Simple and mild protocol for synthesis of 1,2- Disubstitued benzimidazoles using SBA-15-supported poly(4-styrenesulfonyl-(Perfluorobutylsulfonyl)Imide) catalyst

Article abstract of DOI:10.1080/00397911.2010.526280

A simple method for the synthesis of several 1,2-disubstituted benzimidazoles catalyzed by strongly acidic SBA-15-supported poly(4-styrenesulfonyl-(perfluorobutylsulfonyl) imide) is described. The protocol furnished the products in moderate yield and good selectivity in the condensation of o-phenylenediamine with structurally diverse aldehydes under mild conditions. Taylor & Francis Group, LLC.

Full text of DOI:10.1080/00397911.2010.526280

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Simple and Mild Protocol for Synthesis
of 1,2-Disubstitued Benzimidazoles
Using SBA-15-Supported Poly(4-
styrenesulfonyl(perfluorobutylsulfonyl)imide
Catalyst
Zhong-Hua Ma a b , Sheng Lin a & Jin Nie b
a Department of Chemistry, College of Basic Sciences, Huazhong
Agricultural University, Wuhan, China
b School of Chemistry and Chemical Engineering, Huazhong
University of Science and Technology, Wuhan, China
Accepted author version posted online: 04 Aug 2011.Published
online: 17 Oct 2011.
To cite this article: Zhong-Hua Ma , Sheng Lin & Jin Nie (2012) Simple and Mild Protocol
for Synthesis of 1,2-Disubstitued Benzimidazoles Using SBA-15-Supported Poly(4-
styrenesulfonyl(perfluorobutylsulfonyl)imide) Catalyst, Synthetic Communications: An
International Journal for Rapid Communication of Synthetic Organic Chemistry, 42:4, 506-515, DOI:
10.1080/00397911.2010.526280
To link to this article: http://dx.doi.org/10.1080/00397911.2010.526280
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Synthetic Communications1, 42: 506–515, 2012
Copyright # Taylor & Francis Group, LLC
ISSN: 0039-7911 print=1532-2432 online
DOI: 10.1080/00397911.2010.526280
SIMPLE AND MILD PROTOCOL FOR SYNTHESIS OF
1,2-DISUBSTITUED BENZIMIDAZOLES USING
SBA-15-SUPPORTED POLY(4-STYRENESULFONYL-
(PERFLUOROBUTYLSULFONYL)IMIDE) CATALYST
Zhong-Hua Ma,1,2 Sheng Lin,1 and Jin Nie2
1Department of Chemistry, College of Basic Sciences, Huazhong Agricultural
University, Wuhan, China
2School of Chemistry and Chemical Engineering, Huazhong University of
Science and Technology, Wuhan, China
GRAPHICAL ABSTRACT
Abstract A simple method for the synthesis of several 1,2-disubstituted benzimidazoles
catalyzed by strongly acidic SBA-15-supported poly(4-styrenesulfonyl-(perfluorobutylsul-
fonyl)imide) is described. The protocol furnished the products in moderate yield and good
selectivity in the condensation of o-phenylenediamine with structurally diverse aldehydes
under mild conditions.
Keywords Acidic composite; benzimidazole; perfluorobutylsulfonylimide; SBA-15
INTRODUCTION
The benzimidazole core is certainly classified as a privileged substructure for
drug design in light of the affinity it displays toward a variety of enzymes and protein
receptors.[1] Among various benzimidazole analogs, 1,2-disubstituted structures
result in drug leads and commercial pharmaceutical products,[2] such as the agonist
against the c-aminobutyric acid A receptor (GABAA),[3] inhibitors of hepatitis C
virus NS5B polymerase,[4] and the antihypertensive telmisartan.[5] This widespread
interest prompts extensive studies for their synthesis, and several methods have been
reported. These include intramolecular cross-coupling of o-halo aromatic
nitrogen-containing compounds (acetanilide,[6] amidine,[7] and guanidine[8]), direct
Received August 27, 2009.
Address correspondence to Jin Nie, School of Chemistry and Chemical Engineering, Huazhong
University of Science and Technology, Wuhan 430074, China. E-mail: niejin@mail.hust.edu.cn
506

NITROGEN ACID–CATALYZED SYNTHESIS OF BENZIMIDAZOLE
507
Scheme 1. Condensation of o-phenylenediamine with aldehydes.
N-alkylation of an unsubstituted benzimidazole,[3] one-pot synthesis from 2-nitro-
anilines in the presence of trimethyl orthoformate and H2,[9] and acid-catalyzed con-
densation of o-phenylenediamine (o-PD) with aldehydes.[10] Of the methods, the
condensation strategy has been more concentrated on the readily available materials,
but the superficially simple reaction is a complex sequence of competing reactions.[11]
Over the past few years, several catalyst systems have been reported to improve
the selectivity of 1,2-disubstituted benzimidazoles, such as SiO2=ZnCl2,[10(b)] ionic
liquid,[10(c)] silica sulfuric acid,[10(d)] L-proline,[10(e)] TsOH=graphite,[10(g)]
Fe(ClO4)3,[10(h)] and Montmorillonite K10 under microwave irradiation.[10j]
Although some of these catalysts are promising, there is still a need to develop
new catalysts for the synthesis of the analogues.
With the considerable attention on the super nitrogen- and carbon-acid-con-
taining perfluoroalkylsulfonyl in the development of new Brønsted acid catalysts,[12]
we here report a novel acid composite, mesoporous molecular sieve SBA-
15-supported poly(4-styrenesulfonyl (perfluoro-butylsulfonyl)imide) (PSFSI),[13]
which is further used to catalyze the condensation of o-PD with aldehydes at mild
conditions to afford 1,2-disubstituted benzimidazoles (Scheme 1).
RESULTS AND DISCUSSION
Preliminary condition optimization was carried out with o-PD and benzal-
dehyde (molar ratio 1:2.1) as the substrates. Two isolated main products were
characterized, and the structures were confirmed as 1-benzyl-2-phenyl-1H-benzo[d]-
imidazole (1a) and 2-phenyl-1H-benzo[d]imidazole (2a), respectively. Small amounts
of other complex products were not collected. The results are listed in Table 1.
As can be seen from Table 1, both products were obtained whose ratios
depended on the nature of solvent (entries 2–8). The excellent selectivity (94%)
was obtained with comparable yield of 1a (65%) to the documented data catalyzed
by some sulfonic acids (entries 2 and 12–14). Prolonging the reaction time was
unhelpful, and decreasing the amount of the catalyst led to lower yields of 1a in
the same time (entries 10 and 11). So, the optimal reaction conditions for 1a should
be benzaldehyde (3.2 mmol), o-PD (1.5 mmol), PSFSI=SBA-15 (30 mol%, relative to
o-PD), stirred 80 min at 25–28 ꢀC in 7 mL of CH3NO2.
The optimal conditions were employed for other structurally diverse aldehydes
to further examine catalytic performances of PSFSI=SBA-15, with minor adaptions
for several aldehydes according to the actual case. In most studied cases, moderate
yields were achieved, and 1 was formed selectively rather than 2 (Table 2). Aldehydes

508
Z.-H. MA, S. LIN, AND J. NIE
Table 1. Effect of reaction conditions on the yield and selectivity of the reaction of o-PD with
benzaldehydea
Isolated yield (%)
Entry
Solvent
Time (min)
Catalyst (mol%)
Total
1a
2a
Selectivity (%)b
1
2
3
4
5
CH3NO2
CH3NO2
MeCO2Et
CH3CN
360
80
—
30
30
30
30
72
70
65
67
64
43
65
51
49
59
29
5
60
94
78
73
93
80
80
14
18
5
CH2Cl2
80
6
7
80
80
30
30
78
56
55
44
23
12
70
78
EtOH
8
80
30
69
45
24
65
9
10
CH3NO2
CH3NO2
CH3NO2
CH3NO2
EtOH
50
110
80
30
30
20
30
30
19
66
72
62
79
73
89
62
63
56
52
44
66
4
9
94
88
90
66
60
74
11
6
12c
13d
14e
80
60
27
29
23
Solvent-free
40
aReaction conditions: benzaldehyde (3.2 mmol), o-PD (1.5 mmol), PSFSI=SBA-15 (relative to o-PD),
stirred at 25–28 ꢀC in 7 mL of solvent.
b
yield ð1Þ
Selectivity ¼
ꢃ 100%:
total yield ð1 þ 2Þ
cCatalyzed by NKC-9 (–SO3H resin).
dData from Ref. 10(g). Catalyzed by silica sulfuric acid at room temperature.
eData from Ref. 10(g). Catalyzed by p-toluensufonic acid=graphite at 75 ꢀC.
bearing electron-withdrawing groups (entries 9 and 10) required longer reaction time
to obtain comparable yields compared with those bearing electron-donating groups
(entries 1–7), and the electron-donating effect should be responsible for the
excellent selectivity. We were pleased to find that unbranched and branched alipha-
tic aldehydes could react smoothly in extended period (entries 11 and 12). The
relatively poor yield of branched aliphatic aldehyde was perhaps due to the steric effect.
Correspondingly, unsplit peaks were observed for the protons at ArCH2Ph between
5.66 and 5.39 in the 1H NMR spectra of the products 1, except for 1h, 1k, and 1l. Poor
selectivity was unfortunately observed in the case of 3-nitrobenzaldehyde (entry 10).
A possible mechanism to explain the formation of the 1,2-disubstituted benzi-
midazoles 1a–l from o-PD and aldehydes is depicted in Scheme 2.[10(b) 14]
Products 1
,
and 2 are obviously the results of two competing reactions. The fast formation of
dialkylidene (R ¼ alkyl) or dibenzilidene-o-PD (R ¼ aryl) was followed by acid-
catalyzed ring closure and 1, 3-hydride transfer (path A). The electron-donating
effect of R groups promoted the nucleophilic cyclization, and the electron-
withdrawing effect of R groups behaved otherwise, which led to a lifting amount
of the competitive product 2 (path B). Higher acidic strength of PSFSI (H0ꢁꢂ11)
than that of –SO3H (H0ꢁꢂ3) provided superior activation for the nucleophilic
cyclization and resulted in greater selectivity (Table 1, entries 2 and 12–14).

NITROGEN ACID–CATALYZED SYNTHESIS OF BENZIMIDAZOLE
509
Table 2. Condensation of o-PD with aldehyde derivativesa
Isolated yield (%)
Entry
Aldehyde
Products 1
Total
1
Selectivity (%)a
1
70
65 (1a)
94
2
3
67
49
67 (1b)
>99
46 (1c)
93
4
5
52
60
52 (1d)
>99
53 (1e)
88
6
75
61 (1f)
81
7
62
53 (1g)
85
(Continued )

510
Z.-H. MA, S. LIN, AND J. NIE
Table 2. Continued
Isolated yield (%)
Entry
Aldehyde
Products 1
Total
1
Selectivity (%)a
8
50
35 (1h)
70
9b
66
53 (1i)
80
10b
71
36 (1j)
51
11
12
56
42
56 (1k)
>99
>99
42 (1l)
Note. Reaction conditions: PSFSI=SBA-15 (30 mol%, relative to o-PD), o-PD (1.5 mmol), aryl aldehyde
and cinnamaldehyde (4.7 mmol), or alkyl aldehyde (3.2 mmol), stirred for 80 min at 25–28 ꢀC in 7 mL of
CH3NO2.
a
yield ð1Þ
Selectivity ¼
ꢃ 100%:
total yield ð1 þ 2Þ
bReaction time: 150 min. Only 40% of 1i and 29% of 1j were obtained in 80 min.
CONCLUSION
In conclusion, a new type of strongly acidic composite catalyst was developed
by immobilizing the homopolymer, PSFSI, onto SBA-15 silica. The 1,2-disubstituted

NITROGEN ACID–CATALYZED SYNTHESIS OF BENZIMIDAZOLE
511
Scheme 2. Possible mechanism of the synthesis of 1,2-disubstituted benzimidazoles.
benzimidazoles were obtained in moderate yield and good selectivity in the con-
densation of o-phenylenediamine with structurally diverse aldehydes under mild
conditions.
EXPERIMENTAL
All solvents (analytical-reagent grade) for synthesis were commercially avail-
able in China and pretreated before used. Fourier transform infrared (FT-IR) spec-
tra were conducted by using an Avatar 330 Fourier spectrometer with the KBr pellet
technique. NMR was recorded in CDCl3 or dimethylsulfoxide (DMSO-d6) solution
on a Bruker AV400 spectrometer using tetramethylsilane (TMS) as the internal stan-
dard. High-resolution mass spectroscopy (HRMS) data were tested on a Bruker
Apex IV Fourier transform mass spectrometry (FTMS). The melting point was
tested on X-4 digital display binocular microscope.
Immobilization of PSFSI onto SBA-15
A wet impregnation technique was used for the immobilization of PSFSI.
SBA-15 support was introduced into a three-neck flask containing anhydrous meth-
anol. The methanol solution of PSFSI was then added. The slurry was continuously
stirred at room temperature for 6 h, and then solvent was removed by rotary evap-
oration under reduced pressure. In the end, the resultant solid was dried at 135 ꢀC
overnight. The eligible mass ratio of the initial mixture was 1:1.15 (PSFSI=
SBA-15, wt=wt) without obvious loss of the orderly structure of SBA-15. Corre-
spondingly, the acid content of 0.87 mmol=g was obtained and the catalyst was
designated as PSFSI=SBA-15.
General Procedure for the Synthesis of Benzimidazoles
To a mixture of aromatic aldehyde (3.2 mmol, or 4.7 mmol fatty aldehyde) and
o-PD (1.5 mmol) was added 30 mol% PSFSI=SBA-15. Then 7 mL of CH3NO2 were
added, and the whole mixture was stirred at room temperature. The reaction pro-
gress was monitored by thin-layer chromatography (TLC). After completion of
the reaction, filtration was performed and the catalyst was washed thoroughly with
acetoacetate. The combined washings and the filtrate were evaporated in a vacuum.

512
Z.-H. MA, S. LIN, AND J. NIE
The residue was purified by column chromatography over silica gel eluting with
petroleum ether=AcOEt mixture.
Data
2-Phenyl-1-(phenylmethyl)-1H-benzimidazole
(1a). Mp
143–145 ꢀC
(lit.[15] mp 139–141 ꢀC); IR (KBr, n, cmꢂ1): 3080, 3060, 3030, 2947 (CH2, tas),
=
2854 (CH2, ts), 1603, 1493 (benzene backbone), 1471 (CH2, d), 1450 (C N), 734,
1
704 (C-H, c); H NMR (400 MHz, CDCl3) d: 7.91 (d, 1H, J ¼ 8 Hz), 7.72 (d, 2H,
J ¼ 7.2 Hz), 7.48 (d, 3H, J ¼ 6.8 Hz), 7.36–7.33 (m, 4H), 7.27–7.25 (m, 2H), 7.13
(d, 2H, J ¼ 7.2 Hz), 5.49 (s, 2H, ArCH2); 13C NMR (100 MHz, CDCl3) d: 154.2,
143.1, 136.4, 136.1, 130.0, 130.0, 129.3, 129.1, 128.8, 127.8, 126.0, 123.1, 122.8,
120.0, 110.6, 48.4 (CH2).
2-Phenyl-1H-benzoimidazole (2a). IR (KBr, n, cmꢂ1): 3047, 2964, 2920,
1590, 1541 (benzene backbone), 1462, 1443, 1430, 1314, 1276, 970, 742, 702, 687;
1H NMR (400 MHz, d6-DMSO) d: 12.97 (s, 1H, NH), 8.19 (d, 2H, J ¼ 7.6 Hz),
7.66–7.48 (m, 5H), 7.22 (d, 2H, J ¼ 3.6 Hz); 13C NMR (100 MHz, d6-DMSO) d:
151.7, 144.2, 135.5, 130.6, 130.4, 129.5, 126.9, 122.7, 119.1, 111.9.[16]
1-(4-Methoxybenzyl)-2-(4-methoxyphenyl)-1H-benzoimidazole
(1b).
Mp 129–131 ꢀC (lit.[10d] mp 129–130 ꢀC); IR (KBr, n, cmꢂ1): 3049, 2986, 2964,
2935 (CH3, tas), 2835, 1609, 1510 (benzene backbone), 1481 (CH2, d), 1460
=
(C N), 1386 (CH3, d), 1244 (C-O-C, tas), 1173, 1029 (C-O-C, ts), 837, 813, 735;
1H NMR (400 MHz, d6-DMSO) d: 7.70–7.68 (m, 3H), 7.45–7.43 (m, 1H),
7.25–7.19 (m, 2H), 7.09 (d, 2H, J ¼ 8.8 Hz), 6.95 (d, 2H, J ¼ 8.4 Hz), 6.85 (d, 2H,
J ¼ 7.6 Hz), 5.49 (s, 2H, ArCH2), 3.83 (s, 3H, OCH3), 3.69 (s, 3H, OCH3).
1-(4-tert-Butylbenzyl)-2-(4-tert-butylphenyl)-1H-benzoimidazole (1c).
Mp 240–242 ꢀC; IR (KBr, n, cmꢂ1): 3054, 2962, 2903, 2867, 1684, 1611, 1513 (ben-
1
=
zene backbone), 1484 (CH2, d), 1462 (C N), 1393, 1362 (CH3, d), 743; H NMR
(400 MHz, CDCl3) d: 7.92–7.90 (m, 1H), 7.71–7.69 (m, 2H), 7.51–7.49 (m, 2H),
7.38–7.31 (m, 3H), 7.25–7.24 (m, 2H), 7.08 (d, 2H, J ¼ 8.4 Hz), 5.48 (s, 2H, ArCH2),
1.39 (s, 9H, CH3), 1.33 (s, 9H, CH3); 13C NMR (100 MHz, CDCl3) d: 154.3, 153.2,
150.7, 143.0, 136.0, 133.4, 129.9, 129.0, 127.0, 126.0, 125.8, 125.7, 125.3, 122.8, 122.6,
119.8, 110.6, 48.2 (CH2), 34.9, 34.6, 31.3, 31.2 (CMe3). HRMS (ESI): calculated for
C28H32N2 [M þ H]þ 397.26383, found 397.26375.
1-(4-Dimethylaminobenzyl)-2-(4-dimethylaminophenyl)-1H-benzoimida-
zole (1d). Mp 240–242 ꢀC; IR (KBr, n, cmꢂ1): 3080, 3032, 2883, 2800 (NCH3), 1611,
=
1526 (benzene backbone), 1488 (CH2, d), 1455 (C N), 1442, 1389, 1365 (CH3, d),
1
1202, 746; H NMR (400 MHz, CDCl3) d: 7.84 (d, 1H, J ¼ 7.6 Hz), 7.66 (d, 2H,
J ¼ 8.8 Hz), 7.30–7.19 (m, 3H), 7.05 (d, 2H, J ¼ 8.8 Hz), 6.75 (d, 2H, J ¼ 8.8 Hz),
6.71 (d, 2H, J ¼ 8.4 Hz), 5.40 (s, 2H, ArCH2), 3.03 (s, 6H), 2.95 (s, 6H).
1-(2-Furanylmethyl)-2-(2-furanyl)-1H-benzoimidazole (1e). Mp 100–
101 ꢀC (lit.[10d] mp 94 ꢀC); IR (KBr, n, cmꢂ1): 3151, 3129, 3054, 2938, 1671, 1605,
1
=
1511 (benzene backbone), 1475 (CH2, d), 1456 (C N), 1438, 1007, 737; H NMR
(400 MHz, CDCl3) d: 7.81 (d, 1H, J ¼ 9.2 Hz), 7.67 (s, 1H), 7.53–7.50 (m, 1H),

NITROGEN ACID–CATALYZED SYNTHESIS OF BENZIMIDAZOLE
513
7.32 (d, 3H, J ¼ 19.2 Hz), 7.25 (d, 1H, J ¼ 3.6 Hz), 6.63 (d, 1H, J ¼ 0.8 Hz), 6.30–6.25
(m, 2H), 5.66 (s, 2H, ArCH2).
1-(3-Methylbenzyl)-2-(3-methylphenyl)-1H-benzoimidazole
(1f). Mp
74–76 ꢀC; IR (KBr, n, cmꢂ1): 3018, 2919, 1606, 1591, 1501 (benzene backbone),
1
=
1463 (CH2, d), 1447 (C N), 1377, 1007, 747; H NMR (400 MHz, CDCl3) d: 7.93
(d, 1H, J ¼ 7.6 Hz), 7.62 (s, 1H), 7.47 (d, 1H, J ¼ 7.2 Hz), 7.36–7.32 (m, 3H),
7.27–7.22 (m, 3H), 6.96–6.92 (m, 2H), 5.44 (s, 2H, ArCH2), 2.40 (s, 3H), 2.33 (s, 3H).
1-(2-Chlorobenzyl)-2-(2-chlorophenyl)-1H-benzoimidazole
(1g). Mp
162–165 ꢀC (lit.[10d] 163 ꢀC); IR (KBr, n, cmꢂ1): 3059, 2927, 1611, 1471 (CH2, d),
1
=
1440 (C N), 1396, 1047, 745; H NMR (400 MHz, CDCl3) d: 7.94 (d, 1H, J ¼ 8 Hz),
7.75–7.71 (m, 1H), 7.54–7.42 (m, 3H), 7.37–7.30 (m, 3H), 7.23–7.20 (m, 2H), 7.10 (d,
1H, J ¼ 8.8 Hz), 6.66 (d, 1H, J ¼ 6.8 Hz), 5.39 (s, 2H, ArCH2).
1-(3-Phenyl-2-propenyl)-2-(2-phenylethenyl)-1H-benzoimidazole (1h).
IR (KBr, n, cmꢂ1): 3156, 3026, 2926, 2849, 1686, 1635 (benzene backbone), 1550,
1495, 1450, 1202, 965, 747, 699; 1H NMR (400 MHz, CDCl3) d: 8.09 (d, 2H,
J ¼ 16 Hz), 7.89 (d, 1H, J ¼ 7.6 Hz), 7.80 (d, 1H, J ¼ 15.6 Hz), 7.63 (d, 1H,
J ¼ 7.2 Hz), 7.43–7.41 (m, 3H), 7.39–7.30 (m, 4H), 7.14 (d, 2H, J ¼ 16 Hz), 6.51 (d,
2H, J ¼ 16 Hz), 5.09 (d, 2H, J ¼ 5.2 Hz, ArCH2).
1-(4-Nitrobenzyl)-2-(4-nitrophenyl)-1H-benzoimidazole (1i). Mp 242–
244 ꢀC; IR (KBr, n, cmꢂ1): 3101, 3056, 2914, 2849, 1602 (benzene backbone), 1519
1
=
(NO2, tas), 1458 (C N), 1347 (NO2, ts), 857, 747; H NMR (400 MHz, CDCl3) d:
8.35 (d, 2H, J ¼ 8.8 Hz), 8.26 (d, 2H, J ¼ 8.4 Hz), 7.96 (d, 1H, J ¼ 7.6 Hz), 7.86 (d,
2H, J ¼ 8.8 Hz), 7.45–7.41 (m, 1H), 7.39–7.35 (m, 1H), 7.31–7.28 (m, 2H), 7.23 (d,
1H, J ¼ 8.0 Hz), 5.61 (s, 2H).
1-(3-Nitrobenzyl)-2-(3-nitrophenyl)-1H-benzoimidazole (1j). Mp 182–
184 ꢀC; IR (KBr, n, cmꢂ1): 3087, 2926, 2849, 1614 (benzene backbone), 1526
1
=
(NO2, tas), 1455(C N), 1350 (NO2, ts), 818, 737; H NMR (400 MHz, CDCl3) d:
8.52 (s, 1H), 8.38 (d, 1H, J ¼ 8.4 Hz), 8.23 (d, 1H, J¼ 8.4 Hz), 8.08 (d, 2H, J ¼ 8 Hz),
7.96 (d, 1H, J ¼ 8 Hz), 7.72 (t, 1H, J ¼ 8.0 Hz), 7.58 (t, 1H, J ¼ 8.0 Hz), 7.45–7.36 (m,
3H), 7.29 (d, 2H, J ¼ 8.8 Hz), 5.61 (s, 2H).
2-(3-Nitrophenyl)-1H-benzo[d]imidazole (2j). Mp 204–205 ꢀC (lit.[15] mp
207–208 ꢀC); IR (KBr, n, cmꢂ1): 3459 (NH), 3182, 1686, 1621, 1590, 1521, 1349
1
(NO2, ts), 811, 741, 705; H NMR (400 MHz, DMSO-d6) d: 13.34 (s, 1H, NH),
9.02 (s, 1H), 8.61 (d, 1H, J ¼ 7.6 Hz), 8.32 (d, 1H, J ¼ 8 Hz), 7.87–7.83 (m, 1H),
7.66 (s, 2H), 7.26 (s, 2H).
1-Butyl-2-propyl-1H-benzoimidazole (1k). IR (Nujol mull, n, cmꢂ1): 3053,
2961, 2933, 2873, 1615 (benzene backbone), 1508, 1459, 1413, 1378, 766, 743; H
1
NMR (400 MHz, CDCl3) d: 7.74 (s, 1H), 7.29 (s, 1H), 7.23–7.22 (m, 2H), 4.09 (t,
2H, J ¼ 7.6 Hz), 2.87–2.83 (m, 2H), 1.94–1.91 (m, 2H), 1.81–1.72 (m, 2H),
1.43–1.37 (m, 2H), 1.07 (t, 3H, J ¼ 7.6 Hz), 0.97 (t, 3H, J ¼ 7.6 Hz).
1-Isobutyl-2-isopropyl-1H-benzoimidazole (1l). IR (KBr, n, cmꢂ1): 3080,
3057, 2966, 2929, 2873, 1612 (benzene backbone), 1504, 1458, 1419, 1375, 1087,
745, 728; 1H NMR (400 MHz, CDCl3) d: 7.77–7.76 (m, 1H), 7.30 (s, 1H),

514
Z.-H. MA, S. LIN, AND J. NIE
7.23–7.22 (m, 2H), 3.93 (d, 2H, J ¼ 7.6 Hz), 3.24–3.17 (m, 1H), 2.28–2.17 (m, 1H),
1.45 (d, 6H, J ¼ 6.8 Hz), 0.97 (d, 6H, J ¼ 6.4 Hz) ; 13C NMR (100 MHz, CDCl3) d:
160.2, 142.5, 135.1, 121.8, 121.6, 119.2, 109.7, 50.8 (CH2), 29.3, 26.3, 21.9, 20.2.
HRMS (ESI): calculated for C14H20N2 [M þ H]þ 217.16993; found 217.16947.
ACKNOWLEDGMENTS
We gratefully acknowledge the financial support for the project from the Fun-
damental Research Funds for the Central Universities (2011JC004, 2009JC007,
2010BQ023).
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