4-hydroxy-2-quinolones 172*. Synthesis and structure of 4,3′-spiro[(6-allyl-2-amino- 5-oxo-5,6-dihydro-4h-pyrano- [3,2-c]quinoline-3-carbo- nitrile)-2′-oxindole]

Article abstract of DOI:10.1007/s10593-010-0454-9

A three-component condensation of 1-allyl-4-hydroxy-2-oxo-1,2- dihydroquinoline, isatin, and malononitrile gave a satisfactory yield of 4,3′-spiro[(6-allyl-2-amino-5-oxo-5,6-dihydro-4H-pyrano-[3,2-c] quinoline-3-carbonitrile)-2′-oxindole], which structure was confirmed by X-ray analysis.

Full text of DOI:10.1007/s10593-010-0454-9

Chemistry of Heterocyclic Compounds, Vol. 45, No. 12, 2009
4-HYDROXY-2-QUINOLONES
172*. SYNTHESIS AND STRUCTURE
OF 4,3'-SPIRO[(6-ALLYL-2-AMINO-
5-OXO-5,6-DIHYDRO-4H-PYRANO-
[3,2-c]QUINOLINE-3-CARBO-
NITRILE)-2'-OXINDOLE]
I. V. Ukrainets1**, R. G. Red'kin1, L. V. Sidorenko1, and A. V. Turov2
A
three-component condensation of 1-allyl-4-hydroxy-2-oxo-1,2-dihydroquinoline, isatin, and
malononitrile gave a satisfactory yield of 4,3'-spiro[(6-allyl-2-amino-5-oxo-5,6-dihydro-4H-pyrano-
[3,2-c]quinoline-3-carbonitrile)-2'-oxindole], which structure was confirmed by X-ray analysis.
Keywords: 4-hydroxy-2-oxo-1,2-dihydroquinoline, isatin, malononitrile, pyrano[3,2-c]quinoline,
spiro[indole-3,4'-pyran], X-ray structural analysis.
Derivatives of 4-hydroxy-2-quinolone annelated by the pyran fragment along the c edge have long
attracted the attention of synthetic chemists and other investigators. Such an interest is primarily because a
2H-pyrano[3,2-c]quinolin-5-one ring forms the basis of a series of natural alkaloids isolated from the plant
family Rutaceae, including veprisine, flindersine, haplamine, paraensidimerine, and vepridimerine [2-5].
Amongst this series there are compounds having photochromic properties [6] that are able to block Ca2+
channels in cell membranes [7] or K+ channels in thymocytes [8].
All of the synthetic methods for building pyrano[3,2-c]quinolin-5-one systems are based on the Michael
addition of 4-hydroxy-2-quinolones to α,β-unsaturated carbonyl compounds [9-12]. The same principle was
used by us in the preparation and study of the previously unreported 4-hydroxy-2-quinolones annelated by a
spiro[indole-3,4'-pyran] ring.
Practically the preparation of these types of heterocyclic systems relates to different synthetic schemes,
which we have discussed for the structurally closely related 4-hydroxycoumarin. One of the these involves an
initial condensation of isatin with malononitrile after which 2-(2-oxoindolin-3-ylidene)malononitrile is
introduced into a reaction with 4-hydroxycoumarin [13]. It should be noted immediately that such a method
_______
* For Communication 171 see [1].
** To whom correspondence should be addressed, e-mail: uiv@kharkov.ua.
1National University of Pharmacy, Kharkiv 61002, Ukraine.
2Taras Shevchenko National University, Kiev 01033, Ukraine, e-mail: nmrlab@uiv.kiev.ua.
__________________________________________________________________________________________
Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1834-1841, December, 2009.
Original article submitted December 18, 2008.
1478
0009-3122/09/4512-1478©2009 Springer Science+Business Media, Inc.

does not give good results and is hence used as a counter synthesis. A somewhat different scheme has some
preparative value and consists of a three component condensation in which isatin 1, malononitrile 2, and
4-hydroxycoumarin are simultaneously introduced into the reaction and which, moreover, is considerably easier
to carry out [13-15].
Experiments carried out by us have shown that exchange of 4-hydroxycoumarin for an aza analog, in
particular 1-allyl-4-hydroxy-2-oxo-1,2-dihydroquinoline (3) does not prove to have any kind of effect on the
course of the reaction and thus, it gives 4,3'-spiro[(6-allyl-2-amino-5-oxo-5,6-dihydro-4H-pyrano-
[3,2-c]quinoline-3-carbonitrile)-2'-oxindole] (4).
OH
OH
O
COOH
O
–CO2
CN
CN
O
+
+
N
N
O
N
H
1
2
3
5
H2N+
N
O
N
NH2
–
O
O
N
O
NH
NH
O
O
N
4
4a
The 4-hydroxy-2-oxo-1,2-dihydroquinoline-3-carboxylic acids, including the 1-allyl-substituted analog
5, are very liable to decarboxylation [16], hence can be used in the synthesis of the pyrano-[3,2-c]quinolines 4. It
is clear the separation of the intermediate 3H-derivatives 3 is not needed.
Fig. 1. The crystalline structure of the pyranoquinoline 4 ethanol solvate molecule.
1479

TABLE 1. Bond Lengths (l) in the Structure of the Pyranoquinoline 4
Ethanol Solvate Molecule
Bond
N(1)–C(9)
l, Å
Bond
N(1)–C(1)
l, Å
1.388(2)
1.476(2)
1.403(2)
1.157(2)
1.365(2)
1.223(2)
1.412(2)
1.390(2)
1.397(2)
1.350(2)
1.508(2)
1.424(2)
1.519(2)
1.383(2)
1.385(3)
1.382(3)
1.476(3)
1.430(1)
1.540(1)
1.401(2)
1.353(2)
1.340(2)
1.237(2)
1.386(2)
1.397(2)
1.378(2)
1.372(2)
1.433(2)
1.455(2)
1.359(2)
1.526(2)
1.557(2)
1.384(3)
1.376(3)
1.370(2)
1.274(3)
1.430(1)
1.539(1)
N(1)–C(20)
N(2)–C(14)
N(4)–C(23)
O(2)–C(10)
O(3)–C(13)
C(1)–C(6)
N(2)–C(13)
N(3)–C(10)
O(1)–C(9)
O(2)–C(7)
C(1)–C(2)
C(2)–C(3)
C(3)–C(4)
C(4)–C(5)
C(5)–C(6)
C(6)–C(7)
C(7)–C(8)
C(8)–C(9)
C(8)–C(12)
C(11)–C(23)
C(12)–C(19)
C(14)–C(19)
C(15)–C(16)
C(17)–C(18)
C(20)–C(21)
O(1S)–C(2SA)
C(1SA)–C(2SA)
C(10)–C(11)
C(11)–C(12)
C(12)–C(13)
C(14)–C(15)
C(16)–C(17)
C(18)–C(19)
C(21)–C(22)
O(1S)–C(2SB)
C(1SB)–C(2SB)
TABLE 2. Valence Angles (ω) in the Pyranoquinoline 4 Ethanol Solvate
Molecule
Angle
C(9)–N(1)–C(1)
ω, deg
Angle
ω, deg
123.0(1)
119.6(1)
118.9(1)
119.1(1)
120.2(2)
119.3(2)
119.2(1)
117.7(1)
123.2(1)
119.2(1)
117.9(1)
121.4(1)
126.2(1)
121.9(1)
123.5(1)
114.4(1)
110.6(1)
101.1(1)
127.3(1)
107.4(1)
109.3(2)
117.0(2)
120.9(2)
120.1(2)
109.2(1)
127.5(2)
113.9(3)
C(9)–N(1)–C(20)
C(13)–N(2)–C(14)
C(2)–C(1)–N(1)
117.3(1)
112.3(1)
121.9(1)
119.1(1)
121.0(2)
121.2(2)
123.1(1)
122.9(1)
113.9(1)
122.9(1)
120.8(1)
117.8(1)
111.9(1)
119.2(1)
117.2(1)
108.6(1)
112.7(1)
109.3(1)
125.3(1)
122.0(2)
128.7(2)
121.3(2)
118.7(2)
130.7(1)
114.1(1)
178.2(2)
98.3(2)
C(1)–N(1)–C(20)
C(10)–O(2)–C(7)
C(2)–C(1)–C(6)
N(1)–C(1)–C(6)
C(3)–C(2)–C(1)
C(2)–C(3)–C(4)
C(5)–C(4)–C(3)
C(4)–C(5)–C(6)
C(5)–C(6)–C(1)
C(5)–C(6)–C(7)
C(1)–C(6)–C(7)
C(8)–C(7)–O(2)
C(8)–C(7)–C(6)
O(2)–C(7)–C(6)
C(7)–C(8)–C(9)
C(7)–C(8)–C(12)
O(1)–C(9)–N(1)
C(9)–C(8)–C(12)
O(1)–C(9)–C(8)
N(1)–C(9)–C(8)
N(3)–C(10)–C(11)
C(11)–C(10)–O(2)
C(10)–C(11)–C(12)
C(8)–C(12)–C(19)
C(19)–C(12)–C(11)
C(19)–C(12)–C(13)
O(3)–C(13)–N(2)
N(2)–C(13)–C(12)
C(19)–C(14)–N(2)
C(14)–C(15)–C(16)
C(16)–C(17)–C(18)
C(18)–C(19)–C(14)
C(14)–C(19)–C(12)
C(22)–C(21)–C(20)
O(1S)–C(2SA)–C(1SA)
N(3)–C(10)–O(2)
C(10)–C(11)–C(23)
C(23)–C(11)–C(12)
C(8)–C(12)–C(11)
C(8)–C(12)–C(13)
C(11)–C(12)–C(13)
O(3)–C(13)–C(12)
C(19)–C(14)–C(15)
C(15)–C(14)–N(2)
C(17)–C(16)–C(15)
C(19)–C(18)–C(17)
C(18)–C(19)–C(12)
N(1)–C(20)–C(21)
N(4)–C(23)–C(11)
O(1S)–C(2SB)–C(1SB)
1480

The results of the X-ray analysis carried out have shown the pyrano[3,2-c]quinoline 4 is isolated from
the reaction mixture as a 1:1 solvate with ethanol (see Fig. 1 and Tables 1 and 2). Moreover, the solvated ethanol
molecule is randomized in two positions with equal probability population. The quinolone fragment and the
O(1) and C(20) atoms lie in a single plane within the accuracy of 0.02 Å. The 4H-pyran ring occurs in a strongly
flattened boat conformation (folding parameters [17]: S = 0.17, θ = 71.9º, ψ = 2.8º). The deviations of atoms
O(2) and C(12) from the mean square plane of the remaining ring atoms are -0.07 and -0.14 Å, respectively. The
spiro linked fragments are twisted virtually perpendicularly to one another (torsional angle C(7)–C(8)–C(12)–
C(19) 113.2(2)º). The non-equivalence of the bonds O(2)–C(7) 1.386(2) and O(2)–C(10) 1.365(2) Å in the
dihydropyran ring should be noted and this is also seen in other spiro conjugate pyrans [18]. At the same time, in
4-alkyl- and 4-aryl-substituted derivatives this effect appeared to be non-typical [19, 20].
The powerful repulsion between the atoms of the allyl substituent and the quinolone fragment
(shortened intramolecular contacts H(2)···C(20) 2.53 (the sum of van der Waal radii [21] 2.87), H(2)···H(20a)
2.07 (2.34), H(20a)···C(2) 2.59 (2.87), and H(20b)···O(1) 2.32 Å (2.46 Å)) leads to the lengthening of the N(1)–
C(9) bond to 1.388(2) and N(1)–C(1) bond to 1.401(2) when compared with their mean values [22] of 1.353 and
1.371 Å, respectively. The vinyl part of the allyl substituent is placed virtually perpendicularly to the plane of
the quinolone ring and this substituent occurs in a conformation close to syn-periplanar (torsional angles C(9)–
N(1)–C(20)–C(21) 96.1(2)º and N(1)–C(20)–C(21)–C(22) -11.3(3)º, respectively).
The pyrano[3,2-c]quinoline 4 molecules are mutually bonded through the bridging ethanol molecules
via the intermolecular hydrogen bonds N(2)–H(2N)…O(1s)' (-1-x, 2-y, -z) H···O 1.97 Å, N–H···O 175º and
O(1s)–H(1sa)···N(4)' H···N 2.10 Å, O–H···N 164º to form dimers. In the crystal the complexes are arranged in
infinite chains along the crystallographic (0 1 0) axis with the intermolecular bonds N(3)–H(3Na)···O(1s)' (-x,
2-y, -z) H···O 2.13 Å, N–H···O 165º and N(3)–H(3Nb) ···O(1)' (1+x, y, z) H···O 2.25 Å, N–H···O 158º.
The X-ray analysis carried out not only confirmed the structure of the pyrano[3,2-c]quinoline 4
synthesized but further demonstrated its considerable complexity thus presenting a particular interest for NMR
investigation. Since the molecule contains two identical aromatic proton spin systems there exists some
difficulty in interpretation. The most reliable assignment of these signals can be made by measuring the 2D
COSY and NOESY spectra. Hence the COSY spectrum showed that a doublet for one of the aromatic protons
having a chemical shift of 7.48 ppm was close in space to the allyl methylene substituent absorbing at 4.72 ppm.
From the compound formula it follows that this can only occur in the quinolone fragment found in a peri
position to the N-allyl substituent. Hence all of the signals spin related to the signal at 7.48 ppm were assigned
to the quinolone molecular fragment and could be located by correlation in the COSY spectrum. It was found
that all of the aromatic protons in the quinolone ring spin system absorb at a lower field than the signals in the
indoline fragment. The cross peak coordinates in the COSY spectrum allow an assignment of all of the proton
signals.
The 13C NMR spectrum of the pyrano[3,2-c]quinoline 4 solvate showed the presence of the quaternary
spiro atom carbon at 48.8 ppm and a signal for the allyl group methylene signal at 44.4 ppm. The carbon atoms
of the ethanol solvate methyl and methylene groups appeared as signals at 19.3 and 56.7 ppm, respectively.
Assignment of the signals in the aromatic part of the 13C NMR spectrum can be readily made on the basis of the
analysis of cross peaks in the 2D HMQC and HMBC spectra and are given in Table 3. Interpretation of the
majority of the quaternary carbon atoms was carried out from the cross peaks due to spin interactions through
three chemical bonds. The assignments are given in Scheme 1 with the most important HMBC correlations
indicated by arrows.
In the HMBC spectrum correlations were only absent for two carbon atoms at 107.0 and 118.4 ppm. The
first of the these corresponds to the bridging C(4a) atom and the second to the carbon of the nitrile group.
A somewhat unusual behavior was seen for the pyrano[3,2-c]quinoline 4 when deuterated trifluoroacetic
acid was added to its solution in DMSO-d6. No change that is usually observed in such examples was seen either
in the proton or carbon spectrum. Even the active NH and NH2 protons did not undergo deuterium exchange and
remained in the spectrum.
1481

1
TABLE 3. The Complete List of Heteronuclear H–13C Correlations
Found for the Pyranoquinoline 4 Ethanol Solvate Molecule
Position of the cross peaks in the 13C measurement
1Н signals, δ, ppm
НМQC
HMBC
10.52
8.06
7.71
7.48
7.40
7.15
7.02
6.85
6.81
5.75
5.05
4.84
4.72
—
178.5; 143.1; 135.0; 48.8
152.4; 138.5; 132.9
138.5; 116.1; 123.2
159.6; 152.4; 123.0; 113.2; 57.9
116.1; 113.2
123.2
132.9
116.1
123.0
129.0
124.1
122.4
110.0
132.9
117.2
117.2
44.4
143.1; 124.1
143.1; 129.0; 48.8
135.0; 110.0
135.0; 122.4
44.4
44.4
132.9; 44.4
159.2; 138.5; 132.9; 117.2
7.48
NH2+
118.1
159.6
CN
-
8.06
O
H
O
57.9
178.5
10.52
123.2
48.8
7.40
152.4
H
N
H
135.0
143.1
110.0
107.0
159.2
123.0
132.9
113.2
138.5
7.02
H
124.1
H
6.81
129.0
122.4
H
N
O
H
H
6.85
116.1
7.71
7.15
44.4
H
H
5.75
7.48
H
132.9
H
4.72
117.2
H
H
4.84
5.05
EXPERIMENTAL
1
The H NMR and 13C NMR spectra of the pyranoquinoline 4 solvate, COSY 2D 1H NMR experiments,
the NOESY-2D homonuclear Overhauser effect spectroscopy, and the heteronuclear HMQC and HMBC spectra
were recorded on a Varian Mercury-400 spectrometer (400 and 100 MHz, respectively). All of the 2D
experiments were carried out with gradient selection of useful signals. The mixing times in the pulse sequences
1
2-3
were respectively JCH = 140 and
J
CH
= 8 Hz. The number of increments in the COSY and HMQC
1482

experiments was 128 and in the HMBC spectrum 400. The mixing time in the NOESY-2D experiment was 500
ms. In all cases the solvent was DMSO-d6 and the internal standard TMS.
1-Allyl-4-hydroxy-2-oxo-1,2-dihydroquinoline (3) and 1-allyl-4-hydroxy-2-oxo-1,2-dihydroquinoline-
3-carboxylic acid (5) were prepared by the known methods [16] and [23], respectively.
Solvate
of
4,3'-Spiro[(6-allyl-2-amino-5-oxo-5,6-dihydro-4H-pyrano[3,2-c]quinoline-3-carbo-
nitrile)-2'-oxindole] (4) with Ethanol. A mixture of 1-allyl-4-hydroxy-2-oxo-1,2-dihydroquinoline 3 (2.01 g,
0.01 mol), isatin 1 (1.47 g, 0.01 mol), malononitrile 2 (0.66 g, 0.01 mol), and triethanolamine (1.3 ml, 0.01 mol)
in ethanol (20 ml) was refluxed for 2 h, cooled, and placed in a freezer at -5ºC for 24 h. The precipitated solvate
crystals of the pyranoquinoline 4 with ethanol were filtered off, washed with hot hexane, and dried. Yield 2.56 g
1
(58%); mp 313-315ºC (ethanol). H NMR spectrum, δ, ppm (J, Hz): 10.52 (1H, s, NH); 8.06 (1H, d, J = 7.2,
H-10); 7.71 (1H, t, J = 7.2, H-8); 7.48 (3H, m, H-7 and NH2); 7.40 (1H, t, J = 7.6, H-9); 7.15 (1H, t, J = 7.6,
H-6' indole); 7.02 (1H, d, J = 7.2, H-4' indole); 6.85 (1H, t, J = 7.6, H-5' indole); 6.81 (1H, d, J = 7.6, H-7'
indole); 5.75 (1H, m, CH=CH2); 5.05 (1H, d, J = 10.4, NCH2CH=CH cis); 4.84 (1H, d, J = 17.2, NCH2CH=CH
trans); 4.72 (2H, d, J = 2.8, NCH2); 4.39 (1H, t, J = 5.2, OH ethanol); 3.44 (2H, q, J = 5.2, CH2 ethanol);
1.06 (3H, t, J = 7.2, CH3 ethanol). 13C NMR spectrum, δ, ppm: 178.5 (O=C-2'), 159.6 (H2NC-2), 159.2 (С-5),
152.4 (C-10B), 143.1 (C-7'A), 138.5 (С-6А), 135.0 (C-3'A), 132.9 (C-8 + NCH2CH), 129.0 (C-6'), 124.1 (C-4'),
123.2 (C-10), 123.0 (C-9), 122.4 (C-5'), 118.1 (C≡N), 117.2 (NCH2CH=CH2), 116.1 (C-7), 113.2 (C-10A),
110.0 (C-7'), 107.0 (C-4A), 57.9 (C-3), 56.7 (CH3CH2OH), 48.8 (C-4), 44.4 (NCH2), 19.3 (CH3CH2OH). Found,
%: C 67.98; H 5.14; N 12.57. C23H16N4O3.EtOH. Calculated, %: C 67.86; H 5.01; N 12.66.
When 1-allyl-4-hydroxy-2-oxo-1,2-dihydroquinoline-3-carboxylic acid (5) is used as starting material, it
is treated as follows. Acid 5 (2.45 g, 0.01 mol) was added in small portions to refluxing DMF (5 ml). The poorly
soluble acid rapidly decarboxylated to become the readily soluble 3H-derivative 3, which was used without
separation in the subsequent synthesis as described in the method above.
X-ray Structural Analysis. 1:1 Crystals of the pyranoquinoline 4 with ethanol are triclinic (ethanol). At
20ºC: a = 8.665(1), b = 10.364(2), c = 13.294(2) Å, α = 80.94(1)º, β = 83.52(1)º, γ = 71.69(2)º, V = 1116.7(3) Å3,
–
M = 42.47, Z = 2, space group P , dcalc = 1.316 g/cm3, µ(MoKα) = 0.091 mm-1, F(000) = 464. The parameters for
1
r
the unit cell and intensities of 12,468 reflections (3916 independent with Rint = 0.040) were measured on an Xcalibur-
3 diffractomer (MoKα radiation, CCD detector, graphite monochromator, ω-scanning to 2θmax = 50º).
The structure was solved by a direct method using the SHELXTL program package [24]. The positions
of the hydrogen atoms were revealed from electron density difference synthesis and refined using the "riding"
model with Uiso = nUeq (n = 1.5 for methyl groups and n = 1.2 for remaining hydrogen atoms). Hydrogen atoms
taking part in the formation of hydrogen bonds were refined isotropically. The structure was refined via F2 full-
matrix least-squares analysis in the anisotropic approximation for non-hydrogen atoms to wR2 = 0.110 for 3831
reflections (R1 = 0.043 for 1757 reflections with F > 4σ(F) and S = 0.810). The complete crystallographic
information was placed in the Cambridge structural data base (reference CCDC 717536). Interatomic distances
and valence angles are given in Tables 1 and 2.
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