Furan-containing gem-bromonitroethenes: Synthesis and reaction with morpholine

Article abstract of DOI:10.1134/S1070363215060110

The first time the representative of furan-containing gem-bromonitroethenes 5-nitro-2-(2-bromo-2-nitro-ethenyl)furan was synthesized by bromination of 5-nitro-2-(2-nitroethenyl)furan followed by dehydrohalogenation of the dibromide. Morpholine adducts of the synthesized β-substituted gem-bromonitroethene and its analog with a 5-bromo-2-furyl substituent were obtained. The structures of the gem-bromonitroethenes and aza adducts were characterized by spectral methods (IR, UV, ¹H, and ¹³C-{¹H} NMR, including ¹H-¹³C HMQC and HMBC).

Full text of DOI:10.1134/S1070363215060110

ISSN 1070-3632, Russian Journal of General Chemistry, 2015, Vol. 85, No. 6, pp. 1424–1430. © Pleiades Publishing, Ltd., 2015.
Original Russian Text © S.S. Eliseenko, S.V. Makarenko, V.M. Berestovitskaya, 2015, published in Zhurnal Obshchei Khimii, 2015, Vol. 85, No. 6, pp. 957–
9
63.
To the memory of Prof. B.I. Ionin
Furan-Containing gem-Bromonitroethenes:
Synthesis and Reaction with Morpholine
S. S. Eliseenko, S. V. Makarenko, and V. M. Berestovitskaya
Herzen State Pedagogical University, nab. reki Moiki 48, St. Petersburg, 191186 Russia
e-mail: kohrgpu@yandex.ru
Received February 16, 2015
Abstract—The first time the representative of furan-containing gem-bromonitroethenes 5-nitro-2-(2-bromo-2-
nitro-ethenyl)furan was synthesized by bromination of 5-nitro-2-(2-nitroethenyl)furan followed by
dehydrohalogenation of the dibromide. Morpholine adducts of the synthesized β-substituted gem-
bromonitroethene and its analog with a 5-bromo-2-furyl substituent were obtained. The structures of the gem-
1
13
1
bromonitroethenes and aza adducts were characterized by spectral methods (IR, UV, Н, and C–{ H} NMR,
1
13
including Н– С HMQC and HMBC).
Keywords: furan, gem-bromonitroethene, morpholine, nucleophilic addition
DOI: 10.1134/S1070363215060110
The chemistry of gem-halonitroethenes has attracted
furan- and 5-bromofuran-containing gem-bromonitro-
increased interest due to their high reactivity [1].
Especially interesting among compounds of this class
are those containing a furan ring [2–5], because furan
is the key structure of many medicines, including the
antibiotics Furacilin and cefuroxime, antiulcer drug
ranitidine, diuretic furosemide, and anticancer drug
lapatinib [6], and 5-bromo-2-(2-bromo-2-nitroethenyl)-
ethenes in yields of 88 and 39%, respectively [8].
The advantages of the method proposed here is not
only a high yield of the target product, but also that it
has much in common with the known synthesis of its
structurally related analog, specifically 5-bromo-2-(2-
bromo-2-nitroethenyl)furan (V) [8]. The published
procedure of synthesis of compound V [8] was
modified by replacing aqueous potassium hydroxide
1
furan (Furvina) is use in the therapy of dermatological
infections [7].
(
molar ratio 1 : 4.3) at the dehydrohalogenation stage
We report here the first synthesis of 5-nitro-2-(2-
bromo-2-nitroethenyl)furan (III) by bromination of 5-
nitro-2-(2-nitroethenyl)furan (I) followed by dehydro-
halogenation of dibromide II with alcoholic melted
potassium acetate (Scheme 1). This preparatively convenient
procedure features high yields of the intermediate
dibromide II (99%) and final gem-bromonitroethene
III (97%) can be realized in one pot (i.e. without
isolation of dibromide). It should be noted that
compound III was previously obtained by nitration of
by alcoholic melted potassium acetate (molar ratio
1 : 1.6), which allowed the yield of the product to be
increased to 68% (64% [8]).
We performed detailed combined structural analysis
of 5-nitro- and 5-bromo-2-(2-bromo-2-nitroethenyl)-
furans (III, V) by modern spectral methods (IR, UV,
1
13
1
1
13
Н, and C–{ H} NMR, including Н– С HMQC and
HMBC) (Table 1). It should be noted that the obtained
spectral characteristics are agree well with the IR and
UV data presented in part [9] for gem-
bromonitroethene III, as well as more complete IR
1
13
[
9, 10], UV [9], Н [10, 11], and С NMR data [10]
for gem-bromonitroethene V.
1
For convenience in discussion, we used the same heteroring
atom numbering in structurally similar gem-bromonitroethenyl-
furans.
The chemical shift of the vinyl proton signal in the
1
Н NMR spectra of gem-bromonitroethenes III and V
1
424

FURAN-CONTAINING gem-BROMONITROETHENES
1425
Scheme 1.
Br
Br
4
'
'
3'
2'
HA
NO2
Br2
AcOK
5
NO2
1'
O
1
2
NO2
O N
2
O N
2
−HBr
O N
2
O
O
HB
Br
I
II
III
(
1) Br ; (2) AcOK
2
Br
Br
Br2
AcOK
−HBr
NO2
NO2
NO2
Br
Br
O
O
O
Br
IV
V
(
8.55 and 8.49 ppm) suggests Z configuration. As
bromonitrovinyl fragment are observed at 123.00,
123.88 (С ) and 131.10, 124.95 ppm (С ), and the
1
2
known, the downfield position of the signal of the
vinyl proton arranged cis to the nitro group (due to its
anisotropic effect) is one of the important criteria for
the configuration assessment of nitroalkenes. For
example, the olefin proton signal in the spectrum of the
E isomer of 1-bromo-1-nitro-2-phenylethene (the proton
is trans to the nitro group) appears at 7.02 ppm,
whereas the respective signal of the Z isomer (the
proton is cis to the nitro group), at 8.60 ppm [12, 13].
furan ring gives a series of signals at 147.79, 148.49
2
'
3'
4'
(С ), 119.72, 122.08 (С ), 112.55, 115.64 (С ), and
5
'
153.24, 129.48 ppm (С ) (Table 1); the signals were
1
13
assigned on the basis of Н– С HMQC and HMBC
experiments (Fig. 1). Specifically, the HMBC spec-
trum of compound III contains cross peaks between
the downfield vinyl proton signal (δ = 8.55 ppm) and
H
3
'
3
the signals of the furan carbons С (δ = 119.72, J)
and С (δ = 147.79, J), and the carbon atom of the bromo-
nitrovinyl substituent С (δ = 131.10, J), whereas the
doublet signals of the furan hydrogens С Н (δ = 7.45)
C
2'
2
C
1
3
1
2
2
In the С–{ H} NMR spectra of gem-bromo-
nitroethenes III and V, the carbon signals of the
C
4
'
H
Table 1. Yields, melting points, and spectral characteristics of 5-nitro- and 5-bromo-2-(2-bromo-2-nitroethenyl)furans III
and V
Br
4
'
'
3'
2'
5
1
'
2
NO2
X
O
1
UV spectrum
EtOH)
–1
δ, ppm (J, Hz)
ν, cm
(
NO
(Fur-NO2)
2
1
13
1
Yield,
%
mp,
°С
Н
С–{ H}
X
C=C
Fur)
λmax
nm
,
(
4
'
3'
1
5'
2'
4'
3'
1
2
C H C H С H C (C ) C (C ) C (C )
ν
as
ν
s
III NO
2
97
68
89–90 7.45 d 7.53 d 8.55 s 153.24 112.55 123.00 1620 1534 1311
250
5600
20200
(147.79) (119.72) (131.10) (1550) (1352) 360
3
[
J 4.0]
90–91 6.60 d 7.37 d 8.49 s 129.48 115.64 123.88 1611 1533 1305
148.49) (122.08) (124.95) 1623
1460)
V
Br
243
371
6400
19500
(
(
3
[
J 3.7]
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 85 No. 6 2015

1
426
ELISEENKO et al.
C
δ , ppm
1
2' 2
=
С H/C ( J)
δ, ppm
1
13
Fig. 1. H– C HMBC spectrum of gem-bromonitroethene III.
3
'
3
2
and С Н (δ = 7.53) give cross peaks ( J and J) with
Note that according to the X-ray diffraction data in
[14], 5-bromofuran-containing gem-bromonitroethene
V in crystal exists as an s-trans isomer.
H
2
'
the signals of the furan carbons С (δ = 147.79) and
C
5
'
4'
3'
С (δ = 153.24), as well as, separately, С Н/С (δ =
C
C
2
3'
4'
2
1
19.72, J) and С Н/С (δ = 112.55, J).
C
Bromonitroethenes III and V were reacted with
morpholine in ethanol for 1 h at –10 to –5°C to obtain
furan-containing 4-(2-bromo-2-nitroethyl)morpholines
VI and VII (aza-Michael adducts) in yields of up to
The IR spectra of bromonitroethenes III and V in
CHCl differ from each other (Table 1). Thus, the
3
spectrum of 5-nitrofuran-containing compound III
contains strong bands of the conjugated nitro group of
the bromonitrovinyl fragment (ν = 1534, νs
311 cm , Δν = 223 cm ) and of the furan ring
νas = 1550, ν = 1352 cm , Δν = 198 cm ), аs well as
a weak С=С band at 1620 cm . The spectrum of 5-bromo-
furan-containing bromonitroethene V displays absorp-
tion bands of the С=С bond (1611 and 1623 cm ),
furan ring (1460 cm ), and covalent conjugated nitro
8
8%; the products are crystalline substances stable on
storage at a low temperature. Previously Gruntfest
et al. [9] reported the preparation of compound VII in
more rigid conditions (heating in an alcohol solution at
40–80°С) but provided no details of the synthesis and
physicochemical characteristics of the product
(Scheme 3).
=
as
–1
–1
1
(
–
1
–1
s
–1
–
1
–
1
–1
–1
–1
group (ν = 1533 cm , ν = 1305 cm , Δν = 228 cm ).
as
s
It would be noted that the IR spectra of compounds III
and V in a chloroform solution agree with the IR
spectra measured for suspensions of these compounds
in mineral oil. The electronic absorption spectra of
furan-containing bromonitroethenes III and V show
strong long-wave bands at λmax = 360–371 nm, ε =
Scheme 2.
Br
Br
O
O +
Br
−
O
1
9500–20200 (Table 1), whose position does
Br
N
+
contradict the data in [9] and may suggest considerable
polarization of the molecules (Scheme 2).
NO2
−
O
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 85 No. 6 2015

FURAN-CONTAINING gem-BROMONITROETHENES
1427
Scheme 3.
Br
4
'
3'
HA
2'
*
5
'
Br
HN
O
NO2
1
O
'
*
X
HB
NO2
N
X
O
EtOH
4
3
2
5
6
1
O
III, V
VI, VII
X = NO (III, VI); Br (V, VII).
2
1
The H NMR spectra of aza adducts VI and VII
show similar sets of signals, implying diastereohomo-
geneity of these compounds (Table 2). For example, in
the spectrum of compound VII the morpholine ring
proton signals appear as multiplets at 2.16–2.48, 2.52–
(CH N) and 66.93, 66.82 ppm (CH O), and the СН
2 2 А
and СН signals are observed at 76.24, 75.13 and
В
67.30, 67.43 ppm, respectively (Table 2). Such
1
3
1
assignment of the
С–{ H} NMR spectra was
1
13
1
13
confirmed by the Н– С HMQC and Н– С HMBC
2
.75, and 3.50–3.77 ppm, the HA and H methine
experiments (Fig. 2 and 3). For example, in the HMBC
B
protons form two doublets at 6.25 and 4.31 ppm
spectrum of compound VII the H signal forms cross
A
3
2
2' 3
(
J = 10.9 Hz), and the furan ring protons resonate as
peaks with the СН ( J) and С ( J) signals, and the H
В
В
3
3
2
two doublets at 6.34 and 6.36 ppm ( J = 3.3 Hz),
which does not contradict the data for structurally
related 2,5-disubstituted furan [15] and N-substituted
morpholines [16].
signal forms gross peaks with the CH N ( J), CH ( J),
2 A
3
'
3
2' 2
C ( J), and C ( J) signals.
The IR spectra of aza adducts VI and VII contain
strong absorption bands of the unconjugated nitro
1
3
1
–1
The С–{ H} NMR spectra of aza adducts VI and
VII contain sets of signals at 112.32–147.92 (VII) and
group (1575–1576, 1356–1358 cm ). In the IR
spectrum of compound VI the nitro group conjugated
–
1
1
11.77–152.69 ppm (VI) from furan ring carbons. The
with the furan ring gives a ν band at 1535 cm , and
as
morpholine ring carbons appear at 50.27, 50.34
the band of symmetric stretching vibrations appears at
Table 2. Yields, melting points, and spectral characteristics of aza adducts VI and VII
4'
3'
Br
HA
NO2
5'
2'
1
O
'
X
HB
N
4
3
2
5
6
1
O
–1
δ, ppm (J, Hz)
ν, cm
1
13
1
Yield,
%
mp,
°С
Н
С–{ H}
X
CHBrNO
2
4'
3'
CH
CH
B
С , C ,
4'
3'
(
Fur-NO
2
)
CH
2
O
CH
2
N
С H, C H
H
A
H
B
2 2
CH O CH N
5
'
2'
(
A
)
C , C
111.77, 1576 s,
(75.13) 114.82, 1356 s
152.69, (1535 m,
49.52 1356 s)
112.32, 1575 s,
VI NO
2
88
106–107 3.57– 2.30–2.38 m, 7.34 d, 6.32 d 4.49 d 66.82 50.34
decomp.) 3.68 m 2.69–2.74 m 6.62 d
67.43
(
3
[
J 3.7]
[JAB 10.9]
1
VII Br
83
102–104 3.50– 2.16–2.48
decomp.) 3.77 m m,
.52–2.75 m
6.34 d, 6.25 d 4.31 d 66.93 50.27
6.36 d
67.30
(
(76.24) 114.63, 1358 w
123.23,
2
1
47.92
3
[
J 3.3]
[JAB 10.9]
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 85 No. 6 2015

1
428
ELISEENKO et al.
C
δ , ppm
δ, ppm
1
13
Fig. 2. H– C HMQC spectrum of compound VI.
C
δ , ppm
δ, ppm
1
13
Fig. 3. H– C HMBC spectrum of compound VI.
the same position as the same band of the un-
conjugated nitro group (1356 cm ).
EXPERIMENTAL
–
1
Physicochemical measurements were performed at
the Center for Collective Use, Department of Chemistry,
Herzen State Pedagogical University of Russia.
Thus, we developed a convenient method of syn-
thesis of 2-(2-bromo-2-nitroethenyl)-5-nitrofuran. This
nitroalkene and its analog with a 5-bromofuryl substituent
were used to obtain amination products with morpholine.
1
13
1
1
13
The Н, C–{ H}, and H– C HMQC and HMBC
NMR spectra were obtained on a Jeol ECX400A
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 85 No. 6 2015

FURAN-CONTAINING gem-BROMONITROETHENES
1429
1
13
instrument at 399.78 ( Н) and 100.53 MHz ( С) in
suspension at 18–20°С. The reaction mixture was
allowed to stand for 10 min at 18–20°С, poured onto
ice chips, and the precipitate that formed was filtered
off to obtain 2.22 g (97%) of compound III as yellow
crystals, mp 89–90°С (ethanol). Mixed sample with
the compound obtained by procedure а showed no
melting point depression.
chloroform-d and referenced based on the residual
proton signals of the deuterated solvent. The IR spectra
were recorded on a Shimadzu IRPrestige-21 FTIR
spectrometer in chloroform (с = 40 mg/mL). The elec-
tronic absorption spectra were measured on a
Shimadzu UV2401PC spectrophotometer in ethanol in
quartz cells (l = 1.01 mm). Elemental analysis was
performed on a EuroVector EA3000 (CHN Dual) analyzer.
5-Bromo-2-(2-bromo-2-nitroethenyl)furan (V).
A solution of 3.7 mL (11.55 g, 72 mmol) of bromine in
Nitroethenes I and IV were prepared by the
procedures described in [17] and [18], respectively.
1
0 mL of chloroform was added dropwise to a solution
of 5.03 g (36 mmol) of 2-(2-nitroethenyl)furan (IV) in
0 mL of chloroform at –7 to –5°С. The reaction
2
2
-(1,2-Dibromo-2-nitroethyl)-5-nitrofuran (II).
mixture was stirred for 3.5 h at 18–20°С, and the sol-
vent and excess bromine were evaporated in a Petri
dish to leave a light yellow oil which, without additional
treatment, was dissolved in 80 mL of ethanol. A
solution of 5.67 g (57.8 mmol) of melted potassium
acetate in 80 mL of ethanol was added to the resulting
solution at 18–20°С. The reaction mixture was allowed
to stand for 10 min at 18–20°С, poured onto ice chips,
and the precipitate that formed was filtered off to
obtain 7.28 g (68%) of compound V as dark yellow
crystals, mp 90–91°С (hexane) (mp 87–89°С [10]).
A solution of 10.67 mL (33.11 g, 207 mmol) of
bromine in 20 mL chloroform was added dropwise to a
suspension of 7.63 g (41 mmol) of 5-nitro-2-(2-nitro-
ethenyl)furan (I) в 85 mL chloroform. The reaction
mixture allowed to stand for 24 h at 18–20°С, and the
solvent and excess bromine were evaporated in a Petri
dish to obtain 14.10 g (99%) of compound II as
colorless crystals, mp 105–108°С (CCl ) (mp 110–
4
–
1
1
11°С [19]). IR spectrum, ν, cm : 1580, 1354 (C–
1
NO ), 1541, 1354 (Fur–NO ), 1507 (Fur). Н NMR
spectrum, δ, ppm (J, Hz): 5.65 d (1Н, H , J 10.7),
6
2
2
3
B
3
3
3'
.46 d (1Н, H , J 10.7), 6.80 d (1Н, C H, J 3.7), 7.31
A
4
-[2-Bromo-2-nitro-1-(5-nitrofuran-2-yl)ethyl]-
morpholine (VI). A solution of 0.16 mL (0.16 g,
.83 mmol) of morpholine in 13 mL of ethanol was
4
'
3
13
1
d (1Н, C H, J 3.7). С–{ H} NMR spectrum, δ ,
C
ppm: 30.09 (CH ), 75.59 (CH ), 112.03, 114.36,
B
A
1
3
'
4'
2'
5'
1
49.20, 152.40 (С , C , C , C ). Found, %: C 20.64;
added to a suspension of 0.48 g (1.83 mmol) of
compound III in 15 mL of ethanol at –10 to –8°С. The
reaction mixture was allowed to stand for 1 h at –10 to
H 1.31. C H Br N O . Calculated, %: C 20.95; H 1.17.
6
4
2
2
5
2
-(2-Bromo-2-nitroethenyl)-5-nitrofuran (III). a.
–
6°С. The precipitate was filtered off. Yield 0.31 g
A solution of 4.08 g (41.5 mmol) of melted potassium
acetate in 55 mL of ethanol was added dropwise to a
suspension of 8.93 g (26 mmol) of 2-(1,2-dibromo-2-
nitroethyl)-5-nitrofuran (II) in 55 mL of ethanol at 18–
(
49%), mp 106–107°С (decomp., ethanol).
The mother liquor was poured onto ice chips, and
an additional 0.25 g (39%) of compound VI was
filtered off, mp 106–107°С (decomp., ethanol). Mixed
sample with the substance isolated from the reaction
solution showed no melting point depression. Total
yield 88%. Found, %: C 33.99, 33.82; H 3.43, 3.40; N
2
1
0°С. The reaction mixture was stirred for 15 min at
8–20°С, poured onto ice chips, and the precipitate
that formed was filtered off to obtain 6.62 g (97%) of
compound III as yellow crystals, mp 89–90°С
(
ethanol) (mp 88–89°С [9]).
1
1.95, 12.03. C H BrN O . Calculated, %: C 34.30;
10 12 3 6
b. A solution of 2.2 mL (6.94 g, 43 mmol) of
H 3.45; N 12.00.
bromine in 8 mL of chloroform was added to a suspen-
sion of 1.6 g (8.7 mmol) of 5-nitro-2-(2-nitroethenyl)-
furan (I) in 15 mL of chloroform. The reaction mixture
was stirred for 24 h at 18–20°С, and the solvent and
excess bromine were evaporated in a Petri dish to
leave a solid residue which, without additional
treatment, was mixed with 15 mL of ethanol. A
solution of 1.36 g (14 mmol) of melted potassium
acetate in 15 mL of ethanol was added to the resulting
4-[2-Bromo-1-(5-bromofuran-2-yl)-2-nitroethyl]-
morpholine (VII) was prepared in a similar way from
1.41 g (4.75 mmol) of compound V and 0.41 mL (0.41
g, 4.75 mmol) of morpholine in 30 mL of ethanol at –8
to –5°С for 1 h. Yield 1.51 g (83%), mp 102–104°С
(decomp., ethanol). Found, %: C 31.05, 31.32; H 3.33,
3.31; N 7.13, 7.26. C10
31.28; H 3.15; N 7.29.
H12Br N O . Calculated, %: C
2 2 4
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 85 No. 6 2015

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ELISEENKO et al.
1972, vol. 6, no. 10, p. 629.
ACKNOWLEDGMENTS
9
. Gruntfest, M.G., Potemkin, G.F., Kolodyazhnyi, Yu.V.,
Zverev, V.V., Nazarova, Z.N., and Osipov, O.A., Zh.
Org. Khim., 1972, vol. 8, no. 2, p. 404.
The work was financially supported by the Ministry
of Education and Science of the Russian Federation in
the framework of the basic part of the State order.
10. Palmieri, A., Gabrielli, S., and Ballini, R., Synlett, 2013,
vol. 24, p. 114. DOI: 10.1055/s-0032-1317695.
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