Regioselective synthesis of 3-sulfanyl-5H-naphtho[2,3-e][1,3,4] triazino[3,4-b][1,3,4]thiadiazole-6,11-dione and its derivatives

Article abstract of DOI:10.1080/17415993.2010.535209

Regioselective synthesis of novel 3-sulfanyl-5H-naphtho[2,3-e][1,3,4] triazino[3,4-b][1,3,4]thiadiazole-6,11-dione (3) has been achieved by the condensation of 2-bromo-3-hydroxynaphthalene-1,4-dione (1) with 4-amino-4H-1,2,4-triazole-3,5-dithiol (2) in DM

Full text of DOI:10.1080/17415993.2010.535209

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Regioselective synthesis of 3-
sulfanyl-5H-naphtho[2,3-e][1,3,4]
triazino[3,4-b][1,3,4]thiadiazole-6,11-
dione and its derivatives
Vakiti Srinivas a & Vedula Rajeswar Rao a
a Department of Chemistry, National Institute of Technology,
Warangal, 506004, Andhra Pradesh, India
Published online: 29 Nov 2010.
To cite this article: Vakiti Srinivas & Vedula Rajeswar Rao (2011): Regioselective synthesis of 3-
sulfanyl-5H-naphtho[2,3-e][1,3,4] triazino[3,4-b][1,3,4]thiadiazole-6,11-dione and its derivatives,
Journal of Sulfur Chemistry, 32:1, 99-104
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Journal of Sulfur Chemistry
Vol. 32, No. 1, February 2011, 99–104
Regioselective synthesis of 3-sulfanyl-5H-naphtho[2,3-e][1,3,4]
triazino[3,4-b][1,3,4]thiadiazole-6,11-dione and its derivatives
Vakiti Srinivas and Vedula Rajeswar Rao*
Department of Chemistry, National Institute of Technology, Warangal 506004, Andhra Pradesh, India
(Received 2 August 2010; final version received 24 October 2010)
Regioselective synthesis of novel 3-sulfanyl-5H-naphtho[2,3-e][1,3,4]triazino[3,4-b][1,3,4]thiadiazole-
6,11-dione (3) has been achieved by the condensation of 2-bromo-3-hydroxynaphthalene-1,4-dione (1)
with 4-amino-4H-1,2,4-triazole-3,5-dithiol (2) in DMF. Condensation of (3) with various alkyl, aralkyl,
and phenacyl halides gives the corresponding thioethers (4). The structures of newly prepared compounds
have been confirmed by analytical and spectral (IR, 1H NMR, MS) data.
O
O
O
R
S
SH
H
N
H
N
OH
N
N
DMF
N
N
DMF
Br
N
N
+
SH
HS
80–90°C
R
N
N
N
Br
S
S
NH2
O
O
O
4
2
3
1
Keywords: 2-bromo-3-hydroxynaphthalene-1,4-dione; 4-amino-4H-1,2,4-triazole-3,5-dithiol; bromo-
lawsone; thiadiazole-6,11-dione; lawsone; 1,4-naphthoquinone
1. Introduction
The naphthoquinone skeleton is found in many natural products and has been employed as a
synthetic intermediate for the preparation of numerous heterocyclic compounds with interesting
biological properties such as antitumor, antibacterial, antifungal, and anti-inflammatory agents
(1–3). Compounds containing the heterocyclic quinone group represent an important class of bio-
logically active molecules (4).The quinones occupy an important place among the different classes
of antitumor agents. The biological processes involved with the antitumoral activity of quinones
are DNA intercalation, bioreductive alkylation of biomolecules, and generation of oxy radicals
through redox cyclizing (5–8). The amino and thioether derivatives of 1,4-naphthoquinones have
extremely rich biological activities because of their redox potentials (9, 10). These derivatives
have been found to possess marked antiviral (11), molluscidal (12), antimalarial (13), antileish-
manial (14), antiproliferative (15), antibacterial, and antifungal activities (16–20).
*Corresponding author. Email: vrajesw@yahoo.com
ISSN 1741-5993 print/ISSN 1741-6000 online
© 2011 Taylor & Francis
DOI: 10.1080/17415993.2010.535209
http://www.informaworld.com

100 V. Srinivas and V.R. Rao
In view of various biological activities of quinones, the present work has been under taken.
In continuation of our earlier work (21, 22) on the synthesis of heterocyclic fused quinones
from naturally occurring quinones, we are now reporting the regioselective synthesis of the
novel 3-sulfanyl-5H-naphtho[2,3-e][1,3,4]triazino[3,4-b][1,3,4]thiadiazole-6,11-dione and its
derivatives.
2. Results and discussion
2-Bromo-3-hydroxynaphthalene-1,4-dione (1) has been prepared by the bromination of
2-hydroxy-1,4-naphthoquinone using NBS in CCl4 (23). The 4-amino-4H-1,2,4-triazole-3,5-
dithiol (2) was prepared by the condensation of thiocarbohydrazide with carbon disulfide in
pyridine (24). Reaction of 2-bromo-3-hydroxynaphthalene-1,4-dione (1) with 4-amino-4H-
1,2,4-triazole-3,5-dithiol (2) in DMF afforded the regioselective formation of 3-sulfanyl-5H-
naphtho[2,3-e][1,3,4]triazino[3,4-b][1,3,4]thiadiazole-6,11-dione (3) (Scheme 1).
O
SH
N
DMF
80–90°C
R
N
O
O
O
SH
N
H
N
N
OH
N
N
DMF
N
+
R–Br
R–Br
N
S
SH
HS
N
80–90°C
N
Br
S
O
NH2
O
DMF
80–90°C
3
2
1
O
DMF 80–90°C
SH
N
DMF
80–90°C
R–Br
N
S
N
N
O
O
R
S
H
O
H
N
OR
N
N
N
S
S
N
O
N
N
4
N
HS
4
a
R
ethyl
HB
H2
C
O
b
HA
O
S
HX
benzyl
c
d
e
f
g
h
i
p-NO2-benzyl
HN
phenacyl
N
N
p-CH3-phenacyl
p-CH3O-phenacyl
p-Cl-phenacyl
p-Br-phenacyl
N
HS
5
Scheme 1. 3-sulfanyl-5H-naphtho[2,3-e][1,3,4]triazino[3,4-b][1,3,4]thiadiazole-6,11-diones.
The initial nucleophilic attack of thiol (2) on 1 followed by an intramolecular ring closer favors
the formation of a six-membered ring (3). The cyclocondensation reaction between 1 and 2 leading
to the formation of 3 is highly regioselective.
Another possible structure to the product with o-quinonoid (5) can be proposed for the com-
pound prepared. However, this possibility is eliminated due to the fact that the C2 of the lawsone
(2-hydroxy-1,4-naphthoquinone) moiety is relatively more positively charged than the C4 car-
bonyl carbon. This favors the formation of structure 3 only. Further, the formation of 5 could be
ruled out by the fact that the product failed to condense with o-phenylenediamine in different

Journal of Sulfur Chemistry 101
conditions. Both compounds 3 and 4 on reduction with Zn dust in acetic acid gave a colorless
solution which on aerial oxidation regained the original color providing evidence for the presence
of 1,4-quinonoid structure.
Reaction of 3 with different alkyl, aralkyl, and phenacyl halides in a mixture of dry alcohol
and DMF under anhydrous conditions yielded the corresponding thioethers (4). The formation
4 is a regioselective S-alkylation. The alkylation of 3 with alkyl, aralkyl, and phenacyl halides
may result in the formation of different types of products such as O-alkylated, N-alkylated, and
S-alkylated and a mixture of all possible alkylated products. In the present investigation, a mixture
of products is not formed (as evidenced by TLC). The formation of S-alkylated products has been
explained in preference to the two other alkylated products as due to high nucleophilicity of thiol
group. The formation of these S-alkylated products was confirmed by spectral data.
Condensation of 3 with various alkyl, aralkyl, and phenacyl halides resulted in the formation of
=
− = −
thioethers (4). The IR spectrum of 3 displayed bands in the region 1528 (C C), 1594 ( C N ),
1638 ( C O), and 2931 cm−1 (SH weak). The 1H NMR (DMSO-d6) spectrum of 3 displayed a
− =
characteristic singlet at δ 13.7 assignable to the SH group, a signal at δ 8.3 for NH and complex
multiplet centered at δ 8.0 for the four aromatic protons. In the mass spectrum of 3, the molecular
ion was recorded at m/z 302.
3. Conclusion
In summary, we have developed a concise and efficient regioselective approach for the synthesis
of novel 3-sulfanyl-5H-naphtho[2,3-e][1,3,4]triazino[3,4-b][1,3,4]thiadiazole-6,11-dione and its
derivatives. Anticancer activity of these compounds is in progress.
4. Experimental
All the reagents and solvents were purchased from commercial sources and were used without
further purification unless otherwise stated. Melting points were determined in open capillaries
with a “cintex” melting point apparatus, Mumbai, India. All the melting points were uncorrected
and CHNS analysis was done by Carlo Erba EA 1108 automatic elemental analyzer. The purity
of the compounds was checked by TLC plates (E. Merek, Mumbai, India), and IR spectra (KBr)
were recorded on a BrukerWM-4(X) spectrometer (577model). 1H NMR spectra were recorded
on a Bruker WM-300 MHz spectrometer in δ (ppm) using TMS as the internal standard. The NH
protons were exchanged with D2O. Mass spectra (EI-MS) were determined on a Perkin Elmer
(SCIEX API-2000, ESI) at 12.5 eV.
4.1. General procedure
4.1.1. Synthesis of 3-sulfanyl-5H-naphtho[2,3-e][1,3,4]triazino[3,4-b][1,3,4]thiadiazole-
6,11-dione 3
A mixture of 2-bromo-3-hydroxynaphthalene-1,4-dione (2.53 g, 0.01 mol) and 4-amino-4H-
[1,2,4]triazole-3,5-dithiol (1.48 g, 0.01 mol) in DMF (20 ml) was stirred at 80–90 ◦C for 8 h. The
reaction mixture was cooled and poured over crushed ice. The solid thus, separated was filtered,
dried, and recrystallized from methanol.
4.1.1.1. 3-Sulfanyl-5H-naphtho[2,3-e][1,3,4]triazino[3,4-b][1,3,4]thiadiazole-6,11-dione (3).
Yield 92%, mp 200–202 ◦C. IR (KBr, υmax cm−1) 1528 (C C), 1594 ( C N ), 1638 ( C O)
=
− = −
− =

102 V. Srinivas and V.R. Rao
and 2931 (SH weak). 1H NMR (DMSO-d6, δ ppm): 13.4 (s, 1H, D2O exchangable SH), 8.30 (s,
1H, NH), 7.70–8.00 (m, 4H, Ar-H). 13C NMR (DMSO-d6, δ ppm): 126.0, 127.1, 129.8, 131.4,
132.4, 133.0, 135.0, 162.3; MS: m/z 303 (M + H)+. Anal. Calcd. for C12H6N4O2S2: Calcd: C,
47.67; H, 2.00; N, 18.53; S, 21.21%. Found: C, 47.71; H, 2.04; N, 18.57; S, 21.24%.
4.1.2. Reaction of 3 with alkyl, aralkyl and phenacyl halides 4
Compound 3 (0.01 mol) was dissolved in a mixture of dimethyl formamide (10 ml) and anhydrous
ethanol (10 ml) and appropriate alkyl, aralkyl, and phenacyl halides (0.01 mol) was added. The
reaction mixture was refluxed for 3–4 h at 80–90 ◦C, then cooled, the solid separated was filtered,
dried, and recrystallized from methanol to give the corresponding thioethers.
4.1.2.1. 3-Ethylsulfanyl-5H-naphtho[2,3-e][1,3,4]triazino[3,4-b][1,3,4]thiadiazole-
6,11-dione (4a). Yield 91%, mp 138–140 ◦C. IR (KBr, υmaxcm−1): 1540 (C C), 1590
=
1
− = −
− =
( C N ), 1626 ( C O), 3379 (NH). H NMR (DMSO-d6, δ ppm): 1.35 (t, 3H, CH3 of ethyl),
3.20 (q, 2H, CH2 of ethyl), 7.50–7.70 (m, 2H, Ar-H), 7.85–7.75 (m, 2H, Ar-H), 8.25 (s, 1H, NH).
Anal. Calcd. for C14H10N4O2S2: Calcd: C, 50.90; H, 3.05; N, 16.96; S, 19.41%. Found: C, 50.94;
H, 3.00; N, 16.91; S, 19.46%.
4.1.2.2. 3-Allylsulfanyl-5H-naphtho[2,3-e][1,3,4]triazino[3,4-b][1,3,4]thiadiazole-
6,11-dione (4b). Yield 88%, mp 198–200 ◦C. IR (KBr, υmax cm−1): 1540 (C C), 1593
=
1
− = −
− =
( C N ), 1629 ( C O), 3386 (NH). H NMR (DMSO-d6, δ ppm): 3.90 (d, J = 6.0 Hz,
2H, S-CH2), 5.11 (d, J = 7.5 Hz, HA of allyl group), 5.27 (d, J = 12 Hz, HB of allyl group),
5.90–6.00 (m, 1H, HX), 7.65–7.80 (m, 2H, Ar-H), 8.05–8.10 (m, 2H, Ar-H) 8.25 (s, 1H, NH).
Anal. Calcd. for C15H10N4O2S2: Calcd: C, 52.62; H, 2.94; N, 16.36; S, 18.73%. Found: C, 52.66;
H, 2.94; N, 16.31; S, 18.76%.
4.1.2.3. 3-Benzylsulfanyl-5H-naphtho[2,3-e][1,3,4]triazino[3,4-b][1,3,4]thiadiazole-
6,11-dione (4c). Yield 87%, mp 190–192 ◦C. IR (KBr, υmax cm−1): 1541 (C C), 1593 (C N),
=
=
1
− =
1627 ( C O), 3379 (NH). H NMR (CDCl3, δ ppm): 4.50 (s, 2H, S-CH2), 7.20–7.35 (m, 5H,
Ar-H), 7.70–7.80 (m, 2H, Ar-H), 8.05–8.15 (m, 2H, Ar-H), 8.40 (s, 1H, NH). Anal. Calcd. for
C19H12N4O2S2: Calcd: C, 58.15; H, 3.08; N, 14.28; S, 16.34%. Found: C, 58.00; H, 3.00; N,
14.23; S, 16.31%.
4.1.2.4. 3-p-Nitrobenzylsulfanyl-5H-naphtho[2,3-e][1,3,4]triazino[3,4-b][1,3,4]thiadiazole-
6,11-dione (4d). Yield 92%, mp 144–146 ◦C. IR (KBr, υmax cm−1) 1518 (C C), 1594 (C N),
=
=
1
− =
1626 ( C O), 3381 (NH). H NMR (CDCl3, δ ppm): 5.10 (s, 2H, S-CH2), 7.40–7.60 (m, 4H,
Ar-H), 8.10 (d, J = 8.2 Hz, 2H, H3 and H5 of p-nitrophenyl), 8.20 (d, J = 8.2 Hz, 2H, H2 and H6
of p-nitrophenyl), 8.40 (s, 1H, NH). Anal. Calcd. for C19H11N5O4S2: Calcd: C, 52.17; H, 2.53;
N, 16.01; S, 14.66%. Found: C, 52.19; H, 2.56; N, 16.10; S, 14.69%.
4.1.2.5. 3-(2-Oxo-2-phenyl-ethylsulfanyl)-5H-naphtho[2,3-e][1,3,4]triazino[3,4-b][1,3,4]
thiadiazole-6,11-dione (4e). Yield 95%, mp 140–142 ◦C. IR (KBr, υmax cm−1): 1535 (C C),
=
1
=
− =
1595 (C N), 1679 ( C O), 3367 (NH). H NMR (CDCl3, δ ppm): 5.05 (s, 2H, S-CH2), 7.30–
7.40 (m, 5H, Ar-H), 7.80 (m, 2H, Ar-H), 8.10 (m, 2H, Ar-H), 8.40 (s, 1H, NH). Anal. Calcd. for
C20H12N4O3S2: Calcd: C, 57.13; H, 2.88; N, 13.32; S, 15.25%. Found: C, 57.15; H, 2.84; N,
13.35; S, 15.28%.

Journal of Sulfur Chemistry 103
4.1.2.6. 3-(2-Oxo-2-p-tolyl-ethylsulfanyl)-5H-naphtho[2,3-e][1,3,4]triazino[3,4-b][1,3,4]
thiadiazole-6,11-dione (4f). Yield 92%, mp 166–168 ◦C. IR (KBr, υmax cm−1): 1514 (C C),
=
1
=
=
1601 (C N), 1676 (–C O), 3379 (NH). H NMR (CDCl3, δ ppm): 2.50 (s, 3H, Ph-CH3), 4.60 (s,
2H, S-CH2), 7.60–7.80 (m, 4H, Ar-H), 8.10 (d, J = 8.2 Hz, 2H, H3 and H5 of tolyl ring) and 8.20
(d, J = 8.2 Hz, 2H, H2 and H6 of tolyl ring), 8.30 (s, 1H, NH). Anal. Calcd. for C21H14N4O3S2:
Calcd: C, 58.05; H, 3.25; N, 12.89; S, 14.76%. Found: C, 58.00; H, 3.28; N, 12.92; S, 14.29%.
4.1.2.7. 3-[2-(4-Methoxy-phenyl)-2-oxo-ethylsulfanyl]-5H-naphtho[2,3-e][1,3,4]triazino
[3,4-b][1,3,4]thiadiazole-6,11-dione (4g). Yield 88%, mp 178–180 ◦C. IR (KBr, υmax cm−1):
1
=
=
− =
1572 (C C), 1595 (C N), 1669 ( C O), 3406 (NH). H NMR (CDCl3, δ ppm): 3.80 (s, 3H,
O-CH3), 5.00 (s, 2H, S-CH2), 7.81–7.89 (m, 4H, Ar-H), 8.10 (d, J = 8.2 Hz, 2H, H3 and H5 of
p-methoxy phenyl), 8.50 (d, J = 8.2 Hz, 2H, H2 and H6 of p-methoxy phenyl), 8.40 (s, 1H, NH).
Anal. Calcd. for C21H14N4O4S2: Calcd: C, 55.99; H, 3.13; N, 12.44; S, 14.24%. Found: C, 55.96;
H, 3.15; N, 12.48; S, 14.28%.
4.1.2.8. 3-[2-(4-Chloro-phenyl)-2-oxo-ethylsulfanyl]-5H-naphtho[2,3-e][1,3,4]triazino
[3,4-b][1,3,4]thiadiazole-6,11-dione (4h). Yield 87%, mp 172–174 ◦C. IR (KBr, υmax cm−1
)
1
=
=
− =
1529 (C C), 1587 (C N), 1648 ( C O), 3088 (NH). H NMR (DMSO-d6, δ ppm): 5.10 (s,
2H, S-CH2), 7.60–7.70 (m, 4H, Ar-H), 7.80 (d, J = 8 Hz, 2H, H3 and H5 of p-chlorophenacyl),
7.9 (d, J = 8 Hz, 2H, H2 and H6 of p-chlorophenacyl), 8.50 (s, 1H, NH). Anal. Calcd. for
C20H11ClN4O3S2: Calcd: C, 52.80; H, 2.44; N, 12.32; S, 14.10%. Found: C, 52.84; H, 2.48;
N, 12.34; S, 14.14%.
4.1.2.9. 3-[2-(4-Bromo-phenyl)-2-oxo-ethylsulfanyl]-5H-naphtho[2,3-e][1,3,4]triazino
[3,4-b][1,3,4]thiadiazole-6,11-dione (4i). Yield 90%, mp 118–120 ◦C. IR (KBr, υmax cm−1):
1
=
=
=
1544 (C C), 1583, (C N), 1679 (C O) 3082 (NH). H NMR (CDCl3, δ ppm): 5.00 (s, 2H,
S-CH2), 7.60–7.70 (m, 4H, Ar-H), 7.80 (d, J = 8 Hz, 2H, H3 and H5 of p-bromophenacyl),
7.90 (d, J = 8 Hz, 2H, H2 and H6 of p-bromophenacyl), 8.50 (s, 1H, NH). Anal. Calcd. for
C20H11BrN4O3S2: Calcd: C, 48.10; H, 2.22; N, 11.22; S, 12.84%. Found: C, 48.14; H, 2.24; N,
11.25; S, 12.88%.
Acknowledgements
We thank the University Grants Commission New Delhi (F. No. 32-201/2006 (SR)) for financial support.
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