C5N)
7
100
82
95
90
119–120b
(94–95/15)
196–197b
–
3227f (OH), 1490 (C5N, triazine)
–
8
7
2163e (SCN)
238[(MÀC3H9Si)+, C5H2F6NSO+)
256 (M+, C5H6F6N2OS+)
214(M+, C4H4F6OS+)
532 (M+, C10H3F19OS+)
283, (M+, C8H9F6NO2S+)
9
9
–
–
–
–
–
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
10
11
60
(95–97/0.5)
62–64b
17
95g
73h
91h
64
90
18a
19
54–56b
331 (M+, C11H7F6NO2S+)
100–101b
36–37b
347 (M+, C11H7F6NOS2
291 (M+, C9H7F6NOS+)
292 (M+, C8H6F6N2OS+)
315(M+, C11H7F6NOS+)
)
+
20a
21
–
–
198–200b
32–33b (80/0.9)
50–52
22aa
23aa
23ba
24a
24ba
25a
26a
27a
28a,j
67
70
1683, 1675f (C5N)
1676f (C5N)
405 (M+, C11H2F11NOS+)
337 (M+, C10H3F8NOS+)
383 (M+, C12H6F9NOS+)
315 (M+, C11H7F6NOS+)
519 (M+, C11H2F17NOS+)
73
75
35
45
46
65
58
50–52b
39–40b
81–82b (50–52/0.7)
(67–68/0.5)
(63–64/0.5)i
(75–78/25)i
1627f (C5N), 1694 (C5C)
1559,f 1649, 1704 (br.)
633 [(MÀF)+, C13H2F21N2OS+)
188 (M+, C4H3F3OS2
256 (M+, C5H2F6OS2
)
)
+
+
–
a
Structure established by single crystal X-ray diffraction.
From hexane.
b
c
Yield of crude product; purity 95%, contaminated by 5% of 3. Freshly prepared 5 was free of 6, but it underwent partial trimerization during distillation; compound 6
(purity >95%, NMR) was found in distillation pot.
d
Sample of crude 5 crystallized on storage in refrigerator at À25 8C.
e
Neat, KCl plate.
f
In CH2Cl2.
g
Yield of crude product, purity 97%, contaminated by 3% of 12.
h
Yield of crude product, purity >98%.
i
From CCl4.
j
Purity of distilled material was 98%.
mixture became homogeneous. The reaction mixture was diluted
with 300 mL of saturated aqueous solution of NH4Cl, extracted
with CH2Cl2 (3Â 50 mL) and the combined organic solution was
dried over MgSO4 (ꢀ20 min). Solvent was removed under reduced
pressure to leave 12.6 g of crude 5, contaminated by 5% of 3 (NMR).
Sample of 5 crystallized on storage in refrigerator. The distillation
of crude product gave a fraction of 5 (b.p. 46–47 8C/2 mm Hg,
purity >98%) and high boiling point residue in pot of distillation
column (ꢀ50% of sample by weight), which was found to be almost
pure 6 (purity 98% NMR and GC/MS). Data for compound 5 are
given in Tables 1 and 2.
dried over MgSO4, and solvent was removed under reduced pressure
to leave 18 g of black, oily material. It was dissolved in 300 mL of
hexane and put through short silica gel column. After solvent
removal 9.5 g (30%) of tan crystalline solid was isolated and
identified as 5b (NMR, IR, GC/MS, purity 98%). Crystals for X-ray
diffraction experiment were obtained by crystallization of small
sample from hexane at À25 8C. Data for compound 5b are given in
Tables 1 and 2.
4.7. Preparation of compound 6
Sample of crude 5 (liquid, 12 g, 0.05 mol) stored at ambient
temperature crystallized after 6 days. Crystalline material was
identified as 6, 99% purity (NMR, GC/MS). Yield of 6 was
quantitative. A small sample for melting point measurement
was obtained by crystallization from hexane. Data for compound 6
are given in Tables 1 and 2.
4.5. Preparation of compound 5a
The reaction was carried out on same scale as in Section 4.4, but
the reaction mixture was left at ambient temperature for 4 days.
The precipitated dark organic layer (ꢀ3.5 g) was separated, left
under a flow of nitrogen overnight and crystallized. Crystalline
material (2.3 g, 10% yield) was identified as 5a based on combined
data of NMR, IR spectroscopy, MS spectrometry and single crystal
X-ray diffraction data. A small sample of 5a for melting point
measurement was obtained by crystallization from hexane (white
needles). Data for compound 5a are given in Tables 1 and 2.
4.8. Preparation of compounds 7 and 7a
(a) A mixture of 3.9 g (0.03 mol) (CH3)3SiNCS, and 6 g (0.033 mol)
of 2 was kept at ambient temperature for 5d. The thick, clear
reaction mixture was distilled under reduced pressure to give
7.7 g (82%) of 7, b.p. 94–95 8C /15 mm Hg. Data for compound 7
are given in Tables 1 and 2.
4.6. Preparation of compound 5b
(b) A mixture of 2.6 g (0.02 mol) (CH3)3SiNCS, 3.6 g (0.02 mol) 2, 1
drop of triethylamine and 20 mL of dry THF was agitated at
ambient temperature for 24 h. The solvent was removed under
vacuum to leave 6.4 g of clear slightly yellow oil, was identified
as compound 7 (NMR, IR, GC/MS), containing 5% of THF and 5%
of two unknown products.
A mixture of KSCN (10 g, 0.1 mol), 2 (36 g, 0.2 mol) and 200 mL of
water was agitated at ambient temperature for 4d. Precipitated
organic layer (7.5 g, mostly 5a) was removed and the remaining
reaction mixture was diluted by saturated aqueous solution of
NH4Cl, extracted by ether (3Â 75 mL). Combined ether extract was

V.A. Petrov, W. Marshall / Journal of Fluorine Chemistry 132 (2011) 41–51
49
Table 2
1H, 13C and 19F NMR spectra of new materials.
Compound no.
1H NMR (
d
, ppm, J, Hz)a
19F NMR (
d
, ppm, J, Hz)a
13C NMR ( , ppm, J, Hz)a,b
d
3c
3ac
3.24 (2H, s), 4.26 (1H, s)
À76.83 (s)
3.82 (2H, AB quartet, 16), 7.75 (1H, br.s)
À77.12 (3F, q, 10.1), À77.93
(3F, q, 10.1)
52.37, 75.80 (sept, 29.7), 122.46
(q, 288.0), 122.87 (q, 288.0)
4c
5
0.98 (12H, t, 7.4), 1.44 (8H, m, 7.4), 1.82
(8H, m, 7.7),
À77.44 (s)
3.43 (8H, m), 3.66 (2H, s)
3.78 (2H, s), 6.58 (1H, br.s)
À77.50 (s)
31.60, 83.98 (sept, 29.9), 121.13
(q, 286), 165.29
5a
5b
3.50 (2H, s), 4.45 (2H, s), 4.60 (1H, br.s)
3.50 (4H, s), 4.85 (2H, s), 5.90 (1H, br.s)
À77.20 (3F, s), À78.10 (3F, s)
À76.30 (6F, s), À77.30 (3F, s)
30.84, 42.70, 75.55 (sept, 29.5), 84.64
(sept, 33), 121.00 (q, 284), 122.41
(q, 286), 167.72
6
3.78 (2H, s), 5.30 (1H, br.s)
0.14 (9H, s), 3.35 (2H, sept, 0.6)
3.50 (s)c, 6.42 (br.s)
À77.04 (s)
À74.86 (s)
À76.98 (s)c
30.84, 76.84 (sept, 29.0), 124.36
(q, 284), 179.93
7
0.04, 34.90, 76.26 (sept, 30.5),
110.16, 121.33 (q, 292.0)
31.90, 77.19 (sept, 27.6), 123.66
(q, 292.0), 167.51c
9d
10
11
3.51 (s)
3.49 (s)
À76.20 (s)
À76.49 (6F, s), À80.86 (3F, tt, 10.0, 2.0),
À119.57 (2F, m), À121.37 (2F, m), À122.73
(2F, m), À126.12 (2F, m)
À76.40 (s)
17
3.51 (2H, s), 3.54 (2H, t, 8.1), 4.18
(2H, t, 8.1)
33.87 (sept, 1.3), 37.36,
62.15, 77.09 (sept, 27.8), 129.12
(q, 288.0), 172.68
18
19
3.78 (2H, s), 7.38 (2H, m), 7.52 (1H, m),
7.62 (1H, m)
À76.81
À76.32
3.76 (2H, s), 7.39 (1H, t, 7.5), 7.48
(1H, t, 7.5),
7.77 (1H, d, 7.5), 7.86
(1H, d, 7.5), 9.93 (1H, br.s)
20
3.58 (2H, s), 7.18 (1H, ddd, 7.4, 5.6, 1.0), 7.41
(1H, dt, 8.2, 1.3), 7.63 (1H, td, 7.8, 1.8), 8.37
(1H, dm, 5.3), 9.82 (1H, s)
À76.32 (s)
À76.80c
21c
3.94 (2H, sept, 0.6), 7.38 (1H, t, 4.9), 8.28
(1H, br.s), 8.72 (2H, d, 4.9)c
3.19 (2H, s), 6.98 (2H, t, 7.5), 7.17 (1H, t, 7.5),
7.35 (2H, t, 7.4)
22ae
Major: À76.78 (s)
Minor: À77.17 (s)
31.04, 82.68 (sept, 32.9), 120.66 (q, 292),
120.62, 121.54, 125.65, 129.45,
147.45, 159.32
23af
3.89 (s), 3.92 (s)
À76.88 (s), À77.11 (s)
23bg
Major: 3.68, 3.74 (2H, m), 5.11 (1H, m)
Minor: 3.68, 3.74 (2H, m), 5.04 (1H, m)
Major: À77.51 (3F, d, 5.4), À151.01
(2F, d), À162.51 (2F, t),
À163.81 (1F, t)
Minor: À77.86 (3F, d, 5.4), À150.21
(2F, d), À160.91 (2F, t),
À162.23 (1F, t)
24ah
24bi
3.8 (2H, s), 7.15 (1H, m), 7.23 (1H, m), 7.43
(1H, m), 7.47 (1H, m)
Major: À62.88 (3F, s), À76.88 (6F, s)
Minor: À63.06 (3F, s), À77.23 (6F, s)
Major: À62.77 (3F, s), À77.38 (3F, d, 5.4)
Minor: À62.55 (3F, dd, 6.1, 1.8), À79.26
(3F, d, 6.1)
Major: 3.62 (2H, m), 4.98 (1H, m), 7.14
(1H, d), 7.22 (1H, s), 7.41
(1H, d), 7.46 (1H, m)
Minor: 3.22 (2H, m), 5.64 (2H(m)
4.0 (s)
25a
26a
À58.62 (3F, m), À63.00 (3F, m), À80.51
(6F, s), À84.12 (3F, m),
À114.72 (2F, m)
3.96 (s)
À77.58 (6F, s), À80.76 (3F, t, 7.6), À81.39
(3F, t, 9.5), À94.48 (2F, m),
À116.65 (2F, q, 8.9), À125.97 (2F, m),
À126.25 (2F, m), À126.35 (2F, m)
À77.57 (d, 6.1)
27
28
3.78 (dd), 3.87 (dd), (2H, AB quartet), 5.36
33.45 (sept, 1.7), 83.30 (sept, 33.8),
122.00 (q, 280), 208.44
(1H, m)
3.94 (s)
À77.10 (s)
34.33 (sept, 1.4), 89.99 (sept, 33.2),
120.87 (q, 287), 204.21
a
In CDCl3 solvent, unless stated otherwise.
13C {H} NMR spectrum.
b
c
d
e
f
In actone-d6.
In acetonitrile-d3.
Mixture of two isomers, ratio 90:10.
Mixture of two isomers, ratio 50:50.
Mixture of two isomers, ratio 1.5:1.
Mixture of two isomers, ratio 4:1.
Mixture of two isomers, ratio 5:1.
g
h
i

50
V.A. Petrov, W. Marshall / Journal of Fluorine Chemistry 132 (2011) 41–51
A sample of crude 7 was left at ambient temperature and after
0.035 mol) was added slowly at 25–30 8C. The orange-brown
reaction mixture was agitated for 2 h at 25 8C and the epoxide 2
(6.3 g, 0.035 mol) was added drop wise at 25–30 8C (slightly
exothermic). The reaction mixture was agitated for 16 h at ambient
temperature, diluted with water (200 mL), extracted with hexane
(3Â 50 mL). Combined organic layer was washed with water, dried
over MgSO4 and solvent was removed under vacuum. The residue
was distilled under reduce pressure to give compound 25a or 26a
(purity 97–98%). Data for compounds 25a, 26a are given in Tables 1
and 2.
ꢀ6 months the formation of crystalline solid (needles) was
observed in the sample. Crystals were filtered and identified as
compound 7a by single crystal X-ray diffraction.
4.9. Preparation of compounds 9, 10 and 11
Compound 2 (12 g, 0.11 mol) was slowly added to an agitated
solution of thiourea (8, 7.6 g, 0.1 mol) in 100 mL of dry THF, at a
rate that maintained internal temperature at 25–28 8C. The
reaction mixture was agitated at 25 8C for 2 h and the solvent
was removed under vacuum to leave 26 g of white solid material,
identified as 9.
4.13. Preparation of compounds 27 and 28 (typical procedure)
To a solution of 5 g of t-BuOK in 30 mL of dry DMF was added a
solution of 9 (5 g in 20 mL of DMF) at 5–10 8C. The reaction mixture
was warmed to 25 8C (ꢀ1 h) and diluted with 300 mL of saturated
aqueous solution of NH4Cl. Precipitated organic layer was
separated, washed with water (3Â 30 mL), dried over MgSO4
and identified as thiol 9 (NMR spectroscopy).
The reaction of 9 with t-BuOK was run as described above (same
scale), but after the addition of the solution of t-BuOK in DMF, the
reaction mixture was agitated at 25 8C for 1 h, and then 13 g of
C3F13I was added. The agitation was continued for another 6 h at
60 8C. The reaction mixture was diluted with 300 mL of 10%
hydrochloric acid, extracted by hexane (3Â 50 mL), combined
extract was washed with water (2Â 100 mL), dried over MgSO4 and
the solvent was removed under vacuum. The residue (10 g) was
distilled under reduced pressure to give 6 g of compound 11, b.p.
95–97 8C/0.5 mm Hg. Data for compound 9, 10 and 11 are given in
Tables 1 and 2.
The epoxide 1 or 2 or (0.05–0.1 mol) was added slowly at 25–
30 8C to agitated mixture of CS2 (4.0–7.5 mL, 0.05–0.1 mol) and
0.1–0.3 g of Bu4N+FÀÁH2O catalyst and dry THF (50–100 mL). The
reaction mixture was agitated at 25 8C for 4–16 h and the solvent
was removed under reduced pressure. The residue was distilled
under vacuum to give compound 27 or 28 (purity >98%). Data for
both compounds are given in Tables 1 and 2.
Acknowledgements
PVA thanks Dr. A. Sievert (DuPont FLPR) for sample of epoxide 2,
reviewers for helpful suggestions and Timothy Bentz for technical
assistance.
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4.11. Preparation of compounds 22a, 23a, b, 24a, b (typical
procedure)
To a mixture of 0.2–0.5 g of catalysts (Bu4N+FÀÁH2O was used for
the preparation of 22a, 23b, 24b and CsF for synthesis of 23a and
24a) and arylisothiocyanate (0.02 mol) in 50 mL THF (for reaction
of 22, 23, 24 with the epoxides 1, 2) or 50 mL CH3CN (preparation
of 23a) the epoxide 2 or 1 (0.025 mol) was added slowly. The
reactions involving more reactive 2 were exothermic, the epoxide
addition was carried out at 25–30 8C and they typically were
completed within 2–24 h. The reactions involving less reactive 1
require 4–7 days at 25 8C for completion (monitored by GC). After
the conversion of epoxide reached >90%, the reaction mixture was
diluted with water, extracted with hexane (3Â 50 mL), hexane
layer was dried over MgSO4 and the solvent was removed under
reduced pressure to leave crude crystalline material or oil. Pure
samples were obtained by crystallization from hexane. Data for
compounds 22a, 23a, b, 24a, b are given in Tables 1 and 2.
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