Synthesis and molecular structure of 4-nitro-9-phenyl-1H-and 9-hydroxy-3-oxo-9-phenyl-2,3-dihydro-9H-indeno-[2,1-c]pyridines and 3,7-diphenyl-3a, 4,5,6-tetrahydroindeno[2,1-c]isoxazolo[5,4-d]pyridine

Article abstract of DOI:10.1007/s10593-007-0181-z

The 4-nitro derivatives and an oxidation by-product, 9-hydroxy-2-methyl-3- oxo-9-phenyl-2,3-dihydro-9H-indeno[2,1-c]pyridine were obtained by the nitration of N-alkyl-9-phenyl-2,3-dihydro-1H-indeno-[2,1-c]pyridines with sodium nitrite in acetic acid. Thei

Full text of DOI:10.1007/s10593-007-0181-z

Chemistry of Heterocyclic Compounds, Vol. 43, No. 9, 2007
SYNTHESIS AND MOLECULAR STRUCTURE
OF 4-NITRO-9-PHENYL-1H- AND 9-HYDROXY-
3-OXO-9-PHENYL-2,3-DIHYDRO-9H-INDENO-
[2,1-c]PYRIDINES AND 3,7-DIPHENYL-3a,4,5,6-TETRA-
HYDROINDENO[2,1-c]ISOXAZOLO[5,4-d]PYRIDINE
S. V. Volkov1, A. N. Levov1, A. T. Soldatenkov1, N. M. Kolyadina1,
O. E. Volkova1, and V. N. Khrustalev2
The 4-nitro derivatives and an oxidation by-product, 9-hydroxy-2-methyl-3-oxo-9-phenyl-2,3-dihydro-
9H-indeno[2,1-c]pyridine were obtained by the nitration of N-alkyl-9-phenyl-2,3-dihydro-1H-indeno-
[2,1-c]pyridines with sodium nitrite in acetic acid. Their molecular structures were studied by X-ray
structural analysis. The product of [2+3] cycloaddition, 5-methyl-3,7-diphenyl-3a,4,5,6-tetrahydro-
indeno[2,1-c]isoxazolo[5,4-d]pyridine, was obtained by the interaction of 2-chloro-1-hydroxy-
2-phenylazomethine with 2-methyl-9-phenyl-2,3-dihydro-1H-indeno[2,1-c]pyridine.
Keywords: N-alkyl-4-nitro-9-phenyl-2,3-dihydro-1H-indeno[2,1-c]pyridines, 9-hydroxy-2-methyl-3-oxo-
9-phenyl-2,3-dihydro-9H-indeno[2,1-c]pyridine, 3,7-dimethyl-3a,4,5,6-tetrahydroindeno[2,1-c]isoxazolo-
[5,4-d]pyridine, X-ray structural analysis.
The principle of chemical modification of known natural and synthetic biologically active substances and
their precursors is, up to the present time, one of the bases in the strategy of designing new drugs [1], chemical
agents for protecting and treating plants and animals [2], and also food additives [3]. As a continuation of the
systematic investigation of the chemistry [4, 5] and biological activity [6, 7] of indenopyridine derivatives we
have in the present work introduced the problem of studying the direction of the conversions of N-alkyl-9-phenyl-
2,3-dihydro-1H-indeno[2,1-c]pyridines 1a,b on interacting them with sodium nitrite in acid medium, and also
with benzohydroxymoyl chloride in the presence of base. The importance of the functionalization of these close
precursors of the antiallergic agent thephorin [1] is evident, although it is impossible to consider the target
chemical modification of the latter a very simple problem, if the extremely significant chemical lability of the
precursors is taken into consideration [5]. First of all, on studying the reaction between sodium nitrite and
indenopyridines 1a,b it was established that the main products are the 4-nitro derivatives 2a,b, isolated by column
chromatography as garnet-red crystals in yields of 50 and 49% respectively.
__________________________________________________________________________________________
1People's Friendship University of Russia, Moscow 117198; e-mail: swelfen@mail.ru.
2A. N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences, Moscow 119991;
Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1390-1399, September, 2007. Original
article submitted July 21, 2006.
0009-3122/07/4309-1181©2007 Springer Science+Business Media, Inc.
1181

O2N
NaNO2/AcOH
N
N
+
CH2R
CH2R
O
Ph
Ph
2a,b
1a,b
N
Me
+
Ph
HO
3
1,2 a R = H, b R = Ph
High intensity absorption bands, characteristic of a nitro group conjugated with an olefinic bond, were
observed in the IR spectra of the synthesized compounds at 1320 and 1514 cm-1. In the mass spectra of both
compounds peaks of various intensities were present for the molecular ions M+, [M–H]+ , [M–OH]+, [M–HNO]+,
and [M–NO2]+ ions, confirming the empirical formulas of products 2a,b. The fact that the nitro group is found at
position C(4) of the tetrahydropyridine ring is indicated first by the absence of a triplet signal of the H-4 proton
(in the initial compounds it is observed at 6.87 and 6.80 ppm), and secondly by the significant displacement
towards low field (∆δ = 0.6 ppm) of the doublet-doublet signal of the H-5 benzene proton. This may be linked
primarily with the occurrence of the electron-withdrawing NO2 group in a pseudo-peri position to this proton and
its deshielding effect. For unequivocal confirmation of the fact that under electrophilic nitrosation conditions
oxidation of the nitroso group to nitro occurs, an X-ray structural investigation of nitro compound 2a was carried
out (Fig. 1, Tables 1 and 2).
Fig. 1. Molecular structure of compound 2a (atoms are shown
as 40%-probability ellipsoids of anisotropic displacements).
1182

TABLE 1. Bond Lengths (l) in Structure 2a
Bond
O(1)–N(1)
l, Å
Bond
C(5)–C(6)
l, Å
1.193(3)
1.205(3)
1.460(3)
1.444(3)
1.483(3)
1.442(3)
1.456(3)
1.492(3)
1.356(3)
1.466(3)
1.484(3)
1.381(3)
1.416(3)
1.388(4)
1.362(4)
1.397(3)
1.373(3)
1.481(3)
1.353(3)
1.470(3)
1.387(3)
1.398(3)
1.371(3)
1.373(3)
1.367(3)
1.369(3)
O(2)–N(1)
C(6)–C(7)
N(1)–C(4)
C(7)–C(8)
C(1)–N(2)
C(8)–C(8A)
C(8A)–C(9)
C(9)–C(9A)
C(9)–C(11)
C(11)–C(12)
C(11)–C(16)
C(12)–C(13)
C(13)–C(14)
C(14)–C(15)
C(15)–C(16)
C(1)–C(9A)
N(2)–C(3)
N(2)–C(10)
C(3)–C(4)
C(4)–C(4A)
C(4A)–C(9A)
C(4A)–C(4B)
C(4B)–C(5)
C(4B)–C(8A)
TABLE 2. Valence Angles (ω) in Structure 2a
Angle
ω, deg
Angle
ω, deg
O(1)–N(1)–O(2)
O(1)–N(1)–C(4)
O(2)–N(1)–C(4)
N(2)–C(1)–C(9A)
C(3)–N(2)–C(1)
121.9(3)
120.8(2)
117.3(3)
109.70(19)
111.79(18)
110.9(2)
111.9(2)
112.31(18)
124.0(2)
122.3(2)
113.7(2)
116.04(19)
137.4(2)
106.52(17)
118.8(2)
135.0(2)
106.18(18)
119.1(2)
121.8(2)
C(6)–C(7)–C(8)
120.2(2)
C(8A)–C(8)–C(7)
C(8)–C(8A)–C(4B)
C(8)–C(8A)–C(9)
C(4B)–C(8A)–C(9)
C(9A)–C(9)–C(11)
C(9A)–C(9)–C(8A)
C(11)–C(9)–C(8A)
C(9)–C(9A)–C(4A)
C(9)–C(9A)–C(1)
C(4A)–C(9A)–C(1)
C(12)–C(11)–C(16)
C(12)–C(11)–C(9)
C(16)–C(11)–C(9)
C(13)–C(12)–C(11)
C(12)–C(13)–C(14)
C(15)–C(14)–C(13)
C(14)–C(15)–C(16)
C(15)–C(16)–C(11)
118.6(2)
121.36(19)
129.6(2)
108.98(17)
126.70(19)
108.16(19)
125.14(17)
110.12(18)
128.5(2)
C(3)–N(2)–C(10)
C(1)–N(2)–C(10)
N(2)–C(3)–C(4)
C(4A)–C(4)–N(1)
C(4A)–C(4)–C(3)
N(1)–C(4)–C(3)
121.40(19)
117.9(2)
C(4)–C(4A)–C(9A)
C(4)–C(4A)–C(4B)
C(9A)–C(4A)–C(4B)
C(5)–C(4B)–C(8A)
C(5)–C(4B)–C(4A)
C(8A)–C(4B)–C(4A)
C(4B)–C(5)–C(6)
C(7)–C(6)–C(5)
120.85(19)
121.27(18)
121.1(2)
119.8(2)
120.2(2)
120.4(2)
120.5(2)
The indenopyridine portion of molecule 2a (with the exception of atom N(2)) was practically planar
(mean square deviation of atoms from the mean plane was 0.018 Å). Atom N(2) emerges from this plane by 0.618
Å, and consequently the tetrahydropyridine ring has a sofa conformation.The nitro group is disposed in a
practically coplanar manner with the indenopyridine (angle between the corresponding planes is 60°), while the
phenyl substituent is opened at an angle of 50.3° in relation to the same plane.
Atom N(2) has a pyramidal configuration (sum of valence angles at atom N(2) is equal to 334.6°).
The bond lengths and valence angles in the 2a molecule have average values [8].
In the synthesis of nitro compound 2a the product of partial oxidation of the initial 1a, viz. 9-hydroxy-
3-oxo-2,3-dihydroindenopyridine 3, was also isolated from the reaction mixture in 17% yield. This compound is
formed as a result of isomerization of the s-trans diene fragment into the s-cis diene system fixed by oxidation of
the 3-CH2 group into a keto group with the formation of the thermodynamically stable α-pyridone system.
1183

The similar processes may be accompanied by a C(1)→C(9) prototropic shift, but the high C(9)-H acidity
of the triarylmethine proton [9] leads to facile oxidation of this fragment to the corresponding carbinol. It is
necessary to mention that compound 3 has melting point, IR, 1H NMR, and mass spectra identical to those of the
substance obtained previously by us by the oxidation of the initial 1a with manganese dioxide at room
temperature [5]. With the aim of finally establishing its structure and stereochemical features, an X-ray structural
analysis was carried out on compound 3 (Fig. 2, Tables 3 and 4).
Fig. 2. Molecular structure of compound 3 (atoms are shown as 40%
probability ellipsoids of anisotropic displacements).
TABLE 3. Bond Lengths (l) in Structure 3
Bond
l
, Å
Bond
C(6)–C(7)
l, Å
O(1)–C(3)
1.2575(14)
1.4319(14)
1.3547(17)
1.3756(15)
1.3894(16)
1.4678(16)
1.4360(17)
1.3643(16)
1.4240(16)
1.4655(16)
1.3932(17)
1.4024(16)
1.3907(18)
1.3939(19)
1.3951(19)
1.3854(17)
1.5387(17)
1.5247(16)
1.5281(16)
1.3902(18)
1.3945(18)
1.3923(19)
1.386(2)
O(2)–C(9)
C(7)–C(8)
C(1)–C(9A)
C(1)–N(2)
C(8)–C(8A)
C(8A)–C(9)
C(9)–C(11)
C(9)–C(9A)
C(11)–C(16)
C(11)–C(12)
C(12)–C(13)
C(13)–C(14)
C(14)–C(15)
C(15)–C(16)
N(2)–C(3)
N(2)–C(10)
C(3)–C(4)
C(4)–C(4A)
C(4A)–C(9A)
C(4A)–C(4B)
C(4B)–C(5)
C(4B)–C(8A)
C(5)–C(6)
1.381(2)
1.3886(19)
1184

TABLE 4. Main Valence Angles (ω) in Structure 3
Angle
ω, deg
Angle
ω, deg
C(9A)–C(1)–N(2)
C(1)–N(2)–C(3)
C(1)–N(2)–C(10)
C(3)–N(2)–C(10)
O(1)–C(3)–N(2)
O(1)–C(3)–C(4)
N(2)–C(3)–C(4)
C(4A)–C(4)–C(3)
C(6)–C(7)–C(8)
C(8A)–C(8)–C(7)
C(8)–C(8A)–C(9)
20.41(11)
O(2)–C(9)–C(11)
O(2)–C(9)–C(9A)
C(11)–C(9)–C(9A)
O(2)–C(9)–C(8A)
C(11)–C(9)–C(8A)
C(6)–C(5)–C(4B)
C(5)–C(6)–C(7)
107.05(9)
112.92(9)
113.90(10)
111.77(10)
110.86(9)
118.15(12)
120.95(12)
129.65(11)
119.65(11)
121.47(11)
122.83(10)
119.88(10)
117.28(10)
119.28(11)
124.06(11)
116.66(10)
120.13(11)
120.76(12)
118.64(12)
127.92(11)
C(1)–C(9A)–C(9)
C(16)–C(11)–C(9)
C(12)–C(11)–C(9)
The indenopyridine fragment of the molecule 3 is practically planar (mean square deviation of atoms
from the average plane was 0.024 Å). The plane of the phenyl substituent is disposed at angle of 74.7° to the
plane of the indenopyridine fragment but the plane of the three-atom grouping (C(9)–O(2)–H(2O)) is at an angle
of 84.5°.
The N(2) atom has a planar trigonal configuration (sum of valence angles at the N(2) atom is 360.0°).
The bond lengths and valence angles in the molecule 3 have average values [8].
In the crystal the molecules 3 form centrosymmetric dimers as a result of intermolecular hydrogen bonds
O(2)-H(2O)···O(1) [-x, -y+1, -z+1] [O···O 2.759(2), H···O 1.81(2) Å, angle O-H···O 177(1)°] (Fig. 3).
Fig. 3. Centrosymmetric dimers of compound 3 in the crystal,
dotted lines show hydrogen bonds.
Reaction of indenopyridine 1a was also carried out with chlorobenzaldehyde oxime 4. In the presence of
triethylamine the latter is converted into zwitter-ion 4a, which reacts with compound 1a by a [2+3] cycloaddition
reaction with the possible formation of two isomers. As a result of chromatographic separation only one substance
was isolated (in 29% yield) having, according to spectral data, the structure of tetrahydro-
indeno[2,1-c]isoxazolo[5,4-d]pyridine 5.
1185

2
N
3
Ph
1 O
Cl
3a
–
+
1a
4
O
O
OH
Et3N
+
Ph
Ph
N
Ph
N
N
Me
4
6
7
–
Ph
N
+
5
4a
1
In its H NMR spectrum the two H-4 protons experience the significant shielding effect of the
benzaldimine fragment and resonate as two doublet-doublet signals at 2.51 and 2.82 ppm (in the spectrum of the
initial compound 1a the analogous two H-3 protons give one singlet signal at 3.41 ppm). The geminal coupling
constants of these protons are 2J = 11.0, but 3J = 7.0 and 4.0 Hz respectively. This indicates the axial disposition
of the H-3a methine proton, which resonates as a triplet signal at 3.97 ppm. Consideration of a three-dimensional
Dreiding model of molecule 5 also shows that, due to the sp2 configuration of the C(6a) atom and also
participation of atoms C(3a), C(6a), and C(11b) in a rigid spiro-linked system of two five-membered rings, the
piperidine ring must have a sofa configuration with axial disposition of the H-3a proton. A NOESY analysis was
carried out for additional confirmation of the structure of compound 5. The spatial structure of the isomeric
1
adduct of cycloaddition 5 was established with the aid of the two-dimensional Overhauser effect on H nuclei.
Thus, in the 2D NOESY spectrum a cross-peak was observed between the H-3a protons (3.97 ppm) and the ortho
protons of the phenyl substituent at C(3) (7.78 ppm), which was absent from the COSY spectrum. This fact
indicates that the nuclei indicated are spatially close, which is only possible in the case of structure 5.
TABLE 5. Main Crystallographic Data and Refinement Parameters
for Compounds 2a and 3
Compound
Empirical formula
2а
3
C19H16N2O2
304.34
C19H15NO2
289.32
М
T, K
293
120
System
Space group
Monoclinic
P21/c
Monoclinic
P21/c
a, Å
b, Å
c, Å
10.757(2)
15.027(3)
10.025(2)
107.65(2)
1544.2(5)
13.3169(9)
9.5943(6)
11.0655(7)
93.932(5)
β, deg
V, Å3
1410.47(16)
Z
4
4
dc, g/cm-3
F(000)
1.309
640
0.086
54
1.362
608
0.089
54
µ, mm-1
2θmax, deg.
Number of
reflections measured
3527
3335
1959
208
12 949
3054
2612
259
independent reflections
observed reflections with I > 2σ(I)
refined parameters
R1 (I > 2σ(I))
wR2 (all data)
GOOF
0.056
0.140
1.004
0.042
0.116
1.024
1186

In conclusion we note that nitro compound 2a, according to the prediction of the internet program PASS
[10], is promising for biotesting as an agent for the treatment of psychosexual disorders, Alzheimer's disease, and
hypertonia.
EXPERIMENTAL
1
The H NMR spectra were recorded on a Bruker WM-400 (400 MHz) spectrometer in CDCl3, internal
standard was TMS. The mass spectra (EI) were obtained on a MAT-112 instrument with direct insertion of
sample into the ion source at an ionizing voltage of 70 eV. The IR spectra were recorded on an IR-75
spectrometer in KBr disks. Silufol UV-254 plates were used for TLC (visualization with iodine vapor). Column
chromatography was carried out on silica gel (Silicagel L 32/63). Compounds 1a and 1b were obtained as
described in [11].
X-ray Structural Investigation of Compounds 2a and 3. Crystals of compounds 2a and 3 were grown
in benzene. Parameters of the unit cells and the intensity of reflections were measured on a Syntex P21 automatic
diffractometer (T = 293 K, λMoKα radiation, graphite monochromator, θ/2θ scanning) (compound 2a) and a
Bruker SMART 1000 CCD automatic diffractometer (T = 120 K, λMoKα radiation, graphite monochromator, ϕ
and ω scanning) (compound 3). The main crystallographic data and the refinement parameters are given in
Table 5. The structures of both compounds were determined by the direct method and were refined by the full
matrix least squares method in an anisotropic approach for the non-hydrogen atoms. The positions of the
hydrogen atoms in the case of compound 2a were calculated geometrically and were refined in an isotropic
approach with fixed positions ("rider" model) and thermal parameters (Uiso(H) = 1.5Ueq(C) for CH3 groups and
U(H)iso = 1.2Ueq(C) for all other groups). The hydrogen atoms in the case of compound 3 were localized
objectively in Fourier difference syntheses and were refined isotropically. All calculations were carried out using
the SHELXTL PLUS set of programs [12]. Tables of atomic coordinates, bond lengths, valence angles, and
anisotropic thermal parameters for compounds 2a and 3 have been deposited in the Cambridge Structural Data
Bank (CCDC 658025 and 658026 respectively).
2-Methyl-4-nitro-9-phenyl-2,3-dihydro-1H-indeno[2,1-c]pyridine (2a). Sodium nitrite (0.53 g,
7.7 mmol) was added in portions during 1 h to a solution of indenopyridine 1a (2 g, 7.7 mmol) in AcOH (15 ml).
The mixture was stirred for a further 0.5 h at 20°C, then neutralized with saturated sodium carbonate solution
(pH 7), and extracted with ether. The extract was dried over MgSO4, the solvent evaporated, and the residue
resolved on a chromatographic column (eluent hexane, then ethyl acetate–hexane, 1:5). Compound 2a (1.17 g,
50%) was obtained first as garnet-red crystals, mp 102-103°C. IR spectrum, ν, cm-1: 1320, 1514 (NO2). 1H NMR
spectrum, δ, ppm (J, Hz): 2.48 (3H, s, CH3); 3.53 (2H, s, H-1); 3.78 (2H, s, H-3); 7.20-7.50 (8H, m, Harom); 8.18 (1H,
dd, 3J = 7.6, 4J = 1.0, H-5). Mass spectrum, m/z (Irel, %): 304 [M]+ (4), 303 (7), 302 (10), 287 [M–OH]+ (7), 286 (11),
278 (12), 274 (27), 273 [M–H–NO]+ (100), 257 (30), 242 (11), 230 (19), 215 (15), 202 (17), 201 (22), 189 (7), 77
(4). Found, %: C 75.21; H 5.44; N 9.15. C19H16N2O2. Calculated, %: C 75.00; H 5.26; N 9.21. M 304.
9-Hydroxy-2-methyl-3-oxo-9-phenyl-2,3-dihydro-9H-indeno[2,1-c]pyridine (3) was then eluted from
the chromatographic column as beige crystals. Yield was 0.38 g (17%). In mp (143-145°C), 1H NMR, mass, and
IR spectra substance 3 was identical with the substance isolated and described previously in [5].
2-Benzyl-4-nitro-9-phenyl-2,3-dihydro-1H-indeno[2,1-c]pyridine (2b) was obtained analogously to
1
compound 2a. Yield was 49%. Dark claret-crystals, mp 80-82oC. IR spectrum, ν, cm-1: 1328, 1521 (NO2). H
NMR spectrum, δ, ppm (J, Hz): 3.39 (2H, s, H-1); 3.73 (2H, s, H-3); 3.83 (2H, s, NCH2C6H5); 7.23-7.49 (8H, m,
H
arom); 8.16 (1H, dd, 3J = 7.5 and 4J = 1.0, H-5). Mass spectrum, m/z (Irel, %); 380 [M]+ (8), 379 (8), 363 [M–OH]+
(20), 349 [M–H–NO]+ (5), 334 [M–NO2]+ (7), 333 (21), 242 (11), 215 (15), 91 (100), 65 (23). Found, %:
C 78.73; H 5.47; N 7.34. C25H20N2O2. Calculated, %: C 78.95; H 5.26; N 7.37. M 380.
1187

5-Methyl-3,7-diphenyl-3a,4,5,6-tetrahydroindeno[2,1-c]isoxazolo[5,4-d]pyridine (5). Triethylamine
(0.19 g, 0.27 ml, 1.93 mmol) was added gradually (during 10 min) to a solution of benzohydroxymoyl chloride 4
(0.3 g, 1.93 mmol) in absolute ether (20 ml) cooled to 0-5°C. The mixture was stirred for 0.5 h, the solid filtered
off, and a solution of indenopyridine 1a (0.5 g, 1.93 mmol) in absolute ether (30 ml) was added carefully to the
filtrate (benzonitrile N-oxide) cooled to 0°C. The mixture was then boiled for 6 h. The solvent was evaporated in
vacuum, the residue was resolved on a chromatographic column, eluent was ethyl acetate–hexane, 1:1. Compound
1
5 (0.21 g, 29%) was obtained as light-yellow crystals, mp 145-147°C. H NMR spectrum, δ, ppm (J, Hz): 2.27
(3H, s, CH3); 2.50 (1H, dd, 2J = 12.1 and 3J = 7.1, He-4); 2.82 (1H, dd, 2J = 12.1 and 3J = 5.8, Ha-4); 3.42 (1H, d,
2J = 13.8, H-6); 3.61 (1H, d, 2J = 13.8, H-6); 3.96 (1H, t, 3J = 7.0 and 3J = 5.9, H-3a); 7.09-7.79 (14H, m, Harom).
Mass spectrum, m/z (Irel, %): 378 [M]+ (28), 335 [M–CH2NCH3]+ = Φ1 (23), 334 (16), 258 [Φ1-Ph]+ (37), 231
(67), 204 (100), 203 (87), 202 (46), 145 (42), 105 (29), 77 (51), 42 (87). Found, %: C 82.38; H 5.75; N 7.62.
C26H22N2O. Calculated, %: C 82.54; H 5.82; N 7.41. M 378.
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2.
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A. T. Soldatenkov, N. M. Kolyadina, Li Tuan An, and V. N. Buyanov, Principles of the Organic
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