Fused polycyclic nitrogen-containing heterocycles : 1116. Selenazolo[3,4-a]-and thiazolo[3,4-a]quinoxalin-4(5H)-ones

Article abstract of DOI:10.1007/s11172-007-0334-3

Upon treatment with acetic acid, 3-(2-phenyl-1-selenocyanatoethyl)-, 3-(3-phenyl-1-selenocyanatopropyl)quinoxalin-2(1H)-ones and their thio analogs undergo intramolecular condensation to form selenazolo-and thiazolo[3,4-a] quinoxalines.

Full text of DOI:10.1007/s11172-007-0334-3

Russian Chemical Bulletin, International Edition, Vol. 56, No. 10, pp. 2127—2130, October, 2007
2127
Fused polycyclic nitrogenꢀcontaining heterocycles
16.* Selenazolo[3,4ꢀа]ꢀ and thiazolo[3,4ꢀа]quinoxalinꢀ4(5H )ꢀones
V. A. Mamedov,ꢀ D. F. Saifina, E. A. Berdnikov, and I. Kh. Rizvanov
A. E. Arbuzov Institute of Organic and Physical Chemistry,
Kazan Research Center of the Russian Academy of Sciences,
8 ul. Akad. Arbuzova, 420088 Kazan, Russian Federation.
Fax: +7 (843) 273 2253. Eꢀmail: mamedov@iopc.knc.ru
Upon treatment with acetic acid, 3ꢀ(2ꢀphenylꢀ1ꢀselenocyanatoethyl)ꢀ, 3ꢀ(3ꢀphenylꢀ1ꢀ
selenocyanatopropyl)quinoxalinꢀ2(1H )ꢀones and their thio analogs undergo intramolecular
condensation to form selenazoloꢀ and thiazolo[3,4ꢀa]quinoxalines.
Key words: selenazolo[3,4ꢀa]quinoxalines, thiazolo[3,4ꢀa]quinoxalines, intramolecular conꢀ
densation, substituted quinoxalines, IR, NMR spectra.
Azolo[a]quinoxalines and their 4,5ꢀdihydro derivaꢀ
tives show various biological and pharmacological propꢀ
erties2—6 and are of use in the synthesis of many biologiꢀ
cally important compounds and drugs.7—10 In this conꢀ
nection, numerous methods for the synthesis of imidꢀ
azo[1,5ꢀa]ꢀ,11—15 thiazolo[3,4ꢀa]ꢀ,16—21 and especially
pyrrolо[1,2ꢀa]quinoxalines22—26 have been elaborated.
For example, a number of imidazo[1,5ꢀa]ꢀ (1),13—15
thiazolo[3,4ꢀa]ꢀ (2),20,21 and pyrrolо[1,2ꢀa]quinoxalines
(3)26 were synthesized by the reaction of 3ꢀ(αꢀchloroꢀ
benzyl)quinoxalinꢀ2(1H )ꢀone with potassium cyanate
and thiocyanate, thiourea, and compounds with active
methylene group, which were used as synthetic equivaꢀ
lents of N–=C+, S–−C+, and RC+(–)=C–(+)R´ dipoles.
In contrast to the diversity of azoloquinoxalines, their
selenium analogs, i.e., selenazolo[3,4ꢀa]quinoxalines,
which, in comparison with the other representatives of
azolo[a]quinoxalines, are of much interest for their bioꢀ
logical and physical and chemical properties, so far are
not synthesized.
As it follows from the proposed by us methods of
synthesis,13,26,27 based on the retroꢀsynthetic analysis of
azolo[a]quinoxaline structures, a selenium analog of poꢀ
tassium thiocyanate, i.e., potassium selenocyanate, could
serve as the synthetic equivalent of the twoꢀatomic fragꢀ
ment, the reaction of which with 3ꢀ(αꢀchlorophenylꢀ
alkyl)quinoxalinꢀ2(1H )ꢀones (4a,b) would lead to the key
intermediates on the way to the desired tricyclic systems.
Nucleophilic substitution of chlorine atom in comꢀ
pounds 4a,b (see Experimental) proceeds in DMF in the
presence of the excess of KSeCN under argon atmosphere
at room temperature for chlorophenylethylquinoxalinone
4a and at 40 °C for chlorophenylpropylquinoxalinone 4b.
The subsequent aqueous treatment leads to the formation
of light pink crystals of compounds 5a,b (Scheme 1). In
the IR spectra of the latter, a characteristic absorption
band of SeCN group in the region 2150—2155 cm–1 is
presented, whereas in the 1Н NMR spectra, signals of the
methyne protons are upfield shifted by ~0.5 ppm in comꢀ
parison with the corresponding signals in the starting comꢀ
pounds 4a,b, signals of the methyne protons in which are
observed at 5.67 and 5.43 ppm, respectively (see Experiꢀ
mental).
Selenazoloꢀannulation of quinoxaline 5a was carried
out in boiling acetic acid for 15 h, whereas only 5 h were
required for 5b (Scheme 2). During this, the crystalline
compounds with high melting points (292—294 °C (6a)
and 305—308 °C (6b)) were formed, the latter were by 90
and 110 °C higher then the melting points of the correꢀ
1: R = H, OH, SH, SAlk, Ar; R´ = Ph, CO2Et
2: Z = O, S, NH, NAr, NAc, Nꢀnaphthyl, Nꢀthiazolyl; R´ = Me, Ar
3: R = Me, Ph, NH2, OEt; R´ = Ac, Bz, CN, CONH2
* For Part 15, see Ref. 1.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 2055—2058, October, 2007.
1066ꢀ5285/07/5610ꢀ2127 © 2007 Springer Science+Business Media, Inc.

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Mamedov et al.
1
Scheme 2
In the Н NMR spectrum of the sulfur analog of triꢀ
cycle 6a, i.e., 1ꢀacetyliminoꢀ3ꢀbenzylthiazolo[3,4ꢀа]quinꢀ
oxalinꢀ4(5H )ꢀone (7), purꢀ
posely synthesized from the
corresponding 3ꢀ(αꢀthiocyanꢀ
atоphenylethyl)quinoxalinꢀ
2(1H )ꢀone, according to the
procedure similar to that
for the preparation of comꢀ
pound 6a, the doublet of
Н(9) proton of thiazoloquinꢀ
oxaline appears close to the region (9.92 ppm, J = 8.4 Hz)
for the selenium derivatives 6a,b.
It should be noted that a general tendency of the
downfield movement of chemical shifts of Н(9) protons
going from pyrrolо[1,2ꢀa]quinoxalines26 (8.15 ppm)
through imidazo[1,5ꢀa]ꢀ13 (8.60 ppm) and thiazoꢀ
lo[3,4ꢀа]quinoxalines19—21 (9.42 ppm) to selenazoꢀ
lo[3,4ꢀа]quinoxalines (≈ 10.0 ppm) is observed.
n = 1 (a), 2 (b)
sponding starting compounds, which is characteristic of
the condensed quinoxaline systems.20,26 The disappearꢀ
ance of the absorption band of SeCN group in the
IR spectrum is also an evidence in favor of the formation
of selenazolo[3,4ꢀa]quinoxaline tricyclic system, as well
as the changes in the 1Н NMR spectra, where, along
with the signals of the protons of the aromatic rings and
carbamoyl group, the chemical shifts and multiplicity
of signals of the protons at sp3ꢀcarbon atoms are
changed, namely, instead of signals of АВХꢀsystem of
—CН—CН2— group of compound 5a and complicated
multiplets of АВCDХꢀsystem of —CН—CН2—CН2—
group of compound 5b, a singlet of CН2 group (4.8 ppm)
of compound 6a and two triplets of —CН2—CН2— group
Experimental
Melting points were determined on the Boetius heating table.
IR spectra were recorded on a Bruker Vectorꢀ22 Fourier specꢀ
trometer in Nujol for all the compounds. Mass spectra of elecꢀ
tron ionization were recorded on a ThermoQuest/Finnigan
TRACE MS quadruple massꢀspectrometer, insertion of the
samples were carried out through the direct injection system
1
with water cooling. H NMR spectra of compounds 4а,b, 5a,b,
and 6b were recorded on a Bruker MSLꢀ400 spectrometer
(400.13 MHz), of compounds 6a and 7, on a Bruker Avanceꢀ600
spectrometer (600.13 МHz) in DMSOꢀd6 for all the compounds.
Chemical shifts are given in δ scale with signals of residual
1
(3.0—3.7 ppm) of compound 6b appear. In the Н NMR
spectrum, a doublet of Н(9) proton of compounds 6a,b is
downfield shifted by 2.1 ppm in comparison with the
signal of Н(5) proton in the starting compounds 5a,b
and is observed at 9.9 ppm, which is diagnostical for
azolo[a]ꢀannulated quinoxaline systems.27,28
protons in DMSOꢀd6 (δ 2.54 ppm) as the internal standard.
Н
3ꢀ(1ꢀChloroꢀ2ꢀphenylethyl)quinoxalinꢀ2(1H )ꢀone (4а). The
product was obtained by the reaction of methyl 3ꢀchloroꢀ2ꢀoxoꢀ
4ꢀphenylbutanoate29 with оꢀphenylenediamine in quantitative
yield according to the procedure elaborated by us earlier,30 m.p.
199—200 °C. Found (%): C, 67.31; Н, 4.45; N, 9.97; Cl, 12.38.
C16H13ClN2O. Calculated (%): C, 67.49; Н, 4.60; N, 9.84;
Cl, 12.45. IR, ν/cm–1: 503, 589, 698. 709, 755, 761, 907, 1031,
1432, 1482, 1498, 1577, 1599, 1609, 1661, 3065, 3157. 1H NMR,
δ: 3.44 (dd, 1 Н, CН2Ph, Jab = 13.93 Hz, Jax = 7.96 Hz); 3.69
(dd, 1 H, CН2Ph, Jab = 13.93 Hz, Jbx = 6.97 Hz); 5.67 (dd, 1 H,
CHCl, Jax = 7.96 Hz, Jbx = 6.97 Hz); 7.20 (ddd, 1 Н, Н(6), J =
7.29 Hz, J = 6.31 Hz, J = 1.99 Hz); 7.25—7.35 (m, 5 Н, Ph);
7.37 (d, 1 Н, Н(8), J = 7.96 Hz); 7.57 (ddd, 1 Н, Н(7), J =
8.30 Hz, J = 7.30 Hz, J = 1.32 Hz); 7.83 (d, 1 H, Н(5), J =
8.63 Hz); 12.48 (br.s, 1 Н, NH).
Scheme 2
3ꢀ(1ꢀChloroꢀ3ꢀphenylpropyl)quinoxalinꢀ2(1H )ꢀone (4b). The
product was obtained similarly30 with the use of methyl 3ꢀchloroꢀ
2ꢀoxoꢀ5ꢀphenylpentanoate,29 m.p. 201—203 °C. Found (%):
C, 68.13; Н, 4.93; N, 9.55; Cl, 11.75. C17H15ClN2O. Calcuꢀ
lated (%): C, 68.34; Н, 5.06; N, 9.38; Cl, 11.87. IR, ν/cm–1
:
586, 701, 738, 751, 764, 906, 1289, 1429, 1560, 1608, 1677,
2720, 3021, 3067. 1H NMR, δ: 2.75—2.83, 2.88—2.94 (both m,
4 Н each, CН2CН2); 5.40—5.45 (m, 1 Н, CНCl); 7.20—7.40
(m, 7 Н, Ph + Н(6) and Н(8)); 7.60 (dd, 1 Н, Н(7), J = 7.96 Hz,

Selenazoloꢀ and thiazolo[3,4ꢀa]quinoxalinꢀ4(5H )ꢀones Russ.Chem.Bull., Int.Ed., Vol. 56, No. 10, October, 2007 2129
J = 7.32 Hz); 7.82 (d, 1 Н, Н(5), J = 7.96 Hz); 12.48
(br.s, 1 Н, NH).
3ꢀ(2ꢀPhenylꢀ1ꢀthiocyanatoethyl)quinoxalinꢀ2(1H )ꢀone. A soꢀ
lution of 3ꢀ(1ꢀchloroꢀ2ꢀphenylethyl)quinoxalinꢀ2(1H )ꢀone 4a
(0.30 g, 1.1 mmol) and KSCN (0.32 g, 3.3 mmol) in DMF
(10 mL) was stirred for 7 days and quenched with water. The
crystals formed were filtered off, washed with water (3×10 mL),
and dried in air. The yield was 0.30 g (93%), m.p. 207—209 °C.
Found (%): C, 66.21; Н, 4.19; N, 13.56; S, 10.97. C17H13N3OS.
Calculated (%): C, 66.43; Н, 4.26; N, 13.67; S, 10.43. IR,
ν/cm–1: 405, 471, 502, 592, 704, 764, 919, 953, 1030, 1461,
1484, 1497, 1605, 1664, 2156, 3087, 3168. 1H NMR, δ: 3.48 (dd,
1 Н, CН2Ph, Jab = 13.89 Hz, Jax = 7.89 Hz); 3.71 (dd, 1 Н,
CН2Ph, Jab = 13.89 Hz, Jbx = 6.86 Hz); 5.18 (dd, 1 H, CHSCN,
Jax = 7.89 Hz, Jbx = 6.86 Hz); 7.22—7.42 (m, 7 Н, Ph + Н(6),
Н(8)); 7.62 (dd, 1 Н, Н(7), J = 8.24 Hz, J = 7.52 Hz); 7.87 (d,
1 Н, Н(5), J = 8.24 Hz); 12.64 (br.s, 1 Н, NH).
1ꢀAcetyliminoꢀ3ꢀbenzylthiazolo[3,4ꢀа]quinoxalinꢀ4(5H )ꢀone
(7). A solution of 3ꢀ(2ꢀphenylꢀ1ꢀthiocyanatoethyl)quinoxalinꢀ
2(1H )ꢀone (0.2 g, 0.65 mmol) in acetic acid (10 mL) was reꢀ
fluxed for 8.5 h, the reaction mixture was kept for 7 h at room
temperature, the crystals formed were filtered off. The yield was
0.125 g (55%), m.p. 296—298 °C. Found (%): C, 65.10; Н, 4.32;
N, 11.90; S, 9.97. C19H15N3O2S. Calculated (%): C, 65.31;
Н, 4.33; N, 12.03; S, 9.18. IR, ν/cm–1: 603, 657, 697, 762, 775,
791, 982, 1162, 1240, 1271, 1293, 1309, 1331, 1405, 1443,
1497,1508, 1582, 1611, 1671, 3030, 3127, 3184. 1H NMR, δ:
2.33 (s, 3H, CH3CO); 4.77 (s, 2 Н, CН2); 7.20—7.40 (m, 8 Н,
Ph + Н(6), Н(7), Н(8)); 9.92 (d, 1 Н, Н(9), J = 8.4 Hz); 11.46
(br.s, 1 Н, NH).
3ꢀ(2ꢀPhenylꢀ1ꢀselenocyanatoethyl)quinoxalinꢀ2(1H )ꢀone
(5a). A solution of 3ꢀ(1ꢀchloroꢀ2ꢀphenylethyl)quinoxalinꢀ
2(1H )ꢀone (4a) (0.31 g, 1.1 mmol) and KSеCN (0.47 g,
3.3 mmol) in DMF (10 mL) was stirred for 8 h under argon,
then, the reaction mixture was kept for 48 h and quenched with
water. The crystals formed were filtered off, washed with water
(3×10 mL), and dried in air. The yield was 0.37 g (94%),
m.p. 202—204 °C. Found (%): C, 57.23; Н, 3.53; N, 11.98.
C17H13N3OSe. Calculated (%): C, 57.64; Н, 3.70; N, 11.86. IR,
ν/cm–1: 433, 468, 494, 592, 700, 754, 767, 931, 1155, 1608,
1668, 2151, 3063, 3329. 1H NMR, δ: 3.72 (dd, 1 Н, CН2Ph,
Jab = 13.70 Hz, Jax = 8.58 Hz); 3.81 (dd, 1 Н, CН2Ph, Jab
=
13.70 Hz, Jbx = 5.82 Hz); 5.17 (dd, 1 H, CHSeCN, Jax = 8.58 Hz,
Jbx = 5.82 Hz); 7.24—7.44 (m, 7 Н, Ph + Н(6), Н(8)); 7.50 (dd,
1 Н, Н(7), J = 7.56 Hz, J = 7.52 Hz); 7.83 (d, 1 Н, Н(5), J =
7.88 Hz); 12.46 (br.s, 1 Н, NH).
3ꢀ(3ꢀPhenylꢀ1ꢀselenocyanatopropyl)quinoxalinꢀ2(1H )ꢀone
(5b). Compound 5b was obtained similarly to 5a from
3ꢀ(1ꢀchloroꢀ3ꢀphenylpropyl)quinoxalinꢀ2(1H )ꢀone (4b) (1.00 g,
3.3 mmol) and KSеCN (1.45 g, 9.9 mmol) at 40 °C. The yield
was 1.00 g (81%), m.p. 196—197 °C. Found (%): C, 58.41;
Н, 3.95; N, 11.56. C18H15N3OSe. Calculated (%): C, 58.70;
Н, 4.11; N, 11.41. IR, ν/cm–1: 414, 487, 593, 752, 915, 945,
1348, 1496, 1553, 1607, 1666, 2154, 2720, 3087, 3220. 1H NMR,
δ: 2.60—2.95 (m, 4 Н, CН2CН2); 4.90—5.00 (m, 1 Н,
CНSeCN); 7.15—7.41 (m, 7 Н, Ph + Н(6), Н(8)); 7.59 (dd,
1 Н, Н(7), J = 8.24 Hz, J = 6.84 Hz); 7.83 (d, 1 Н, Н(5), J =
8.24 Hz); 12.57 (br.s, 1 Н, NH).
This work was financially supported by the Russian
Foundation for Basic Research (Project No. 07ꢀ03ꢀ
00613).
1ꢀAcetyliminoꢀ3ꢀbenzylselenazolo[3,4ꢀа]quinoxalinꢀ4(5H )ꢀ
one (6a). A solution of compound 5a (0.2 g, 0.56 mmol) in
acetic acid (10 mL) was refluxed for 15 h, the reaction mixture
was kept for 12 h at room temperature, the crystals formed were
filtered off and recrystallized from acetic acid. The yield was
0.092 g (41%), m.p. 292—294 °C. Found (%): C, 57.39; Н, 3.67;
N, 10.49. C19H15N3O2Se. Calculated (%): C, 57.58; Н, 3.81;
N, 10.60. IR, ν/cm–1: 698, 761, 1230, 1272, 1304, 1328, 1400,
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Received 21 July, 2006;
in revised form 27 August, 2007