Synthesis and properties of cyanomethyl derivatives of imidazo[1,2-a] pyridine, imidazo[1,2-a]pyrimidine, and imidazo[2,1-b]thiazole

Article abstract of DOI:10.1007/s11178-008-2012-9

2-Cyanomethyl derivatives were obtained of imidazo[1,2-a]pyridine, imidazo[1,2-a]pyrimidine, and imidazo[2,1-b]thiazole, and their reactivity was investigated by an example of imidazo[1,2-a]pyridine: It was subjected to nitration, bromination, azo coupling and nitrosation. Acylation of the methylene group effected by amino acids esters with a subsequent addition of the amino group to the cyano group resulted in the formation of 5-amino-4-imidazo[1,2-a]- pyridin-2-yl-1-phenyl-1,2-dihydro-3H-pyrrol-3-one and 2-amino-1-ethyl-3- imidazol[1,2-a]pyridin-2-yl-4(1H)-quinolinone.

Full text of DOI:10.1007/s11178-008-2012-9

ISSN 1070-4280, Russian Journal of Organic Chemistry, 2008, Vol. 44, No. 2, pp. 257−262. © Pleiades Publishing, Ltd., 2008.
Original Russian Text © G.P. Kutrov, N.V. Kovalenko, Yu.M. Volovenko, 2008, published in Zhurnal Organicheskoi Khimii, 2008, Vol. 44, No. 2, pp. 264−268.
Synthesis and Properties of Cyanomethyl Derivatives
of Imidazo[1,2-a]pyridine, Imidazo[1,2-a]pyrimidine,
and Imidazo[2,1-b]thiazole
G. P. Kutrov†, N. V. Kovalenko, and Yu. M. Volovenko
Taras Shevchenko Kiev National University, Kiev, 01033 Ukraine
e-mail: kutrov@ukr.net
Received May 15, 2007
Abstract—2-Cyanomethyl derivatives were obtained of imidazo[1,2-a]pyridine, imidazo[1,2-a]pyrimidine, and
imidazo[2,1-b]thiazole, and their reactivity was investigated by an example of imidazo[1,2-a]pyridine: It was
subjected to nitration, bromination, azo coupling and nitrosation. Acylation of the methylene group effected by
amino acids esters with a subsequent addition of the amino group to the cyano group resulted in the formation of
5-amino-4-imidazo[1,2-a]-pyridin-2-yl-1-phenyl-1,2-dihydro-3H-pyrrol-3-one and 2-amino-1-ethyl-3-
imidazo[1,2-a]pyridin-2-yl-4(1H)-quinolinone.
DOI: 10.1134/S1070428008020127
Derivatives of imidazoheterocycles can exhibit
a versatile biological activity: Nonsteroid antiphlogistic
drugs [1], cardiotonic and antiarrhithmic pharmaceuticals
[2], substances with a neurotropic action [3, 4], and those
possessing cytoprotective and antitumor activity [5] are
found among these compounds. Therefore the
development of new preparation procedures for these
fused systems is very promising.
carboxylic acids. However in reaction of diazonium salts
with compound IIIa formed bisazo dyes of IVa and IVb
type (Scheme 2). In the 1H NMR spectra of compounds
IVa and IVb the signal of proton H5 is shifted downfield
by 0.9 ppm. This abnormal paramagnetic shift indicates
that these compounds are present prevailingly in the syn-
conformation [10]. No signals from the position 3 of the
bicycle and CH2 group and also the chemical shifte and
intensities of the other signals in the 1H spectrum confirm
the assumed structures of the azo dyes IVa and IVb. At
equivalent ratio of the reactant an intractable mixture
was obtained containing along with other compounds
(TLC data) bisazo dye IV and free base IIIa.
The bromomethyl derivatives of imidazo[1,2-a]-
pyridine, imidazo[1,2-a]pyrimidine, and imidazo[2,1-
b]thiazole I, II [6, 7] that we have previously synthesized
can be by a known procedure converted into the
corresponding cyanomethyl heterocycles III [8].
Methylene group in these compounds is less reactive
than in the 1-methyl-2-cyanomethylbenzimidazole [9].
It is not acylated with anhydrides and chlorides of
The nitrosation of imidazo[1,2-a]pyridine-2-ylaceto-
nitrile (IIIa) led to the formation of 2-(hydroxyimino)(3-
nitrosoimidazo[1,2-a]pyridine-2-yl)-acetonitrile (VII).
Scheme 1.
Y
Y
Y
N
N
NH
R3
R1
Na2CO3
R1
Na2CO3
H2O
R1
CH2Br
CH2CN
CH2Br
N+_
Br
KCN + MeOH
N
N
R2
R2
R2
R3
R3
IIIa_IIIe
IIa_IIe
Ia
Ia–IIIa, R1 = R2 = H, Y = CH=CH, R3 = H; II, III, R1 = Cl, R2 = H, Y = CH=CH, R3 = Cl (b); R1 = R2 = H, Y = CH=CH,
R3 = Br (c); R1 = H, R2 = CH3, Y = CH3–CN=CH, R3 = H (d); R1 = H, R2 = H, Y = S, R3 = Br (e).
† Deceased.
257

KUTROV et al.
258
1
In the H NMR spectrum of this compound a slightly
broadened singlet of the hydroxy group proton appeared
in the region 15 ppm, and it disappeared at treatment
with deuterium oxide. The signal of H5 proton is shifted
downfield by 1.4 ppm compared to the spectrum of the
initial compound IIIa indicating that this substance is
present prevailingly in the syn-conformation [10].
imidazo[1,2-a]pyridine-2-yl)-1-phenyl-1,2-dihydro-3H-
pyrrol-3-one (XIII).
The treatment of 2-amino-3-aryl-4-quinolones in
acetic acid solution with sodium nitrite is known to lead
to the formation of the derivatives of a quino[2,3-c]-
cinnolone heterocyclic system [11]. However the treat-
ment of amine X with sodium nitrite in dilute hydro-
chloric acid resulted in the nitrosation in the position 3
of imidazopyridine giving a dihydrochloride of nitroso
derivative XIV converted into compound XV with
aqueous ammonia. This reaction route is due to the
electron-donor effect of the nitrogen atom in the position
2 of the imidazo[1,2-a]pyridine fragment [12]. The
intramolecular coordination of the amino group proton
in 2-amino-3-(3-nitrosoimidazo[1,2-a]pyridine-2-yl)-1-
ethyl-4(1H)-quinolinone (XV) hampers the reciprocal
rotation of both heterocycles.
The bromination and nitration of compound IIIa
occurred only in the position 3. Salt V isolated after
bromination in dioxane (Scheme 2) treated with 2 M
alkali solution was readily converted into (3-bromo-
imidazo[1,2-a]pyridine-2-yl)acetonitrile (IIIc).
The nitration of nitrile IIIa gave (3-nitroimidazo-
[1,2-a]pyridine-2-yl)acetonitrile (VI).
Neither salt V nor base IIIc entered into the reactions
of azo coupling, nitrosation, bromination, and nitration.
Imidazo[1,2-a]pyridine-2-ylacetonitrile (IIIa) was
acylated at the methylene group with methyl 2-(ethyl-
amino)benzoate in the presence of sodium tert-butylate
(structure VIII), but we failed to isolate this substance
for the ethylamino group underwent an intramolecular
addition to the cyano group (Scheme 3). The product of
the reaction was 2-amino-3-(imidazo[1,2-a]pyridine-2-
yl)-1-ethyl-4(1H)-quinolinone (X). Similarly compound
IIIa reacted with ethyl N-phenylglycinate yielding 5-
amino-4-imidazo[1,2-a]pyridine-2-yl-1-phenyl-1,2-
dihydro-3H-pyrrol-3-one (XIII).
EXPERIMENTAL
IR spectra were recorded on a spectrophotometer Pye-
Unicam SP3-300 from KBr pellets. H NMR spectra
were registered on a spectrometer Varian Mercury 400
(400 MHz), internal reference TMS. The reaction
progress was monitored and the purity of products
obtained was checked by TLC on Silufol UV-254 plates.
1
Imidazo[1,2-a]pyridin-2-ylacetonitrile (IIIa). To
a dispersion of 21.2 g (0.073 mol) of 2-bromomethyl-
1H-imidazo[1,2-a]pyridinium bromide in 140 ml of
methanol a solution was added of 7.42 g (0.07 mol) of
sodium hydrogen carbonate in 56 ml of water.Acolorless
precipitate formed, the mixture was stirred for 5 min,
then 7.6 g (0.12 mol) of potassium cyanide was added.
At the treatment of crude products X and XIII with
dilute hydrochloric acid bishydrochlorides IX and XII
were obtained that on adding aqueous ammonia provided
analytically pure 2-amino-(3-imidazo[1,2-a]pyridin-2-
yl)-1-ethyl-4(1H)-quinolinone (X) and 5-amino-(4-
Scheme 2.
O
H
N
N
N
N
CH2CN
CH2CN
C_CN
N
N
N
O
NO2
Br
IIIc
N
NaNO2
VI
VII
OH_
HNO3,
H2SO4
N_Ar
N
H
N
_
+
N
NH
]
N
Ar[N
Cl
Br2
C_CN
CH2CN
CH2CN
N+
N
N
Dioxane
N
N
Br _
V
IIIa
Br
Ar
IVa, IVb
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 44 No. 2 2008

SYNTHESIS AND PROPERTIES OF CYANOMETHYL DERIVATIVES
259
Scheme 3.
N
CH3O2C
HN
N
HN
CN
CO2C2H5
(CH3)3CONa
CH3
IIIa
(CH3)3CONa
O
O
N
N
N
N
H
CN
N
HN
CN
CH3
XI
VIII
O
O
N
N
N
N
Ph
N
2HCl
H
N
N
2HCl
CH3
N
H
H
.
NH3 H2O
XII
H
IX
.
O
NH3 H2O
O
N
N
N
N
N
N
Ph
CH3
N
N
H
H
H
XIII
H
X
Scheme 4.
H
H
H
H
.
N
CH3
.
N
CH3
.
N
.
N
.
.
N
N
.
NH3 H2O
NaNO2
2HCl
X
N
N
O
O
HCl
N
N
O
O
XIV
XV
The stirring was continued for 6 h, the precipitate was
filtered off and washed with ethanol. The mother liquor
was evaporated to dryness, and the reaction product was
extracted with ether from the dry residue. The insoluble
residue was alkalinized with 2 M solution of NaOH and
several times treated with ether. The ether was distilled
off on a rotary evaporator, the crystals of the nitrile were
dried and recrystallized from 2-propanol. Yield 5.72 g
(51%), mp 91–92°C (92°C [8]). IR spectrum, ν, cm–1:
1
2254 (CN). H NMR spectrum (DMSO-d6), δ, ppm:
8.47 d (1H, J 6.1 Hz), 7.88 s (1H), 7.46 d (1H, J 8.8 Hz),
7.22 m (1H), 6.84 m (1H), 3.99 s (2H). Found, %:
C 68.56; N 26.54. C9H7N3. Calculated, %: C 68.78;
N 26.74.
Compounds IIIb–IIIe. General procedure. To 0.1 mol
of base II in 140 ml of methanol 7.6 g (0.12 mol) of
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 44 No. 2 2008

KUTROV et al.
260
an ice bath. After 1 h 9 mg (0.1 mmol) of Na2CO3 was
added, the separated precipitate was filtered off, washed
with ethanol, dried, and crystallized.
potassium cyanide was added. The mixture was stirred
for 5–6 h, the precipitate was filtered off and washed
with ethanol. The mother liquor was evaporated to
dryness, and the nitrile was extracted with ether from
the dry residue. The insoluble residue was alkalinized
with 2 M solution of NaOH and several times treated
with ether. The ether was distilled off on a rotary
evaporator.
(2Z)-{3-[(E)-Phenyldiazenyl]imidazo[1,2-a]-
pyridin-2-yl}(phenylhydrazono)acetonitrile (IVa).
Yield 1.14 g (72%), mp 191°C (decomp.) (aqueous DMF).
IR spectrum, ν, cm–1: 2212.39 (CN). 1H NMR spectrum
(acetone-d6), δ, ppm: 9.30 d (1H, J 5.6, J 9.6 Hz),
8.82 t (1H, J 8.8 Hz), 8.37 d (1H, J 8.4 Hz), 8.21 m (2H,
Hο, PhN=N), 8.05 t (1H, J 6.5 Hz), 7.93–7.71 m (8H,
protons PhNH, Hm,p, PhN=N). Found, %: C 69.25;
N 26.97. C21H15N7. Calculated, %: C 69.03; N 26.83.
(3,6-Dichloroimidazo[1,2-a]pyridin-2-yl)aceto-
nitrile (IIIb). Yield 8.54 g (50%), mp 130°C (ethanol).
1H NMR spectrum (DMSO-d6), δ, ppm: 8.39 s (1H),
7.66 d (1H, J 9.6 Hz), 7.37 d (1H, J 9.6 Hz), 4.06 s (2H,
CH2). Found, %: C 47.45; Cl 31.22; N 18.14. C9H5Cl2N3.
Calculated, %: C 47.82; Cl 31.37; N 18.59.
2-{3-[(E)-2-(4-Methoxyphenyl)diazenyl]-imidazo-
[1,2-a]pyridin-2-yl}-2-[(Z)-2-(4-methoxyphenyl)-
hydrazono]acetonitrile (IVb). Yield 1.00 g (65%), mp
288°C (decomp.). IR spectrum, ν, cm–1: 2218 (CN), 1722
(C=O). 1H NMR spectrum (acetone-d6), δ, ppm: 9.36 d
(1H, J 5.6 Hz), 8.88 t (1H, J 8.8 Hz) 8.65 m (2H, Hο,
PhN=N), 8.47–8.34 m (5H, Hm,m', PhN=N, H8), 8.12–
(3-Bromoimidazo[1,2-a]pyridin-2-yl)acetonitrile
(IIIc). a. Yield 9.56 g (56%), mp 149°C (2-propanol).
1H NMR spectrum (DMSO-d6), δ, ppm: 8.25 d (1H,
J 6.8, J 9.6 Hz), 7.59 d (1H, J 9.2 Hz), 7.36 m (1H),
7.08 m (1H), 4.03 s (2H, CH2). Found, %: Br 34.52;
N 17.60. C9H6BrN3. Calculated, %: Br 33.85; N 17.80.
ο
'
8.05 t (3H, H , PhN=N, J 6.5 Hz), 4.27 s (3H, OCH3),
b. To 0.64 g (0.002 mol) of salt V in 10 ml of water
was added at room temperature 2 M solution of NaOH
till pH 8. The separated precipitate was filtered off,
washed with water, dried, and crystallized from
4.23 s (1H, OCH3). Found, %: C 62.56; N 20.43.
C25H19N7O4. Calculated, %: C 62.37; N 20.36.
3-Bromo-2-(cyanomethyl)-1H-imidazo[1.2-a]-
pyridin-4-ium bromide (V). To 0.8 g (5 mmol)
imidazo[1,2-a]pyridin-2-ylacetonitrile (IIIa) in 20 ml of
dioxane was added at room temperature 0.26 ml (5 mmol)
of bromine, and the mixture was stirred for 4 h. The
separated precipitate was filtered off, washed with
dioxane, dried, and crystallized from 2-propanol. Yield
1
2-propanol. Yield 0.43 g (99%), mp 149°C. H NMR
spectrum (DMSO-d6), δ, ppm: 8.25 d (1H, J 6.8 Hz),
7.59 d (1H, J 9.2 Hz), 7.36 m (1H), 7.08 m (1H), 4.03 s
(2H, CH2). Found, %: Br 34.68. N 17.67. C9H6BrN3.
Calculated, %: Br 33.85; N 17.80.
1
0.98 g (93%), mp 142°C. H NMR spectrum (DMSO-
(5,7-Dimethylimidazo[1,2-a]pyrimidin-2-yl)aceto-
nitrile (IIId). Yield 9.63 g (68%), mp 184–186°C
(ethanol). IR spectrum, ν, cm–1: 2235.99 (CN). 1H NMR
spectrum (DMSO-d6), δ, ppm: 7.88 s (1H), 6.84 s (1H),
3.99 s(2H, CH2), 2.57 s (6H, CH3 and CH3). Found, %:
C 64.56; N 30.27. C10H10N4. Calculated, %: C 64.50;
N 30.09;.
d6), δ, ppm: 8.40 d (1H, J6.8 Hz), 7.74 d (1H, J 8.8 Hz),
7.56 m (1H), 7.25 m (1H), 5.4 br.s (H2O, exchange with
a proton), 4.16 s (2H, CH2). Found, %: C 34.19; Br 50.52;
N 13.31. C9H7Br2N3. Calculated, %: C 34.10; Br 50.42;
N 13.26.
(3-Nitroimidazo[1,2-a]pyridin-2-yl)acetonitrile
(VI). To a nitrating mixture composed of 0.5 ml
(7.5 mmol) of 70% nitric acid and 10 ml of concn. H2SO4
was added 0.8 g (5 mmol) of nitrile IIIa, and the reaction
mixture was stirred for 3 h at room temperature. Then it
was poured on ice, and 12 mg (0.1 mmol) of sodium
sulfate was added. The separated precipitate was filtered
off, washed with water, dried, and crystallized. Yield
0.14 g (18%), mp 173°C (decomp.) (2-propanol).
1H NMR spectrum (DMSO-d6), δ, ppm: 9.4 d (1H,
J 6.8 Hz), 7.96 d (1H, J 9.2 Hz), 7.84 m (1H), 7.50 m
(1H), 4.52 s (2H, CH2). Found, %: C 53.40; N 28.01.
C9H6N4O2. Calculated, %: C 53.47; N 27.71.
(5-Bromoimidazo[2,1-b][1,3]thiazol-6-yl)aceto-
nitrile (IIIe). Yield 7.18 g (46%), mp 110°C (2-prop-
anol). IR spectrum, ν, cm–1: 2245 (CN). 1H NMR spec-
trum (DMSO–d6), δ, ppm: 7.72 d (1H, J 4.8 Hz), 7.38 d
(1H), 3.86 s (2H, CH2). Found, %: N 17.36; S 13.24.
C7H4BrN3S. Calculated, %: N 17.47; S 13.63.
Azo dyes IVa and IVb. General procedure. The
diazonium salt was obtained at 0°C from 7.6 mmol of
amine, 0.54 g (7.8 mmol) of sodium nitrite, 1.91 ml
(22.8 mmol) of hydrochloric acid, and 6.34 ml of water,
sodium acetate was added till neutral reaction toward
Congo, and the mixture obtained was added to the ethanol
solution of 0.52 g (3.3 mmol) of nitrile (IIIa) cooled on
(2)-(Hydroxyimino)(3-nitrosoimidazo[1,2-a]-
pyridin-2-yl)acetonitrile (VII). To 0.39 g (0.025 mol) of
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SYNTHESIS AND PROPERTIES OF CYANOMETHYL DERIVATIVES
261
nitrile IIIa in 4 ml of glacial acetic acid was added by
small portions a solution of 0.2 g (0.029 mol) of sodium
nitrite in 1 ml of water. The reaction proceeded for 15 min,
then 8–10 ml of water was added. The separated
precipitate was filtered off, washed with water, and dried.
To the mother liquor 0.5 g of additional dry sodium nitrite
was added. The separated precipitate was identical to
the preceding portion. Yield 0.42 g (79%), mp 236°C
(aqueous DMF). 1H NMR spectrum (DMSO-d6), δ, ppm:
15.05 br.s (1H, OH), 9.70 d (1H, J 6.8 Hz), 8.09 m (2H),
7.58 m (1H). Found, %: C 50.57; N 32.41. C9H5N5O2.
Calculated, %: C 50.24; N 32.55.
filtered off. Yield 1.8 g (52%), mp 242°C. IR spectrum, ν,
cm–1: 1623–1658 (C=O). 1H NMR spectrum (DMSO-d6),
δ, ppm: 8.80 d (1H, J 5.8 Hz*), 8.76 s (1H*), 8.02 d (2H,
NH2), 8.99 d (1H, J 8.8 Hz*), 7.74 t (1H*), 7.51 t (2H,
HmPh), 7.45 d (2H, HOPh, J 8.8 Hz), 7.36 m (2H, CH
and HïPh), 4.36 C (2H, CH2). Found, %: C 56.34; Cl 19.71;
N 15.56. C17H16Cl2N4O. Calculated, %: C 56.21; Cl 19.52;
N 15.42.
5-Amino(4-imidazo[1,2-a]pyridin-2-yl)-1-phenyl-
1,2-dihydro-3H-pyrrol-3-one (XIV). A solution of 0.5
g (1.4 mmol) of salt XIII in water was neutralized with
a water solution of sodium hydrogen carbonate, the
precipitate was filtered off. Yield 0.15 g (38%), mp
2-Amino(3-imidazo[1,2-a]pyridin-2-yl)-1-ethyl-
4(1H)-quinolinone dihydrochloride (X). A mixture of
1.57 g (1 mmol) of nitrile IIIa, 2.17 g (1 mmol) of ethyl
N-ethylanthranilate, and 4 g of sodium tert-butylate was
boiled in 30 ml of pyridine, the pyridine was distilled
off in a vacuum, and the residue was ground in 100 ml
of water. To the reaction mixture 27 ml of 3.5% HCl was
added at stirring, and some hours later the precipitate
obtained was filtered off. Yield 2.02 g (57%), mp 190°C.
1
185°C. IR spectrum, ν, cm–1: 1578 (C=O). H NMR
spectrum (DMSO-d6), δ, ppm: 8.55 d (1H, J 6.4 Hz*),
8.32 s (1H*), 8.01 br.s (2H, NH2), 7.62 d (1H, J 8.8 Hz*),
7.49 t (1H*), 7.45 m (3H, Hm,ïPh), 7.30 d (2H, HOPh,
J 8.8 Hz), 4.20 s (2H, CH2). Found, %: C 70.63; N 19.38.
C17H14N4O. Calculated, %: C 70.33; N 19.30.
2-Amino-1-ethyl-3-(3-nitrosoimidazo[1,2-a]-
pyridin-2-yl)-4(1H)-quinolinone dihydrochloride
(XV). To 1 g (3 mmol) of amine XI in dilute hydrochloric
acid was added 0.3 g (4.3 mmol) of sodium nitrite. Some
hours later the precipitate obtained was filtered off,
washed with acetone and ether. Yield 0.77 g (80%), mp
1
IR spectrum, ν, cm–1: 1651(C=O). H NMR spectrum
(DMSO-d6), δ, ppm: 9.08 d (1H, J 6.71 Hz*), 8.66 s
(1H*), 8.44 br.s (2H, NH2), 8.24 d (1H, J 7.93 Hz*),
7.95 m (4H), 7.45 m (2H), 4.32 t (2H, CH2, J 7.32 Hz),
1.35 t (3H, CH3). Found, %: N 14.92; Cl 18.97.
C18H18Cl2N4O. Calculated, %: N 14.85; Cl 18.79.
1
201°C (decomp.) (2-propanol). H NMR spectrum
(DMSO-d6), δ, ppm: 9.76 d (1H, J6.71*), 8.64 br.s (2H,
NH2), 8.17 d (1H, J 7.93 Hz*), 8.14 m (2H**), 7.00 m
(2H**), 7.61m (2H*), 4.54 s (2H, CH2), 1.39 t (3H).
Found, %: C 53.32; Cl 17.56; N 17.38. C18H17Cl2N5O2.
Calculated, %: C 53.21; Cl 17.45; N 17.24.
2-Amino-(3-imidazo[1,2-a]pyridin-2-yl)-1-ethyl-
4(1H)-quinolinone (XI). In water was dissolved 0.5 g
(0.0013 mol) of salt X, a base was added, and some hours
later the precipitate obtained was filtered off. Yield
0.29 g (73%), mp 139–140°C. IR spectrum, ν, cm–1: 1626
(C=O). 1H NMR spectrum (DMSO-d6), δ, ppm: 9.36 br.s
(2H, NH2), 9.21 s (1H*), 8.66 d (1H, J 6.71 Hz*), 8.32 d
(1H, J 7.93 Hz*), 7.61 m (2H**), 7.28 m (2H*,**), 6.90
m (1H*), 4.32 t (1H, CH2-N, J 7.2 Hz), 1.35 t (3H, CH3).
Calculated, %: C 71.04; N 18.41. C18H16N4O. Found,
%: C 71.21; N 18.68;.
2-Amino-1-ethyl-3-(3-nitrosoimidazo[1,2-a]-
pyridin-2-yl)-4(1H)-quinolinone (XVI). To a solution
of 0.5 g (1.2 mmol) of salt XV in water several drops of
aqueous ammonia was added, and the precipitate formed
was filtered off.Yield 0.24 g (58%), mp 229°C (decomp.).
IR spectrum, ν, cm–1: 1614 (C=O). 1H NMR spectrum
(DMSO-d6), δ, ppm: 9.80 d (1H, J 8.00 Hz*), 7.95 m
(2H*), 7.63 m (2H**), 7.49 br.s (2H, NH2), 7.41 m (2H*),
7.29 m (1H**), 4.34 s (2H, CH2), 1.43 t (3H, CH3).
Found, %: C 64.97; N 21.22. C18H15N5O2. Calculated,
%: C 64.86; N 21.02.
5-Amino-4-imidazo[1,2-a]pyridin-2-yl-1-phenyl-
1.2-dihydro-3H-pyrrol-3-one dihydrochloride XIII).
A mixture of 1.57 g (1 mmol) of nitrile IIIa, 1.90 g
(0.01 mol) ethyl N-phenylaminoacetate, and 4 g of
sodium tert-butylate was boiled in 30 ml of pyridine for
2.5 h. The pyridine was distilled off in a vacuum, and
the residue was ground in 100 ml of water. To the reaction
mixture 3 ml of acetic acid was added at stirring, and
some hours later the precipitate obtained was filtered
off, the precipitate was dissolved in dilute hydrochloric
acid (1:10), and some hours later the precipitate was
The signals from the imidazo[1.2-a]pyridine ring are
marked with one asterisk, from the quinolone fragment,
with two asterisks.
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