Reaction of polyfluoro-3-chloro(bromo)-1-butenes with sodium hypohalites and properties of epoxides derived therefrom

Article abstract of DOI:10.1023/B:RUJO.0000003178.33413.99

Epoxidation of 3-chloro(bromo)heptafluoro-1-butenes and 3,4-dichlorohexafluoro-1-butene with aqueous solutions of sodium hypohalites is accompanied by cleavage of the carbon skeleton at the double bond and formation of polyfluorocarboxylic acid sodium sal

Full text of DOI:10.1023/B:RUJO.0000003178.33413.99

Russian Journal of Organic Chemistry, Vol. 39, No. 7, 2003, pp. 919 923. Translated from Zhurnal Organicheskoi Khimii, Vol. 39, No. 7, 2003,
pp. 980 984.
Original Russian Text Copyright
2003 by Zapevalov, Filyakova, Kodess, Saloutin.
Reaction of Polyfluoro-3-chloro(bromo)-1-butenes
with Sodium Hypohalites and Properties
of Epoxides Derived Therefrom
A. Ya. Zapevalov, T. I. Filyakova, M. I. Kodess, and V. I. Saloutin
Institute of Organic Synthesis, Ural Division, Russian Academy of Sciences,
ul. S. Kovalevskoi 20, Yekaterinburg, 620219 Russia
e-mail: saloutin@ios.uran.ru
Received February 13, 2002
Abstract Epoxidation of 3-chloro(bromo)heptafluoro-1-butenes and 3,4-dichlorohexafluoro-1-butene with
aqueous solutions of sodium hypohalites is accompanied by cleavage of the carbon skeleton at the double
bond and formation of polyfluorocarboxylic acid sodium salts as by-products. 3-Chloro(bromo)-1,2-epoxy-
heptafluoro- and 3,4-dichloro-1,2-epoxyhexafluorobutanes were synthesized and subjected to isomerization
into carbonyl compounds by the action of cesium fluoride or antimony pentafluoride.
We previously demonstrated a wide synthetic
potential of the hypohalite procedure for epoxidation
of polyfluoroalkenes, which makes it possible to
obtain various polyfluorinated epoxy derivatives
[1 5]. We found that the structure of the initial alkene
largely determines the mechanism of its reaction with
hypohalite ions. In the epoxidation of internal and
cyclic perfluoroalkenes, the yields of the correspond-
ing epoxy derivatives were nearly quantitative [1 4],
whereas in the reactions with terminal perfluoro-
alkenes the yields were somewhat lower because of
side processes [1, 2, 5]. The selectivity of epoxidation
is also reduced when the substrate contains chlorine
or bromine atoms in the - or -position with respect
to the double bond [6, 7].
purpose, we examined reactions of sodium hypo-
halites with polyfluoro-1-butenes having a chlorine or
bromine atom in position 3: 3-chloroheptafluoro-1-
butene (I), 3-bromoheptafluoro-1-butene (II), and
3,4-dichlorohexafluoro-1-butene (III).
The synthesis and some properties of alkenes I and
II were described by us previously [8]. Compound
III was synthesized by pyrolysis of sodium 4,5-di-
chloropentanoate. Alkenes I III readily react with
sodium hypohalites in a mixture of water with
an aprotic solvent; however, the presence of chlorine
or bromine atom gives rise to alternative paths for
stabilization of intermediate carbanions. Despite the
reactions were not strictly selective, we succeeded
in isolating epoxy derivatives of all the above alkenes
(Scheme 1). The by-products were mainly sodium
salts of polyfluorocarboxylic acids, which are soluble
in water (polyfluorinated peroxides are insoluble
in water).
The goal of the present study was to get a deeper
insight into the mechanism of hypohalite oxidation
of fluoroalkenes, prepare the corresponding epoxides,
and determine their structure and properties. For this
Scheme 1.
I, IV, VII, Hlg = Cl; II, V, VIII, Hlg = Br.
1070-4280/03/3907-0919$25.00 2003 MAIK Nauka/Interperiodica

920
ZAPEVALOV et al.
Scheme 2.
The reaction is likely to follow Scheme 2. Carb-
the reaction with dichloroalkene III. Presumably,
oxygen-containing anions undergo further transforma-
tion, as follows from evolution of a small amount
of CO and CO2. This is consistent with the results
obtained in the epoxidation of 1,4-dichlorohexa-
fluoro-2-butene [6], where we failed to detect by-
products as well. However, following the above
procedure, from alkene II we obtained 1-bromohepta-
fluoro-2-butene (X) as the major product (Scheme 3).
We previously reported [8] that alkene II extremely
readily undergoes isomerization into compound X
by the action of both nucleophilic and electrophilic
reagents [8]. Addition of a few drops of a solution
of NaOCl to a solution of polyfluorobutene II in
acetonitrile (i.e., the reaction occurs in fact in aprotic
medium) leads to elimination of bromide ion (path-
way a1 in Scheme 2) which promotes isomerization
of II into X. The latter process is accompanied by
elimination of the allylic bromine atom, giving rise
to a specific chain reaction (Scheme 3).
anionic intermediate A can be stabilized according to
pathways a1 and a2 with equal propabilities. The
yields of epoxy derivatives IV and V are 52 and 40%,
respectively; sodium trifluoroacetate is the major com-
ponent of the salt products. However, the formation
of a small amount of compounds VII and VIII (7 9%
of the overall amount of the salt products) indicates
that stabilization pathway a3 also exists.
The product composition and the yield of epoxy
derivatives IV, V, and IX depend on the initial alkene
structure, reaction temperature, and the way of mixing
of the reactants. The maximal yields of 1,2-epoxy-
butanes IV and IX were obtained when an aqueous
solution of sodium hypochlorite was added at 5 to
10 C to a solution of polyfluoroalkene I or III in
acetonitrile. The yield decreases on raising the tem-
perature, while the fraction of alkaline hydrolysis
products increases. No by-products were isolated in
Scheme 3.
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 39 No. 7 2003

REACTION OF POLYFLUORO-3-CHLORO(BROMO)-1-BUTENES
Table 1. 19F NMR spectra of compounds III V, VII IX, XIII, and XVIa
Comp.
921
Formula
Chemical shifts, F, ppm
Coupling constants JF, F, Hz
no.
III
108.24 d.d.d.d.d (1-F);
89.64 d.d.d.m (2-F);
166.94 d.d.d.d.d (3-F);
128.34 d.d.d.d.d (4-F);
66.32 d.d.d.d (5-FA);
65.23 d.d.d.d (5-FB)
J1, 2 = 58.2, J1, 3 = 126.3,
J1, 4 = 48.8, J1, 5A J1, 5B = 4.0,
J2, 3 = 42.8, J2, 4 = 2.8, J3, 4 = 22.8,
J3, 5A = 9.0, J3, 5B = 8.2,
J4, 5A = 12.1, J4, 5B = 13.0,
J5A, 5B = 177.1
=
IV
Isomer 1 (60%):
107.86 d.d.m (1-F);
J1, 2 = 41.0, J1, 3 = J2, 3 = 17.0,
J1, 4 = 24.5, J3, 5 = J4, 5 = 8.3
107.26 d.d (2-F); 143.27 m (3-F);
133.87 m (4-F); 79.11 d.d (5-F)
Isomer 2 (40%):
108.57 d.d.m (1-F);
110.60 d.d.d (2-F); 147.68 m (3-F);
135.15 m (4-F); 77.90 d.d (5-F)
J1, 2 = 42.0, J1, 3 = 18.0,
J1, 4 = 20.5, J2, 3 = 18.0,
J2, 4 = 2.0, J3, 5 = 7.3, J4, 5 = 9.8
V
Isomer 1 (70%):
J1, 2 = 39.0, J1, 3 = 17.1,
107.86 d.d.d (1-F); 106.67 d.d.d (2-F); J1, 4 = 25.6, J2, 3 = 17.1;
140.68 m (3-F);
J2, 4 = 3.7; J3, 5 = J4, 5 = 9.8
137.61 m (4-F); 77.82 d.d (5-F)
Isomer 2 (30%):
109.04 d.d.m (1-F);
111.49 d.d.d (2-F); 147.54 m (3-F);
138.51 m (4-F); 76.34 d.d (5)
J1, 2 = 42.7, J1, 3 = 18.3,
J1, 4 = 20.8, J2, 3 = 18.3,
J2, 4 = 2.4, J3, 5 = J4, 5 = 9.8
VII
VIII
IX
78.54 d (1-F); 123.95 q (2-F)
J1, 2 = 6.1
J1, 2 = 8.5
76.83 d (1-F); 124.54 q (2-F)
Isomer 1 (75%):
107.88 d.d.d.m (1-F);
108.70 d.d.m (2-F); 143.56 m (3-F);
127.30 m (4-F); 61.81 d.d (5-FA);
66.04 d.m (5-FB)
J1, 2 = 40.0, J1, 3 = 17.0,
J1, 4 = 26.0, J1, 5A = 2.0,
J1, 5B = 1.0, J2, 3 = 16.0,
J3, 4 = 18.0, J3, 5A = 15.0,
J3, 5B = 13.0, J4, 5A
=
8.5,
J4, 5B = 11.0, J5A, 5B = 176.0
Isomer 2 (25%):
109.64 d.d.d.m (1-F);
112.69 d.d.d.m (2-F); 148.90 m (3-F);
127.92 m (4-F);
J1, 2 = 43.0, J1, 3 = 18.0,
J1, 4 = 21.0, J2, 3 = 19.0,
J2, 4 = 2.0, J3, 4 = 6.5,
J3, 5 = 14.5, J4, 5 = 9.5
63.67 d.d.m (5-F, AB center)
XIIIb
XVI
13.6 m (1-F, AB center);
57.3 m (2-F); 33.43 m (3-FA);
34.67 m (3-FB);
J3A, 3B = 175
97.3 m (4-F)
73.04 d.t (1-F); 134.34 m (2-F);
63.84 d.d.q (3-FA);
65.34 d.d.q (3-FB)
J1, 2 = 5.8, J2, 3A = 8.6,
J2, 3B = 10.0, J1, 3A = J1, 3B = 1.9,
J3A, 3B = 176.9
a
The 19F NMR spectra of compounds XIV and XV coincided with those reported in [6].
Relative to CF3COOH (external reference).
b
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 39 No. 7 2003

922
ZAPEVALOV et al.
Table 2. Yields, boiling points, and IR spectra of com-
pounds III V, IX, and XI XVI
Scheme 5.
Compound
no.
Yield,
%
IR spectrum,
bp,
C
1
, cm
III
IV
V
IX
73
52
44
57
88
90
92
86
75
84
66 67
30 31
46 47
65 66
36 37
57 58
70 71
31 32
45 46
64 65
1770 (C C)
1540 (oxirane)
1535 (oxirane)
1540 (oxirane)
1880 (COF)
1880 (COF)
1865 (COF)
1785 (C O)
1775 (C O)
1780 (C O)
XIV, Hlg = Cl; XV, Hlg = Br.
XI
XII
XIII
XIV
XV
XVI
EXPERIMENTAL
The 19F NMR spectra were recorded on Tesla BS-
567A (94.1 MHz) and Tesla BS-587A spectrometers
(75.3 MHz) using acetone-d6 and methanol-d4 as sol-
vents and C6F6 as internal reference; also, a Perkin
Elmer R-32 instrument (84.6 MHz) was used with
CF3CO2H as external reference. The chemical shifts
are given in ppm relative to CFCl3 (positive values
correspond to increasing field strength). The 19F NMR
data are collected in Table 1. The IR spectra were
measured on a Specord 75IR spectrometer from
samples prepared as thin films or solutions in CCl4.
GLC analysis was performed on an LKhM-72 chro-
matograph equipped with a thermal conductivity
detector and steel columns (6500 4 mm) packed with
15% of SKTFT-100 or FS-1265 on Chromosorb W;
carrier gas helium.
No isomerization products were obtained from
alkenes I and III under analogous conditions. The
observed difference in the behaviors of bromine-con-
taining polyfluorobutene (II) and alkenes I and III
may be explained by more facile elimination of
bromine as bromide ion and higher nucleophilicity of
bromide ion as compared to chloride ion [9].
3-Bromo-1,2-epoxyheptafluorobutane (V) was
obtained in 41% yield by addition of alkene II in
a dropwise fashion to a solution of NaOCl containing
acetonitrile at 0 to 10 C. According to the 19F NMR
data, compounds IV, V, and IX are formed as mix-
tures of two diastereoisomers due to the presence in
their molecules of two chiral centers (Table 1).
Epoxypolyfluoroalkanes IV, V, and IX, as well as
their perfluorinated analogs, are capable of under-
going rearrangement into carbonyl compounds by the
action of Lewis acids and bases. In the presence of
fluoride ion, these compounds give rise to acyl
fluorides XI XIII (Scheme 4). The rearrangement
was performed in acetonitrile under reflux to avoid
formation of oligomeric products. Compounds IV, V,
and IX readily react with SbF5 at room temperature to
afford -chloro(bromo)polyfluoroketones XIV XVI
(Scheme 5).
4,5-Dichloroheptafluoropentanoic acid was synthe-
sized by the procedure described in [10], and alkene
III was prepared by pyrolytic decarboxylation of
sodium 4,5-dichloroheptafluoropentanoate at 250
280 C. The yields, boiling points, and some IR bands
of the compounds prepared are given in Table 2.
Solutions of sodium hypochlorite [1] and sodium
hypobromite [11] were prepared by known methods.
Reaction of alkene I with NaOCl. An aqueous
solution of NaOCl, 50 ml, was added at 5 to 10 C
under vigorous stirring to a solution of 4.8 g
(22.17 mmol) of alkene I in 6 ml of acetonitrile. The
mixture was stirred for 1 h, and the organic layer was
separated, washed with water, dried over MgSO4, and
distilled. Yield of epoxy derivative IV 2.7 g. Found,
%: C 20.34; Cl 15.12; F 56.90. C4ClF7O. Calculated,
%: C 20.65; Cl 15.27; F 57.20. The aqueous phase
was evaporated, and the salt residue was dried and
dissolved in CD3OD. According to the 19F NMR data,
it was a 61:39 mixture of salts VI and VII.
Scheme 4.
Reaction of alkene II with NaOCl. a. The reac-
tion was carried out in a similar way. From 10 g
(38.31 mmol) of alkene II, 8 ml of acetonitrile, and
50 ml of a solution of NaOCl we obtained 8.4 g of
XI, Hlg = Cl; XII, Hlg = Br.
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 39 No. 7 2003

REACTION OF POLYFLUORO-3-CHLORO(BROMO)-1-BUTENES
923
alkene X containing a small amount ( 5%, according
to GLC and 19F NMR) of compound V.
Reaction of compound IV with SbF5. Antimony
pentafluoride, 0.1 ml, was added dropwise to 1.0 g
(4.3 mmol) of compound IV. The mixture was kept
for 0.5 h and was then distilled over concentrated
sulfuric acid to isolate 0.86 g of ketone XIV.
Reaction of compounds V and IX with SbF5.
Following the above procedure, from 1.2 g (4.3 mmol)
of compound V or 1.8 g (7.23 mmol) of IX and
0.1 ml of SbF5 we obtained, respectively, 0.9 g of
ketone XV or 1.5 g of ketone XVI.
b. Alkene II, 6.0 g (23 mmol), was added drop-
wise at 0 to 10 C under vigorous stirring to 50 ml
of an aqueous solution of NaOCl and 6 ml of aceto-
nitrile. The mixture was stirred for 1 h, and the
bottom layer was separated, washed with water, dried
over MgSO4, and distilled. Yield of compound V
2.8 g. Found, %: C 17.25; Br 29.30; F 41.07.
C4BrF7O. Calculated, %: C 17.45; Br 29.09; F 41.45.
According to the 19F NMR data, the aqueous phase
contained salts VI and VIII at a ratio of 91:9.
REFERENCES
Reaction of alkene II with NaOBr. Alkene II,
4.0 g (15.33 mmol), was added dropwise at 5 C
under vigorous stirring to a mixture of 20 ml of
an aqueous solution of NaOBr and 2 ml of aceto-
nitrile. The mixture was stirred for 1 h. The organic
phase was separated, washed with water, dried over
MgSO4, and distilled. We isolated 2.8 g of a mixture
of compounds V and X at a ratio of 70:30 (GLC,
19F NMR). From the aqueous phase, a mixture of salts
VI and VIII (93:7; 19F NMR) was isolated.
Reaction of alkene III with NaOCl. An aqueous
solution of NaOCl, 100 ml, was added dropwise at
0 to 10 C under vigorous stirring to a solution of
20.0 g (85.8 mmol) of alkene III in 10 ml of aceto-
nitrile. The mixture was stirred for 1 h and was
subjected to appropriate treatment to isolate 12.2 g
of compound IX. Found, %: C 19.56; Cl 28.05;
F 45.33. C4Cl2F6O. Calculated, %: C 19.28; Cl 28.51;
F 45.78. No organofluorine compounds were detected
in the aqueous phase by 19F NMR spectroscopy.
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Reaction of 3-chloro-1,2-epoxyheptafluoro-
butane (IV) with CsF. Compound IV, 1.25 g
(5.38 mmol), was added dropwise with stirring to
a mixture of 0.3 g (1.96 mmol) of freshly calcined
CsF and 3 ml of freshly distilled (over P2O5) aceto-
nitrile, heated to the boiling point. The mixture was
stirred for 0.5 h, filtered, and distilled. We isolated
1.1 g of 3-chlorohexafluorobutanoyl fluoride (XI).
Reaction of 3-bromo-1,2-epoxyheptafluoro-
butane (V) and 3,4-dichloro-1,2-epoxyhexafluoro-
butane (IX) with cesium fluoride. Following the
above procedure, from 1.6 g (5.8 mmol) of compound
V or 2.5 g (10.0 mmol) of compound IX and 0.5 g
(3.27 mmol) of CsF in 4 ml of acetonitrile we ob-
tained 1.4 g of fluoride XII or 2.3 g of fluoride XIII.
8. Filyakova, T.I. and Zapevalov, A.Ya., Zh. Org.
Khim., 1991, vol. 27, p. 1824.
9. Mathieu, J. and Panico, R., Mecanismes reactionnels
en chimie organique, Paris: Hermann, 1972. Tran-
slated under the title Kurs teoreticheskikh osnov
organicheskoi khimii, Moscow: Mir, 1975, pp. 152,
156.
10. Plashkin, V.S., Zapevalova, T.B., Zapevalov, A.Ya.,
and Selishchev, B.N., Zh. Org. Khim., 1980, vol. 16,
p. 540.
11. Brauer, G., Handbuch der Praparativen anorgani-
schen Chemie, Stuttgart: Enke, 1981. Translated
under the title Rukovodstvo po preparativnoi neorga-
nicheskoi khimii, Moscow: Inostrannaya Literatura,
1956, p. 165.
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 39 No. 7 2003