Synthesis of nitro pyrido- and dipyrido[1,4]oxazines

Article abstract of DOI:10.1016/j.mencom.2016.09.005

3-Nitro-10H-pyrido[3,2-b][1,4]benzoxazines and first representative of a new heterocyclic system, 10H-dipyrido[2,3-e:3’,2’-b][1,4]oxazine, were obtained by reaction of 2-chloro-3,5-dinitropyridine with various o-aminophenols followed by intramolecular sub

Full text of DOI:10.1016/j.mencom.2016.09.005

Mendeleev
Communications
Mendeleev Commun., 2016, 26, 383–385
Synthesis of nitro pyrido- and dipyrido[1,4]oxazines
Maxim A. Bastrakov,*a Anastasiya O. Geraseva,a Alexey M. Starosotnikov,a
Ivan V. Fedyanin,b Alexander A. Pavlov,b Bogdan I. Ugraka and Svyatoslav A. Sheveleva
a N. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, 119991 Moscow, Russian
Federation. Fax: +7 499 135 5328; e-mail: b_max82@mail.ru
b A. N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences, 119991 Moscow,
Russian Federation
DOI: 10.1016/j.mencom.2016.09.005
HO
R1
R2
O2N
NO2
Et3N
+
3-Nitro-10H-pyrido[3,2-b][1,4]benzoxazines and first repre-
sentative of a new heterocyclic system, 10H-dipyrido[2,3-e:
3',2'-b][1,4]oxazine, were obtained by reaction of 2-chloro-
3,5-dinitropyridine with various o-aminophenols followed
by intramolecular substitution of the nitro group.
MeOH, room
temperature
H2N
X
N
Cl
R2
NO2
O2N
R1
O2N
O
R1
R2
Et3N
DMF,
X
N
N
N
N
X
100 °C
H
H
OH
Nitro(het)arenes represent a unique class of aromatic compounds
possessing dual reactivity towards reactions with nucleophiles.
They undergo nucleophilic aromatic substitution (SNAr) when the
nitro group acts as one of the best nucleofugal groups as well as
activating groups for the substitution of other types of nucleofugs,
e.g. halogens.1 At the same time, nitro(het)arenes also tend to
additions to the aromatic ring (for example, SNHAr).2
This work is a part of our ongoing research on application of
available (het)aromatic nitro compounds as precursors of various
fused heterosystems.3 Here we report on reactions of 2-chloro-
3,5-dinitropyridine with different o-aminophenols. Such interac-
tions may lead to nitro azaphenoxazines. Phenoxazines are
tricyclic heterocycles which have found use as therapeutic agents
and scaffolds in medicinal chemistry.4 For example, phenoxazine
moiety is a part of Dactinomycin, a naturally occurring anti-
biotic.5 Due to their photophysical properties,6 phenoxazines
have been applied as dyes in dye-sensitized solar cells7 and
chemosensors.8 Someazaphenoxazines(includingnitroderivatives)
were used in therapy and diagnostics of neurodegenerative dis-
orders, such as Parkinson’s and Alzheimer’s diseases,9,10 how-
ever, the synthesis of these compounds has not been reported.
We have found that reaction of 2-chloro-3,5-dinitropyridine 1
with o-aminophenols 2a–e in methanol in the presence of Et3N
afforded compounds 3a–e, the products of replacement of chlorine
atoms with amino group of o-aminophenol (Scheme 1).†
Heating of 3a–e in DMF in the presence of base causes the
intramolecular nucleophilic substitution of ortho-positioned nitro
group leading to tricycles 4a–e (Scheme 1).
†
All chemicals were of commercial grade and used directly without
purification. Melting points were measured on a Stuart SMP20 apparatus.
The 1H and 13C NMR spectra were recorded from solutions in DMSO-d6
with a Bruker Avance 300 FT-spectrometer (300 and 75 MHz respec-
tively). Chemical shifts are reported in ppm downfield from TMS. All
reactions were monitored by TLC analysis usingALUGRAM SIL G/UV254
plates, which were visualized by UV light.
General procedure for the synthesis of 3a–e, 7. Triethylamine (0.42 ml,
3 mmol) was added to a solution of 1 (0.6 g, 1 mmol) and corresponding
o-aminophenol (3 mmol) in MeOH (30 ml). The reaction mixture was
stirred at room temperature for 1–2 h (TLC monitoring). Then the mixture
was poured into water (150 ml) and acidified with HCl to pH 5–6. The
precipitate was filtered off, washed with water and dried in air.
2-[(3,5-Dinitropyridin-2-yl)amino]phenol 3a. Yield 93%, mp 240–241°C
(lit.,13 240–241°C). 1H NMR, d: 6.84–7.11 (m, 3H), 8.25 (d, 2H,
J 7.7 Hz), 9.05 (s, 1H), 9.32 (s, 1H), 10.43 (s, 1H), 10.92 (s, 1H).
13C NMR, d: 150.70, 150.52, 148.45, 134.50, 131.02, 127.23, 126.00,
125.34, 122.40, 119.18, 115.05. Found (%): C, 47.94; H, 2.68; N, 20.72.
Calc. for C11H8N4O5 (%): C, 47.83; H, 2.92; N, 20.28.
2-[(3,5-Dinitropyridin-2-yl)amino]-5-methylphenol 3b. Yield 86%,
mp 232–233°C. 1H NMR, d: 2.27 (s, 3H), 6.68 (d, 1H, J 8.2 Hz), 6.78 (s,
1H), 8.10 (d, 1H, J 8.2 Hz), 9.05 (d, 1H, J 2.0 Hz), 9.27 (d, 1H, J 2.3 Hz),
10.17 (s, 1H), 10.82 (s, 1H). 13C NMR, d: 150.49, 148.27, 135.53, 134.23,
130.90, 127.01, 122.81, 122.19, 121.98, 119.72, 115.56, 20.74. Found (%):
C, 49.70; H, 3.30; N, 19.19. Calc. for C12H10N4O5 (%): C, 49.66; H, 3.47;
N, 19.30.
2-[(3,5-Ddinitropyridin-2-yl)amino]-4-methylphenol 3c. Yield 90%,
mp 234–235°C. 1H NMR, d: 2.27 (s, 3H), 6.88 (s, 2H), 8.08 (s, 1H), 9.07
(s, 1H), 9.34 (s, 1H), 10.18 (s, 1H), 10.89 (s, 1H). 13C NMR, d: 150.54,
146.14, 134.39, 130.96, 127.87, 127.12, 126.34, 125.05, 122.64, 114.79,
20.58. Found (%): C, 49.52; H, 3.65; N, 19.12. Calc. for C12H10N4O5 (%):
C, 49.66; H, 3.47; N, 19.30.
HO
R1
R2
O2N
NO2
Cl
Et3N
+
MeOH, room
temperature
H2N
N
1
2a–e
O2N
R2
NO2
O
R1
R2
O2N
R1
Et3N
DMF,
100 °C
N
N
H
N
N
H
OH
3a–e, 86–93%
4a–e, 83–95%
4-Chloro-2-[(3,5-dinitropyridin-2-yl)amino]phenol 3d. Yield 87%,
mp 250–251°C. 1H NMR, d: 6.95 (d, 1H, J 8.5 Hz), 7.10 (d, 1H, J 8.3 Hz),
8.38 (s, 1H), 9.07 (s, 1H), 9.38 (s, 1H), 10.79 (s, 1H), 10.90 (s, 1H).
13C NMR, d: 150.43, 146.98, 134.95, 130.93, 127.54, 126.57, 125.04,
122.53, 121.06, 115.93. Found (%): C, 42.68; H, 2.12; Cl, 11.84; N, 17.99.
Calc. for C11H7ClN4O5 (%): C, 42.53; H, 2.27; Cl, 11.41; N, 18.04.
a R1 = R2 = H
d R1 = H, R2 = Cl
e R1 = H, R2 = Br
b R1 = Me, R2 = H
c R1 = H, R2 = Me
Scheme 1
© 2016 Mendeleev Communications. Published by ELSEVIER B.V.
on behalf of the N. D. Zelinsky Institute of Organic Chemistry of the
Russian Academy of Sciences.
– 383 –

Mendeleev Commun., 2016, 26, 383–385
5
O
6
4
NOE
It is known11 that such reactions can in principle give two
O2N
5a
4a
7
8
3
2
isomeric products 4 or 5 (Scheme 2). In the case of path A the
substitution of ortho-NO2 occurs under the action of phenolate
anion and tricycles 4 are formed. Product 5 can be formed as a
result of Smiles rearrangement (path B). Such transformations
have been reported for the synthesis of phenoxazines on the basis
of nitroarenes.12
H
4
H
N
H
10
6
9a
10a
N
N
Br
O2N
Br
5a
4a
9
5
3
2
7
8
H
H
10
O
1
N
9a
10a
9
NOE
4e
5e
Figure 1 Cross-peak interaction of protons in isomeric 4e and 5e.
R2
O2N
R1
NO2
To the best of our knowledge the only azaphenoxazine 4a has
been described so far.13 It was synthesized in a manner similar to
indicated in Scheme 1, however its structure was assigned based
on elemental analysis and 1H NMR spectrum.† At the same time,
these data are insufficient to distinguish 4a from its isomer 5a.
We carried out a detailed study of the structures of compounds 4
N
N
H
OH
3a–e
DMF,
100 °C
Et3N
1
using various NMR experiments. For example, H-1H NOESY
path A
path B
spectrum of 4e contains characteristic cross-peak corresponding
to the interaction of spatially close H9 and NH protons (Figure 1).
In case of Smiles rearrangement (formation of compound 5e)
two cross-peaks are expected to appear in NOESY spectrum,
corresponding to the interaction of NH proton with H4 and H6.
These data allowed us to unambiguously confirm the structure of
compounds 4.
O2N
O
R1
R2
O2N
NO2
O
N
N
H
N
R1
HN
4a–e
R2
In addition, the structures of 3a and 4a were proved by single-
R1
crystal X-ray diffraction studies.‡ The structure of 3a (Figure 2)
H
N
O2N
R2
R1
NO2
O2N
R2
O(2)
O(1)
H(8)
N(3)
O(8)
C(8)
N
O
N
O
H(2)
N(2)
NH2
5a–e
C(3)
C(9)
C(4)
Scheme 2
C(2)
N(1)
C(7)
C(10)
C(5)
O(3)
4-Bromo-2-[(3,5-dinitropyridin-2-yl)amino]phenol 3e. Yield 91%,
mp 247–248°C. 1H NMR, d: 6.92 (d, 1H, J 8.6 Hz), 7.20 (dd, 1H, J 8.4 and
2.2 Hz), 8.49 (d, 1H, J 2.0 Hz), 9.07 (d, 1H, J 2.4 Hz), 9.39 (d, 1H, J 2.4 Hz),
10.85 (s, 1H), 10.91 (s, 1H). 13C NMR, d: 150.44, 147.44, 134.94, 130.94,
128.04, 127.55, 126.95, 123.96, 116.53, 109.97. Found (%): C, 37.55;
H, 1.90; Br, 22.43; N, 15.69. Calc. for C11H7BrN4O5 (%): C, 37.21; H,
1.99; Br, 22.50; N, 15.78.
2-[(3,5-Dinitropyridin-2-yl)amino]pyridin-3-ol 7. Yield 55%,
mp 245–246°C. 1H NMR, d: 6.87–7.09 (m, 3H), 8.27 (d, 2H, J 7.6 Hz),
9.07 (s, 1H), 9.33 (s, 1H), 10.44 (s, 1H), 10.93 (s, 1H). 13C NMR, d:
150.67, 150.50, 148.42, 134.49, 131.00, 127.21, 125.97, 125.33, 122.35,
119.17, 115.03. Found (%): C, 43.43; H, 2.37; N, 25.10. Calc. for
C10H7N5O5 (%): C, 43.33; H, 2.55; N, 25.27.
General procedure for the synthesis of 4a–e, 8. Triethylamine (0.14 ml,
1 mmol) was added to a solution of compound 3a–e or 7 in DMF (15 ml).
The reaction mixture was kept at 100°C for 4–8 h (TLC monitoring).
Then the mixture was poured into water (150 ml) and acidified with HCl
to pH 1–2. The precipitate that formed was filtered off, washed with water
and dried in air.
C(12)
N(5)
O(4)
C(11)
C(6)
Figure 2 General view of one of three independent molecules in crystal of
3a in thermal ellipsoid representation at 50% probability level. Selected bond
lengths (Å): O(1)–N(3) 1.250(4), O(2)–N(3) 1.224(4), O(3)–N(5) 1.213(4),
O(4)–N(5) 1.232(4), O(8)–C(8) 1.369(5), N(1)–C(6) 1.326(5), N(1)–C(2)
1.364(5), N(2)–C(2) 1.342(5), N(2)–C(7) 1.405(5), N(3)–C(3) 1.446(5),
N(5)–C(5) 1.452(5), C(2)–C(3) 1.424(5), C(3)–C(4) 1.379(5), C(4)–C(5)
1.384(5), C(5)–C(6) 1.376(6), C(7)–C(12) 1.395(5), C(7)–C(8) 1.408(5),
C(8)–C(9) 1.369(6), C(9)–C(10) 1.392(6), C(10)–C(11) 1.392(6), C(11)–C(12)
1.366(5). Corresponding bond lengths in two other independent molecules
are very close to given values.
8-Chloro-3-nitro-10H-pyrido[3,2-b][1,4]benzoxazine 4d. Yield 95%,
1
mp 223–224°C. H NMR, d: 6.61–6.71 (m, 3H), 7.41 (s, 1H), 8.41 (s,
1H), 10.25 (br.s, 1H). 13C NMR, d: 149.79, 140.89, 140.38, 138.39, 138.29,
130.29, 128.04, 122.55, 116.54, 114.44, 114.24.
3
-Nitro-10H-pyrido[3,2-b][1,4]benzoxazine 4a. Yield 83%, mp 267–268°
C
8-Bromo-3-nitro-10H-pyrido[3,2-b][1,4]benzoxazine 4e. Yield 79%,
mp 253–254°C. 1H NMR, d: 6.69–6.91 (m, 3H), 7.49 (s, 1H, H-4), 8.48
(s, 1H, H-2), 10.41 (br.s, 1H, NH). 13C NMR, d: 150.40 (C-3), 141.95
(C-9a), 141.02 (C-2), 138.96 (C-10a), 138.82 (C-4a), 131.17 (C-5a),
126.11 (C-7), 117.70 (C-9), 117.57 (C-6), 116.29 (C-8), 114.87 (C-4).
Found (%): C, 42.99; H, 2.01; Br, 25.81; N, 13.52. Calc. for C11H6BrN3O3
(%): C, 42.88; H, 1.96; Br, 25.94; N, 13.64.
(lit.,13 275–276°C). 1H NMR, d: 6.65–6.87 (m, 4H), 7.44 (d, 1H, J 2.1 Hz),
8.45 (d, 1H, J 2.2 Hz), 10.35 (s, 1H). 13C NMR, d: 150.55, 141.98, 140.62,
138.56, 137.93, 128.62, 124.70, 123.57, 115.28, 115.22, 113.92. Found (%):
C, 57.50; H, 3.01; N, 18.52. Calc. for C11H7N3O3 (%): C, 57.65; H, 3.08;
N, 18.33.
7-Methyl-3-nitro-10H-pyrido[3,2-b][1,4]benzoxazine 4b. Yield 89%,
mp 257–258°C. 1H NMR, d: 2.14 (s, 3H), 6.56–6.73 (m, 3H), 7.44 (s, 1H),
8.46 (s, 1H), 10.30 (br.s, 1H). 13C NMR, d: 150.52, 141.69, 140.67,
138.38, 137.60, 133.14, 125.84, 124.74, 115.78, 114.95, 113.73, 20.13.
Found (%): C, 59.50; H, 3.51; N, 17.52. Calc. for C12H9N3O3 (%): C, 59.26;
H, 3.73; N, 17.28.
8-Methyl-3-nitro-10H-pyrido[3,2-b][1,4]benzoxazine 4c. Yield 88%,
mp 277–278°C. 1H NMR, d: 2.15 (s, 3H), 6.51–6.64 (m, 3H), 7.42 (s, 1H),
8.45 (s, 1H),10.20 (br.s, 1H). 13C NMR, d: 150.49, 140.41, 139.79, 138.58,
137.84, 133.79, 128.15, 123.62, 115.57, 114.94, 113.72, 20.14. Found (%):
C, 59.63; H, 3.25; N, 17.58. Calc. for C12H9N3O3 (%): C, 59.26; H, 3.73;
N, 17.28.
3-Nitro-10H-dipyrido[2,3-e:3',2'-b][1,4]oxazine 8. Yield 80%,
mp 264–265°C. 1H NMR, d: 6.76 (s, 1H), 7.04 (d, 1H, J 2.1 Hz), 7.52 (s,
1H), 7.67 (s, 1H), 8.48 (s, 1H), 10.80 (s, 1H). 13C NMR, d: 150.71, 143.24,
142.49, 140.25, 138.79, 138.61, 121.64, 119.31, 114.50. Found (%):
C, 52.50; H, 2.22; N, 24.52. Calc. for C10H6N4O3 (%): C, 52.18; H, 2.63;
N, 24.34.
‡
Crystallographic data.
For 3a: crystals are monoclinic, space group P21/c, a = 6.96480(10),
b = 11.2318(2) and c = 43.2214(7) Å, b = 92.7800(10)°, V = 3377.11(9) Å3,
Z = 12 (Z' = 3), dcalc = 1.630 g cm–3, R1 = 0.0751 [for 5841 reflections
with I > 2s(I)], wR2 = 0.1785, GOF = 1.059.
– 384 –

Mendeleev Commun., 2016, 26, 383–385
HO
O2N
NO2
Cl
O(3)
N(5)
Et3N
O(8)
+
C(4)
C(3)
C(9)
MeOH, room
temperature
C(8)
C(7)
C(5)
H2N
N
N
C(10)
O(4)
1
6
C(6)
C(2)
N(2)
C(11)
C(12)
NO2
O2N
O
O2N
N(1)
Et3N
N
H(2)
DMF,
100 °C
Figure 3 General view of 4a in crystal in thermal ellipsoid representation
at 50% probability level. Selected bond lengths (Å): O(3)–N(5) 1.2337(14),
O(4)–N(5) 1.2278(14), O(8)–C(3) 1.3755(15), O(8)–C(8) 1.3961(16),
N(1)–C(2) 1.3403(16), N(1)–C(6) 1.3430(17), N(2)–C(2) 1.3488(17),
N(2)–C(7) 1.4019(16), N(5)–C(5) 1.4458(17), C(2)–C(3) 1.4253(17),
C(3)–C(4) 1.3609(19), C(4)–C(5) 1.4055(17), C(5)–C(6) 1.3751(18),
C(7)–C(12) 1.3864(19), C(7)–C(8) 1.3951(18), C(8)–C(9) 1.3773(18),
C(9)–C(10) 1.390(2), C(10)–C(11) 1.3862(19), C(11)–C(12) 1.3879(18).
N
N
H
N
N
H
N
OH
7, 55%
8, 80%
Scheme 3
This work was supported by the Russian President’s Council
for Grants (grant no. MK-3450.2015.3).
contains three independent molecules in the unit cell. These
molecules are almost planar, except for out-of-plane rotation of
nitro groups. Relative orientation of pyridine and phenyl rings is
fixed by intramolecular N(2)–H(2)···O(1) hydrogen bond [N···O
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hydrogen bond with oxygen atom of hydroxyl group [N···O
2.577(4), 2.582(4) and 2.579(4) Å] can also be considered, but the
corresponding five-membered H-bonded ring is not energetically
favorable. Hydrogen atoms of hydroxyl groups in 3a participate
in relatively weak intermolecular H-bonds with oxygen atoms
of nitro groups. The heterocyclic fragment in 4a (Figure 3) is
virtually planar. As in case of 4a, the bond N(2)–C(2) is shorter
than N(2)–C(7) by ca. 0.05 Å that implies more effective con-
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the pyridine ring than with one of the phenyl ring. Small changes
in the bond length distribution are expected in 4a comparing to
3a, as the central ring in the former in not aromatic. The
difference in bond lengths is also observed for O(8)–C(3) and
O(8)–C(8) bonds in 4a, the latter being ca. 0.02Å shorter. Hydrogen
atom of amino group in 4a participates in intermolecular N–H···N
hydrogen bond with nitrogen atom of pyridine ring [N···N
2.9969(15) Å], connecting molecules into centrosymmetric
dimers.
Pyridine analogue of o-aminophenols, 2-aminopyridin-3-ol
6, reacts with chloride 1 in the similar manner. In this case the
formation of new hetrerocyclic system, 3-nitro-10H-dipyrido-
[2,3-e:3',2'-b][1,4]oxazine 8 occurs (Scheme 3).
In conclusion, we accessed a series of new 3-nitro-10H-pyrido-
[3,2-b][1,4]benzoxazines 4a–e as well as representative of new
heterocyclic system, 10H-dipyrido[2,3-e:3',2'-b][1,4]oxazine 8.
Such compounds are analogues of anti-neurodegenerative drugs.
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15 (a) M. Ma˛kosza and K. Wojciechowski, in Topics in Heterocyclic
For 4a: crystals are monoclinic, space group P21/n, a = 5.62730(10),
b = 8.1437(2) and c = 20.7305(5) Å, b = 96.5350(10)°, V = 943.84(4) Å3,
Z = 4 (Z' = 1), dcalc = 1.613 g cm–3, R1 = 0.0348 [for 1530 reflections with
I > 2s(I)], wR2 = 0.0991, GOF = 1.028.
Both experiments were performed on a Bruker Apex DUO diffracto-
meter at 120 K using CuKa radiation (l = 1.54178 Å). The structures
were solved by direct methods and refined by full-matrix least-squares
technique against Fh2kl in anisotropic approximation. Hydrogen atoms
bonded to carbon atoms were placed into calculated positions and refined
in riding model with Uiso(H) = 1.2Ueq(C), hydrogen atoms bonded to
nitrogen and oxygen atoms were found from difference Fourier synthesis
and refined in isotropic approximation. All calculations were performed
using SHELX software package.14
C
hemistry, eds. V. Charushin and O. Chupakhin, 2014, vol. 37, pp. 51–106
;
(b) S. Shevelev and A. Starosotnikov, in Topics in Heterocyclic Chemistry
,
eds. V. Charushin and O. Chupakhin, 2014, vol. 37, pp. 107–154.
CCDC 1455656 and 1455657 contain the supplementary crystallographic data
for this paper. These data can be obtained free of charge from The Cambridge
Crystallographic Data Centre via http://www.ccdc.cam.ac.uk.
Received: 9th March 2016; Com. 16/4865
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