Selective Synthesis of 2-Substituted and 1,2-Disubstituted Benzimidazoles Directly from Aromatic Diamines and Alcohols Catalyzed by Molecularly Defined Nonphosphine Manganese(I) Complex

Article abstract of DOI:10.1021/acs.joc.8b01316

Herein, we present a selective synthesis of 2-substituted and 1,2-disubstituted benzimidazoles by acceptorless dehydrogenative coupling of aromatic diamine with primary alcohols. The reaction is catalyzed by a phosphine-free tridentate NNS ligand-derived manganese(I) complex.

Full text of DOI:10.1021/acs.joc.8b01316

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Note
Selective Synthesis of 2-substituted and 1,2-disubstituted Benzimidazoles
Directly from Aromatic Diamines and Alcohols Catalyzed by
Molecularly Defined Non-Phosphine Manganese (I) Complex.
KALICHARAN DAS, Avijit Mondal, and Dipankar Srimani
J. Org. Chem., Just Accepted Manuscript • DOI: 10.1021/acs.joc.8b01316 • Publication Date (Web): 11 Jul 2018
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The Journal of Organic Chemistry
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Selective Synthesis of 2-substituted and 1,2-disubstituted Benzimid-
azoles Directly from Aromatic Diamines and Alcohols Catalyzed by
Molecularly Defined Non-Phosphine Manganese (I) Complex.
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Kalicharan Das, Avijit Mondal and Dipankar Srimani*
Department of Chemistry, Indian Institute of Technology-Guwahati, Kamrup, Assam 781039, India.
Supporting Information
ABSTRACT: Herein, we present a selective synthesis of 2-substituted and 1,2-disubstituted benzimidazoles by acceptorless dehy-
drogenative coupling of aromatic diamine with primary alcohols. The reaction is catalyzed by phosphine free tridentate NNS ligand
derived manganese (I) complex.
Over the past few years, benzimidazoles and their derivatives
have attracted significant attention due to their important bio-
logical as well as pharmacological properties.1 Several pharma-
ceutically important compounds having benzimidazole core are
known for their antiallergic,2 antihistaminic,3 anti-ulcerative,4
antihypertensive5 and antipyretic properties.6 Furthermore, ben-
zimidazole derivatives are also effective against HIV7 and hu-
man cytomegalovirus (HCMV).8 The classical approach to syn-
thesize benzimidazoles is the condensation of o-phenylenedia-
mine with carboxylic acids or carboxylic acid-derivatives under
strong acidic conditions.9 Another widely used strategy in-
volves the condensation 1,2-phenelynediamine with alde-
hyde/alcohol in the presence of different oxidizing agents.10
Several other different catalytic approaches to synthesize ben-
zimidazoles are also reported.11-14 However many of these
method suffers either from the use of stoichiometric amount
of oxidizing agents or expensive catalysts. Another major prob-
lem is the selectivity during the synthesis of 2-substituted and
1,2-disubstituted benzimidazoles. In recent times, acceptorless
dehydrogenation strategies for synthesis of different heterocy-
cles directly from alcohols15 are becoming more and more im-
portant, as alcohols can be readily obtained from renewable lig-
nocellulose.16 Thus, the synthesis of benzimidazoles17 directly
from primary alcohol and o-phenylenediamine has recently at-
tracted much attention and most of these methodologies use pre-
cious noble metals and/or acceptors.18 One of the earliest exam-
ple of such type of reaction was developed by Watanbe and
coworkers.18a The reaction is catalyzed by ruthenium complex
at elevated temperature (215 °C). Recently, Kempe and co-
workers developed an elegant method to synthesize 2-substi-
tuted benzimidazoles under relatively milder condition.18b The
reaction is catalyzed by iridium pincer complex and does not
involve any acceptor. Selective synthesis of 1,2-disubstituted
imidazole from diamine and alcohol catalysed by Ir(III) com-
plexes was also accomplished recently.18c
The replacement of costly noble-metal catalyst by inexpen-
sive environmentally benign earth-abundant metals is an im-
portant goal in homogenous catalysis. In the recent years, con-
siderable efforts were made towards the development of several
different de(hydrogenative) reaction methodologies using base
metal complexes.19 Although manganese is less expensive
abundant and nontoxic metal, the catalytic de(hydrogenative)
reactions with manganese is still in the nascent stage. The
(de)hydrogenative reactions catalyzed by Mn-pincer complexes
became a very important topic in the area of catalysis after the
seminal works published independently by the group of Mil-
stein, Beller, Kempe and Kirchner in 2016.20 Subsequent to
these reports a significant number of intriguing transformations
catalyzed by Mn-complexes have been developed.21
Very recently, the formation of 2-substituted benzimidazoles
catalyzed by cobalt pincer22 complex has been reported by Mil-
stein and co-workers. However, selective synthesis of both 2-
substituted and 1,2-disubstituted benzimidazoles from 1,2-dia-
mino benzene and alcohol using earth-abundant, nontoxic metal
catalyst is highly desirable. To the best of our knowledge the
synthesis of benzimidazoles directly from 1,2-diaminobenzene
and alcohol catalyzed by manganese has not been reported.
Herein, we describe a general and selective method to synthe-
size both 2-substituted and 1,2-disubstituted benzimidazoles
from 1,2-diamino benzene and alcohol using non-phosphine-
manganese complex. At the outset, we prepared new NNS-
Manganese (I) complex (1) by refluxing 2-(ethylthio)-N
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Table 2. Scope of the reaction to synthesize 1,2-disubstituted
benzimidazole a, b
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Figure 1. Synthesis of tridentate NNS ligand based manganese (I)
complex and molecular structure of 1 with thermal ellipsoid 30%
probability level. (all the hydrogens except N2 and the counter ion
are not shown for the clarity)
-(pyridin-2-ylmethyl)ethanamine with MnBr(CO)5 in THF.
Single crystal suitable for X-ray diffraction was made by layer-
ing THF solution of the complex 1 with toluene. The crystal
structure of 1 is more like octahedral geometry around Mn-cen-
ter, which is formed by tridentate ligand and three carbonyl
groups. The crystal structure reveals that both the N atoms and
the S atom are cis to each other and the three carbonyls are cis
to each other (Figure 1).
Table 1. Optimization of the reaction conditions for the syn-
thesis of 1,2-disubstituted benzimidazolea, b
aReaction conditions: Diamine
2
(0.5 mmol), alcohol
3 (1.7
mmol), tBuOK (1 mmol), Cat
1 (0.05 mmol), 20 h, under argon,
bIsolated yield, c44 h, d26 h
The catalytic applicability of complex 1 towards the synthesis
of 1,2-disubstituted benzimidazole, directly from 1,2-phe-
nylenediamines and alcohols has been investigated. To find out
the optimum conditions, the reaction between 1,2-phenylenedi-
amine and 4-methoxybenzylalcohol was studied under neat
condition. It was found that the particular ratio of base and sub-
strate and specific ratio of amine and alcohol is important for
good yield of the desired products. Potassium tert-butoxide was
found to be more effective base than KOH or K2CO3 (Table 1
entries 6, 12 and 13). MnBr(CO)5 gave only trace amount of
the desired product under the similar reaction conditions. The
control experiments were also performed and it was observed
that in the absence of catalyst, no desired product was obtained
and similarly without the presence of base, complex 1 failed to
give any desired product (Table 1 entries 10, 11).
Here, a wide range of 1-benzyl-2-aryl-1H-benzo[d]imidazole
derivatives were also synthesized from 1,2-diaminobeznene
and primary alcohol (Table 2). Differently substituted benzylic
alcohols as well as 2-naphthalenemethanol reacted well with o-
phenylenediamine to give good yield of the desired products.
Moderate to good yield of the desired 1,2-disubstituted benzim-
idazoles were achieved when heterocyclic alcohols such as 2-
pyridinemethanol, furfural or 2-thiophenemethanol have been
employed as substrates. A small amount of bis N-alkylated
aReaction conditions: 2a (0.5 mmol), 3b (1.5-2.0 mmol), tBuOK
(0.75-2.0 mmol), Cat 1 (0.05 mmol), under argon. bNMR yield us-
ing CH3CN as internal standard. c0.025 mmol cat used. d80 °C
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Table 3. Synthesis of 2-substituted benzimidazole a, b
Excellent yield of the desired products were obtained with the
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7
8
benzyl alcohols having both electron donating and electron
withdrawing group in the aromatic ring. For example,
4-methylbenzyl alcohol and 4-methoxybenzyl alcohol gave
81% and 82% yield of the desired benzimidazole respectively,
which is even higher than the yield reported by Ru18a or cobalt
catalyst.22 However, the reaction is slower with aliphatic alco-
hols. Thus, when 1-octanol was used as substrate, 35% of the 2-
ethyl-1H-benzo[d]imidazole was obtained after 72 hours. To
our delight, complex 1 also able to catalyse the dehydrogenative
coupling of N-Benzyl-1,2-diaminobenzene (6) with different
benzyl alcohols to afford 1-benzyl-2-aryl-1H-benzo[d]imidaz-
ole derivatives (7) in good yield (Table 4).
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In addition, three possible mechanistic pathways are pro-
posed which are depicted in the (Scheme 1). At first, the alde-
hyde was formed by the assistance of Mn-complex 1. The dia-
mine can react with the aldehyde A to form monoamine B
which can further undergo nucleophilic addition to the imine
carbon to form benzimidazoline intermediate C. This interme-
diate benzimidazoline C either undergoes oxidation leading to
the formation of 2-substituted benzimidazole 5a or reacts fur-
ther with the aldehyde A to generate intermediate D which will
finally transform to 1,2-disubstituted imidazole 4a (Path II).
There is also a possibility of N-alkylation of 2-substituted ben-
zimidazole23 by primary alcohol through borrowing hydrogen
strategy, which will eventually transform 5a, to 4a (Path I). Fur-
thermore, diamine also can lead to the formation of bis-imine F
which undergoes rearrangement to afford 1,2-disubstituted ben-
zimidazole (Path III).17i
aReaction conditions: Diamine (1.0 mmol), alcohol (1.3 mmol),
KOH (0.27 mmol), Cat
1
(0.05 mmol), 20 h, under air. bIsolated
yield, c72 h
product of the o- phenylenediamine was also observed in some
cases, which might be due to the hydrogenation of bis-imines
formed in-situ during the reaction. Furthermore, 4,5-Dimethyl-
1,2-phenylenediamine, 4,5-Dichloro-o-phenylenediamine and
3,4-diaminotoluene reacted smoothly under the optimized reac-
tion condition. 3,4-diaminotoluene gave mixture of two iso-
meric 1-benzyl-2-aryl-1H-benzo[d]imidazole derivatives. It is
important to note that synthesis of 2-aryl-1H-benzo[d]imidaz-
ole derivatives could also be achieved just by tuning the reac-
tion conditions (Table 3).
Scheme 1. Plausible mechanistic pathway
Table 4. Synthesis of 1-benzyl-2-aryl-1H-benzo[d]imidaz-
olesa, b
Although the exact pathway is not fully clear at this point, yet
we tried to shed light on the mechanism by controlling experi-
ment. First of all, when 2-(4-methoxyphenyl)-1H-benzo[d]im-
idazole 5b was treated with 4-methoxybenzyl alcohol 3a in
presence of Cat 1 and tBuOK, no N-alkylated product, 1-(4-
methoxybenzyl)-2-(4-methoxyphenyl)-1H-benzo[d]imidazole
4b was observed (Scheme 2). Thus, it is clear that the reaction
is not following Path I. MS analysis of the crude reaction mix-
ture of o-phenylenediamine and 4-methoxybenzyl alcohol after
2 h, showed peak which corresponds either to bisimine (F, Ar=
aReaction conditions: N-Benzyl-1,2-diaminobenzene (1.0
mmol), alcohol (1.3 mmol), KOH (0.27 mmol), Cat
1 (0.05
mmol), 20 h, under air. bIsolated yield.
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Scheme 2. Study of N-alkylation of 2-substituted benzimid-
azole By Cat 1
s, 1H), 7.40 (br s, 1H), 4.81(br s, 1H), 4.58 (br s, 1H), 3.39-
3.35 (m, 2H), 2.98-2.87 (m, 2H), 2.05 (br s, 2H), 1.45 (s, 3H);
1
2
25
13C NMR (150 MHz, CDCl3) δ 218.92, 216.57, 161.90,
152.64, 139.58, 125.25, 122.70, 60.41, 54.57, 33.07, 31.85,
13,42. IR (cm-1): 3059, 2920, 2875, 2030, 1946, 1920, 1609,
1462, 1286, 1196, 1083, 949, 910, 821, 769, 689, 637. HRMS
(ESI) calcd for C13H16MnN2O3S [M]+: 335.0262; found,
335.0263.
3
4
5
6
7
General experimental procedure for the synthesis of
1,2-disubstituted benzimidazoles: A mixture of o-phenylene-
diamine (0.5 mmol), primary alcohol (1.7 mmol), KOtBu (1.0
mmol) and complex 1 (0.05 mmol) was stirred at 140 °C for the
specified time under solvent free condition in an open system
under argon. Then the reaction mixture was cooled to room tem-
perature and was diluted with chloroform. Then it was filtered
through celite and the filtrate was concentrated under vacuum.
The residue obtained was further purified by column chroma-
tography on silica gel using 10%-30 % ethyl acetate in hexane
as an eluent.
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p-C6H4OMe) or 1,2 disubstituted benzimidazole 4b (as the mo-
lecular weight of both the compound are same) while the ion
peak corresponds to intermediate (D, Ar = p-C6H4OMe) was not
observed. We have also isolated small amount bis-amine H dur-
ing the synthesis of 1-benzyl-2-aryl-1H-benzo[d]imidazole de-
rivatives which finally validate the involvement of bis-imine in-
termediate F and formation of 1,2 disubstituted imidazole de-
rivatives via Path III.
General experimental procedure for the synthesis of 2-
substituted benzimidazoles: A mixture of 1,2-diaminoben-
zene (1.0 mmol), primary alcohol (1.3 mmol), KOH (0.27
mmol) and catalyst 1 (0.05 mmol) was stirred under neat con-
dition at 140 °C for 20 h in open air. After cooling, MeOH was
added to dilute the mixture and filtered through celite. The fil-
trate was concentrated under reduced pressure and the residue
was purified by silica gel column chromatography using 10% -
30 % ethyl acetate in hexane as an eluent to get pure compound.
In Summary, we have synthesized a new tridentate NNS-
ligand based manganese (I) complex, which catalyzes the dehy-
drogenative coupling of diamine and primary alcohol to synthe-
size a wide range of benzimidazole derivatives. The main ad-
vantage of this methodology is 3-fold: selectively 2-substituted
and 1,2 di-substituted benzimidazoles are synthesized using a
single catalyst just by tuning the reaction conditions, the reac-
tions are catalyzed by earth abundant metal and catalytic reac-
tions are performed under phosphine free condition.
General experimental procedure for the synthesis of 1-
benzyl-2-aryl-1H-benzo[d]imidazoles: A mixture of N-Ben-
zyl-1,2-diaminobenzene (1.0 mmol), primary alcohol (1.3
mmol), KOH (0.27 mmol) and catalyst 1 (0.05 mmol) was
stirred under neat condition at 140 °C for 20 h in open air. After
cooling, CHCl3 was added to dilute the mixture and then it was
filtered through celite. The filtrate was concentrated under vac-
uum and the residue was purified by silica gel column chroma-
tography using 10% -30 % ethyl acetate in hexane as an eluent
to get pure compound.
1-Benzyl-2-phenyl-1H-benzo[d]imidazole (4a).17a White
solid, (0.113mg, 79% yield). 1H NMR (600 MHz, CDCl3) δ 7.80
(d, J = 8.04 Hz, 1H), 7.62-7.60 (m, 2H), 7.40- 7.36 (m, 3H),
7.27-7.21 (m, 4H), 7.18-7.13 (m, 2H), 7.03 (d, J = 7.02 Hz, 2H),
5.39 (s, 2H); 13C NMR (150 MHz, CDCl3) δ 154.3, 143.3,
136.5, 136.2, 130.2, 130.0, 129.4, 129.2, 128.9, 127.9, 126.1,
123.2, 122.8, 120.1, 110.7, 48.5.
EXPERIMENTAL SECTION
General Considerations: Unless otherwise mentioned, all
the chemicals were purchased from common commercial
sources and used as received. All solvents were dried by using
standard procedure. The preparation of catalyst was carried out
under argon atmosphere with freshly distilled dry THF. All cat-
alytic reactions were carried out with air and/or under argon at-
mosphere using dried glassware and standard syringe/septa
techniques. DRX-400 Varian spectrometer and Bruker Avance
1
III 600 and 400 spectrometers were used to record H and 13C
NMR spectra using CDCl3 and DMSO-d6 as solvent and TMS
as an internal standard. Chemical shifts (δ) are reported in ppm
and spin-spin coupling constant (J) are expressed in Hz, and
other data are reported as follows: s = singlet, d = doublet, t =
triplet, m = multiplet, q = quartet, and br s = broad singlet. X-
ray crystallographic data were collected using Agilent Super
Nova (Single source at offset, Eos) diffractometer. FTIR were
collected on PerkinElmer IR spectrometer. Q-Tof ESI-MS in-
strument (model HAB 273) was used for recording mass spec-
tra. SRL silica gel (100-200 mesh) were used for column chro-
matography.
1-(4-methoxybenzyl)-2-(4-methoxyphenyl)-1H-
benzo[d]imidazole (4b).17a White solid, (0.129mg, 83% yield).
1H NMR (600 MHz, CDCl3) δ 7.75 (d, J = 7.98 Hz, 1H), 7.55
(d, J = 8.7 Hz, 2H), 7.22-7.18 (m, 1H), 7.15-7.12 (m, 2H), 6.94
(d, J = 8.52 Hz, 2H), 6.88 (d, J = 8.7 Hz, 2H), 6.76 (d, J = 8.7
Hz, 2H), 5.29 (s, 2H), 3.75 (s, 3H), 3.69 (s, 3H); 13C NMR (150
MHz, CDCl3) δ 161.0, 159.2, 154.2, 143.2, 136.2, 130.8, 128.6,
127.3, 122.8, 122.6, 122.5, 119.8, 114.5, 114.3, 110.5, 55.5,
55.4, 48.0.
Synthesis and characterization of NNS-Mn-complex 1:
Ligand24 [(PyCH2)HN(CH2CH2SEt)] (0.302g, 1.54 mmol) was
taken in 4 mL dry THF and was added dropwise to the orange-
yellow suspension of [MnBr(CO)5] (0.423g, 1.54 mmol) in 8
mL degassed dry THF. Then, the suspension was refluxed for
overnight under argon atmosphere. After cooling it down to the
room temperature, the solvent was evaporated to obtain the res-
idue, which was further washed with hexane and dried under
vacuum to get yellow solid of Mn-complex 1 (yield 0.610g,
95%). The single crystal was grown by slow diffusion of tolu-
1-(3-methoxybenzyl)-2-(3-methoxyphenyl)-1H-
benzo[d]imidazole (4c).18c White solid, (0.156mg, 91% yield).
1H NMR (400 MHz, CDCl3) δ 7.79 (d, J = 5.32Hz, 1H), 7.29-
7.23 (m, 2H), 7.19-7.16 (m, 5H), 6.95-6.96 (m, 1H), 6.75 (dd, J
= 7.2 Hz, 1.14 Hz, 1H), 6.62 (d, J = 5.12 Hz, 1H), 6.58 (s,1H),
5.36 (s, 2H), 3.66 (s, 3H), 3.65 (s, 3H);13C NMR (100 MHz,
CDCl3); δ 160.3, 159.8, 154.1, 143.1, 138.3, 136.3, 131.3,
1
ene in the THF solution of the complex. H NMR (600 MHz,
CDCl3) δ 8.69 (s, 1H), 8.26 (br s, 1H), 7.87 (br s, 1H), 7.71 (br
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130.3, 130.0, 123.2, 122.8, 121.5, 120.1, 118.3, 116.7, 114.1,
113.0, 112.0, 110.6, 55.4, 55.3, 48.4.
130.6, 129.5, 129.3, 128.5, 127.4, 123.6, 123.2, 120.3, 110.4,
47.9.
1-(4-chlorobenzyl)-2-(4-chlorophenyl)-5,6-dimethyl-
1
2
3
4
5
6
7
8
2-(naphthalen-2-yl)-1-(naphthalen-2-ylmethyl)-1H-
benzo[d]imidazole (4d).17a White solid, (0.155mg, 81% yield).
1H NMR (400 MHz, CDCl3) δ 8.13 (s, 1H), 7.88-7.75 (m, 6H),
7.67-7.63 (m, 2H), 7.49-7.39 (m, 5H), 7.30-7.16 (m, 4H), 5.59
(s, 2H); 13C NMR (100 MHz, CDCl3) δ 154.4, 143.4, 136.5,
134.1, 133.8, 133.5, 133.02, 132.9, 129.4, 129.2, 128.7, 128.7,
128.0, 127.9, 127.4, 126.8, 126.8, 126.4, 126.2, 124.9, 124.0,
123.4, 123.0, 120.2, 110.7, 48.9.
1H-benzo[d]imidazole (4k).27 White solid, (0.145mg, 76%
yield). 1H NMR (400 MHz, CDCl3) δ 7.61 (s, 1H), 7.56 (d, J =
8.48 Hz, 2H), 7.41 (d, J = 8.48 Hz, 2H), 7.31 (d, J = 8.40 Hz,
2H), 7.01 (d, J = 8.24 Hz, 2H), 6.95 (s, 1H), 5.34 (s, 2H), 2.39
(s, 3H), 2.34 (s, 3H); 13C NMR (100 MHz, CDCl3) δ 152.2,
141.9, 136.2, 135.1, 134.7, 133.9, 132.9, 132.2, 130.5, 129.5,
129.2, 128.8, 127.3, 120.3, 110.5, 47.8, 20.7, 20.5.
9
1-(4-methylbenzyl)-2-(p-tolyl)-1H-benzo[d]imidazole
(4e).17a White solid, (0.126mg, 81% yield). 1H NMR (600
MHz, CDCl3) δ 7.78 (d, J = 8.04 Hz, 1H), 7.51 (d, J = 8.16 Hz,
2H), 7.23-7.21 (m, 1H), 7.19 -7.17 (m, 2H), 7.16- 7.11 (m, 2H),
7.06 (d, J = 7.92 Hz, 2H), 6.92 (d, J = 8.04 Hz, 2H), 5.33 (s,
2H), 2.33 (s, 3H), 2.26 (s, 3H); 13C NMR (150 MHz, CDCl3) δ
154.5, 143.3, 140.1, 137.5, 136.2, 133.6, 129.8, 129.6, 129.3,
127.3, 126.0, 122.9, 122.7, 119.9, 110.6, 48.3, 21.6, 21.2.
1-benzyl-5,6-dimethyl-2-phenyl-1H-benzo[d]imidazole
10
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(4l).28 White solid, (0.121mg, 77% yield). H NMR (600 MHz,
1
CDCl3) δ 7.67-7.65 (m, 2H), 7.63 (s, 1H), 7.45-7.40 (m, 3H),
7.35-7.28 (m, 3H), 7.10 (d, J = 7.08 Hz, 2H), 6.97 (s, 1H), 5.41
(s, 2H), 2.39 (s, 3H), 2.32 (s, 3H); 13C NMR (150 MHz, CDCl3)
δ 153.5, 141.9, 136.8, 134.8, 132.4, 131.7, 130.4, 129.8, 129.3,
129.2, 128.8, 127.8, 126.0, 120.1, 110.7, 48.4, 20.7, 20.5.
5,6-Dimethyl-1-(4-methylbenzyl)-2-(4-methylphenyl)-
1H-benzimidazole (4m).27 White solid, (0.122mg, 72% yield).
1H NMR (600 MHz, CDCl3) δ 7.61 (s, 1H), 7.55 (d, J = 8.04
Hz, 2H), 7.22 (d, J = 7.92 Hz, 2H), 7.13 (d, J = 7.86 Hz, 2H),
6.99 (d, J = 7.92 Hz, 2H), 6.96 (s, 1H), 5.36 (s, 2H), 2.39 (s,
3H), 2.38 (s, 3H), 2.34 (s, 3H), 2.32 (s, 3H); 13C NMR (150
MHz, CDCl3) δ 153.6, 141.8, 139.8, 137.4, 134.8, 133.9, 132.1,
131.5, 129.8, 129.5, 129.2, 127.5, 125.9, 120.0, 110.7, 48.2,
21.5, 21.2, 20.7, 20.5.
1-(3-phenoxybenzyl)-2-(3-phenoxybenzyl)-1H-
benzo[d]imidazole (4f).26
Brown liquid, (0.186mg, 80%
yield). 1H NMR (600 MHz, CDCl3) δ 7.75 (d, J = 7.98 Hz, 1H),
7.34 -7.29 (m, 2H), 7.24-7.21 (m, 6H), 7.19-7.16 (m, 1H), 7.14-
7.12 (m, 2H), 7.05-7.0 (m, 3H), 6.92 (dd, J = 8.58 Hz, 1.02 Hz,
2H), 6.86 (dd, J =8.46 Hz, 1.02 Hz, 2H), 6.80 (d, J = 6.72 Hz,
1H), 6.64 (d, J = 6.84 Hz, 2H); 5.31 (s, 2H); 13C NMR (150
MHz, CDCl3); δ 158.1, 157.9, 156.6, 153.5, 143.1, 138.3, 136.0,
131.7, 130.5, 130.3, 130.0, 129.9, 129.8, 123.9, 123.9, 123.8,
123.4, 122.9, 120.6, 120.2, 120.2, 119.4, 119.3, 119.2, 117.9,
116.3,110.6, 48.2.
5,6-dimethyl-2-(naphthalen-2-yl)-1-(naphthalen-2-
ylmethyl)-1H-benzo[d]imidazole (4n).28 White solid,
(0.187mg, 91% yield). 1H NMR (CDCl3, 600 MHz) δ 8.18 (s,
1H), 7.90-7.82 (m, 5H), 7.74-7.70 (m, 3H), 7.57 (s, 1H), 7.53-
7.46 (m, 4H), 7.33 (d, J = 8.46 Hz, 1H), 7.05 (s, 1H), 5.63(s,
2H), 2.42 (s, 3H), 2.33(s, 3H); 13C NMR (150MHz, CDCl3) δ
153.6, 142.1, 135.1, 134.4, 133.7, 133.6, 133.0, 132.9, 132.6,
131.9, 129.2, 129.1, 128.7, 128.6, 128.1, 127.9, 127.9, 127.7,
127.2, 126.7, 126.7, 126.3, 126.3, 124.7, 124.0, 120.2, 110.7,
48.8, 20.8, 20.5.
2-(thiophen-2-yl)-1-(thiophen-2-ylmethyl)-1H-
benzo[d]imidazole (4g).17a White solid, (0.121mg, 81% yield).
1H NMR (600 MHz, CDCl3) δ 7.76 (d, J = 7.08 Hz, 1H), 7.45
(dd, J = 5.37 Hz, 1.02 Hz, 1H), 7.40 (dd, J = 3.75 Hz, 1.02 Hz,
1H), 7.31-7.29 (m, 1H), 7.25-7.19 (m, 2H), 7.17 (dd, J = 5.1 Hz,
1.14 Hz, 1H), 7.08-7.06 (m, 1H), 6.88-6.87 (m, 1H), 6.80-6.79
(m, 1H), 5.63 (s, 2H); 13C NMR (150 MHz, CDCl3); δ 147.7,
143.1, 138.9, 136.0, 132.0, 129.1, 128.1, 128.1, 127.4, 125.6,
125.5, 123.4, 123.1, 120.1, 110.0, 44.2.
5,6-dimethyl-2-(pyridin-2-yl)-1-(pyridin-2-ylmethyl)-
1H-benzo[d]imidazole (4o).29 Orange solid, (0.137mg, 87%
yield). 1H NMR (600 MHz, CDCl3) δ 8.59 (d, J = 4.56 Hz,
1H), 8.53 (d, J = 4.56 Hz, 1H), 8.44 (d, J = 8.04 Hz, 1H), 7.81
(dt, J =7.83 Hz, 1.56 Hz, 1H), 7.62 (s, 1H), 7.47 (dt, J = 7.71
Hz, 1.68 Hz, 1H), 7.27-7.25 (m, 1H), 7.15-7.13 (m, 1H), 7.11
(s, 1H), 6.83 (d, J = 7.92 Hz, 1H), 6.25 (s, 2H), 2.38 (s, 3H),
2.33 (s, 3H); 13C NMR (150 MHz, CDCl3) δ 157.8, 150.6,
149.2, 149.2, 148.7, 141.4, 137.0, 136.9, 135.5, 133.3, 132.1,
124.4, 123.7, 122.3, 120.9, 120.1, 110.8, 51.2, 20.8, 20.5.
2-(pyridin-2-yl)-1-(pyridin-2-ylmethyl)-1H-
benzo[d]imidazole (4h).17a
White solid, (0.113mg, 79%
yield). 1H NMR (CDCl3, 400 MHz) δ 8.50 (t, J=5.02 Hz, 2H),
8.39 (d, J = 8.0 Hz, 1H), 7.80-7.74 (m, 2 H), 7.42-7.38 (dt, J =
7.74, 1.68 Hz, 1H), 7.29 (d, J = 7.92 Hz, 1H), 7.25-7.16 (m,
3H), 7.07-7.04 (m, 1H), 6.82 (d, J = 7.92 Hz, 1H), 6.22 (s, 2H);
13C NMR (100 MHz, CDCl3) δ 157.6, 150.5, 150.0, 149.3,
148.8, 142.8, 137.0, 137.0, 136.9, 124.7, 124.0, 123.8, 123.1,
122.4, 121.1, 120.2, 110.9, 51.2.
5,6-dichloro-1-(4-methoxybenzyl)-2-(4-methoxy-
2-(furan-2-yl)-1-(furan-2-ylmethyl)-1H-benzo[d]imid-
phenyl)-1H-benzo[d]imidazole
(4p).17d
White
solid,
azole (4i).17a White solid, (0.089mg, 67% yield). H NMR (400
(0.122mg, 64% yield). 1H NMR (400 MHz, CDCl3) δ 7.89 (s,
1H), 7.62 (d, J = 8.64 Hz, 2H), 7.28 (s, 1H), 6.99 (t, J = 8.24
Hz, 4H), 6.88 (d, J =8.52Hz, 2H), 5.34 (s, 2H), 3.86 (s, 3H),
3.80 (s, 3H); 13C NMR (100 MHz, CDCl3) δ 161.4, 159.5,
156.2, 142.7, 135.5, 130.8, 127.6, 127.2, 126.7, 126.7, 121.7,
121.0, 114.8, 114.5, 111.9, 55.6, 55.5, 48.2.
1
MHz, CDCl3) δ 7.72-7.69 (m,1H), 7.57 (d, J =0.96 Hz, 1H),
7.44-7.40 (m,1H), 7.25-7.18 (m, 3H),7.14 (d, J = 3.44 Hz, 1H),
6.54-6.53 (m, 1H), 6.21-6.16 (m, 2H), 5.57 (s, 2H); 13C NMR
(100 MHz, CDCl3); δ 149.7, 145.5, 144.1, 144.0, 143.1,142.8,
135.6, 123.4, 123.1, 119.9, 113.1, 112.2, 110.7, 110.1, 108.5,
41.8.
5-methyl-1-(4-methylbenzyl)-2-(p-tolyl)-1H-
1-(4-chlorobenzyl)-2-(4-chlorobenzyl)-1H-benzo[d]im-
benzo[d]imidazole
&
6-methyl-1-(4-methylbenzyl)-2-(p-
idazole (4J).17a White solid, (0.137mg, 78% yield). H NMR
tolyl)-1H-benzo[d]imidazole (4q & 4q′).17f White solid,
(0.127mg, 78% yield). 1H NMR (600 MHz, CDCl3) δ 7.72 (d,
J = 8.16 Hz, 1H), 7.63 (s, 1H), 7.58-7.55 (m, 4H), 7.25-7.22 (m,
4H), 7.15-7.11 (m, 5H), 7.07-7.02 (m, 2H), 7.00-6.98 (m, 5H),
5.36 (s, 4H), 2.48 (s, 3H), 2.42 (s, 3H), 2.39 (s, 3H), 2.39 (s,
1
(400 MHz, CDCl3) δ 7.79 (d, J =7.92 Hz, 1H), 7.51 (d, J = 8.52
Hz, 2H), 7.37 (d, J = 8.52 Hz, 2H), 7.30 - 7.22 (m, 3H), 7.20-
7.12 (m, 2H), 6.95 (d, J = 8.44 Hz, 2H), 5.33 (s, 2H); 13C NMR
(100 MHz, CDCl3) δ 153.0, 143.2, 136.5, 136.1, 134.8, 134.0,
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3H), 2.34 (s, 3H), 2.33 (s, 3H); 13C NMR (150 MHz, CDCl3) δ
150.0, 148.7, 142.8, 137.5, 136.9, 136.9, 128.6, 127.4,
126.9,124.7, 123.9, 123.6, 122.9, 120.2, 110.8, 49.0.
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154.3, 154.0, 143.5, 141.3, 140.0, 139.9, 137.5, 137.4, 136.5,
134.3, 133.7, 133.7, 133.0, 132.3, 129.8, 129.8, 129.5, 129.5,
129.2, 129.2, 127.4, 126.0, 125.9, 124.4, 124.3, 119.7, 119.4,
110.4, 110.1, 48.3, 48.1, 22.0, 21.7, 21.5, 21.5, 21.2, 21.2.
2-phenyl-1H-benzo[d]imidazole (5a).17c Pale yellow
solid, (0.149mg, 77% yield). 1H NMR (600 MHz, DMSO-d6)
δ 12.95 (br s, 1H), 8.19 (d, J = 7.14 Hz, 2H), 7.67(d, J = 6.96
Hz, 1H), 7.57-7.54 (m, 3H), 7.50-7.48 (m, 1H), 7.23-7.19 (m,
2H), 13C NMR (150 MHz, DMSO-d6) δ 151.3, 143.8, 135.0,
130.2, 129.9, 129.0, 126.5, 122.6, 121.8, 118.9, 111.4.
5-methyl-2-(thiophen-2-yl)-1-(thiophen-2-ylmethyl)-
1H-benzo[d]imidazole & 6-methyl-2-(thiophen-2-yl)-1-(thi-
ophen-2-ylmethyl)-1H-benzo[d]imidazole (4r & 4r′).17f Yel-
low solid, (0.091mg, 59% yield). 1H NMR (600 MHz, CDCl3)
δ 7.70 (d, J = 8.22, 1H), 7.61 (s, 1H), 7.51-7.49 (m, 2H), 7.45-
7.42 (m, 2H), 7.26-7.23 (m, 3H), 7.15-7.09 (m, 5H), 6.96-6.93
(m, 2H), 6.86-6.85 (m 2H), 5.67 (s, 2H), 5.66 (s, 2H), 2.48 (s,
3H), 2.47 (s, 3H); 13C NMR (150 MHz, CDCl3) δ 147.6, 147.2,
143.4, 141.2, 139.1, 139.1, 136.2, 134.1, 133.6, 132.9, 132.1,
132.1, 128.9, 128.8, 128.0, 128.0, 127.8, 127.4, 127.3, 125.5,
125,5, 125.4, 124.9, 124.8, 119.8, 119.5, 109.8, 109.5, 44.2,
44.1, 22.1, 21.7.
2-(4-methoxyphenyl)-1H-benzo[d]imidazole
(5b).17c
White solid, (0.184mg, 82% yield). 1H NMR (600 MHz,
DMSO-d6) δ 12.76 (s, 1H), 8.11 (d, J = 8.76 Hz, 2H), 7.61 (d, J
= 7.5 Hz, 1H), 7.49 (d, J = 7.5 Hz, 1H), 7.19 - 7.14 (m, 2H),
7.11(d, J = 8.76 Hz, 2H), 3.84 (s, 3H); 13C NMR (150 MHz,
DMSO-d6) δ 160.6, 151.4, 143.9, 135.0, 128.1, 122.7, 122.2,
121.5, 118.5, 114.4, 111.1, 55.4.
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2-(3-methoxyphenyl)-1H-benzo[d]imidazole
(5c).17c
1
White solid, (0.189mg, 85% yield). H NMR (400 MHz,
DMSO-d6) δ 12.90 (s, 1H), 7.77-7.75 (m, 2H), 7.67 (d, J = 7.44
Hz, 1H), 7.53 (d, J = 7.36 Hz, 1H), 7.46 (t, J = 7.6 Hz, 1H),
7.24-7.17 (m, 2H), 7.07-7.05 (m, 1H), 3.86 (s, 3H); 13C NMR
(100 MHz, DMSO-d6) δ 159.7, 151.1, 143.7, 135.0, 131.5,
130.1, 122.6, 121.7, 118.9, 118.8, 115.9, 111.4, 111.3, 55.3.
1-benzyl-2-(p-tolyl)-1H-benzo[d]imidazole
(7a).17b
White solid, (0.201mg, 67% yield). 1H NMR (400 MHz,
CDCl3) δ 7.78 (d, J = 8.0 Hz, 1H), 7.49 (d, J = 8.08Hz, 2H),
7.25-7.19 (m, 4H), 7.16 (d, J = 8.0 Hz, 2H), 7.13-7.09 (m, 2H),
7.01 (d, J = 6.84 Hz, 2H), 5.35 (s, 2H), 2.31 (s, 3H); 13C NMR
(100 MHz, CDCl3) δ 154.4, 143.3, 140.1, 136.6, 136.2, 129.5,
129.2, 129.1, 127.8, 127.2, 126.1, 123.0, 122.7, 120.0, 110.5,
48.5, 21.5.
2-(naphthalen-2-yl)-1H-benzo[d]imidazole
(5d).17c
1
Yellow solid, (0.179mg, 73% yield). H NMR (400 MHz,
DMSO-d6) δ 13.08 (s, 1H), 8.75 (s, 1H), 8.32 (d, J = 8.04 Hz,
1H), 8.09-7.99 (m, 3H), 7.70 (d, J = 6.64 Hz, 1H), 7.61-7.59
(m, 3H), 7.23 (s, 2H); 13C NMR (100 MHz, DMSO-d6) δ 151.3,
143.9, 135.2, 133.5, 132.8, 128.6, 128.5, 127.8, 127.62, 127.1,
126.9, 125.8, 124.0, 122.7, 121.8, 118.9, 111.4.
1-benzyl-2-(4-methoxyphenyl)-1H-benzo[d]imidazole
(7b).17b White solid, (0.219mg, 70% yield). 1H NMR (600
MHz, CDCl3) δ 7.86 (d, J = 8.04 Hz, 1H), 7.63 (d, J = 8.82 Hz,
2H), 7.34- 7.28 (m, 4H), 7.23-7.18 (m, 2H), 7.11(d, J = 7.38 Hz,
2H), 6.96 (d, J = 8.76 Hz, 2H), 5.43 (s, 2H), 3.83 (s, 3H); 13C
NMR (150 MHz, CDCl3) δ 161.0, 154.2, 143.2, 136.6, 136.2,
130.7, 129.1, 127.8, 126.0, 122.8, 122.6, 122.4, 119.8, 114.3,
110.5, 55.4, 48.4.
2-(p-tolyl)-1H-benzo[d]imidazole (5e).17c White solid,
(0.169mg, 81% yield). 1H NMR (400 MHz, DMSO-d6) δ 12.82
(s, 1H), 8.07 (d, J = 8.12 Hz, 2H), 7.64 (d, J = 6.12 Hz, 1H),
7.51 (d, J = 6.24 Hz, 1H), 7.35 (d, J = 8.0 Hz, 2H), 7.18 (d, J =
3.76 Hz, 2H), 2.38 (s, 3H); 13C NMR (100 MHz, DMSO-d6) δ
151.4, 143.8, 139.6, 135.0, 129.5, 127.5, 126.4, 122.3, 121.6,
118.7, 111.2, 21.0.
1-benzyl-2-(4-fluorophenyl)-1H-benzo[d]imidazole
(7c).17b White solid, (0.184mg, 61% yield). 1H NMR (600
MHz, CDCl3) δ 7.86 (d, J = 8.04 Hz, 1H), 7.68-7.65(m, 2H),
7.35-7.31(m, 4H), 7.26-7.22 (m, 2H), 7.14 (t, J = 8.58 Hz, 2H),
7.09 (d, J = 7.2, 2H), 5.43 (s, 2H); 13C NMR (150 MHz, CDCl3)
δ 163.8 (d, J=249 Hz), 153.3, 143.1, 136.3, 136.2, 131.4, 131.3,
129.3, 128.0, 126.3 (d, J=3 Hz), 126.0, 123.1 (d, J=55.5 Hz),
120.1, 116.1 (d, J=21 Hz), 110.6, 48.4.
2-(3-phenoxyphenyl)-1H-benzo[d]imidazole
(5f).31
Yellow solid, (0.246mg, 86% yield). 1H NMR (400 MHz,
DMSO-d6) δ 12.94 (s, 1H), 7.96 (d, J = 7.72 Hz, 1H), 7.81 (s,
1H), 7.65 (d, J = 7.6 Hz, 1H), 7.57 (t, J = 7.96 Hz, 1H), 7.52 (d,
J = 7.56 Hz, 1H), 7.45 (t, J = 8.04 Hz, 2H), 7.24-7.11 (m, 6H);
13C NMR (100 MHz, DMSO-d6) δ 157.4, 156.3, 150.5, 143.6,
135.0, 132.0, 130.8, 130.2, 123.9, 122.7, 121.8, 121.4, 120.0,
119.0, 119.0, 116.0, 111.4.
1-benzyl-2-(4-chlorophenyl)-1H-benzo[d]imidazole
(7d).17b White solid, (0.202mg, 64% yield). 1H NMR (400
MHz, CDCl3) δ 7.79 (d, J = 7.96 Hz, 1H), 7.55 (d, J = 8.56 Hz,
2H), 7.35 (d, J = 8.56 Hz, 2H), 7.29-7.23 (m, 4H), 7.20-7.15
(m, 2H), 7.01 (d, J = 6.52 Hz, 2H), 5.36 (s, 2H); 13C NMR (100
MHz, CDCl3) δ 153.1, 143.2, 136.3, 136.3, 136.3, 130.7, 129.3,
129.2, 128.7, 128.1, 126.0, 123.4, 123.0, 120.2, 110.6, 48.5.
2-(thiophen-2-yl)-1H-benzo[d]imidazole (5g).17c Yel-
low solid, (0.150mg, 75% yield). 1H NMR (400 MHz, DMSO-
d6) δ 12.94 (s, 1H), 7.83 (d, J = 3.6 Hz, 1H), 7.72 (d, J = 4.92
Hz, 1H), 7.55(s, 2H), 7.24-7.18 (m, 3H). 13C NMR (100 MHz,
DMSO-d6) δ 147.0, 133.7, 128.8, 128.3, 126.7, 122.6, 122.5,
121.9, 118.5, 111.3, 111.1.
1-benzyl-2-(4-bromophenyl)-1H-benzo[d]imidazole
(7e).17b White solid, (0.240mg, 66% yield). 1H NMR (400
MHz, CDCl3) δ 7.86 (d, J = 7.96 Hz, 1H), 7.59-7.53(m, 4H),
7.36-7.30(m, 4H), 7.27-7.21(2H), 7.08 (d, J = 6.52 Hz, 2H),
5.42 (s, 2H); 13C NMR (100 MHz, CDCl3) δ 153.1, 143.2,
136.3, 132.1, 130.8, 129.3, 129.1, 128.0, 126.0, 124.6, 123.5,
123.0, 120.2, 110.6, 48.5.
1-benzyl-2-(pyridin-2-yl)-1H-benzo[d]imidazole (7f).30
White solid, (0.226mg, 79% yield). 1H NMR (400 MHz,
CDCl3) δ 8.50 (d, J = 4.72 Hz, 1H), 8.33 (d, J = 8.0 Hz, 1H),
7.77 (d, J = 8.08 Hz, 1H), 7.69 (t, J = 7.92 Hz, 1H), 7.25-7.05
(m, 9H), 6.08 (s, 2H); 13C NMR (100 MHz, CDCl3) δ 150.6,
2-(pyridin-2-yl)-1H-benzo[d]imidazole (5h).17c Yellow
1
solid, (0.176mg, 90% yield). H NMR (400 MHz, DMSO-d6) δ
13.10 (s, 1H), 8.72 (d, J = 4.68 Hz, 1H), 8.33 (d, J = 7.88 Hz,
1H), 7.99 (dt, J = 7.76 Hz, 1.48 Hz, 1H), 7.70 (d, J = 7.6 Hz,
1H), 7.56-7.50 (m, 2H), 7.26-7.19 (m, 2H); 13C NMR (100
MHz, DMSO-d6) δ 150.8, 149.4, 148.5, 143.9, 137.6, 134.9,
124.7, 123.2, 121.9, 121.4, 119.3, 112.1.
2-(4-bromophenyl)-1H-benzo[d]imidazole (5i).17c Yel-
1
low solid, (0.219mg, 80% yield). H NMR (400 MHz, DMSO-
d6) δ 12.99 (s, 1H), 8.12 (d, J = 8.48 Hz, 2H), 7.76 (d, J = 8.48
Hz, 2H), 7.67 (d, J = 6.96 Hz, 1H), 7.53 (d, J = 6.84 Hz, 1H),
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The Journal of Organic Chemistry
7.22 (s, 2H). 13C NMR (100 MHz, DMSO-d6) δ 150.2, 143.7,
135.0, 132.0, 129.4, 128.4, 123.3, 122.8, 121.9, 119.0, 111.4.
Hz, 3H); 13C NMR (100 MHz, CDCl3) δ 155.8, 138.7, 122.2,
114.7, 31.8, 29.5, 29.4, 29.1, 28.5, 22.7, 14.1.
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2-(4-chlorophenyl)-1H-benzo[d]imidazole
White solid, (0.187mg, 82% yield). 1H NMR (400 MHz,
DMSO-d6) δ 12.99 (s, 1H), 8.19 (d, J = 8.4 Hz, 2H), 7.62 (d, J
= 8.56 Hz, 4H), 7.23-7.20 (m, 2H); 13C NMR (100 MHz,
DMSO-d6) δ 150.2, 143.7, 134.6, 129.1, 129.1, 128.2, 122.7,
122.1, 119.0, 111.5.
(5J).17c
ASSOCIATED CONTENT
Supporting Information
The Supporting Information is available free of charge on the
ACS Publications website
1
Copies of the H NMR, 13C NMR of all the com-
2-(4-fluorophenyl)-1H-benzo[d]imidazole (5k).17c Yel-
low solid, (0.151mg, 71% yield). 1H NMR (400 MHz, DMSO-
d6) δ 12.92 (s, 1H), 8.25-7.21 (m, 2H), 7.67 (d, J = 7.24 Hz, 1H),
7.53 (d, J = 7.28 Hz, 1H), 7.40 (t, J = 8.88 Hz, 2H), 7.24-7.17
(m, 2H). 13C NMR (100 MHz, DMSO-d6) δ 162.6 (d, J=246
Hz), 150.4, 143.8, 135.0, 128.7 (d, J=9 Hz), 126.8 (d, J=3 Hz),
122.6, 121.7, 118.9, 116.0 (d, J=22 Hz), 111.3.
pounds and HRMS, IR and crystallographic data of 1.
MS analysis of the crude reaction mixture of o-phe-
nylenediamine and 4-methoxybenzyl alcohol (PDF)
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55
56
57
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60
X-ray crystallographic data (CCDC 1831616) for 1
(CIF)
AUTHOR INFORMATION
2-(2,5-difluorophenyl)-1H-benzo[d]imidazole
(5l).17f
1
Corresponding Author
Orange liquid, (0.143mg, 62% yield). H NMR (400 MHz,
DMSO-d6) δ 12.70 (s, 1H), 8.00-7.96 (m, 1H), 7.66 (s, 2H),
7.54-7.48 (m, 1H), 7.44-7.39 (m, 1H), 7.26-7.24 (m, 2H); 13C
NMR (100 MHz, DMSO-d6) δ 158.3 (dd, J= 239 Hz, 2 Hz),
155.9 (d, J= 245 Hz, 2 Hz), 145.3 (t, 3 Hz), 122.8-122.3 (m),
119.5 (dd, J=14.5, 9Hz), 118.7, 118.6, 118.6, 118.5, 118.5,
118.4, 118.3, 118.2, 115.8 (dd, J= 23 Hz, 3Hz).
*E-mail: dsrimani@iitg.ernet.in
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENT
Financial support from SERB, DST (ECR/2016/000108) and DST-
INSPIRE (IFA-14-CH-143) are gratefully acknowledged. We
would also like to thank CIF and the Department of Chemistry, IIT-
Guwahati, for the instrumental facilities, infrastructural support and
startup grant. K.D and A.M are thankful to the institute for their
fellowship.
5-methyl-2-(p-tolyl)-1H-benzo[d]imidazole
(5m).32
White solid, (0.162mg, 74% yield). 1H NMR (400 MHz, CDCl3)
δ 7.99 (d, J = 8.08 Hz, 2H), 7.48 (d, J = 7.56 Hz, 1H), 7.34 (s,
1H), 7.17 (d, J = 8.0 Hz, 2H), 7.03 (d, J = 8.24 Hz, 1H), 2.42 (s,
3H), 2.33 (s, 3H); 13C NMR (150 MHz, DMSO-d6) δ 151.2,
139.5, 131.3, 129.6, 127.6, 126.5, 126.4, 123.5, 117.9, 111.3,
21.4, 21.1.
REFERENCES
2-(4-chlorophenyl)-5-methyl-1H-benzo[d]imidazole
(5n).32 White solid, (0.180mg, 74% yield). 1H NMR (400 MHz,
DMSO-d6) δ 8.16 (d, J = 8.12 Hz, 2H), 7.60 (d, J = 8.08 Hz,
2H), 7.51-7.31 (m, 2H), 7.03 (d, J = 6.96 Hz, 1H), 2.42 (s, 3H);
13C NMR (100 MHz, DMSO-d6) δ 149.8, 141.9, 135.3, 134.3,
132.1, 129.2, 129.0, 128.0, 123.5, 118.6, 111.1, 21.3.
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5-methyl-2-(thiophen-2-yl)-1H-benzo[d]imidazole
(5o).24 White solid, (0.148mg, 69% yield). 1H NMR (400
MHz, DMSO-d6) δ 12.79 (s, 1H), 7.81 (d, J = 3.24 Hz, 1H),
7.69 (d, J = 4.8 Hz, 1H), 7.47-7.29 (m, 2H), 7.21 (t, J = 4.72
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ole (5p).32 White solid, (0.223mg, 76% yield). HNMR (400
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7.78 (s, 2H), 7.11 (d, J = 8.88 Hz, 2H), 3.83 (s, 3H). 13C NMR
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8.28 (d, J = 7.92 Hz, 1H), 7.96 (dt, J= 7.56 Hz, 1.52 Hz 1H),
7.46 (t, J = 6.16 Hz, 2H), 7.31 (s, 1H), 2.31 (s, 6H); 13C NMR
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