Reactions of pyridoxal with aromatic diamines

Article abstract of DOI:10.1007/s10593-020-02663-y

[Figure not available: see fulltext.] Pyridoxal monoimines were obtained by the reaction of pyridoxal with aromatic diamines. A change in the ratio of the reagents or introduction of another aromatic aldehyde into the reaction leads to the formation of sy

Full text of DOI:10.1007/s10593-020-02663-y

DOI 10.1007/s10593-020-02663-y
Chemistry of Heterocyclic Compounds 2020, 56(3), 326–330
Reactions of pyridoxal with aromatic diamines
Roza Kh. Bagautdinova1*, Lyudmila K. Kibardina1, Alexander R. Burilov1,
Anna G. Strelnik1, Mikhail A. Pudovik1
1 Arbuzov Institute of Organic and Physical Chemistry,
Federal Research Center ''Kazan Scientific Center of the Russian Academy of Sciences'',
8 Akademika Arbuzova St., Kazan 420088, Russia; e-mail: bagrosa@iopc.ru
Translated from Khimiya Geterotsiklicheskikh Soedinenii,
2020, 56(3), 326–330
Submitted November 1, 2019
Accepted after revision January 29, 2020
Pyridoxal monoimines were obtained by the reaction of pyridoxal with aromatic diamines. A change in the ratio of the reagents or
introduction of another aromatic aldehyde into the reaction leads to the formation of symmetric and asymmetric diimines. In some cases,
the initially formed diimines are transformed into the corresponding benzimidazoles. The products of the reaction of pyridoxal with
1,3-diaminobenzene have a furopyridine structure.
Keywords: aromatic aldehydes, aromatic diamines, benzimidazoles, diimines, imines, furopyridines, pyridoxal.
Interest in the synthesis of functionalized derivatives of
pyridoxal (vitamin B6) and the study of their biological
activity has been ongoing from the moment of synthesis of
the first representatives of this class of compounds up to
the present. The central place among pyridoxal derivatives
is occupied by imino derivatives (Schiff bases)1–3 due to
their wide use as ligands in coordination chemistry.4,5 They
are also successfully used as biologically active
compounds,6–8 analytical reagents,9 catalysts.10
the literature that the reaction of pyridoxal (1) hydro-
chloride and 1,2-diaminobenzene (2a) in MeOH solution in
the presence of KOH leads to the formation of monoimine
3a.14 Moreover, this result was obtained using both
equimolar amounts of reagents and a twofold excess of
pyridoxal. The formation of diimine in this reaction was
not recorded. In another work, a diimine was obtained as a
result of the reaction of 1,2-diaminobenzene (2a) with
pyridoxal (1) hydrochloride under similar conditions using
Et3N as the base.23
We repeated this reaction using pyridoxal (1) and 1,2-di-
aminobenzene (2a) or 1,4-diaminobenzene (2b) and
obtained the corresponding monoimines 3a,b (Scheme 1).
At the same time, the use of a double amount of
pyridoxal in the reaction with 1,2-diaminobenzene (2a)
when heating a solution in EtOH under reflux allowed us to
obtain the corresponding symmetric diimine 4. In the case
of diamine 2b, the reaction stopped at the stage of
formation of monoimine 3b even when using a double
amount of pyridoxal (1) (Scheme 1).
Pyridoxal readily reacts with primary aliphatic and
aromatic amines to form the corresponding azomethines.11–13
At the same time, various diamines were reacted with
pyridoxal. The bisazomethines formed in this process are
promising ligands for the production of metal complexes
employed, for example, to determine nitrate and nitrite
anions and as catalysts in various chemical
transformations.14–21 It is noted that when alkylene
diamines are employed, regardless of the ratio and nature
of the starting aldehydes, only the corresponding
bisazomethines are formed.11,22 Data on the reaction of
aromatic diamines with pyridoxal are scarce and
contradictory.
It should be noted that in the reaction of pyridoxal (1)
with 1,3-diaminobenzene (2c) under similar conditions
using aldehyde and diamine in a 1:1 ratio, a mixture of two
tautomeric forms is formed, according to 1H NMR
We used 1,2-, 1,3-, and 1,4-diaminobenzenes 2a–c as
the objects of study (Schemes 1, 2). There is information in
0009-3122/20/56(3)-0326©2020 Springer Science+Business Media, LLC
326

Chemistry of Heterocyclic Compounds 2020, 56(3), 326–330
Scheme 1
Scheme 3
OH
EtOH
Me
CHO
OH
2c
2
+
80°C, 7 h
75%
N
1
OH
Me
HN
HO
N
HO
N
O
Me
N
7
Since the reactions of pyridoxal (1) with aromatic
diamines initially give rise to stable monoimines, the latter
can be subjected to reactions with other aromatic aldehydes
in order to obtain new asymmetric diimines. However, it
turned out that the reactions of azomethine 3a with a
number of aromatic aldehydes (benzaldehyde (8a), 4-nitro-
benzaldehyde (8b), 4-hydroxybenzaldehyde (8c), 2-hydroxy-
benzaldehyde (8d)) produce a different synthetic result
(Scheme 4). The initially formed bisazomethines 9a–d in
this case undergo intramolecular cyclization, which is
accompanied by a 1,3-proton shift from the carbon atom of
the aryl fragment to the carbon atom in the pyridoxal, to the
corresponding benzimidazoles 10a–d.
spectroscopy: azomethine (compound 5) and aminoacetal
(compound 6). Heating the reaction mixture in an EtOH
solution under reflux for 6 h made it possible to isolate the
thermodynamically more stable tautomer 6 (Scheme 2).
Scheme 2
NH2
Scheme 4
OH
Me
N
N
5
EtOH
EtOH
OH
6
1 +
H2N
+
80°C, 6 h
68%
rt, 10 h
NH2
2c
OH
HN
O
Me
NH2
N
6
There is no absorption band characteristic of the C=N
bond in the IR spectrum of compound 6, but there is an
absorption band of stretching vibrations of the NH group at
1
3343 cm–1. In the H NMR spectrum of compound 6, the
protons of the methylene group appear as two doublets
with chemical shifts of 5.08 and 5.23 ppm and an identical
constant of 12 Hz. The singlet signal of the methine proton
of the furan ring is observed at 6.13 ppm. It should be
noted that there are few examples in the literature of
stabilization of pyridoxal azomethines as an isomeric
aminoacetal form, the formation of which is determined by
the structural features of the aromatic amine reagent. For
example, whereas the reaction of pyridoxal with
phenylamine leads to the formation of azomethine,
furopyridine is formed when 2-aminopyridine is used in
this reaction.24
As a result of the reaction of 1,3-diaminobenzene (2c)
with pyridoxal (1) in a 1:2 ratio, compound 7 was obtained
containing both furopyridine and azomethine fragments.
Apparently, the initially formed diimine undergoes an
intramolecular transformation with the participation of one
azomethine group and the formation of a furan fragment
(Scheme 3).
In the examined cases, ring closure in compounds 9a–d
can occur with the participation of one of two
nonequivalent nitrogen atoms of azomethine fragments and
lead to structurally different benzimidazoles (Scheme 4,
paths a, b). Based on the fact that the protons of the
methylene group in compounds 10a–d have close chemical
shifts, it can be assumed that path b is realized, and the
methylene group becomes the bridging link between the
pyridoxal and benzimidazole moieties.
327

Chemistry of Heterocyclic Compounds 2020, 56(3), 326–330
Scheme 5
1
Figure 1. Key correlations in Н–13С HMBC spectrum of com-
pound 10b.
To confirm this assumption, a set of NMR correlation
experiments (DEPT, COSY, 1H–13C HSQC, 1H–13C
HMBC) was performed for compounds 10a–d. For
compound 10b, for example, the chain of successive
correlations between the atoms Н-5/С-1, Н-5/С-7, Н-6/С-2,
and Н-7/С-3 (Fig. 1) allows one to differentiate in the
spectrum the signal corresponding to the CH2OH group
(7-CH2) from a signal of another methylene group (8-CH2).
Moreover, correlations between the H-8/C-3, H-8/C-4, and
H-8/C-2 atoms unambiguously indicate the location of the
methylene group within the structure. The correlation
between the H-11/C-9 atoms is an additional argument in
favor of the fact that, in compound 10b, the nitrophenyl
moiety is bonded to the imidazole directly rather than via
the methylene group. The structures of compounds 10a,c,d
were similarly established.
Examples of the formation of benzimidazoles in the
reactions of 1,2-diaminobenzene (2a) with aromatic
aldehydes are known, and for this process to occur, the
presence of mineral or organic acids (H2SO4, AcOH), a
high-boiling solvent, ultrasonic irradiation is required.25–27
In the case of imines based on pyridoxal (1), only brief
heating under reflux in an EtOH solution is sufficient for
this reaction to take place. Compound 10d was also
obtained by counter synthesis: the reaction of 1,2-di-
aminobenzene (2a) with salicylic aldehyde 8d gave
monoimine 11,28 treatment of which with pyridoxal (1)
leads to the formation of compound 10d (Scheme 5). The
reaction of furopyridine 6 with salicylic aldehyde 8d yields
compound 12 containing both azomethine and furopyridine
moieties.
nuclei). MALDI-TOF mass spectra were recorded on an
Ultraflex III TOF/TOF Bruker spectrometer (p-nitroaniline
matrix). Elemental analysis was performed on an Euro
Vector EA-3000 CHNS-analyzer.
4-{[(2-Aminophenyl)imino]methyl}-5-(hydroxymethyl)-
2-methylpyridin-3-ol (3a). 1,2-Diaminobenzene (2а) (0.65 g,
6 mmol) was added with stirring to a suspension of
3-hydroxy-5-(hydroxymethyl)-2-methylpyridine-4-carbalde-
hyde (1) (1.00 g, 6 mmol) in EtOH (20 ml). After 10 h, the
precipitate was filtered off, washed with EtOH (50 ml), and
dried. Yield 1.28 g (88%), yellow powder, mp 197–200°С
(mp 182–184°С14). IR spectrum, ν, cm–1: 1620 (С=N),
1
3332 (NН2). H NMR spectrum, δ, ppm (J, Hz): 2.45 (3H,
s, CH3); 4.77 (2Н, s, СН2О); 5.16 (1H, s, OH); 5.42 (2Н, s,
NH2); 6.67–7.21 (4Н, m, H Ar); 7.99 (1H, s, H pyridine);
9.09 (1H, s, СH); 13.77 (1H, s, OH). 13C NMR spectrum,
δ, ppm: 19.2; 59.0; 116.3; 117.4; 119.4; 121.0; 129.3; 133.8;
134.0; 138.7; 143.5; 148.5; 153.3; 159.0. Mass spectrum,
m/z: 258 [M+Н]+. Found, %: C 65.00; H 6.21; N 16.31.
C14H15N3O2. Calculated, %: C 65.34; H 5.89; N 16.33.
4-{[(4-Aminophenyl)imino]methyl}-5-(hydroxymethyl)-
2-methylpyridin-3-ol (3b) was obtained by the same
procedure as compound 3a from 3-hydroxy-5-(hydroxy-
methyl)-2-methylpyridine-4-carbaldehyde (1) (1.32 g,
8 mmol) and 1,4-diaminobenzene (2b) (0.86 g, 8 mmol).
Yield 1.89 g (93%), yellow powder, mp 226–228°С.
1
IR spectrum, ν, cm–1: 1635 (С=N), 3351 (NН2). H NMR
spectrum, δ, ppm (J, Hz): 2.41 (3H, s, CH3); 4.74 (2Н, s,
СН2О); 5.36 (1H, s, OH); 5.57 (2Н, s, NH2); 6.66 (2Н, d,
J = 7.4, H Ar); 7.30 (2Н, d, J = 7.4, H Ar); 7.93 (1H, s,
H pyridine); 9.07 (1H, s, СH); 14.49 (1H, s, OH). 13C NMR
spectrum, δ, ppm: 19.2; 59.0; 114.6; 121.0; 123.5; 133.3;
135.5; 136.5; 148.1; 150.2; 153.5; 154.0. Mass spectrum,
m/z: 258 [M+Н]+. Found, %: C 65.10; H 6.08; N 16.72.
C14H15N3O2. Calculated, %: C 65.34; H 5.89; N 16.33.
4,4'-{[1,4-Phenylenebis(azanylylidene)]bis(methanyl-
idene)}bis[5-(hydroxymethyl)-2-methylpyridin-3-ol] (4).
A mixture of 3-hydroxy-5-(hydroxymethyl)-2-methylpyri-
dine-4-carbaldehyde (1) (0.25 g, 1.5 mmol), 1,2-diamino-
benzene (2а) (0.08 g, 0.75 mmol), and EtOH (10 ml) was
heated under reflux for 7 h. The formed precipitate was
separated, washed with EtOH (40 ml), and dried. Yield
0.26 g (81%), orange powder, mp 193–195°С (mp 199°С23).
To conclude, it was found as a result of the study that
the reactions of pyridoxal with aromatic diamines proceed
in two steps, and the initially formed monoimines can be
used in successive synthesis of symmetric and asymmetric
diimines. For some of them, an unusual transformation was
observed, leading to the construction of a compound
containing both azomethine and furopyridine fragments.
Benzimidazoles with a pyridoxal moiety were obtained for
the first time.
Experimental
IR spectra were registered on a Bruker Tensor-27
spectrometer over 400–3600 cm–1 range in KBr pellets.
1H and 13C NMR spectra were acquired on a Bruker
Avance-400 spectrometer (400 and 101 MHz, respectively)
in DMSO-d6, using residual solvent signals as internal
1
IR spectrum, ν, cm–1: 1611 (С=N), 3332 (NН). H NMR
spectrum, δ, ppm (J, Hz): 2.38 (3Н, s, СН3); 2.40 (3H, s,
CH3); 4.77 (2Н, s, ОН); 5.17 (2Н, s, СН2О); 5.40 (2Н, s,
СН2О); 6.66 (1Н, t, J = 7.5, H Ar); 6.83 (1Н, d, J = 7.9, H Ar);
7.07 (1Н, t, J = 7.5, H Ar); 7.20 (1Н, d, J = 7.6, H Ar); 7.99
1
standard (2.50 ppm for Н nuclei and 39.5 ppm for 13С
328

Chemistry of Heterocyclic Compounds 2020, 56(3), 326–330
(1H, s, H pyridine); 8.02 (1H, s, H pyridine); 9.09 (1Н, s,
129.9; 130.1; 131.4; 134.5; 135.8; 139.9; 143.1; 146.3;
149.9; 154.7. Mass spectrum, m/z: 346 [М+Н]+. Found, %:
С 73.45; Н 5.66; N 11.81. С21Н19N3O2. Calculated, %:
С 73.01; Н 5.56; N 12.17.
СН); 9.18 (1Н, s, СН) ); 13.59 (2H, s, OH). 13C NMR
spectrum, δ, ppm: 19.2; 58.9; 59.0; 116.3; 117.3; 119.4; 120.4;
120.9; 129.8; 133.8; 134.0; 138.6; 138.7; 142.3; 143.5;
148.5; 148.8; 153.3; 153.6; 159.0; 163.5. Mass spectrum, m/z:
407 [M+Н]+. Found, %: C 64.70; H 5.34; N 13.42.
C22H22N4O4. Calculated, %: C 65.00; H 5.47; N 13.79.
1-[(3-Aminophenyl)amino]-6-methyl-1,3-dihydrofuro-
[3,4-c]pyridin-7-ol (6). A mixture of 3-hydroxy-5-(hydroxy-
methyl)-2-methylpyridine-4-carbaldehyde (1) (0.25 g,
1.5 mmol), 1,3-diaminobenzene (2c) (0.16 g, 1.5 mmol),
and EtOH (20 ml) was heated under reflux for 6 h. After
cooling, the formed precipitate was separated, washed with
EtOH (50 ml), and dried. Yield 0.26 g (68%), orange
powder, mp 137–140°С. IR spectrum, ν, cm–1: 3343 (NH).
1H NMR spectrum, δ, ppm (J, Hz): 2.29 (3H, s, CH3); 5.08
(1Н, d, J = 12.0, СН2О); 5.23 (1Н, d, J = 12.0, СН2О);
5.31 (2Н, s, NH2); 5.78–6.74 (4Н, m, H Ar); 6.13 (1H, s,
СH); 7.85 (1H, s, H pyridine); 13.99 (1Н, s, OH). 13C NMR
spectrum, δ, ppm: 19.4; 71.3; 80.1; 103.6; 104.2; 107.3;
126.9; 132.3; 134.5; 135.5; 142.9; 145.2; 146.4; 149.4.
Mass spectrum, m/z: 258 [M+H]+. Found, %: C 65.12;
H 6.06; N 16.31. C14H15N3О2. Calculated, %: C 65.34;
H 5.89; N 16.33.
5-(Hydroxymethyl)-2-methyl-4-{[2-(4-nitrophenyl)-
1Н-benzimidazol-1-yl]methyl}pyridin-3-ol (10b) was
obtained by the same procedure as compound 10a from
imine 3a (0.28 g, 1.1 mmol) and 4-nitrobenzaldehyde (8b)
(0.16 g, 1.1 mmol). Yield 0.23 g (54%), white powder,
mp 243–244°С. IR spectrum, ν, cm–1: 1347, 1523 (NO2),
1
1610 (С=N), 3098 (OН). H NMR spectrum, δ, ppm
(J, Hz): 2.25 (3Н, s, CH3); 4.26 (2Н, s, СН2); 5.16 (1Н, s,
OH); 5.64 (2Н, s, CH2O); 7.16 (1Н, d, J = 7.5, H Ar); 7.21
(1Н, d, J = 7.5, H Ar); 7.32 (1Н, d, J = 8.1, H Ar); 7.71
(1Н, d, J = 7.6, H Ar); 7.90 (1Н, s, Н pyridine); 8.09 (2Н,
d, J = 8.2, H Ar); 8.37 (2Н, d, J = 8.4, H Ar); 8.88 (1Н, s,
OH). 13C NMR spectrum, δ, ppm: 20.2; 41.6; 59.2; 111.9;
120.0; 122.6; 123.3; 123.9; 128.5; 131.4; 134.3; 136.1;
137.7; 140.1; 143.1; 146.4; 148.3; 149.8; 152.6. Mass
spectrum, m/z: 391 [М+Н]+. Found, %: С 65.00; Н 4.92;
N 13.96. С21Н18N4O4. Calculated, %: С 64.60; Н 4.66;
N 14.35.
5-(Hydroxymethyl)-4-{[2-(4-hydroxyphenyl)-1Н-benz-
imidazol-1-yl]methyl}-2-methylpyridin-3-ol (10c) was
obtained by the same procedure as compound 10a from
imine 3a (0.31 g, 1.2 mmol) and 4-hydroxybenzaldehyde
(8с) (0.15 g, 1.2 mmol). Yield 0.25 g (57%), white powder,
mp 198–201°С. IR spectrum, ν, cm–1: 1611 (С=N), 3064
1-[(3-{[2-Hydroxy-6-(hydroxymethyl)-3-methylbenzyl-
idene]amino}phenyl)amino]-6-methyl-1,3-dihydrofuro-
[3,4-c]pyridin-7-ol (7) was obtained by the same
procedure as compound 4 from 3-hydroxy-5-(hydroxy-
methyl)-2-methylpyridine-4-carbaldehyde (1) (0.73 g,
4.37 mmol) and 1,3-diaminobenzene (2c) (0.24 g,
2.22 mmol). Yield 0.67 g (75%), brown powder, mp 222–
224°С. IR spectrum, cm–1: 1611 (С=N), 3332 (NН).
1H NMR spectrum, δ, ppm (J, Hz): 2.34 (3Н, s, СН3); 2.37
(3H, s, CH3); 4.74 (2Н, s, СН2О); 5.13 (1Н, d, J = 12.1,
СН2О); 5.25 (1Н, d, J = 12.1, СН2О); 5.43 (1Н, s, СН);
6.50 (1Н, d, J = 2.1, H Ar); 6.81 (1Н, d, J = 8.0, H Ar);
6.94 (1Н, d, J = 2.1, H Ar); 7.03 (1Н, d, J = 8.0, H Ar);
7.94 (1H, s, H pyridine); 7.98 (1H, s, H pyridine); 9.12
(1Н, s, СН). 13C NMR spectrum, δ, ppm: 19.2; 19.4; 58.9;
71.3; 79.8; 110.5; 112.5; 120.3; 126.9; 128.0; 132.8; 134.0;
135.0; 138.6; 145.3; 145.6; 146.3; 147.9; 148.7; 153.7;
161.2. Mass spectrum, m/z: 407 [M+Н]+. Found, %:
C 64.70; H 5.34; N 13.42. C22H22N4O4. Calculated, %:
C 65.00; H 5.47; N 13.79.
1
(OН). H NMR spectrum, δ, ppm (J, Hz): 2.31 (3Н, s,
CH3); 4.19 (2Н, s, CH2); 5.06 (1Н, s, OH); 5.54 (2Н, s,
CH2О); 6.92 (2Н, d, J = 8.2, H Ar); 7.03 (1Н, d, J = 7.3,
H Ar); 7.11 (2Н, d, J = 8.2, H Ar); 7.59 (1Н, d, J = 7.6,
H Ar); 7.64 (2Н, d, J = 8.4, H Ar); 7.92 (1Н, s, H pyridine);
9.80 (1Н, s, OH); 14.96 (1Н, s, OH). 13C NMR spectrum,
δ, ppm: 20.3; 41.6; 59.1; 111.4; 115.7; 119.2; 121.7; 121.9;
122.1; 122.2; 128.6 (2C); 131.6; 134.6; 135.6; 139.6;
143.0; 146.2; 149.9; 155.0; 159.1. Mass spectrum, m/z: 362
[М+Н]+. Found, %: C 69.71; H 5.71; N 11.43. C21H19N3O3.
Calculated, %: C 69.78; H 5.59; N 11.63.
5-(Hydroxymethyl)-4-{[2-(2-hydroxyphenyl)-1Н-benz-
imidazol-1-yl]methyl}-2-methylpyridin-3-ol (10d) was
obtained by the same procedure as compound 10a from
imine 3a (0.12 g, 0.5 mmol) and 2-hydroxybenzaldehyde
(8d) (0.06 g, 0.5 mmol). Yield 0.06 g (35%), white powder,
mp 247–248°С. IR spectrum, ν, cm–1: 1613 (С=N), 3052
5-(Hydroxymethyl)-2-methyl-4-[(2-phenyl-1Н-benz-
imidazol-1-yl)methyl]pyridin-3-ol (10a). A mixture of
imine 3a (0.4 g, 1.6 mmol) and benzaldehyde (8а) (0.16 g,
1.6 mmol) in EtOH (10 ml) was heated under reflux with
stirring for 4 h. After cooling, the formed precipitate was
filtered off, washed with EtOH (40 ml), Et2O (20 ml), and
dried. Yield 0.18 g (33%), white powder, mp 224–226°С.
1
(OН). H NMR spectrum, δ, ppm (J, Hz): 2.30 (3Н, s,
CH3); 4.21 (2Н, s, CH2); 5.11 (1Н, s, OH); 5.42 (2Н, s,
CH2О); 6.94 (1Н, t, J = 7.5, H Ar); 6.98–7.09 (2Н, m,
H Ar); 7.14 (1Н, t, J = 7.7, H Ar); 7.29–7.40 (2Н, m,
H Ar); 7.50 (1Н, dd, J = 7.6, J = 1.6, H Ar); 7.62 (1Н, d,
J = 7.9, H Ar); 7.88 (1Н, s, H pyridine); 9.05 (1Н, s, OH);
10.40 (1Н, s, OH). 13C NMR spectrum, δ, ppm: 20.3; 41.4;
59.1; 111.4; 116.5; 117.9; 119.3; 119.5; 121.9; 122.4;
128.6; 131.7; 131.9; 134.7; 135.3; 139.8; 142.9; 146.3;
150.0; 153.2; 156.5. Mass spectrum, m/z: 362 [М+Н]+.
Found, %: C 69.42; H 6.01; N 11.54. C21H19N3O3.
Calculated, %: C 69.78; H 5.59; N 11.63.
1
IR spectrum, ν, cm–1: 1619 (С=N), 3183 (ОН). H NMR
spectrum, δ, ppm (J, Hz): 2.30 (3Н, s, СН3); 4.26 (2Н, d,
J = 4.1, CH2); 5.18 (1Н, s, OH); 5.58 (2Н, s, CH2O); 7.08
(1Н, t, J = 7.2, Ph); 7.17 (2H, dd, J = 14.0, J = 7.8, H Ph);
7.55 (3H, dd, J = 5.1, J = 1.8, H Ph); 7.65 (1H, d, J = 7.9,
H Ph); 7.82 (2H, dd, J = 6.5, J = 3.0, H Ph); 7.92 (1Н, s,
H pyridine); 8.91 (1Н, s, OH). 13C NMR spectrum, δ, ppm:
20.3; 41.6; 59.2; 111.6; 119.6; 122.1; 122.5; 128.5; 128.9;
1-[(3-{[(2-Hydroxyphenyl)methylidene]amino}phenyl)-
amino]-6-methyl-1,3-dihydrofuro[3,4-c]pyridin-7-ol (12)
329

Chemistry of Heterocyclic Compounds 2020, 56(3), 326–330
was obtained by the same procedure as compound 4 from
9. Sadeghi, S.; Gafarzadeh, A.; Naeimi, H. J. Anal. Chem. 2006, 61, 677.
10. Cupta, K. C.; Sutar, A. K. J. Mol. Catal. A: Chem. 2007,
272, 64.
furopyridine 6 (0.3 g, 1.165 mmol) and 2-hydroxybenz-
aldehyde (8d) (0.14 g, 1.165 mmol). Yield 0.22 g (52%),
orange powder, mp 285–286°С. IR spectrum, ν, cm–1: 1613
11. Naskar, S.; Naskar, S.; Butcher, R. J.; Chattopadhyay, S. K.
Inorg. Chim. Acta 2010, 363, 404.
1
(С=N), 3042 (NН). H NMR spectrum, δ, ppm (J, Hz):
12. Matsushima, Y. Chem. Pharm. Bull. 1968, 16, 2143.
13. Iwanami, M.; Numata, T.; Murakami, M. Bull. Chem. Soc.
Jpn. 1968, 41, 161.
2.37 (3Н, s, СН3); 5.13 (1Н, d, J = 12.1, СН2О); 5.25 (1Н,
d, J = 12.1, СН2О); 6.62 (1Н, s, СН=N); 7.00–7.05 (3Н, m,
H Ar); 7.27 (1Н, s, H Ar); 7.43 (2Н, s, H Ar); 7.67 (1Н, s,
H Ar); 7.75 (1H, s, H Ar); 8.00 (1H, s, H pyridine); 8.99
(1Н, s, ОСНN); 12.50 (1Н, s, OH); 12.95 (1Н, s, OH).
13C NMR spectrum, δ, ppm: 19.5; 71.1; 79.7; 112.4; 117.2;
119.8; 120.2; 128.7; 132.3; 133.1; 134.0; 134.2; 135.1;
135.7; 145.7; 146.3; 148.9; 149.6; 160.6; 164.4. Mass
spectrum, m/z: 362 [M+Н]+. Found, %: C 69.71; H 5.71;
N 11.43. C21H19N3O3. Calculated, %: C 69.78; H 5.59;
N 11.63.
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The authors are grateful to the Collective Spectro-
Analytical Center for Physico-Chemical Studies of the
Structure, Properties, and Composition of Substances and
Materials of the Kazan Research Center of the Russian
Academy of Sciences for the technical support.
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