Synthesis and photocyclization of 1,2,4-triazole-3-thiones

Article abstract of DOI:10.1055/s-2006-950301

Irradiation of thienyl and other substituted triazolothiones in a thin film reactor at 254 nm in an acetonitrile-dilute sodium hydroxide medium, furnished the respective triazolobenzothiazoles and, in some cases, the desulfurized product. The irradiation of anilinomethyl-, and aryloxymethyltriazolothiones under the above conditions also furnished the respective cyclized products and desulfurized compounds. Irradiation of benzyl substituted triazole thiones in the presence of triethylamine in benzene furnished the corresponding triazolothiazine and triazolodibenzazepine. Reaction of glycine hydrazide with aryl isothiocyanates furnished the triazolothiones, wherein glycine hydrazide functioned as a hydrazine-transferring agent. Irradiation of o-chlorophenyl substituted thione in basic acetonitrile medium furnished triazolodibenzdiazepine, whereas, the benzyl derivative furnished the triazolobenzothiazine. Georg Thieme Verlag Stuttgart.

Full text of DOI:10.1055/s-2006-950301

PAPER
3841
Synthesis and Photocyclization of 1,2,4-Triazole-3-thiones
a
a
a
b
Synthesis and
uP hotocycliza
n
tion of 1,2,4
d
a
hiones rarajan Aruna, Annamalai Senthilvelan, Dhakshanamurthy Thirumalai, Sengodagounder Muthusamy,
a
Vayalakkavoor T. Ramakrishnan*
a
Department of Organic Chemistry, School of Chemical Sciences, University of Madras, Guindy Campus, Chennai 600025, India
Fax +91(44)22352494; E-mail: vtrk28@yahoo.com
b
Department of Chemistry, Bharathidasan University, Thiruchirappalli 620024, India
Received 20 June 2006; revised 13 July 2006
tion of 4-(2-halobenzyl)-1,2,4-triazole-5-thiones to ben-
zothiazine (C) in a MLR in an alkaline medium (sodium
hydroxide in acetonitrile) required a shorter reaction time.
In the later case, we also observed photodesulfurized
Abstract: Irradiation of thienyl and other substituted triazo-
lothiones in a thin film reactor at 254 nm in an acetonitrile-dilute so-
dium
hydroxide
medium,
furnished
the
respective
triazolobenzothiazoles and, in some cases, the desulfurized product.
The irradiation of anilinomethyl-, and aryloxymethyltriazo- products (D) along with the anticipated photocyclized
4
lothiones under the above conditions also furnished the respective products (Scheme 2).
cyclized products and desulfurized compounds. Irradiation of ben-
zyl substituted triazole thiones in the presence of triethylamine in
R
R
benzene furnished the corresponding triazolothiazine and triazolod-
ibenzazepine. Reaction of glycine hydrazide with aryl isothiocyan-
ates furnished the triazolothiones, wherein glycine hydrazide
functioned as a hydrazine-transferring agent. Irradiation of o-chlo-
rophenyl substituted thione in basic acetonitrile medium furnished
triazolodibenzdiazepine, whereas, the benzyl derivative furnished
the triazolobenzothiazine.
R
MLR
hν (254 nm)
N
NH
N
2
5 °C
N
N
N
MeCN–H2O
NaOH
N
S
N
X
X
1
1–62 h
N
S
C
D
Key words: photocyclization, photodesulfurization, triazoles, hy-
drazides, azepine
Scheme 2 Photochemical synthesis of triazolobenzothiazines C
Based on the above findings, in this paper, we wish to
report the photocyclization of triazole-3-thiones to
triazolobenzothiazoles, triazolobenzothiazines, triazolo-
benzazepines and triazolodibenzdiazepine, under basic
conditions.
The photochemical synthesis of heterocyclic systems has
become a versatile method, in respect to its applicability
to many ring systems. We have previously explored the
1
photochemical synthesis of benzothiazoles (A), and ben-
2
zothiazoloquinazolinones (B) from suitably substituted
The required triazolothiones 1a–d and 4a–c were pre-
pared from the respective o-chloroaryl isothiocyanates
and hydrazides using 10% K CO solution under reflux
thioacyl derivatives (Scheme 1).
MLR
2
3
hν (254 nm)
(Schemes 3 and 4).
NHCSR
N
2
5 °C
R
A solution of the thione 1a in acetonitrile containing di-
lute sodium hydroxide was flushed with nitrogen and irra-
diated at 254 nm in a thin film reactor (TFR) for 2.5 hours,
which furnished the benzothiazole 2a. Likewise, the
MeOH
6–45 h
S
Cl
1
A
MLR
hν (300 nm)
25 °C
O
O
N
N
NCS
R
N
S
MeOH
12–45 h
N
S
Cl
NH
N
H
Cl
O
C
S
H
10% K2CO3
reflux
6
N
B
+
R
N
NH2
–8 h R1
Cl
R1
Scheme 1 Photochemical synthesis of benzothiazoles A and benzo-
thiazoloquinazolinones B
5
3–83%
1a–d
MeCN–H2O hν (254 nm)
2
M NaOH 2–2.5 h
N
Following extensive research on the photochemistry of
thiones, we found that the photochemical cyclization of 4-
R
R
N
N
N
N
N
(2-halophenyl)-1,2,4-triazole-5-thiones to their corre-
+
sponding benzothiazoles in a multilamp reactor (MLR)
R1
R1
S
Cl
3
proceeded slowly (30–60 h), whereas the photocycliza-
2
a–d
3
(from 1d)
5%
2
1–56%
2
SYNTHESIS 2006, No. 22, pp 3841–3848
x
x
.x
x
.
2
0
0
6
Advanced online publication: 09.10.2006
DOI: 10.1055/s-2006-950301; Art ID: Z12306SS
Georg Thieme Verlag Stuttgart · New York
Scheme 3 Synthesis of triazolethiones 1a–d and triazolobenzo-
thiazoles 2a–d
©

3842
S. Aruna et al.
PAPER
Table 1 Synthesis of Triazolethiones 1a–d, 4a–c and Their Photoproducts 2a–d, 3, 5a–c and 6
Triazole thiones
R
R1
H
Irradiation time (h) Photoproducts
Yield (%)
1
1
1
1
a
b
c
2-Thienyl
2-Thienyl
Bn
2.5
2.0
2.5
2.0
2a
2b
2c
48
43
56
Cl
Cl
H
d
1-Naphthylmethyl
2d
3
21
25
4
a
H
H
2.0
2.5
2.0
5a
42
(Y = NMe)
4
b
4-Me
2-Me
H
5b
38
(Y = O)
4
c
6-Me
5c
6
32
18
(Y = O)
thiones 1b and 1c, on irradiation, furnished the benzothi-
azoles 2b and 2c, respectively (Table 1). The thione 1d
furnished the desulfurized product 3, in addition to the
benzothiazole 2d, on irradiation under alkaline conditions
Y
NCS
N
NH
Y
Cl 10% K2CO3
CH2
C
NHNH2
R
N
reflux
6–7 h
O
R1
S
R
(
Scheme 3). Triazolobenzothiazole formation through a
Cl
7
8–83%
R1
singlet state involves a photosubstitution of the anionic
thio-carbonyl sulphur of triazolethione which intramolec-
4 a–c
MeCN–H2O hν (254 nm)
ularly displaces the halogen of the haloarene in an
2–2.5 h
2
M NaOH
5
S (ET)Ar* mechanism. A similar mechanism for the for-
N
Y
Y
1
mation of triazolobenzothiazine through a singlet state
and desulfurization through a triplet state has been pro-
posed earlier. Since compound 1d gave the desulfurized
3
N
2
N
1
R
9
N
8
5
N
2
R
4
7
N
N3
6
5
6
R1
S
product, along with the cyclization product, a triplet state
4
Cl
R1
of 1d would also have been involved due to the presence
7
6 (from 4c)
5a–c
32–42%
of the naphthyl ring (heavy atom effect). The irradiation
1
8%
of thiones 4a and 4b, under the basic conditions described
above using a TFR, furnished the respective triazoloben- Scheme 4 Synthesis of triazolethiones 4a–c and triazolobenzo-
zothiazoles 5a and 5b. The thione 4c, on irradiation under thiazoles 5a–c
the same conditions, furnished the thiazole 5c and the des-
ulfurized product 6 (Scheme 4) (Table 1).
nal for compounds 5a, and 5b at d = 4.5 and 5.5 ppm, and
The IR spectra of the thiones showed absorption bands in
geminal coupled signals for compounds 5c and 6 around
–
1
the region 1300–1380 cm , characteristic of the C=S
group. However, the proton NMR spectrum of thiones
13
d = 4.7, and 4.9–5.2 ppm, respectively. The C NMR shift
for the N–CH carbon for compounds 4a and 5a appeared
2
1a–d and 4a,4b in chloroform showed a sharp signal be-
at d = 48.7 and 30.6 ppm, respectively. The O–CH carbon
2
tween d = 11–13 ppm, characteristic of an SH proton. The
for the compounds 4b, 4c, 5b, 5c and 6 appeared at d =
13
C NMR spectra of these compounds showed a signal
6
0.5, 60.9, 48.8, 61.9 and 60.3 ppm, respectively.
around d = 169 ppm, which could be due to a HS–C=N
carbon, rather than a thio carbonyl (C=S) carbon, indicat-
ing that these thiones exist in an enol form in the solution.
Irradiation of thione 7a in the presence of triethylamine,
using benzene as a solvent in an MLR at 254 nm for 80
hours, furnished triazolobenzothiazine 8a (11%) and tri-
azolodibenzazepine 9a (4%). Likewise, irradiation of 7b
for six hours, under the same conditions, furnished the thi-
azine 8b (15%) and azepine 9b (5%) (Scheme 5). No de-
sulfurized product was formed under these conditions.
1
3
For comparison, the C NMR spectroscopic shifts for the
C=S carbon of thiourea and N,N¢-dimethylthiourea have
been reported as d = 179.7 and 182.7 ppm, respectively.
8
The methylene protons of the thiones 1c and 1d exhibited
geminal coupled signals at d = 3.6–4.3 and 4.12–4.45 ppm
respectively, however, the products 2c, 2d and 3 showed
only singlets for the methylene protons at d = 4.62, 5.05,
and 4.45 ppm, respectively. Similarly, the methylene pro-
tons of the thiones 4a–c showed geminal coupled signals
The triazolo benzothiazines 8a and 8b thus prepared were
identical to those obtained under the basic acetonitrile
6
conditions reported previously (melting point compari-
son and superimposable IR).
at d = 4.2–4.4, 4.77–5.01, and 4.67–4.99 ppm, respective- The formation of the thiazine 8 from the thione 7 can be
ly, whereas, the methylene protons induced a singlet sig- rationalized, by an electron transfer mechanism from
Synthesis 2006, No. 22, 3841–3848 © Thieme Stuttgart · New York

PAPER
Synthesis and Photocyclization of 1,2,4-Triazole-3-thiones
3843
R
R
anate, furnished the thiones 10b and 10c in 68% and 83%
yields respectively. The thiones 10a–c were also prepared
from the respective isothiocyanate and hydrazine hydrate
by refluxing in 10% K CO for six hours.
R
N
NH
N
NH
hν, MLR
45 nm, N2
N
N
S
2
3
N
N
2
N
Thus, the glycine hydrazide could be seen as a hydrazine-
transferring agent. The evolution of hydrogen sulfide was
identified by testing with a filter paper, which had been
dipped in lead acetate solution. The mechanism for the
formation of thione 10a–c could be rationalized as depict-
ed in Scheme 7.
S
benzene, Et3N
S
Cl
62–80 h
8
1
a,b
1, 15%
9a,b
7
a,b
4,5%
a R = H
b R = Me
Scheme 5 Photochemical synthesis of triazolobenzothiazines 8a,b
and triazolo dibenzazepines 9a,b
Irradiation of the thione 10a in basic acetonitrile solution
in a thin film reactor, at 254 nm, for two hours, furnished
1
,2,4-triazolo[4,3-a]-13H-(4,5)(6,7)-dibenz[1,3]diaz-
9
triethylamine to the thione, followed by electron transfer
epine-3(2H)-thione 11 (43%) (Scheme 8).
6
to the aryl ring and further steps as proposed earlier. The
formation of the azepine 9 could be explained through
electron transfer from the triethylamine to the 3-aryl ring
of the thione 7 which then attacks the halobenzyl ring to
yield the triazolodibenzazepine.
11
Cl
12
TFR
hν, N2, 2 h
10
13
NH
9
NH
N
1
N
Cl
N
NH
2
M NaOH
MeCN–H2O
8
7
N
NH
2
4 3
5
As an extension of the above studies, glycine hydrazide
was treated with o-chlorophenyl isothiocyanate in 10%
K CO under reflux for 9 hours, furnishing 4-(2-chlo-
S
43%
6
S
1
0a
11
2
3
rophenyl)-5-(2-chlorophenylamino)-1,2,4-triazole-3-thio-
Scheme 8 Photochemical synthesis of triazolodibenzdiazepine 11
ne 10a in 80% yield (Scheme 6). The structure of thione
1
13
1
0a was established by IR, H NMR, C NMR, and mass
The IR spectrum of the compound 11 absorbed at 3313
spectral data. Likewise, the reaction of glycine hydrazide
with 2-chlorobenzyl isothiocyanate and phenyl isothiocy-
–1
–1
and 3186 cm , due to the NH groups, and at 1546 cm ,
1
due to the presence of the C=N group. The H NMR spec-
trum of compound 11 exhibited four aromatic doublets
R
(
d = 7.67, 7.81, 7.85 and 8.16 ppm) possibly due to H5,
HN
1
0% K2CO3
N
NH
H8, H9, H12 and a multiplet at d = 7.31–7.58 ppm for the
NH2CH2CONHNH2
+
R-NCS
N
13
reflux
other aromatic protons. The C NMR and mass spectral
R
6
h
S
0a–c
analysis of compound 11 also supported the structure
shown.
6
8–80%
CH2
Cl
1
Since amines are known to initiate electron transfer reac-
10a: R =
10b: R =
10c: R =
9
tions under photochemical conditions, it is probable that
Cl
the electron transfer occurs from the amino group (NH) in
the side chain of the thione 10a, to the attached aromatic
Scheme 6 Syntesis of triazolethiones 10a–c
CH2NH2
O
NH
NH
H
N
Ar-NCS
+
NH2CH2CONHNH2
Ar
S
Ar-NCS
Ar
Ar-NCS
CH2NH2
O
C
S
C
2
CH NH2
ArHN
N
OC
NH
NH
C
ArHN
NH
S
N
C
S
NH
H2
H2N C
Ar
C
O
S
OH
–
H2O
S
S
OH
2
–H O
CH2NH2
CH2NH2
ArHN
C
N
O
N
S
O
N
NH
H
N
ArHN
N
NH
Ar
Ar
Ar
N
NH
S
N
Ar
S
10a
S
Scheme 7 Mechanism for the formation of triazolethiones 10a–c
Synthesis 2006, No. 22, 3841–3848 © Thieme Stuttgart · New York

3844
S. Aruna et al.
PAPER
ring which, in turn, attacks the second aryl ring, leading to with cold dil. HCl and the separated solid was filtered and washed
with H O to furnish the corresponding triazole-3-thione 1a, which
was recrystallized from EtOAc.
cyclization, followed by elimination of the chloride anion.
Photochemical reduction of the second halogen, during
2
1
0
base-mediated irradiation would lead to the product 11.
Thus, the present report describes a facile method for the
synthesis of a condensed diazepine ring system. Though
there are many methods for the preparation of 1,4-
4-(2-Chlorophenyl)-5-(thien-2-yl)-1,2,4-triazole-3-thione (1a)
Yield: 1.09 g (53%); mp 72–74 °C.
–
1
IR (KBr): 3082, 2908, 1577, 1350 cm .
1
1
1
12
H NMR (CDCl , 400 MHz): d = 6.82–7.78 (m, 7 H, ArH), 11.68
3
diazepines and 1,2-diazepines, only a few methods are
available for the synthesis of 1,3-diazepines.1
3–16
(s, 1 H, SH).
1
3
C NMR (CDCl , 100 MHz): d = 127.5, 127.9, 128.4, 128.6, 130.9,
3
Irradiation of the thione 10b in basic acetonitrile furnished
the triazolobenzothiazine 12 (50%) (Scheme 9), the for-
1
31.2, 131.9, 132.3, 147.2, 169.1.
+
MS (EI, 70 eV): m/z (%) = 293 (8) [M] , 258 (35), 149 (100), 111
6
mation of which can be explained, as reported earlier. Ir-
(
30), 109 (37), 105 (9), 83 (12).
radiation of triazolothione 10c (containing no o-halogen)
in chloroform, in the presence of iodine, in an MLR for 20
hours resulted only in the recovery of the starting material,
instead of the expected oxidative cyclized dibenzodi-
azepine 11.
Anal. Calcd for C H N S Cl: C, 49.05; H, 2.74; N, 14.30. Found:
1
2
8
3 2
C, 48.74; H, 2.72; N, 14.14.
4-(2,4-Dichlorophenyl)-5-(thien-2-yl)-1,2,4-triazole-3-thione
(1b)
Treatment of thiophene-2-carboxylic acid hydrazide (1.0 g, 7
mmol) with 2,4-dichlorophenyl isothiocyanate (1.43 g, 7 mmol) in
aq K CO (10%, 100 mL) under reflux for 6 h, gave the thione 1b.
Cl
Cl
2
3
Yield: 1.65 g (72%); mp 195–196 °C.
TFR
hν, N2, 2 h
–
1
HN
HN
IR (KBr): 3073, 2900, 2094, 1581, 1380 cm .
N
N
NH
1
H NMR (CDCl , 400 MHz): d = 7.01–7.93 (m, 6 H, ArH), 11.22
N
NH
N
3
2
M NaOH
MeCN–H2O
(
s, 1 H, SH).
S
Cl
S
1
3
C NMR (CDCl , 100 MHz): d = 126.6, 127.7, 128.1, 128.8, 130.7,
50%
3
1
32.1, 134.1, 137.2, 146.0, 169.1.
+
1
0b
12
MS (EI, 70 eV): m/z (%) = 327 (21) [M] , 329 (21) [M + 2], 294
41), 292 (76), 183 (100), 109 (81).
(
Scheme 9 Photochemical synthesis of triazolobenzothiazine 12
Anal. Calcd for C H N S Cl : C, 43.90; H, 2.15; N, 12.80. Found:
1
2
7
3
2
2
C, 43.66; H, 2.15; N, 12.93.
In conclusion, we have synthesized a range of substituted
triazolethiones and studied their photochemistry in a base- 5-Benzyl-4-(2,4-dichlorophenyl)-1,2,4-triazole-3-thione (1c)
A mixture of phenylacetic acid hydrazide (1 g, 6 mmol) and 2,4-
dichlorophenyl isothiocyanate (1.35 g, 6 mmol) under reflux for 5
mediated solvent system. Photocyclization and photode-
sulfurization are two competing processes through which
the photoproducts were formed. During the course of this
work, we also identified glycine hydrazide as a novel hy-
drazine-transferring agent.
h, in aq K CO (10%, 100 mL) furnished the thione 1c.
2
3
Yield: 1.86 g (83%); mp 168–170 °C.
–
1
IR (KBr): 3062, 2758, 1300 cm .
1
H NMR (CDCl , 400 MHz): d = 3.66–4.27 (2 × d, J = 15.6 Hz,
3
2
H, CH ), 6.98–7.35 (m, 7 H, ArH), 7.56 (d, J = 2.4 Hz, 1 H, 3¢-
2
UV spectra were recorded with a Shimadzu 1601 spectrophotome-
ter. IR spectra were recorded on a FTIR-8300 Shimadzu spectro-
CH), 12.20 (s, 1 H, SH).
1
13
13
photometer. H and C NMR spectra were recorded on Bruker
DPX 200 (200 MHz) and Jeol GSX 400 (400 MHz) instruments
with TMS as internal standard (chemical shift in d ppm). The mass
spectra were recorded on Jeol JMS-DX 3030 HF and GCMS QP
C NMR (CDCl , 100 MHz): d = 32.4 (CH ), 127.6, 128.3, 128.7,
3
2
128.7, 129.5, 130.6, 131.5, 133.1, 133.8, 137.2, 151.6, 169.0.
+
MS (EI, 70 eV): m/z (%) = 335 (14) [M] , 337 (10) [M + 2], 300
(
(
100), 302 (38), 183 (63), 185 (24), 148 (8), 117 (5), 116 (8), 91
48), 65 (21).
5000 Shimadzu instruments. Chromatographic separations were
performed using silica gel (ACME samples). Thin layer chromatog-
raphy (TLC) was performed using glass plates coated with silica gel
Anal. Calcd for C H N SCl : C, 53.58; H, 3.29; N, 12.49. Found:
15 11
3
2
C, 53.26; H, 3.03; N, 12.49.
(ACME samples) of 0.25 mm thickness. Spots were visualized us-
ing iodine vapour. The photochemical reactions were carried out in
quartz vessels of different capacity in an Applied Photophysics mul-
tilamp reactor (254 nm, 365 nm, 12 lamps) and an Applied Photo-
physics thin-film reactor (254 nm). The petrol ether (PE) used had
a boiling range of 68–80 °C.
4
-(2-Chlorophenyl)-5-(1-naphthylmethyl)-1,2,4-triazole-3-
thione (1d)
Treatment of 1-naphthylacethydrazide (1.0 g, 5 mmol) with 2-chlo-
rophenyl isothiocyanate (0.85 g, 5 mmol) in aq K CO (10%, 100
mL) under reflux for 6 h, gave the thione 1d.
2
3
Synthesis of Substituted 1,2,4-Triazole-3-thiones 1a–d; Typical
Procedure
Yield: 1.08 g (62%); mp 226–227 °C.
–
1
IR (KBr): 3012, 2931, 1330 cm .
A mixture of thiophene-2-carboxylic acid hydrazide (1 g, 7 mmol)
and 2-chlorophenyl isothiocyanate (1.19 g, 7 mmol) was refluxed in
K CO solution (10%, 100 mL) for 6–8 h, cooled, filtered and the
1
H NMR (CDCl , 400 MHz): d = 4.12–4.45 (2 × d, J = 16.1 Hz,
3
2 H, CH ), 7.20–8.11 (m, 11 H, ArH), 11.36 (s, 1 H, SH).
2
3
2
filtrate was washed with Et O. The aqueous layer was neutralized
2
Synthesis 2006, No. 22, 3841–3848 © Thieme Stuttgart · New York

PAPER
Synthesis and Photocyclization of 1,2,4-Triazole-3-thiones
3845
1
3
1
C NMR (CDCl , 100 MHz): d = 30.2 (CH ), 123.3, 125.0, 125.7,
H NMR (CDCl , 400 MHz): d = 4.62 (s, 2 H, CH ), 7.22–7.34 (m,
3
2
3
2
1
26.0 127.6, 127.8, 128.1, 129.3, 130.3, 130.6, 131.3, 131.5, 132.6,
7 H, ArH), 7.62 (d, J = 1.0 Hz, 1 H).
1
33.5, 150.6, 168.6.
13
C NMR (CDCl , 100 MHz): d = 32.3, 114.7, 124.3, 126.9, 127.5,
3
+
MS (EI, 70 eV): m/z (%) = 351 (29) [M] , 316 (89), 225 (14), 190
128.0, 129.2, 131.8, 133.9, 134.3, 155.8.
(46), 166 (26), 149 (100), 141 (37), 115 (28), 111(24), 85 (19).
+
MS (EI, 70 eV): m/z (%) = 299 (100) [M] , 301 (30) [M + 2], 182
Anal. Calcd for C H N SCl: C, 64.86; H, 4.01; N, 11.94. Found:
C, 65.23; H, 3.97; N, 12.01.
(42), 184 (18), 147 (12), 146 (42), 120 (15), 117 (11), 115 (20), 91
(37), 90 (16).
1
9
14
3
Anal. Calcd for C H N SCl: C, 60.10; H, 3.36; N, 14.02. Found:
C, 60.12; H, 3.23; N, 14.16.
1
5
10
3
Photochemical Synthesis of 1,2,4-Triazolo[3,4-b]benzothiazoles
2a–d and Desulfurized Triazoles 3; Typical Procedure
A solution of triazole-3-thione 1a (0.3 g, 1 mmol) in MeCN (150
mL), containing aqueous NaOH (2 M, 30 mL) was flushed with ni-
trogen for 1 h and irradiated in a TFR (equipped with one lamp) at
Irradiation of 1d
An MeCN (150 mL) solution of 4-(2-chlorophenyl)-5-(1-naphthyl-
methyl)-1,2,4-triazole-3-thione 1d (0.35 g, 1 mmol) containing
NaOH (2 M, 30 mL), was flushed with nitrogen, and irradiated in a
TFR for 2 h. After the usual work-up as mentioned above, chro-
matographic separation afforded the triazolo benzothiazole 2d (PE–
EtOAc, 1:1) and triazole 3 (PE–EtOAc, 2:3).
254 nm for 2.5 h. In the reactor, the solution to be irradiated was
pumped, using a peristaltic pump, from a three-necked flask
through a jet, which allowed a thin film of the solution to fall over
a quartz tube surrounding the lamp. After the reaction was complete
(monitored by TLC), the acetonitrile was removed under reduced
pressure from the two-phase mixture and the aqueous layer was ex-
tracted with EtOAc (3 × 25 mL). The organic layer was separated
and the aqueous layer was neutralized with dil. HCl and extracted
with EtOAc (2 × 20 mL). The organic layers were combined, evap-
orated and the residue was purified by chromatography (silica gel;
EtOAc–PE, 1:1) to furnish 2a.
1
-(1-Naphthylmethyl)-1,2,4-triazolo[3,4-b]benzothiazole (2d)
Yield: 0.066 g (21%); mp 152–154 °C.
–
1
IR (KBr): 3015, 2985, 1488, 1450 cm .
1
H NMR (CDCl , 400 MHz): d = 5.05 (s, 2 H, CH ), 6.91–8.12 (m,
3
2
1
1 H, ArH).
1
3
C NMR (CDCl , 100 MHz): d = 29.2, 123.7, 125.0, 125.6, 126.0,
3
1-(Thien-2-yl)-1,2,4-triazolo[3,4-b]benzothiazole 2a
1
26.9, 127.5, 128.3, 129.5, 130.1, 130.4, 131.1, 131.3, 131.5, 133.0,
Yield: 0.13 g (48%); mp 152–154 °C.
1
44.7, 152.5.
–
1
IR (KBr): 3124, 2923, 1515, 1326 cm .
+
MS (EI, 70 eV): m/z (%) = 315 (16) [M] , 317 (6) [M + 2], 271 (10),
269 (11), 255 (8), 166 (100), 148 (9), 139 (61), 122 (30), 115 (42),
96 (31).
1
H NMR (CDCl , 400 MHz): d = 7.1–7.8 (m, 7 H, ArH).
3
13
C NMR (CDCl , 100 MHz): d = 114.3, 124.9, 126.5, 126.6, 126.8,
3
1
27.8, 129.4, 130.0, 132.5, 143.7, 156.5.
Anal. Calcd for C H N S: C, 72.36; H, 4.15; N, 13.32. Found: C,
1
9
13
3
+
72.09; H, 4.28; N, 13.11.
MS (EI, 70 eV): m/z (%) = 257 (48) [M] , 258 (13) [M + 1], 148
(
(
100), 122 (45), 109 (49), 108 (18), 104 (23), 96 (61), 82 (23), 81
14), 76 (20).
4
-(2-Chlorophenyl)-3-(1-naphthylmethyl)-1,2,4-triazole (3)
Yield: 0.079 g (25%); mp 160–162 °C.
Anal. Calcd for C H N S : C, 56.01; H, 2.74; N, 16.33. Found: C,
5
1
2
7
3 2
–1
IR (KBr): 3105, 3055, 1514 (C=N) cm .
5.36; H. 2.93; N, 16.42.
1
H NMR (CDCl , 400 MHz): d = 4.45 (s, 2 H, CH ), 6.85–8.02 (m,
3
2
6
-Chloro-1-(thien-2-yl)-1,2,4-triazolo[3,4-b]benzothiazole (2b)
1
1 H, ArH), 8.63 (s, 1 H, C5-H).
A MeCN (150 mL) solution of 1b (0.33 g, 1 mmol) containing
NaOH (2 M, 30 mL) was flushed with nitrogen and irradiated in a
TFR for 2 h. Usual work-up as mentioned above and chromato-
graphic separation afforded the triazolobenzothiazole 2b.
1
3
C NMR (CDCl , 100 MHz): d = 29.5, 123.6, 124.9, 125.8, 126.5,
3
1
1
27.3, 127.7, 128.0, 128.5, 128.9, 130.4, 131.3, 131.4, 131.6, 131.9,
33.7.
+
MS (EI, 70 eV): m/z (%) = 319 (70) [M] , 320 (18) [M + 1], 321
(
1
Yield: 0.126 g (43%); mp 162–164 °C.
26) [M + 2], 318 (100), 284 (33), 194 (31), 167 (28), 166 (45),
41(27), 140 (32), 139 (36), 127 (29), 115 (39), 111 (28).
–
1
IR (KBr): 3125, 2925, 1343, 1200 cm .
1
H NMR (CDCl , 400 MHz): d = 7.28–7.67 (m, 5 H, ArH), 7.71 (d,
3
Anal. Calcd for C H N Cl: C, 71.36; H, 4.41; N, 13.13. Found: C,
19 14 3
7
J = 1.5 Hz, 1 H).
1.25; H, 4.55; N, 13.23.
1
3
C NMR (CDCl , 100 MHz): d = 115.0, 124.6, 127.0, 127.9, 128.5,
3
Synthesis of Substituted 1,2,4-Triazole-3-thiones 4a–c; Typical
Procedure
A mixture of 2-chlorophenyl isothiocyanate (1.18 g, 7 mmol) and 2-
1
29.8, 130.3, 132.4, 134.1.
+
MS (EI, 70 eV): m/z (%) = 291 (74) [M] , 293 (29) [M + 2], 292
(14) [M + 1], 182 (100), 156 (7), 124 (6), 110 (3), 109 (13), 104 (8),
(
N-methyl-N-phenylamino)acethydrazide (1.26 g, 7 mmol) was re-
93 (6).
fluxed in aq K CO (10%, 100 mL) for 6 h, cooled, filtered and the
2
3
Anal. Calcd for C H N S Cl: C, 49.39; H, 2.07; N, 14.40. Found:
filtrate washed with Et O. The aqueous layer was acidified with
1
2
6
3
2
2
C, 48.98; H, 2.12; N, 14.22.
cold, dil. HCl and the separated solid was filtered and washed with
H O to furnish thione 4a.
2
1-Benzyl-6-chloro-1,2,4-triazolo[3,4-b]benzothiazole (2c)
A MeCN (150 mL) solution containing NaOH (2 M, 30 mL) and
thione 1c (0.34 g, 1.1 mol) was flushed with nitrogen and then irra-
diated in a TFR for 2.5 h. Usual work-up as mentioned above and
chromatographic separation afforded triazolobenzothiazole 2c.
4-(2-Chlorophenyl)-5-(N-methyl-N-phenylaminomethyl)-1,2,4-
triazole-3-thione (4a)
Yield: 1.90 g (82%); mp192–193 °C (EtOAc).
IR (KBr): 3100, 2940, 1350, 750 cm–1.
Yield: 0.168 g (56%); mp 176–178 °C.
1
H NMR (CDCl , 400 MHz): d = 2.63 (s, 3 H, NCH ), 4.20–4.48 (2
3
3
–
1
IR (KBr): 3078, 2928, 1600, 1404 cm .
× d, J = 16.5 Hz, 2 H, CH ), 6.41–7.65 (m, 9 H, ArH), 12.41 (s, 1 H,
SH).
2
Synthesis 2006, No. 22, 3841–3848 © Thieme Stuttgart · New York

3846
S. Aruna et al.
PAPER
1
3
C NMR (CDCl , 100 MHz): d = 38.7 (CH ), 48.7 (CH ), 113.1,
Yield: 0.123 g (42%); mp 123–125 °C (EtOAc).
IR (KBr): 3129, 2985, 1200, 644 cm–1.
3
3
2
1
(
18.2, 128.1, 129.0, 130.4, 130.6, 131.0, 131.5, 132.4, 148.1, 150.4
C=N), 169.0.
1
H NMR (CDCl , 400 MHz): d = 2.92 (s, 3 H, NCH ), 4.54 (s, 2 H,
2
+
3
3
MS (EI, 70 eV): m/z (%) = 330 (12) [M] , 332 (5) [M + 2], 295 (13),
2
1
CH ), 6.65–7.83 (m, 9 H, ArH).
25 (2), 190 (11), 189 (12), 146 (2), 134 (2), 149 (10), 120 (100),
06 (15), 90 (3), 77 (29).
1
3
C NMR (CDCl , 100 MHz): d = 29.4 (CH ), 30.6 (CH ), 110.8,
3
3
2
1
14.3, 116.8, 118.3, 124.7, 126.1, 126.6, 129.0, 129.5, 129.7, 147.7,
Anal. Calcd for C H N SCl: C, 58.08; H, 4.57; N, 16.94. Found:
C, 58.12; H, 4.56; N, 17.21.
1
6
15
4
1
48.1.
+
MS (EI, 70 eV): m/z (%) = 294 (92) [M] , 295 (18), 189 (9), 176 (6),
1
1
48 (8), 147 (10), 146 (29), 145 (100), 117 (34), 118 (52), 116 (10),
03 (5), 77 (10).
4
3
-(2-Chlorophenyl)-5-(4-methylphenoxymethyl)-1,2,4-triazole-
-thione (4b)
A mixture of 2-(4-methylphenoxy)acethydrazide (1.26 g, 7 mmol)
and 2-chlorophenyl isothiocyanate (1.18 g, 7 mmol) in aq K CO
Anal. Calcd for C H N S: C, 65.28; H, 4.79; N, 19.03. Found: C,
65.35; H, 4.77; N, 18.84.
1
6
14
4
2
3
(10%, 100 mL) was refluxed for 6 h which, after work-up as men-
tioned above, afforded the thione 4b.
1
(
4
-(4-Methylphenoxymethyl)-1,2,4-triazolo[3,4-b]benzothiazole
5b)
-(2-Chlorophenyl)-5-(4-methylphenoxymethyl)-1,2,4-triazole-3-
Yield: 1.80 g (78%); mp 166–168 °C.
–
1
IR (KBr): 3154, 2928, 1354, 700 cm .
thione 4b (0.33 g, 1 mmol) in MeCN (150 mL) containing NaOH (2
M, 30 mL) was irradiated using a TFR (254 nm) for 2.5 h. Usual
work-up followed by chromatographic separation furnished the
benzothiazole 5b.
1
H NMR (CDCl , 400 MHz): d = 2.24 (s, 3 H, CH ), 4.77–5.01 (2 ×
3
3
d, J = 12.7 Hz, 2 H, CH ), 6.64–7.18 (2 × d, J = 8.3 Hz, 4 H, ArH),
7
2
.46–7.63 (m, 4 H, ArH), 12.65 (s, 1 H, SH).
1
3
C NMR (CDCl , 100 MHz): d = 20.5 (CH ), 60.5 (CH ), 114.7,
Yield: 0.112 g (38%); mp 149–151 °C (EtOAc).
IR (KBr): 3098, 2929, 1100, 544 cm–1.
3
3
2
1
1
28.1, 130.0, 130.6, 130.7, 130.8, 131.5, 131.8, 132.6, 148.6 (C=N),
55.0, 169.4.
1
H NMR (CDCl , 400 MHz): d = 2.21 (s, 3 H, CH ), 5.5 (s, 2 H,
2
+
3
3
MS (EI, 70 eV): m/z (%) = 331(27) [M] , 333 (12) [M + 2], 296
(
1
(
CH ), 6.94–7.18 (2 × d, J = 8.4Hz, 4 H), 7.33–7.91 (m, 4 H, ArH).
91), 295 (31), 225 (11), 224 (19), 190 (17), 189 (61), 188 (100),
70 (20), 149 (24), 116 (34), 108 (58), 107 (53), 90 (10), 79 (24), 64
10).
1
3
C NMR (CDCl , 100 MHz): d = 38.8 (CH ), 48.8 (CH ), 113.2,
3
3
2
1
1
18.3, 129.0, 129.1, 130.5, 130.7, 131.6 (all CH), 128.3, 130.9,
31.2, 132.5, 148.2, 150.5 (all C).
Anal. Calcd for C H N SOCl: C, 57.92; H, 4.25; N, 12.66. Found:
C, 57.62; H, 4.34; N, 12.66.
1
6
14
3
+
MS (EI, 70 eV): m/z (%) = 295 (39) [M] , 294 (85), 189 (100), 146
(
38), 145 (34), 118 (28), 176 (31), 91 (28), 77 (23).
4
1
-(2-Chloro-6-methylphenyl)-5-(2-methylphenoxymethyl)-
,2,4-triazole-3-thione (4c)
Anal. Calcd for C H N OS: C, 65.06; H, 4.43; N, 14.22. Found:
C, 65.12; H, 4.42; N, 14.01.
1
6
13
3
A mixture of 2-(2-methylphenoxy)-acethydrazide (1.26 g, 7 mmol)
and 2-chloro-6-methylphenyl isothiocyanate (1.28 g, 7 mmol) in aq
K CO (10%, 100 mL) was heated under reflux for 7 h to furnish the
Irradiation of 4c
2
3
Irradiation of an MeCN (150 mL) solution of thione 4c (0.35 g, 1
mmol) containing NaOH (2 M, 30 mL) in a TFR for 2 h, followed
by usual work-up gave a crude mixture that was purified by chro-
matography (PE–EtOAc, 1:1) to give benzothiazole 5c. Further elu-
tion (PE–EtOAc, 3:4) afforded the triazole 6.
thione 4c.
Yield: 2.0 g (83%); mp 198–200 °C.
–
1
IR (KBr): 3100, 2928, 1550, 1350 cm .
1
H NMR (CDCl , 400 MHz): d = 2.21 and 2.24 (2 × s, 6 H, 2 ×
3
CH ), 4.67–4.99 (2 × d, J = 12.7 Hz, 2 H, CH ), 6.67–7.48 (m, 7 H,
ArH), 11.89 (s, 1 H, SH).
8-Methyl-1-(2-methylphenoxymethyl)-1,2,4-triazolo[3,4-b]ben-
zothiazole (5c)
3
2
1
3
Yield: 0.098 g (32%); mp 146–148 °C (EtOAc).
C NMR (CDCl , 100 MHz): d = 18.7 (CH ), 20.7 (CH ), 60.9
2
3
3
3
–
1
(
CH ), 114.7, 114.9, 128.1, 128.4, 129.9, 130.1, 130.3, 131.6,
IR (KBr): 3145, 2927, 1340, 1200 cm .
1
31.8, 140.4, 148.8 (C=N), 155.6, 168.2.
1
H NMR (CDCl , 400 MHz): d = 2.11, 2.64 (2 × s, 6 H, 2 × CH ),
3
3
+
MS (EI, 70 eV): m/z (%) = 345 (8) [M] , 347 (6) [M + 2], 310 (24),
4.73–5.02 (2 × d, J = 12.4 Hz, 2 H, CH ), 6.99–7.50 (m, 7 H, ArH).
13
2
238 (16), 204 (10), 203 (9), 201 (9), 169 (9), 163 (11), 162 (9), 108
C NMR (CDCl , 100 MHz): d = 20.0 (CH ), 20.5 (CH ), 61.9
3
3
3
(30), 107(31), 79 (36), 77 (100).
(
CH ), 114.7, 122.5, 126.4, 126.7, 127.2, 128.1, 128.8, 129.9,
2
Anal. Calcd for C H N OSCl: C, 59.04; H, 4.66; N, 12.14. Found:
130.2, 130.3, 130.7, 131.4, 132.8, 155.0.
1
7
16
3
C, 59.10; H, 4.42; N, 11.84.
+
MS (EI, 70 eV): m/z (%) = 309 (27) [M] , 201 (100), 202 (23), 162
81), 161 (35), 108 (27), 107 (36), 79 (36), 77 (86).
(
1-(N-Methyl-N-phenylaminomethyl)-1,2,4-triazolo[3,4-b]ben-
Anal. Calcd for C H N OS: C, 65.99; H, 4.88; N, 13.58. Found:
zothiazole (5a)
17 15
3
C, 65.82; H, 4.75; N, 13.67.
An MeCN (150 mL) solution of triazole-3-thione 4a (0.33 g, 1
mmol), containing NaOH (2 M, 30 mL) was flushed with nitrogen
for 1 h then irradiated in a TFR (254 nm) for 2 h. After the reaction
was complete (monitored by TLC), the acetonitrile was removed
under reduced pressure from the two-phase mixture and the aqueous
layer was extracted with EtOAc (3 × 25 mL). The organic layer was
separated and the aqueous layer was neutralized with dil. HCl then
extracted with EtOAc (2 × 20 mL). The combined organic layers
were evaporated and the residue was purified by chromatography
4
1
-(2-Chloro-6-methylphenyl)-3-(2-methylphenoxymethyl)-
,2,4-triazole (6)
Yield: 0.056 g (18%); mp 90–92 °C.
IR (KBr): 3032, 2985, 1520 (C=N) cm–1.
1
H NMR (CDCl , 400 MHz): d = 2.13, 2.28 (2 × s, 6 H, 2 × CH ),
.95–5.28 (2 × d, J = 12.5 Hz, 2 H, CH ), 6.65–7.48 (m, 7 H, ArH),
3
3
4
2
8.19 (s, 1 H, C5-H).
(silica gel; EtOAc–PE, 1:1) to furnish the benzothiazole 5a.
Synthesis 2006, No. 22, 3841–3848 © Thieme Stuttgart · New York

PAPER
Synthesis and Photocyclization of 1,2,4-Triazole-3-thiones
3847
1
3
C NMR (CDCl , 100 MHz): d = 18.0 (CH ), 20.4 (CH ), 60.3
2
Synthesis of Substituted 1,2,4-Triazole-3-thiones 10a–c; Typical
Procedure
3
3
3
(
CH ), 114.3, 127.8, 129.6, 129.9, 130.5, 131.0, 131.1, 132.2,
138.6, 144.2, 150.7, 155.5.
A mixture of glycine hydrazide (1.24 g, 14 mmol) and o-chlorophe-
+
nyl isothiocyanate (2.36 g, 14 mmol) in K CO (10%, 100 mL) was
refluxed for 6 h, cooled, filtered and the filtrate was washed with
2 3
MS (EI, 70 eV): m/z (%) = 313 (20) [M] , 314 (10), 278 (45), 206
(
(
40), 192 (10), 172 (34), 171 (29), 165 (24), 107 (33), 79 (46), 77
100).
Et O. The aqueous layer was neutralized with cold dil. HCl and the
2
separated solid was filtered and washed with H O to furnish the tri-
2
Anal. Calcd for C H N OCl: C, 65.07; H, 5.14; N, 13.39. Found:
1
7
16
3
azole-3-thione 10a.
C, 64.89; H, 5.28; N, 13.52.
4
-(2-Chlorophenyl)-5-(2-chlorophenylamino)-1,2,4-triazole-3-
Synthesis of Substituted 1,2,4-Triazole-3-thiones 7a,b
17
thione (10a)
Yield: 1.88 g (80%); mp 222–224 °C (EtOAc) (Lit. 218–219 °C).
The synthetic procedure and the experimental data of compounds
17
7
a,b were reported earlier.6
–
1
IR (KBr): 3379 (NH), 3100, 2925, 1492 (C=N), 744 cm .
1
Irradiation of 7a
A benzene (180 mL) solution of triazole-3-thione 7a (0.3g, 0.9
mmol) containing Et N (0.9 g, 9 mmol) was flushed with nitrogen
H NMR (CDCl , 400 MHz): d = 6.34 (s, 1 H, NH), 6.91–7.65 (m,
3
6 H, ArH), 7.75 and 8.10 (2 × d, J = 7.33 Hz, 2 H), 11.07 (s, 1 H,
SH).
3
for 1 h then irradiated in an Applied Photophysics multilamp reactor
13
C NMR (CDCl , 100 MHz): d = 118.6, 123.4, 128.1, 129.1, 131.4,
3
(254 nm) for 80 h. The solvent was removed under reduced pres-
1
32.6 (all CH) 128.8 (both CH and C), 121.4, 133.5, 134.4, 146.9
sure, and the residue was purified by chromatography (silica gel;
petrol–EtOAc, 9:1) to give the azepine 9a. Further elution (PE–
EtOAc, 1:1) gave the thiazine 8a (11%) and finally (PE–EtOAc,
(all C), 166.1.
+
MS (EI, 70 eV): m/z (%) = 336 (31) [M] , 338 (17) [M + 2], 340 (5)
[
(
M + 4], 301 (100), 303 (37), 269 (7), 152 (11), 127 (6), 125 (5), 119
19), 77 (9).
3:7) the starting triazole-3-thione 7a was recovered (22%).
1
,2,4-Triazolo[4,3-a]-(3,4)(5,6)-dibenz-7H-azepine-3[2H]-
4
-(2-Chlorobenzyl)-5-(2-chlorobenzylamino)-1,2,4-triazole-3-
thione (9a)
Yield: 0.010 g (4%); mp 150–152 °C.
thione (10b)
A mixture of glycine hydrazide (1.24 g, 14 mmol) and o-chloroben-
zyl isothiocyanate (2.56 g, 14 mmol) in K CO (10%, 100 mL) was
refluxed for 6 h. Work-up as described above afforded the thione
–1
IR (KBr): 3058, 2864, 2650, 1565, 1469, 1340, 1175 cm .
2
3
1
H NMR (CDCl 400 MHz): d = 5.45 (s, 2 H, CH ), 7.26–7.44 (m,
3,
2
6
H, ArH), 8.08–8.09 (m, 2 H, ArH).
10b.
1
3
C NMR (CDCl , 100 MHz): d = 49.1, 126.0, 126.6, 127.1, 128.2,
Yield: 1.73 g (68%); mp 198–200 °C.
IR (KBr): 3319 (NH), 3125, 2928, 1438, 776 cm–1.
3
1
28.3, 128.7, 129.6, 139.4, 140.1, 161.9.
+
MS (EI, 70 eV): m/z (%) = 265 (100) [M] , 264 (50), 205 (2), 161
(
1
H NMR (CDCl , 400 MHz): d = 4.56 (s, 2 H, HNCH ), 5.31 (s,
3
2
12), 135 (6), 134 (12), 129 (6), 121 (15), 104 (14), 103 (7), 89 (12).
2
H, NCH ), 6.67 (s, 1 H, NH), 7.25–7.87 (m, 8 H, ArH), 11.35 (s,
2
UV (MeOH): lmax = 252, 234 nm.
1 H, SH).
13
Anal. Calcd for C H N S: C, 67.89; H, 4.17; N, 15.83. Found: C,
C NMR (CDCl , 100 MHz): d = 42.8 (CH ), 45.0 (CH ), 126.9,
3 2 2
1
5
11
3
68.05; H, 4.32; N, 15.62.
127.8, 129.2, 129.6, 129.8, 130.1, 129.8 (all CH), 128.9 (both CH
and C), 131.6, 132.6, 134.6, 151.5 (all C) 165.9 (C=S).
1
3
2-Methyl-1,2,4-triazolo[4,3-a]-(3,4)(5,6)-dibenz-7H-azepine-
[2H]-thione (9b)
+
MS (EI, 70 eV): m/z (%) = 364 (16) [M] , 366 (14) [M + 2], 330
(
(
24), 331 (10), 332 (13), 329 (100), 295 (10), 256 (6), 239 (10), 204
9), 129 (15), 127 (26), 125 (90), 99 (9), 89 (19), 85 (8), 73 (21).
Irradiation of thione 7b (0.3 g, 1 mmol) in benzene (180 mL) con-
taining Et N (0.96 g, 10 mmol) using a MLR for 62 h, followed by
chromatographic separation, afforded the azepine 9b, in addition to
the triazolo benzothiazine 8b (15%) and the starting thione 7b
3
Anal. Calcd for C H Cl N S: C, 52.61; H, 3.86; N, 15.33. Found:
16 14
2
4
C, 52.73; H, 3.78; N, 15.42.
(
20%).
4
-Phenyl-5-phenylamino-1,2,4-triazole-3-thione (10c)18
Yield: 0.040 g (5%); mp 208–210 °C.
A mixture of glycine hydrazide (1.24 g, 14 mmol) and phenyl
isothiocyanate (1.89 g, 14 mmol) in K CO (10%, 100 mL) was re-
–
1
IR (KBr): 3020, 2916, 2856, 2642, 1573, 1463, 1328, 1170 cm .
2
3
1
fluxed for 6 h. Work-up as described above afforded the thione 10c.
Yield: 1.27 g (68%); mp 201–203 °C (Lit.18 206–208 °C).
H NMR (CDCl 400 MHz): d = 2.39 (s, 3 H, CH ), 5.43 (s, 2 H,
2
3,
3
CH ), 7.24 (s, 1 H, C10-ArH), 7.30–7.41 (m, 4 H, ArH), 7.96–7.98
(
m, 2 H, ArH).
IR (KBr): 3301, 2923, 1612, 1446, 762 cm–1.
13
C NMR (CDCl , 100 MHz): d = 21.7, 50.7, 126.2, 127.3, 127.7,
28.1, 128.3, 128.7, 129.3, 139.5, 147.0, 162.6.
1
3
H NMR (CDCl , 400 MHz): d = 6.39 (s, 1 H, NH), 6.94–7.63 (m,
3
1
1
0 H, ArH), 13.09 (s, 1 H, SH).
+
MS (EI, 70 eV): m/z (%) = 279 (100) [M] , 278 (88), 161 (16), 118
13C NMR
(CDCl , 100 MHz): d = 117.3, 121.5, 128.1, 128.2,
3
(22), 104 (13), 90 (25), 77 (18).
1
29.3, 129.3, 131.8, 138.5, 147.4, 164.7.
UV (MeOH): lmax = 254, 208 nm.
+
MS (EI, 70 eV): m/z (%) = 268 (100) [M] , 267 (47), 236 (8), 235
(15), 209 (5), 195 (13), 194 (8), 135 (8), 133 (9), 103 (5), 93 (19),
77 (93), 66 (6).
Anal. Calcd for C H N S: C, 68.78; H, 4.69; N, 15.04. Found: C,
1
6
13
3
68.57; H, 4.82; N, 15.30.
The triazolo benzothiazines 8a,b obtained from 7a,b were com-
pared by mp and mixture-mp, and their IR spectra were found to be
superimposable with those obtained under MeCN/NaOH condi-
1
3
,2,4-Triazolo[4,3-a]-13H-(4,5)(6,7) dibenzo[1,3]diazepine-
(2H)-thione (11)
6
A MeCN solution (150 mL) of 4-(2-chlorophenyl)-5-(2-chlorophe-
nylamino)-1,2,4-triazole-3-thione 10a (0.34 g 1 mmol) containing
aq NaOH (2 M, 30 mL), was flushed with nitrogen for 1 h and then
tions.
Synthesis 2006, No. 22, 3841–3848 © Thieme Stuttgart · New York

3848
S. Aruna et al.
PAPER
irradiated at 254 nm in a TFR for 2 h. After completion of the reac- Acknowledgment
tion (monitored by TLC), the solvent was removed under reduced
We wish to thank the University of Madras, Chennai, for the Uni-
versity Research Fellowship (URF) and CSIR-New Delhi for provi-
ding the research fellowships (SRF) (S.A., A.S.V & D.T) and the
University Grants Commission, New Delhi, for the Special Assi-
stance Programme to the Department of Organic Chemistry.
pressure from the two-phase mixture followed by extraction with
EtOAc (3 × 25 mL). The organic layer was separated and the aque-
ous layer was neutralized with dil. HCl then extracted with EtOAc
(
2 × 20 mL). The organic layers were combined, dried, and concen-
trated to give a residue, which was purified by chromatography
EtOAc–PE, 3:4) to furnish the thione 11.
(
Yield: 0.114 g (43%); mp 210–212 °C.
References
–1
IR (KBr): 3313 (NH), 3186, 1334 (C=S), 775 cm .
(1) Paramasivam, R.; Palaniappan, R.; Ramakrishnan, V. T. J.
1
H NMR (CDCl , 400 MHz): d = 6.48 (s, 1 H, NH), 7.31–7.58 (m,
Chem. Soc., Chem. Commun 1979, 260.
(2) Muthusamy, S.; Ramakrishnan, V. T. Synth. Commun. 1992,
22, 519.
3
4
1
H, ArH), 7.67, 7.81, 7.85, 8.16 (4 × d, J = 7.8 Hz (all), 4 H, ArH),
1.89 (s, 1 H, NH).
1
3
(3) Jayanthi, G.; Muthusamy, S.; Ramakrishnan, V. T. J.
Photochem. Photobiol. A 1998, 116, 103.
C NMR (CDCl , 100 MHz): d = 109.6, 114.0, 119.8, 121.0, 123.8,
3
1
1
25.7, 127.5 (all CH), 123.2 (both CH and C), 127.0, 127.6, 130.8,
44.7 (all C), 144.9.
(
4) Senthilvelan, A.; Ramakrishnan, V. T. Tetrahedron Lett.
002, 43, 5119.
2
+
MS (EI, 70 eV): m/z (%) = 266 (16) [M] , 267 (3), 264 (100), 237
(
(
(5) Horspool, W. H.; Song, P. S. CRC Handbook of Organic
Photochemistry and Photobiology; CRC Press: New York,
8), 211 (10), 206 (82), 179 (3), 159 (28), 131 (26), 108 (38), 90
10), 77 (8).
1
995, 250.
(
(
(
6) Senthilvelan, A.; Thirumalai, D.; Ramakrishnan, V. T.
Tetrahedron 2004, 60, 851.
Anal. Calcd for C H N S: C, 63.13; H, 3.78; N, 21.03. Found: C,
1
4
10
4
63.33; H, 3.71; N, 21.23.
7) Depuy, C. H.; Chapman, O. L. Molecular Reactions and
Photochemistry; Prentice-Hall: New Delhi, 1998, 35.
8) Levy, G. C.; Lichter, R. L.; Nelson, G. L. Carbon-13
Nuclear Magnetic Resonance Spectroscopy, 2nd ed.; John
Wiley & Sons: New York, 1980.
1-(2-Chlorobenzylamino)-1,2,4-triazolo(3,4-b)-1,3-(4H)-ben-
zothiazine (12)
A MeCN solution (150 mL) of 4-(2-chlorobenzyl)-5-(2-chloroben-
zylamino)-1,2,4-triazole-3-thione 10b (0.37 g, 1 mmol) containing
aq NaOH (2 M, 30 mL) was flushed with nitrogen for 1 h then irra-
diated at 254 nm in a TFR for 2 h. Work-up and purification, as de-
scribed above, afforded benzothiazine 12.
(
9) Turro, N. J. Modern Molecular Photochemistry; The
Benjamin/Cummings Publishing Company Inc.: Menlo Park
CA, 1978.
(
10) Park, Y.-T.; Jung, C.-H.; Kim, K.-W.; Kim, H. S. J. Org.
Chem. 1999, 64, 8546.
(11) Katritzky, A. R. Adv. Heterocycl. Chem. 1967, 8, 52.
(12) Katritzky, A. R. Adv. Heterocycl. Chem. 1967, 8, 22.
13) Katritzky, A. R. Adv. Heterocycl. Chem. 1967, 8, 39.
14) Wang, L.; Ramachandra, S. H. Bioorg. Med. Chem. Lett.
Yield: 0.164 g (50%); mp 180–182 °C.
–1
IR (KBr): 3367, 2931, 2349, 1751, 1584, 1450, 748 cm .
1
H NMR (CDCl , 400 MHz): d = 4.63 (s, 2 H, CH ), 4.81 (s, 1 H,
3
2
(
(
CH), 5.26 (s, 2 H, CH ), 6.76 and 6.89 (2 × s, 2 H, NH), 7.29–7.47
(
2
m, 8 H, ArH).
2
001, 11, 2893.
1
3
C NMR (CDCl , 100 MHz): d = 45.4, 49.4, 80.0, 125.0, 126.1,
3
(15) Kobayashi, Y.; Nakano, T.; Nakajima, M.; Kumadaki, I.
1
26.7, 127.6, 127.9, 128.3, 129.1, 129.8, 132.9, 134.8, 134.9, 137.0,
Tetrahedron Lett. 1981, 22, 1113.
157.4.
(
16) De Stevens, G.; Dughi, M. J. Am. Chem. Soc. 1961, 83,
+
MS (EI, 70 eV): m/z (%) = 330 (24) [M] , 293 (100), 203 (14), 148
3087.
(
12), 127 (18), 89 (26), 77 (19).
(17) Dubenko, R. G.; Pel'kis, P. S. Zh. Obshch. Khim. 1963, 33,
220.
2
Anal. Calcd for C H N SCl: C, 58.09; H, 4.57; N, 16.94. Found:
C, 58.18; H, 4.68; N, 17.12.
1
6
15
4
(
18) Hassan, A. A.; Mourad, A.-F. E.; Kamal, M. E.-S.; Ashraf,
H. A.-Z.; Dopp, D. Heteroat. Chem. 2003, 14, 535.
Synthesis 2006, No. 22, 3841–3848 © Thieme Stuttgart · New York