Facile synthesis of 3-aryl-1-((4-aryl-1,2,3-selenadiazol-5-yl)sulfanyl) isoquinolines

Article abstract of DOI:10.2478/s11696-011-0074-6

A new series of 1,2,3-selenadiazoles containing an aryl or a 3-arylisoquinoline sulfanyl moiety at carbons 4 and 5, respectively, was prepared by cyclization of the respective semicarbazones in the presence of selenium(II) oxide and tetrahydrofuran at 70-

Full text of DOI:10.2478/s11696-011-0074-6

Chemical Papers 65 (6) 883–889 (2011)
DOI: 10.2478/s11696-011-0074-6
ORIGINAL PAPER
Facile synthesis
of 3-aryl-1-((4-aryl-1,2,3-selenadiazol-5-yl)sulfanyl)isoquinolines
b
aKamalakannan Prabakaran, a,bFazlur-Rahman Nawaz Khan*, Jong Sung Jin*,
a
bEuh Duck Jeong, Pitchai Manivel
aOrganic & Medicinal Chemistry Research Laboratory, Organic Chemistry Division, School of Advanced Sciences,
VIT University, Vellore, 632014 Tamil Nadu, India
bDivision of High Technology Materials Research, Busan Center, Korea Basic Science Institute,
618-230 Busan, Republic of Korea
Received 15 April 2011; Revised 14 June 2011; Accepted 15 June 2011
A new series of 1,2,3-selenadiazoles containing an aryl or a 3-arylisoquinoline sulfanyl moiety at
carbons 4 and 5, respectively, was prepared by cyclization of the respective semicarbazones in the
presence of selenium(II) oxide and tetrahydrofuran at 70–75◦C. Semicarbazones required for the
reaction were obtained from 2-((3-arylisoquinolin-1-yl)sulfanyl)-1-phenylethanones, I, by a reaction
with semicarbazide hydrochloride in ethanol/water mixture and potassium acetate base.
c
ꢀ 2011 Institute of Chemistry, Slovak Academy of Sciences
Keywords: 1,2,3-selenadiazoles, isoquinolines, cyclization, semicarbazones, phenylethanones
Introduction
with a wide spectrum of biological activities. They are
widely used as pharmaceuticals and agrochemicals. A
number of papers mention the use of isoquinolines and
their thio analogues’ derivatives in medicinal chem-
istry. Thus, their synthesis has been of great interest
in the preparation of biologically active selenium and
sulfur containing heterocyclic compounds.
Heterocyclic compounds containing selenium are
of interest due to their biological and synthetic ap-
plications. Synthesis of 1,2,3-selenadiazoles is of re-
cent interest as they are not only versatile intermedi-
ates for the preparation of alkynes and other selenium
compounds (Al-Smadi & Ratrout, 2004a, 2004b), but
they also have attracted much attention for their bio-
logical characteristics like their antifungal, antibacte-
rial, antimicrobial, and insecticidal activities (Kandeel
et al., 1994; Schatz, 1960). The chemistry of 1,2,3-
selenathiadiazoles has been recently reviewed by dif-
ferent researchers (Arsenyan et al., 2002; Morzherin
et al., 2003; Saravanan et al., 2006; Dehaen et al.,
2004; Meier & Voigt, 1972). In continuation of our
study on 1,2,3-selenadiazoles, the synthesis of yet an-
Selenadiazoles are organoselenium compounds that
possess a broad-spectrum of potent antitumor and
other related biological activities (Niculescu-Duvaz,
2001; Murray et al., 1963; Burger & Abraham, 2003).
The use of the selenium containing compounds syn-
thesis has steadily increased and it has been utilized
in organic synthesis (Takimiya et al., 2004). Though a
large scale of thiadiazoles is known, only few selenadia-
zoles have been reported (Al-Smadi & Ratrout, 2004a,
2004b; Cillo & Lash, 2004; Vernon et al., 1983). The
synthesis of an 1,2,3-selenadiazole was first reported
by Lalezari et al. (1969, 1973) and Yalpani et al. (1971)
and it was done by analogy with the 1,2,3-thiadiazole
system (Hurd & Mori, 1955; Saravanan et al., 2006,
2008). Selenium compounds have many applications;
they are electroluminescent (Yang et al., 2005), and
potential candidates for two-photon absorption, non-
linear optics, and sensor applications (Ostrowski et
al., 2003; Velusamy et al., 2005). Isoquinoline deriva-
tives represent a group of the most active compounds
*Corresponding author, e-mail: nawaz f@yahoo.co.in; jsjin@kbsi.re.kr

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K. Prabakaran et al./Chemical Papers 65 (6) 883–889 (2011)
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other 1,2,3-selenadiazole system with a potential func-
tionality in its skeleton is reported and the target
molecules are expected to have enhanced their bio-
logical activity. As a part of our ongoing research
on organosulfur and organoselenium compounds, 3-
substituted isoquinolines and their thionate deriva-
tives were reported earlier (Prabakaran & Nawaz
Khan, 2010; Manivel & Nawaz Khan, 2009; Manivel
et al., 2009a, 2009b, 2010). Based on the aforemen-
tioned importance of selenium containing compounds
and their further utilization in organic synthesis,
a new series of 3-aryl-1-((4-aryl-1,2,3-selenadiazol-5-
yl)sulfanyl) isoquinolines, III, from their correspond-
ing semicarbazones is reported herein (Fig. 1).
arated in high purity and yield (76–93 %). Semicar-
bazones, II, (0.24 mmol) were dissolved in tetrahy-
drofuran (THF) (4 mL) under vigorous stirring. The
above solution was treated with selenium(II) oxide
(SeO2) powder (2.4 mmol) and heated at 70–75◦C.
The reactions were monitored by thin layer chromath-
ography (TLC) (eluent: hexane/ethyl acetate, ϕr =
7 : 3) until the completion of the reaction (4 h). In
TLC, the products appeared to be significantly less
polar compared to the polar semicarbazones. The re-
action mixtures were filtered to remove excess SeO2,
and the filtrates were concentrated to dryness un-
der vacuum to afford crude selenadiazoles, III, which
were further purified by column chromatography us-
ing petrol ether/ethyl acetate gradient elution (from
ϕr = 9 : 1 to ϕr = 17 : 2) and afforded pure compound
in good yields (78–91 %).
Experimental
All reagents purchased from Sigma–Aldrich (In-
dia), Lancaster (India), and Qualigens (India) were
used without further purification. Infrared (IR) spec-
tra were recorded at room temperature from 4000
cm−1 to 400 cm−1 using Avatar 330 (ALPHA-T,
Bruker, India) equipped with a deuterated triglycine
sulfate detector. Most of the obtained vibrational
bands of the IR spectrum were identified. 1H NMR
and 13C NMR spectra (400 MHz for 1H and 100
MHz for 13C) of the compounds were obtained us-
ing a Bruker Spectrospin Avance DPX400 Ultrashield
400 MHz spectrometer (Bruker, India) and chemi-
cal shifts were reported in δ relative to tetramethyl-
silane (TMS) as an internal standard. Mass spec-
tra were obtained using an Agilent mass spectrom-
eter 6200 series accurate (Agilent, India). Melting
points were determined using open capillaries and
are uncorrected (a model BUCHI M-565, Bu¨chi,
Switzerland). Elemental analysis was carried using
an Elementar–Vario Micro cube CHNSO analyser
(Elementar, Germany). The 2-((3-arylisoquinolin-1-
yl)sulfanyl)-1-phenylethanones, I, required for the
present study were obtained according to a procedures
reported earlier (Manivel et al., 2010; Hathwar et al.,
2007a, 2007b; Tajudeen & Nawaz Khan, 2007; Mo-
hana Roopan et al., 2008).
Results and discussion
The experiments were started with an attempted
synthesis of semicarbazones, II, from I, through a re-
action with semicarbazide hydrochloride in the pres-
ence of absolute ethanol and potassium acetate under
reflux conditions and stirring in the presence of wa-
ter. Semicarbazones, II, when treated afterwards with
SeO2 in the presence of THF at 70–75◦C afforded the
desired products, III, in good yields and high purity
(Fig. 1).
Optimization of the semicarbazone formation was
carried out by reacting 2-((3-phenyl-isoquinolin-1-
yl)sulfanyl)-1-phenylethanone, Ia, with semicarbazide
hydrochloride in the presence of ethanol/water mix-
ture (ϕr = 15 : 1), potassium acetate in a round bot-
tom flask, under reflux at 90◦C. When the reaction
was analyzed by LC-MS, only 40 % conversion to the
desired product and 59 % of the starting material was
present after 16 h of the reaction. Then, the reaction
continued for different time periods and the corre-
sponding conversions are shown in Table 1. However,
when the reaction was carried out in a pressure tube
at 90◦C, it was successfully completed within 16 h pro-
viding the products in excellent yields. A comparison
of results obtained from both methods is presented in
Table 1.
Considering these optimized results, various semi-
carbazones were synthesized, isolated, purified by re-
crystallization in ethanol, and characterized by spec-
tral techniques such as LC-MS, 1H NMR and 13C
NMR. Purified semicarbazones were then allowed to
react with SeO2, in THF, in pressure tubes at 70–75◦C
for 4 h to afford the desired products, III, (Fig. 1).
Optimization of the reaction was studied by varying
the amount of SeO2 and that of the solvents. From
Table 2 it is clear that an increase in the amount of
SeO2 increased the yield steadily. Similarly, the reac-
tion of IIa and SeO2 in various solvents was found to
be proceeding well when THF was used (Table 3, en-
General procedure for the preparation of semi-
carbazones, IIa–IIf, and 1,2,3-selenadiazole
derivatives, IIIa–IIIf
To I, (0.3 mmol), the filtrate obtained from a mix-
ture of semicarbazide hydrochloride (2.1 mmol) and
potassium acetate (2.1 mmol) in absolute ethanol (8
mL) heated under reflux condition for 30 min and
filtered to remove precipitated NaCl was added and
mixed, the resulting solution was heated and refluxed
in a pressure tube for 16 h. The reaction was mon-
itored by the LC-MS technique. Then, the reaction
mixture was diluted with cold water (8 mL) and
stirred for 30 min. Yellow semicarbazone, II, was sep-

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K. Prabakaran et al./Chemical Papers 65 (6) 883–889 (2011)
Table 1. Comparison of conventional (C) and pressure tube
(P) methods in the reaction of Ia and semicarbazide
hydrochloride
Table 2. SeO2 optimization in the reaction of IIa (0.24 mmol)
SeO2
Yielda
%
Entry
Time
h
Product IIa conversion
mmol
Method
1
2
3
4
5
6
7
8
9
1.00
1.20
1.44
1.68
1.92
2.16
2.40
2.64
2.88
36
43
58
69
73
87
91
91
91
%
C
P
C
P
C
P
C
P
C
P
16
16
24
24
36
36
48
48
60
60
40
92
55
–
65
–
80
–
85
–
a) LC-MS purity.
a) LC-MS purity.
Table 3. Effect of solvent in the reaction of IIa and SeO2
Entry
Solvent
Yielda/%
try 4) unlike the other solvents tested, i.e. acetic acid,
toluene, o-xylene, 1,4-dioxane, and acetonitrile, which
provided lower yields (Table 3).
1
2
3
4
5
6
Acetic acid
Toluene
o-Xylene
THF
1,4-Dioxane
Acetonitrile
55
63
58
89
64
67
Results of the selenadiazoles, III, synthesis are
summarized in Table 4. Products of the reaction
were isolated, purified by column chromatography and
characterized by spectral techniques such as IR, LC-
1
MS, H NMR, 13C NMR, and elemental analysis (Ta-
a) Isolated yields.
bles 4 and 5).
The characteristic IR spectra showed bands for
Table 4. Characterization data of newly prepared compounds semicarbazones IIa–IIf and selenadiazoles IIIa–IIIf
wi(calc.)/%
wi(found)/%
Yield
M.p.
Compound
Formula
Mr
C
H
N
S
%
◦C
IIa
IIb
C24H20N4OS
C25H19F3N4OS
C25H21ClN4O2S
C26H18F6N4OS
C24H19ClN4OS
C24H18ClFN4OS
C23H15N3SSe
412.14
480.12
476.11
548.11
446.10
464.09
445.02
513.00
508.99
580.99
478.98
496.97
69.88
69.81
62.49
62.51
62.95
62.88
56.93
56.87
64.49
64.41
62.00
62.03
62.16
62.12
56.26
56.22
56.65
56.58
51.73
51.67
57.69
57.61
55.60
55.56
4.89
4.83
3.99
3.94
4.44
4.38
3.31
3.26
4.28
4.22
3.90
3.84
3.40
3.36
2.75
2.69
3.17
3.11
2.26
2.21
2.95
2.90
2.64
2.57
13.58
13.55
11.66
11.62
11.75
11.71
10.21
10.16
12.54
12.48
12.05
12.01
9.46
9.41
8.20
8.17
8.26
8.21
7.24
7.17
8.78
7.77
7.69
6.67
6.59
6.72
6.65
5.85
5.79
7.17
7.11
6.90
6.87
7.22
7.17
6.26
6.21
6.30
6.26
5.52
5.46
6.70
6.65
6.45
6.39
88
234–235
86
76
83
93
90
91
83
78
88
90
89
253–254
249–250
242–243
245–246
246–247
195–196
252–255
168–169
278–281
203–204
217–218
IIc
IId
IIe
IIf
IIIa
IIIb
IIIc
IIId
IIIe
IIIf
C24H14F3N3SSe
C24H16ClN3OSSe
C25H13F6N3SSe
C23H14ClN3SSe
C23H13ClFN3SSe
8.72
8.46
8.39

K. Prabakaran et al./Chemical Papers 65 (6) 883–889 (2011)
887
Table 5. Spectral data of newly prepared compounds semicarbazones IIa–IIf and selenadiazoles IIIa–IIIf
Compound
Spectral data
IIa
IR, ν˜/cm−1: 3472, 3394, 3281, 3196, 3138, 1713, 1586, 1491, 1437, 1308, 1159, 984, 846, 761, 686, 576, 470
1H NMR (DMSO-d6) δ: 9.80 (s, 1H), 8.32–8.31 (d, 2H, J = 7.2 Hz), 8.24 (s, 1H), 8.10–8.03 (dd, 2H, J = 19.6 Hz,
J = 8.4 Hz), 7.93–7.91 (m, 2H), 7.83–7.79 (t, 1H, J = 7.2 Hz), 7.66–7.62 (t, 1H, J = 7.2 Hz), 7.57–7.53 (t, 2H, J =
7.2 Hz), 7.47–7.44 (t, 1H, J = 7.2 Hz), 7.30–7.29 (m, 3H), 6.62 (bs, 2H), 4.92 (s, 2H)
13C NMR (DMSO-d6), δ: 157.1, 156.8, 148.6, 141.4, 138.3, 136.6, 136.2, 131.3, 128.9, 128.6, 128.2, 128.0, 127.8,
126.6, 125.1, 123.8, 113.4
MS, m/z: 413 (M+ + 1)
IIb
IIc
IR, ν˜/cm−1: 3476, 3396, 3283, 3198, 3139, 1716, 1589, 1490, 1438, 1308, 1159, 986, 846, 762, 686, 576
1H NMR (DMSO-d6) δ: 10.02 (s, 1H), 8.29–8.26 (d, 2H, J = 9.7 Hz), 8.21 (s, 1H), 8.12–8.01 (m, 4H), 7.81–7.77 (t,
1H, J = 7.2 Hz), 7.62–7.44 (m, 6H), 6.69 (bs, 2H), 4.93 (s, 2H)
13C NMR (DMSO-d6) δ: 157.3, 157.0, 149.1, 141.0, 140.4, 138.7, 136.6, 131.7, 129.2, 128.4, 128.3, 127.4, 127.0, 125.5,
125.4, 125.3, 124.2, 113.9, 24.2
MS, m/z: 481 (M+ + 1)
IR, ν˜/cm−1: 3282, 3199, 3158, 2925, 2854, 1717, 1645, 1593, 1492, 1465, 1407, 1325, 1284, 1251, 1228, 1153, 1045,
958, 889, 848, 773, 692, 657, 524
1H NMR (DMSO-d6) δ: 9.84 (bs, 1H), 8.15–8.13 (d, 2H, J = 8.3 Hz), 7.99–7.95 (m, 2H), 7.95–7.75 (t, 1H, J = 7.2
Hz), 7.65–7.40 (m, 5H), 7.12–7.10 (d, 1H, J = 10.8 Hz), 7.04 (s, 1H), 6.75 (m, 1H), 6.43 (bs, 2H), 4.59 (bs, 2H), 3.85
(s, 3H)
13C NMR (CDCl3) δ: 158.3, 153.7, 151.5, 143.3, 138.5, 136.8, 136.3, 132.7, 131.6, 129.1, 128.9, 128.2, 127.9, 127.8,
124.9, 123.8, 121.0, 120.7, 117.8, 112.4, 55.9, 31.9
MS, m/z: 477 (M+ +1)
IId
IIe
IIf
IR, ν˜/cm−1: 3283, 3198, 3155, 2925, 1727, 1668, 1627, 1589, 1544, 1471, 1436, 1406, 1326, 1282, 1251, 1215, 1153,
1076, 1045, 999, 958, 887, 850, 767, 690, 617, 567, 518, 399
1H NMR (DMSO-d6) δ: 10.18 (bs, 1H), 8.43 (s, 2H), 8.27–8.24 (m, 3H), 8.04–8.01 (t, 2H, J = 10.8 Hz), 7.90 (bs,
1H), 7.82–7.79 (t, 1H, J = 7.2 Hz), 7.63–7.60 (t, 1H, J = 7.2 Hz), 7.51–7.40 (m, 3H), 6.95–6.80 (bs, 2H), 5.05 (s,
2H)
13C NMR (DMSO-d6) δ: 157.1, 156.7, 149.1, 139.9, 139.7, 138.5, 136.7, 131.8, 129.2, 128.4, 128.3, 127.3, 126.9, 125.6,
124.2, 114.0, 23.6
MS, m/z: 549 (M+ + 1)
IR, ν˜/cm−1: 3274, 3180, 3120, 2927, 1707, 1645, 1591, 1467, 1409, 1325, 1284, 1253, 1157, 1128, 1101, 1045, 960,
873, 773, 692, 661, 522
1H NMR (DMSO-d6) δ: 9.80 (s, 1H), 8.34–8.32 (d, 2H, J = 8.4 Hz), 8.25 (s, 1H), 8.09–8.07 (d, 1H, J = 8.4 Hz),
8.03–8.01 (d, 1H, J = 8.0 Hz), 7.91 (bs, 2H), 7.83–7.79 (t, 1H, J = 7.2 Hz), 7.66–7.58 (m, 3H), 7.31 (bs, 3H), 6.60
(bs, 2H), 4.89 (s, 2H)
13C NMR (DMSO-d6) δ: 157.8, 157.2, 147.8, 142.0, 137.6, 137.1, 136.5, 134.0, 131.8, 129.3, 129.0, 128.8, 128.7, 128.5,
126.7, 125.6, 124.3, 114.1, 24.2
MS, m/z: 447 (M+ + 1)
IR, ν˜/cm−1: 3321, 3200, 3125, 1712, 1645, 1581, 1525, 1498, 1459, 1406, 1326, 1299, 1276, 1172, 1137, 1043, 958,
856, 770, 696, 523
1H NMR (DMSO-d6) δ: 9.83 (s, 1H), 8.34–8.32 (d, 2H, J = 8.8 Hz), 8.28 (s, 1H), 8.10–8.08 (d, 1H, J = 8.0 Hz),
8.05–8.03 (d, 1H, J = 8.0 Hz), 7.97–7.93 (m, 2H), 7.85–7.81 (t, 1H, J = 8.0 Hz), 7.68–7.64 (t, 1H, J = 8.4 Hz),
7.61–7.57 (m, 2H), 7.14–7.10 (t, 2H, J = 8.8 Hz), 6.62 (bs, 2H), 4.88 (s, 2H)
13C NMR (DMSO-d6) δ: 157.2, 147.8, 141.1, 137.6, 136.5, 134.0, 131.8, 129.2, 129.0, 128.8, 128.5, 125.6, 124.3, 115.5,
115.3, 114.1
MS, m/z: 465 (M+ + 1)
IIIa
IIIb
IR, ν˜/cm−1: 3058, 2962, 2919, 2852, 1491, 1444, 1262, 1095, 1023, 802, 749, 687, 512
1H NMR (CDCl3) δ: 8.30–8.28 (d, 1H, J = 8.4 Hz), 8.08–8.05 (m, 4H), 7.98–7.96 (d, 1H, J = 8.4 Hz), 7.89 (s, 1H),
7.84–7.80 (t, 1H, J = 6.8 Hz), 7.71–7.54 (m, 7H)
13C NMR (CDCl3) δ: 138.4, 131.7, 129.4, 129.2, 128.9, 128.8, 128.8, 128.2, 128.0, 127.8, 125.0, 123.8, 118.0
MS, m/z: 446 (M+ + 1)
IR, ν˜/cm−1: 3059, 2926, 2856, 1729, 1584, 1494, 1446, 1396, 1316, 1259, 1212, 1094, 1024, 881, 804, 743, 688
1H NMR (CDCl3) δ: 8.27–8.25 (d, 1H, J = 8.4 Hz), 8.05–8.03 (d, 2H, J = 7.2 Hz), 7.95–7.91 (t, 3H, J = 9.2 Hz),
7.86 (s, 1H), 7.81–7.77 (t, 1H, J = 7.2 Hz), 7.66–7.56 (m, 4H), 7.44–7.42 (d, 2H, J = 8.0 Hz)
13C NMR (DMSO-d6) δ: 157.8, 157.4, 149.5, 141.7, 140.3, 138.3, 136.4, 131.9, 129.9, 128.2, 128.0, 127.8, 127.3, 125.7,
125.6, 125.2, 124.5, 113.7
MS, m/z: 514 (M+ + 1)
IIIc
IR, ν˜/cm−1: 2919, 2852, 1557, 1489, 1447, 1309, 1270, 1218, 988, 879, 824, 778, 742, 517
1H NMR (CDCl3) δ: 8.18–8.16 (d, 1H, J = 8.4 Hz), 8.05–8.03 (d, 2H, J = 8.0 Hz), 7.93–7.91 (t, 1H, J = 8.4 Hz),
7.84 (s, 1H), 7.79–7.75 (t, 1H, J = 7.6 Hz), 7.65–7.60 (m, 3H), 7.57–7.51 (m, 2H), 7.18–7.14 (m, 2H), 3.88 (s, 3H)
13C NMR (CDCl3) δ: 158.0, 153.7, 151.5, 143.3, 138.6, 136.8, 136.4, 132.7, 131.6, 129.2, 129.0, 128.2, 128.0, 127.9,
125.0, 123.9, 121.1, 120.7, 117.8, 112.4, 56.0
MS, m/z: 510 (M+ + 1)

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K. Prabakaran et al./Chemical Papers 65 (6) 883–889 (2011)
Table 5. (continued)
Compound
Spectral data
IIId
IR, ν˜/cm−1: 3057, 2923, 2853, 1728, 1584, 1494, 1446, 1390, 1316, 1256, 1212, 1094, 1024, 881, 804, 743, 689, 595,
512
1H NMR (CDCl3) δ: 8.27–8.25 (d, 1H, J = 8.4 Hz), 8.19–8.17 (d, 2H, J = 8.0 Hz), 8.04–8.02 (d, 2H, J = 8.4 Hz),
7.97–7.95 (d, 2H, J = 8.0 Hz), 7.89–7.87 (m, 3H), 7.83–7.79 (t, 1H, J = 8.0 Hz), 7.71–7.67 (t, 1H, J = 8.4 Hz),
7.65–7.61 (t, 2H, J = 6.8 Hz), 7.59–7.55 (t, 1H, J = 7.2 Hz)
13C NMR (CDCl3) δ: 158.3, 153.8, 151.5, 143.3, 138.5, 136.8, 136.5, 132.7, 131.6, 129.1, 128.9, 128.3, 127.9, 127.4,
124.9, 123.8, 117.8, 114.3, 22.6
MS, m/z: 582 (M+ + 1)
IIIe
IIIf
IR, ν˜/cm−1: 3058, 2962, 2919, 2852, 1491, 1444, 1262, 1095, 1023, 802, 749, 687, 512
1H NMR (CDCl3) δ: 8.28–8.25 (d, 1H, J = 8.4 Hz), 8.03–7.97 (m, 4H), 7.95–7.93 (d, 1H, J = 8.0 Hz), 7.84 (s, 1H),
7.82–7.78 (t, 1H, J = 6.8 Hz), 7.69–7.65 (t, 1H, J = 7.2 Hz) 7.64–7.59 (m, 4H) 7.55–7.51 (t, 1H, J = 7.6 Hz)
13C NMR (CDCl3) δ: 157.9, 151.1, 150.2, 140.8, 136.9, 136.7, 135.4, 133.3, 131.9, 129.4, 129.4, 129.2, 128.9, 128.2,
127.8, 125.1, 123.9, 117.9
MS, m/z: 479 (M+ + 1)
IR, ν˜/cm−1: 3059, 2966, 2918, 2858, 1490, 1444, 1264, 1095, 1023, 802, 749, 687, 516
1H NMR (CDCl3) δ: 8.27–8.24 (d, 1H, J = 8.4 Hz), 8.01–7.93 (m, 5H), 7.84–7.79 (m, 2H), 7.71–7.67 (t, 1H, J = 7.6
Hz), 7.61–7.58 (d, 2H, J = 8.4 Hz), 7.33–7.29 (t, 2H, J = 8.4 Hz)
13C NMR (CDCl3) δ: 150.8, 150.2, 136.8, 136.7, 135.4, 131.9, 131.3, 131.3, 129.4, 129.2, 128.3, 127.9, 125.0, 123.8,
118.0, 116.0, 115.8
MS, m/z: 497 (M+ + 1)
the formation of semicarbazone derivatives, II, where
Signals due to the aromatic carbons resonate at their
usual positions.
the two characteristic bands at 3200–3400 cm−1 and
1645–1720 cm−1 were assigned to the N—H and C
O
It is worth mentioning that in the present study,
effective cyclization of hydrazones in the presence of
SeO2 can be attributed to the increasing acidity of the
active methylene, which prevents the decomposition of
1,2,3-selenadiazoles into acetylenes and thus ensures
their thermal stability.
—
—
stretching, and the band at 1580–1630 cm−1 due
—
to C N suggested the condensation of different ke-
—
tones, I, and semicarbazide. Symmetric and asymmet-
ric C—H stretching modes of the methylene group
appeared as a shoulder just below 3000 cm−1 in all
semicarbazone derivatives. The appearance of bands
—
—
corresponding to C C and N N also showed the for-
Conclusions
—
—
mation of 1,2,3-selenadiazole rings; also bands corre-
sponding to C—S at 760 cm−1, C—Se—N at 802 cm−1
were observed.
Structures of semicarbazones, II, and selenadia-
zoles, III, were further confirmed by 1H NMR and
13C NMR. In semicarbazone, II, the N—H and NH2
protons appeared as a singlet at δ 9.8–10.1 and a
broad singlet at δ 6.43–6.89, respectively. Structures
of hydrazones, II, were further supported by 13C NMR
A facile method for the synthesis of new selenadia-
zoles containing the isoquinoline ring moiety has been
established. The presented methodology was found to
be efficient in terms of yield and purity.
Acknowledgements. This work was supported in part by
the fund from the Korea Basic Science Institute (KBSI) (No.
C30223) for division of high technology materials research. Also
the author Dr Fazlur-Rahman Nawaz Khan acknowledges KBSI
for providing financial support and facilities.
—
spectra. Disappearance of the ketonic carbon (C O)
—
signal from the starting ketones, I, confirmed the for-
mation of semicarbazone derivatives. The formation
of 1,2,3-selenadiazole rings, III, was also supported
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