The syntheses and crystal structure of novel 5-methyl-3-substituted-1,2,4-triazolo[3,4-b]benzothiazoles

Article abstract of DOI:10.1016/S0022-2860(01)00923-1

Novel 5-methyl-3-substituted-1,2,4-triazolo[3,4-b]benzothiazoles were synthesized from o-methylaniline to 5 with various aromatic carbonic acids. The yielded product 6a-e were confirmed by Elemental Analyses, NMR, MS, IR spectra and 6e was investigated with X-ray crystallography. Compound 6e, C₂₄H₁₆N₄S, Mr = 392.69, crystallized in the triclinic space group P1? with unit cell parameters a = 9.713(3) ?, b = 14.645(4) ?, c = 15.641(3) ?, α = 113.17(2)°, β=90.11(2)°, γ = 109.29(2)°, V = 1908.1(7) ?³, Z = 4, D_m = 1.366 Mgm^-3.

Full text of DOI:10.1016/S0022-2860(01)00923-1

Journal of Molecular Structure 608 @2002) 41±47
www.elsevier.com/locate/molstruc
The syntheses and crystal structure of novel 5-methyl-3-
substituted-1,2,4-triazolo[3,4-b]benzothiazoles
a,
b
Heng-Shan Dong , Bin Quan , Er-Feng Chai , Xue-Rong Mao
b
b
*
aNational Laboratory of Applied Organic Chemistry, Institute of Organic Chemistry, College of Chemistry and Chemical Engineering,
Lanzhou University, Lanzhou, Gansu 730000, People's Republic of China
bDepartment of Chemistry, Guansu Education College, Lanzhou, Gansu 730000, People's Republic of China
Received 1 March 2001; revised 23 October 2001; accepted 23 October 2001
Abstract
Novel 5-methyl-3-substituted-1,2,4-triazolo[3,4-b]benzothiazoles were synthesized from o-methylaniline to 5 with various
aromatic carbonic acids. The yielded product 6a±e were con®rmed by Elemental Analyses, NMR, MS, IR spectra and 6e was
ꢀ
investigated with X-ray crystallography. Compound 6e, C24H16N4S , Mrˆ 392:69; crystallized in the triclinic space group P1
Ê
Ê
Ê
with unit cell parameters a ˆ 9:713ꢀ3† A, b ˆ 14:645ꢀ4† A, c ˆ 15:641ꢀ3† A, a ˆ 113:17ꢀ2†8; b ˆ 90:11ꢀ2†8; g ˆ 109:29ꢀ2†8;
V ˆ 1908:1ꢀ7† A , Z ˆ 4; Dm ˆ 1:366 Mgm23. q 2002 Elsevier Science B.V. All rights reserved.
Keywords: Tricyclazole derivative; Synthesis; 1,2,4-Triazolo[3,4-b]benzothiazole; Crystal structure
Ê 3
1. Introduction
gous compounds are promoted. We have reported the
crystalline structure of 2-@3-bromoanilino)-5-[5-
amino-1-@4-chlorophenyl)-1,2,3-triazol-4-yl]-1,3,4-
thiodiazole and their derivatives [4±7]. We have
obtained the crystalline structure of a new compound
3-[5-methyl-1-@4-methylphenyl)-1,2,3-triazol-4-yl]-
6-@4-methylphenyl)-s-triazolo[3,4-b]-1,3,4-thiadia-
zole. Therefore, it was planned to investigate a
system, which combines these three biologic compo-
nents in a ring to give a compact system for screening
their biologic activities. Recently, we have synthe-
sized several novel 5-methyl-3-substituted-1,2,4-
triazolo[3,4-b]benzothiazoles from o-methylaniline
to 5 with various aromatic carbonic acids. The yielded
products 6a±e were investigated with Elemental
Analyses, NMR, MS, IR techniques and 6e was inves-
tigated with X-ray crystallography. Compound 6e,
C24H16N4S , Mrˆ 392:69; crystallized in the triclinic
Tricyclazole is one of the benzothiazole deriva-
tives, which are well known for developing this synth-
esis of many compounds with this ring system
beading diverse biological activities such as applica-
tion as potent antibacterials [1,2] and fungicides for
the control of Piricularia oryzae in the prevention of
rice blast [3]. The crystal structure of this heterocyclic
system was not found in literature up to now. In recent
years, fused heterocycles have been found to possess
many unique properties in synthesis and pharma-
cology. In particular, s-triazolo[3,4-b]benzothiazole
derivatives are of interest because of their broad
spectra of biological activities. The structure, which
is established, should be yearned for studying relation
between de®nite structure and properties in these
®elds. It should be referenced that studies of analo-
ꢀ
space group P1 with unit cell parameters
Ê
Ê
Ê
a ˆ 9:713ꢀ3† A, b ˆ 14:645ꢀ4† A, c ˆ 15:641ꢀ3† A,
* Corresponding author. Tel.: 186-931-891-582.
0022-2860/02/$ - see front matter q 2002 Elsevier Science B.V. All rights reserved.
PII: S0022-2860@01)00923-1

42
H.-S. Dong et al. / Journal of Molecular Structure 608 42002) 41±47
Scheme 1.
a ˆ 113:17ꢀ2†8; b ˆ 90:11ꢀ2†8; g ˆ 109:29ꢀ2†8;
substituted-1,2,4-triazolo[3,4-b]benzothiazoles 6a±e
show in Table 1.
Ê 3
V ˆ 1908:1ꢀ7† A , Z ˆ 4; Dm ˆ 1:366 Mgm23
.
The synthesis pathway of compound 6 is shown in
Scheme 1 @the syntheses route of compounds 6a±e).
The spectral data of 6a±e presented in Tables 2±4.
IR absorption peaks of 5 at 3167, 3203 cm21 are
assigned to its NHNH2 group. When 5 is converted
6, the NHNH2 perk disappears but a new peak char-
acteristic of nCyN appears at 1588±1626 cm21. Like
the allied system [4]. The nC±S±C absorption peaks of
2. Results and discussion
compound 6a±e are in the region of 693±702 cm21
.
The structure of the title compound is shown in
Fig. 1. The unit cell parameters of the title compound
is shown in Fig. 2. In recent years the synthesis and
characteristics of s-triazolo[3,4-b]1,3,4-thiadiazoles
[8,9] and 7H-s-triazolo[3,4-b]-1,3,4-thiadiazine deri-
vatives [10] have been investigated. These hetero-
cyclic compounds contain 1,2,4-triazole and
benzothiazole rings condensed through a C±N bond.
The substituted groups at the 3 positions cannot conju-
gate with the heterocyclic nucleus giving it new char-
acteristics in a continuation of our earlier studies [4].
We report the syntheses of several novel 5-methyl-3-
1
In H NMR spectra, compared 5 and 6a±e, we
found that after cyclization the evident change is
that the signals of ±NHNH2 protons are at d
3.11 ppm. The chemical shifts of the aromatic methyl
group show in the range of d 2.36±2.52 ppm. The
chemical shifts of the triazole methyl group show in
the range d 2.33±2.75 ppm, and the chemical shift of
the aromatic ring methyl group on the 1,2,4-tria-
zolo[3,4-b]benzothiazole ring in compound 6e occurs
at higher frequency than the other compounds.
Single crystals were selected and were mounted on
Fig. 1. ORTEP drawing of the title compound showing the atom
numbering scheme.
Fig. 2. The unit cell parameters of the title compound.

H.-S. Dong et al. / Journal of Molecular Structure 608 42002) 41±47
43
Table 1
Structures, yields and melting points of the compounds 6a±e @Ar ˆ 6a 5-methyl-1-@4-chlorophenyl)-1,2,3-triazol-4-yl; 6b 5-methyl-1-@4-
methylphenyl)-1,2,3-triazol-4-yl; 6c 5-methyl-1-@2-methylphenyl)-1,2,3-triazol-4-yl; 6d 2,4-dichlorophoxymethylene; 6e 2-phenylquinoline-
4-yl)
Compound
Yield @%)
Mp @8C)
Formula
Found @required) @%)
C
H
N
6a
6b
6c
6d
6e
42
60
67
57
45
252±253
220±221
143±144
125±126
228±229
C18H13ClN6S56.68@56.77)
C19H16N6S63.27@63.31)
C19H16N6S63.23@63.31)
3.40@3.44)
4.42@4.47)
4.46@4.47)
22.27@22.07)
23.43@23.32)
23.45@23.32)
C16H11Cl2N3OS52.68@52.76)
C24H16N4S73.39@73.45)
3.10@3.04)
4.08@4.11)
11.62@11.54)
14.38@14.28)
the tip of a glass ®ber. Preliminary examination and
data collection were performed with Mo Ka radiation
the three CyN bonds ranging from 1.294@4) to
Ê
Ê
1.392@4) A. The benzothiazole ring system is planar.
1.306@4) A and the N±N bond lengths ranging
Ê
@l ˆ 0:71073 A) on an Enraf±Nonius CAD4
Ê
The bond lengths N2±C8 1.373@4) A, N2±C7
computer controlled kappa axis diffractometer oper-
ating in the v/2u scanning mode using the crystal.
The structure was determined by direct methods
@shelxs-86) and re®ned by full covariance matrix
methods @shelxl-93). The crystal data and the re®ne-
ment detail gives in Table 5.
Ê
Ê
Ê
1.422@4) A, S1±C6 1.756@4) A, S1±C8 1.719@3) A
are not in agreement with the values reported for
benzothiazole by Fehlmann [11] @the bond lengths
Ê
Ê
N2±C8 1.297 A, N2±C7 1.381 A, S1±C6 1.739 A,
Ê
Ê
S1±C8 1.763 A). The bond lengths N2±C8 1.297 A
Ê
Ê
[11] and N2±C8 1.373@4) A are between the bond
lengths of CyN and C±N. The structure of the title
The structure of the title compound is shown in Fig.
1. The fractional coordinates and mean temperature
factors with estimated standard deviations for non-
hydrogen atoms are listed in Table 6 and selected
bond lengths are given in Table 7, selected bond
angles are given in Table 8. The geometric calcula-
tions were performed using the program shelxs-86.
The central ring system in the present compound is
already determined. The bond lengths indicate a
degree of delocalization around the ring system with
Table 3
1H NMR spectral data for compounds 6a±e @Bti: benzothiazole;
Tazo: 1,2,3-triazol)
Compound
1H NMR @CDCl3 2 d), d @ppm), J @Hz)
6a
7.14±7.72 @m, 3H, Bti-H), 7.14±7.47 @q or
2d, 4H, J ˆ 8.5, p-ClC6H4±), 2.45 @s,3H,
Bti-CH3), 2.75 @s,3H,Tazo-CH3)
6b
6c
7.13±7.60 @m, 3H, Bti-H), 7.42 @s, 4H, 4-
CH3C6H4), 2.49 @s, 6H, Bti-CH3, Tazo-
CH3), 2.10 @s, 3H, 4-CH3C6H4)
Table 2
IR spectral data for compounds 6a±e
Compound
IR@cm21) @KBr disc)
7.15±7.63 @m, 7H, Bti-H, 2-CH3C6H4), 2.33
@s, 3H, Tazo-CH3), 2.33 @s, 3H, Bti-CH3),
2.14 @s, 3H, 2-CH3C6H4)
6a
3067, 3014, 2919, 2851, 1679, 1551, 1498,
1426, 1369, 1258, 980, 861, 823, 723.5
6d
6e
6.93±7.60 @m, 6H, ±C6H3Cl2, Bti-4H), 4.97
@s,2H, ±OCH2±), 2.58 @s, 3H, Bti-CH3)
6b
6c
6d
6e
3067, 2969, 2922, 2864, 1650, 1558, 1518,
1483, 1383, 971, 862, 798, 722.4
8.35±8.33 @d,1H, J ˆ 8.3, 80-H), 8.25±8.26
@m, 1H, J ˆ 1.5, Bti-8H),8.23 @s, 1H, 50-H),
8.22 @s, 1H, 70-H), 7.79±7.83 @m, 1H,
J ˆ 8.2, J ˆ 1.52, Bti-7H), 7.48±7.58 @m,
5H, Ph-H), 7.31 @s, 1H, 30-H), 7.26±7.27 @d,
1H, J ˆ 1.48, Bti-6H), 6.99±7.01 @d, 1H,
J ˆ 7.63, 60-H), 1.51 @s, 3H, Bti-5CH3)
3077, 2968, 2930, 2864, 1612, 1501, 1481,
1407, 1382, 1259, 971, 861, 807, 722.1
3191, 2918, 1615, 1556, 1480, 1454, 1362,
1291, 1231, 1122, 984, 860, 815, 720.9
3057, 2974, 2917, 1600, 1548, 1481, 1445,
1355, 1240, 956.9, 824, 762, 721.1

44
H.-S. Dong et al. / Journal of Molecular Structure 608 42002) 41±47
Table 4
MSspectral data for compounds 6a±e
Table 5
Crystal data and summary of data collection and structure re®ne-
ment
No
MP
m/z @%)
Compound
C24H16N4S
6a
381@25)
353@6), 326@5), 320@8), 300@1),
292@9), 285@2), 229@4), 285@2),
229@4), 194@6), 191@29),
181@11), 175@15), 163@20),
154@23), 153@32), 152@62),
149@34), 146@10), 139@5),
136@23), 128@15), 123@10),
121@22), 119@6), 113@33),
111@100), 109@19), 102@16),
101@11), 92@13), 91@7), 77@23),
75@59), 51@13)
Color/Shape
Colorless/rhombic pillared
392.47
20 @293 K)
Formula weight
Temperature @8C)
Crystal system
Space group
Triclinic
ꢀ
P1
Cell constants
Ê
a @A)
9.713@3)
14.645@4)
15.641@8)
113.17@2)
90.11@2)
109.29@2)
1908.1@7)
4
Ê
b @A)
Ê
c @A)
a @8)
b @8)
g @8)
6b
360@22)
345@54), 332@17), 331@22),
318@22), 317@100), 303@9),
290@10), 289@14), 274@2),
263@4), 247@2), 214@2), 200@7),
197@4), 190@2), 184@3), 171@5),
170@29), 169@49), 163@22),
162@16), 156@19), 155@11),
143@31), 136@18), 132@34),
128@13), 122@11), 121@14),
119@9), 102@10), 91@75), 77@19),
65@50)
Ê 3
Volume @A )
Formula units/units cell
Dcalc @g cm23
)
1.366
F@000)
816
Absorption coef®cient @mm21
Diffractometer/scan Enraf±
Nonius CAD4
)
0.188
v/2?
Radiation, graphite
0.71073
monochromator Mo Ka
Re¯ections for cell measurement
and u range @8)
Index ranges
25, 0 , 25
6c
360@17)
345@49), 332@12), 331@16),
318@22), 317@100), 303@8),
290@8), 289@13), 276@2), 274@2),
263@3), 256@2), 247@2), 214@2),
200@7), 197@4), 190@1), 184@2),
171@4), 170@25), 169@48),
163@23), 162@21), 156@15),
143@27), 136@18), 132@22),
128@15), 121@17), 117@13),
109@10), 102@12), 91@80),
89@23), 77@25), 65@77)
0 # h # 11; 217 # k # 16;
218 # l # 18
7149
Standard re¯ections
Re¯ections measured
Re¯ection observed ‰1 . 2sꢀI†Š
Maximum value of u @8)
Computing
6714
4237 @Rint ˆ 0.0322)
25.02
Data collection CAD4
Cell re®nement CAD4
Data reduction PCSDP
Structure solution shelxs-86
shelxl-93
Structure re®nement
Data/restrains/parameters
Goodness-of-®t on F2
Final R indices
6d
363@4)
328@1), 240@17), 239@6),
238@47), 223@1), 203@15),
202@100), 184@2), 177@27),
173@8), 163@9), 161@26),
150@12), 148@8), 136@8), 133@7),
121@7), 117@13), 109@8), 103@3),
92@5), 77@6), 65@5)
6649/0/523
1.134
R1 ˆ 0.0514, wR2 ˆ 0.1364
Ê 23
Largest diff. peak and hole
0.369 and 20.391 eA
compound is shown in Scheme 2 @the structure of 5-
methyl-3-@2-phenylquinoline-4-yl)-1,2,4-triazolo
[3,4-b]benzothiazole 6e).
6e
392@70)
378@27), 377@100), 364@10),
359@1), 334@1), 317@2), 315@24),
289@3), 256@2), 231@17),
230@73), 229@98), 204@9),
203@10), 196@16), 189@1),
176@6), 175@5), 162@53),
161@55), 151@14), 147@9),
136@15), 135@27), 126@5),
122@7), 121@12), 118@24),
110@12), 109@12), 92@17),
91@13), 77@20, 65@12)
3. Experimental
Melting points were determined on a Ko¯er
melting point apparatus and are uncorrected. The
mass spectrum was performed on a HP-5988A

H.-S. Dong et al. / Journal of Molecular Structure 608 42002) 41±47
45
chlorobenzene @130 ml) was heated. After o-toluidine
was dissolved, concentrated hydrochloride @21 ml,
0.25 mol) was dripped and a white precipitate was
obtained. Powdered potassium thiocyanate @26 g,
0.26 mol) was poured rapidly into the mixture and
re¯uxed for 16 h and then allowed to cool. The solid
was crushed, collected, and washed with water. The o-
tolylthiourea was recrystallized from aqueous alcohol,
yielded 30.4 g @78.3%), mp 155±156 8C @Lit. mp
155±156 8C [12]).
Table 6
The fractional coordinates and mean temperature factors with esti-
mated standard deviations for non-hydrogen atoms
X
Y
Z
U
S1
0.31523@10)
0.5804@3)
0.3749@3)
0.6140@3)
0.5497@3)
0.1623@4)
0.1218@4)
0.60184@7) 0.95148@7) 0.0647@3)
N1
N2
0.5688@2)
0.4377@2)
0.4810@2)
0.1107@2)
0.2240@3)
0.3130@3)
0.3061@4)
0.3864@4)
0.4779@4)
0.4871@3)
0.4060@3)
0.5398@2)
0.4034@2)
0.2982@2)
0.2124@2)
0.2149@3)
0.1294@3)
0.0381@3)
0.0332@3)
0.1197@3)
0.2869@3)
0.1911@2)
0.1808@3)
0.0974@3)
0.0927@4)
0.1685@4)
0.2492@4)
0.2552@3)
0.9294@2)
0.8413@2)
0.8721@2)
0.6564@2)
0.6770@3)
0.7449@3)
0.7380@3)
0.7954@4)
0.8634@3)
0.8719@3)
0.8157@2)
0.9094@2)
0.8212@2)
0.7604@2)
0.7881@2)
0.8660@3)
0.8880@3)
0.8331@3)
0.7581@3)
0.7324@2)
0.6829@2)
0.6315@2)
0.5511@2)
0.5146@3)
0.4463@3)
0.4115@3)
0.4444@3)
0.5133@3)
0.0616@7)
0.0462@6)
0.0609@7)
0.0552@7)
0.0734@11)
0.0610@9)
0.0830@12)
0.0954@15)
0.0834@12)
0.0609@9)
0.0518@7)
0.0539@8)
0.0486@7)
0.0490@7)
0.0512@7)
0.0604@8)
0.0780@11)
0.0836@12)
0.0708@10)
0.0540@8)
0.0506@7)
0.0483@7)
0.0537@8)
0.0697@10)
0.0855@13)
0.0875@13)
0.0813@11)
0.0666@9)
N3
N4
C1
C2
C3
20.0241@4)
20.0689@5)
0.0269@4)
0.1737@4)
0.2203@3)
0.4389@3)
0.4931@3)
0.4974@3)
0.4486@3)
0.3757@4)
0.3333@5)
0.3634@5)
0.4341@4)
0.4785@3)
0.5662@3)
0.5912@3)
0.6750@3)
0.7266@4)
0.8168@5)
0.8540@5)
0.7991@5)
0.7105@4)
3.2. The preparation of the 2-amino-4-
methylbenzothiazole 4
C4
C5
C6
A solution of bromine @6.8 ml, 0.17 mol) in chloro-
form @50 ml) was poured into a mixture of the dry
powdered o-tolylthiourea @20 g, 0.13 mol) and chloro-
form @60 ml) which was heated to boil contained in a
3-necked ¯ask. Heat was evolved and the mixture
rapidly gave a clear solution which was kept below
30 8C by external cooling. When the initial reaction
had subsided the ¯ask was ®tted with a stirrer and
condenser carrying a calcium chloride tube and the
mixture re¯uxed until evolution of hydrogen bromide
ceased @ca. 24 h), the hydrobromide of the 2-amino-4-
methylbenzothiazole crystallizing out meanwhile.
The mixture was set aside overnight. The cold mixture
was ®ltered and the insoluble residue suspended in
water and treated with sodium sul®te until traces of
free bromine had been removed. The mixture was
again ®ltered. The precipitate was collected, washed
with water, and dried @average yield, 22.5 g, 76.2%)
C7
C8
C9
C10
C11
C12
C13
C14
C15
C16
C17
C18
C19
C20
C21
C22
C23
C24
spectrometer @EI at 70 eV). IR spectra were obtained
in KBr discs using a Nicolet 170SX FT-IR spectro-
meter.1H NMR spectroscopy were recorded at room
temperature at 400.13 MHz on a Bruker AM 400
instrument. Elemental Analyses were carried out on
a Yanaco CHN Corder MT-3 analyzer.
1
mp 253±254 8C @Lit. 254 8C [12]), H NMR @DMSO-
d6) d ˆ 14.27 @s,1H), 11.52 @s, 2H), 7.25±7.37 @m,
3H), 2.67 @s, 3H).
3.3. 2-Hydrazino-4-methylbenzothiazole 5
Phosphorus oxychloride was redistilled @bp
105 8C).
2-Amino-4-methylbenzothiazole @20 g, 0.82 mol)
and hydrazine hydrate 85% @0.11 mol) in 50 ml of
glycol re¯uxed @110±120 8C) while stirring for
4 h. The color of the reaction mixture changed
to green, and gave a homogeneous solution. A
white solid was precipitated at the end of the
re¯ux period. The mixture was cooled and the
product was ®ltered, washed with water, air-dried
and recrystallized from ethanol to give white
needles of 5. It gave 11 g @75.3%), mp 169±170 8C.
5-Methyl-1-@4-methylphenyl)-1,2,3-triazol-4-
carboxylic acid, 5-Methyl-1-@2-methylphenyl)-1,2,3-
triazol-4-carboxylic acid and 5-Methyl-1-@4-cholo-
phenyl)-1,2,3-triazol-4-carboxylic acid were prepared
by the literature [9].
3.1. The preparation of the o-tolylthiourea 3
A mixture of o-toluidine @25.4 g, 0.24 mol) and

46
H.-S. Dong et al. / Journal of Molecular Structure 608 42002) 41±47
Table 7
Selected bond lengths @A)
Ê
S1C8
S1C6
N1C8
N1N3
N2C8
N2C9
N2C7
N3C9
N4C18
1.719@3)
1.756@4)
1.294@4)
1.392@4)
1.373@4)
1.389@4)
1.422@4)
1.306@4)
1.324@4)
N4C16
C1C2
C2C3
C2C7
C3C4
C4C5
C5C6
C6C7
C9C10
1.360@4)
1.495@5)
1.388@5)
1.394@5)
1.373@6)
1.357@6)
1.388@5)
1.387@5)
1.473@4)
C10C17
C10C11
C11C12
C11C16
C12C13
C13C14
C14C15
C15C16
C17C18
1.365@4)
1.424@4)
1.405@5)
1.420@5)
1.362@5)
1.402@6)
1.350@6)
1.412@5)
1.418@4)
C18C19
C19C24
C19C20
C20C21
C21C22
C22C23
C23C24
1.483@5)
1.384@5)
1.388@5)
1.379@6)
1.367@6)
1.373@6)
1.374@5)
Table 8
Selected bond angles @8)
C8S1C6
C8N1N3
C8N2C9
C8N2C7
C9N2C7
C9N3N1
C18N4C16
C3C2C7
C3C2C1
C7C2C1
C4C3C2
C5C4C3
C4C5C6
88.7@2)
C5C6C7
C5C6S1
C7C6S1
C6C7C2
C6C7N2
C2C7N2
N1C8N2
N1C8S1
N2C8S1
N3C9N2
N3C9C10
N2C9C10
C17C10C11
121.9@3)
123.4@3)
114.6@2)
121.1@3)
109.1@3)
129.8@3)
112.9@3)
133.3@3)
113.8@2)
108.9@3)
120.2@3)
130.7@3)
119.5@3)
C17C10C9
C11C10C9
C12C11C10
C12C11C16
C10C11C16
C13C12C11
C12C13C14
C15C14C13
C14C15C16
N4C16C15
N4C16C11
C15C16C11
C10C17C18
119.3@3)
120.7@3)
124.3@3)
119.3@3)
116.4@3)
120.6@4)
120.0@4)
121.0@4)
120.7@4)
118.3@3)
123.3@3)
118.4@3)
120.1@3)
N4C18C17
N4C18C19
C17C18C19
C24C19C20
C24C19C18
C20C19C18
C21C20C19
C22C21C20
C21C22C23
C22C23C24
C23C24C19
121.8@3)
117.4@3)
120.6@3)
117.9@3)
122.0@3)
119.9@3)
120.5@4)
120.7@4)
119.3@4)
120.3@4)
121.1@4)
105.1@3)
103.4@2)
113.7@3)
142.9@3)
109.6@3)
118.8@3)
115.7@3)
119.1@3)
125.3@3)
122.5@4)
122.1@4)
116.7@4)
1H NMR @CDCl3) d ˆ 6.93±7.57 @m, 3H), 4.96
the remaining reaction mixture poured into ice-
water. The solution was basifyed by adding potas-
sium hydroxide solution, the deposited solid was
®ltered off and recrystallized from ethanol to give
the title 5-methyl-3-substituted-1,2,4-triazolo[3,4-
b]benzothiazoles 6a±e. The solid was separated
by chromatographic column @silica gel, eluant
ethyl acetate/petroleum ether 1:1). The results are
given in Table 1.
@broad, 3H), 2.58 @s, 3H).
3.4. Novel 5-methyl-3-substituted-1,2,4-triazolo[3,4-
b]benzothiazoles 6a±e
A mixture of 2-hydrazino-4-methylbenzothiazole
@1 mmol), various aromatic carbonic acids
5
@1 mmol) and POCl3 @5 ml) was heated under re¯ux
for 12 h. A portion of POCl3 was distilled out and
The puri®ed product was dissolved in ethyl acetate/
petroleum ether/ethanol solution. The crystal was
obtained after 7 days by evaporation of the solution.
Acknowledgements
The authors with to acknowledge that this project is
supported by University Key Teacher by the Ministry
of Education, NNSFC@chuangxin qunti,2002-001),
Gansu NSFC@ZS991-A25-003-Z) and Lanzhou
University NLAOC.
Scheme 2.

H.-S. Dong et al. / Journal of Molecular Structure 608 42002) 41±47
47
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