The investigations in 2,3-biquinoline series. 25*. Synthesis of 4-(2-quinolinyl)-pyrrolo[1,2-a]quinolines and 4-(2-quinolyl)-imidazo[1,2-a] quinolines

Article abstract of DOI:10.1007/s10593-009-0267-x

A method has been developed for the synthesis of 4-(2-quinolinyl)-1,2,3,3a- tetrahydropyrrolo-[1,2-a]quinolines based on the 1,3-dipolar cycloaddition reaction of α,β-unsaturated carbonyl compounds to 2,3-biquinolinium salts. Oxidation in benzene using Mn

Full text of DOI:10.1007/s10593-009-0267-x

Chemistry of Heterocyclic Compounds, Vol. 45, No. 3, 2009
THE INVESTIGATIONS IN 2,3'-BIQUINOLINE
SERIES. 25*. SYNTHESIS OF 4-(2-QUINOLINYL)-
PYRROLO[1,2-a]QUINOLINES AND 4-(2-QUINOLYL)-
IMIDAZO[1,2-a]QUINOLINES
T. P. Glushchenko1, A. V Aksenov1**, and V. I. Goncharov2
A method has been developed for the synthesis of 4-(2-quinolinyl)-1,2,3,3a-tetrahydropyrrolo-
[1,2-a]quinolines based on the 1,3-dipolar cycloaddition reaction of α,β-unsaturated carbonyl
compounds to 2,3'-biquinolinium salts. Oxidation in benzene using MnO2 gave 4-(2-quinolinyl)-
pyrrolo[1,2-a]quinolines. It was found that a side product of the 1,3-dipolar cycloaddition is 7,14-di-
benzoyl-6,13-di(2-quinolyl)-6a,7,13a,14-tetrahydro-7a,14a-diazadibenzo[a,h]anthracene. Reaction of
1'-phenacyl-2,3'-biquinolinium salts with hydroxylamine in acetic acid gave 4-(2-quinolyl)imidazo-
[1,2-a]quinolines.
Keywords: 2,3'-biquinoline, 1'-R-3-(2-quinolyl)quinolinium bromides, 7,14-dibenzoyl-6,13-di(2-quinolyl)-
6a,7,13a,14-tetrahydro-7a,14a-diazadibenzo[a,h]anthracene, α,β-unsaturated carbonyl compounds, 4-(2-
quinolyl)imidazo[1,2-a]quinolines, 4-(2-quinolinyl)pyrrolo[1,2-a]quinolines, 4-(2-quinolinyl)-1,2,3,3a-
tetrahydropyrrolo[1,2-a]quinolines, cyclization.
We have previously developed a method for the synthesis of 1'-R-2,3'-biquinolinium salts 1 [2]. These
compounds have been used as starting materials in the preparation of various 2,3'-biquinoline derivatives, viz.
dihydro derivatives [2-6], biquinolones [7], and thiones [8, 9]. This report concerns the synthesis of previously
unknown 4-(2-quinolinyl)pyrrolo[1,2-a]quinolines and 4-(2-quinolyl)imidazo[1,2-a]quinolines based on them.
We have shown that the reactions of the conjugated bases of salts 1a,b (prepared by treating the
corresponding salts with Et3N in CH2Cl2 or with AcONa in AcOH) with the α,β-enones and nitriles of
α,β-unsaturated carboxylic acids give 4-(2-quinolinyl)-1,2,3,3a-tetrahydropyrrolo[1,2-a]quinolines 3 in 44-82%
yield.
1
The reaction occurs diastereospecifically. The H NMR spectra show signals for only one diastereomer
whose configuration we were unable to determine. The side product formed was that of the reaction of the
starting salt with its conjugate base. In the case of the phenacyl salt 1a it could be isolated and characterized.
_______
* For Communication 24 see [1].
** To whom correspondence should be addressed, e-mail: k-biochem-org@stavsu.ru.
1Stavropol State University, Stavropol 355009, Russia.
2Stavropol State Medical Academy, Stavropol 355017, Russia; e-mail: sgma@statel.stavropol.ru.
__________________________________________________________________________________________
Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 433-439, March, 2009. Original
article submitted October 9, 2007.
0009-3122/09/4503-0351©2009 Springer Science+Business Media, Inc.
351

R–CH=CH–Y
N
Y
N
N
+
N
+
N
N
–
Z
Z
Z
1a,d
2a,d
R
3a–d
O
O
O
1, 2 a Z = Ph, d Z = OEt; 3 a R = Z = Ph, Y = COPh, b R = H, Z = Ph, Y = CN,
c R = H, Z = OEt, Y = COMe, d R = H, Z = OEt, Y = CN
N
O
2a
N
Ph
1a
Ph
O
N
N
4
Oxidation of compounds 3a-d gave a quantitative yield of the previously unknown 4-(2-quinolinyl)-
pyrrolo[1,2-a]quinolines 5a-d.
MnO2
C6H6
3a–d
N
Y
N
Z
R
5a–d
O
3, 5 a R = Z = Ph, Y = COPh, b R = H, Z = Ph, Y = CN, c R = H, Z = OEt,
Y = COMe, d R = H, Z = OEt, Y = CN
The next part of our work was related to the synthesis of the previously unknown 4-(2-quinolyl)-
imidazo[1,2-a]quinolines 6a-c from the biquinolinium salts 1a-c. We have shown that these compounds can be
prepared in quantitative yield by reaction of salts 1a-c with hydroxylamine in AcOH.
NH2OH
N
N
+
N
AcOH
Z
Z
Y
N
N
Br
O
1a–c
Y
6a–c
1, 6 a Z = Y = H, b Z = NO2, Y = H, c Z = NO2, Y = Cl
352

Reduction of the nitro derivatives 6b,c with hydrazine on Raney nickel in alcohol gave a quantitative
yield of the amines 7a,b (see Experimental).
EXPERIMENTAL
1H NMR spectra were recorded on a Bruker DRX-500 instrument (500 MHz) and 13C NMR spectra on a
Bruker AM-300 (75 MHz) using TMS as internal standard. Monitoring of the reaction course and the purity of
the compounds synthesized was performed on Silufol UV-254 plates using the solvent system ethyl acetate–
petroleum ether (1:1).
Synthesis of 4-(2-Quinolinyl)-1,2,3,3a-tetrahdropyrrolo[1,2-a]quinolines by a 1,3-Dipolar Cyclo-
addition Reaction (General Methods). A. A mixture of the corresponding 1'-R-3'-(2-quinolyl)quinolinium
halide (2 mmol), the dipolarophile (2.4 mmol), and triethylamine (0.5 ml) in methylene chloride (10 ml) was
stirred for 2 h at ~ 20ºC, chloroform was added (30 ml), washed with water (3×20 ml), and the solvent was
evaporated. The red-yellow crystals or oil obtained were crystallized from benzene or benzene and hexane. The
residue insoluble in benzene during crystallization was compound 4. It could be purified by washing the residue
with benzene (2×20 ml).
B. A mixture of the corresponding 1'-R-3'-(2-quinolyl)quinolinium halide (2 mmol), the dipolarophile
(2.4 mmol), and sodium acetate (0.9 g, 5 mmol) in glacial acetic acid (10 ml) was stirred at ~ 20ºC for 1 h,
poured into water (50 ml), neutralized with 25% ammonia solution, extracted with chloroform (3×20 ml), and
the solvent was evaporated. The red-yellow crystals or oil were crystallized from benzene or benzene and
hexane.
1,3-Dibenzoyl-2-phenyl-4-(2-quinolyl)-1,2,3,3a-tetrahydropyrrolo[1,2-a]quinoline (3a) was prepared
from 1'-phenacyl-3'-(2-quinolyl)quinolinium bromide and the chalcone. By method A the yield was 0.95 g (82%)
and by method B 1.02 g (88%); mp 187-188ºC (benzene). 1H NMR spectrum (CDCl3), δ, ppm (J, Hz): 4.24 (1Н,
dd, J1,2 = 9.75, J2,3 = 2.2, Н-2); 5.35 (1Н, dd, J2,3 = 2.2, J3,3a = 5.55, H-3); 6.11 (1Н, d, J1,2 = 9.75, Н-1); 6.19 (1Н, d,
J8,9 = 8.0, Н-9); 6.59 (1Н, dd, J6,7 = 7.4, J7,8 = 7.3, Н-7); 6.72 (2Н, m, Н-8,4 (2-C6H5)); 6.88 (1Н, d, J3,3a = 5.5, H-3a);
6.95 (1Н, d, J6,7 = 7.4, Н-6); 7.06 (1Н, s, Н-5); 7.15 (4Н, m, H-2,3,5,6 (2-C6H5)); 7.2-7.4 (8Н, m, H-3,4,5
(1-COC6H5), H-2,3,4,5,6 (3-COC6H5)); 7.42 (1Н, dd, J5',6' = 8.1, J6',7' = 7.1, Н-6'); 7.45 (1Н, d, J3',4' = 9.0, Н-3'); 7.59
(1H, dd, J6',7' = 7.1, J7',8' = 8.2, Н-7'); 7.66 (1Н, d, J5',6' = 8.1, Н-5'); 7.75 (1Н, d, J7',8' = 8.2, Н-8'); 7.78 (2Н d, J = 7.8,
H-2,6 (1-COC6H5)); 7.82 (1Н, d, J3',4' = 9.0, Н-4'). 13C NMR spectrum (DMSO-d6), δ, ppm: 48.90 (1C); 56.90 (1C);
64.03 (1C); 68.04 (1C); 109.04 (1C); 116.40 (1C); 116.93 (1C); 117.53 (1C); 119.66 (1C); 126.26 (1C); 126.52
(1C); 126.74 (1C); 126.93 (1C); 127.05 (1C); 127.29 (2C); 127.63 (2C); 127.72 (2C); 127.90 (1C); 128.06 (2C);
128.12 (1C); 128.26 (1C); 128.39 (1C); 128.74 (2C); 129.08 (1C); 130.35 (1C); 131.75 (1C); 132.74 (1C); 135.24
(1C); 135.94 (1C); 136.74 (1C); 143.16 (1C); 146.24 (1C); 154.41 (1C); 198.79 (1C); 200.64 (1C). Found, %:
C 84.65; H 5.11; N 4.73. C41H30N2O2. Calculated, %: C 84.51; H 5.19; N 4.81.
1-Benzoyl-3-cyano-4-(2-quinolyl)-1,2,3,3a-tetrahydropyrrolo[1,2-a]quinoline (3b) was prepared from
1'-phenacyl-3'-(2-quinolyl)quinolinium bromide and acrylonitrile. By method A the yield was 0.62 g (72%) and by
method B 0.78 g (91%); mp 252-253ºC (benzene and hexane). 1H NMR spectrum (DMSO-d6), δ, ppm (J, Hz): 2.34
(1Н, ddd, Jhet = 13.3, J2Ha3 = 7.45, J2Ha1 = 9.0, 2-CHaHb); 2.87 (2Н, ddd, Jhet = 13.3, J2Hb3 = 6.8, J2Hb1 = 7.75,
2-CHaHb); 4.58 (1Н, ddd, J2Ha3 = 7.45, J2Hb3 = 6.8, J3,3a = 4.3, H-3); 5.56 (1Н, d, J3,3a = 4.3, Н-3a); 5.74 (1H, dd,
J2Ha1 = 9.0, J2Hb-1 = 7.75, Н-1); 6.18 (1Н, d, J8,9 = 7.8, Н-9); 6.65 (1Н, dd, J7,8 = 7.4, J6,7 = 7.5, Н-7); 7.05 (1Н, dd,
J7,8 = 7.4, J8,9 = 7.8, Н-8); 7.21 (1Н, d, J6,7 = 7.5, Н-6); 7.59 (1Н, dd, J5',6' = 7.8, J6',7' = 7.7, Н-6'); 7.63 (2Н, t, J = 7.8,
H-3,5 (C6H5)); 7.74 (2Н, m, Н-7',4 (C6H5)); 7.76 (1Н, s, Н-5); 7.96 (1Н, d, J5',6' = 7.8, Н-5'); 7.99 (3H, d, J7',8' = 8.1,
13
Н-8'); 8.13 (1Н, d, J3',4' = 8.7, Н-3'); 8.19 (2Н, d, J = 7.8, H-2,6 (C6H5)); 8.37 (1Н, d, J3',4' = 8.7, Н-4'). C NMR
spectrum (DMSO-d6), δ, ppm: 31.64 (1C); 35.71 (1C); 60.92 (1C); 62.93 (1C); 109.71 (1C); 117.14 (1C); 117.53
(1C); 119.51 (1C); 120.44 (1C); 126.39 (1C); 126.73 (1C); 127.57 (1C); 128. 61 (2C); 128.73 (1C); 128.79 (1C);
353

128.96 (2C); 129.33 (1C); 129.59 (1C); 129.75 (1C); 130.87 (1C); 133.85 (1C); 134.16 (1C); 136.04 (1C); 142.50
(1C); 146.81 (1C); 154.39 (1C); 197.72 (1C). Found, %: C 81.61; H 4.89; N 9.77. C29H21N3O. Calculated, %:
C 81.48; H 4.95; N 9.83.
3-Acetyl-1-ethoxycarbonyl-4-(2-quinolyl)-1,2,3,3a-tetrahydropyrrolo[1,2-a]quinoline (3c) was
prepared from 1'-(2-ethoxy-2-oxoethyl)-3'-(2-quinolyl)quinolinium iodide and methyl vinyl ketone. Using
method A the yield was 0.47 g (57%) and method B 0.71 g (86%); mp 143-144ºC (benzene and hexane).
1H NMR spectrum, (CDCl3), δ, ppm (J, Hz): 1.27 (3H, t, J = 7.2, CH2CH3); 1.59 (3Н, s, CH3); 2.09 (2Н, ddd,
Jhet = 13.35, J2Ha3 = 6.8, J2Ha1 = 7.7, 2-CHaHb); 2.39 (2Н, ddd, Jhet = 13.35, J2Hb3 = 7.5, J2Hb1 = 9.0, 2-CHaHb);
4.22 (2Н, t, J = 7.2, СН2СН3); 4.28 (1Н, ddd, J2Ha3 = 6.8, J2Hb3 = 7.5, J3,3a = 4.3, H-3); 4.48 (1H, dd, J2Ha1 = 7.7,
J2Hb1 = 9.0, Н-1); 5.68 (1Н, d, J3,3a = 4.3, Н-3a); 6.27 (1Н, d, J8,9 = 7.8, Н-9); 6.58 (1Н, dd, J7,8 = 7.4, J6,7 = 7.5,
Н-7); 7.07 (1H, dd, J7,8 = 7.4, J8,9 = 7.8, H-8); 7.09 (1H, d, J6,7 = 7.5, H-6); 7.58 (1Н, s, Н-5); 7.59 (1Н, dd,
J
J
5',6' = 7.8, J6',7' = 7.7, Н-6'); 7.79 (1Н, dd, J6',7' = 7.7, J7',8' = 8.2, Н-7'); 7.98 (1Н, d, J5',6' = 7.8, Н-5'); 8.02 (1Н, d,
7',8' = 8.2, H-8'); 8.10 (1Н, d, J3',4' = 8.7, Н-3'); 8.38 (1Н, d, J3',4' = 8.7, Н-4'). Found, %: C 75.82; H 5.81; N 6.77.
C26H24N2O3. Calculated, %: C 75.71; H 5.86; N 6.79.
3-Cyano-1-ethoxycarbonyl-4-(2-quinolyl)-1,2,3,3a-tetrahydropyrrolo[1,2-a]quinoline (3d) was
prepared from 1'-(2-ethoxy-2-oxoethyl)-3'-(2-quinolyl)quinolinium iodide and acrylonitrile. Yield by method A
0.54 g (68%) and by method B 0.7 g (89%); mp 178-179ºC (benzene and hexane). 1H NMR spectrum (CDCl3),
δ, ppm (J, Hz): 1.35 (3H, t, J = 7.2, CH2CH3); 2.49 (1Н, ddd, Jhet = 13.3, J2Ha3 = 7.45, J2Ha1 = 9.0, 2-CHaHb);
2.71 (1Н, ddd, Jhet = 13.3, J2Hb3 = 6.8, J2Hb1 = 7.75, 2-CHaHb); 4.29 (2H, q, J = 7.2, CH2CH3); 4.58 (1Н, ddd,
J2Ha3 = 7.45, J2Hb3 = 6.8, J3,3a = 4.3, H-3); 4.59 (1H, dd, J2Ha1 = 9.0, J2Hb1 = 7.75, Н-1); 5.78 (1Н, d, J3,3a = 4.3,
Н-3a); 6.39 (1Н, d, J8,9 = 7.8, Н-9); 6.71 (1Н, dd, J7,8 = 7.4, J6,7 = 7.5, Н-7); 7.11 (1Н, dd, J6,8 = 1.6, J6,7 = 7.5,
Н-6); 7.15 (1Н, dd, J7,8 = 7.4, J8,9 = 7.8, Н-8); 7.40 (1Н, s, Н-5); 7.52 (1Н, dd, J5',6' = 7.8, J6',7' = 7.7, Н-6'); 7.72
(1Н, dd, J6',7' = 7.7, J7',8' = 8.1, Н-7'); 7.75 (1Н, d, J5',6' = 7.8, Н-5'); 7.88 (1Н, d, J3',4' = 8.7, Н-3'); 7.97 (3H, d,
J
7',8' = 8.1, Н-8'); 8.14 (1Н, d, J3',4' = 8.7, Н-4'). Found, %: C 76.06; H 5.30; N 10.57. C25H21N3O2. Calculated, %:
C 75.93; H 5.35; N 10.63.
7,14-Dibenzoyl-6,13-di(2-quinolyl)-6a,7,13a,14-tetrahydro-7a,14a-diazadibenzo[a,h]anthracene
(4)
was synthesized as the side product in the reaction of 1'-phenacyl-3'-(2-quinolyl)quinolinium bromide and
acrylonitrile, using method A the yield was 0.31 g (21%); mp 294-296ºC (alcohol). 1H NMR spectrum (DMSO-d6),
δ, ppm (J, Hz): 6.39 (2H, d, J = 3.65, H-6a,13a); 6.60 (2H, d, J = 3.65, H-7,14); 6.81 (2H, dd, J3(10),4(11) = 7.8,
J2(9),3(10) = 7.3, H-3,10); 7.05 (6H, m, H-3,5 (C6H5), H-2,10); 7.26 (2Н, s, H-5,12); 7.29 (2H, d, J3(10),4(11) = 7.8,
H-4,11); 7.36 (2H, dd, J2(9),3(10) = 7.3, J1(8),2(9) = 8.0, H-1,9); 7.47 (2H, t, J = 6.7, H-4 (C6H5)); 7.62 (6Н, m, H-2,6
(C6H5), Н-6'); 7.84 (2Н, d, J5',6' = 7.8, Н-5'); 7.93 (2H, dd, J6',7' = 7.2, J7',8' = 8.1, H-7'); 7.98 (2H, d, J7',8' = 8.1, Н-8');
8.23 (2Н, d, J3',4' = 8.45, Н-3'); 8.29 (2Н, d, J3',4' = 8.45, Н-4'). Found, %: C 83.55; H 4.81; N 7.39. C52H36N4O2.
Calculated, %: C 83.40; H 4.85; N 7.48.
Synthesis of 4-(2-Quinolinyl)pyrrolo[1,2-a]quinolines 5a-d (General Method). A mixture of the
corresponding 4-(2-quinolinyl)-1,2,3,3a-tetrahydropyrrolo[1,2-a]quinoline (1 mmol) and activated MnO2
(0.44 g, 5 mmol) in benzene (15 ml) was refluxed and the reaction was monitored by TLC (~ 3 h). The solution
was filtered hot and the precipitate was washed with hot benzene (2×10 ml). The obtained solutions were
combined and evaporated.
1,3-Dibenzoyl-2-phenyl-4-(2-quinolyl)pyrrolo[1,2-a]quinoline (5a). Yield 0.56 g (quantitative); mp
1
196-197ºC (benzene). H NMR spectrum (CDCl3), δ, ppm (J, Hz): 6.9 (5H, m, 2-C6H5); 7.15 (5Н, m, H-3,5
(1-COC6H5), H-3,4,5 (3-COC6H5)); 7.23 (2Н, d, J = 7.65, H-2,6 (3-COC6H5)); 7.36 (3Н, m, H-7,8,6'); 7.46 (4Н,
m, Н-7',2,4,6 (1-COC6H5)); 7.53 (1Н, s, Н-5); 7.66 (1Н, d, J6,7 = 7.5, Н-6); 7.69 (1Н, d, J8,9 = 7.8, Н-9); 7.76
(1Н, d, J5',6' = 7.8, Н-5'); 8.78 (3H, d, J7',8' = 8.1, Н-8'); 7.82 (1Н, d, J3',4' = 8.45, Н-3'); 8.97 (1Н, d, J3',4' = 8.45,
Н-4'). Found, %: C 85.22; H 4.48; N 4.77. C41H26N2O2. Calculated, %: C 85.10; H 4.53; N 4.84.
354

1-Benzoyl-3-cyano-4-(2-quinolyl)pyrrolo[1,2-a]quinoline (5b). Yield 0.4 g (quantitative); mp
1
236-238ºC (benzene). H NMR spectrum (CDCl3), δ, ppm (J, Hz): 7.15 (3Н, m, H-3,4,5 (C6H5)); 7.46 (2Н, d,
J = 6.8, H-2,6 (C6H5)); 7.54 (1Н, dd, J7,8 = 7.4, J6,7 = 7.5, Н-7); 7.63 (1Н, dd, J5',6'= 7.8, J6',7' = 7.7, Н-6'); 7.68
(1Н, dd, J7,8 = 7.4, J8,9 = 7.8, Н-8); 7.74 (1Н, d, J6,7 = 7.5, Н-6); 7.81 (1Н, s, Н-2); 7.83 (1Н, dd, J6',7' = 7.7,
J
J
7',8' = 8.0, Н-7'); 7.85 (1Н, s, Н-5); 7.88 (1Н, d, J8,9 = 7.8, Н-9); 7.93 (1Н, d, J5',6' = 7.8, Н-5'); 8.22 (1H, d,
7',8' = 8.0, Н-8'); 8.32 (1Н, d, J3',4' = 8.8, Н-3'); 8.39 (1Н, d, J3',4' = 8.8, Н-4'). Found, %: C 82.36; H 3.99; N 9.87.
C29H17N3O. Calculated, %: C 82.25; H 4.05; N 9.92.
3-Acetyl-1-ethoxycarbonyl-4-(2-quinolyl)pyrrolo[1,2-a]quinoline (5c). Yield 0.4 g (quantitative); mp
1
185-186ºC (benzene). H NMR spectrum (CDCl3), δ, ppm (J, Hz): 1.34 (3H, t, J = 7.1, CH2CH3); 4.42 (2H, q,
J = 7.1, CH2CH3); 1.63 (3Н, s, COCH3); 7.55 (1Н, dd, J7,8 = 7.4, J6,7 = 7.48, Н-7); 7.63 (1Н, dd, J5',6' = 7.8,
J6',7' = 7.7, Н-6'); 7.68 (1Н, dd, J7,8 = 7.4, J8,9 = 7.8, Н-8); 7.76 (1Н, d, J6,7 = 7.5, Н-6); 7.79 (1Н, s, Н-2); 7.81
(1Н, dd, J6',7' = 7.7, J7',8' = 8.0, Н-7'); 7.82 (1Н, s, Н-5); 7.88 (1Н, d, J8,9 = 7.8, Н-9); 7.92 (1Н, d, J5',6' = 7.8, Н-5');
8.22 (3H, d, J7',8' = 8.0, Н-8'); 8.37 (1Н, d, J3',4' = 8.7, Н-3'); 8.32 (1Н, d, J3',4' = 8.7, Н-4'). Found, %: C 76.57;
H 4.89; N 6.85. C26H20N2O3. Calculated, %: C 76.46; H 4.94; N 6.86.
3-Cyano-1-ethoxycarbonyl-4-(2'-quinolyl)pyrrolo[1,2-a]quinoline (5d). Yield 0.57 g (quantitative);
mp 219-220ºC (benzene). 1H NMR spectrum (CDCl3), δ, ppm (J, Hz): 1.43 (3H, t, J = 7.2, CH2CH3); 4.48 (2H,
q, J = 7.2, CH2CH3); 7.55 (1Н, dd, J7,8 = 7.4, J6,7 = 7.5, Н-7); 7.63 (1Н, dd, J5',6' = 7.8, J6',7' = 7.7, Н-6'); 7.68
(1Н, dd, J7,8 = 7.4, J8,9 = 7.8, Н-8); 7.76 (1Н, d, J6,7 = 7.5, Н-6); 7.79 (1Н, s, Н-2); 7.81 (1Н, dd, J6',7' = 7.7,
J
J
7,'8' = 8.0, Н-7'); 7.82 (1Н, s, Н-5); 7.88 (1Н, d, J8,9 = 7.8, Н-9); 7.92 (1Н, d, J5',6' = 7.8, Н-5'); 8.22 (1H, d,
7',8' = 8.0, Н-8'); 8.37 (1Н, d, J3',4' = 8.7, Н-3'); 8.38 (1Н, d, J3',4' = 8.7, Н-4'). Found, %: C 76.83; H 4.33;
N 10.69. C25H17N3O2. Calculated, %: C 76.71; H 4.38; N 10.73.
Synthesis of 4-(2-Quinolyl)imidazo[1,2-a]quinolines 6a-c (General Method). A mixture of the
corresponding salt 1a-c (1 mmol), hydroxylamine hydrochloride (0.139 g, 2 mmol), and sodium acetate (0.25 g,
3 mmol) in acetic acid (10 ml) was stirred at 55-60ºC for 3 h, cooled, water (50 ml) was added, and neutralized
with ammonia solution. The precipitate was filtered.
2-Phenyl-4-(2'-quinolyl)imidazo[1,2-a]quinoline (6a). Yield 0.36 g (quantitative); mp 137-138ºC
1
(benzene). H NMR spectrum (DMF-d7), δ, ppm (J, Hz): 7.39 (1H, t, J = 7.6, H-4 (C6H5)); 7.55 (2Н, dd,
J = 7.6, J = 7.4, H-3,5 (C6H5)); 7.65 (1H, dd, J6,7 = 10.9, J7,8 = 7.0, H-7); 7.70 (1H, dd, J6',7' = 6.6, J7',8' = 8.1,
H-7'); 7.86 (1H, dd, J8,9 = 8.5, J7,8 = 7.0, H-8); 7.88 (1H, dd, J6',7' = 6.6, J5',6' = 8.2, H-6); 8.13 (1H, d, J7',8' = 8.1,
H-8'); 8.23 (1H, d, J5',6' = 8.2, H-5'); 8.25 (2H, d, J = 7.4, H-2,6 (C6H5)); 8.28 (1H, d, J6,7 = 10.9, H-6); 8.55 (1H,
d, J8,9 = 8.5, H-9); 8.65 (1H, d, J3',4' = 8.55, H-4'); 8.87 (1Н, s, Н-5); 9.43 (1Н, s, Н-1); 9.53 (1H, d, J3',4' = 8.55,
H-3'). Found, %: C 84.18; H 4.58; N 11.24. C26H17N3. Calculated, %: C 84.07; H 4.62; N 11.31.
4-(8-Nitro-2-quinolyl)-2-phenylimidazo[1,2-a]quinoline (6b). Yield 0.41 g (quantitative); mp
1
235-237ºC (benzene). H NMR spectrum (DMSO-d6), δ, ppm (J, Hz): 7.37 (1H, t, J = 7.6, H-4 (C6H5)); 7.51
(2Н, dd, J = 7.6, J = 7.4, H-3,5 (C6H5)); 7.61 (1H, dd, J6,7 = 10.7, J7,8 = 7.0, H-7); 7.80 (1H, dd, J6',7' = 7.4,
J5',6' = 8.2, H-6'); 7.86 (1H, dd, J8,9 = 8.5, J7,8 = 7.0, H-8); 8.14 (2H, d, J = 7.4, H-2,6 (C6H5)); 8.18 (1H, d,
J6,7 = 10.7, H-6); 8.35 (1H, d, J5',6' = 8.2, H-5'); 8.37 (1H, d, J6',7' = 7.4, H-7'); 8.45 (1H, d, J8,9 = 8.5, H-9); 8.57
(1Н, s, Н-5); 8.80 (1H, d, J3',4' = 8.55, H-4'); 9.34 (1Н, s, Н-1); 9.54 (1H, d, J3',4' = 8.55, H-3'). Found, %:
C 75.18; H 3.79; N 13.41. C26H16N4O2. Calculated, %: C 74.99; H 3.87; N 13.45.
2-(4-Chlorophenyl)-4-(8-nitro-2-quinolyl)imidazo[1,2-a]quinoline (6c). Yield 0.44 g (quantitative);
mp 152-153ºC (benzene). 1H NMR spectrum (DMSO-d6), δ, ppm (J, Hz): 7.56 (2Н, d, J = 7.9, H-3,5 (Ar)); 7.62
(1H, dd, J6,7 = 10.7, J7,8 = 7.0, H-7); 7.81 (1H, dd, J6',7' = 7.4, J5',6' = 8.2, H-6'); 7.86 (1H, dd, J8,9 = 8.5, J7,8 = 7.0,
H-8); 8.18 (1H, d, J6,7 = 10.7, H-6); 8.24 (2H, d, J = 7.9, H-2,6 (Ar)); 8.35 (1H, d, J5',6' = 8.2, H-5'); 8.38 (1H, d,
J6',7' = 7.4, H-7'); 8.46 (1H, d, J8,9 = 8.5, H-9); 8.57 (1Н, s, Н-5); 8.82 (1H, d, J3',4' = 8.55, H-4'); 9.34 (1Н, s, Н-1);
9.53 (1H, d, J3',4' = 8.55, H-3'). Found, %: C 69.41; H 3.31; N 12.36. C26H15ClN4O2. Calculated, %: C 69.26;
H 3.35; N 12.43.
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Reduction of Compounds 6b,c (General Method). Hydrazine hydrate (85%, 0.5 g, 10 mmol) was added to
a mixture of the corresponding compound 6 (1 mmol) and Raney nickel (0.5 g) in alcohol (50 ml). The product was
stirred at 50ºC for 3h with TLC monitoring, filtered, the alcohol evaporated, and the residue was treated with water
(50 ml) and then extracted with benzene (3×30 ml). The solvent was evaporated to give yellow-green crystals.
4-(8-Amino-2-quinolyl)-2-phenylimidazo[1,2-a]quinoline (7a) Yield 0.38 g (quantitative); mp
1
215-217ºC (benzene). H NMR spectrum (DMSO-d6), δ, ppm (J, Hz): 6.30 (2H, br. s, NH2); 6.91 (1H, dd,
J6',7' = 7.6, J5',7' = 1.0, H-7'); 7.11 (1H, dd, J5',6' = 7.9, J5',7' = 1.0, H-5'); 7.34 (1H, dd, J6',7' = 7.6, J5',6' = 7.9, H-6'); 7.37
(1H, t, J = 7.6, H-4 (C6H5)); 7.53 (2Н, dd, J = 7.6, J = 7.3, H-3,5 (C6H5)); 7.63 (1H, dd, J6,7 = 10.9, J7,8 = 7.0, H-7);
7.82 (1H, dd, J8,9 = 8.6, J7,8 = 7.0, H-8); 8.17 (2H, d, J = 7.4, H-2,6 (C6H5)); 8.26 (1H, d, J6,7 = 10.9, H-6); 8.39 (1H,
d, J3',4' = 8.55, H-4'); 8.44 (1H, d, J8,9 = 8.6, H-9); 9.13 (1Н, s, Н-5); 9.35 (1Н, s, Н-1); 9.50 (1H, d, J3',4' = 8.55, H-3').
Found, %: C 80.92; H 4.63; N 14.45. C26H18N4. Calculated, %: C 80.81; H 4.69; N 14.50.
4-(8-Amino-2-quinolyl)-2-(4-chlorophenyl)imidazo[1,2-a]quinoline (7b). Yield 0.42 g (quantitative);
1
mp 133-135ºC (benzene). H NMR spectrum (DMSO-d6), δ, ppm (J, Hz): 5.12 (2H, br. s, NH2); 6.99 (1H, dd,
J6',7' = 7.6, J5',7' = 1.0, H-7'); 7.18 (1H, dd, J5',6' = 7.9, J5',7' = 1.0, H-5'); 7.37 (1H, dd, J6',7' = 7.6, J5',6' = 7.9, H-6');
7.54 (2Н, d, J = 7.9, H-3,5 (Ar)); 7.65 (1H, dd, J6,7 = 10.9, J7,8 = 7.0, H-7); 7.88 (1H, dd, J8,9 = 8.6, J7,8 = 7.0,
H-8); 8.26 (1H, d, J6,7 = 10.9, H-6); 8.29 (2H, d, J = 8.0, H-2,6 (Ar)); 8.45 (1H, d, J8,9 = 8.6, H-9); 8.59 (1H, d,
J3',4' = 8.55, H-4'); 8.88 (1Н, s, Н-5); 9.41 (1Н, s, Н-1); 9.52 (1H, d, J3',4' = 8.55, H-3'). Found, %: C 74.34;
H 4.01; N 13.27. C26H17ClN4. Calculated, %: C 74.19; H 4.07; N 13.31.
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