Reactions of p-quinone diimines of the 1,2,3,4,4a,5-hexahydro-10H- benzimidazo[2,1-j]quinolin-10-imines with some compounds having an activated methylene group

Article abstract of DOI:10.1134/S1070428009030130

Reactions of N-(1,2,3,4,4a,5-hexahydro-10H-benzimidazo[2,1-j]quinolin-10- ylidene)amines with malononitrile and cyanoacetamide gave the corresponding 12-methylidene derivatives.

Full text of DOI:10.1134/S1070428009030130

ISSN 1070-4280, Russian Journal of Organic Chemistry, 2009, Vol. 45, No. 3, pp. 425–429. © Pleiades Publishing, Ltd., 2009.
Original Russian Text © O.Yu. Slabko, O.N. Shandova, V.A. Kaminskii, 2009, published in Zhurnal Organicheskoi Khimii, 2009, Vol. 45, No. 3,
pp. 435–439.
Reactions of p-Quinone Diimines of the 1,2,3,4,4a,5-Hexahydro-
10H-benzimidazo[2,1-j]quinolin-10-imines with Some
Compounds Having an Activated Methylene Group
O. Yu. Slabko, O. N. Shandova, and V. A. Kaminskii
Far East State University, ul. Oktyabr’skaya 27, Vladivostok, 690600 Russia
e-mail: slabko@chem.dvgu.ru
Received April 19, 2008
Abstract—Reactions of N-(1,2,3,4,4a,5-hexahydro-10H-benzimidazo[2,1-j]quinolin-10-ylidene)amines
with malononitrile and cyanoacetamide gave the corresponding 12-methylidene derivatives.
DOI: 10.1134/S1070428009030130
Reactions of p-quinone diimines with carbon-
centered nucleophiles have been studied insufficiently.
A few reactions of symmetric N,N′-diacyl-p-quinone
diimines with 1,3-dicarbonyl compounds (dibenzoyl-
methane, cyclohexane-1,3-dione, etc.) were reported to
occur as addition at the quinoid ring with formation of
benzoid structures [1–3]. Even less data are available
on analogous reactions with heterocyclic quinone
derivatives. We found only one example of reaction of
heterocyclic quinone imine (benzophenoxazinone)
with anionic C-nucleophiles, which followed aromatic
nucleophilic substitution pattern, and the subsequent
tautomerization gave products having methylenequi-
none imine structure [4]; no analogous reactions with
quinone diimines were reported. Baxter et al. [5] de-
scribed the addition of acetylacetone at the quinoid
fragment of 4-arylsulfonylimino-6H-1,3-benzoxazol-2-
one with formation of benzoid structure.
directions of nucleophilic addition to quinone diimines
is related to the presence of an electron-withdrawing
phenyl ring or electron-donating cyclohexane ring on
the exocyclic nitrogen atom. Taking into account that
the addition at position 9 (and subsequent tautomeriza-
tion) was observed only once, it seemed to be reason-
able to examine reactions of CH acids with a larger
number of N-substituted quinone diimines with a view
to elucidate whether the above direction is general.
Initial quinone diimines IIa, IIIa, IVa, and IVb
were prepared by oxidative coupling of 1,2,3,4,4a,5-
hexahydro-13H-benzimidazo[2,1-j]quinolines Ia and
Ib with primary aliphatic amines in the presence of
manganese(IV) oxide. Compounds IIIa [7] and IVa
and IVb [8], which were obtained by coupling with
2,2,6,6-tetramethylpiperidin-4-amine and 2-amino-2-
methylpropan-1-ol, respectively, were described previ-
ously. Condensation product IIa derived from methan-
amine was synthesized for the first time.
We previously showed [6] that pyrido[1,2-a]benz-
imidazole derivatives having a quinone imine or
N-phenylquinone diimine fragment react with indan-
1,3-dione, barbituric acid, malononitrile, and cyano-
acetamide to give the corresponding substitution prod-
ucts at the 8-position of the pyridobenzimidazole
system. By contrast, the reactions with N-cyclohexyl-
quinone diimines of the same series occurred at the
9-position with subsequent tuatomerization to o-meth-
ylenequinone imine derivatives. Presumably, initial
1,4-addition at the quinoid ring is followed by oxida-
tion (e.g., with atmospheric oxygen) which regenerates
quinoid structure. It was presumed that the different
We found that compounds IIa, IIIa, IVa, and IVb
readily react with malononitrile and cyanoacetamide to
give compounds V–IX having a methylene-p-quinone
imine fragment (Scheme 1). The reactions occurred at
high rate at room temperature, i.e., under milder condi-
tions than in the reactions with quinone imines and
N-phenylquinone diimine (the latter were slow even at
elevated temperature) [6].
Taking into account that the isolation of compound
IIa was difficult due to its thermal and chromato-
graphic instability, we tried to synthesize compounds
Va and VIIIa directly from 1,2,3,4,4a,5-hexahydro-
425

SLABKO et al.
426
Scheme 1.
R4
R4
N
HN
NC
R3
R3
R3
10
9
7
R2
R1
R2
R1
11
R2
R1
8
N
6
R4NH2, MnO2
R5CH2CN
N
N
12
5
R5
NH
N13
N
1
4
2
3
Ia, Ib
IIa, IIIa, IVa, IVb
Va, VIa, VIIa, VIIb, VIIIa, IXa
R1 = H, R2R3 = (CH2)4 (a); R1 = R3 = Ph, R2 = H (b); II, V, VIII, R4 = Me; III, VI, IX, R4 = 2,2,6,6-tetramethylpiperidin-4-yl;
IV, VII, R4 = HOCH2CMe2; V–VII, R5 = CN; VIII, IX, R5 = CONH2.
13H-benzimidazo[2,1-j]quinolines Ia and Ib and the
corresponding CH acids without intermediate isolation
of imines IIa and IIIa. For this purpose, the reaction
mixture containing imine IIa or IIIa was filtered from
MnO2, and malononinitrile or cyanoacetamide was
added to the filtrate. This one-pot procedure was also
used to obtain compounds VIa and IXa from
N-(2,2,6,6-tetramethylpiperidin-4-yl)imine IIIa.
The m/z values of pseudomolecular [M + H]+ ions
in the mass spectra of V–IX were consistent with those
calculated for the assumed structures.
The 1H NMR spectra of V–IX lacked signal assign-
able to 12-H, a signal typical of NH group appeared,
and the 11-H signal changed its multiplicity from dou-
blet of doublets (as in the spectra of initial compounds
II–IV) to a doublet with a long-range coupling con-
4
stant J of 1.7 Hz. These findings also confirmed the
All compounds V–VII obtained by condensation
with malononitrile were stable, in contrast to those
derived from cyanoacetamide (compounds VIIIa and
IXa); the yields of the latter were lower due to their
thermal and photochemical lability. Solutions of all
compounds V–IX were bright green.
presence of a methylenequinone imine fragment in
molecules V–IX.
In the 1H NMR spectra of Va, VIa, VIIa, and VIIb,
signals from the quinoid 9-H and 11-H protons, as well
as from protons in the NH and CH3 groups, were
doubled at a ratio of 1.5:1 (Va, VIa), 1:1 (VIIa), or
6:1 (VIIb). Nuclear Overhauser effect experiments
showed the existence of stable conformers A and B
with respect to the single C10–N bond. Signals from
protons in the quinoid fragments and NH groups in the
spectra of Va, VIa, VIIa, and VIIb were assigned
using heteronuclear double resonance technique
(INDOR). Increased fraction of one conformer of com-
pound VIIb (6:1) is likely to be related to restricted
inversion of the aminoethanol fragment located in the
vicinity of the 7-phenyl group.
We previously showed [8] that N-(2-hydroxyethyl)-
quinone diimines formed as a result of oxidative
coupling of pyridobenzimidazole derivatives with sub-
stituted aminoethanols are capable of undergoing intra-
molecular cyclization to give products having an oxa-
zine ring fused at the 7,8-position. However, we failed
to obtain analogous cyclization products from com-
pounds VIIa and VIIb on heating or on treatment with
potassium tert-butoxide. Presumably, the presence of
an electron-donating amino group at C10 deactivates
the neighboring C11 atom toward nucleophilic attack;
on the other hand, some contribution of steric hin-
drances is also possible.
Analogous signal doubling in the spectra of VIIIa
and IXa could result from the presence of Z and E
stereoisomers with respect to the exocyclic C12=C
double bond, as was the case of p-methylenequinone
imine derivatives reported previously [9]. We believe
that these compounds also exist as mixtures of stable
conformers A and B having more favorable E con-
figuration of the exocyclic double bond. The latter
follows from the downfield position of the 11-H signal
(δ 7.40–7.50 ppm against δ 6.90 ppm in the spectrum
of IIa) due to deshielding by the CONH2 fragment.
The IR spectra of V–IX contained an absorption
band typical of secondary amino group, while absorp-
tion bands belonging to vibrations of the double C6=C7
bond and quinoid C=N and C=C bonds were retained,
indicating formation of ortho-quinoid structure. Com-
pounds V–VII displayed absorption bands due to con-
jugated cyano groups, and bands typical of conjugated
cyano and carbamoyl groups were observed in the IR
spectra of VIIIa, IXa. The presence of OH absorption
in the spectra of VIIa and VIIb confirmed that no
fusion at positions 7,8 occurred.
Our results demonstrate that the regioselectivity of
nucleophilic addition to p-quinone diimines of the
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REACTIONS OF p-QUINONE DIIMINES OF THE 1,2,3,4,4a,5-HEXAHYDRO-10H-...
427
pyridobenzimidazole series is determined by the elec-
tronic nature of substituent on the exocyclic nitrogen
atom.
purified by chromatography using petroleum ether–
ethyl acetate (3:1) as eluent. Yield 62%, red crystals,
mp 120–122°C. IR spectrum, ν, cm–1: 1666 (C6=C7);
1629 (C=N); 1595, 1535 (C=Cquin). 1H NMR spectrum,
δ, ppm: 1.20–2.20 m (19H), 3.16 s (3H, CH3), 5.82 s
(1H, 9-H), 6.90 d (1H, 11-H, J = 10.0 Hz), 7.15 d (1H,
12-H, J = 10.0 Hz). Found, %: C 78.07; H 8.42;
N 13.21. Mass spectrum: m/z 308 [M + H]+. C20H25N3.
Calculated, %: C 78.14; H 8.20; N 13.67. M 307.43.
EXPERIMENTAL
The IR spectra were recorded on a Perkin–Elmer
Spectrum BX-II spectrometer from solutions in meth-
ylene chloride or samples prepared as KBr pellets. The
1H NMR spectra were measured from solutions in
DMSO-d6 on a Bruker AC-250 spectrometer at
250 MHz using tetramethylsilane as internal reference.
The elemental compositions were determined on
a Flash EA 1112 CHN/MAS200 analyzer. HPLC anal-
ysis was performed on an HP 1100 LC/MSD instru-
ment equipped with a Hypersil ODS column (4×
125 mm); eluent propan-2-ol–water (60:40), flow rate
0.3 ml/min, temperature 55°C, diode matrix; atmos-
pheric pressure corona discharge ionization source;
positive or negative (VIIa) ion mode. The mass spec-
tra were also recorded under electron impact (70 eV)
with direct sample admission into the ion source.
General procedure for the synthesis of com-
pounds V–IX. a. Compound IIa, IIIa, IVa, or IVb,
1 mmol, was dissolved in 10 ml of ethanol, 1.5 mmol
of malononitrile or cyanoacetamide was added, and the
mixture was stirred at room temperature until the
initial compound disappeared according to the TLC
data (for 1 h in the sunthesis of VIa, for 2 h in the
synthesis of VIIa and VIIb, for 3 h in the synthesis of
VIIIa and IXa, and for 5 h in the synthesis of Va). By
the end of the process, the mixture turned dark green.
In the synthesis of VIIa, the mixture was cooled, and
the precipitate was filtered off and recrystallized from
hexane–acetone. In the other cases, the mixture was
diluted with three volumes of water, 3 ml of a saturated
solution of Na2CO3 was added, and the precipitate was
filtered off, washed with water (2×5 ml), dried, and
subjected to chromatography using petroleum ether–
ethyl acetate (2:1) (Va, VIIb), acetone–ethanol (1:2)
(VIIIa, IXa), or pure ethanol (VIa) as eluent. The
products were green finely crystalline substances
which were readily soluble in ethanol, acetone, and
ethyl acetate and very poorly soluble in hexane and
chloroform.
The melting points were determined in capillaries
or using a Boetius melting point apparatus. The prog-
ress of reactions and the purity of products were
monitored by TLC using Silufol UV-254 and Sorbfil
plates; hexane–ethyl acetate (1:1), ethyl acetate, etha-
nol, and AcOH–water (1:10) were used as eluents.
Preparative thin-layer chromatography was performed
on 25×30-cm plates coated with a 1.5-mm layer of
aluminum oxide of activity grade II according to
Brockmann; sample amount 0.25 g.
All compounds were synthesized according to
the general procedure (see below) with different isola-
tion and purification methods. Compounds Ia and Ib
[10], IIIa [7], and IVa [8] were reported previously.
b. One-pot procedure for the synthesis of com-
pounds Va, VIa, VIIIa, and IXa. Compound Ia,
1 mmol, was dissolved in 10 ml of ethanol, 1.5 mmol
of the corresponding amine and 3 g of MnO2 were
added in succession, and the mixture was stirred at
room temperature until the initial compound disap-
peared according to the TLC data. The precipitate of
MnO2 was filtered off and washed on a filter with
ethanol until slightly colored washings. Malononitrile,
or cyanoacetamide, 1.5 mmol, was added to the fil-
trate, and the mixture was stirred at room temperature
until compound IIa or IIIa disappeared according to
the TLC data. The mixture was then diluted with three
volumes of water, 3 ml of a saturated solution of
Na2CO3 was added, and the precipitate was filtered off,
washed with water (2×5 ml), and dried. The product
was purified by preparative thin-layer chromatography
as described above in a.
N-(6,7-Tetramethylene-1,2,3,4,4a,5-hexahydro-
10H-benzimidazo[2,1-j]quinolin-10-ylidene)meth-
anamine (IIa). Compound Ia, 1 mmol, was dissolved
in 20 ml of ethanol, a solution of 1.5 mmol of methan-
amine hydrochloride in 10 ml of ethanol saturated with
Na2CO3 was added under stirring, and 3 g of MnO2
was then added. The mixture was stirred for 3 h at
room temperature until the initial compound disap-
peared (TLC), the precipitate of MnO2 was filtered off
and washed with ethanol until slightly colored wash-
ings, the filtrate was diluted with three volumes of
water, 3 ml of a saturated solution of Na2CO3 was
added, and the precipitate was filtered off, washed with
two portions of water, and dried. The product was
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SLABKO et al.
428
1H NMR spectrum, δ, ppm: 1.10–2.20 m (11H), 1.14 s
(10-Methylamino-6, 7-tetramethylene-
(3H, CH3, A), 1.22 s (3H, CH3, A), 1.28 s (3H, CH3,
B), 1.30 s (3H, CH3, B), 4.00 d.d (1H, 5-H, B, J5,4a
1,2,3,4,4a,5-hexahydro-12H-benzimidazo[2,1-j]-
quinolin-12-ylidene)malononitrile (Va) (A:B ratio
3:2). Yield 51 (a), 67 (b); mp 266–268°C (decomp.).
IR spectrum, ν, cm–1: 3263 (NH); 2186, 2155 (CN);
1666 (C6=C7); 1633 (C=N); 1590, 1549 (C=Cquin).
1H NMR spectrum, δ, ppm: 0.80–2.40 m (19H), 1.20 s
(3H, CH3, B), 1.28 s (3H, CH3, A), 5.60 d (1H, 9-H, A,
J = 1.7 Hz), 5.66 d (1H, 9-H, B, J = 1.5 Hz), 5.80 d
(1H, 11-H, B, J = 1.5 Hz), 5.97 d (1H, 11-H, A, J =
1.7 Hz), 8.73 m (1H, NH, B), 8.97 m (1H, NH, A).
Found, %: C 74.45; H 6.99; N 18.39. Mass spectrum:
m/z 372 [M + H]+. C23H25N5. Calculated, %: C 74.36;
H 6.78; N18.85. M 371.48
=
10.0, J5,6 = 3.0 Hz), 4.07 d.d (1H, 5-H, A, J5,4a = 10.0,
J5,6 = 3.0 Hz), 4.52 d (1H, 9-H, A, J = 1.7 Hz), 4.75 d
(1H, 9-H, B, J = 1.7 Hz), 4.99 t (1H, OH, A, J =
5.6 Hz), 5.15 t (1H, OH, B, J = 5.6 Hz), 5.50 d (1H,
6-H, B, J = 3.0 Hz), 5.55 d (1H, 6-H, A, J = 3.0 Hz),
6.08 d (1H, 11-H, B, J = 1.7 Hz), 6.10 d (1H, 11-H, A,
J = 1.7 Hz), 7.20–7.50 m (10H, Harom), 8.18 br.s (1H,
NH, B), 8.48 br.s (1H, NH, A). Found, %: C 77.72;
H 6.11; N 13.20. Mass spectrum: m/z 528 [M + H]+.
C34H33N5O. Calculated, %: C 77.39; H 6.30; N 13.27.
M 527.66
2-Cyano-2-[(12E)-10-methylamino-6,7-tetra-
methylene-1,2,3,4,4a,5-hexahydro-12H-benzimid-
azo[2,1-j]quinolin-12-ylidene]acetamide (VIIIa)
(A:B ratio 1:1). Yield 48 (a), 64 (b); mp 167–169°C
(decomp.). IR spectrum, ν, cm–1: 3483, 3410 (NH2);
3247 (NH); 2162 (CN); 1700 (C=O); 1669 (C6=C7);
[6,7-Tetramethylene-10-(2,2,6,6-tetramethyl-
piperidin-4-ylamino)-1,2,3,4,4a,5-hexahydro-12H-
benzimidazo[2,1-j]quinolin-12-ylidene]malono-
nitrile (VIa) (A:B ratio 3:2). Yield 65 (a), 53 (b);
mp 252–254°C (decomp.). IR spectrum, ν, cm–1: 3317,
3244 (NH); 2193, 2170 (CN); 1668 (C6=C7); 1633
1
1
1644 (C=N); 1585 (C=Cquin). H NMR spectrum, δ,
(C=N); 1593, 1537 (C=Cquin). H NMR spectrum, δ,
ppm: 0.90–2.50 m (19H), 1.14 s (3H, CH3, A), 1.22 s
(3H, CH3, B), 5.50 s (1H, 9-H, A), 5.52 s (1H, 9-H, B),
6.03 br.s (2H, NH2, A), 6.36 br.s (2H, NH2, B),
7.40 br.s (1H, 11-H, A), 7.50 br.s (1H, 11-H, B),
8.09 br.s (1H, NH, A), 8.60 br.s (1H, NH, B). Found,
%: C 70.97; H 7.43; N 18.19. Mass spectrum: m/z 390
[M + H]+. C23H27N5O. Calculated, %: C 70.92; H 6.99;
N 17.98. M 389.49.
ppm: 1.00–2.50 m (24H), 1.02 s (12H, CH3, A), 1.20 s
(12H, CH3, B), 5.61 d (1H, 9-H, A, J = 1.5 Hz), 5.69 d
(1H, 9-H, B, J = 1.2 Hz), 5.85 d (1H, 11-H, B, J =
1.2 Hz), 5.99 d (1H, 11-H, A, J = 1.5 Hz), 8.62 br.s
(1H, NH, B), 8.85 br.s (1H, NH, A). Found, %:
C 75.38; H 8.15; N 16.66. Mass spectrum: m/z 497
[M + H]+. C31H40N6. Calculated, %: C 74.96; H 8.12;
N16.92. M 496.69.
2-Cyano-2-[(12E)-6,7-tetramethylene-10-
(2,2,6,6-tetramethylpiperidin-4-ylamino)-
1,2,3,4,4a,5-hexahydro-12H-benzimidazo[2,1-j]-
quinolin-12-ylidene]acetamid (IXa) (A:B ratio 3:2).
Yield 63 (a), 54 (b); mp 240–242°C (decomp). IR
spectrum, ν, cm–1: 3480, 3420 (NH2); 3248 (NH); 2163
(CN); 1673 (C=O); 1653 (C6=C7); 1631 (C=N); 1580,
[10-(2-Hydroxy-1,1-dimethylethylamino)-6,7-
tetramethylene-1,2,3,4,4a,5-hexahydro-12H-benz-
imidazo[2,1-j]quinolin-12-ylidene]malononitrile
(VIIa) (A:B ratio 1:1). Yield 72%, mp 270–272°C
(decomp.) IR spectrum, ν, cm–1: 3289 br (NH, OH);
2195, 2176 (CN); 1668 (C6=C7); 1640 (C=N); 1591,
1
1588 (C=Cquin). H NMR spectrum, δ, ppm: 1.00–
1
1576 (C=Cquin). H NMR spectrum, δ, ppm: 1.02 s
2.50 m (21H), 1.31 s (6H, CH3, A), 1.33 s (6H, CH3,
B), 5.20 t (1H, OH, B, J = 5.4 Hz), 5.25 t (1H, OH, A,
J = 5.2 Hz), 5.79 br.s (1H, 9-H, B), 5.86 br.s (1H, 9-H,
A), 6.07 br.s (1H, 11-H, B), 6.12 br.s (1H, 11-H, A),
8.09 br.s (1H, NH, A), 8.41 br.s (1H, NH, B). Found,
%: C 72.81; H 7.39; N 16.25. Mass spectrum: m/z 428
[M – H]–. C26H31N5O. Calculated, %: C 72.70; H 7.27;
N 16.30. M 429.56.
(6H, CH3, A), 1.05 s (6H, CH3, A), 1.14 s (6H, CH3,
B), 1.20 s (6H, CH3, B), 1.50–2.70 m (24H), 5.57 s
(1H, 9-H, A), 5.59 s (1H, 9-H, B), 6.07 br.s (2H, NH2,
B), 6.34 br.s (2H, NH2, A), 7.50 br.s (1H, 11-H, B),
7.67 br.s (1H, 11-H, A), 8.00 d (1H, NH, A, J =
7.0 Hz), 8.55 d (1H, NH, B, J = 7.0 Hz). Found, %:
C 72.45; H 8.01; N 16.67. Mass spectrum: m/z 515
[M + H]+. C31H42N6O. Calculated, %: C 72.34; H 8.22;
N16.33. M 514.71.
[10-(2-Hydroxy-1,1-dimethylethylamino)-5,7-di-
phenyl-1,2,3,4,4a,5-hexahydro-12H-benzimidazo-
[2,1-j]quinolin-12-ylidene]malononitrile (VIIb)
(A:B ratio 6:1). Yield 66%, mp 255–257°C (decomp.).
IR spectrum, ν, cm–1: 3262 br (NH, OH); 2193, 2167
(CN); 1653 (C6=C7); 1631 (C=N); 1590 (C=Cquin).
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