Abstract
The starting material 4-amino-4
H
-[1,2,4]triazino[5,6-b]indole-3-thiol
1
was synthesized by refluxing a mixture of isatin and thiocarbohydrazide in glacial acetic acid. Compound
1
reacted with various types of reagents including ammonia, hydrazine hydrate, semicarbazide HCl in various media to give triazino-[5,6-b]indole-3,4-diamine
2
, 3-hydrazino-4
H
-[1,2,4]triazino[5,6-b]indol-4-amine
3
and 3,4-dihydro[1,2,4,5]-tetrazino[6',1':3,4][1,2,4]triazino[5,6-
b
]indole-2(1
H
)-one
5
, respectively. Reactions of compounds
2
and
3
with ethyl chloroformate in boiling DMF led to 1
H
-[1,2,4]triazolo[5',1':3,4][1,2,4]triazino[5,6-b]indol-3(4
H
)-one
4
and compound
5
, respectively. Microwave irradiation of compound
1
with maleic anhydride yielded 1-(3-mercapto-4
H
-[1,2,4]triazino[5,6-
b
]indol-4-yl)-1
H
-pyrrole-2,5-dione
6
. Reactions of
1
with different aldehydes in EtOH-HCl gave the corresponding Schiff bases. Treatment of substrate 1 with NH
4
SCN in glacial AcOH yielded
N
-(3-mercapto-4H-[1,2,4]triazino[5,6-b]indol-4-yl)thiourea
9
and 1
H
-[1,2,4]triazolo[5',1':3,4][1,2,4]-triazino[5,6-
b
]indole-3(2
H
,4
H
)-thione
10
, respectively. Reaction of substrate 1 with phenyl isothiocyanate in refluxing dioxan gave
N
-(3-mercapto-4
H
-[1,2,4]triazino[5,6-
b
]indol-4-yl)-
N
'-phenylthiourea
11
. Its reaction with ethyl cyanoacetate upon refluxing in EtONa/EtOH afforded ethyl (4-amino-4
H
-[1,2,4]triazino[5,6-
b
]-indol-3-yl)(cyano)acetate
12
, which upon boiling gave ethyl 2-amino-1H-pyrazolo[5',1':3,4][1,2,4]triazino-[5,6-
b
]indole-3-carboxylate
13
. Structures of new compounds were confirmed by elemental analysis and spectroscopic data (IR,
1
H and
13
C NMR). The newly synthesized compounds were subjected to the biological screening, which demonstrated promising results.