Studies on the chemical reactivity of 1H-benzimidazol-2-ylacetonitrile towards some 3-substituted chromones: Synthesis of some novel pyrido[1,2-a]benzimidazoles

Article abstract of DOI:10.1016/j.tet.2013.06.011

A simple and convenient synthesis of a novel series of pyrido[1,2-a] benzimidazoles was efficiently achieved from the condensation reactions of 1H-benzimidazol-2-ylacetonitrile (1) with some 3-substituted chromones, chromone-3-carboxylic acids, chromone-3-carboxamides, ethyl chromone-3- carboxylates and chromone-3-carbonitriles. Reaction of compound 1 with 2-aminochromone-3-carboxaldehydes produced 2-amino-3-(1H-benzimidazol-2-yl) chromeno[2,3-b]pyridines. The reaction mechanisms and spectral data were also discussed.

Full text of DOI:10.1016/j.tet.2013.06.011

Tetrahedron 69 (2013) 6861e6865
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Tetrahedron
journal homepage: www.elsevier.com/locate/tet
Studies on the chemical reactivity of 1H-benzimidazol-2-
ylacetonitrile towards some 3-substituted chromones: synthesis
of some novel pyrido[1,2-a]benzimidazoles
*
Magdy A. Ibrahim
Department of Chemistry, Faculty of Education, Ain Shams University, Roxy, 11711 Cairo, Egypt
a r t i c l e i n f o
a b s t r a c t
Article history:
A simple and convenient synthesis of a novel series of pyrido[1,2-a]benzimidazoles was efficiently
achieved from the condensation reactions of 1H-benzimidazol-2-ylacetonitrile (1) with some 3-
substituted chromones, chromone-3-carboxylic acids, chromone-3-carboxamides, ethyl chromone-3-
Received 11 March 2013
Received in revised form 24 May 2013
Accepted 3 June 2013
carboxylates and chromone-3-carbonitriles. Reaction of compound
1 with 2-aminochromone-3-
Available online 11 June 2013
carboxaldehydes produced 2-amino-3-(1H-benzimidazol-2-yl)chromeno[2,3-b]pyridines. The reaction
mechanisms and spectral data were also discussed.
Keywords:
Ó 2013 Elsevier Ltd. All rights reserved.
3-Substituted chromones
1H-Benzimidazol-2-ylacetonitrile
Pyrido[1,2-a]benzimidazole
RORC reactions
Michael addition
1. Introduction
2. Results and discussion
Chromones are widely distributed in nature and are a well
studied class of organic compounds.1e4 The chemical reactivity of
3-substituted chromones towards nucleophilic reagents is widely
different depending on the nature of substituents at position 3 and
reaction conditions. The introduction of an electron-withdrawing
group; COOH, COOEt, CONH2 and CN at position 3 of the chro-
The present work aimed to study the chemical behaviour of 1H-
benzimidazol-2-ylacetonitrile (1) towards a variety of 3-substituted
chromones. Thus, treatment of chromone-3-carboxylic acids 2a,b13
with compound 1, in boiling ethanol containing few drops of trie-
thylamine as a basic catalyst, afforded the novel pyrido[1,2-a]
benzimidazole-4-carbonitriles (3a,b). The reaction proceeds via
deprotonation of compound 1 to produce carbanion A, which un-
derwent 1,4-Michael addition at C-2 position in carboxylic acids 2 to
produce intermediates B. Intermediates B undergo retro-Michael
mone system changes the reactivity of the g-pyrone ring with re-
spect to nucleophiles, and provides a broad synthetic potential of 3-
substituted chromones.5e11 The diversity of properties of these
compounds is due to the fact that, are highly reactive geminally
addition with
g-pyrone ring opening, generating intermediates C,
activated pushepull alkenes (
leaving group at the -carbon atom. 3-Substituted chromones have
the ability to undergo a nucleophilic 1,4-addition at position 2
followed by further transformations related to -pyrone ring
opening and heterocyclizations at the C-4 atom and/or at the
substituent in position 3. The reaction of 1H-benzimidazol-2-
ylacetonitrile (1) with some 3-formylchromones gave 4-cyano-2-
(2-hydroxybenzoyl)pyrido[1,2-a]benzimidazoles as previously
published.12
a
,
b
-unsaturated ketones) with a good
with concomitant decarboxylation to give a,b
-unsaturated ketones
b
D.10 The latter intermediates D underwent intramolecular de-
hydration giving rise the final products 3a,b; presumption through
reactive intermediates E as illustrated in Scheme 1. The structures of
compounds 3a,b were further deduced from their authentic syn-
thesis via reaction of 1H-benzimidazol-2-ylacetonitrile (1) with
chromone 4a and 6-methylchromone 4b, respectively. The latter
reactions confirm the decarboxylation of compounds 2a,b during
the course of reactions.10 The structures of compounds 3a,b were
deduced from their elemental analysis and spectral data. The IR
spectra of compounds 3a and 3b showed characteristic absorption
bands attributed to the nitrile functions at 2231 cmꢀ1. The mass
spectra of compounds 3a and 3b showed the molecular ion peaks, as
the base peaks at m/z 285 and 299, which is coincident with the
g
* Tel.: þ20 1007887204; fax: þ20 22581243; e-mail address: magdy_ahmed1977@
yahoo.com.
0040-4020/$ e see front matter Ó 2013 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.tet.2013.06.011

6862
M.A. Ibrahim / Tetrahedron 69 (2013) 6861e6865
O
H
N
N
HOOC
R
EtOH/TEA
-H+
+
N
H
N
A
O
CN
CN
2
1
a; R = H
b; R = CH
3
R
HOOC
O
N
O
O
-CO
2
:
N
COOH
N
H
O
R
CN
B
N
H
CN
C
R
R
HO
O
N
O
O
:
N
N
H
E
N
H
CN
CN
+H+
3a; 64%
3b; 65%
D
-H O
2
R
O
OH
N
R
N
EtOH/TEA
+
N
H
3a; 61%
3b; 63%
N
O
CN
CN
1
3
4
a; R = H
a; R = H
b; R = CH
b; R = CH
3
3
Scheme 1. Reactions of compound 1 with chromone-3-carboxylic acids 2a,b and chromones 4a,b.
formula weights and support the identity of the structures. Fur-
showed characteristic absorption bands at 2235/2231 and 1670/
1680 cmꢀ1, attributed to the C^N and C]Opyridone functions, re-
spectively. The 1H NMR spectra showed characteristic singlets at
thermore, the 13C NMR spectrum of compound 3b showed charac-
teristic singlet signals at
d 19.9 and 114.3 ppm, assigned to the
methyl and cyano carbons, respectively.
d 8.78 and 9.09 ppm assigned to the H-4pyridine in compounds 6a
On the other hand, treating ethyl chromone-3-carboxylates
5a,b13 and chromone-3-carboxamides 5c,d8 with 1H-benzimida-
zol-2-ylacetonitrile (1), in boiling ethanol containing few drops of
triethylamine, produced pyrido[1,2-a]benzimidazoles 6a,b. The
reactions proceed via deprotonation of compound 1, intermediate
and 6b, respectively. Furthermore, the mass spectrum of compound
6a showed the molecular ion peak at m/z 329, which agrees with
the molecular formula (C19H11N3O3) and supports the structure.
Next, the chemical behaviour of compound 1 towards chro-
mone-3-carbonitriles 7a,b14 was studied under basic conditions.
Thus, reaction of compound 1 with chromone-3-carbonitrile 7a,15
in boiling ethanol containing few drops of triethylamine, gave the
novel angular heteroannulated chromone identified as chromeno
[2,3:6,5]pyrido[1,2-a]benzimidazole-6-carbonitrile 8a, the other
expected product 9a was ruled out on the basis of the spectral data
A, which underwent nucleophilic attack at C-2 position with
g-
pyrone ring opening of compounds 5aed to produce intermediates
F. Cyclocondensation of the latter intermediates F, via loss of eth-
anol or ammonia molecules, afforded the target compounds 6a,b as
depicted in Scheme 2. The IR spectra of compounds 6a and 6b

M.A. Ibrahim / Tetrahedron 69 (2013) 6861e6865
6863
O
O
O
O
X
R
N
N
X
+
N
H
N
H
O
O
R
CN
CN
A
5
a
X
R
F
H
OEt
OEt
NH
b
c
CH
3
-HX
H
2
NH
CH
3
d
2
O
O
O
OH
O
O
+H+
N
N
6a; 54-57%
6b; 56-60%
N
N
H
H
R
CN
G
R
CN
6
a; R = H
b; R = CH
3
Scheme 2. Reactions of compound 1 with chromone derivatives 5aed.
(Scheme 3). The reaction of compound 1 with 6-methylchromone-
3-carbonitrile 7b showed different behaviour and the reaction
proceeds in a different mechanism producing 2-amino-3-(1H-
benzimidazol-2-yl)-7-methyl-5H-chromeno[2,3-b]pyridin-5-one
(9b) (Scheme 3). The formation of compound 9b rather than 8b
may be attributed to the electron donating nature of the methyl
group in compound 7b, which could increase the nucleophilicity of
the phenolate anion as compared with the NHimidazole group.
Compound 9b was obtained from the reaction of compound 1 with
2-amino-6-methylchromone-3-carboxaldehyde (10b)16 under the
same reaction conditions. Similarly, compound 9a was obtained
from the reaction of compound 1 with 2-aminochromone-3-
carboxaldehyde (10a) (Scheme 3).16,17 The IR spectrum of com-
pound 8a showed characteristic absorption bands at 2234 and 1657
assigned to (C^N) and (C]Og-pyrone), respectively. The 1H NMR
spectrum of compounds 8a showed characteristic singlet signal at
instrument (70 eV). Elemental microanalyses were performed on
a PerkineElmer CHN-2400 analyzer.
3.2. General procedure for the reaction of 1H-benzimidazol-
2-ylacetonitrile (1) with 3-substituted chromones
To
a solution of 1H-benzimidazol-2-ylacetonitrile (0.31 g,
2 mmol) in absolute ethanol (10 mL) containing two drops of
triethylamine, a solution of chromone derivatives 2, 4, 5, 7 and/or
10 (2 mmol) in absolute ethanol (15 mL) was added and the re-
action mixture was heated at reflux for 30 min. The yellow crystals
obtained after cooling were filtered off and recrystallized from DMF
to give compounds 3, 6, 8 and 9, respectively.
3.2.1. 1-(2-Hydroxyphenyl)pyrido[1,2-a]benzimidazole-4-carbonitrile
(3a). Yield (61e64%), mp 296 ꢁC. IR (KBr, cmꢀ1): 3421 (OH), 3073
(CHarom.), 2231 (C^N), 1628 (C]N),1609 (C]C). 1H NMR (300 MHz,
d
8.79 ppm, assigned to the H-4pyridine. Its mass spectrum showed
the molecular ion peak, as the base peak, which is coincident with
the formula weight (311.30) and confirms the structure. The 1H
NMR spectra of compounds 9a and 9b showed exchangeable sig-
nals attributed to the NH2 and NH protons, in addition to charac-
DMSO-d6):
d
6.71 (d, J¼9.0 Hz, 1H, AreH), 6.98 (d, J¼7.2 Hz, 1H,
AreH), 7.10e7.17 (m, 3H, AreH), 7.45e7.58 (m, 3H, AreH), 7.92 (d,
J¼8.1 Hz, 1H, AreH), 8.33 (d, J¼7.2 Hz, 1H, AreH), 10.20 (br s, 1H, OH
exchangeable with D2O). 13C NMR (75 MHz, DMSO-d6):
d 98.9, 111.9,
teristic singlet signals at d 8.44 ppm, assigned to the H-4pyridine. The
114.1, 115.8, 115.9, 119.4, 119.7, 120.2, 121.6, 126.0, 129.3, 130.1, 132.4,
137.8, 144.1, 144.3, 146.3, 155.4. MS (m/z, %): 286 (Mþ1, 17), 285 (Mþ,
100), 268 (10), 255 (11), 149 (49), 114 (15), 102 (8), 77 (11) and 64
(12). Anal. Calcd for C18H11N3O (285.29): C, 75.78; H, 3.89; N, 14.73%.
Found: C, 75.53; H, 3.55; N, 14.49%.
mass spectrum of compound 9b showed the molecular ion peak, as
the base peak, at m/z 342, which agrees well with the formula
weight (342.35) and confirms the identity of the structure.
3. Experimental
3.1. General
3.2.2. 1-(2-Hydroxy-5-methylphenyl)pyrido[1,2-a]benzimidazole-4-
carbonitrile (3b). Yield (63e65%), mp>320 ꢁC. IR (KBr, cmꢀ1):
3446 (OH), 3045 (CHarom.), 2920, 2837 (CHaliph.), 2231 (C^N), 1629
Melting points are uncorrected and were determined on a digi-
tal Stuart SMP3 apparatus. Infrared spectra were measured on
a PerkineElmer 293 spectrophotometer (cmꢀ1), using KBr disks. 1H
NMR (300 MHz and 500 MHz) and 13C NMR (75 MHz) spectra were
measured on Mercury-300BB spectrometers and Jeol Eca-500 MHz,
(C]N), 1609 (C]C). 1H NMR (300 MHz, DMSO-d6):
d 2.30 (s, 3H,
CH3), 6.76 (d, J¼9.0 Hz, 1H, AreH), 6.97 (t, J¼7.5 Hz, 1H, AreH), 7.16
(t, J¼7.2 Hz, 1H, AreH), 7.26 (s, 1H, AreH), 7.34 (d, 1H, J¼7.8 Hz,
AreH), 7.48e7.53 (m, 2H, AreH), 7.91 (d, J¼8.1 Hz, 1H, AreH), 8.32
(d, J¼7.2 Hz, 1H, AreH), 10.00 (br s, 1H, OH exchangeable with D2O).
using DMSO-d6 as a solvent and TMS (
d
) as the internal standard.
13C NMR (75 MHz, DMSO-d6):
d 19.9, 98.7, 111.8, 114.3, 115.8, 119.3,
Mass spectra were obtained using GCeMS qp 1000 ex Scheimadzu
119.6, 121.6, 126.0, 128.4, 129.3, 130.1, 132.8, 134.7, 137.8, 144.0,

6864
M.A. Ibrahim / Tetrahedron 69 (2013) 6861e6865
N
O
a
O
N
NC
R
N
+
N
H
N
H
O
O
R
CN
CN
H
7
A
a; R=H
R = H
b; R= CH
3
route a
R = CH
3
R
O
N
R
HO
NH
N
H
N
N
O
N
O
H
N
+H+
CN
I
O
N
H
R
R
N
H
O
N
HN
O
H N
2
K
N
O
9b; 68%
O
N
N
H
R
CN
-NH
N
H
J
H N
2
N
O
8a; 55%
3
9
R
a; R = H
b; R = CH
3
O
9a; 65%
EtOH/TEA
O
9b; 66%
N
O
N
OHC
R
N
+
N
H
CN
H N
2
O
CN
8
1
10
a; R = H
b; R = CH
a; R = H
b; R = CH
3
3
Scheme 3. Reactions of compound 1 with chromone-3-carbonitriles 7a,b and 2-amino-3-formylchromones 10a,b.
144.5, 146.2, 153.2. MS (m/z, %): 300 (Mþ1, 15), 299 (Mþ, 100), 282
(26), 163 (49), 91 (14), 77 (20). Anal. Calcd for C19H13N3O (299.33):
C, 76.24; H, 4.38; N, 14.04%. Found: C, 76.03; H, 4.14; N, 13.91%.
exchangeable with D2O). 13C NMR (75 MHz, DMSO-d6):
d 98.8,
114.3, 115.3, 116.1, 118.4, 119.6, 121.0, 122.0, 126.3, 129.8, 130.2, 132.4,
137.4, 142.6, 144.6, 145.7, 155.4, 162.9, 165.8. MS (m/z, %): 329 (Mþ,
2), 311 (100), 282 (10), 254 (17), 228 (5), 155 (12), 127 (19), 114 (18),
76 (11) and 64 (8). Anal. Calcd for C19H11N3O3 (329.31): C, 69.30; H,
3.37; N, 12.76%. Found: C, 69.51; H, 3.25; N, 12.38%.
3.2.3. 2-(2-Hydroxybenzoyl)-1-oxo-1,5-dihydropyrido[1,2-a]benz-
imidazole-4-carbonitrile (6a). Yield (54e57%), mp>320 ꢁC. IR
(KBr, cmꢀ1): 3354 (OH), 3174 (NH), 3056 (CHarom.) 2235 (C^N),
1670 (C]Opyridone), 1630 (C]Obenzoyl), 1591 (C]C). 1H NMR
3.2.4. 2-[(2-Hydroxy-5-methylbenzoyl)-1-oxo-1,5-dihydropyrido
[1,2-a]benzimidazole-4-carbonitrile (6b). Yield (56e60%), mp>320
ꢁC. IR (KBr, cmꢀ1): 3361 (OH), 3180 (NH), 3061 (CHarom.), 2231
(C^N), 1680 (C]Opyridone), 1654 (C]Obenzoyl), 1617 (C]C). 1H NMR
(500 MHz, DMSO-d6):
d
6.50 (d, J¼9.0 Hz, 1H, AreH), 7.14 (t, 1H,
AreH), 7.22 (t, 1H, AreH), 7.54e7.56 (m, 3H, AreH), 7.58 (t, 1H,
AreH), 7.97 (d, J¼8.4 Hz, 1H, AreH), 8.78 (s, 1H, H-4pyridine), 10.40
(br s, 1H, OH exchangeable with D2O), 13.40 (br s, 1H, NH
(300 MHz, DMSO-d6):
d 2.45 (s, 3H, CH3), 7.26 (br s, 2H, AreH),

M.A. Ibrahim / Tetrahedron 69 (2013) 6861e6865
6865
7.49e7.64 (m, 4H, AreH), 7.95 (s, 1H, AreH), 9.09 (s, 1H, H-4pyridine),
10.15 (br s, 1H, OH exchangeable with D2O), 13.22 (br s, 1H, NH
exchangeable with D2O). Anal. Calcd for C20H13N3O3 (343.33): C,
69.96; H, 3.82; N, 12.24%. Found: C, 69.74; H, 3.65; N, 12.35%.
NH), 9.99 (s, 1H, NH), 13.36 (s, 1H, NH). 13C NMR (75 MHz, DMSO-
d6): 20.3, 106.3, 110.6, 111.2, 111.7, 114.4, 117.8, 118.5, 120.8, 121.9,
123.2, 125.1, 126.6, 133.9, 135.1, 135.7, 142.4, 149.1, 152.6, 157.2. MS
(m/z, %): 343 (Mþ1, 24), 342 (Mþ, 100), 325 (41), 313 (17), 253 (5),
208 (11), 117 (6), 107 (11), 91 (8), 77 (20) and 64 (34). Anal. Calcd for
C20H14N4O2 (342.35): C, 70.17; H, 4.12; N,16.37%. Found: C, 69.84; H,
4.05; N, 16.15%.
d
3.2.5. 8-Oxo-8H-chromeno[2,3:6,5]pyrido[1,2-a]benzimidazole-6-
carbonitrile (8a). Yield (55%), mp>320 ꢁC. IR (KBr, cmꢀ1): 3066
(CHarom.), 2234 (C^N), 1657 (C]Og-pyrone), 1596 (C]N and C]C).
1H NMR (500 MHz, DMSO-d6):
d
6.37 (d, J¼8.6 Hz,1H, AreH), 7.18 (t,
J¼8.6 Hz, 1H, AreH), 7.55 (t, J¼8.0 Hz, 1H, AreH), 7.61 (d, J¼8.6 Hz,
1H, AreH), 7.63 (t, J¼7.4 Hz, 1H, AreH), 7.77 (d, J¼7.4 Hz, 1H, AreH),
7.88 (t, J¼7.4 Hz, 1H, AreH), 7.97 (d, J¼8.6 Hz, 1H, AreH), 8.79 (s, 1H,
H-4pyridine). MS (m/z, %): 312 (Mþ1, 13), 311 (Mþ, 21), 310 (100), 293
(13), 280 (9), 154 (11), 126 (11), 114 (9) and 77 (5). Anal. Calcd for
C19H9N3O2 (311.29): C, 73.31; H, 2.91; N, 13.50%. Found: C, 73.53; H,
2.75; N, 13.36%.
Supplementary data
Supplementary data related to this article can be found at
http://dx.doi.org/10.1016/j.tet.2013.06.011.
References and notes
1. Plaskon, A. S.; Grygorenko, O. O.; Ryabukhin, S. V. Tetrahedron 2012, 68,
2743e2757.
3.2.6. 2-Amino-3-(1H-benzimidazol-2-yl)-5H-chromeno[2,3-b]pyr-
idin-5-one (9a). Yield (65%), mp>320 ꢁC. IR (KBr, cmꢀ1): 3305, 3150
(NH2, NH), 3071 (CHarom.), 1645 (C]Og-pyrone), 1629 (C]N), 1614
2. Verma, A. K.; Pratap, R. Tetrahedron 2012, 68, 8523e8538.
3. Tang, L.; Feng, Q.; Zhao, J.; Dong, L.; Liu, W.; Yang, C.; Liu, Z. Food Chem. Toxicol.
2012, 50, 1460e1467.
(C]C). 1H NMR (500 MHz, DMSO-d6):
d
7.22 (t, J¼8.4 Hz,1H, AreH),
ꢀ
ꢁ
ꢁ
ꢁ
4. Gasparova, R.; Lacova, M. Molecules 2005, 10 937e960.
5. Sosnovskikh, V. Y.; Moshkin, V. S. Chem. Heterocycl. Compd. 2012, 48, 139e146.
6. Terzidis, M. A.; Zarganes-Tzitzikas, T.; Tsimenidis, C.; Stephanidou-Stephanatou, J.;
Tsoleridis, C. A.; Kostakis, G. E. J. Org. Chem. 2012, 77, 9018e9028.
7. Zarganes-Tzitzikas, T.; Terzidis, M. A.; Stephanidou-Stephanatou, J.; Tsoleridis, C. A.;
Kostakis, G. E. J. Org. Chem. 2011, 76, 9008e9014.
7.25 (t, J¼8.4 Hz, 1H, AreH), 7.45 (t, J¼7.6 Hz, 1H, AreH), 7.53 (t,
J¼6.8 Hz, 1H, AreH), 7.61 (d, J¼7.6 Hz, 1H, AreH), 7.68 (t, J¼8.4 Hz,
1H, AreH), 7.81 (t, J¼7.6 Hz, 1H, AreH), 8.15 (d, J¼7.6 Hz, 1H, AreH),
8.44 (s, 1H, H-4pyridine), 9.07 (s, 1H, NH exchangeable with D2O),
9.98 (s, 1H, NH exchangeable with D2O), 13.36 (s, 1H, NH ex-
changeable with D2O). Anal. Calcd for C19H12N4O2 (328.32): C,
69.51; H, 3.68; N, 17.06%. Found: C, 69.33; H, 3.61; N, 17.08%.
8. Ibrahim, M. A. Tetrahedron 2009, 65, 7687e7690.
9. Ibrahim, M. A. Synth. Commun. 2009, 39, 3527e3545.
10. Ibrahim, M. A. Arkivoc 2008, xvii, 192e204.
11. Klutchko, S.; Shavel, J.; von Strandtmann, M. V. J. Org. Chem. 1974, 39,
2436e2437.
12. Reddy, K. V.; Rao, A. V. S. Org. Prep. Proced. Int. 1997, 29, 355e357.
13. Machida, Y.; Nomoto, S.; Negi, S.; Jkuta, H.; Saito, I. Synth. Commun. 1980, 10,
889e895.
14. Petersen, U.; Heitzer, H. Liebigs Ann. Chem. 1976, 9, 1659e1662.
15. Ibrahim, M. A.; Hassanin, H. M.; Gabr, Y. A.; Alnamer, Y. A. J. Braz. Chem. Soc.
2012, 23, 905e912.
16. Ibrahim, S. S.; Allimony, H. A.; Abdel-Halim, A. M.; Ibrahim, M. A. Arkivoc 2009,
xiv, 28e38.
17. Ibrahim, M. A. Eur. J. Chem. 2010, 1, 124e128.
3.2.7. 2-Amino-3-(1H-benzimidazol-2-yl)-7-methyl-5H-chromeno
[2,3-b]pyridin-5-one (9b). Yield (66e68%), mp>320 ꢁC. IR (KBr,
cmꢀ1): 3298, 3154 (NH2, NH), 3061 (CHarom.), 2913, 2837 (CHaliph.),
1651 (C]Og-pyrone), 1633 (C]N), 1614 (C]C). 1H NMR (300 MHz,
DMSO-d6):
d 2.43 (s, 3H, CH3), 7.26e7.29 (m, 2H, AreH), 7.54 (t,
J¼8.7 Hz, 1H, AreH), 7.62 (d, 1H, AreH), 7.72 (d, 1H, AreH), 7.94 (s,
1H, AreH), 8.25 (d, 1H, AreH), 8.44 (s, 1H, H-4pyridine), 9.09 (s, 1H,