Synthesis of Novel Tetrahydropyrimido[4,5-B][1,6]Naphthyridines via Condensation of 1-benzyl-3,5-bis[(E)-arylmethylidene]tetrahydropyridin-4(1H)-ones with 6-aminouracils

Article abstract of DOI:10.1007/s10593-020-02840-z

[Figure not available: see fulltext.] The successful synthesis of novel tetrahydropyrimido[4,5-b][1,6]naphthyridine derivatives is reported. 1-Benzyl-3,5-bis[(E)-arylmethylidene] tetrahydropyridin-4(1H)-ones prepared via Knoevenagel condensation of 1-benz

Full text of DOI:10.1007/s10593-020-02840-z

DOI 10.1007/s10593-020-02840-z
Chemistry of Heterocyclic Compounds 2020, 56(11), 1473–1476
Synthesis of novel tetrahydropyrimido[4,5-b][1,6]naphthyridines
via condensation of 1-benzyl-3,5-bis[(E)-arylmethylidene]tetrahydro-
pyridin-4(1H)-ones with 6-aminouracils
Mehdi Ghandi1*, Rasoul Rashid1, Alireza Abbasi1
1 School of Chemistry, College of Science, University of Tehran,
Enghelab St., Tehran, Iran; e-mail: ghandi@khayam.ut.ac.ir
Published in Khimiya Geterotsiklicheskikh Soedinenii,
2020, 56(11), 1473–1476
Submitted February 4, 2020
Accepted after revision June 5, 2020
The successful synthesis of novel tetrahydropyrimido[4,5-b][1,6]naphthyridine derivatives is reported. 1-Benzyl-3,5-bis[(E)-aryl-
methylidene]tetrahydropyridin-4(1H)-ones prepared via Knoevenagel condensation of 1-benzyl-4-piperidinone with aromatic aldehydes
undergo condensation with 6-aminouracils in acetic acid to afford the desired products. Structures of the products are confirmed by
analytical data and X-ray crystallography analysis.
Keywords: 6-aminouracils, 1-benzyl-4-piperidinone, 1,6-naphthyridines.
Synthesis of naphthyridine derivatives are of a particular
interest due to its diverse biological activity.1 The functio-
nalized 1,6-naphthyridines are known to exhibit various
types of biological properties including antibacterial,2
anticonvulsant,3 anti-human cytomegalovirus,4 anticancer,5
antiviral, antiretroviral,6 and antiproliferative activities.
On the other hand, during the past decade, dihydro-
pyrimidines have become an increasingly active area of
research because of their anticarcinogenic,7 antimicrobial,8
and acetyl cholinesterase inhibitory9 activities.
Known methods used for the synthesis of 1,6-naphthy-
ridines include cyclization of tosylhydrazine, carbonyl
compounds, and 2-alkynyl-3-formylquinolines,10 Mitsunobu
reaction with glycine derivatives followed by a Dieckmann
cyclization in the presence of sodium methoxide,11 inverse
electron demand Diels–Alder reaction between 3,5-dinitro-
N-methylpyridone and piperidone,12 and tandem reaction of
isoquinoline, dialkyl acetylenedicarboxylates, and 3-chloro-
pentane-2,4-dione or alkyl 3-chloroacetoacetates.13
In 2013, a two-component reaction of bischalcones 1a–d
with 6-amino-1,3-dimethyluracil (2a) for the synthesis of
pyrimidine monoadducts 3a–d was described.14 Compounds
3a–d displayed cytotoxic activity with a massive vacuo-
lation in different human cell lines in vitro (Scheme 1).14
These results prompted us to investigate the two-compo-
nent reaction of 1-benzyl-3,5-bis[(E)-arylmethylidene]-
tetrahydropyridin-4(1H)-ones 4a–f with 6-aminouracils
2a,b since these reactions could afford the formation of
fused heterocyclic compounds 5a–k encompassing both
1,6-naphthyridine and tetrahydropyrimidine motifs with
Scheme 1
0009-3122/20/56(11)-1473©2020 Springer Science+Business Media, LLC
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Chemistry of Heterocyclic Compounds 2020, 56(11), 1473–1476
Scheme 2
individual biological activities (Scheme 2). It should be
noted that the synthesis of uracil derivatives is of great
importance due to their potential activity as antiviral and
anticancer agents.15
Initially, 1-benzyl-3,5-bis[(E)-arylmethylidene]tetrahydro-
pyridin-4(1H)-one derivatives 4a–f were prepared via
Knoevenagel condensation of 1-benzyl-4-piperidinone with
aromatic aldehydes using the previously reported synthetic
procedure (Scheme 2).16
Adducts 4a–f were subsequently treated with 6-amino-
uracil 2a,b in AcOH and heated at reflux to afford the
desired products 5a–k (Scheme 2, Table 1). We assume
that the formation of tetrahydropyrimido[4,5-b][1,6]-
naphthyridine derivatives 5a–k can be explained by the
attack of the NH2 group to the most reactive carbonyl
functionality in compounds 4a–f, which in the acidic
conditions resulted in the formation of intermediate A
(Scheme 2).16 Subsequent 6π-electron cyclization reaction
allows to obtain dihydropyrimidinedione intermediates B
that under air oxidation process afford products 5a–k.
The structures of products 5a–k were established by
elemental analysis, MS, IR, and 1H and 13C NMR
spectroscopy. Unambiguous evidence for the structure of
compound 5g was obtained by single crystal X-ray
diffraction analysis (Fig. 1).
Table 1. Yields of tetrahydropyrimido[4,5-b][1,6]-
naphthyridines 5a–k
Adduct
4a
R
H
6-Aminouracil
R1
Me
H
Time, h Product Yield, %
15
16
18
15
20
15
16
18
18
17
15
79
86
84
75
87
81
85
92
81
78
72
2a
2b
2a
2b
2a
2b
2a
2b
2a
2b
2a
5a
5b
5c
5d
5e
5f
H
4a
4-Cl
4-Cl
4-Me
4-Me
4-OMe
4-OMe
2-Cl
2-Cl
4-Br
Me
H
4b
4b
4c
Me
H
4c
Me
H
4d
4d
4e
5g
5h
5i
Me
H
4e
5j
Me
4f
5k
In conclusion, the initially prepared 1-benzyl-3,5-bis-
[(E)-arylmethylidene]tetrahydropyridin-4(1H)-one derivative
underwent reaction with 6-aminouracils in acetic acid to
afford the tetrahydropyrimido[4,5-b][1,6]naphthyridines in
high yields. These novel structures broaden the scope of
hybrid scaffolds obtained from the two-component reaction
and many of them may be valuable for medicinal chemistry
studies in the future.
Experimental
IR spectra were recorded on a Bomem B100 series
spectrophotometer in KBr pellets. 1H and 13C NMR spectra
were recorded on a Bruker Avance DRX-500 spectrometer
(500 and 125 MHz, respectively) in DMSO-d6. Solvent
signals were used as internal standard (2.50 ppm for
1H nuclei and 39.5 ppm for 13C nuclei). Mass spectra were
recorded on an Agilent Technologies 5937 Series Mass
Selective Detector. Elemental analyses were carried out by
a Heraeus CHN-O-Rapid automatic elemental analyzer
with TCD detection. Melting points were determined with
an Electrothermal model 9100 apparatus and are uncorrected.
All commercially available chemicals and reagents were
purchased from Merck Chemical Company and used
without further purification.
Figure 1. Molecular structure of compound 5g with atoms repre-
sented as thermal vibration ellipsoids of 50% probability.
1474

Chemistry of Heterocyclic Compounds 2020, 56(11), 1473–1476
1-Benzyl-3,5-bis[(E)-arylmethylidene]tetrahydropyridin-
mp 230–233°C. IR spectrum, ν, cm–1: 3140, 3034, 2825, 1698,
1
4(1H)-one derivatives 4a–f were obtained by adapting
1559. H NMR spectrum, δ, ppm: 3.17 (2H, s, PhCH2);
previously reported procedure.16
3.30 (2H, s, NCH2); 3.68 (2H, s, NCH2); 7.07–7.17 (7H, m,
H Ar); 7.30–7.42 (6H, m, H Ar); 7.98 (1H, s, =CH); 11.09
(1H, s, NH); 11.52 (1H, s, NH). 13C NMR spectrum,
δ, ppm: 52.4; 52.8; 60.4; 106.9; 124.9; 127.5; 128.3; 128.5;
128.8; 129.1; 129.3; 129.6; 131.6; 132.5; 133.0; 133.2;
136.0; 136.9; 138.0; 150.0; 150.6; 151.5; 154.2; 161.8.
Mass spectrum, m/z (Irel, %): 541 [M]+ (28), 540 (52), 449 (34),
415 (18), 91 (100). Found, %: C 66.45; H 4.13; N 10.42.
C30H22Cl2N4O2. Calculated, %: C 66.55; H 4.10; N 10.35.
(E)-7-Benzyl-1,3-dimethyl-9-(4-methylbenzylidene)-
5-(p-tolyl)-6,7,8,9-tetrahydropyrimido[4,5-b][1,6]-
naphthyridine-2,4(1H,3H)-dione (5e). Yield 0.485 g (92%),
yellow solid, mp 205–208°C. IR spectrum, ν, cm–1: 2942,
Synthesis of compounds 5a–k (General method).
6-Aminouracil 2a,b (1.0 mmol) was added to a stirring
solution of 1-benzyl-3,5-bis[(E)-arylmethylidene]tetrahydro-
pyridin-4(1H)-one derivative 4a–f (1.0 mmol) in AcOH
(3 ml). The mixture was heated at reflux for the appropriate
time (see Table 1). After completion of the reaction
indicated by TLC, saturated 10% aq solution of NaHCO3
(10 ml) was added and the mixture was extracted with
EtOAc (15 ml). The organic phase was dried over Na2SO4,
the solvent was evaporated under reduced pressure, and the
residue was purified by column chromatography (SiO2,
eluent n-hexane–EtOAc, 3:1).
1
(E)-7-Benzyl-9-benzylidene-1,3-dimethyl-5-phenyl-
6,7,8,9-tetrahydropyrimido[4,5-b][1,6]naphthyridine-
2,4(1H,3H)-dione (5a). Yield 0.395 g (79%), yellow solid,
mp 212–213°C. IR spectrum, ν, cm–1: 2798, 1701, 1654.
1H NMR spectrum, δ, ppm: 3.10 (3H, s, CH3); 3.16 (2H, s,
PhCH2); 3.47 (2H, s, NCH2); 3.67 (3H, s, CH3); 3.72 (2H,
s, NCH2); 7.01–7.14 (7H, m, H Ar); 7.30 (4H, s, H Ar);
7.36 (4H, s, H Ar); 8.10 (1H, s, =CH). 13C NMR spectrum,
δ, ppm: 28.3; 30.0; 52.5; 53.1; 60.6; 107.0; 125.0; 127.3;
127.4; 127.6; 128.3; 128.4; 128.9; 129.2; 130.1; 130.5
(2C); 132.5; 136.2; 137.4; 137.9; 149.6; 151.3; 151.7;
153.7; 160.1. Mass spectrum, m/z (Irel, %): 501 [M]+ (82),
409 (100), 91 (98). Found, %: C 76.80; H 5.67; N 11.28.
C32H28N4O2. Calculated, %: C 76.78; H 5.64; N 11.19.
(E)-7-Benzyl-9-benzylidene-5-phenyl-6,7,8,9-tetra-
hydropyrimido[4,5-b][1,6]naphthyridine-2,4(1H,3H)-dione
(5b). Yield 0.406 g (86%), yellow solid, mp 227–230°C.
IR spectrum, ν, cm–1: 3193, 3053, 2812, 1695, 1551. 1H NMR
spectrum, δ, ppm: 3.18 (2H, s, PhCH2); 3.49 (2H, s, NCH2);
3.72 (2H, s, NCH2); 7.04–7.17 (9H, m, H Ar); 7.31–7.41 (6H,
m, H Ar); 8.01 (1H, s, =CH); 11.04 (1H, s, NH); 11.50
(1H, s, NH). 13C NMR spectrum, δ, ppm: 52.6; 53.1; 60.7;
106.7; 124.9; 127.4; 127.5; 127.7; 128.2; 128.4; 129.1;
129.2; 129.9, 130.1; 132.6; 136.2; 137.1; 137.9; 150.7;
151.3; 151.5; 154.4; 161.7. Mass spectrum, m/z (Irel, %):
472 [M]+ (15), 381 (40), 304 (20), 227 (17), 169 (10), 91
(100). Found, %: C 76.18; H 5.17; N 11.88. C30H24N4O2.
Calculated, %: C 76.25; H 5.12; N 11.86.
1702, 1654. H NMR spectrum, δ, ppm (J, Hz): 2.28 (3H,
s, 4-CH3 Ar); 2.32 (3H, s, 4-CH3 Ar); 3.09 (3H, s, CH3);
3.16 (2H, s, PhCH2); 3.60 (2H, s, NCH2); 3.64 (3H, s,
3
CH3); 3.68 (2H, s, NCH2); 6.87 (2H, d, J = 7.7, H Ar);
7.06–7.16 (9H, m, H Ar); 7.22 (2H, d, 3J = 7.9, H Ar); 8.03
(1H, s, =CH). 13C NMR spectrum, δ, ppm: 21.3 (2C); 28.3;
29.9; 52.6; 53.2; 60.7; 106.9; 125.1; 127.3; 127.4; 128.4;
128.9; 129.1; 129.5; 130.2; 130.5; 131.7; 133.4; 134.5;
136.7; 138.0; 138.1; 149.6; 151.3; 151.8; 153.8; 160.1.
Mass spectrum, m/z (Irel, %): 529 [M]+ (78), 438 (100), 424
(31), 91 (67). Found, %: C 77.35; H 6.05; N 10.68.
C34H32N4O2. Calculated, %: C 77.25; H 6.10; N 10.60.
(E)-7-Benzyl-9-(4-methylbenzylidene)-5-(p-tolyl)-
6,7,8,9-tetrahydropyrimido[4,5-b][1,6]naphthyridine-
2,4(1H,3H)-dione (5f). Yield 0.436 g (87%), yellow solid,
mp 220–222°C. IR spectrum, ν, cm–1: 3162, 3025, 2804,
1
1703, 1551. H NMR spectrum, δ, ppm (J, Hz): 2.31 (3H,
s, 4-CH3 Ar); 2.33 (3H, s, 4-CH3 Ar); 3.19 (2H, s, PhCH2);
3.51 (2H, s, NCH2); 3.71 (2H, s, NCH2); 6.93 (2H, d, 3J = 8.5,
H Ar); 7.09–7.21 (11H, m, H Ar); 8.02 (1H, s, =CH); 11.01
13
(1H, s, NH); 11.45 (1H, s, NH). C NMR spectrum, δ, ppm:
21.3 (2C); 52.7; 53.2; 60.7; 106.6; 125.0; 127.4; 127.5; 128.4;
128.8; 129.2; 129.7; 129.9; 130.0; 130.1; 131.7; 133.4; 134.1;
136.7; 138.0; 150.7; 151.4; 151.5; 154.5; 161.7. Mass
spectrum, m/z (Irel, %): 501 [M]+ (20), 500 (60), 409 (35),
317 (10), 91 (100). Found, %: C 76.74; H 5.70; N 10.99.
C32H28N4O2. Calculated, %: C 76.78; H 5.64; N 11.19.
(E)-7-Benzyl-9-(4-methoxybenzylidene)-5-(4-methoxy-
phenyl)-1,3-dimethyl-6,7,8,9-tetrahydropyrimido[4,5-b]-
[1,6]naphthyridine-2,4(1H,3H)-dione (5g). Yield 0.476 g
(85%), yellow solid, mp 215–217°C. IR spectrum, ν, cm–1:
(E)-7-Benzyl-9-(4-chlorobenzylidene)-5-(4-chlorophenyl)-
1,3-dimethyl-6,7,8,9-tetrahydropyrimido[4,5-b][1,6]-
naphthyridine-2,4(1H,3H)-dione (5c). Yield 0.394 g (84%),
yellow solid, mp 213–216°C. IR spectrum, ν, cm–1: 2801,
1
2953, 1708, 1660, 1605. H NMR spectrum, δ, ppm (J, Hz):
1
1703, 1651, 1554. H NMR spectrum, δ, ppm: 3.13 (3H, s,
3.09 (3H, s, CH3); 3.17 (2H, s, PhCH2); 3.47 (2H, s,
NCH2); 3.63 (3H, s, CH3); 3.68 (2H, s, NCH2); 3.75 (3H, s,
OCH3); 3.76 (3H, s, OCH3); 6.82–6.92 (6H, m, H Ar); 7.04–
7.20 (5H, m, H Ar); 7.27 (2H, d, 3J = 8.8, H Ar); 8.01 (1H,
s, =CH). 13C NMR spectrum, δ, ppm: 52.6; 53.8; 55.4 (2C);
55.6 (2C); 60.8; 106.8; 113.7; 114.4; 125.0; 127.4; 128.4;
128.7 (2C); 129.2; 129.4; 130.3; 130.5; 132.9; 138.0; 149.6;
151.3; 151.4; 154.0; 158.9; 159.5; 160.1. Mass spectrum,
m/z (Irel, %): 561 [M]+ (81), 470 (85), 454 (26), 440 (37),
91 (100). Found, %: C 72.60; H 5.90; N 10.10.
C34H32N4O4. Calculated, %: C 72.84; H 5.75; N 9.99.
CH3); 3.19 (2H, s, PhCH2); 3.52 (2H, s, NCH2); 3.68 (3H,
s, CH3); 3.72 (2H, s, NCH2); 7.04–7.12 (4H, m, H Ar); 7.15–
7.22 (3H, m, H Ar); 7.38–7.44 (6H, m, H Ar); 8.07 (1H, s,
=CH). 13C NMR spectrum, δ, ppm: 28.4; 30.0; 52.3; 52.8;
60.4; 107.2; 125.0; 127.5; 128.4; 128.5 (2C); 128.9; 129.2,
129.3; 131.9; 132.5; 133.0; 133.1; 135.1; 136.3; 137.9; 149.6;
150.4; 151.3; 153.6; 160.2. Mass spectrum, m/z (Irel, %):
569 [M]+ (4), 568 (9), 477 (25), 443 (17), 91 (100). Found, %:
C 67.42; H 4.71; N 9.80. C32H26Cl2N4O2. Calculated, %:
C 67.49; H 4.60; N 9.84.
(E)-7-Benzyl-9-(4-chlorobenzylidene)-5-(4-chlorophenyl)-
6,7,8,9-tetrahydropyrimido[4,5-b][1,6]naphthyridine-
2,4(1H,3H)-dione (5d). Yield 0.405 g (75%), yellow solid,
(E)-7-Benzyl-9-(4-methoxybenzylidene)-5-(4-methoxy-
phenyl)-6,7,8,9-tetrahydropyrimido[4,5-b][1,6]naph-
thyridine-2,4(1H,3H)-dione (5h). Yield 0.430 g (81%),
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Chemistry of Heterocyclic Compounds 2020, 56(11), 1473–1476
yellow solid, mp 238–240°C. IR spectrum, ν, cm–1: 3161,
mar345 Image Plate Detector System (MoKα radiation,
λ 0.71073 Å, 295 K). The structure was solved by direct
methods using SHELXS-97 and the obtained model refined
with SHELXL-2014.17 All non-hydrogen atoms were
refined anisotropically. Hydrogen atoms were placed at
calculated positions and refined using the "rider" model.
Full crystallographic data is deposited at the Cambridge
Crystallographic Data Center (deposit CCDC 1941896).
1
3031, 2831, 1689, 1553. H NMR spectrum, δ, ppm (J, Hz):
3.19 (2H, s, PhCH2); 3.30 (2H, s, NCH2); 3.49 (2H, s,
NCH2); 3.75 (3H, s, OCH3); 3.76 (3H, s, OCH3); 6.84–6.97
(6H, m, H Ar); 7.10–7.19 (5H, m, H Ar); 7.27 (2H, d, 3J = 8.8,
H Ar); 7.98 (1H, s, =CH); 10.97 (1H, s, NH); 11.40 (1H, s,
NH). 13C NMR spectrum, δ, ppm: 52.7; 53.4; 55.4; 55.6;
60.8; 106.5; 113.6; 114.6; 125.0; 127.4; 128.5; 128.7; 129.0;
129.2; 129.9; 130.6; 131.6; 131.7; 138.0; 150.6; 151.0; 151.5;
154.7; 158.9; 159.5; 161.7. Mass spectrum, m/z (Irel, %):
532 [M]+ (17), 441 (38), 334 (25), 227 (22), 169 (8), 91
(100). Found, %: C 72.08; H 5.37; N 10.55. C32H28N4O4.
Calculated, %: C 72.17; H 5.30; N 10.52.
Supplementary information file containing 1H and
13C NMR spectra of compounds 5a–k is available at the
journal website at http://link.springer.com/journal/10593.
(E)-7-Benzyl-9-(2-chlorobenzylidene)-5-(2-chlorophenyl)-
1,3-dimethyl-6,7,8,9-tetrahydropyrimido[4,5-b][1,6]-
naphthyridine-2,4(1H,3H)-dione (5i).Yield 0.467 g (81%),
yellow solid, mp 208–210°C. IR spectrum, ν, cm–1: 3065,
The authors acknowledge the University of Tehran for
financial support of this research.
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1705, 1663, 1555. H NMR spectrum, δ, ppm (J, Hz): 3.13–
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3.21 (5H, m, CH3, PhCH2); 3.44–3.63 (7H, m, CH3, 2NCH2);
6.97–7.18 (6H, m, H Ar); 7.23–7.37 (5H, m, H Ar); 7.44
3
3
(1H, d, J = 8.1, H Ar); 7.52 (1H, d, J = 7.7, H Ar); 8.21
(1H, s, =CH). 13C NMR spectrum, δ, ppm: 28.4; 29.9; 52.0;
52.2; 60.0; 107.6; 116.0 (2C); 124.9; 127.4 (2C); 127.5;
127.6; 128.4; 129.0; 129.1; 129.3; 129.8; 129.9; 130.2;
130.8; 131.1; 133.7; 133.9; 134.2; 136.2; 137.8; 148.8;
149.7; 151.2; 153.7; 160.0. Mass spectrum, m/z (Irel, %):
570 [M]+ (30), 568 (40), 534 (15), 477 (13), 441 (45), 91
(100). Found, %: C 67.49; H 4.65; N 9.79. C32H26Cl2N4O.
Calculated, %: C 67.49; H 4.60; N 9.84.
(E)-7-Benzyl-9-(2-chlorobenzylidene)-5-(2-chlorophenyl)-
6,7,8,9-tetrahydropyrimido[4,5-b][1,6]naphthyridine-
2,4(1H,3H)-dione (5j). Yield 0.422 g (78%), yellow solid,
mp 233–235°C. IR spectrum, ν, cm–1: 3175, 3051, 2834,
1
1688, 1566. H NMR spectrum, δ, ppm (J, Hz): 3.10 (1H,
3
3
d, J = 15.6, PhCH); 3.21 (1H, d, J = 15.6, PhCH); 3.43–
3.58 (4H, m, 2NCH2); 7.05–7.53 (13H, m, H Ar); 8.13 (1H,
s, =CH); 11.15 (1H, s, NH); 11.63 (1H, s, NH). 13C NMR
spectrum, δ, ppm: 52.2; 52.4; 60.0; 107.3; 124.7; 127.4;
128.4; 129.0; 129.1; 129.2; 129.8; 129.9; 130.2; 130.9;
131.2; 133.7; 134.4; 135.9; 136.3; 137.8; 148.3; 150.6;
151.5; 154.3; 161.5. Mass spectrum, m/z (Irel, %): 541 [M]+
(20), 540 (53), 506 (22), 449 (21), 415 (27), 91 (100).
Found, %: C 66.47; H 4.22; N 10.56. C30H22Cl2N4O2.
Calculated, %: C 66.55; H 4.10; N 10.35.
(E)-7-Benzyl-9-(4-bromobenzylidene)-5-(4-bromophenyl)-
1,3-dimethyl-6,7,8,9-tetrahydropyrimido[4,5-b][1,6]-
naphthyridine-2,4(1H,3H)-dione (5k). Yield 0.472 g (72%),
yellow solid, mp 238–239°C. IR spectrum, ν, cm–1: 2932,
2084, 1700, 1650. 1H NMR spectrum, δ, ppm (J, Hz): 3.09
(3H, s, CH3); 3.16 (2H, s, PhCH2); 3.44 (2H, s, NCH2); 3.63
(3H, s, CH3); 3.68 (2H, s, NCH2); 6.87 (2H, d, 3J = 7.7, H Ar);
7.05–7.16 (9H, m, H Ar); 7.22 (2H, d, 3J = 7.9, H Ar); 8.03
(1H, s, =CH). 13C NMR spectrum, δ, ppm: 28.3; 29.0; 52.3;
52.8; 60.0; 106.0; 115.5; 124.5; 126.0; 128.4; 128.5; 128.9;
129.0; 129.3; 132.1; 132.5; 133.0; 134.0; 135.7; 136.3;
137.8; 150.0; 150.6; 152.7; 153.4; 161.0. Mass spectrum,
m/z (Irel, %): 658 [M]+ (26), 656 (23), 567 (31), 487 (14),
91 (100). Found, %: C 58.36; H 3.96; N 8.57. C32H26Br2N4O2.
Calculated, %: C 58.38; H 3.98; N 8.51.
15. Sacarescu, L.; Atudosie, I.; Simionescu, M.; Sacarescu, G.;
Harabagiu, V. Chem. Heterocycl. Compd. 2011, 47, 497.
[Khim. Geterotsikl. Soedin. 2011, 602.]
16. Han, Z.-G.; Tu, S.-J.; Jiang, B.; Yan, S.; Zhang, X.-H.; Wu, S.-S.;
Hao, W.-J.; Cao, X.-D.; Shi, F.; Zhang, G.; Ma, N. Synthesis
2009, 1639.
17. (a) Sheldrick, G. M. Acta Crystallogr., Sect. A: Found.
Crystallogr. 2008, A64, 112. (b) Sheldrick, G. M. SADABS;
University of Göttingen, 1996. (c) Sheldrick, G. M. Acta
Crystallogr, Sect. A: Found. Adv. 2015, A71, 3.
X-ray structural study of compound 5g was per-
formed on a MARresearch diffractometer equipped with
1476