Benzimidazoles from Aryl Alkyl Ketones and 2-Amino Anilines by an Iodine Catalyzed Oxidative C(CO)-C(alkyl) Bond Cleavage

Article abstract of DOI:10.1021/acs.joc.7b00165

Novel molecular iodine catalyzed cyclization reactions of 2-amino anilines with aryl alkyl ketones under oxidant and metal-free conditions are described. The reaction likely involves sequential C-N bond formation followed by C(CO)-C(alkyl) bond cleavage. Various 2-substituted benzimidazoles are obtained in moderate to good yields in a single step from readily available acetophenones, propiophenones, and phenylacetophenones.

Full text of DOI:10.1021/acs.joc.7b00165

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Note
Benzimidazoles from Aryl Alkyl Ketones and 2-Amino Anilines
by an Iodine Catalyzed Oxidative C(CO)-C(alkyl) Bond Cleavage
Owk Ravi, Altab Shaikh, Atul Upare, Kiran Kumar Singarapu, and Surendar Reddy Bathula
J. Org. Chem., Just Accepted Manuscript • DOI: 10.1021/acs.joc.7b00165 • Publication Date (Web): 05 Apr 2017
Downloaded from http://pubs.acs.org on April 6, 2017
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Benzimidazoles from Aryl Alkyl Ketones and 2ꢀAmino
Anilines by an Iodine Catalyzed Oxidative C(CO)−C(alkyl)
9
Bond Cleavage
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Owk Ravi,a Altab Shaikh,a Atul Upare,a Kiran Kumar Singarapub and
Surendar Reddy Bathula*a
aDivision of Natural Products Chemistry, CSIRꢀIndian Institute of Chemical Technology,
Hyderabad 500607, India
bCentre for Nuclear Magnetic Resonance, CSIRꢀIndian Institute of Chemical Technology,
Hyderabad, 500 007, India.
Eꢀmail: bsreddy@iict.res.in
RECEIVED DATE (to be automatically inserted after your manuscript is accepted if
required according to the journal that you are submitting your paper to)
O
I2 (10 mol%)
DMSO
R
NH2
NH2
N
R1
R
+
Na2SO4
N
H
R1
120 o
C
R
(41 examples)
ABSTRACT: A novel molecular iodine catalyzed cyclization reactions of 2ꢀamino anilines with
aryl alkyl ketones under oxidant and metal free conditions are described. The reaction likely
involves, sequential CꢀN bond formation followed by C(CO)ꢀC(alkyl) bond cleavage. Various 2ꢀ
substituted benzimidazoles are obtained in moderate to good yields in single step from readily
available acetophenones, propiophenones and phenylacetophenones.
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KEYWORDS: Benzimidazoles, CꢀC bond cleavage, Iodine catalysis, Acetophenones.
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Benzimidazoles represent an important and abundant class of dinitrogen containing fused
heterocycles. Compounds that contain the benzimidazoles motif are acclaimed for their
widespread applications as enzyme inhibitors, drugs, dyes and polymers.1 Moreover, huge
market of commercially available benzimidazole based drugs (esomeprazole, lansoprazole,
rabeprazole, telmisartan, bendazol and bendamustine) signifies the need to develop new,
economical and more environment friendly synthetic methods.
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O
Ar
X
X = H or OH or Cl or OR
1
h
t
a
Ar
X
Previous work
P
X = H or NH2 or OH
H
N
2
NH2
h
t
a
P
Ar
X = CN or COMe or
COOMe or COAr
N
NH2
R1
R1
O
X
This Work
Ar
R = H or Me or Ph
O
R
Ar
Scheme 1. Different Pathways for the Synthesis of Benzimidazoles by Using 1,2ꢀDiaminoarenes
Generally, these bicyclic compounds are prepared through the condensation of 1,2ꢀ
diaminoarenes with carboxylic acids2 , carboxylic acid derivatives3 and aldehydes4 (Scheme 1,
path 1) under oxidative conditions. Benzylalcohol5 or amine6 or methylarene7 (Scheme 1, path 2)
are also employed as substrates in the place of above carbonyls. Most of the above reactions
require harsh conditions, use of expensive, airꢀsensitive and toxic reagents. Further βꢀdiketones8,
βꢀketo nitriles9 and keto esters10 (Scheme 1, path 3) have also been used for the synthesis of
benzimidazoles. On the other hand, readily available aryl alkyl ketones are underutilized. This
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could be due to the involvement of challenging C(CO)ꢀC(alkyl) bond cleavage reaction. In
continuation of our previous work on the oxidative CꢀC bond cleavage,11 herein we report the
synthesis of the title compounds from more simpler and readily available aryl alkyl ketones.
Our previous work
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(A). Oxidative annulation
O
ref. 12
I2 (2 mmol),
I2 (10 mol%)
HO
N
N
Ar
2a
O
(B). Oxidative C-C bond cleavage
ref. 11a
Ph
O
DMSO,
100 -120 oC,
H
N
2a
Ar
H2N
N
I2 (10 mol%)
I2 (30 mol%)
This work
(C). Concomitant oxidative C-C
bond cleavage and annulation
Scheme 2. Design of Present Approach Based on our Previous Findings
Earlier, we have reported the synthesis of pyrazines and quinoxalines by utilizing
stoichiometric quantity of molecular iodine (2 equiv.) through the (CO)ꢀC bond oxidative
cyclization (Scheme 2A) from aryl methyl ketones, wherein αꢀketoaldehydes were generated in
situ.12 Interestingly, our subsequent research revealed that the use of catalytic amount of iodine
on similar substrates lead to the oxidative CꢀC bond cleavage (Scheme 2B) for benzoic acids and
benzamides.11a This work led us to explore the synthesis of benzimidazoles via iodine catalysed
concomitant oxidative CꢀC bond cleavage and annulation (Scheme 2C) of aryl alkyl ketones and
oꢀphenylenediamines.
To initiate our study, the test reaction between acetophenone (1a, 1 mmol) and 2ꢀamino aniline
o
(2a, 1 mmol) was carried out in the presence of iodine (0.1 mmol) in DMSO at 100 C. As
expected, the above combination of reagents gave desired product (3a), but in low yields (20%)
(entry 1 in Table 1). This can be attributed to possible chemical equilibrium during imine
formation and can be resolved by adding desiccants to the reaction mixture.
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Table 1: Optimization of the Reaction Conditions
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N
O
NH2
NH2
conditions
N
H
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3a
1a
2a
s. no. catalyst
(mol %)
solvent drying agent
yieldb
(%)
temp
(oC)
time
(h)
1
2
3
I2 (10)
I2 (10)
DMSO
DMSO
---
100
100
24
20
40
Na2SO4
24
I2 (20)
I2 (30)
I2 (10)
I2 (10)
DMSO
DMSO
Na2SO4
Na2SO4
Na2SO4
Na2SO4
100
100
24
24
41
42
4
5
DMSO
110
12
63
6
DMSO
120
12
70
7
I2 (10)
I2 (10)
DMSO
DMF
Na2SO4
Na2SO4
130
120
12
24
71
trace
8
9
I2 (10)
I2 (10)
dioxane
CH3CN
Na2SO4
Na2SO4
120
120
24
24
n.r.
n.r.
10
a Reaction conditions: 1 mmol of 1a and 1 mmol of 2a in the presence of
catalyst and dehydrating agent in solvent (6 mL) at 120 °C for 12 h in air.
b Isolated yields.
We have tried magnesium sulfate, molecular sieves and sodium sulfate to disrupt the equilibrium
and it was observed that addition of 5 mmol of Na2SO4, improved the yield of 3a to 40% (entry
2). Besides increase in the catalyst loading did not show any significant improvement on the
o
o
yield of 3a at 100 C (entries 3 & 4). However, increase in temperature to 110 and 120 C with
0.1 mmol of iodine furnished 3a in 63% and 70% yield in 12 h time respectively (entries 5 & 6).
Furthermore, additional increase of temperature did not improve the yield of the products (entry
7). On the other hand change of solvents to dioxane, CH3CN or DMF was also not advantageous
(entries 8ꢀ10) to improve the yield. With the optimized conditions (entry 6 in Table 1) in hand,
we next evaluated the generality of the method (Table 2). We first studied the reaction of
different substituted acetophenones. Various functional groups as in alkyl products 3d (72%), 3h
(76%), alkoxyl products 3i (85%), 3u (74%), 3y (73%), 3ab (70%), halogen products 3k (65%),
3n (68%), 3p (68%), 3s (65%), 3v (62%), 3aa (67%), trifluoromethyl product 3r (62%) and
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nitro products 3q (61%), and 3t (60%) were tolerated under the optimized conditions. It is
noteworthy that aryl methyl ketones bearing electronꢀdonating groups were found to give better
results than those with electronꢀwithdrawing groups (Table 2). To our delight, some of the fused
acetophenones (α/βꢀacetyl naphthalenes) and heteroaromatic ketone (2ꢀacetylthiophene) also
resulted the corresponding products 3aeꢀ3ah with 65ꢀ78% yield. Unprotected functional groups
like amine (3ai), hydroxyl(3aj), nitrile (3ak), ester (3al), acid (3am) containing acetophenones
were also tolerated under standard condition to give desired products in low to moderate yields
(25ꢀ50%).
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Expanding the scope of the reaction, different oꢀphenylenediamines were employed in this
reaction. Methyl substituted benzeneꢀ1,2ꢀdiamine reacts with both electronꢀ rich and poor
aryl/heteroaryl methyl ketones afforded the products in good yields (Table 2, 3b, 3l, 3o, 3x, 3z &
3ah, 58ꢀ68%). Furthermore oꢀphenylenediamine bearing electronꢀwithdrawing groups like 4ꢀ
flouro & 4ꢀchloro oꢀphenylenediamine produced products 3f (55%) and 3e (58%) in good yields.
Additionally 4, 5 dichloroꢀsubstituted oꢀphenylenediamine furnished the product 3ac in 52%
yield. Surprisingly, benzoyl substituted oꢀphenylenediamine gave very low yield with electronꢀ
rich acetophenones 3c (44%), 3g (35%), 3j (40%), 3m (35%), 3w (32%), and no product formed
with electron deficient substrates. Interestingly, diaminomaleonitrile offered corresponding
imidazole 3ad in 50% yield.
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Table 2. Synthesis of Various Benzimidazoles from Aromatic Ketones and oꢀ
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Phenylenediaminesa
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O
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I2 (10mol%)
DMSO
Na2SO4
H2N
H2N
H
N
R1
R1
R
air
open
120 o
R
N
1
2
C
3
H
N
R1
H
N
R1
R
N
N
R = H & R1 = H
(3a, 70%)
R
gramꢀscale: 68%
R= H & R1 = CH3 (3b, 68%)
R= H & R1 = Bz (3c, 44%)
R= CH3 & R1 = H (3d, 72 %)
R= CH3 & R1= Cl (3e, 58%)
R= CF3 & R1 = H (3r, 62%)
3s
R= Br & R1 = H
( , 65%)
R= NO2 & R1 = H (3t, 60%)
H
R1
3f
(
R= CH3 & R1= F
, 55%)
N
R= CH3 & R1= Bz (3g, 35%)
R= tꢀBu & R1 = H (3h, 76%)
R= OMe & R1 = H (3i, 85%)
R= OMe & R1= Bz (3j, 40%)
N
R
R= OMe & R1 = H (3u, 74%)
3v
R= Cl & R1 = H
R= Cl & R1 = Bz (3w, 32%)
(
, 62%)
3k
, 65%)
R= F & R1 = H
(
R= F & R1= CH3 (3l, 58%)
R= F & R1 = Bz (3m, 35%)
H
R1
N
R= Cl & R1= H
R= Cl & R1= CH3 (3o, 68%)
3p
, 68%)
(3n, 68%)
R
N
R= Br & R1= H
(
R
R= NO2 & R1 = H (3q, 61%)
R= OMe & R1 = CH3 (3x, 68%)
H
R1
MeO
N
H
N
R
N
MeO
N
R
R= OMe & R1= H
(3y, 73%)
R= OMe & R1 = CH3 (3z, 58%)
MeO
(3ab,70%)
R= Cl & R1 = H
(3aa, 67%)
N
H
N
R
)
(3ae, 68%
N
H
N
R
3ac
R= Cl (
R= CN (
,52%)
,50%)
R
N
3ad
N
S
H
N
R= H (3ag, 78%)
R= CH3 (3ah, 65%)
N
H
69%)
(3af,
R= NH2
(3ai,30%)
H
N
3aj
(3ak, 50%)
R= OH
R= CN
(
, 35%)
R
R= COOMe (3al, 45%)
R= COOH (3am, 25%)
N
a
1
2
Reaction conditions: 1 mmol of and 1 mmol of , I2 (10 mol %) and
Na2SO4 (5 mmol) in DMSO at 120 °C for 12 h in air.
Aforementioned results prompted us to test the fate of the more challenging aryl higher
alkyl/benzyl ketones (4aꢀ4j) in place of preceding methyl ketones under the standard conditions
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Table 3. Synthesis of Benzimidazoles from Aryl Alkyl/Benzyl Ketones and oꢀ
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Phenylenediaminesa
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O
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I2 (10mol%)
DMSO
H
N
H2N
Alkyl/Aryl
R1
R1
R
Open Air
H2N
R
N
120 o
C
4 (a-j)
2
3
Product
R1
H
Substrate
O
R1
Substrate
Product
O
H
3a,
(
63%)
68%)
3a,
(
82%)
88%)
4a
4f
O
OMe
H
O
H
3d,
(
3i,
(
4b
4g
O
MeO
O
O
3a,
3i,
(
(
40%)
48%)
3i,
(
75%)
H
4c
H
H
MeO
4h
O
O
3a,
3p,
(
(
41%)
44%)
MeO
Br
3an,
(
62%)
60%)
4-Me
4-Me
4d
4i
Br
H
O
Br
3i,
3p,
(
(
46%)
44%)
3ao,
(
4e
4j
Br
MeO
a Reaction conditions: 1 mmol of 1 and 1 mmol of 2a, I2 (10 mol %) and Na2SO4 (5 mmol)
in DMSO at 120 °C for 12 h in air.
(Table 3). To our delight, propiophenone and its derivatives reacted well to produce
corresponding benzimidazoles (3a, 3d, 3i, 3an, 3ao) in good yields (60 to 75%). In the case of
aryl benzyl ketones, interestingly both ends of the substrate were converted to the corresponding
benzimidazoles. In particular, both ends of symmetrically substituted aryl benzyl ketones 4f and
4g were converted to single benzimidazole 3a and 3i respectively in 82% & 88% yield (Note: the
product was more than one mmol from one mmol of starting material). Whereas aryl benzyl
1
ketones with distinct substitutions (4hꢀj) produced two different benzimidazoles. An H NMR
study during the course of the reaction also indicated the formation of second benzimidazole
adduct from benzylic terminal (as shown in Figure S1). Moreover, no other byꢀproduct from this
benzyl terminal was observed. Moving forward, we have tested the scalability of the method by
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conducting the reaction in gram scale. Under the standard conditions 1g of 1a has produced
1.09g of 3a with 68% yield.
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Before proposing the mechanism, some control experiments (Scheme S1) were conducted to rule
out the formation of phenacyl iodide or phenylglyoxal as intermediates. We then propose a
possible mechanism as shown in scheme 3. The reaction starts with the Schiff base (A) formation
followed by cyclization to obtain dihydro benzimidazole (B). Intermediate "B" undergoes
iodinate on followed by oxidation13 to produce its oxo derivative ''C'', which was detected in the
2
Na2SO4
O
Na2SO4. nH2O
Ar
Ar
1
N
NH2
N
A
Ar
N
H
3
S
M
D
H
N
Ar
O
S
M
D
H
N
I2
Ar
NH
HI
B
N
H
H
O
C
Scheme 3. Proposed Mechanism
1H NMR spectrum of a crude product (Figure S2). Subsequently, aromatization of “C" with the
loss of formaldehyde produces 2ꢀaryl benzimidazole product 3.
CONCLUSION
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In summary, we have demonstrated a facile synthetic method to convert aryl alkyl
ketones to benzimidazoles for the first time via C (sp2)–C bond cleavage. The reaction is
executed by a catalytic amount of iodine under metal free conditions. Some control experiments
and NMR studies were carried out to support the mechanism. This method constitutes a simple
and inexpensive route to obtain 2ꢀaryl substituted benzimidazoles which are of great importance
in medicinal chemistry.
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EXPERIMENTAL SECTION:
Reactions were monitored by thinꢀlayer chromatography carried out on silica plates using
UVꢀlight, and Ninhydrin for visualization. Column chromatography was performed on silica gel
(60–120 mesh) using hexane and ethyl acetate as eluents. Evaporation of solvents was done
under reduced pressure at temperature less than 40 °C. IR spectra were recorded as neat
1
13
compound. H and C NMR spectra were recorded in CDCl3 and DMSOꢀd6 solvents on a 300
MHz and 500 MHz spectrometer. Chemical shifts δ and coupling constants J are given in ppm
(parts per million) and Hz (hertz) respectively. Chemical shifts are reported relative to residual
1
solvent as an internal standard for H and 13C (CDCl3: δ 7.26 ppm for 1H, and 77.0 ppm for 13C,
DMSOꢀd6: δ 2.50 ppm for 1H, and 39.5 ppm for 13C). HRMS data were recorded by electrospray
ionization with a QꢀTOF mass analyzer. Melting points were measured on micro melting point
apparatus. Commercially available substituted acetophenones, iodine and DMSO were used
without further purification.
General procedure for the synthesis of Benzimadazoles from acetophenones(A) : mixture
of acetophenone (1 equiv), benzeneꢀ1, 2ꢀdiamine (1 equiv), iodine (10 mol %) and sodium
sulphate (5 equiv) in DMSO (10 mL) was stirred at 120 °C under open air for the appropriate
time (Table 1). After completion of the reaction, as indicated by TLC, the mixture was diluted
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with water and filtered. The filtrate was extracted with EtOAc (4×15 mL) and extract was
washed with brine, drying over Na2SO4 and evaporation, the crude product was purified by
column chromatography on silica gel (eluent: petroleum ether/EtOAc) to afford the
product.Characterization data for new compounds is given below.
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2ꢀphenylꢀ1Hꢀbenzo[d]imidazole (3a):6a According to general procedure, 1a (120 mg, 1 mmol)
1
gave 3a (135 mg, 70%) as a white solid. Rf = 0.3 (EtOAc/hexanes, 3:7); m.p. 290 ꢀ 292 ºC; H
NMR (300 MHz, DMSO ꢀ d) δ: 12.9 (bs, 1H), 8.18 (d, J = 7.04 Hz, 2H), 7.62 ꢀ 7.51 (m, 5H),
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7.22 ꢀ 7.19 (m, 2H) ppm; C NMR (75 MHz, DMSO ꢀ d) δ: 151.1, 130.0, 129.8, 128.9, 126.4,
122.1, 115.1, 115.0 ppm; IR (KBr) ν: 2940, 1219.8, 1378.0, 1167.0, 772.5 cm–1; MS (EI) m/z
195 [M+1]+.
5ꢀmethylꢀ2ꢀphenylꢀ1Hꢀbenzo[d]imidazole (3b):6a According to general procedure, 1a (120 mg, 1
mmol) gave 3b (140 mg, 68%) as a white solid. Rf = 0.3 (EtOAc/hexanes, 3:7); m.p. 240 ꢀ 242
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ºC; H NMR (300 MHz, DMSO ꢀ d) δ: 8.15 (d, J = 7.01 Hz, 2H), 7.56 ꢀ 7.44 (m, 4H), 7.37 (s,
13
1H), 7.02 (d, J = 8.15 Hz, 1H), 2.42 (s, 3H) ppm; C NMR (75 MHz, DMSO ꢀ d) δ: 150.9,
138.9, 138.7, 131.3, 130.2, 129.7, 128.9, 126.3, 123.6, 114.6, 114.4, 21.3 ppm; IR (KBr) ν:
2922.0, 1412.1, 1219.6, 1057.0, 772.6 cm–1; MS (EI) m/z 209 [M+1] +.
phenyl(2ꢀphenylꢀ1Hꢀbenzo[d]imidazolꢀ5ꢀyl)methanone (3c):6a According to general procedure,
1a (120 mg, 1 mmol) gave 3c (131 mg, 44%) as a white solid. Rf = 0.3 (EtOAc/hexanes, 3:7);
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m.p. 222 ꢀ 224 ºC; H NMR (300 MHz, DMSO ꢀ d) δ: 13.3 (bs, 1H), 8.21 (d, J = 6.56 Hz, 2H),
7.96 (bs, 1H), 7.78 ꢀ 7.60 (m, 5H), 7.60 ꢀ 7.55 (m, 5H); 13C NMR (75 MHz, DMSO ꢀ d) δ: 195.5,
138.0, 132.0, 131.0, 130.4, 129.4, 129.3, 129.0, 128.3, 126.7; IR (KBr) ν: 3012.5, 1641.0,
1317.7, 1216.2, 772.8 cm–1; MS (EI) m/z 299 [M+1] +.
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2ꢀ(pꢀtolyl)ꢀ1Hꢀbenzo[d]imidazole (3d):6a According to general procedure, 1b (134 mg, 1 mmol)
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gave 3d (149 mg, 72%) as a white solid. Rf = 0.3 (EtOAc/hexanes, 3:7); m.p. 274 ꢀ 276 ºC; H
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NMR (300 MHz, DMSO ꢀ d) δ: 12.82 (bs, 1H), 8.05 (d, J = 8.10 Hz, 2H), 7.63 (d, J = 6.90 Hz,
1H), 7.50 (d, J = 6.90 Hz, 1H), 7.34 (d, J = 7.97 Hz, 2H), 7.20 ꢀ 7.11(m, 2H), 2.37 (s, 3H) ppm;
13C NMR (75 MHz, DMSO ꢀ d) δ: 151.3, 139.5, 129.4, 127.4, 126.3, 122.0, 121.86, 121.80, 20.9
ppm; IR (KBr) ν: 2944.2, 1219.7, 892.2, 772.5 cmꢀ1; MS (EI) m/z 209 [M +1] +.
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6ꢀchloroꢀ2ꢀpꢀtolylꢀ1Hꢀbenzo[d]imidazole (3e):4a According to general procedure, 1b (134 mg, 1
mmol) gave 3e (140 mg, 58%) as a off white solid. Rf = 0.3 (EtOAc/hexanes, 3:7); m.p. 230 –
232 ºC; 1H NMR (300 MHz, DMSO ꢀ d) δ: 13.03 (s, 1H), 8.05 (d, J = 8.1 Hz, 3H), 7.58 (s, 2H),
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7.36 (d, J = 8.0 Hz, 2H), 7.21 (dd, J = 8.5, 1.7 Hz, 1H), 2.38 (s, 3H) ppm; C NMR (75 MHz,
DMSO ꢀ d) δ: 152.9, 140.1, 129.6, 126.9, 126.5, 126.3, 122.2, 21.2 ppm; MS (EI) m/z 243
[M+1] +.
6ꢀfluoroꢀ2ꢀpꢀtolylꢀ1Hꢀbenzo[d]imidazole (3f):14a According to general procedure, 1b (134 mg, 1
mmol) gave 3f (124 mg, 55%) as a white solid. Rf = 0.3 (EtOAc/hexanes, 3:7)); m.p. 232 ꢀ
234ºC; 1H NMR (300 MHz, DMSO ꢀ d) δ: δ 12.95 (s, 1H), 8.05 (d, J = 8.0 Hz, 2H), 7.56 (s, 1H),
7.36 (d, J = 7.9 Hz, 3H), 7.11 – 6.96 (m, 1H), 2.37 (s, 3H) ppm; 13C NMR (75 MHz, DMSO ꢀ d)
δ: 126 MHz, CDCl3) δ 159.5, 157.6, 152.8, 139.8, 129.5, 129.5, 127.1, 126.3, 110.0, 20.1 ppm;
MS (EI) m/z 227 [M+1] +.
Phenyl(2ꢀ(pꢀtolyl)ꢀ1Hꢀbenzo[d]imidazolꢀ5ꢀyl)methanone(3g):14b According to general procedure,
1b (134 mg, 1 mmol) gave 3g (107 mg, 35%) as a white solid. Rf = 0.3 (EtOAc/hexanes, 3:7);
m.p. 233 ꢀ 235 ºC; 1H NMR (300 MHz, DMSO ꢀ d) δ: 13.21 (bs, 1H), 8.09 (d, J = 8.08 Hz, 2H),
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7.94 (bs, 1H), 7.77 ꢀ 7.55 (m, 7H), 7.39 (d, J = 7.39 Hz, 2H), 2.39 (s, 3H) ppm; C NMR (75
MHz, DMSO ꢀ d) δ: 195.5, 140.3, 138.1, 131.9, 130.8, 129.5, 129.3, 128.3, 126.7, 126.6, 124.0,
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20.9 ppm; IR (KBr) ν: 3101.2, 1646.1, 1443.8, 1317.8, 1218.8, 826.9, 771.8 cm–1; MS (EI) m/z
313 [M+1] +.
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2ꢀ(4ꢀ(tertꢀbutyl)phenyl)ꢀ1Hꢀbenzo[d]imidazole (3h):14c According to general procedure, 1c (176
mg, 1 mmol) gave 3h (190 mg, 76%) as a white solid. Rf = 0.3 (EtOAc/hexanes, 3:7); m.p. 256 ꢀ
258 ºC; 1H NMR (300 MHz, DMSO ꢀ d) δ: 12.83 (bs, 1H), 8.11 (d, J = 8.38 Hz, 2H), 7.64 (d, J =
7.60 Hz, 1H), 7.56 (d, J = 8.39 Hz, 2H), 7.51 (d, J = 6.98 Hz, 1H), 7.22 ꢀ 7.14 (m, 2H), 1.33(s,
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9H) ppm; C NMR (75 MHz, DMSO ꢀ d) δ: 152.4, 151.2, 143.8, 134.9, 127.4, 126.1, 125.6,
122.2, 121.04, 118.6, 111.1, 34.5, 30.9 ppm; IR (KBr) ν: 2962.8, 1430.3, 1362.9, 1211.2, 966.0,
770.7 cm–1; MS (EI) m/z 251 [M+1] +.
2ꢀ(4ꢀmethoxyphenyl)ꢀ1Hꢀbenzo[d]imidazole (3i):6a According to general procedure, 1d (150 mg,
1 mmol) gave 3i (189 mg, 85%) as a white solid. Rf = 0.3 (EtOAc/hexanes, 7:3); m.p. 224 ꢀ 226
ºC; 1H NMR (300 MHz, DMSO ꢀ d) δ: 12.70 (bs, 1H), 8.10 (d, J = 8.86 Hz, 2H), 7.62 ꢀ 7.47 (m,
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2H), 7.18 ꢀ 7.09 (m, 4H), 3.83 (s, 3H) ppm; C NMR (75 MHz, DMSO ꢀ d) δ: 160.5, 151.3,
143.8, 143.7, 134.9, 127.9, 121.4, 118.4, 114.3, 110.9, 55.3 ppm; IR (KBr) ν: 2944.2, 2392.0,
1612.6, 1513.2, 1388.6, 1252.4, 1177.6, 1031.6, 838.5, 772.4 cm–1; MS (EI) m/z 225 [M+1] +.
(2ꢀ(4ꢀmethoxyphenyl)ꢀ1Hꢀbenzo[d]imidazolꢀ5ꢀyl)(Phenyl)methanone (3j):14d According to
general procedure, 1d (150 mg, 1 mmol) gave 3j (130 mg, 40%) as a white solid. Rf = 0.2
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(EtOAc/hexanes, 3:7); m.p. 190 ꢀ 192 ºC; H NMR (300 MHz, DMSO ꢀ d) δ: 13.14 (d, J = 17.8
Hz, 1H), 8.14 (d, J = 8.84 Hz ,2H), 7.86ꢀ7.54 (m, 8H), 7.13 (d, J = 8.70 Hz, 2H), 3.84 (s, 3H)
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ppm; C NMR (75 MHz, DMSO ꢀ d) δ: 195.4, 161.0, 154.5, 153.6, 147.4, 143.2, 138.2, 134.5,
131.9, 130.6, 129.3, 128.3, 124.2, 123.7, 121.9, 121.2, 118.1, 114.4, 113.8, 111.1, 55.3 ppm; IR
(KBr) ν: 3126.2, 1613.2, 1495.6, 1292.1, 1255.2, 1178.5, 1029.2, 834.5, 771.8 cm–1; MS (EI)
m/z 329 [M+1] +.
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2ꢀ(4ꢀfluorophenyl)ꢀ1Hꢀbenzo[d]imidazole (3k):6a According to general procedure, 1e (138
mg, 1 mmol) gave 3k (137 mg, 65%) as off white solid. Rf = 0.3 (EtOAc/hexanes, 3:7); m.p. 245
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ꢀ 247 ºC; H NMR (300 MHz, DMSO ꢀ d) δ: 12.90 (bs, 1H), 8.24ꢀ8.19 (m, 2H), 7.59 (bs, 2H),
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7.43ꢀ7.37 (m, 2H), 7.21ꢀ7.19 (m, 2H) ppm; C NMR (75 MHz,CDCl3 + DMSO ꢀ d) δ: 164.7,
161.4, 150.5, 139.0, 128.4, 128.3, 126.3, 126.2, 121.8, 115.4, 115.1, 114.6 ppm; IR (KBr) ν:
2998.0, 1612.6, 1496.0, 1436.2, 1218.8, 772.1 cm–1; MS (EI) m/z 213 [M+1] +.
2ꢀ(4ꢀfluorophenyl)ꢀ5ꢀmethylꢀ1Hꢀbenzo[d]imidazole (3l):4e According to general procedure, 1e
(138 mg, 1 mmol) gave 3l (130 mg, 58%) as a white solid. Rf = 0.4 (EtOAc/hexanes, 3:7); m.p.
180 ꢀ 182 ºC; 1H NMR (300 MHz, DMSO ꢀ d) δ: 8.21 ꢀ 8.16 (m, 2H), 7.47 (d, J = 8.17 Hz, 1H),
7.41 ꢀ 7.35 (m, 3H), 7.02 (d, J = 8.22 Hz, 1H), 2.42 (s, 3H) ppm; 13C NMR (75 MHz, DMSO ꢀ d)
δ: 164.6, 161.3, 150.1, 139.0, 138.0, 131.4, 128.7, 128.5, 126.96, 126.94, 123.6, 116.1, 115.8,
115.1, 114.4, 21.3 ppm; IR (KBr) ν: 2924.5, 1435.6, 1220.5, 922.0, 772.5 cm–1; MS (EI) m/z 227
[M+1] +.
(2ꢀ(4ꢀfluorophenyl)ꢀ1Hꢀbenzo[d]imidazolꢀ5ꢀyl)(phenyl)methanone (3m): According to general
procedure, 1e (138 mg, 1 mmol) gave 3m (110 mg, 35%) as a white solid. Rf = 0.3
(EtOAc/hexanes, 3:7); m.p. 238 ꢀ 240 ºC; 1H NMR (300 MHz, DMSO ꢀ d) δ: 13.3 (bs, 1H), 8.27ꢀ
8.22 (m, 2H), 8.00 ꢀ 7.65 (m, 6H), 7.60 ꢀ 7.57 (m, 2H), 7.44 (t, J = 8.98 Hz, 2H) ppm; 13C NMR
(75 MHz, DMSO ꢀ d) δ: 195.5, 165.0, 161.7, 138.0, 129.3, 129.0, 126.1, 116.2, 115.9 ppm; IR
(KBr) ν: 3126.3, 1618.2, 1489.3, 1319.9, 1225.5, 772.3 cm–1. HRMS (ESI) calcd for
C20H13FN2O [M + Na]+ 339.0904, found 339.0909.
2ꢀ(4ꢀchlorophenyl)ꢀ1Hꢀbenzo[d]imidazole (3n):6a According to general procedure, 1f (154 mg, 1
mmol) gave 3n (154 mg, 68%) as a white solid. Rf = 0.3 (EtOAc/hexanes, 3:7); m.p. 268 ꢀ 270
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ºC; H NMR (300 MHz, DMSO ꢀ d) δ: 13.00 (bs, 1H), 8.18 (d, J = 8.60 Hz, 2H), 7.62 (d, J =
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8.62 Hz, 4H), 7.23 ꢀ 7.20 (m, 2H) ppm; C NMR (75 MHz, DMSO ꢀ d) δ: 150.1, 143.7, 135.0,
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134.4, 129.0, 128.0, 121.8, 118.9, 111.3 ppm; IR (KBr) ν: 3119.0, 1442.1, 1403.3, 1216.2,
1051.9, 968.5, 743.7 cm–1; MS (EI) m/z 229 [M+1] +.
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2ꢀ(4ꢀchlorophenyl)ꢀ5ꢀmethylꢀ1Hꢀbenzo[d]imidazole (3o):14a According to general procedure, 1f
(154 mg, 1 mmol) gave 3o (163 mg, 68%) as a white solid. Rf = 0.4 (EtOAc/hexanes, 3:7); m.p.
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224 – 226 ºC; H NMR (300 MHz, DMSO ꢀ d) δ: 12.83 (d, J = 11.0 Hz, 1H), 8.15 (d, J = 8.43
Hz, 2H), 7.61 (d, J = 8.56 Hz, 2H), 7.52 ꢀ 7.31 (m, 2H), 7.03 (t, J = 8.54 Hz, 1H), 2.42 (s, 3H)
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ppm; C NMR (75 MHz, DMSO ꢀ d) δ: 149.8, 134.2, 131.6, 131.4, 129.1, 128.9, 127.9, 127.0,
123.7, 118.7, 118.6, 111.2 ,111.1, 21.3 ppm; IR (KBr) ν: 2997.3, 1445.3, 1311.6, 1219.6, 1053.0,
770.3, 731.9 cm–1; MS (EI) m/z 243 [M+1] +.
2ꢀ(4ꢀbromophenyl)ꢀ1Hꢀbenzo[d]imidazole (3p):14a According to general procedure, 1g (197 mg,
1 mmol) gave 3p (183 mg, 68%) as a off white solid. Rf = 0.3 (EtOAc/hexanes, 3:7); m.p. 255 ꢀ
257 ºC; 1H NMR (300 MHz, DMSO ꢀ d) δ: 8.12 (d, J = 8.53 Hz, 2H), 7.76 (d, J = 8.48 Hz, 2H),
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7.67 (d, J = 7.20 Hz, 1H), 7.53 (d, J = 6.83 Hz, 1H), 7.24 ꢀ 7.17 (m, 2H) ppm; C NMR (75
MHz, DMSO ꢀ d) δ: 150.1, 143.7, 134.9, 131.9, 129.3, 128.3, 123.3, 122.7, 121.8, 111.4 ppm; IR
(KBr) ν: 2939.0, 1436.0, 1216.2, 772.5 cm–1; MS (EI) m/z 273 [M+2] +.
2ꢀ(4ꢀnitrophenyl)ꢀ1Hꢀbenzo[d]imidazole (3q):14a According to general procedure, 1h (165 mg, 1
mmol) gave 3q (145 mg, 61%) as a light yellow solid. Rf = 0.3 (EtOAc/hexanes, 3:7); m.p. 262 ꢀ
264 ºC; 1H NMR (300 MHz, DMSO ꢀ d) δ: 8.45 ꢀ 8.35 (m, 4H), 7.61 ꢀ 7.64 (m, 2H),7.27 ꢀ 7.24
(m, 2H) ppm; 13C NMR (75 MHz, DMSO ꢀ d) δ: 149.0, 147.7, 139.6, 136.1, 130.0, 127.3, 124.2,
122.8, 122.6, 115.6 ppm; IR (KBr) ν: 2943.2, 1523.9, 1389.2, 1349.2, 772.3 cm–1; MS (EI) m/z
240 [M+1] +.
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2ꢀ(3ꢀ(trifluoromethyl)phenyl)ꢀ1Hꢀbenzo[d]imidazole (3r):6a According to general procedure, 1i
(188 mg, 1 mmol) gave 3r (162 mg, 62%) as a white solid. Rf = 0.3 (EtOAc/hexanes, 3:7); m.p.
209 ꢀ 211 ºC; 1H NMR (300 MHz, DMSO ꢀ d) δ: 13.17 (bs, 1H), 8.53 ꢀ 8.47 (m, 2H), 7.87 ꢀ 7.77
(m, 2H), 7.70 (d, J = 6.88 Hz, 1H), 7.57 (d, J = 7.05 Hz, 1H), 7.24 ꢀ 7.23 (m, 2H) ppm; 13C NMR
(75 MHz, DMSO ꢀ d) δ: 149.6, 143.6, 135.0, 131.1, 130.4, 130.1, 130.0, 129.6, 126.1, 125.8,
122.8, 122.7, 122.2, 121.9, 119.1, 111.5 ppm; IR (KBr) ν: 2963.2, 1405.8, 1328.4, 1165.7,
1128.7, 1074.7, 772.0 cm–1; MS (EI) m/z 263 [M+1] +.
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2ꢀ(3ꢀbromophenyl)ꢀ1Hꢀbenzo[d]imidazole (3s):14a According to general procedure, 1j (197 mg, 1
mmol) gave 3s (175 mg, 65%) as a white solid. Rf = 0.3 (EtOAc/hexanes, 3:7); m.p. 222 ꢀ 224
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ºC; H NMR (300 MHz, DMSO ꢀ d) δ: 13.30 (bs, 1H), 8.36 (s, 1H), 8.18 (d, J = 7.84 Hz, 1H),
7.70 ꢀ 7.67 (m, 2H), 7.55 ꢀ 7.49 (m, 2H), 7.27 ꢀ 7.18 (m, 2H) ppm; 13C NMR (75 MHz, DMSO ꢀ
d) δ: 149.5, 143.6, 134.9, 131.1, 128.8, 125.3, 122.2, 121.9, 119.0, 111.4 ppm; IR (KBr) ν:
2915.0, 1219.8, 1159.0, 772.4 cm–1; MS (EI) m/z 273 [M+2] +.
2ꢀ(3ꢀnitrophenyl)ꢀ1Hꢀbenzo[d]imidazole (3t):6a According to general procedure, 1k (165 mg, 1
mmol) gave 3t (143 mg, 60%) as a light yellow solid. Rf = 0.3 (EtOAc/hexanes, 3:7); m.p. 205 ꢀ
207 ºC; 1H NMR (300 MHz, DMSO ꢀ d) δ: 13.30 (bs, 1H), 9.01 (t, J = 1.76 Hz, 1H), 8.61 (d, J =
7.90 Hz, 1H), 8.33 (dd, J = 8.16,1.90 Hz, 1H), 7.85 (t, J = 8.08 Hz, 1H), 7.72 (d, J = 7.41 Hz,
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1H), 7.58 (d, J = 7.27 Hz, 1H), 7.32 ꢀ 7.21 (m, 2H) ppm; C NMR (75 MHz, DMSO ꢀ d) δ:
149.0, 148.3, 143.5, 135.0, 132.4, 131.7, 130.6, 124.1, 123.2, 122.1, 120.7, 119.2, 111.6 ppm; IR
(KBr) ν: 2954.0, 1523.9, 1389.0, 1349.2, 772.3 cm–1; MS (EI) m/z 240 [M+1] +.
2ꢀ(2ꢀmethoxyphenyl)ꢀ1Hꢀbenzo[d]imidazole (3u):15a According to general procedure, 1l (150
mg, 1 mmol) gave 3u (165 mg, 74%) as a white solid. Rf = 0.3 (EtOAc/hexanes, 3:7); m.p. 178 ꢀ
180 ºC; 1H NMR (300 MHz, DMSO ꢀ d) δ: 12.13 (bs, 1H), 8.35 ꢀ 8.33 (m, 1H), 7.64 ꢀ 7.61 (m,
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2H), 7.49 ꢀ 7.44 (m, 1H), 7.24 ꢀ 7.09 (m, 4H), 4.02 (s, 3H) ppm; 13C NMR (75 MHz, DMSO ꢀ d)
δ: 156.7, 148.9, 131.1, 129.7, 121.7, 120.8, 118.1, 112.0, 55.7 ppm; IR (KBr) ν: 2924.0, 1439.9,
1342.0, 1243.7, 886.0, 772.1 cm–1; MS (EI) m/z 225 [M+1] +.
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2ꢀ(2ꢀchlorophenyl)ꢀ1Hꢀbenzo[d]imidazole(3v):15a According to general procedure, 1m (154 mg,
1 mmol) gave 3v (141 mg, 62%) as a white solid. Rf = 0.4 (EtOAc/hexanes, 3:7); m.p. 231 ꢀ 233
ºC; 1H NMR (300 MHz, DMSO ꢀ d) δ: 12.71 (bs, 1H), 7.92 ꢀ 7.88 (m, 1H), 7.67 ꢀ 7.51 (m, 5H),
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7.24 ꢀ 7.23 (m, 2H) ppm; C NMR (75 MHz, DMSO ꢀ d) δ: 149.0, 132.0, 131.1, 130.3, 129.9,
127.3, 122.0, 119.0, 111.8, 111.7, 111.5 ppm; IR (KBr) ν: 2984.6, 1442.1, 1403.3, 1216.2,
1051.9, 968.5, 743.7 cm–1. MS (EI) m/z 229 [M+1] +.
2ꢀ(2ꢀchlorophenyl)ꢀ1Hꢀbenzo[d]imidazolꢀ5ꢀyl)(phenyl)methanone (3w): According to general
procedure, 1m (180 mg, 1 mmol) gave 3w (106 mg, 32%) as a white solid. Rf = 0.3
1
(EtOAc/hexanes, 3:7); m.p. 146 ꢀ 148 ºC; H NMR (300 MHz, DMSO ꢀ d) δ: 13.12 (bs, 1H),
8.00 (bs, 1H), 7.94 (d, J = 6.72 Hz, 1H), 7.78 ꢀ 7.66 (m, 6H), 7.61 ꢀ 7.51 (m, 4H) ppm; 13C NMR
(75 MHz, DMSO ꢀ d) δ: 195.6, 138.0, 132.1, 132.0, 131.6, 130.4, 129.4, 128.3, 127.5 ppm; IR
(KBr) ν: 3052.2, 1649.3, 1630.0, 1618.0, 1443.5, 1319.9, 1219.3, 1109.9, 1051.6, 851.1, 761.0
cm–1. HRMS (ESI) calcd for C20H13ClN2O [M + Na]+ 355.0609, found 355.0611.
2ꢀ(3,4ꢀdimethoxyphenyl)ꢀ5ꢀmethylꢀ1Hꢀbenzo[d]imidazole(3x):15b
According
to
general
procedure, 1n (180 mg, 1 mmol) gave 3x (182 mg, 68%) as a white solid. Rf = 0.2
(EtOAc/hexanes, 3:7); m.p. 203 ꢀ 205 ºC; 1H NMR (300 MHz, DMSO ꢀ d) δ: 12.60 (d, J = 10.37
Hz ,1H), 7.74 ꢀ 7.69 (m, 2H), 7.50 ꢀ 7.27 (m, 2H), 7.11 (d, J = 8.32 Hz, 1H), 3.87 (s, 3H), 3.82
13
(s, 3H), 2.42 ꢀ 2.40 (s, 3H) ppm; C NMR (75 MHz, DMSO ꢀ d) δ: 151.0, 150.1, 148.8, 123.3,
123.0, 122.9, 119.1, 118.0, 111.7, 111.0, 109.6, 55.5, 21.3 ppm; IR (KBr) ν: 2941.0, 1503.8,
1264.2, 1225.9, 1024.6, 768.4 cm–1; MS (EI) m/z 269 [M+1] +.
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2ꢀ(2,4ꢀdimethoxyphenyl)ꢀ1Hꢀbenzo[d]imidazole (3y):15d According to general procedure, 1o
(180 mg, 1 mmol) gave 3y (185 mg, 73%) as a off white solid. Rf = 0.3 (EtOAc/hexanes, 3:7));
m.p. 278 ꢀ 280 ºC; 1H NMR (300 MHz, DMSO ꢀ d) δ: 11.96 (bs, 1H), 8.25 (d, J = 8.66 Hz, 1H),
7.59 ꢀ 7.57 (m, 1H), 7.15 ꢀ 7.14 (m, 2H), 6.75 (d, J = 2.32 Hz, 1H), 6.71 (dd, J = 8.70, 2.39 Hz,
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1H) 3.85 (s, 3H) ppm; C NMR (75 MHz, DMSO ꢀ d) δ: 161.9, 158.0, 149.1, 130.8, 121.3,
115.1, 114.9, 114.8, 114.6, 114.4, 111.0, 106.2, 98.5, 55.8, 55.4 ppm; IR (KBr) ν: 2939.0,
1613.5, 1582.5, 1210.3, 769.05, 749.1 cm–1; MS (EI) m/z 255 [M+1] +.
2ꢀ(2,4ꢀdimethoxyphenyl)ꢀ5ꢀmethylꢀ1Hꢀbenzo[d]imidazole(3z):15c
According
to
general
procedure, 1o (180 mg, 1 mmol) gave 3z (155 mg, 58%) as a white solid. Rf = 0.2
(EtOAc/hexanes, 3:7); m.p. 203 ꢀ 205 ºC; 1H NMR (300 MHz, DMSO ꢀ d) δ: 11.97 (d, J = 10.66
Hz ,1H), 7.85 (s, 1H), 7.53 ꢀ 7.39 (m, 2H), 7.16 (d, J = 9.22 Hz, 1H), 7.03 (dd, J = 9.12, 3.18
Hz, 2H), 3.96 (s, 3H), 3.79 (s, 3H), 2.42 (s, 3H) ppm; 13C NMR (75 MHz, DMSO ꢀ d) δ: 153.1,
150.9, 148.3, 123.3, 118.6, 116.8, 113.4, 113.3, 56.0, 55.4, 21.3 ppm; IR (KBr) ν: 2941.0,
1503.8, 1264.1, 1225.9, 1024.6, 768.4 cm–1. MS (EI) m/z 269 [M+1] +.
2ꢀ(2,4ꢀdichlorophenyl)ꢀ1Hꢀbenzo[d]imidazole (3aa):15c According to general procedure, 1p (187
mg, 1 mmol) gave 3aa (185 mg, 67%) as a white solid. Rf = 0.3 (EtOAc/hexanes, 3:7); m.p. 218
ꢀ 220 ºC; 1H NMR (300 MHz, DMSO ꢀ d) δ: 7.90 (d, J = 8.49 Hz, 1H), 7.60 ꢀ 7.58 (m, 2H), 7.46
13
ꢀ 7.45 (m, 1H), 7.31 (dd, J = 8.36, 1.90 Hz, 1H), 7.19 ꢀ 7.16 (m, 1H) ppm; C NMR (75 MHz,
DMSO ꢀ d) δ: 148.2, 143.0, 135.1, 133.3, 132.7, 129.9, 128.8, 127.8, 123.0, 122.1, 119.2, 111.9
ppm; IR (KBr) ν: 2913.2, 1422.8, 1216.2, 1100.0, 995.0, 772.1 cm–1; MS (EI) m/z 263 [M+1] +.
2ꢀ(3, 4, 5ꢀtrimethoxyphenyl)ꢀ1Hꢀbenzo[d]imidazole (3ab):15d According to general procedure ,
1q (210 mg, 1 mmol) gave 3ab (198 mg, 70%) as a white solid. Rf = 0.2 (EtOAc/hexanes, 3:7);
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m.p. 259 ꢀ 261 ºC; H NMR (300 MHz, DMSO ꢀ d) δ: 12.84 (bs, 1H), 7.59 (bs, 2H), 7.52 (bs,
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2H), 7.21 ꢀ 7.18 (m, 2H) ppm; C NMR (75 MHz, CDCl3+DMSO ꢀ d) δ: 152.9, 151.4, 138.8,
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7
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125.2, 121.7, 144.6, 114.4, 114.2, 103.6, 60.2, 55.7 ppm; IR (KBr) ν: 2912.6, 1590.0, 1429.9,
1220.5, 1128.6, 772.2cm–1. MS (EI) m/z 285 [M+1] +.
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5, 6ꢀdichloroꢀ2ꢀpꢀtolylꢀ1Hꢀbenzo[d]imidazole (3ac):16a According to general procedure, 1b (134
mg, 1 mmol) gave 3ac (144 mg, 52%) as a yellow solid. Rf = 0.3 (EtOAc/hexanes, 3:7); m.p. 223
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ꢀ 225 ºC; H NMR (300 MHz, DMSO ꢀ d) δ: δ 13.16 (s, 1H), 8.05 (d, J = 8.1 Hz, 2H), 7.91 (s,
1H), 7.73 (s, 1H), 7.37 (d, J = 8.0 Hz, 2H), 2.38 (s, 3H) ppm; 13C NMR (75 MHz, DMSO ꢀ d) δ:
153.9, 143.5, 140.4, 134.5, 129.6, 126.7, 124.5, 124.0, 119.7, 112.5, 21.0 ppm; MS (EI) m/z 277
[M+1] +.
2ꢀpꢀtolylꢀ1Hꢀimidazoleꢀ4,5ꢀdicarbonitrile (3ad):16b According to general procedure, 1b (134 mg,
1 mmol) gave 3ad (104 mg, 50%) as a yellow solid. Rf = 0.3 (EtOAc/hexanes, 3:7); m.p. 143 –
145 ºC; 1H NMR (300 MHz, CDCl3 + DMSO ꢀ d) δ 7.83 (d, J = 8.2 Hz, 2H), 7.27 (d, J = 8.0 Hz,
13
2H), 2.35 (s, 3H) ppm; C NMR (75 MHz, CDCl3 + DMSO ꢀ d) δ: 150.9, 140.5, 129.3, 126.0,
124.6, 115.6, 110.8, 20.9 ppm; MS (EI) m/z 208 [M+1] +.
2ꢀ(naphthalenꢀ1ꢀyl)ꢀ1Hꢀbenzo[d]imidazole (3ae):15c According to general procedure, 1r (170
mg, 1 mmol) gave 3ae (165 mg, 68%) as a white solid. Rf = 0.3 (EtOAc/hexanes, 3:7); m.p. 217
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ꢀ 219 ºC; H NMR (300 MHz, DMSO ꢀ d) δ: 12.93 (bs, 1H), 9.11 (d, J = 7.72 Hz, 1H), 8.11 ꢀ
8.00 (m, 3H), 7.78 (d, J = 6.85 Hz, 1H), 7.71 ꢀ 7.56 (m, 4H), 7.28 ꢀ 7.23 (m, 2H) ppm; 13C NMR
(75 MHz, DMSO ꢀ d) δ: 151.3, 143.8, 134.4, 133.5, 130.4, 130.1, 127.8, 127.5, 127.0, 126.3,
125.2, 122.6, 121.5, 119.0, 111.3 ppm; IR (KBr) ν: 2917.2, 1389.2, 1221.3, 772.8 cm–1; MS (EI)
m/z 225 [M+1] +.
2ꢀ(naphthalenꢀ2ꢀyl)ꢀ1Hꢀbenzo[d]imidazole (3af):14a According to general procedure, 1s (170
mg, 1 mmol) gave 3af (168 mg, 69%) as a white solid. Rf = 0.3 (EtOAc/hexanes, 3:7); m.p. 201 ꢀ
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203 ºC; 1H NMR (300 MHz, DMSO ꢀ d) δ: 8.68 (bs, 1H), 8.29 (dd, J = 8.60, 1.59 Hz, 1H), 7.88
(d, J = 8.71 Hz, 1H), 7.84 ꢀ 7.79 (m, 2H), 7.64 ꢀ 7.61 (m, 2H), 7.49 ꢀ 7.43 (m, 2H), 7.21 ꢀ 7.18
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(m, 2H) ppm; C NMR (75 MHz, CDCl3+DMSO ꢀ d) δ: 151.5, 139.3, 139.2, 133.3, 132.6,
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127.9, 127.2, 126.4, 126.1, 125.9, 123.6, 121.9, 114.6 ppm; IR (KBr) ν: 2927.5, 1385.2, 1221.5,
772.8 cm–1; MS (EI) m/z 225 [M+1] +.
2ꢀ(thiophenꢀ2ꢀyl)ꢀ1Hꢀbenzo[d]imidazole (3ag):6a According to general procedure, 1t (126 mg, 1
mmol) gave 3ag (156 mg, 78%) as a brown solid. Rf = 0.3 (EtOAc/hexanes, 3:7); m.p. 342 ꢀ 344
ºC; 1H NMR (300 MHz, DMSO ꢀ d) δ: 12.94 (bs, 1H), 7.82 (dd, J = 3.56, 0.84 Hz, 1H), 7.72 (dd,
13
J = 4.98, 0.84 Hz, 1H), 7.58 ꢀ 7.51 (m, 2H), 7.24 ꢀ 7.18 (m, 3H) ppm; C NMR (75 MHz,
DMSO ꢀ d) δ: 147.0, 133.7, 128.7, 128.2, 126.6, 122.2, 122.1, 118.6, 118.5, 111.1, 111.0 ppm;
IR (KBr) ν: 2912.0, 1405.1, 1220.9, 741.6, 700.8 cm–1; MS (EI) m/z 201 [M+1] +.
5ꢀmethylꢀ2ꢀ(thiophenꢀ2ꢀyl)ꢀ1Hꢀbenzo[d]imidazole (3ah):16c According to general procedure, 1t
(126 mg, 1 mmol) gave 3ah (139 mg, 65%) as a white solid. Rf = 0.3 (EtOAc/hexanes, 3:7); m.p.
225 ꢀ 227 ºC; 1H NMR (300 MHz, DMSO ꢀ d) δ: 12.79 (bs, 1H), 7.79 (d, J = 2.96 Hz, 1H), 7.69
(d, J = 4.90 Hz, 1H), 7.42 (d, J = 8.22 Hz, 1H), 7.32 (s, 1H), 7.22 ꢀ 7.20 (m, 2H), 7.00 (d, J =
13
8.05 Hz, 1H), 2.41 (s, 3H) ppm; C NMR (75 MHz, DMSO ꢀ d) δ: 146.6, 133.8, 131.6, 131.3,
128.3, 128.1, 126.3, 123.5, 21.2 ppm; IR (KBr) ν: 2937.1, 1420.2, 1218.4, 941.5, 767.8, 710.3
cm–1; MS (EI) m/z 215 [M+1] +.
4ꢀ(1Hꢀbenzo[d]imidazolꢀ2ꢀyl)aniline (3ai):16d According to general procedure, 1u (135 mg, 1
mmol) gave 3ai (62 mg, 30%) as a pale yellow solid. Rf = 0.2 ( EtOAc/hexane, 8:2); m.p. 245 ꢀ
1
248 ºC; H NMR (300 MHz, CDCl3+DMSO) δ: 12.28 (bs, 1H), 7.93 (d, J = 70.0 Hz, 2H), 7.43
13
(s, 2H), 7.06 (s, 2H), 6.64 (s, 2H), 5.24 (s, 2H) C NMR (101 MHz, DMSO) δ 152.5, 150.6,
127.7, 121.2, 117.2, 113.5 ppm; MS (EI) m/z 210 [M+1] +.
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4ꢀ(1Hꢀbenzo[d]imidazolꢀ2ꢀyl)phenol(3aj):4b According to general procedure, 1v (136 mg, 1
mmol) gave 3aj (73.5 mg, 35%) as a pale yellow solid. Rf = 0.3 (EtOAc/hexane, 8:2); m.p. 243 ꢀ
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245 ºC; H NMR (300 MHz, CDCl3+DMSO) δ 12.63 (s, 1H), 9.94 (s, 1H), 8.00 (d, J = 8.4 Hz,
2H), 7.53 (d, J = 32.7 Hz, 2H), 7.07 (d, J = 47.9 Hz, 2H), 6.91 (d, J = 8.4 Hz, 2H). 13C NMR (75
MHz, CDCl3+DMSO) δ 159.0, 151.7, 127.9, 121.3, 121.0, 115.5 ppm; MS (EI) m/z 211 [M+1]
+
.
4ꢀ(1Hꢀbenzo[d]imidazolꢀ2ꢀyl)benzonitrile (3ak):3c According to general procedure, 1w (145 mg,
1 mmol) gave 3ak (110 mg, 50%) as a pale yellow solid. Rf = 0.4 (EtOAc/hexane, 4:6); m.p.
247 ꢀ 249 ºC; 1H NMR (300 MHz, DMSO) δ 13.20 (s, 1H), 8.34 (d, J = 8.5 Hz, 1H), 8.03 (d, J
= 8.5 Hz, 1H), 7.72 (d, J = 7.4 Hz, 1H), 7.58 (d, J = 7.2 Hz, 1H), 7.38 – 7.16 (m, 1H). 13C NMR
(75 MHz, CDCl3+DMSO) δ 149.2, 134.1, 132.4, 126.8, 122.5, 118.2, 111.9 ppm; MS (EI) m/z
220 [M+1] +.
methyl 4ꢀ(1Hꢀbenzo[d]imidazolꢀ2ꢀyl)benzoate (3al):17a According to general procedure, 1x (178
mg, 1 mmol) gave 3al (113 mg, 45%) as a pale yellow solid. Rf = 0.4 (EtOAc/hexane, 3:7); m.p.
1
201 ꢀ 203 ºC; H NMR (500 MHz, DMSO) δ 13.13 (s, 1H), 8.32 (d, J = 8.4 Hz, 2H), 8.11 (t, J =
12.7 Hz, 2H), 7.70 (d, J = 7.8 Hz, 1H), 7.56 (d, J = 7.8 Hz, 1H), 7.37 – 7.10 (m, 2H), 3.90 (s,
13
3H). C NMR (101 MHz, DMSO) δ 165.8, 149.9, 143.8, 135.1, 134.3, 130.3, 129.8, 126.6,
123.1, 122.0, 119.2, 111.6, 52.3 ppm; MS (EI) m/z 253 [M+1] +.
4ꢀ(1Hꢀbenzo[d]imidazolꢀ2ꢀyl)benzoic acid (3am):17bAccording to general procedure, 1y (164
mg, 1 mmol) gave 3am (60 mg, 25%) as a pale yellow solid. Rf = 0.2 (EtOAc/hexane, 8:2); m.p.
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297 ꢀ 299 ºC; H NMR (500 MHz, DMSO) δ 13.10 (s, 2H), 8.20 (d, J = 94.3 Hz, 4H), 7.63 (s,
2H), 7.24 (s, 2H). 13C NMR (101 MHz, DMSO) δ 166.8, 150.1, 133.9, 129.9, 126.4, 122.5 ppm;
MS (EI) m/z 239 [M+1] +.
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2ꢀ(3ꢀbromophenyl)ꢀ5ꢀmethylꢀ1Hꢀbenzo[d]imidazole (3an):16c According to general procedure,
4d (212 mg, 1 mmol) gave 3ai (177 mg, 62%) as a white solid. Rf = 0.4 (EtOAc/hexane, 3:7);
1
m.p. 201 ꢀ 203 ºC; H NMR (300 MHz, DMSO ꢀ d) δ: 13.1(bs, 1H), 8.98 (s, 1H), 8.58 (d, J =
7.88 Hz, 1H), 8.30 (dd, J = 8.22, 1.56 Hz, 1H), 7.83 (t, J = 8.04 Hz, 1H), 7.52 ꢀ 7.42 (m, 2H),
13
7.07 (d, J = 7.98 Hz, 1H), 2.44 (s, 3H) ppm; C NMR (75 MHz, DMSO ꢀ d) δ: 148.6, 148.3,
132.2, 132.1, 132.0, 131.8, 130.5, 124.1, 123.9, 120.6, 21.3 ppm; IR (KBr) ν: 2969.2, 1522.9,
1418.0, 1347.2 ,772.2 cm–1; MS (EI) m/z 287 [M+2] +.
2ꢀ(4ꢀbromophenyl)ꢀ5ꢀmethylꢀ1Hꢀbenzo[d]imidazole (3ao):16c According to general procedure, 4e
(212 mg, 1 mmol) gave 3j (172 mg, 60%) as a white solid. Rf = 0.4 (EtOAc/hexane, 3:7); m.p.
1
215 ꢀ 217 ºC; H NMR (300 MHz, DMSO ꢀ d) δ: 12.84 (d, J = 11.71 Hz, 1H), 8.08 (d, J = 8.53
Hz, 2H), 7.74 (d, J = 8.61 Hz, 2H), 7.54 ꢀ 7.31 (m, 2H), 7.03 (t, J = 8.77 Hz, 1H), 2.43 (s, 3H)
13
ppm; C NMR (75 MHz, DMSO ꢀ d) δ: 149.6, 141.8, 135.2, 131.8, 128.1, 122.9, 118.5, 111.0,
110.9, 21.3 ppm; IR (KBr) ν: 2969.2, 1522.9, 1418.0, 1347.2 ,772.2 cm–1; MS (EI) m/z 287
[M+2] +.
2ꢀ(4ꢀMethoxyꢀphenyl)ꢀpyrazine:12
Column chromatography (flash silica gel, Hexane/EtOAc): Rf = 0.40 (EtOAc/hexane, 3:7); yield
85 %; Colorless solid; 1H NMR (400 MHz, CDCl3) δ = 9.30 (bs, 1H), 8.19 (d, J = 8.95 Hz, 2H),
8.14 ꢀ 8.09 (m, 2H), 7.79 ꢀ 7.70 (m, 2H), 7.04 (d, J = 8.86 Hz, 2H), 3.91 (s, 3H) ppm; 13C NMR
(75 MHz, CDCl3) δ = 161.6, 151.6, 143.2, 142.5, 141.4, 130.3, 129.5, 129.4, 129.2, 129.1,
114.7, 55.6 ppm.
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ACKNOWLEDGEMENTS
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This work was supported by CSIRꢀORIGIN (CSC0108), New Delhi. We are thankful to NMR,
Mass divisions of CSIRꢀIICT, for providing the analytical facilities. O.R, A.U and A.S thank
CSIR and UGC for the Ph.D. fellowships.
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Supporting Information Available. 1H & 13C NMR spectra of all compounds. This material is
available free of charge via the Internet at http://pubs.acs.org
References and Notes:
1. (a) Yadav, G.; Ganguly, S. Eur. J. Med. Chem. 2015, 97, 419ꢀ443. (b) Bansal, Y.; Silakari,
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M. M. B. Chem. Eur. J. 2011, 17, 12544ꢀ12555. (d) Min, J.; Won, J.; Kang, Y. S.; Nagase,
S. J. Photochem. Photobiol. A: Chem. 2011, 219, 148–153. (e) O’Hagan, D. J. Fluorine
Chem. 2010, 131, 1071ꢀ1081. (f) Wang, T.; Zhao, Z.; Wei, B.; Zhang, L.; Ji, L. J. Mol.
Struct. 2010, 970, 128ꢀ133.
2. (a) Wen, X.; El Bakali, J.; DeprezꢀPoulain, R.; Deprez, B. Tetrahedron Lett. 2012, 53,
2440ꢀ2443. (b) Hein, D.; Alheim, R. J.; Leavitt, J. J. Am. Chem. Soc. 1957, 79, 427ꢀ429. (c)
Phillips, M. A. J. Chem. Soc. 1928, 2393ꢀ2399. (d) Rambabu, D.; Murthi, P. R. K.; Dulla,
B.; Basaveswara Rao, M.; Pal, M. Synth. Commun. 2013, 43, 3083ꢀ3092.
3. (a) Tandon, V. K.; Kumar, M. Tetrahedron Lett. 2004, 45, 4185ꢀ4187. (b) Bommegowda,
Y. K.; Lingaraju, G. S.; Thamas, S.; Kumar, K. S. V.; Kumara, C. S. P.; Rangappa, K. S.;
Sadashiva, M. P. Tetrahedron Lett. 2013, 54, 2693ꢀ2695. (c) Pinder, J. L.; Davis, R. E.;
Charrier, J.ꢀD. Tetrahedron Lett. 2014, 55, 4853ꢀ4855. (d) Dubois, N.; Glynn, D.; McInally,
T.; Rhodes, B.; Woodward, S.; Irvine, D. J.; Dodds, C. Tetrahedron. 2013, 69, 9890ꢀ9897.
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