Synthesis of perfluoro- and 2-trifluoromethylpentafluoro-dihydrofurans and their epoxy derivatives

Article abstract of DOI:10.1023/B:RUJO.0000003194.13428.68

Perfluorotetrahydrofuran-2-carboxylic acid was converted through a series of transformations into perfluoro-2,3-dihydrofuran and perfluoro-2,5- dihydrofuran; likewise, from (2-perfluorotetrahydrofuryl)difluoroacetic acid 2-trifluoromethylpentafluoro-2,3-dihydrofuran was obtained. Perfluoro-2,3- dihydrofuran and 2-trifluoromethylpentafluoro-2,3-dihydrofuran underwent isomerization into perfluoro-2,5-dihydrofuran and 2-trifluoromethylpentafluoro- 2,5-dihydrofuran by the action of cesium fluoride. Treatment of perfluoro-2,5-dihydrofuran with SbF₅ resulted in ring opening and formation of cis-perfluoro-2-butenoyl fluoride, while 2- trifluoromethylpentafluoro-2,3-dihydrofuran was converted into 2-trifluoromethylpentafluoro-2,5-dihydrofuran under the same conditions. Perfluoro-3,4-epoxytetrahydrofuran and 2-trifluoromethyl-3,4-epoxypenta- fluorotetrahydrofuran containing fused oxirane and tetrahydrofuran rings were synthesized by reactions of perfluoro-2,5-dihydrofuran and 2- trifluoromethylpentafluoro-2,5-dihydrofuran, respectively, with sodium hypochlorite.

Full text of DOI:10.1023/B:RUJO.0000003194.13428.68

Russian Journal of Organic Chemistry, Vol. 39, No. 7, 2003, pp. 1010 1015. Translated from Zhurnal Organicheskoi Khimii, Vol. 39, No. 7, 2003,
pp. 1073 1078.
Original Russian Text Copyright
2003 by Filyakova, Kodess, Zapevalov, Saloutin.
Synthesis of Perfluoro- and 2-Trifluoromethylpentafluoro-
dihydrofurans and Their Epoxy Derivatives
T. I. Filyakova, M. I. Kodess, A. Ya. Zapevalov, 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 Perfluorotetrahydrofuran-2-carboxylic acid was converted through a series of transformations into
perfluoro-2,3-dihydrofuran and perfluoro-2,5-dihydrofuran; likewise, from (2-perfluorotetrahydrofuryl)di-
fluoroacetic acid 2-trifluoromethylpentafluoro-2,3-dihydrofuran was obtained. Perfluoro-2,3-dihydrofuran and
2-trifluoromethylpentafluoro-2,3-dihydrofuran underwent isomerization into perfluoro-2,5-dihydrofuran and
2-trifluoromethylpentafluoro-2,5-dihydrofuran by the action of cesium fluoride. Treatment of perfluoro-2,5-di-
hydrofuran with SbF5 resulted in ring opening and formation of cis-perfluoro-2-butenoyl fluoride, while
2-trifluoromethylpentafluoro-2,3-dihydrofuran was converted into 2-trifluoromethylpentafluoro-2,5-dihydro-
furan under the same conditions. Perfluoro-3,4-epoxytetrahydrofuran and 2-trifluoromethyl-3,4-epoxypenta-
fluorotetrahydrofuran containing fused oxirane and tetrahydrofuran rings were synthesized by reactions of
perfluoro-2,5-dihydrofuran and 2-trifluoromethylpentafluoro-2,5-dihydrofuran, respectively, with sodium
hypochlorite.
Polyfluorinated heterocyclic compounds attract
researchers’ attention from both theoretical and prac-
tical viewpoints. Methods of their synthesis are based
mainly on fluorination of hydrocarbons and chlorinat-
ed heterocycles [1 5]. In the present work we used as
starting compounds perfluorotetrahydrofuran-2-car-
boxylic acid and (perfluorotetrahydro-2-furyl)difluoro-
acetic acid which are formed as by-products in the
electrochemical synthesis of perfluoroadipic acid. The
goal of our study was to obtain perfluorinated di-
hydrofurans and their epoxy derivatives and examine
their properties.
fluoro-2,5-dihydrofuran (Ib) and 2-trifluoromethyl-
pentafluoro-2,3-dihydrofuran (IIIa) (Scheme 1). Com-
pounds Ib and IIIa were synthesized previously by
other methods [1, 4]. It was shown that perfluoro-2,5-
dihydrofuran (Ib) can be used as starting compound
in the synthesis of perfluoro-3-oxaglutaric acid [1].
However, the properties of perfluorinated dihydro-
furans have been studied insufficiently.
We examined nucleophilic and electrophilic iso-
merization of perfluoro derivatives Ia/Ib and IIIa.
Treatment of mixture Ia/Ib with cesium fluoride in
Pyrolysis of potassium salts II and IV in the pres-
ence of potassium carbonate gave, respectively, a 1:9
mixture of perfluoro-2,3-dihydrofuran (Ia) and per-
Scheme 2.
Scheme 1.
Ia, Ib, X = F; IIIa, IIIb, X = CF3.
1070-4280/03/3907-1010$25.00 2003 MAIK Nauka/Interperiodica

SYNTHESIS OF PERFLUORO- AND 2-TRIFLUOROMETHYL-.. .
1011
diethylene glycol dimethyl ether gave compound Ib
which is likely to be thermodynamically more stable.
Likewise, from perfluorinated 2,3-dihydrofuran IIIa
we obtained perfluorinated 2,5-dihydrofuran IIIb
(Scheme 2).
However, electrophilic isomerization of perfluoro-
dihydrofurans by the action of antimony pentafluoride
takes different pathways. Compound IIIa, as in the
reaction with cesium fluoride, isomerizes into 2,5-di-
hydro derivative IIIb. Treatment of compounds Ia
and Ib with SbF5 leads to opening of the dihydrofuran
ring with formation of unsaturated perfluoro-2-bute-
Perfluorocycloalkenes are known to react with
bromine at a very low rate. As a rule, the process
requires prolonged UV irradiation in a quartz tube
[8]. We have found that isomer Ia readily reacts with
bromine. On exposure to light, the process is accom-
panied by heat evolution. The bromination of com-
pound Ib requires UV irradiation and yields 3,4-di-
bromohexafluorotetrahydrofuran (VIb). By treatment
of isomer mixture Ia/Ib with a stoichiometric amount
of bromine we succeeded in obtaining and isolating
2,3-dibromohexafluorotetrahydrofuran (VIa). Accord-
ing to the 19F NMR data, dibromo derivatives VIa
and VIb were formed as a single stereoisomer. Like-
wise, trifluoromethyl-substituted compounds IIIa and
IIIb reacted with bromine to afford the corresponding
dibromides VIIa and VIIb (Scheme 5).
noyl fluoride (V). According to the 19F NMR data, the
product has cis configuration of the double C C
bond. Presumably, the transformation Ia V involves
intermediate formation of isomer Ib (Scheme 3).
Scheme 5.
Scheme 3.
The driving force for the above process is likely
to be rearrangement of carbocation A (which is the
primary product of electrophilic attack on Ib by SbF5)
into more stable difluoromethyl cation B. The latter
gives rise to vinylacylium ion C. The stability of such
cations and their acylating ability were demonstrated
in [6, 7]. Complex C decomposes on distillation of
the reaction mixture with concentrated sulfuric acid,
yielding acyl fluoride V (Scheme 4).
VI, X = F; VII, X = CF3.
The ease of bromination of Ia and IIIa may be
explained by the presence of oxygen atom at the
double bond, i.e., the substrates can be regarded as
perfluorinated cyclic vinyl ethers. Dibromo derivatives
VI and VII are readily debrominated to give the
initial dihydrofurans by the action of zinc in acetic
acid. In such a way we obtained pure isomer Ia.
Scheme 4.
With the goal of synthesizing the corresponding
epoxy derivatives, we examined oxidation of Ib and
Scheme 6.
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 39 No. 7 2003

1012
FILYAKOVA et al.
Scheme 7.
IIIb. These compounds turned out to react with
aqueous sodium hypochlorite in the presence of aceto-
nitrile, affording bicyclic products with fused oxirane
and tetrahydrofuran rings: perfluoro-3,4-epoxytetra-
hydrofuran (VIII) and 2-trifluoromethylpentafluoro-
3,4-epoxytetrahydrofuran (IX) (Scheme 6).
to bromination or chlorination in a quartz tube under
UV irradiation, and the halogenation products were
isolated by fractional distillation. According to the
19F NMR data, epoxytetrahydrofuran IX is formed as
a mixture of diastereoisomers at a ratio of 65:35.
Unlike internal and cyclic perfluoroalkenes whose
epoxidation with sodium hypochlorite occurs almost
quantitatively [9, 10], the reaction of NaOCl with
compounds Ib and IIIb does not come to completion.
The product isolated from the organic phase is a mix-
ture of the initial dihydrofuran and the corresponding
epoxy derivative. This may be explained by reduced
electrophilicity of fluorinated dihydrofuran ring, as
compared to perfluorocycloalkenes, due to the pres-
ence of oxygen atom. Moreover, the reaction with
NaOCl is complicated by side processes leading to
cleavage of the dihydrofuran ring (via alternative
paths of stabilization of the carbanionic intermediate),
so that the temperature conditions should be strictly
met. As by-products, sodium salts of polyfluorooxa-
carboxylic acids are mainly formed; they reside in
the aqueous phase. Scheme 7 shows a probable
mechanism of the process with the reaction of com-
pound Ib with NaOCl as an example.
EXPERIMENTAL
The 19F NMR spectra were recorded on Tesla BS-
567A (94.1 MHz), Tesla BS-587A (75.3 MHz), and
Bruker DRX-400 spectrometers (376 MHz) using
C6F6 as internal reference. The 19F chemical shifts
are given relative to CFCl3 (positive values corre-
spond to increasing field strength). The 1H NMR
spectra were obtained on a Bruker DRX-400 instru-
ment at 400 MHz using TMS as internal reference.
The NMR data of the obtained compounds are given
in table. The IR spectra were measured on a Specord
75IR spectrometer from samples prepared as thin
films or gaseous samples. GLC analysis was per-
formed on an LKhM-72 chromatograph equipped with
a thermal conductivity detector; carrier gas helium;
steel columns, 6500 4 mm, packed with 15% of
SKTFT-100 on Chromosorb W. A solution of sodium
hypochlorite was prepared as described in [11].
The boiling points of epoxy derivatives VIII and
IX and the initial dihydrofurans are very similar;
therefore, compounds VIII and IX were subjected
Perfluoro-2,5-dihydrofuran (Ib). a. Pyrolysis of
potassium perfluorotetrahydrofuran-2-carboxylate
(II). A mixture of 84 g (0.3 mol) of salt II and 48 g
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 39 No. 7 2003

SYNTHESIS OF PERFLUORO- AND 2-TRIFLUOROMETHYL-.. .
1013
1
19F and H NMR spectra of compounds Ia, Ib, IIIa, IIIb, V, VIa, VIb, VIIa, and VIII XI
Compound
Formula
Chemical shifts
and F, ppm
Coupling constants J, Hz
no.
Ia
105.82 d.t (1-F); 202.69 d.t.t (2-F); 112.58 J1, 2 = 20.5, J1, 3 = 11.7,
d.d.t (3-F); 91.38 d.t (4-F)
J2, 3 = 9.1, J2, 4 = 3.1,
J3,4 = 1.7
Ib
77.36 d (1-F, 4-F); 153.44 t (2-F, 3-F)
J1, 2 = J3, 4 = 7.3
IIIa
68.10 d.t (1-F); 167.50 q.t.t (2-F); 117.85 d.q J1, 2 = 13.4, J1, 3 = 2.4,
(3-F); 90.08 d (4-F) J2, 3 = 12.8, J2, 4 = 3.6
IIIb
V
82.0 s (1-F); 127.42 m (2-F); 149.65 m (3-F); J3, 4 J4,5A J4, 5B = 13.2,
150.16 m (4-F); 69.74 m (5-FA); 77.53 m JAB = 141.6
(5-FB)
64.85 d.d.d (1-F); 127.90 d.d.q (2-F); J1, 2
J1, 3
7.8,
136.87 d.d.q (3-F); 25.71 d.d.q (4-F)
J1, 4 = 11.8, J2, 3 = 9.8,
J2, 4 = 23.6, J3, 4 = 27.6
VIa
51.86 d.d.d (1-F); 121.73 d.d.d.d (2-F); J1, 2 = 20.8, J1, 3A = 6.1,
103.56 (3-FA); 126.54 d.d (3-FB); J1, 3B = 12.2, J2, 3B = 14.7,
77.60 m (4-FA); 85.20 d.d (4-FB)
m
J2, 4A = 2.4, J3A, 4A = 14.7,
J3B,4A = 12.2, J3A,3B = 247.8,
J4A, 4B = 130.6
VIb
65.16 (1-FA, 4-FA); 86.70 m (1-FB, 4-FB); J1A, 1B = J4A, 4B = 133.0
121.04 m (2-F, 3-F)
VIIa
Isomer 1 (76%): 72.36 d.d (1-F); 107.49 m J2, 3A = 13.4, J2, 3B = 12.2,
(2-F); 111.84 m (3-FA); 124.89 d.d (3-FB); J3A, 4A = 6.1, J3A, 3B = 238.0,
78.80 m (4-FA); 85.31 d (4-FB)
Isomer 2 (24%): 72.16 m (1-F); 107.49 m J2, 3A
(2-F); 104.43 m (3-FA); 132.08 m (3-FB); J3A, 4A = 6.1, J3A, 3B = 246.6,
77.29 m (4-FA); 84.03 d.d (4-FB) J4A, 4B = 133.0
J4A, 4B = 133.1
J3A, 4B = 13.4,
VIII
IX
80.65 (1-FA, 4-FA); 94.88 (1-FB, 4-FB); 182.81 J1A, 1B = J4A,4B = 141.4
(2-F, 3-F)
Isomer 1 (65%): 81.76 d.d.m (1-F); 143.16 d.m J1, 2 = 1.3, J1, 4 J1, 5B 3.6,
(2-F); 174.72 m (3-F); 179.63 d.m (4-F); J2, 5A = 2.4, J4, 5A = 14.6,
79.74 m (5-FA); 91.02 d.m (5-FB)
J5A, 5B = 139.5
Isomer 2 (35%): 79.48 m (1-F); 130.39 d.d.m J1, 2 = 2.4, J2, 3 = 16.0,
(2-F); 178.17 d.m (3-F); 185.54 d.m (4-F); J2, 5B = 6.3, J4, 5A = 14.2,
78.06 d.m (5-FA); 96.03 d.m (5-FB)
J5A, 5B = 140.8
X
6.61 d.t (1-H); 154.02 d.t.m (2-F); 83.54 d.t.d J1, 2 = 47.2, J1, 3 = 5.0,
(3-FA); 84.44 d.t.d (3-FB); 76.54 d.d.d (4-F) J2, 3A
J2, 3B
J3B, 4
12.0,
11.0,
J3A, 4
J2, 4 = 2.8, J4A, 4B = 148.0
XI
7.04 t (1-H); 84.44 d.d.d (2-F); 79.53 d.t J1, 2 = 69.9, J2, 3A = 4.1,
(3-FA); 81.86 d.t (3-FB); 122.66 d.d.m (4-F)
J2, 3B = 4.5, J2, 4 = 3.4,
J3B, 4 = 9.0, J2A, 2B = 146.0
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 39 No. 7 2003

1014
FILYAKOVA et al.
(0.35 mol) of potassium carbonate was heated at 220
240 C. The pyrolysis products were collected in
receivers cooled with a mixture of isopropyl alcohol
and solid carbon dioxide ( 78 C). Distillation with
concentrated sulfuric acid gave 40 g (75%) of a mix-
ture of compounds Ia and Ib at a ratio of 1:9 (accord-
ing to the GLC and 19F NMR data).
pound IIIa and 2.2 g (0.01 mol) of SbF5. The ampule
was sealed and heated for 2 h at 70 C. It was then
cooled and opened, and the mixture was poured into
concentrated sulfuric acid and distilled to isolate 2.2 g
(0.097 mol, 91%) of compound IIIb.
3,4-Dibromohexafluorotetrahydrofuran (VIb).
A quartz ampule was charged with 10.0 g (0.056 mol)
of compound Ib and 9.6 g (0.06 mol) of bromine.
The ampule was sealed and irradiated with UV light
over a period of 12 h. The ampule was opened, the
mixture was treated with a solution of sodium thio-
sulfate, and the organic phase was separated, dried
over MgSO4, and distilled. Yield 17.4 g (0.052 mol,
92%), bp 99 101 C. Found, %: C 14.39; Br 47.62;
F 34.28. C4Br2F6O. Calculated, %: C 14.20; Br 47.34;
F 33.73.
b. Reaction of compounds Ia and Ib with cesium
fluoride in diethylene glycol dimethyl ether. A flask
equipped with a magnetic stirrer and reflux condenser
( 78 C) was charged with 2 g (0.013 mol) of freshly
calcined CsF and 5 ml of diethylene glycol dimethyl
ether (freshly distilled over lithium aluminum
hydride), and 32 g of mixture Ia/Ib was added drop-
wise under stirring. The resulting mixture was stirred
for 2 h at room temperature, and the products were
condensed in a cooled trap ( 78 C). Distillation with
concentrated sulfuric acid gave 29.2 g (0.164 mol,
91%) of compound Ib, bp 14 15 C. IR spectrum:
2,3-Dibromohexafluorotetrahydrofuran (VIa).
A flask equipped with a magnetic stirred and a reflux
condenser ( 78 C) was charged with 80.0 g of isomer
mixture Ia/Ib (1:9), and 7.0 g (0.044 mol) of bromine
was added dropwise under stirring and irradiation with
a filament lamp. The mixture was washed with water,
dried over MgSO4, and subjected to fractional distilla-
tion. Yield 14.2 g (0.042 mol, 93%), bp 98.5 100 C.
Found, %: C 14.56; Br 47.83; F 33.24. C4Br2F6O.
Calculated, %: C 14.20; Br 47.34; F 33.73.
1
1805 cm . The physical constants and spectral
parameters of the product were consistent with those
reported in [1].
2-Trifluoromethylpentafluoro-2,3-dihydrofuran
(IIIa). Pyrolysis of 82.5 g (0.25 mol) of potassium
(perfluoro-2-tetrahydrofuryl)difluoroacetate (IV) in
the presence of 50 g (0.36 mol) of K2CO3 at 220
240 C gave 41.6 g (73%) of compound IIIa, bp 27
1
2,3-Dibromo-2-trifluoromethylpentafluorotetra-
hydrofuran (VIIa). Likewise, from 9.6 g (0.042 mol)
of compound IIIa and 7.0 g (0.044 mol) of bromine
we obtained 15.1 g (0.039 mol, 93%) of dibromide
VIIa, bp 116 120 C. Found, %: C 15.25; Br 40.98;
F 39.18. C5Br2F8O. Calculated, %: C 15.46; Br 41.24;
F 39.18.
28 C. IR spectrum: 1755 cm . The physical con-
stants and spectral parameters of the product were
consistent with those reported in [4].
Reaction of compound IIIa with cesium fluoride
in diethylene glycol dimethyl ether. Likewise, from
26 g (0.114 mol) of compound IIIa, 2 g (0.013 mol)
of CsF, and 5 ml of diethylene glycol dimethyl ether
(reflux, 3 h) we obtained 24 g (0.105 mol, 92%) of
Debromination of compound VIa. A flask
equipped with a magnetic stirrer and a reflux con-
denser was charged with 5 g (0.077 mol) of zinc and
30 ml of acetic acid, and 12 g (0.036 mol) of com-
pound VIa was added dropwise under vigorous stir-
ring. The products were collected in a trap cooled to
78 C. Distillation over concentrated sulfuric acid
gave 4.8 g (0.027 mol, 76%) of compound Ia with
1
compound IIIb, bp 27 C. IR spectrum: 1810 cm .
Reaction of compound Ib with SbF5. A glass
ampule was charged with 1.7 g (96 mmol) of com-
pound Ib and 2.2 g (0.01 mol) of SbF5. The ampule
was sealed and kept for 6 h at room temperature. It
was then cooled and opened, and the mixture was
poured into concentrated sulfuric acid and distilled
to isolate 1.54 g (0.086 mol, 90%) of acyl fluoride V,
1
bp 15 C. IR spectrum: 1745 cm (C C).
1
bp 36 37 C. IR spectrum, , cm : 1700 (C C),
Debromination of compound VIb. Likewise,
from 8.1 g (0.024 mol) of dibromide VIb, 4 g
(0.061 mol) of zinc, and 25 ml of acetic acid we
obtained 3.2 g (0.018 mol, 75%) of compound Ib.
1860 (COF).
Reaction of compound Ia with SbF5. Likewise,
from 2.0 g (0.011 mol) of compound Ia and 2.4 g
(0.011 mol) of SbF5 we obtained 1.76 g (0.01 mol,
88%) of fluoride V.
Reaction of compound IIIa with SbF5. A glass
ampule was charged with 2.4 g (0.0105 mol) of com-
Debromination of compound VIIa. Likewise,
from 14.0 g (0.036 mol) of dibromide VIIa, 5.0 g
(0.077 mol) of zinc, and 30 ml of acetic acid we
obtained 6.4 g (0.028 mol, 78%) of compound IIIa.
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 39 No. 7 2003

SYNTHESIS OF PERFLUORO- AND 2-TRIFLUOROMETHYL-.. .
Reaction of compound Ib with sodium hypo- REFERENCES
1015
chlorite. Compound Ib, 22.0 g (0.124 mol), was
gradually added to a mixture of 100 ml of an aqueous
solution of NaOCl and 10 ml of acetonitrile under
vigorous stirring at 5 10 C. The mixture was stirred
for 2 h, and the products were collected in a trap
cooled to 78 C. We thus obtained 18.2 g of a mix-
ture of epoxy derivative VIII and initial compound
Ib (according to the GLC and IR data). This mixture
was transferred into a quartz ampule, 1.5 ml of
bromine was added, and the ampule was sealed and
irradiated with UV light. The resulting mixture was
treated with a solution of sodium thiosulfate, and the
organic phase was separated, dried over MgSO4, and
subjected to fractional distillation to isolate 14.4 g
(0.074 mol, 60%) of compound VIII, bp 14 15 C,
1. Feast, W.J., Musgrave, W.K.R., and Reeves, N.,
J. Chem. Soc. C, 1971, p. 769.
2. Feast, W.J., Musgrave, W.K.R., and Reeves, N.,
J. Chem. Soc. C, 1970, p. 2429.
3. Burdon, J., Coe, P.L., Smith, J.A., and Tatlow, J.C.,
J. Fluorine Chem., 1991, vol. 51, p. 179.
4. Burdon, J., Coe, P.L., Smith, J.A., and Tatlow, J.C.,
J. Fluorine Chem., 1991, vol. 52, p. 165.
5. Takubo, S. and Sekiya, A., J. Fluorine Chem., 1998,
vol. 87, p. 105.
6. Chepik, S.D., Belen’kii, G.G., Cherstkov, V.F.,
Sterlin, S.R., and German, L.S., Izv. Akad. Nauk
SSSR, Ser. Khim., 1991, p. 513.
7. Snegirev, V.F., Gervits, L.L., and Makarov, K.N.,
1
IR spectrum, , cm : 1550, 1570 (oxirane ring), and
3.8 g (0.011 mol) of dibromide VIb.
Izv. Akad. Nauk SSSR, Ser. Khim., 1983, p. 2765.
8. Haszeldine, R.N. and Osborne, J.E., J. Chem. Soc.,
The aqueous layer was evaporated, and the residue
was dried, dissolved in methanol-d4, and analyzed by
19F NMR spectroscopy. It was a mixture of salts X
and XI at a ratio of 31:69.
1956, p. 61.
9. Zapevalov, A.Ya., Filyakova, T.I., Peschanskii, N.V.,
Kolenko, I.P., and Kodess, M.I., Zh. Org. Khim.,
1986, vol. 22, p. 2088.
Reaction of compound IIIb with sodium hypo-
chlorite. Likewise, from 16.0 g (0.07 mol) of com-
pound IIIb, 80 ml of aqueous NaOCl, and 10 ml of
acetonitrile we obtained 9.3 g (0.038 mol, 54%) of
10. Filyakova, T.I., Peschanskii, N.V., Kodess, M.I.,
Zapevalov, A.Ya., and Kolenko, I.P., Zh. Org. Khim.,
1988, vol. 24, p. 371.
11. Filyakova, T.I., Zapevalov, A.Ya., and Kolenko, I.P.,
USSR Inventor’s Certificate no. 666176, 1979;
Byull. Izobret., 1979, no. 12.
epoxy derivative IX, bp 26 28 C. IR spectrum,
,
1
cm : 1540, 1552 (oxirane ring).
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 39 No. 7 2003