Synthesis of some isomeric quinoxaline derivatives with 6-azauracil cycle [1]

Article abstract of DOI:10.1002/jhet.5570380633

By diazotization of 3-(2-aminophenyl)-1,2-dihydroquinoxaline 1c, its 3-(4-aminophenyl)-isomer 2c, 3-(2-aminobenzyl)-1,2-dihydroquinoxaline-2-one 3c and its 3-(4-aminobenzyl)-isomer 4c and by azo coupling of formed diazonium salts with ethyl cyanoacetylcar

Full text of DOI:10.1002/jhet.5570380633

Nov-Dec 2001
Synthesis of Some Isomeric Quinoxaline Derivatives
with 6-Azauracil Cycle [1]
1465
Iveta Wiedermannová* and Jan Slouka
Department of Organic Chemistry, Palacky University, Trˇ. Svobody 8, Olomouc 771 46 Olomouc, Czech Republic
Received April 20, 2001
By diazotization of 3-(2-aminophenyl)-1,2-dihydroquinoxaline 1c, its 3-(4-aminophenyl)-isomer 2c, 3-(2-
aminobenzyl)-1,2-dihydroquinoxaline-2-one 3c and its 3-(4-aminobenzyl)-isomer 4c and by azo coupling of
formed diazonium salts with ethyl cyanoacetylcarbamate, corresponding hydrazones 1d-4d were prepared.
Cyclization of these compounds afforded compounds containing two heterocyclic rings with acidic N-H
groups in their molecules: 3-[2-(5-cyano-6-azauracil-1-yl)-phenyl]-1,2-dihydroquinoxaline-2-one 1e, its
4-isomer 2e, 3-[2-(5-cyano-6-azauracil-1-yl)-benzyl]-1,2-dihydroquinoxaline-2-one 3e and its 4-isomer 4e.
The aminoderivative 1c was prepared by the reaction of N-acetylisatine with o-phenylenediamine and by
hydrolysis of prepared N-acetylderivative 1a. The aminoderivative 2c was prepared by the condensation of
4-acetylaminophenylglyoxylic acid with o-phenylenediamine and by hydrolysis of prepared N-acetylderiva-
tive 2a. The aminoderivative 3c was prepared by the condensation of 2-nitrophenylpyruvic acid with
o-phenylenediamine and by the reduction of the formed nitroderivative 3b and finally starting aminoderiva-
tive 4c was obtained by the condensation of o-phenylenediamine with 4-aminophenylpyruvic acid.
J. Heterocyclic Chem., 38, 1465 (2001).
Due to free rotation, non-condensed polynuclear com-
Compounds of this type seem to be very interesting from
the view of their possible conformations and the ability to
form intermolecular hydrogen bonds with substrates on
two bonding centres.
pounds with acidic N-H groups can take up various confor-
mations, which differ in mutual distance of the acidic NH
groups. They should be able to interact with biomolecules
by means of intermolecular hydrogen bonds on two remote
bonding centres and can affect their spatial arrangement.
In the past years we have paid attention to two [2-6] and
three-nuclear [6] compounds where the role of heterocycles
with acidic N-H groups was played by 6-azauracil cycles.
The subject of this communication is the extension of
this area with compounds which, besides the 6-azauracil
cycle, contain also the 2-oxo-1,2-dihydro-quinoxaline
cycle which have somewhat different N-H groups than
6-azauracil ring. We have focused on the synthesis of com-
pounds where the 2-oxo-1,2-dihydro-quinoxaline cycle is
connected in the position 3 with the 6-azauracil cycle by
means of either phenyl or benzyl groups (Scheme 1).
Key intermediates for the synthesis of the mentioned
compounds were 1,2-dihydro-quinoxaline-2-ones substi-
tuted in the position 3 by 2-aminophenyl 1c, 4-aminophenyl
2c, 2-aminobenzyl 3c or 4-aminobenzyl 4c group
(scheme 1). All of these compounds were further trans-
formed in similar ways. By diazotation of these aminoderiv-
atives and by azo coupling of formed diazonium salts with
ethyl cyanoacetylcarbamate in aqueous solution of natrium
acetate, the corresponding ethyl arylhydrazono-cyanoacetyl
carbamates 1d-4d were prepared in good yields. By alkaline
cyclization of these hydrazones the corresponding substi-
tuted 6-azauracils 1e-4e were easily prepared. Starting
aminoderivatives 1c-4c were prepared in good yields from
simple and easily accessible compounds. The compound 1c
was prepared from N-acetylisatine by the reaction with o-
phenylenediamine, according to Schunck and Marchlewski
[7] and modified in reference [8], afforded N-acetylderivate
1a which further underwent alkaline hydrolysis. Starting
compound for compound 2c was 4-acetylaminophenylgly-
oxylic acid, which by the condensation with o-phenylenedi-
amine formed N-acetylderivative 2a which further under-
went the alkaline hydrolysis. This procedure appeared to be
more suitable than the procedure described by Russian
authors [9] based on the oxidative arylation of 1,2-dihydro-
quinoxalin-2-one with aniline. The compound 3c was pre-
pared by the condensation of o-phenylenediamine with
2-nitrophenylpyruvic acid and by the reduction of o-
nitrobenzylderivative 3b. The 4-aminobenzylderivative 4c
was prepared by the condensation of o-phenylenediamine
with 4-aminophenylpyruvic acid.
Scheme 1
For all compounds with two heterocyclic rings 1e-4e, the
mutual distance of N-H groups can be continuously changed
in a relatively wide range depending on the conformation of

1466
Communication to the Editor
Vol. 38
J=7.70, ArH), 8.40 (d, 1H, J=5.15, ArH), 12.41 (s, 1H, NH).
Anal. Calcd. For C H N O (237.26): C, 70.87; H, 4.67; N,
17.71. Found: C, 70.69; H, 4.50; N, 17.49.
independent cycles. Limiting conformations are planar ones
with both minimal and maximal mutual distance of N-H
groups. So e.g., the compound 1e exhibits following limit
conformations:
14 11
3
3-(2-Nitrobenzyl)-1,2-dihydroquinoxaline-2-one (3b).
To the solution of o-nitrophenylpyruvic acid [11] (417.6 mg;
1.99 mmol) in ethanol (10 ml) a solution of o-phenylenediamine
(240.1 mg; 2.24 mmol) in hot ethanol (4 ml) was added. The reac-
tion mixture was refluxed for 5 minutes. Then ethanol was evapo-
rated and water (20 ml) was added to the reaction mixture. The next
day, a crystalline compound was collected with suction, washed
with water and dried in air to yield (45.7 %) of 3b. Recrystallization
from ethanol and water (1:1 v/v) afforded the yellow solid, mp =
-1
232-234 °C, ir: 3197, 3114, 1660 (C=O), 1612, 1515 (C=C) cm ;
1
H nmr: 4.58 (s, 2H, CH ), 7.24 (t, 1H, J=7.41, ArH), 7.33 (m, 1H,
2
ArH), 7.51 (m, 2H, ArH), 7.62 (m, 2H, ArH), 7.76 (m, 1H, ArH),
8.11 (d, 1H, J=8.11, ArH), 12.51 (s, 1H, NH).
(Method of the calculation of distances – see ref. [3])
EXPERIMENTAL
Anal. Calcd. For C H N O (281.27): C, 64.05; H, 3.94; N,
15 11
3 3
14.94. Found: C, 64.00; H, 3.81; N, 14.98.
3-(2-Aminobenzyl)-1,2-dihydroquinoxaline-2-one (3c).
A solution of FeSO •7H O (1.39 g; 5.0 mmol) in water (7 ml)
4
2
Melting points were determined on a Boetius stage and are not
corrected. Infrared spectra were measured in potassium bromide
disks and scanned on an ATI Unicam Genesis FTIR instrument.
was added to the solution of Ba(OH) •8H O in hot water (15 ml).
2
2
The mixture of Fe(OH) and BaSO was quickly collected with
2
4
suction and washed with hot ethanol. The mixture was added to
the solution of 3-(2-nitrobenzyl)-1,2-dihydroquinoxalin-2-one 3b
(140.6 mg; 5.0 mmol) in hot ethanol (30 ml). The reaction mix-
ture was refluxed for 90 minutes on a water bath and then filtered
with suction and washed with hot ethanol. The filtrate was evap-
orated and the solid was mixed with a little water. The compound
was collected with suction, washed with water and dried in air to
yield (71.6 %) of 3c. Recrystallization from ethanol and water
(1:1 v/v) afforded the yellow solid, mp = 185-187 °C, ir: 3330
(NH ), 3154, 2966 (C-H), 1666 (C=O), 1612 (NH ), 1529 (C=C)
The NMR spectra were measured in DMSO-d solutions on a
6
Bruker AMX-360 spectrometer (360 MHz) with TMS as an
internal standard; the reported chemical shifts are in ppm.
Elemental analyses were performed by using an EA 1108
Elemental Analyzer (Fison Instrument).
3-(4-Acetylaminophenyl)-1,2-dihydroquinoxaline-2-one (2a).
To the solution of o-phenylenediamine (216.28 mg; 2.0 mmol)
in hot ethanol (3 ml), the solution of p-acetylaminophenylgly-
oxylic acid [10] (414.38 mg; 2.0 mmol) in hot ethanol (8 ml) was
added. The reaction mixture was refluxed for 5 minutes. The next
day upon cooling, a crystalline compound was collected with
suction, washed with water and dried in air to yield (81.5 %) of
2a. Recrystallization from ethanol and water (1:1 v/v) afforded
the yellow solid, mp = 270-272 °C, ir: 3240 (N-H), 3095 (C-H),
2
2
-1
1
cm ; H nmr: 4.62 (s, 2H, CH ), 5.21 (s, 2H, NH ), 7.29 (m, 4H,
2
2
ArH), 7.50 (t, 2H, J=7.52, ArH), 7.61 (m, 1H, ArH), 7.75 (t, 1H,
J=7.51, ArH), 12.47 (s, 1H, NH).
Anal. Calcd. For C
H N O (251.29): C, 71.70; H, 5.21; N,
15 13 3
16.72. Found: C, 71.62; H, 5.29; N, 16.59.
-1
1
3050 (C-H), 1668 (C=O), 1598 (C=C), 1477 cm ; H nmr: 2.14
3-(4-Aminobenzyl)-1,2-dihydroquinoxaline-2-one (4c).
(s, 3H, CH ), 7.36 (m, 2H, ArH), 7.55 (m, 1H, ArH), 7.74 (d, 2H,
3
A solution of p-aminophenylpyruvic acid hydrochloride [12]
(431.36 mg; 2.0 mmol) in ethanol (40 ml) was added to the solu-
tion of o-phenylenediamine (216.28 mg; 2.0 mmol) in hot
ethanol (8 ml). The reaction mixture was refluxed for 5 minutes
and then taken down. The solid was dissolved in water (60 ml)
and pH was adjusted to 7 using ammonia solution. The next day,
a crystalline compound was collected with suction, washed with
water and dried in air to yield (95.6 %) of 4c. Recrystallization
from ethanol and water (1:1 v/v) afforded the yellow solid, mp =
185-187 °C, ir: 3442, 3330, 3099, 3002, 1666 (C=O), 1612, 1517
J=8.82, ArH), 7.85 (d, 1H, J=8.00, ArH), 8.41 (d, 2H, J=8.82,
ArH), 10.23 (s, 1H, NH), 12.56 (s, 1H, NH).
Anal. Calcd. For C
H N O (279.3): C, 68.81; H, 4.69; N,
16 13 3 2
15.04. Found: C, 68.70; H, 4.58; N, 15.13.
3-(4-Aminophenyl)-1,2-dihydro-quinoxaline-2-one (2c).
The mixture of acetylderivative (2a) (12.0g; 10.025 mmol) and
the solution of KOH (5.01g; 89.299 mmol) in a mixture of ethanol
(25.0 ml) and water (12.5 ml) was heated until a solution formed.
The solution was then refluxed for 4 hours. Then, ethanol was
evaporated from the reaction mixture by heating on a water bath
and the solution was acidified with acetic acid to pH=5. The next
day, a yellow crystalline compound was collected with suction,
washed with water and dried in air to yield (94.7 %) of 2c.
Recrystallization from ethanol and water (1:1 v/v) afforded the
yellow solid, mp = 197-198 °C (ref. [9] gives mp = 221-223 °C),
-1
1
cm ; H nmr: 3.98 (s, 2H, CH ), 4.93 (s, 2H, NH ), 6.51 (d, 2H,
2
2
J=4.43, ArH), 7.02 (d, 2H, J=8.38, ArH), 7.31 (m, 2H, ArH), 7.51
(m, 1H, ArH), 7.76 (m, 1H, ArH), 12.35 (s, 1H, NH).
Anal. Calcd. For C
H N O (251.29): C, 71.70; H, 5.21; N,
15 13 3
16.72. Found: C, 71.62; H, 5.29; N, 16.59.
Ethyl 2-(2-Oxo-1,2-dihydro-quinoxaline-3-yl)-phenylhydra-
zonocyanoacetylcarbamate (1d).
ir: 3305 (NH ), 3118, 3100, 3008 (C-H), 1666 (C=O), 1610
2
-1
1
(NH ), 1598 (C=C), 1515 (NO ), 1473, 1351 (NO ) cm ;
H
2
2
2
nmr: 5.77 (s, 2H, J=5.47, NH ), 6,67 (d, 2H, J=5.14, ArH), 7.35
A suspenzion of amino derivative (1c) [7,8] (0.48 g; 2.02
2
(d, 1H, J=7.68, ArH), 7.75 (t, 2H, J=7.70, ArH), 8.33 (d, 2H,
mmol) in a mixture of water (35 ml) and HCl (3.0 ml, 37%)

Nov-Dec 2001
Comunication to the Editor
1467
was cooled on an ice bath and treated with a solution of
Anal. Calcd. For C H N O (418.41): C, 60.28; H, 4.34; N,
21 18 6 4
NaNO (140.0 mg; 2.0 mmol) in water (4 ml). The suspension
20.09. Found: C, 60.35; H, 4.40; N, 20.32.
2
dissolved slowly during 35 minutes of stirring. The reaction
mixture was filtered from a small amount of indolo[2,3-
b]quinoxaline and the filtrate was added portionwise to a
stirred mixture obtained by dissolving ethyl cyanoacetylcarba-
mate (0.42 mg; 2.691 mmol) in warm water (110 ml), cooling
2-[2-(2-Oxo-1,2-dihydroquinoxaline-3-yl)-phenyl]-3,5-dioxo-
2,3,4,5-tetrahydro-1,2,4-triazin-6-carbonitril (1e).
A mixture of hydrazone 1d (0.413 g; 1.0 mmol), Na CO
2
3
(120.0 mg) and water (10 ml) was heated on a boiling water bath
until a solution was formed and then for an additional 15 minutes.
The solution was then allowed to cool down and acidified with
37% HCl to pH=1. After several hours, the crystalline solid was
collected by suction, washed with a little water and dried in air to
yield (74.6 %) of 1e. Recrystallization from ethanol and water
(1:1 v/v) afforded the yellow solid, mp = 178-179 °C, ir: 3448
on an ice bath, adding CH COONa (5 g) and crushed ice. The
3
next day, a crystalline compound was collected with suction,
washed with water and dried in air to yield (94.1 %) of 1d.
Recrystallization from ethanol and water (1:1 v/v) afforded
the yellow solid, mp = 225-227 °C, ir: 3241 (N-H), 2981
(C-H), 2211 (C≡N), 1776 (C=O), 1743 (C=O), 1652, 1230
-1
1
(C-O) cm ; H nmr: 1.29 (t, 3H, J=7.0, CH ), 4.16 (q, 2H,
-1
3
(N-H), 3220, 3048 (C-H), 2244 (C≡N), 1707 (C=O), 1660 cm ;
J=7.0, CH ), 7.37 (m, 3H, ArH), 7.62 (m, 2H, ArH), 8.00 (d,
1
2
H nmr: 7.39 (m, 2H, ArH), 7.70 (m, 5H, ArH), 8.05 (m, 1H,
1H, J=8.03, ArH), 8.30 (m, 2H, ArH), 10.70 (s, 1H, NH),
12.81 (s, 1H, NH), 12.84 (s, 1H, NH).
ArH), 12.74 (s, 1H, NH), 12.82 (s, 1H, NH).
Anal. Calcd. For C
H N O (358.32): C, 60.34; H, 2.81; N,
18 10 6 3
Anal. Calcd. For C
H N O •1/2H O (413.39): C, 58.11; H,
20 16 6 4 2
23.45. Found: C, 60.29; H, 2.80; N, 23.15.
4.14; N, 20.33. Found: C, 58.25; H, 4.00; N, 20.01.
2-[4-(2-Oxo-1,2-dihydroquinoxaline-3-yl)-phenyl]-3,5-dioxo-
2,3,4,5-tetrahydro-1,2,4-triazin-6-carbonitril (2e).
Ethyl 4-(2-Oxo-1,2-dihydro-quinoxaline-3-yl)-phenylhydra-
zonocyanoacetylcarbamate (2d).
This compound was prepared by an analogous procedure as
that of 1e from hydrazone 2d, by using hydrazone 2d (0.413g;
This compound was prepared analogically to 1d from amino
derivative 2c by using amino derivative 2c (0.48 g, 2.02 mmol),
HCl (3 ml, 37%), water (45 ml) in the yield (63.3 %) of 2d.
Recrystallization from ethanol and water (1:1 v/v) afforded the yel-
low solid, mp = 218-220 °C, ir: 2985 (C-H), 2215 (C≡N), 1776
1.0 mmol), Na CO (120.0 mg), water (15 ml, in a yield (80.6 %)
2
3
of 2e. Recrystallization from ethanol and water (1:1 v/v) afforded
the yellow solid, mp = 303-305 °C, ir: 3035 (C-H), 2933, 2244
-1
1
(C≡N), 1712 (C=O), 1660, 1612 cm ; H nmr: 7.40 (d, 2H,
J=7.75, ArH), 7.60 (m, 3H, ArH), 7.91 (d, 1H, J=7.80, ArH), 8.48
(m, 2H, ArH), 12.68 (s, 1H, NH), 12.71 (s, 1H, NH).
-1 1
(C=O), 1704 (C=O), 1666, 1604, 1191 (C-O) cm ; H nmr: 1.32 (t,
3H, J=7.06, CH ), 4.25 (d, 2H, J=7.10, CH ), 7.36 (m, 2H, ArH),
3
2
7.57 (m, 1H, ArH), 7.86 (d, 3H, J=8.85, ArH), 8.47 (d, 2H, J=8.90,
ArH), 10.68 (s, 1H, NH), 12.31 (s, 1H, NH), 12.59 (s, 1H, NH).
Anal. Calcd. For C
H N O (358.32): C, 60.34; H, 2.81; N,
18 10 6 3
23.45. Found: C, 60.29; H, 2.74; N, 23.52.
Anal. Calcd. For C
H N O (404.38): C, 59.40; H, 3.99; N,
20 16 6 4
20.78. Found: C, 59.25; H, 3.79; N, 20.59.
2-[2-(2-Oxo-1,2-dihydroquinoxaline-3-ylmethyl)-phenyl]-3,5-
dioxo-2,3,4,5-tetrahydro-1,2,4-triazin-6-carbonitril (3e).
Ethyl 2-(2-Oxo-1,2-dihydro-quinoxaline-3-ylmethyl)-phenyl-
hydrazonocyanoacetylcarbamate (3d).
This compound was prepared by an analogous procedure as
that of 1e from hydrazone 3d in the yield (78.3 %) of 3e.
Recrystallization from ethanol and water (1:1 v/v) afforded the
yellow solid, mp = 165-166 °C, ir: 3068, 3009 (C-H), 1750
This compound was prepared in analogically 1d from amino
derivative 3c by using amino derivative 3c (0.5076 g, 2.02 mmol),
HCl (3 ml, 37%), water (60 ml) in the yield (69.3 %) of 3d.
Recrystallization from ethanol and water (1:1 v/v) afforded the yel-
low solid, mp = 197-198 °C, ir: 3062 (C-H), 2985, 2211 (C≡N),
-1
1
(C=O), 1655, 1600, 1549 cm ; H nmr: 4.15 (s, 2H, CH ), 7.31
2
(m, 2H, ArH), 7.45 (m, 2H, ArH), 7.55 (t, 3H, J=7.20, ArH), 7.64
(d, 1H, J=6.60, ArH),12.47 (s, 1H, NH), 13.08 (s, 1H NH).
-1
1
1772 (C=O), 1720 (C=O), 1658, 1612 cm ; H nmr: 1.28 (t, 3H,
J=7.09, CH ), 4.21 (d, 2H, J=7.09, CH ), 4.26(s, 2H, CH ), 7.23(t,
Anal. Calcd. For C
H N O (372.34): C, 61.29; H, 3.25; N,
3
2
2
19 12 6 3
1H, J=7.39, ArH), 3.36(m, 3H, ArH), 7.47(d, 1H, J= 7.39, ArH),
7.56 (m, 1H, ArH), 7.94 (d, 1H, J=7.88, ArH), 8.02 (d, 1H, J=7.92,
ArH), 10.69 (s, 1H, NH), 12.04 (s, 1H, NH), 12.79 (s, 1H, NH).
22.57. Found: C, 61.18; H, 3.17; N, 22.30.
2-[4-(2-Oxo-1,2-dihydroquinoxaline-3-ylmethyl)-phenyl]-3,5-
dioxo-2,3,4,5-tetrahydro-1,2,4-triazin-6-carbonitril (4e).
Anal. Calcd. For C
H N O (418.41): C, 60.28; H, 4.34; N,
21 18 6 4
20.09. Found: C, 60.11; H, 4.29; N, 19.85.
This compound was prepared analogically to 1e from hydra-
zone 4d in the yield (76.0 %) of 4e. Recrystallization from
ethanol and water (1:1 v/v) afforded the yellow solid, mp = 190-
191 °C, ir: 3100, 3079, 3024 (C-H), 1736 (C=O), 1666, 1600
Ethyl 4-(2-Oxo-1,2-dihydro-quinoxaline-3-ylmethyl)-phenyl-
hydrazonocyanoacetylcarbamate (4d).
This compound was prepared analogically to 3d from
amino derivative 4c in the yield (63.3 %) of 4d.
Recrystallization from ethanol and water (1:1 v/v) afforded
the yellow solid, mp = 175-176 °C, ir: 3226 (N-H), 3189, 3056
(C-H), 2983 (C-H), 2904, 2213 (C≡N), 1768 (C=O), 1666,
-1
1
cm ; H nmr: 4.34 (s, 2H, CH ), 7.40 (m, 4H, ArH), 7.68 (m,
2
4H, ArH), 12.55 (s, 1H, NH), 13.18 (s, 1H NH).
Anal. Calcd. For C
H N O (372.34): C, 61.29; H, 3.25; N,
19 12 6 3
22.57. Found: C, 61.00; H, 3.30; N, 22.19.
-1
1
1610 (C=C), 1200 (C-O) cm ; H nmr: 1.30 (t, 3H, J=7.06,
CH ), 4.21 (m, 4H, CH ), 7.31 (t, 2H, J=7.67, ArH), 7.41 (t,
Acknolwedgement.
3
2
Financial support for this work by the Ministry of Education,
Youth and Sport of Czech Republic No CEZ: MSM 153100008 is
gratefully acknowledged.
2H, J=8.50, ArH), 7.53 (t, 1H, J=7,14, ArH), 7.68 (d, 2H,
J=8.51, ArH), 7,76 (t, 1H, J=7.45, ArH), 10.53 (s, 1H, NH),
12.44 (s, 1H, NH), 12.66 (s, 1H, NH).

1468
Communication to the Editor
Vol. 38
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*
Author to whom correspondence should be sent: E-mail: wie-
dermannova@prfnw.upol.cz, Fax:++420-68-5634405.
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