Synthesis of 2-((2-(Benzo[d]oxazol-2-yl)-2H-imidazol -4-yl)amino)-phenols from 2-((5H-1,2,3-Dithiazol -5-ylidene)amino)phenols through Unprecedented Formation of Imidazole Ring from Two Methanimino Groups

Article abstract of DOI:10.3390/molecules25173768

A new synthetic pathway to four substituted imidazoles from readily available 2-((4-aryl (thienyl)-5H-1,2,3-dithiazol-5-ylidene)amino)phenols has been developed. Benzo[d]oxazol-2-yl(aryl (thienyl))methanimines were proved as key intermediates in their synthesis. The formation of an imidazole ring from two methanimine derivatives likely includes the opening of one benzoxazole ring followed by ring closure by intermolecular nucleophilic attack of the N-methanimine atom to a carbon atom of another methanimine.

Full text of DOI:10.3390/molecules25173768

molecules
Article
Synthesis of 2-((2-(Benzo[d]oxazol-2-yl)-2H-imidazol
-4-yl)amino)-phenols from 2-((5H-1,2,3-Dithiazol
-5-ylidene)amino)phenols through Unprecedented
Formation of Imidazole Ring from Two
Methanimino Groups
Ilia V. Baranovsky 1, Lidia S. Konstantinova 1,2, Mikhail A. Tolmachev 1 , Vadim V. Popov 2,
Konstantin A. Lyssenko 3,4 and Oleg A. Rakitin 1,2,
*
1
N. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, 119991 Moscow, Russia;
ilay679@rambler.ru (I.V.B.); konstantinova_ls@mail.ru (L.S.K.); mtolmachev4@gmail.com (M.A.T.)
Nanotechnology Education and Research Center, South Ural State University, 454080 Chelyabinsk, Russia;
popov.ioc@gmail.com
Department of Chemistry, M. V. Lomonosov Moscow State University, Leninskiye Gory, 1, 119991 Moscow,
Russia; kostya@ineos.ac.ru
2
3
4
G. V. Plekhanov Russian University of Economics, 36 Stremyanny Per., 117997 Moscow, Russia
Correspondence: orakitin@ioc.ac.ru; Tel.: +7-499-135-5327
*
ꢀꢁꢂꢀꢃꢄꢅꢆꢇ
Academic Editor: Alessandro Sacchetti
Received: 28 July 2020; Accepted: 18 August 2020; Published: 19 August 2020
ꢀꢁꢂꢃꢄꢅꢆ
Abstract: A new synthetic pathway to four substituted imidazoles from readily available 2-((4-aryl
(thienyl)-5H-1,2,3-dithiazol-5-ylidene)amino)phenols has been developed. Benzo[d]oxazol-2-yl(aryl
(thienyl))methanimines were proved as key intermediates in their synthesis. The formation of an
imidazole ring from two methanimine derivatives likely includes the opening of one benzoxazole
ring followed by ring closure by intermolecular nucleophilic attack of the N-methanimine atom to a
carbon atom of another methanimine.
Keywords: sulfur-nitrogen heterocycles; 5-Arylimino-1,2,3-dithiazoles; four substituted 2H-imidazol-
4-amines; X-ray analysis; thermolysis
1. Introduction
1,2,3-Dithiazoles are one of the most investigated groups of five membered sulfur–nitrogen
heterocycles [
active compounds [
and spintronics [ 14]. The chemistry of monocyclic 1,2,3-dithiazoles has attracted considerable
attention through recent decades [ ] due to the easy availability of 4,5-dichloro-1,2,3-dithiazolium
chloride (Appel’s salt, ) [15 16]. 4-Chlorosubtituted monocyclic 1,2,3-dithiazoles [ 17 20] were
thoroughly investigated. The most interesting and valuable parts of this reactivity are various
rearrangements of 4-chloro-1,2,3-dithiazoles, especially 5-arylimino derivatives (i.e., ), which showed a
great potential for the synthesis of multiple heterocycles, such as 1,2,4-thiadiazoles [21], isothiazoles [22],
benzoxazines and benzothiazines [23], benzimidazoles [24], quinazolones [25], benzothiazoles [26
and benzoxazoles ( , see Scheme 1) [26 28], and many others [ 29 30]. The formation of these
1
–3
]. In addition to the utility of these heterocyclic compounds as potent biologically
4–8], they are efficient precursors for functional materials applied in electronics
9–
1–3
1
,
1–3, –
2
]
3
–
1,2, ,
heterocycles was the result of the presence of a chlorine atom at the C-4 position of the 1,2,3-dithiazole
ring, which can be readily removed as a chloride anion. Presumably, one might expect that the exchange
of 4-chlorine atom in 1,2,3-dithiazoles to poorly leaving groups, such as aryl or hetaryl, can significantly
change reaction results. There is only one example of the benzoxazole ring formation (5) from
Molecules 2020, 25, 3768; doi:10.3390/molecules25173768
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2-((4-(4-nitrophenyl)-5H-1,2,3-dithiazol-5-ylidene)amino)phenol
4
[
28]. 4-Substituted 1,2,3-dithiazoles,
except 4-chloro-1,2,3-dithiazoles, are much less available, and their chemistry still needs further
developments. A couple of years ago, an easy one pot protocol for the preparation of the 4-substituted
1,2,3-dithiazolium chlorides from readily available acetoximes, disulfur dichloride and pyridine
in MeCN has been developed [31]. The treatment of these salts was prepared in situ with aniline
afforded 5-phenylimino-1,2,3-dithiazoles in low to moderate yields. Other 5-arylimino-1,2,3-dithiazoles
including o-substituted derivatives, which can be used for the synthesis of new heterocyclic systems,
were not obtained.
Scheme 1. Synthesis of 5-arylimino-1,2,3-dithiazoles
benzo[d]oxazole derivatives 3 and 5.
2 and 4 and subsequent formation of
Herein, we report the synthesis of 2-((4-aryl(hetaryl)-5H-1,2,3-dithiazol-5-ylidene)amino)phenols,
their thermal ring transformation into benzo[d]oxazol-2-yl(aryl(hetaryl)methanimines, followed by
their unprecedented dimerization of into imidazole derivatives.
2. Results and Discussion
The treatment of 4-aryl(thienyl)-5-chloro-1,2,3-dithiazolium chlorides 6, obtained in situ from
acetoximes, disulfur dichloride, and pyridine in MeCN in a conditions described by us earlier [31],
with o-aminophenol and pyridine at 0 ◦C and further stirring at room temperature for 2 h, gave imines
6
in moderate to low yields (Scheme 2). All our attempts to increase the yield of imines
base (DABCO, N-ethyldiisopropylamine or o-aminophenol), temperature of the reaction from
to room temperature, and time of dithiazolium salt formation, resulted in a decrease in the yield of
7
by varying the
−
20 ◦C
6
the target product to trace amounts. The low yields of imines
7 can be explained by low stability of the
dithiazolium salts 6 at room temperature.
The thermal behavior of imines
toluene, methanol, ethanol, acetonitrile). The imines
(8 h) in chloroform (bp 61 ◦C) and benzene (bp 80 ◦C) and were isolated from the reaction mixtures in
practically quantitative yields. The heating of the compounds in more polar solvent—ethanol (95% or
anhydrous) afforded (benzo[d]oxazol-2-yl)arylmethanones 8 in high yields (Scheme 3).
7
was investigated in various solvents (chloroform, benzene,
were found to be inert by prolonged refluxing
7
When continuing the study of thermolysis of imines
(bp 65 C), the formation of compounds other than methanones
7
, it was found that when heated in methanol
is observed. The structure of
has been confirmed by NMR and IR spectroscopy and mass-spectrometry and
was unambiguously determined by an X-ray diffraction study of thienylmethanimine 9f (Figure 1).
Presumably, the formation of imines and aroylbenzoxazoles can be explained by the collapse of
phenolic oxygen onto C-5 of the dithiazole ring with loss of HCl and sulfur followed by hydrolysis of
◦
8
the methanimines
9
9
8

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methanimines 9 [28]. The difference in the result of reactions in methanol and ethanol can be explained
by the higher stability of imine in methanol; for example, NMR spectra of imines were successfully
8
8
obtained in deuteromethanol, while our attempts to obtain similar spectra in deuteroethanol failed
due to their decomposition (hydrolysis).
Scheme 2. Synthesis of 2-((4-aryl(thien-2-yl)-5H-1,2,3-dithiazol-5-ylidene)amino)phenols 7.
Scheme 3. Thermolysis of 2-((4-aryl(thien-2-yl)-5H-1,2,3-dithiazol-5-ylidene)amino)phenols 7 in ethanol
and methanol.
Figure 1. The general view of benzo[d]oxazol-2-yl(thien-2-yl)methanimine 9f in representation of
atoms by thermal ellipsoids (p = 50%).

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In the crystal, 9f exists in the form of an isomer with the imine group in transposition to the C=N
bond of the benzo[d]oxazole ring. Such conformation can be stabilized by the intramolecular N4-H···O1
and/or C14-H···N3 interactions. In order to estimate the stability of two possible isomers, we performed
PBE1PBE/def-2-TZVP calculations with the empirical dispersion corrections. The optimization at the
above level was followed by the evaluation of the harmonic vibration frequencies. Full geometry
optimization revealed that both isomers were characterized by almost equal energy with a small
stabilization (0.87 kcal/mol) of the experimentally observed isomer (Figure 2).
(A)
(B)
Figure 2. The molecular graphs of two isomers with trans- (
The critical points (3,
and C-H···N interactions are shown by dashed lines.
A) and cis- (B) disposition of C=N bonds.
−
1) and (3, +1) are shown by small green and red balls. The bond path for C-H···
O
The topological analysis of the electron density distribution function
ρ(r) within Bader’s quantum
theory of “Atoms in Molecule” (QTAIM) [32] revealed that in both isomers, the imine group did not
participate in the formation of N-H···N or N-H···O interactions. In contrast, for C-H···O or C-H···
contacts, the critical points (3, 1) were located, and thus we can conclude that both of them are
N
−
attractive interactions. The energy of the above intramolecular C-H···N and C-H···O interactions
according to the correlation suggested by Espinosa et al. [33] was 3.1 and 2.9 kcal/mol.

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Despite conjugation in the 9f, the crystal molecule was not planar with the dihedral angle between
the thiophen ring and rest molecule equal to 5.6◦. Such conformation in 9f is clearly the consequence
of crystal packing. It was found out that the C=N-H group did not participate in any intermolecular
hydrogen bond and that molecules were assembled by stacking interactions into infinite columns with
the shortest C5···C10 contact equal to 3.405(2)Å.
Further investigation of imines
of new compounds 10 (TLC data) along with methanones
by a prolonged (4–38 h) refluxing of methanimines
7
thermolysis in toluene, acetonitrile, or THF showed the formation
and methanimines . This was confirmed
in MeCN, which led to the formation of products
8
9
9
10, selectively, with good yields. Mass spectrometry, HRMS, and 1H and 13C NMR data showed that
they are products of dimerization of methanimines 9 (Scheme 4).
Scheme 4. Synthesis of imidazoles 10 from methanimines 9.
According to the literature search in SciFinder and Reaxys databases, no similar dimerization
reaction of imino derivatives was published in the literature. The structure of imidazoles 10 was finally
proved by the X-ray analysis for 4-fluorophenyl analogue 10b (Figure 3).
Figure3. The general view of 2-((2-(benzo[d]oxazol-2-yl)-2,5-bis(4-fluorophenyl)-2H-imidazol-4-yl)amino)phenol
10b in representation of atoms by thermal ellipsoids (p = 50%).
The interesting feature of 10b was the presence of the shortened N4-H···H-C18 intramolecular
contact with H···H distance (with the account of C-H and N-H bond normalization) equal to 2.08Å.
It is reasonable to propose that this shortened contact is clearly the consequence of the competition
of the destabilization due to steric hindrance between atoms of amino-phenol and of fluorophenyl
and stabilization due to conjugation of this substituents with the central 2H-imidazol ring. In order to

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analyze the nature of the observed NH···HC contact in the experimental conformation, we performed the
optimization of hydrogen atom positions with all other parameters fixed. The consequent topological
analysis of ρ(r) revealed that this shortened intramolecular contact corresponded to attractive interaction
(Figure 4). Furthermore, the full optimization practically did not change the torsion angles, and the
above H···H contact became as short as 2.068Å with CHH and NH···H angles equal to 116.2 and 96.1◦.
Thus, we can conclude that the observed conformation was not the consequence of the crystal packing
effect but rather the inherent feature of this molecule.
Figure 4. The molecular graph of 10b according to PBE1PBE/def-2-TZVP calculation. The critical points
(3,
−
1) and (3, +1) are shown by small green and red balls. The bond path for C-H···H-N and C-H···
N
interactions is shown by dashed lines.
Crystal molecules were assembled into a centrosymmetric dimer due to the formation of the
O2-H···N3 (O···N 2.840(2)Å) hydrogen bonds. The latter dimer was additionally stabilized by the
stacking interactions with the interplane distance of ~3.4 Å (Figure 5).
Figure 5. O-H···N and stacking bonded centrosymmetric dimer in the crystal of 10b.

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Mechanistic Rationale
The described procedure provides a new synthetic pathway to imidazole derivatives from
compounds containing methanimine and benzoxazole fragments. To the best of our knowledge,
9
this reaction has not been described so far. We assume that the first step is the nucleophilic attack
of the N-methanimine atom into the carbon atom of the oxazole ring with the opening of the
benzoxazole ring to o-aminophenol moiety, which is well described for many benzoxazoles [34–36].
The result of this reaction is the formation of compounds containing three consecutive methanimino
groups 11. According to the search from Reaxys database, such structures were not known. The
second intramolecular nucleophilic attack of the methanimino-nitrogen to the carbon atom of another
methanimino group led to the 2-aminoimidazole ring closure (Scheme 5).
Scheme 5. A suggested reaction path for the formation of imidazoles 9 from methanimines 8.
3. Experimental Section
3.1. General Methods and Materials
The reagents were purchased from commercial sources and used as received. Ethan-1-one
oximes were prepared according to the published methods [37] and characterized by NMR spectra.
All synthetic operations were performed under a dry argon atmosphere. Solvents were purified
by distillation from the appropriate drying agents. Elemental analyses were performed on a 2400
Elemental Analyzer (Perkin Elmer Inc., Waltham, MA, USA). Melting points were determined on a
1
Kofler hot-stage apparatus and were uncorrected. H and 13C NMR spectra were taken with a Bruker
AM-300, AVANCE DRX 500, and AVANCE II 600 machines (Bruker Ltd., Moscow, Russia) with TMS as
the standard. J values are given in Hz. MS spectra (EI, 70 eV) were obtained with a Finnigan MAT
INCOS 50 instrument (Thermo Finnigan LLC, San Jose, CA, USA). High-resolution MS spectra were
measured on a Bruker micrOTOF II instrument using electrospray ionization (ESI). The measurement
was operated in a positive ion mode (interface capillary voltage 4500 V) or in a negative ion mode
−
(3200 V); the mass range was from m/z 50 to m/z 3000 Da; external or internal calibration was performed
with Electrospray Calibrant Solution (Fluka Chemicals Ltd., Gillingham, UK). A syringe injection was
used for solutions in acetonitrile, methanol, or water (flow rate 3
µL
min−1). Nitrogen was applied
·
as a dry gas; the interface temperature was set at 180 ◦C. IR spectra were measured with a Bruker
“Alpha-T” instrument (Bruker, Billerica, MA, USA) in KBr pellets.
X-ray diffraction data for all studied compounds were collected using a SMART APEX II
area-detector diffractometer (graphite monochromator,
ω-scan technique) at the temperature of 120(2)
K, using MoKα radiation (0.71073 Å). The intensity data were integrated by the SAINT program
and corrected for absorption and decay by the multiscan method (semi-empirical from equivalents)
implemented in SADABS. All structures were solved by direct methods using SHELXS [38] and were
refined against F2 using SHELXL-2017 [39]. All nonhydrogen atoms were refined with anisotropic
displacement parameters. All C-H hydrogen atoms were placed in ideal calculated positions and
refined as riding atoms with relative isotropic displacement parameters taken as Uiso(H) = 1.2Ueq(C).
The hydrogen atoms of NH and OH groups were located from the Fourier density synthesis. Detailed

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crystallographic information is provided in Table 1 and as Supplementary Materials in CIF format
that can be obtained free of charge via http://www.ccdc.cam.ac.uk/conts/retrieving.html or from the
Cambridge Crystallographic Data Centre, 12, Union Road, Cambridge CB2 1EZ, UK; fax: 44-1223-336033
using the reference CCDC numbers (Table 1).
Table 1. X-ray crystallographic data and refinement details for studied molecules.
9f
10b
CCDC number
Empirical formula
Formula weight
T, K
1993040
C28H18F2N4O2
480.46
1993041
C12H8N2OS
228.26
120
120
Crystal system
Space group
Z (Z’)
Monoclinic
Monoclinic
P21/n
4 (1)
P21/n
4(1)
12.3650(12)
12.9901(13)
14.3314(14)
90
107.871(2)
90
2190.9(4)
1.457
1.06
6.1355(5)
7.5454(6)
22.0813(19)
90
94.779(2)
90
a, Å
b, Å
c, Å
α, ◦
β, ◦
γ, ◦
V, Å3
1018.70(15)
1.488
Dcalc,gcm−3
µ, cm−1
2.93
F(000)◦
992
58
472
58
2θ
,
max
Reflections collected
25153
11900
Reflections unique (Rint
Reflections with I > 2σ(I)
)
5821 (0.0410)
4558
2710 (0.0357)
2443
Variables/restraints
333
149
R1
wR2
GOF
0.0425
0.1092
1.024
0.328/−0.242
0.0357
0.0962
1.036
Largest difference in peak/hole (e/Å3)
0.415/−0.342
All quantum chemistry computations were performed in the Gaussian09 program [40] using the
density functional theory (PBE0) [41] and the def-2-TZVP basis set. The choice of the PBE0 functional
was based on the recent paper in which errors of various DFT functionals in the reproduction of
an exact electron density and energy are discussed [42]. The geometry was optimized using the
very tight optimization criteria and empirical dispersion corrections on the total energy [43] with the
Becke-Johnson damping (D3) [44].
Topological analyses of the ρ(r) function were performed using the AIMAll program (AIMAll
(Version 16.08.17), T. Keith, TK Gristmill Software, Overland Park KS, USA, 2016 (aim.tkgristmill.com)).
All expected critical points were found, and the whole set of critical points in each system satisfies the
Poincaré-Hopf rule.
3.2. General Procedure for the Synthesis of 2-((4-aryl-5H-1,2,3-dithiazol-5-ylidene)amino)phenols (7)
Pyridine (0.24 mL, 3 mmol) was added dropwise at 0 to
5 ◦C to a stirred solution of ethanoneoxime
−
4
(1 mmol) and disulfur dichloride (0.16 mL, 2 mmol) in acetonitrile (10 mL) under inert atmosphere
◦
of argon. The mixture was stirred at 0 C for 15–40 min. Then o-aminophenol (109 mg, 1 mmol)
was added, the mixture was stirred at 0 ◦C for 30 min and followed by pyridine (0.16 mL, 2 mmol).
The reaction mixture was stirred at room temperature for 2 h, filtered, and solvents were evaporated.
The residue was separated by column chromatography (Silica gel Merck 60, light petroleum and then
light petroleum–CH2Cl2 mixtures).

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2-((4-Phenyl-5H-1,2,3-dithiazol-5-ylidene)amino)phenol (7a)
Yield 172 mg (30%). Yellow solid, m.p. 89–90 ◦C. Anal. calcd. for C14H10N2OS2: C, 58.72; H, 3.52;
1
N, 9.78 found: C, 58.65; H, 3.56; N, 9.80. H NMR (300 MHz, CD2Cl2)
δ
: 8.27(s, 1H, Ar), 8.21 (d, 1H
,
J = 8.1, Ar), 7.74 (m, 3H, Ar), 7.57 (t, 1H, J = 7.3, Ar), 7.30 (d, 2H, J = 11.0, Ar), 7.15 (m, 1H, Ar),
7.03 (s, 1H, OH). 13C NMR (75 MHz, CD2Cl2)
: 162.6, 161.9, 151.9, 134.7, 133.5, 130.7, 129.4, 129.1,
128.7, 120.1, 116.7, 114.8. IR,
δ
ν
, cm−1: 3321, 3055, 1563, 1478, 1248, 1145, 1032, 722, 622. m/z (%): 286 (M+,
31), 222 (47), 119 (100), 91 (45). HRMS m/z (ESI) 287.0312 (calcd. for C14H10N2OS2 [M + H]+ 287.0312).
2-((4-(4-Fluorophenyl)-5H-1,2,3-dithiazol-5-ylidene)amino)phenol (7b)
Yield 201 mg (33%). Yellow solid, m.p. 124–125 ◦C. Anal. calcd. for C14H9FN2OS2: C, 55.25; H,
1
2.98; N, 9.20 found: C, 55.20; H, 3.01; N, 9.24. H NMR (300 MHz, CD2Cl2)
δ: 8.07 (m, 2H, Ar), 7.63
(d, 1H, J = 7.8, Ar), 7.25 (m, 3H, Ar), 7.06 (m, 2H, Ar), 6.53 (s, 1H, OH). 13C NMR (75 MHz, CD2Cl2)
δ
: 164.0 (J = 286), 161.4, 151.7, 134.9, 131.6, 131.5, 129.2, 120.2, 116.7, 116.0, 115.7, 115.0. IR, ν :
, cm−1
3310, 1478, 1289, 1227, 1154, 1154, 862, 721. m/z (%): 304 (M+, 29), 240 (38), 183 (14), 119 (100), 91 (56).
HRMS m/z (ESI) 305.0220 (calcd. for C14H10FN2OS2 [M + H]+ 305.0213).
2-((4-(4-Methoxyphenyl)-5H-1,2,3-dithiazol-5-ylidene)amino)phenol (7c)
Yield 190 mg (30%). Yellow solid, m.p. 137–138 ◦C. Anal. calcd. for C15H12N2O2S2: C, 56.94;
1
H, 3.82; N, 8.85 found: C, 57.04; H, 3.78; N, 8.85.). H NMR (300 MHz, CD2Cl2)
δ
: 8.03 (d, 2H, J = 8.8
,
Ar), 7.64 (d, 1H, J = 7.7, Ar), 7.26 (t, 1H, J = 7.3, Ar), 7.06 (m, 4H, Ar), 6.63 (s, 1H, OH), 3.91 (s, 3H, CH3).
13C NMR (75 MHz, CD2Cl2)
: 162.4, 161.9, 161.7, 151.7, 135.0, 130.9, 129.4, 128.9, 120.1, 116.7, 114.8,
114.1, 55.7. IR (KBr),
δ
ν
, cm−1: 3376, 2836, 1609, 1479, 1313, 1250, 1172, 1032, 801, 727, 612. m/z (%): 316
(M+, 15), 252 (53), 183 (9), 133 (100), 119 (47), 91 (34). HRMS m/z (ESI)317.0417 (calcd. for C15H13N2O2S2
[M + H]+ 317.0413).
2-((4-(4-Bromophenyl)-5H-1,2,3-dithiazol-5-ylidene)amino)phenol (7d)
Yield 80 mg (11%). Yellow solid, m.p. 152–153 ◦C. Anal. calcd. for C14H9BrN2OS2: C, 46.03; H,
2.48; N, 7.67 found: C, 45.95; H, 2.53; N, 7.71. 1H NMR (300 MHz, CD2Cl2)
δ
: 7.95 (d, 2H, J = 8.1,
Ar), 7.68 (d, 2H, J = 8.1, Ar), 7.61 (d, 1H, J = 8.1, Ar), 7.26 (t, 1H, J = 7.7, Ar), 7.06 (m, 2H), 6.54 (s, 1H,
OH). 13C NMR (75 MHz, CD2Cl2)
: 161.9, 161.2, 151.6, 134.9, 132.3, 131.9, 130.9, 129.1, 125.1, 120.1,
116.7, 115.0. IR,
δ
ν
, cm−1: 3411, 3057, 1583, 1477, 1253, 1229, 1153, 1068, 1010, 851, 805, 772, 740, 725,
678. m/z (%): 366 (M+ +2, 11), 364 (M+, 9) 300 (12), 183 (27), 150 (5), 119 (100), 91 (47). HRMS m/z
(ESI)366.9384 (calcd. for C14H10BrN2OS2 [M + H]+ 366.9384).
2-((4-(4-Nitrophenyl)-5H-1,2,3-dithiazol-5-ylidene)amino)phenol (7e)
Yield 172 mg (26%). Orange solid, m.p. 140–141 ◦C. Anal. calcd. for C14H9N3O3S2: C, 50.74;
1
H, 2.74; N, 12.68 found: C, 50.68; H, 2.76; N, 12.72. H NMR (300 MHz, CD2Cl2)
δ: 8.37 (d, 2H, J = 8.9,
Ar), 8.26 (d, 2H, J = 8.9, Ar), 7.61 (d, 1H, J = 8.0, Ar), 7.28 (t, 1H, J = 7.8, Ar), 7.11–7.03 (m, 2H, Ar),
6.40 (s, 1H, Ar). 13C NMR (75 MHz, CD2Cl2)
: 161.8, 160.3, 151.5, 149.0, 139.1, 134.8, 130.5, 129.4, 123.9,
120.3, 116.6, 115.1. IR,
, cm−1: 3395, 1560, 1480, 1218, 1152, 1042, 843, 756, 715, 696. m/z (%): 331 (M+,
δ
ν
41), 231 (25), 183 (15), 148 (100), 123 (14), 79 (9). HRMS m/z (ESI)332.0158 (calcd. for C14H10N3O3S2
[M + H]+ 332.0162).
2-((4-(Thiophen-2-yl)-5H-1,2,3-dithiazol-5-ylidene)amino)phenol (7f)
Yield 111 mg (19%). Orange solid, m.p. 77–78 ◦C. Anal. calcd. for C12H8N2OS3: C, 49.29; H, 2.76;
1
N, 9.58 found: C, 49.21; H, 2.80; N, 9.56. H NMR (300 MHz, CD2Cl2)
δ
: 8.17 (d, 1H, J = 5.1, Ar), 7.60
(m, 2H, Ar), 7.25 (m, 2H, Ar), 7.09 (m, 2H, Ar), 6.87 (s, 1H, OH). 13C NMR (75 MHz, CD2Cl2) δ: 161.5,
156.3, 152.3, 135.3, 134.4, 131.6, 130.2, 129.4, 127.9, 120.5, 116.9, 115.6. IR, ν
, cm−1: 3439, 3119, 1556, 1479,
1222, 1151, 1035, 834, 775, 711, 680. m/z (%): 292 (M+, 32), 228 (46), 195 (16), 150 (7), 119 (100), 109 (58),
91 (47). HRMS m/z (ESI)292.9869 (calcd. for C12H9N2OS3 [M + H]+ 292.9872).

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2-((4-(Benzofuran-2-yl)-5H-1,2,3-dithiazol-5-ylidene)amino)phenol (7g)
Yield 63 mg (13%). Orange solid, m.p. 167–169 ◦C. Anal. calcd. for C16H10N2O2S2: C, 58.88;
H, 3.09; N, 8.58 found: C, 59.13; H, 3.26; N, 8.49. 1H NMR (600 MHz, CD2Cl2)
: 8.04 (s, 1H, Ar),
7.75 (d, 1H, J = 8.1, Ar), 7.63 (d, 1H, J = 8.1, Ar), 7.54 (d, 1H, J = 8.1, Ar), 7.48 (t, 1H, J = 7.7, Ar),
7.35 (t, 1H
J = 7.3, Ar), 7.29 (t, 1H, J = 7.7, Ar), 7.09 (m, 2H, Ar), 6.50 (s, 1H, OH). 13C NMR (90 MHz,
CD2Cl2) : 163.3, 156.0, 152.2, 151.1, 149.6, 137.1, 129.4, 128.3, 127.6, 124.4, 123.5, 121.0, 117.1, 115.7,
112.2, 110.5. IR,
δ
,
δ
ν
, cm−1: 3487, 3456, 3139, 3059, 2958, 2929, 2858, 1728, 1610, 1560, 1485, 1333, 1288,
1257, 1220, 1175, 1162, 1072, 1034, 883, 741, 668. m/z (%): 326 (M+, 76), 262 (100), 245 (36), 143 (98),
119 (63) 91 (19), 64 (17). HRMS m/z (ESI)327.0254 [M + H]+ (calc. for C16H10N2O2S2, m/z 327.0256).
3.3. General Procedure for the Thermolysis of 2-((4-aryl(hetaryl)-5H-1,2,3-dithiazol-5-ylidene)amino)phenols
in Various Solvents
7
Dithiazole
7 (0.2 mmol) was refluxed in solvent (10 mL) up to its disappearance (TLC control) for
the time given below. The reaction mixture was evaporated, and the residue was separated by column
chromatography (Silica gel Merck 60, light petroleum and then light petroleum–CH2Cl2, then CH2Cl2).
Benzo[d]oxazol-2-yl(phenyl)methanone (8a)
EtOH, 1.5 h, yield 44 mg (99%). Colorless solid, m.p. 72–73 ◦C. (m.p. 74–75 ◦C) [36]. The 1H and
13C NMR spectra were similar to those samples prepared by the literature method [45].
Benzo[d]oxazol-2-yl(4-fluorophenyl)methanone (8b)
EtOH, 1 h, yield 47 mg (97%). Colorless solid, m.p. 138–141 ◦C. (m.p. 108–110 ◦C) [36]. The 1H
and 13C NMR spectra were similar to those described in the literature [45].
Benzo[d]oxazol-2-yl(4-methoxyphenyl)methanone (8c)
EtOH, 1 h, yield 50 mg (98%). Colorless solid, m.p. 123–124 ◦C. (m.p. 78–80 ◦C) [36]. The 1H and
13C NMR spectra were similar to those described in the literature [45].
Benzo[d]oxazol-2-yl(4-bromophenyl)methanone (8d)
EtOH, 1.5 h, yield 59 mg (98%). Light yellow solid, m.p. 113–115 ◦C. (m.p. 140–142 ◦C) [37].
The 1H and 13C NMR spectra were similar to those described in the literature [46].
Benzo[d]oxazol-2-yl(4-nitrophenyl)methanone (8e)
EtOH, 1.5 h, yield 49 mg (92%). Colorless solid, m.p. 160–161 ◦C. (m.p. 139–141 ◦C) [36]. The 1H
and 13C NMR spectra were similar to those described in the literature [45].
Benzo[d]oxazol-2-yl(thiophen-2-yl)methanone (8f)
EtOH, 8 h, yield 40 mg (87%). Colorless solid, m.p. 119–120 ◦C. (m.p. 105–107 ◦C) [36]. The 1H
and 13C NMR spectra were similar to those described in the literature [45].
Benzo[d]oxazol-2-yl(benzofuran-2-yl)methanone (8g)
EtOH, 5 h, yield 59 mg (89%). Colorless solid, m.p. 210–211 ◦C. Anal. calcd. for C16H9NO3: C,
1
73.00; H, 3.45; N, 5.32 found: C, 73.15; H, 3.56; N, 5.11. H NMR (600 MHz, CD2Cl2)
δ: 8.75 (s, 1H,
Ar), 8.02 (d, 1H, J = 7.9, Ar), 7.91 (d, 1H, J = 7.9, Ar), 7.80 (d, 1H, J = 7.9, Ar), 7.72 (d, 1H, J = 8.6, Ar),
7.65–7,58 (m, 2H, Ar), 7.56 (t, 1H, J = 7.6, Ar), 7.43 (t, 1H, J = 7.9, Ar). 13C NMR (150 MHz, CD2Cl2)
169.0, 156.9, 156.8, 151.0, 150.7, 141.1, 129.9, 126.9, 127.6, 126.3, 124.6, 124.6, 122.6, 121.2, 112.8, 112.2. IR,
δ:
ν
, cm−1: 3440, 3139, 3105, 3065, 2960, 2926, 2855, 2361, 2342, 1657, 1613, 1542, 1528 1478, 1445, 1326,
1309, 1265, 1124, 1006, 991, 895, 737. m/z (EI) 263 (M+, 39), 145 (100), 118 (4), 89 (71), 28 (10). HRMS m/z
(ESI)302.0215 [M + K]+ (calc. for C16H9KNO3, m/z 302.0214).

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Benzo[d]oxazol-2-yl(phenyl)methanimine (9a)
MeOH, 1.5 h, yield 43 mg (98%). Colorless amorphous solid, m.p. 40–42 ◦C. Anal. calcd. for
1
C14H10N2O: C, 73.00; H, 3.45; N, 5.32 found: C, 73.15; H, 3.56; N, 5.11. H NMR (500 MHz, CD3OD)
δ
:
8.07(s, 1H, Ar), 7.85 (d, 1H, J = 7.3, Ar), 7.76–7.72 (m, 2H, Ar), 7.59(d, 1H, J = 7.3, Ar), 7.55–7.52 (m, 3H,
Ar), 7.48 (t, 1H, J = 7.6, Ar), 7.38 (d, 1H, J = 6.1, Ar). 13C NMR (150 MHz, CD3OD)
: 162.4, 150.3, 140.6,
, cm−1 3463, 3434, 2363, 2339, 1721, 1704,
δ
133.7, 130.8, 129.2, 128.8, 127.7, 126.9, 125.6, 124.9, 110.7. IR,
ν
1634, 1562, 1545, 1526, 1511, 1400, 1369, 1041, 1000, 966, 671, 571, 430. m/z (%): 222 (M+, 100), 119 (84),
104 (58), 91 (38), 77 (44). HRMS m/z (ESI)245.0688 [M + Na]+ (calcd. for C14H10NaN2O, m/z 245.0685).
Benzo[d]oxazol-2-yl(4-fluorophenyl)methanimine (9b)
MeOH, 1 h, yield 46 mg (99%). Colorless solid, m.p. 103–104 ◦C. Anal. calcd. for C14H9FN2O: C,
1
69.99; H, 3.78; N, 11.66 found: C, 70.23; H, 3.98; N, 11.82. H NMR (500 MHz, CD3OD)
δ
:
8.06 (s, 1H
,
Ar), 7.79 (d, 1H, J = 8.1, Ar), 7.69 (d, 1H, J = 8.1, Ar), 7.53–7.40 (m, 3H, Ar), 7.21 (t, 3H, J = 8.8, Ar).
13C NMR (125 MHz, CD2Cl2)
: 169.9, 150.0, 139.9 (J = 173), 131.1, 131.0 (, 128.3, 127.0, 124.9, 124.1, 114.7,
114.5, 110.7. IR,
δ
ν
, cm−1: 3435, 3270, 3045, 1602, 1507, 1451, 1414, 1381, 1334, 1230, 1188, 1158, 1104,
952, 843, 744, 633. m/z (%): 240 (M+,100), 122 (68), 119 (94), 95 (57), 75 (54). HRMS m/z (ESI)263.0587
[M + Na]+ (calcd. for C14H9NaFN2O, m/z 263.0591).
Benzo[d]oxazol-2-yl(4-methoxyphenyl)methanimine (9c)
◦
MeOH, 1 h, yield 43 mg (87%). Colorless amorphous solid, m.p. 63–64 C. Anal. calcd. for
1
C15H12N2O2: C, 71.42; H, 4.79; N, 11.10 found: C, 71.55; H, 4.92; N, 4.52. H NMR (500 MHz, CD3OD)
δ
: 8.07 (s, 1H, Ar), 7.85(d, 1H, J = 7.9, Ar), 7.75 (d, 1H, J = 8.6, Ar), 7.55 (t, 1H, J = 7.3, Ar), 7.48(t, 1H,
J = 7.3, Ar), 7.06 (d, 2H, J = 9.2, Ar) 3.89 (s, 3H, MeO). 13C NMR (125 MHz, CD3OD)
: 162.4, 150.2,
140.5, 132.9, 130.4, 126.8, 124.9, 120.5, 119.1, 113.1, 112.8, 110.7, 54.2. IR,
, cm−1 3465, 3433, 3402, 3276,
δ
ν
3084, 3014, 2951, 2931, 2913, 2838, 2382, 2346, 2290, 1777, 1737, 1721, 1704, 1686, 1653, 1608, 1539, 1454,
1421, 1377, 1337, 1306, 1256, 1175, 1154, 1110, 1070, 1029, 1004, 951, 913, 893, 832, 808, 745, 712, 651, 625,
610, 563, 507, 427. m/z (%) 252 (M+,100), 237 (6), 221 (13), 134 (75), 119 (37), 91 (11), 77 (7). HRMS m/z
(ESI)275.0791 [M + Na]+ (calcd. for C15H12NaN2O2, m/z 275.0791).
Benzo[d]oxazol-2-yl(4-bromophenyl)methanimine (9d)
MeOH.1.2 h, yield 60 mg (98%). Colorless solid, m.p. 82–83 ◦C. Anal. calcd. for C14H9BrN2O: C,
1
55.84; H, 3.01; N, 9.30 found: C, 55.99; H, 3.23; N, 9.11. H NMR (600 MHz, CD3OD)
δ:
8.07 (d, 1H
,
J = 6.6, Ar), 7.88 (d, 1H, J = 8.1, Ar), 7.78 (d, 1H, J = 8.1, Ar), 7.73 (d, 2H, J = 8.8, Ar), 7.58 (t, 1H,
J = 8.4, Ar), 7.51 (t, 1H, J = 7.3, Ar). 13C NMR (150 MHz, CD2Cl2)
: 151.4, 141.7, 133.0, 132.0, 129.3,
δ
128.2, 126.3, 126.1, 125.3, 121.8, 111.8, 111.3. IR, ν, cm−1: 3587, 3492, 3435, 2926, 2856, 1591, 1530, 1485,
1459, 1357, 1237, 1191, 1148, 1072, 1010, 945, 862, 826, 773, 738, 691. m/z (%): 299 (M+, 32%), 221 (7),
182 (21), 119 (100), 91 (43), 76 (25). HRMS m/z (ESI)322.9792 [M + Na]+ 324.9770 [M + Na]+ (calcd. for
C14H9NaBrN2O, m/z 322.9792, 324.9770).
Benzo[d]oxazol-2-yl(4-nitrophenyl)methanimine (9e)
MeOH, 1.5 h, yield 60 mg (97%). Colorless solid, m.p. 130–131 ◦C. Anal. calcd. for C14H9N3O3:
C, 62.92; H, 3.39; N, 15.72 found: C, 63.13; H, 3.52; N, 15.48. 1H NMR (600 MHz, CD3OD)
8.10–7.94 (m, 4H, Ar), 7.80 (d, 1H, J = 9.5, Ar), 7.72 (d, 1H, J = 5.9, Ar), 7.42–7.26 (m, 2H, Ar).
13C NMR (150 MHz, CD2Cl2)
δ: 169.5, 152.0, 148.1, 147.9, 132.4, 132.2, 127.7, 124.4, 121.1, 119.5, 118.6,
110.6. IR, ν, cm−1: 3467, 3436, 3267, 3109, 1589, 1521, 1482, 1447, 1408, 1347, 1238, 1156, 1106, 952, 917,
852, 743, 682. m/z (%): 267 (M+, 64%), 221 (3), 149 (7), 119 (100), 103 (28), 76 (25), 46 (9). HRMS m/z
(ESI)290.0536 [M + Na]+ (calcd. for C14H9NaN3O3, m/z 290.0536).

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Benzo[d]oxazol-2-yl(thiophen-2-yl)methanimine (9f)
MeOH, 1.5 h, yield 43 mg (96%). Colorless solid, m.p. 69–70 ◦C. Anal. calcd. for C12H8N2OS: C,
1
63.14; H, 3.53; N, 12.27 found: C, 63.07; H, 3.55; N, 12.30. H NMR (300 MHz, CD2Cl2)
δ:
11.04 (s, 1H),
8.42 (d, 1H, J = 1.4, Ar), 7.92 (d, 1H, J = 7.5, Ar), 7.72 (d, 1H, J = 7.9, Ar), 7.63 (d, 1H, J = 4.8, Ar),
7.61–7.44 (m, 2H, Ar), 7.25 (t, 1H, J = 4.3, Ar). 13C NMR (75 MHz, CD2Cl2)
: 156.9, 150.8, 141.5, 137.8,
, cm−1: 3464, 3296, 3088, 2926, 1638, 1571, 1541,
δ
133.1, 131.1, 128.3, 127.6, 125.7, 121.8, 112.1, 111.5. IR,
ν
1431, 1229, 1137, 1048, 942, 836, 744, 730, 611. m/z (%): 228 (M+, 77%), 144 (23), 120 (6), 109 (100), 84 (7),
64 (6), 76 (5). HRMS m/z (ESI) 229.0432 [M + H]+ (calcd. for C12H9N2OS, m/z 229.0430).
Benzo[d]oxazol-2-yl(benzofuran-2-yl)methanimine (9g)
MeOH, 1.5 h, yield 50 mg (95%). Colorless solid, m.p. 159–161 ◦C. Anal. calcd. for C16H10N2O2:
C, 73.27; H, 3.84; N, 10.68 found: C, 73.45; H, 3.90; N, 10.42. NMR (600 MHz, CD3OD)
NH), 7.83 (d, 1H, J = 8.1, Ar), 7.70 (d, 1H, J = 7.3, Ar), 7.65 (d, 1H, J = 8.1, Ar), 7.53 (d, 1H, J = 8.1, Ar),
7.44 (t, 1H, J = 7.7, Ar), 7.39 (t, 2H, J = 7.7, Ar), 7.26 (t, 1H, J = 7.3, Ar). 13C NMR (90 MHz, CD3OD)
154.7, 152.7, 149.8, 140.4, 128.8, 127.8, 126.7, 126.5, 124.6, 123.0, 120.6, 120.1, 111.7, 111.1, 110.9, 110.7. IR,
δ: 8.11 (s, 1H,
δ:
ν
, cm−1: 3448, 3287, 3138, 3092, 3065, 2957, 2924, 2853, 1654, 1615, 1590, 1557, 1525, 1474, 1450, 1229,
1170, 1123, 1005, 974, 894, 873, 734. m/z (%): 262 (M+, 100), 245 (24), 143 (81), 119 (51), 94 (13), 89 (50),
63 (34). HRMS m/z (ESI)301.0376 [M + K]+ (calcd. for C16H10N2O2K, m/z 301.0374).
General procedure for the thermolysis of benzo[d]oxazol-2-yl(aryl(hetaryl))methanimines 9 in MeCN
Methanimine
9 (0.2 mmol) was refluxed in MeCN (10 mL) up to its disappearance (TLC control)
for the time given below. Reaction mixture was evaporated and the residue was separated by column
chromatography (Silica gel Merck 60, light petroleum and then light petroleum–CH2Cl2, then CH2Cl2).
2-((2-(Benzo[d]oxazol-2-yl)-2,5-diphenyl-2H-imidazol-4-yl)amino)phenol (10a)
Yield 26 mg (58%). Colorless solid, m.p. 246–248 ◦C. Anal. calcd. for C28H20N4O2: C, 75.66;
1
H, 4.54; N, 12.60 found: C, 75.70; H, 4.52; N, 12.56. H NMR (300 MHz, DMSO-d6,)
δ: 10.26 (s, 1H,
NH), 8.54 (d, 1H, J = 5.7, Ar), 8.02–7.90 (m, 5H, Ar), 7.71 (m, 5H, Ar), 7.47–7.41 (m, 5H, Ar), 6.94 (s, 3H,
Ar). 13C NMR (125 MHz, DMSO-d6,)
: 164.8, 163.8, 156.3, 150.3, 146.2, 140.3, 138.4, 131.7, 130.0, 129.6,
128.5, 128.3, 128.2, 128.1, 127.5, 125.8, 124.8, 123.6, 120.2, 119.5, 118.7, 114.5, 111.1, 100.8. IR,
, cm−1
δ
ν
:
3390, 3083, 1636, 1611, 1581, 1529, 1458, 1243, 746, 696, 568. m/z (%): 444 (M+, 12), 414 (26), 310 (9),
222 (100), 207 (48), 120 (16), 93 (41), 77 (12). HRMS m/z (ESI)445.1648 [M + H]+ (calc. for C28H21N4O2,
m/z 445.1659).
2-((2-(Benzo[d]oxazol-2-yl)-2,5-bis(4-fluorophenyl)-2H-imidazol-4-yl)amino)phenol (10b)
Yield 40 mg (83%). Colorless solid, m.p. 217–219 ◦C. Anal. calcd. for C28H18F2N4O2: C, 69.99;
1
H, 3.78; N, 11.66 found: C, 69.90; H, 3.82; N, 11.73. H NMR (300 MHz, DMSO-d6,)
δ: 10.25 (s, 1H, NH),
8.46 (d, 1H, J = 7.4, Ar), 8.05 (s, 1H, OH), 8.03 (s, 2H, Ar), 7.96–7.91 (m, 2H, Ar), 7.76 (d, 1H, J = 8.7
Ar), 7.10 (d, 1H, J = 8.6, Ar), 7.53 (t, 2H, J = 8.7, Ar), 7.40–7.38 (m, 2H, Ar), 7.29 (t, 2H, J = 8.8, Ar),
6.95 (s, 3H, Ar). 13C NMR (125 MHz, DMSO-d6,)
: 155.6 (J = 192), 155.5, 153.4 (J = 246), 147.8, 141.6,
137.8, 131.6, 125.8, 122.4, 121.7, 121.6, 118.7, 117.1, 116.1, 115.1, 111.5, 110.8, 110.4, 107.9, 106.5, 106.3,
,
δ
106.0, 102.4, 91.4. IR, ν
, cm−1: 3423, 3068, 2926, 1632, 1589, 1572, 1529, 1506, 1456, 1236, 1157, 1081,
832, 747, 524. m/z (%): 480 (M+, 75%), 359 (100), 346 (96), 239 (23), 225 (13), 197 (10), 122 (15), 91 (6).
HRMS m/z (ESI)481.1477 [M + H]+ (calc. for C28H19F2N4O2, m/z 481.1471).
2-((2-(Benzo[d]oxazol-2-yl)-2,5-bis(4-methoxyphenyl)-2H-imidazol-4-yl)amino)phenol (10c)
Yield 42 mg (84%). Colorless crystals, m.p. 242–244 ◦C. Anal. calcd. for C30H24N4O4: C, 71.42; H,
1
4.79; N, 11.10 found: C, 71.50; H, 4.65; N, 11.05. H NMR (500 MHz, DMSO-d6,)
δ: 10.28 (s, 1H, NH),
8.53 (d, 1H, J = 7.4, Ar), 7.99 (s, 1H, OH), 7.91 (d, 2H, J = 8.7, Ar), 7.79 (d, 2H, J = 8.8, Ar), 7.74 (d, 1H
,
J = 7.2, Ar), 7.69 (d, 1H, J = 7.2, Ar), 7.42–7.34 (m, 2H, Ar), 7.23 (d, 2H, J = 8.7, Ar), 7.01 (d, 2H, J = 8.8,

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Ar), 6.97–6.90 (m, 3H, Ar), 3.90 (s, 3H, CH3), 3.79 (s, 3H, CH3). 13C NMR (125 MHz, DMSO-d6,)
155.5, 155.2, 153.1, 150.6, 147.5, 141.5, 137.4, 131.6, 121.9, 121.3, 120.7, 118.9, 116.9, 116.0, 114.7, 113.5,
δ:
111.4, 110.8, 110.0, 106.3, 105.8, 104.9, 102.3, 91.4, 46.8, 46.5. IR, ν
, cm−1: 3391, 2927, 2840, 1608, 1582,
1509, 1458, 1250, 1172, 1026, 831, 747. m/z (%): 504 (M+, 9), 472 (25), 356 (82), 328 (37), 252 (100), 120 (5),
106(8), 93 (7), 78(14). HRMS m/z (ESI)505.1887 [M + H]+ (calc. for C30H25N4O4 m/z 505.1870).
2-((2-(Benzo[d]oxazol-2-yl)-2,5-bis(4-bromophenyl)-2H-imidazol-4-yl)amino)phenol (10d)
Yield 40 mg (66%). Colorless crystals, m.p. 251–253 ◦C. Anal. calcd. for C28H18Br2N4O2: C, 55.84;
1
H, 3.01; N, 9.30 found: C, 55.84; H, 3.10; N, 9.25. H NMR (300 MHz, CD2Cl2)
δ: 10.25 (s, 1H, NH),
7.85 (d, 2H, J = 8.2, Ar), 7.81–7.67 (m, 6H, Ar), 7.64–7.53 (m, 4H, Ar), 7.42–7.35 (m, 2H, Ar), 7.07 (t, 1H
J = 6.3, Ar), 6.96 (t, 2H, J = 7.2, Ar). 13C NMR (75 MHz, CD2Cl2)
: 163.9, 163.4, 157.6, 151.4, 147.9,
147.8, 140.8, 137.3, 133.0, 132.7, 132.2, 131.8, 130.3, 130.2, 129.0, 126.3, 126.0, 125.0, 121.3, 121.0, 120.6,
,
δ
111.2, 100.4. IR, ν
, cm−1: 3407, 2925, 2854, 1635, 1591, 1579, 1457, 1243, 1072, 1010, 821, 748. m/z (%): 604
(M+ + 2, 13%), 602 (M+, 14), 522 (18), 483 (100), 446 (90), 442 (5), 300 (23), 284 (45), 167 (17), 156 (14),
107 (35), 79 (37). HRMS m/z (ESI)600.9875 [M + H]+ (calc. for C28H19Br2N4O2 m/z 600.9869).
2-((2-(Benzo[d]oxazol-2-yl)-2,5-bis(4-nitrophenyl)-2H-imidazol-4-yl)amino)phenol (10e)
Yield 40 mg (62%). Light yellow crystals, m.p. 213–215 ◦C. Anal. calcd. for C28H18N6O6: C, 62.92;
1
H, 3.39; N, 15.72; O, 17.96 found: C, 62.85; H, 3.30; N, 15.81. H NMR (300 MHz, CD2Cl2,) 8.69 (d, 1H,
J = 6.6), 8.35 (d, 2H, J = 8.1, Ar), 8.42–8.14 (m, 4H, Ar), 8.00 (t, 1H, J = 7.7, Ar), 7.89 (d, 2H, J = 8.1, Ar),
7.65 (d, 1H, J = 7.3, Ar), 7.47 (d, 1H, J = 7.3, Ar), 7.34–7.29 (m, 3H, Ar), 6.89 (t, 2H, J = 6.6, Ar), 6.78 (d,
1H, J = 4.4, Ar). 13C NMR (75 MHz, CD2Cl2,)
δ
: 163.7, 162.5, 156.9, 151.1, 149.8, 146.7, 144.1, 135.5,
129.7, 129.7, 126.1, 125.5, 125.0, 124.6, 123.5, 121.8, 121.2, 120.9, 120.4, 120.3, 116.9, 116.2, 111.1, 100.7.
IR, ν
, cm−1: 3420, 2956, 2927, 2855, 1776, 1736, 1720, 1703, 1685, 1639, 1583, 1521, 1458, 1406, 1347,
1311, 1282, 1245, 1218, 1201, 1173, 1107, 1076, 1039, 1014, 984, 932, 888, 849, 747, 692. m/z (%): 534 (M+,
38%), 488 (100), 435 (26), 411 (45), 365 (28), 268 (7), 148 (19), 123 (18), 79 (5). HRMS m/z (ESI)535.1366
[M + H]+ (calc. for C28H19N6O6, m/z 535.1361).
2-((2-(Benzo[d]oxazol-2-yl)-2,5-bis(thiophen-2-yl)-2H-imidazol-4-yl)amino)phenol (10f)
◦
Yield 22 mg (48%). Dark brown amorphous crystals, m.p. 142–144 C. Anal. calcd. for
1
C24H16N4O2S2: C, 63.14; H, 3.53; N, 12.27 found: C, C, 63.11; H, 3.54; N, 12.32. H NMR (300 MHz,
DMSO-d6,) 10.39 (s, 1H, NH), 8.42 (d, 1H, J = 7.4, Ar), 8.28 (s, 1H, OH), 8.08 (m, 2H, Ar), 8.04 (d, 1H,
J = 3.5, Ar), 7.79–7.71 (m, 2H, Ar), 7.59 (d, 1H, J = 5.1, Ar), 7.45–7.40 (m, 4H, Ar), 7.13 (t, 1H, J = 8.7,
Ar), 6.98–6.94 (m, 3H, Ar). 13C NMR (75 MHz, DMSO-d6,)
δ
: 158.4, 156.2, 150.2, 146.6, 140.2, 139.4,
132.8, 131.7, 130.5, 130.1, 129.1, 127.5, 127.3, 126.9, 126.7, 125.9, 124.8, 123.9, 121.9, 120.2, 119.4, 119.3,
114.6, 111.1. IR, ν
, cm−1: 3392, 3116, 2927, 2855, 2362, 1629, 1577, 1531, 1457, 1384, 1239, 1067, 836, 748,
710. m/z (%): 456 (M+, 5%), 347 (21), 322 (50), 284 (100), 228 (18), 119 (19), 110 (15), 91 (9). HRMS m/z
(ESI)457.0797 [M + H]+ (calc. for C24H17N4O2S2, m/z 457.0787).
2-((2-(Benzo[d]oxazol-2-yl)-2,5-bis(benzofuran-2-yl)-2H-imidazol-4-yl)amino)phenol (10g)
Yield 30 mg (57%). Yellow crystals, m.p. 231–233 ◦C. Anal. calcd. for C32H20N4O4: C, 73.45;
1
H, 3.99; N, 10.32 found: C, 73.27; H, 3.84; N, 10.68. H NMR (300 MHz, CD2Cl2)
δ: 8.94 (s, 1H, NH),
7.95 (d, 1H, J = 6.6, Ar), 7.89 (s, 1H, Ar), 7.83 (d, 1H, J = 7.3, Ar), 7.76 (d, 1H, J = 8.1, Ar), 7.64 (d, 1H,
J = 7.3, Ar), 7.59–7.29 (m, 8H, Ar), 7.08 (s, 1H, Ar), 6.94 (d, 2H, J = 8.7, Ar), 6.85 (s, 1H, Ar). 13C NMR
(150 MHz, CD2Cl2)
δ: 161.9, 158.6, 155.8, 155.7, 152.0, 151.4, 147.7, 147.6, 140.8, 128.1, 127.9, 127.4, 127.3,
126.3, 125.9, 125.3, 125.2, 124.8, 123.5, 123.1, 121.9, 121.5, 120.9, 120.7, 120.0, 118.4, 116.8, 113.4, 112.2,
111.8, 111.4, 106.3. IR, ν
, cm−1: 3386, 3115, 3064, 2923, 2853, 1632, 1592, 1557, 1506, 1455, 1348, 1281,
1248, 1166, 1147, 1106, 1068, 1002, 930, 874, 822, 746, 618, 430. m/z (%): 524 (M+, 16%), 262 (51), 145 (96),
119 (41), 94 (100), 63 (80). HRMS m/z (ESI)563.1116 [M + K]+ (calcd. for C32H20N4O4, m/z 563.1116).

Molecules 2020, 25, 3768
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4. Conclusions
In summary, a new unprecedented formation of four substituted imidazoles containing a
benzoxazole ring from the thermolysis of readily available 2-((4-aryl(hetaryl)-5H-1,2,3-dithiazol-
5-ylidene)amino)phenols was developed. The possibility of the imidazole ring formation from the
compounds containing two methanimino groups was proved. Finally, 4-aryl(hetaryl)-substituted
5H-1,2,3-dithiazoles gave, upon thermolysis, different products from 4-chloro derivatives where
the chlorine atom was readily expelled as a chloride anion, and the cyano group was generated.
2,2-Diaryl-2H-imidazol-4-amines are of interest as a BACE-1 inhibitors for the treatment of Alzheimer’s
disease or dementia [47,48].
Supplementary Materials: The Supplementary Materials are available online. Characterization data including
1H and 13C NMR spectra for novel compounds and single crystal X-ray crystallography data (CCDC 1850211 and
1850212 for compounds 9f and 10b, respectively).
Author Contributions: O.A.R. conceived and designed the study; L.S.K., I.V.B., M.A.T., and V.V.P. performed the
experiments; L.S.K. analyzed the data; K.A.L. carried out the XRD studies and DFT calculations. All authors have
read and agreed to the published version of the manuscript.
Funding: This research was funded by The Scientific Schools Development Program by the Zelinsky Institute of
Organic Chemistry, grant number NSh 31.
Conflicts of Interest: The authors declare no conflict of interest.
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Sample Availability: Samples of the compounds are available from the authors.
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