A Simple One-pot Three-component Synthesis of Dihydrobenzo[4,5]imidazo[2,1-b]thiazol-3-ols by Reaction of Acyl Chlorides, Isocyanides, and 2-Mercaptobenzimidazoles

Article abstract of DOI:10.1002/jhet.3335

The reactive imidoyl chloride adducts generated in situ from the reaction of isocyanide and acyl chlorides were trapped by 2-mercaptobenzimidazole to yield highly functionalized dihydrobenzo[4,5]imidazo[2,1-b]thiazoles in excellent yields.

Full text of DOI:10.1002/jhet.3335

Month 2018
A Simple One-pot Three-component Synthesis of Dihydrobenzo[4,5]
imidazo[2,1-b]thiazol-3-ols by Reaction of Acyl Chlorides, Isocyanides,
and 2-Mercaptobenzimidazoles
*
Mahdiyeh Talebizadeh, Mohammad Anary-Abbasinejad, and Ali Darehkordi
Department of Chemistry, Faculty of Science, Vali-e-Asr University of Rafsanjan, Rafsanjan 77176, Iran
*E-mail: adarehkordi@yahoo.com; darehkordi@mail.vru.ac.ir
Received May 2, 2018
DOI 10.1002/jhet.3335
Published online 00 Month 2018 in Wiley Online Library (wileyonlinelibrary.com).
The reactive imidoyl chloride adducts generated in situ from the reaction of isocyanide and acyl chlorides
were trapped by 2-mercaptobenzimidazole to yield highly functionalized dihydrobenzo[4,5]imidazo[2,1-b]
thiazoles in excellent yields.
J. Heterocyclic Chem., 00, 00 (2018).
INTRODUCTION
Previous studies have also showed that some molecules
like tricyclic benzimidazole derivatives had anti-HIV
activity, which had led to the discovery of 1H,3H-
thiazolo[3,4-a]benzimidazoles [4].
The literature describes several methods of synthesis of
thiazolo benzimidazoles and their potential biological
activities [17,18]. Therefore, the development of more
and novel effective thiazolo[3,4-a] benzimidazoles is a
pharmacological interest.
On the basis of the aforementioned facts and our interest
in heterocyclic chemistry, and various imidoyl chlorides
reactions, and in order to synthesize bioactive heterocyclic
compounds in this project, we decided to synthesize
a new series of dihydrobenzo[4,5]imidazo[2,1-b]thiazol-
3-ols using N,S-bidentate nucleophides such as 2-
mercaptobenzimidazole and imidoyl chlorides, which are
prepared from a reaction of simple aromatic and aliphatic
acyl chlorides with isocyanides without separation and
purification (in situ).
The benzimidazole nucleus is one of the bioactive
heterocyclic compounds that exhibit a range of biological
activities [1]. Specifically, this nucleus is a constituent of
the vitamin B12 [2].
Also 2-mercaptobenzimidazoles are convenient
precursors that have been extensively utilized in the
synthesis of compounds containing S–C bonds [3].
Recently, many studies have been focused on the design
and synthesis of thiazolo imidazole derivatives, because of
their highly significant bioactivities. These compounds
have been reported to possess a wide spectrum of
biologic activities [4].
Many reactions were developed in the last decades
for which the reactivity of 2-mercaptobenzimidazole
towards diverse reagents was utilized for the synthesis of
nitrogen-bridged and sulfur-bridged heterocycles. From
the point of view for biological activities, benzimidazole
derivatives are useful intermediates and subunits for the
development of molecules having pharmaceutical or
biological interests [4–6].
RESULTS AND DISCUSSION
Imidazo[2,1-b]thiazoles and their derivatives have
attracted more and more research interest since its
synthetic utility and occupy a prominent place in medicinal
chemistry because of their therapeutic properties. The
imidazo[2,1-b]thiazole derivatives have emerged as an
important target molecules owing to their therapeutic and
pharmacological properties such as antibacterial [7],
antifungal [8], antihelmintic [9,10], and antitumor [11–15]
agents. Also compounds containing this heterocyclic
system have been reported as potential acetylcholinesterase
and butyrylcholinesterase inhibitors [16].
The reaction of isocyanides with acyl chlorides produced
reactive imidoyl chlorides, which have been used for
the synthesis of a wide variety of organic compounds.
They are starting materials or key intermediates in the
preparation of heterocyclic compounds and fused
analogues [19,20].
The ketoimidoyl chloride adduct 3, obtained from the
reaction of cyclohexyl isocyanide 1 with acyl chlorides 2,
was reacted with 2-mercaptobenzimidazoles
4
at
room temperature to give dihydrobenzo[4,5]imidazo[2,1-
© 2018 Wiley Periodicals, Inc.

M. Talebizadeh, M. Anary-Abbasinejad, and A. Darehkordi
Vol 000
Table 1
Reaction of imidoyl chlorides with 2-mercaptobenzimidazole.
Entry
R
Product
Melting point (°C)
145–147
Yielda (%)
90
5a
C6H5
5b
4-NO2C6H4
188–190
98
5c
4-BrC6H4
190–192
96
5d
4-pyridine
191–193
96
5e
3-NO2C6H4
189–191
97
(Continues)
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Table 1
(Continued)
Entry
R
Product
Melting point (°C)
Yielda (%)
96
5f
3-FC6H4
184–185
5g
5h
5i
CH3
167–169
180–182
168–169
95
98
98
CH2Cl
2,4-(NO2)2C6H3
aIsolated yields.
b]thiazoles
5
in excellent yields. The results are
The structures of compounds 5a–i were confirmed by
summarized in Table 1. As shown, the reaction was
compatible with different aromatic and aliphatic acyl
chlorides. Although both electron-donating and electron-
withdrawing groups on the acyl chloride resulted in
excellent yields, when electron-poor acyl chlorides were
used, the related dihydrobenzo[4,5]imidazo[2,1-b]thiazol-
3-ol was obtained in higher yields.
the analytical and NMR and IR spectral data. For
example, the H-NMR spectrum of 5d exhibited a singlet
1
at δ = 8.76 due to the OH proton, doublet at δ = 8.62,
3
3JHH = 5.0 Hz, doublet at δ = 7.65, JHH = 8.0 Hz,
3
doublet at δ = 7.49, JHH = 5.0 Hz, triplet at δ = 7.22,
3
3JHH = 7.1 Hz, triplet at δ = 7.10, JHH = 7.1 Hz, and
3
doublet at δ = 6.95, JHH = 8.0 Hz for aromatic
Journal of Heterocyclic Chemistry
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M. Talebizadeh, M. Anary-Abbasinejad, and A. Darehkordi
Vol 000
Scheme 1. A possible mechanism for the synthesis of dihydrobenzo[4,5]
imidazo[2,1-b]thiazol-3-ol.
hydrogens. The multiplet signals are at 1.19–1.76 and at
3.05–3.09 ppm for the cyclohexyl ring. The 1H
decoupled 13C-NMR spectrum of 5d showed 16 distinct
resonances in agreement with the suggested structure,
with the sulfide (C–S) and imine carbons resonating at
150.60 and 161.16 ppm, respectively.
The 1H decoupled 13C-NMR spectrum of 5d showed 16
distinct resonances in agreement with the suggested
structure, with the sulfide (C–S) and imine carbons
resonating at 150.60 and 161.16 ppm, respectively. The
structure of compound 5f was finally unambiguously
confirmed by X-ray crystallographic analysis (Fig. 1).
Mechanistically, the formation of dihydrobenzo[4,5]
imidazo[2,1-b]thiazoles 5 can be rationalized by initial
formation of the ketoimidoyl chloride adduct 3 from
reaction of cyclohexyl isocyanide 1 with acyl chlorides
Scheme 2. Synthesis of 1H-benzo[d]imidazol-2-yl-N-cyclohexyl-2-oxo-
2-phenylethanimidothioate.
2. Then, the intermediate
3 is attacked by 2-
mercaptobenzimidazole 4 to form the intermediate 6,
which then undergoes an intramolecular cyclization
reaction to afford product 5 (Scheme 1).
In the aforementioned reaction, when the utilized acyl
chloride was not electron poor, the cyclization step did
not progress and the intermediate 6 was isolated.
Thus, the reaction of 4-fluorobenzoyl chloride and 4-
methylbenzoyl chloride with cyclohexyl isocyanide, and
2-mercaptobenzimidazole led to 1H-benzo[d]imidazol-2-yl-
N-cyclohexyl-2-oxo-2-phenylethanimidothioate compounds
6a and 6b in high yields (Scheme 2). The structures 6a
and 6b were easily distinguished from compounds 5 by
observing the signal related to the carbonyl group at about
190 ppm in 13C-NMR spectra.
products were characterized by the IR, 1H-NMR, 13C-
NMR, and elemental analysis, further confirmed by single-
crystal X-ray diffraction determination of compound
5f (Fig. 1). Crystallographic data for the structure of
5f reported in this paper have been deposited at the
Cambridge Crystallographic Data Centre as supplementary
publication with CCDC No. 1476856. Structural
parameters for 5f: data collection; crystal size:
0.30 × 0.10 × 0.08 mm3; C21H20FN3OS, Mr = 381.47,
It is worth mentioning that all of the 2,3-
dihydrobenzo[4,5]imidazo[2,1-b]thiazol-3-ol derivatives
synthesized by this method were isolated by easily
washing the isolated precipitate with diethyl ether. The
Figure 1. The ORTEP diagram of 5f. [Color figure can be viewed at wileyonlinelibrary.com]
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Synthesis of Dihydrobenzo[4,5]imidazo[2,1-b]thiazol-3-ols
orthorhombic system, space group P212121, a = 8.3242
(17), b = 12.107 (2), c = 20.597 (4) Å; V = 2075.8 (7) Å3,
Z = 4.
7.25 (1H, m, HAr), 7.37–7.38 (3H, HAr), 7.46–7.48 (2H,
m, HAr). 8.81 (1H, s, OH). 13C-NMR (100 MHz,
DMSO-d6) δ: 24.15, 24.39, 25.36, 31.80, 32.41, 69.28
(C–N-cyclo), 91.47 (C–OH), 112.04, 115.39, 116.22,
124.21, 124.29, 125.66, 128.66, 129.39, 130.24, 131.65,
CONCLUSIONS
138.24 (C–S), 151.14 (C–N-cyclo).
3-(4-Nitrophenyl)-2-(phenylimino)-2,3-dihydrobenzo[4,5]
imidazo[2,1-b]thiazol-3-ol (5b). Yellow crystals, mp: 188–
In summary, the reaction of ketoimidoyl chlorides
with 2-mercaptobenzimidazoles provides a facile and
efficient route for synthesis of dihydrobenzo[4,5]
imidazo[2,1-b]thiazol-3-ol derivatives in excellent yields.
The advantages of this method are simply available
starting materials, neutral and easy reaction condition,
and also very simple purification method.
190°C. Yield: 98%. IR (KBr) (υmax, cmÀ1): 3072 (OH),
1670 (C═N). Elemental analysis: Calcd. for
(C21H20N4O3S): C, 61.74; H, 4.92; N, 13.72%. Found:
C, 61.51; H, 4.67; N, 13.75%. 1H-NMR (400 MHz,
DMSO-d6): δ: 1.22–1.77 (10H, m, 5CH2 of cyclohexyl),
3
3.05–3.1 (1H, m, CHN), 6.94 (1H, d, JHH = 8.1 Hz,
3
HAr), 7.09 (1H, t, JHH = 8.1 Hz, HAr), 7.22 (1H, t,
3JHH = 8.1 Hz, HAr), 7.69 (3H, m), 8.26 (2H, d,
3JHH = 8.1 Hz, HAr), 8.8 (1H, s, OH). 13C-NMR
(100 MHz, DMSO-d6): δ: 23.92, 24.01, 25.39, 32.25,
32.36, 68.14 (C–N-cyclo), 89.59 (C–OH), 110.63,
119.38, 123.11, 123.21, 124.25, 127.18, 131.17, 146.58
EXPERIMENTAL
All of the chemicals and solvents were purchased from
commercial sources and used without further purification
unless otherwise stated. Melting points were determined on
a Melt-Temp II melting point apparatus (Merck, Tehran,
Iran) and are uncorrected. Elemental analyses were
performed at analytical laboratory of Islamic Azad
University, Yazd Branch, using a Costech ECS 4010
CHNS–O analyzer. IR spectra were obtained on a Mattson
1000 Fourier transform IR spectrometer. Peaks are reported
in wave numbers (cmÀ1). All of the NMR spectra were
recorded on a Bruker model DRX-400 Avance (1H, 400;
13C, 100) NMR spectrometer (Bruker Corporation, Billerica,
MA). Chemical shifts of 1H-NMR and 13C-NMR are
reported in parts per million (ppm) from tetramethylsilane as
an internal standard in DMSO-d6 or CDCl3 as a solvent.
147.08, 148.24, 150.43 (C–S), 163.31 (C–N-cyclo).
3-(4-Bromophenyl)-2-(phenylimino)-2,3-dihydrobenzo[4,5]
imidazo[2,1-b]thiazol-3-ol (5c).
Colorless crystals, mp:
190–192°C. Yield: 96%. IR (KBr) ( υ max, cmÀ1): 3422
(OH), 1668 (C═N). Elemental analysis: Calcd. for
(C21H20BrN3OS): C, 57.02; H, 4.56; N, 9.50%. Found:
C, 57.13; H, 4.46; N, 9.38%. 1H-NMR (400 MHz,
DMSO-d6): δ: 1.20–1.75 (10H, m, 5CH2 of cyclohexyl),
3.06–3.09 (1H, broad, CHN), 6.96–7.25 (3H, m, HAr),
3
7.32 (2H, d, JHH = 8.0 Hz, HAr), 7.58–7.60 (3H, m,
HAr), 8.57 (1H, s, OH). 13C-NMR (100 MHz,
DMSO-d6): δ: 23.97, 24.04, 25.42, 32.11, 32.40, 68.06
(C–N-cyclo), 89.97 (C–OH), 110.74, 119.25, 122.76,
122.94, 123.03, 128.41, 131.92, 139.35, 147.05, 150.30
General procedure for the synthesis of compounds 5a–i.
In a typical experimental procedure, a dry, two-necked, 50-
mL round-bottom flask was charged with 1.0 mmol of acyl
chloride derivatives and 1.0 mmol of cyclohexyl
isocyanide and was heated at 60°C for 1 h. Then a
mixture of 2-mercaptobenzothiazole (1.0 mmol) and
K2CO3 (1.0 mmol) in tetrahydrofuran (10 mL) was
added. The reaction mixture was stirred at room
temperature for 5 h and then was filtered. After removing
the solvent under reduced pressure, the crude product
was purified by washing with diethyl ether. The products
may be further purified by crystallization from absolute
(C–S), 161.52 (C═N-cyclo).
2-(Phenylimino)-3-(pyridin-4-yl)-2,3-dihydrobenzo[4,5]
imidazo[2,1-b]thiazol-3-ol (5d).
Colorless crystals, mp:
191–193°C. Yield: 96%. IR (KBr) ( υ max, cmÀ1): 3422
(OH), 1673 (C═N). Elemental analysis: Calcd. for
(C20H20N4OS): C, 65.91; H, 5.53; N, 15.37%. Found: C,
65.78; H, 5.40; N, 15.52%. 1H-NMR (400 MHz,
DMSO-d6): δ: 1.19–1.76 (10H, m, 5CH2 of cyclohexyl),
3
3.05–3.09 (1H, m, CHN), 6.95 (1H, d, JHH = 8.0 Hz,
3
HAr), 7.10 (1H, t, JHH = 7.1 Hz, HAr), 7.22 (1H, t,
3JHH = 7.1 Hz, HAr), 7.49 (2H, d, JHH = 5.0 Hz, HAr),
3
3
7.65 (1H, d, JHH = 8.0 Hz, HAr), 8.62 (2H, d,
3JHH = 5.0 Hz, HAr), 8.76 (1H, s, OH). 13C-NMR
(100 MHz, DMSO-d6): δ: 23.91, 23.99, 25.40, 32.25,
32.36, 68.07 (C–N-cyclo), 89.36 (C–OH), 110.62,
119.36, 120.98, 123.07, 123.17, 131.75, 147.05, 148.32,
ethanol.
3-Phenyl-2-(phenylimino)-2,3-dihydrobenzo[4,5]
imidazo[2,1-b]thiazol-3-ol (5a).
Colorless crystals, mp:
145–147°C. Yield: 90%. IR (KBr) ( υ max, cmÀ1): 3060
¯
(OH), 1671 (C═N). Elemental analysis: Calcd. for
(C21H21N3OS): C, 69.39; H, 5.82; N, 11.56%. Found: C,
69.44; H, 5.71; N, 11.43%. 1H-NMR (400 MHz,
DMSO-d6): δ: 1.30–2.05 (10H, m, 5CH2 of cyclohexyl),
2.91 (1H, brond, CHN), 7.15–7.17 (3H, m, HAr), 7.23–
150.51, 150.60 (C–S), 161.16 (C═N-cyclo).
3-(3-Nitrophenyl)-2-(phenylimino)-2,3-dihydrobenzo[4,5]
imidazo[2,1-b]thiazol-3-ol (5e).
Colorless crystals, mp:
189–191°C. Yield: 97%. IR (KBr) ( υ max, cmÀ1): 3088
(OH), 1674 (C═N). Calcd. for (C21H20N4O3S): C, 61.75;
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M. Talebizadeh, M. Anary-Abbasinejad, and A. Darehkordi
Vol 000
H, 4.94; N, 13.72%. Found: C, 61.73; H, 4.96; N, 13.70%.
1H-NMR (400 MHz, DMSO-d6): δ: 1.10–1.76 (10H, m,
5CH2 of cyclohexyl), 3.08–3.09 (1H, m, CHN), 6.96
(1H, m), 7.06 (1H, m, HAr), 7.20–7.24 (1H, m, HAr),
7.64–7.67 (3H, m, HAr), 8.26–8.29 (1H, m, HAr), 8.40
Calcd. for (C21H19N5O5S): C, 55.62; H, 4.22, N, 15.44%.
Found: C, 55.55; H, 4.35, N, 15.24%. 1H-NMR
(400 MHz, DMSO-d6): δ: 1.22–1.77 (10H, m, 5CH2 of
cyclohexyl), 3.03–3.12 (1H, m, CHN), 7.03–7.15 (3H, m,
3
HAr), 7.24 (1H, m, HAr), 7.68 (1H, d, JHH = 8.0 Hz,
2
3
(1H, t, JHH = 2 Hz, HAr), 8.85 (1H, s, OH). 13C-NMR
HAr), 8.36 (1H, d, JHH = 8.0 Hz, HAr), 8.56 (1H, S,
(100 MHz DMSO-d6): δ: 23.88, 23.99, 25.39, 32.04,
32.33, 68.03 (C–N-cyclo), 89.44 (C–OH), 110.70,
119.38, 121.12, 123.13, 123.23, 124.52, 135.92, 131.72,
132.73, 142.00, 147.09, 148.29, 150.52 (C–S), 161.38
(C═N-cyclo).
3-(3-Fluorophenyl)-2-(phenylimino)-2,3-dihydrobenzo[4,5]
HAr), 9.17 (1H, s, OH).
1H-Benzo[d]imidazol-2-yl(Z)-N-cyclohexyl-2-(4-
fluorophenyl)-2-oxoethanimidothioate
(6a).
Colorless
crystals, mp: 155–156°C. Yield: 95%. IR (KBr) ( υ max
,
cmÀ1): 1673 and 1614 (C═O and C═N). Elemental
analysis: Calcd. for (C21H20FN3OS): C, 66.12; H, 5.28;
N, 11.02%. Found: C, 66.15; H, 5.41; N, 10.88%. H-
1
imidazo[2,1-b]thiazol-3-ol (5f).
Colorless crystals, mp:
184–185°C. Yield: 96%. IR (KBr) ( υ max, cmÀ1): 3059
(OH), 1669 (C═N). Elemental analysis: Calcd. for
(C21H20FN3OS): C, 66.12; H, 5.28; N, 11.02%. Found:
C, 66.01; H, 5.35; N, 11.19%. 1H-NMR (400 MHz,
DMSO-d6): δ: 1.20–1.70 (10H, m, 5CH2 cyclohexyl),
2.41 (3H, S, CH3), 3.04–3.09 (1H, m, CHN), 6.97 (1H,
NMR (400 MHz, DMSO-d6): δ: 1.15–1.84 (10 H, m, 5
CH2 of cyclohexyl), 3.73–3.76 (1H, m, CHN), 7.43 (2H,
3
3
t, JHH = 8.0 Hz, HAr), 7.60 (2H, dd, JHF = 9.1 Hz,
3
3JHH = 3.6 Hz, HAr), 7.48 (2H, dd, JHF = 9.1 Hz,
3JHH = 3.6 Hz, HAr), 7.89 (2H, m, HAr), 9.64 (1H, s,
NH). 13C-NMR (100 MHz, DMSO-d6): δ: 24.98, 25.51,
32.48, 48.23, 114.93, 116.59, 126.6, 130.21 (d,
3
3
d, JHH = 8.1 Hz, HAr), 7.05 (1H, d, JHH = 8.1 Hz,
HAr), 7.19–7.25 (2H, m, HAr), 7.29–7.33 (1H, m, HAr),
3
4JCF = 3.1 Hz), 133.28 (d, JCF = 9.0 Hz), 140.164 (C–
3
2
7.38–7.44 (1H, m, HAr), 7.64 (1H, d, JHF = 8.1 Hz,
S), 164.47 (C═N, cyclo), 164.89 (d, JCF = 41.0 Hz),
1
HAr), 7.99 (1H, m, HAr), 8.83 (1H, s, OH).
3-Methyl-2-(phenylimino)-2,3-dihydrobenzo[4,5]
166.41 (d, JCF = 280.1 Hz), 189.5 (C═O).
1H-Benzo[d]imidazol-2-yl(Z)-N-cyclohexyl-2-oxo-2-(p-tolyl)
imidazo[2,1-b]thiazol-3-ol (5g).
Colorless crystals, mp:
ethanimidothioate (6b).
Colorless crystals, mp: 145–
167–169°C. Yield: 95%. IR (KBr) ( υ max, cmÀ1): 3055
(OH), 1668 (C═N). Elemental analysis: Calcd. for
(C16H19N3OS): C, 63.76; H, 6.35, N, 13.94%. Found: C,
63.89; H, 6.24, N, 13.86%. 1H-NMR (400 MHz,
DMSO-d6): δ: 1.25–1.94 (10H, m, 5CH2 of cyclohexyl),
1.94 (3H, S, CH3), 3.06–3.09 (1H, m, CHN), 7.23–7.25
(2H, m, ArH), 7.62–7.69 (2H, m, ArH), 7.70 (1H, s,
OH). 13C-NMR (100 MHz, DMSO-d6): δ: 24.16 (CH3),
25.53, 25.95, 32.54, 67.86 (C–N-cyclo), 88.86 (C–OH)
110.85, 119.08, 122.68, 122.74, 132.12, 147.06, 146.68
146°C. Yield: 96%. IR (KBr) ( υ max, cmÀ1): 1671 and
1604 (C═O and C═N). Elemental analysis: Calcd. for
(C22H23N3OS): C, 70.00; H, 6.14; N, 11.13%. Found: C,
69.83; H, 6.04; N, 11.22%. 1H-NMR (400 MHz,
DMSO-d6): 1.12–1.85 (10H, m, 5 CH2 of cyclohexyl),
2.41 (3H, s, CH3), 3.73–3.75 (1H, m, CHN), 7.40 (2H, d,
3JHH = 8.1 Hz, HAr), 7.62 (2H, dd, JHH = 6.0 Hz,
3
3JHH = 3.0 Hz, HAr), 7.85 (2 H, d, JHH = 8.1 Hz, HAr),
3
3
3
7.89 (2H, JHH = 6.0 Hz, JHH = 3.0 Hz, HAr), 9.62 (1H,
s, NH). 13C-NMR (100 MHz, DMSO-d6): δ: 21.83
(CH3), 24.99, 25.53, 32.54, 48.13 (C–N-cyclo), 114.94,
126.61, 127.20, 130.02, 130.19, 130.87, 130.97, 141.00,
145.71 (C–S), 165.13 (C═N-cyclo), 190.87 (C═O).
(C–S), 161.68 (C═N-cyclo).
3-(Chloromethyl)-2-(phenylimino)-2,3-dihydrobenzo[4,5]
imidazo[2,1-b]thiazol-3-ol (5h).
180–182°C. Yield: 98%. IR (KBr) ( υ max, cmÀ1): 3057
(OH), 1672 (C═N). Elemental analysis: Calcd. for
(C16H18ClN3OS): C, 57.22; H, 5.40, N, 12.51%. Found:
C, 57.17; H, 5.32; N, 12.46%. 1H-NMR (400 MHz,
DMSO-d6): δ: 1.29–1.82 (10H, m, 5CH2 of cyclohexyl),
Colorless crystals, mp:
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2
3.12–3.17 (1H, m, CHN), 4.20 (1H, d, JHH = 11.1 Hz,
2
CH2), 4.68 (1H, d, JHH = 11.1 Hz, CH2), 7.26 (2H, m,
HAr), 7.62–7.65 (1H, m, HAr), 7.74–7.77 (1H, m, HAr),
8.50 (1H, s, OH). 13C-NMR (100 MHz, DMSO-d6): δ:
24.03, 25.52, 32.32, 32.54, 47.19, 67.80 (C–N-cyclo),
90.00 (C–OH), 90.10 (C–Cl), 110.87, 119.23, 123.01,
123.18, 131.88, 146.97, 131.07 (C–S), 159.86 (C═N-
cyclo).
3-(2,4-Dinitrophenyl)-2-(phenylimino)-2,3-
dihydrobenzo[4,5]imidazo[2,1-b]thiazol-3-ol (5i).
Yellow
crystals, mp: 168–169°C. Yield: 98%. IR (KBr) ( υ max
cmÀ1): 3089 (OH), 1672 (C═N). Elemental analysis:
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Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

Month 2018
Synthesis of Dihydrobenzo[4,5]imidazo[2,1-b]thiazol-3-ols
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