Samarium diiodide promoted formation of 1,2-diketones and 1-acylamido-2-substituted benzimidazoles from N-acylbenzotriazoles

Article abstract of DOI:10.1016/S0040-4020(03)00575-1

N-Acylbenzotriazoles, when treated with samarium diiodide in THF, undergo self-coupling reaction to afford 1,2-diketones in good to excellent yields; while when treated with samarium diiodide in CH₃CN, they undergo ring-opening reaction to afford 1-acylamido-2-alkyl (or aryl) benzimidazoles in reasonable to good yields. A plausible mechanism was suggested.

Full text of DOI:10.1016/S0040-4020(03)00575-1

Tetrahedron 59 (2003) 4201–4207
Samarium diiodide promoted formation of 1,2-diketones
and 1-acylamido-2-substituted benzimidazoles
from N-acylbenzotriazoles
a
Xiaoxia Wang and Yongmin Zhang
a,b,*
a
Department of Chemistry, Zhejiang University, Xixi Campus, Hangzhou 310028, People’s Republic of China
State Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences,
Shanghai 200032, People’s Republic of China
b
Received 6 November 2002; revised 10 March 2003; accepted 3 April 2003
Abstract—N-Acylbenzotriazoles, when treated with samarium diiodide in THF, undergo self-coupling reaction to afford 1,2-diketones in
good to excellent yields; while when treated with samarium diiodide in CH CN, they undergo ring-opening reaction to afford 1-acylamido-2-
alkyl (or aryl) benzimidazoles in reasonable to good yields. A plausible mechanism was suggested. q 2003 Elsevier Science Ltd. All rights
3
reserved.
5
1
. Introduction
a variety of secondary and tertiary homoallylamines. All
the above reactions involve the removal of benzotriazole
group and no report concerning the benzotriazole ring-
opening reaction by samarium reagents has been available
so far. Herein we wish to describe the reaction type (ii)
and type (iii) of the benzotriazole derivatives N-acylbenzo-
triazoles promoted by SmI2.
1
Benzotriazole is a very useful synthetic auxiliary and its
application in organic chemistry has been extensively
investigated. After the introduction of benzotriazole group
into a molecule, the resulting benzotriazole derivatives
can usually undergo three types of transformation: (i)
transformation in which the benzotriazole group is
retained; (ii) transformation involving the removal of the
benzotriazole group; and (iii) transformation involving
the cleavage of the benzotriazole ring. Whilst engaging in
the research of the application of samarium reagents, we are
especially interested in the reactions between benzotriazole
1
e
We have noted that promoted by SmI in THF, benzoyl
2
chlorides underwent reductive coupling reaction to give
6
a-diketones while they, when treated with SmI in CH CN,
2
3
0
high yields. Keeping in view that benzotriazole group in
could afford a,a -stilbenediol dibenzoate compounds in
7
derivatives and samarium reagents. SmI as an one-electron
2
many ways is comparable to a halogen substituent because
1
reducing agent can remove the benzotriazolyl moiety from
a-benzotriazolyl ketones to afford the corresponding
of its leaving abilities, we began to focus on the present
study on the reactivity of the benzoyl chlorides analogues
2
ketones. Also, the elimination of benzotriazolyl radical
z
N-acylbenzotriazoles promoted by SmI . The reactions
2
conducted in THF and in CH CN are investigated,
3
respectively.
(Bt ) from N-[(N,N-dialkylamino)alkyl]benzotriazoles is
realized by the reduction of SmI with the generation of
2
a-amino radicals, which undergo dimerization to form
z
3
vicinal diamines. Besides, SmI can eliminate the Bt from
2
the appropriately designed benzotriazole adducts with an
activated double bond to produce an a-amino radical, which
undergo intramolecular addition to the double bond to
afford N-cycloalkylamines. Organosamarium reagent allyl-
samarium bromide could substitute the benzotriazolyl
group, thus providing a new method for the preparation of
2. Results and discussion
2.1. With THF as the solvent
4
As shown in Scheme 1 and Table 1, N-acylbenzotriazoles
(1) when treated with samarium diiodide in THF at room
temperature could afford a-diketones (2) in reasonable to
excellent yields.
Keywords: samarium (II) diiodide; N-acylbenzotriazoles; 1,2-diketones;
1
*
-acylamido-2-alkyl (or aryl) benzimidazoles.
Corresponding author. Tel.: 86-571-85178611; fax: 86-571-88807077;
e-mail: yminzhang@mail.hz.zj.cn
8
Acid chlorides and keto cyanides were both reported to be
coupled by samarium diiodide into 1,2-diketones. In both
0040–4020/03/$ - see front matter q 2003 Elsevier Science Ltd. All rights reserved.
doi:10.1016/S0040-4020(03)00575-1

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X. Wang, Y. Zhang / Tetrahedron 59 (2003) 4201–4207
Scheme 1.
2
Table 1. SmI promoted coupling of N-acylbenzotriazoles giving 1,2-diketones
a
Entry
R
Substrate
SmI
2
equivalents
Product
Reaction time (min)
10
Yield (%)
1
2
3
4
5
6
7
8
9
C
C
6
H
H
5
5
1a
1a
1b
1b
1b
1b
1c
1d
1e
1f
1g
1h
1i
1j
1k
1l
2.2
3.3
2.2
3.3
2a
2a
2b
2b
2b
2b
2c
2d
2e
2f
2g
2h
2i
2j
2k
2l
68 (26)
60 (29)
95 (0)
b
6
180
m-ClC
m-ClC
m-ClC
m-ClC
6
H
6
H
6
H
6
H
4
4
4
4
5
180
b
c
92 (0)
c
96 (0)
d
2.2
5
180
5
5
5
5
5
5
5
5
5
5
10
10
e
2.2
83 (12)
93 (0)
95 (0)
p-ClC
p-BrC
6
H
4
2.2
2.2
2.2
2.2
2.2
2.2
2.2
2.2
2.2
2.2
2.2
2.2
6
H
4
p-IC
p-CH
o-CH
6
H
4
92 (0)
10
11
12
13
14
15
16
17
18
3
C
6
H
4
68 (trace)
52 (trace)
65 (trace)
53 (trace)
0 (0)
0 (0)
0 (0)
11 (35)
16 (30)
3
OC
6
H
4
p-Et
2-furyl
p-NO
2
NC
6
H
4
2
C
6
H
4
3-Pyridyl
4-Pyridyl
n-C
n-C
4
H
H
9
1m
1n
2m
2n
6
12
The reaction was conducted at room temperature unless specified otherwise.
a
The yield of a-hydroxy ketones obtained is shown in parentheses.
b
2
The characteristic blue color of SmI still persisted.
c
d
e
No obvious decrease in the yield of 1,2-diketone.
The run was carried out with 2.2 equivalents of SmI
This run was carried out with 2.2 equiv. of SmI
2
and l.1 equivalents of samarium powder at room temperature.
2
and 1.1 equiv. of samarium powder under reflux conditions.
z
cases, acyl anion species and RCO radicals were deduced or
9
and 1 l (entry 16) failed to give any desirable products
besides benzotriazole. It is probable that the corresponding
even verified to be the intermediates and a leaving group
2
2
13
(
Cl or CN ) was involved. In our investigation here, acyl
radicals produced undergo decarbonylation before their
dimerization or electron transfer from SmI to form an acyl
z
anion species and RCO radicals may also be involved with
benzotriazoles acting as a leaving group. Despite the
similarity in the reaction mechanism, the present study is
a very useful method for the synthesis of a-diketones.
Unlike acyl chlorides and keto cyanides (the preparation of
them is tedious, needs high temperature and requires the
use of toxic cyanides), N-acylbenzotriazoles are stable
crystals and readily available from carboxylic acids and
2
anion species. Aliphatic N-acylbenzotriazoles mainly afford
with low yields a-ketol compounds instead of the
corresponding 1,2-diketones (entries 17 and 18). Finally,
when R is a p-methoxyphenyl group (substrate lo), vic-
di(1H-1,2,3-benzotriazol-1-yl)alkene (3) was obtained in
1
0
68% yield under the same SmI –THF conditions (Scheme
2
2).
1
1
N-(1-methanesulfonyl)benzotriazole. What’s more, benzo-
triazole as an auxiliary group can be recovered almost
quantitatively after the reaction and therefore the method
has the potential of recycling the starting material. These
characteristics coupled with the short reaction time and mild
reaction conditions may make the method an attractive one
for the preparation of 1,2-diketones.
N-Acylbenzotriazoles may be seen as a special type of
amide and vic-di(1H-1,2,3-benzotriazol-1-yl)alkene 3 may
be looked on as a product formed from the deoxygenative
coupling reaction of amides. Bearing in mind that the
deoxygenative coupling reaction of amides could be
1
4
effectively realized under SmI /Sm system, we treated
2
substrate 1b with SmI /Sm system (entry 5 and 6).
2
As for aromatic N-acylbenzotriazoles, the reaction is
strongly influenced by the substituents on the aromatic
ring. With an electron-withdrawing group present, the
reaction is very clean and affords 1,2-diketones exclusively
in high yields. While N-acylbenzotriazoles with an electron-
donating group attached on the aromatic ring gave relatively
lower yields. Though an iodo group on the aromatic ring is
1
2
potentially reactive towards SmI2, we were surprised to
find that the reaction can tolerate the iodo group (entry 9)
and afford the 1,2-bis(4-iodophenyl)ethanedione in excel-
lent yield. However, substrates 1j (entry 14), 1k (entry 15)
Scheme 2.

X. Wang, Y. Zhang / Tetrahedron 59 (2003) 4201–4207
4203
Scheme 3.
0
with samarium diiodide in acetonitrile give a,a -stilbene-
diol dibenzoate compounds in high yields, which is in
contrast to the report that benzoyl chlorides when treated by
samarium diiodide in tetrahydrofuran afford a-diketones or
Table 2. Preparation of 1-acylamido-2-substituted benzimidazoles
a
a
b
Substrate
R
Product
Reaction time
Yield (%)
1
1
1
1
1
1
1
1
1
1
1
1
1
a
b
c
C
6
H
5
4a
4c
4d
4b
4p
4m
4n
4o
4q
4r
4s
5 h
5 h
5 h
5 h
60 (10)
50 (15)
43 (26)
62 (–)
59 (–)
63
75
0 (72)
60
63
a-hydroxy ketones. This may indicate that SmI in THF and
2
in CH CN show very different reactivity. Therefore, we
3
treated N-acylbezotriazoles with SmI in CH CN. Interest-
3
ingly, a drastically different kind of products is obtained,
which is characterized as 1-acylamido-2-alkyl (or aryl)
m-ClC
p-ClC
p-CH
o-ClC
CH
CH
p-CH
CH
CH
c-C
CH
CH
6
H
4
6
H
4
c
f
3
C
6
H
4
2
c
p
m
n
o
q
r
s
t
u
6
H
4
5 h
3
(CH
(CH
2
)
)
2
CH
CH
2
30 min
30 min
30 min
30 min
30 min
30 min
30 min
30 min
3
2
4
2
1
benzimidazoles (4) by IR, H NMR, MS and elemental
analysis (Scheme 3 and Table 2).
3
OC
6
H
4
3
(CH
(CH
H
CH
2
)
)
6
CH
2
3
2
7
CH
2
6
11
82
79
73
The formation of 1-acylamido-2-alkyl (or aryl) benzo-
triazoles indicates that the benzotriazole ring is opened by
the reduction of SmI in acetonitrile.
3
2
4t
4u
3
2
a
1
The products were identified by mp, H NMR, MS, IR spectra, and
elemental analysis.
Benzotriazole ring is usually highly stable to acids and
1
b
c
The yield of 1,2-diketones obtained is shown in parentheses.
No attempts were made to isolate the by-products since the amount of
by-products was minute according to the TLC.
bases, to oxidation and reduction and to heat. However,
more and more reports are available concerning the
1
5
benzotriazole ring opening. For example, 1-aryl-benzo-
trizoles can be converted into carbazoles with loss of
nitrogen at 3608C. 1-Butyl-, 1-allyl-, 1-benzyl-, and
1-phenethylbenzonitriles ring open and lose nitrogen at
4008C. Substituted benzotriazoles exclude nitrogen to
form diradicals which then cyclize to form carbazoles
on photolysis. The opening of the benzotriazole ring in
benzotriazol-1-yl alkyl carbanions a to the benzotriazol-1-
yl group tend to loss of nitrogen, thus affording o-lithiated
1
6
However, the expected deoxygenative coupling product was
not obtained and 1,2-diketone remains to be the main
product with the a-ketol type compound as by-product.
1
7
1
8
2
.2. With CH CN as the solvent
3
As mentioned previously, benzoyl chlorides when treated
Scheme 4.

4204
X. Wang, Y. Zhang / Tetrahedron 59 (2003) 4201–4207
1
9
aniline imines. 1-(a-Alkoxyalkyl)benzotriazoles, when
treated with Grignard reagents, can also undergo the
short way for the syntheses of 1-acylamido-2-alkyl (or aryl)
benzimidazoles and may be superior to the previously
26
reported method starting from o-nitrophenylhydrazine.
2
0
benzotriazole ring opening. On standing, lithiated
N-(a-alkoxyalkyl)-benzotriazoles extrude nitrogen, which
presents a synthetically useful method for the preparation
of o-substituted anilines and benzannelated heterocycles.
-(Benzotriazol-1-yl)enamines undergo rearrangement,
and loss of nitrogen in refluxing toluene to give 2,4-di-
arylquinazolines. Treatment of a-benzotriazol-1-yl hydra-
zones with n-butyllithium in the presence of TMEDA gave
benzotriazines or indoles by the corresponding ring
2
1
3. Conclusions
2
With THF and CH CN as the reaction media, the
3
1
5
benzotriazole derivatives N-acylbezotriazoles can undergo,
respectively, transformation where the benzotriazolyl group
leaves and transformation where the benzotriazole ring
2
2
scission.
cleaves promoted by SmI , thus providing synthetically
2
useful methods for both 1,2-diketones and 1-acylamido-2-
substituted benzimidazoles. Further studies concerning
the reactivity of samarium reagents towards heteroatom
compounds are still in progress in our laboratory.
The formation of 1-acylamido-2-alkyl (or aryl) benzotri-
azoles in this investigation is an addition to the examples of
benzotriazole ring opening. Besides, it is one of the few
cases where there is no nitrogen releasing during the ring
opening and the three N atoms are retained altogether in the
products.
4. Experimental
4.1. General
Though the detailed mechanism is not clarified yet, a
plausible reaction pathway is proposed as in Scheme 4.
Tetrahydrofuran was distilled from sodium-benzophenone
and acetonitrile was distilled in the presence of phosphorus
pentoxide immediately prior to use. All reactions were
conducted under a nitrogen atmosphere. Melting points are
In Scheme 4, the intermediate C may be produced by Route
a where the N–N bond (a) in A is broken to form an
intermediate B, which was acylated by another molecule
of compound 1. C can also be formed through Route b
where the N–C bond (b) in A cleaves to give an acyl radical
I, which attacks the N–N bond in another molecule of
2
3
1
uncorrected. H NMR spectra were recorded on a Bruker
6
AC-400 instrument as CDCl or d -DMSO solutions using
3
TMS as internal standard. Chemical shifts (d) are reported in
ppm and coupling constants J are given in Hz. IR spectra
were recorded using KBr disks with a Bruker Vector-22
infrared spectrometer. Elemental analyses were performed
on a EA-1110 instrument. Metallic samarium and other
reagents were purchased from commercial sources, without
further purification before use. Substrates 1a–1m were
synthesized according to reported procedure with com-
compound 1. C gets another electron from SmI to form the
2
intermediate D. The NvN bond in compound D is further
2
4
reduced by an equivalent of SmI to give E. The amino
2
anion attached to the aromatic ring attacks the carbonyl
carbon intramolecularly in such a way that it can
preferentially form a five-membered ring (see F). After
another electron transfer from SmI to the N atom (see F to
2
1
1
G), an elimination of I SmOSmI from intermediate G
2
pounds 1d,e,m being new compounds.
2
constructs the benzimidazole skeleton (see H). Subsequent
protonation gives the final product 2.
4.2. General procedure for the preparation of substrates
1
1
1
Notably, when R is an alkyl group in compound 1, the
reaction for the formation of 2 is clean and the yield is high.
However, when R is an aryl group, the yield of 2 is relatively
low and a-diketones can be obtained as a by-product. For
such substrate 1o, the corresponding a-diketone even
becomes the main product and product 4 is not obtained.
Typical procedure for the synthesis of compounds 2 and 3:
under nitrogen atmosphere, 1H-1,2,3-benzotriazole-1-yl(4-
chlorophenyl)methanone (1c, 0.258 g, 1 mmol) dissolved in
dry THF (3 mL) was added at room temperature to
2.2 mmol of SmI dissolved in THF (20 mL). The resulting
2
solution turned yellow in 5 min. Dilute hydrochloric acid
(2 M, 5 mL) was added and the resulting mixture extracted
with diethyl ether (3£20 mL). The combined organic layer
was washed with brine, dried over anhydrous sodium
sulfate, and concentrated under reduced pressure. The
residue was separated on preparative TLC on silica gel
with ethyl acetate and cyclohexane (1:3) as eluent to afford
the 1,2-bis(4-chlorophenyl) ethanedione 0.259 g in 93%
yield.
In summary, here describes the first example of benzotrizole
ring opening promoted by SmI . The unique reductivity of
2
SmI in CH CN makes the benzotriazole ring susceptible to
2
3
ring opening. By cyclization again, it affords a synthetically
useful way for the preparation of 1-acylamido 2-alkyl (or
aryl) benzimidazoles.
The benzimidazole ring system is part of the vitamin B-12
structure and several benzimidazole derivatives are of
commercial importance as pharmaceuticals, veterinary
General procedure for the synthesis of compounds 4:
Samarium powder (0.33 g, 2.2 mmol) was placed in a
well-dried three-necked round bottom flask containing a
magnetic stirrer bar. The flask was evacuated and flushed
with nitrogen several times. Acetonitrile (15 mL) was added
through a rubber septum by a syringe. Iodine (0.54 g,
2.13 mmol) was added to the flask and the mixture was
2
5
anthelmintics and fungicides. Development of new
benzimidazole derivatives and research into their potential
uses are always of interest. As far as we know, 1-acylamido-
2-alkyl (or aryl) benzimidazoles remain less investigated.
The ring opening of benzotriazole ring in N-acylbenzotri-
azoles promoted by SmI in CH CN provides a novel and
2
3

X. Wang, Y. Zhang / Tetrahedron 59 (2003) 4201–4207
4205
stirred at room temperature until the solution became deep
brown (2 h). To the solution of SmI thus prepared was
added N-acylbenzotriazole 1 (1 mmol) in acetonitrile
4.2.7. 1H-1,2,3-Benzotriazole-1-yl(n-nonyl)methanone
(1r). White crystals, yield: 82%, mp: 38–408C. d : 8.29
2
H
(1H, d, J¼7.6 Hz), 8.12 (1H, d, J¼8.0 Hz), 7.63–7.67 (1H,
m), 7.48–7.52 (1H, m), 3.42 (2H, t, J¼7.2 Hz), 1.87–1.94
(2H,m), 1.27–1.51 (12H, m), 0.87 (3H, t, J¼6.8 Hz).
(
(
3 mL) by syringe. After being stirred for a given time
Table 1), most of the solvent was removed under reduced
2
1
pressure. Hydrochloric acid (0.2N, 3 mL) was added and the
mixture was extracted with diethyl ether (3£30 mL). The
combined organic extract was washed with brine, dried over
anhydrous sodium sulfate and concentrated. The residue
was separated by preparative TLC on silica gel with ethyl
acetate and cyclohexane (1:3) as eluent to afford product 4.
n
(KBr)/cm : 2946, 2919, 2851, 1740, 1595, 1485. m/z
max
þ
8.48; N, 15.37. Found C, 70.27; H, 8.55; N, 15.33%.
(%): 273 (M , 1.89). Anal. C H N O. Calcd C, 70.30; H,
16 23 3
4.2.8. 1H-1,2,3-Benzotriazole-1-yl(c-hexyl)methanone
(1s). White crystals, yield: 65%, mp: 94–968C. d : 8.30
H
(
1H, d, J¼8.4 Hz), 8.12 (1H, d, J¼8.4 Hz), 7.63–7.67 (1H,
4.2.1. 1H-1,2,3-Benzotriazole-1-yl(4-bromophenyl)-
methanone (1d). White plates, yield: 66%, mp: 142–
m), 7.48–7.52 (1H, m), 3.88–3.95 (1H, m), 2.12–2.15 (2H,
m), 1.88–1.92 (2H, m), 1.69–1.78 (3H, m), 1.48–1.51 (2H,
m), 1.30–1.35 (1H, m). nmax(KBr)/cm2 : 3106, 2950, 2934,
2853, 1730, 1594, 1482. m/z (%): 229 (M , 5.52), 146
(100). Anal. C H N O. Calcd C, 68.10; H, 6.59; N, 18.33.
Found C, 68.12; H, 6.63; N, 18.30%.
1
1
438C. d : 8.39 (1H, d, J¼8.0 Hz), 8.16 (3H, dd, J¼8.4,
H
þ
8
cm : 1707, 1588, 1482, 1377, 943, 751. m/z (%): 303 (M ,
8
1
N, 13.91. Found C, 51.61; H, 2.77; N, 13.86%.
.0 Hz), 7.71–7.75 (3H, m), 7.55–7.59 (1H, m). n (KBr)/
max
2
1
þ
1
3 15 3
þ
.57), 301 (M , 9.24), 273 (76.52), 275 (74.11), 183 (100),
85 (92.48). Anal. C H BrN O. Calcd C, 51.68; H, 2.67;
1
3
8
3
4.2.9. 1,2-Diphenyl-1,2-ethanedione (2a). Yellow crystals,
7
2
yield: 68%, mp: 95–978C (lit., 95–978C). d : 7.99–7.97
H
4.2.2. 1H-1,2,3-Benzotriazole-1-yl(4-iodophenyl)metha-
none (1e). Golden plates, yield: 58%, mp: 153–1558C.
(4H, m), 7.69–7.64 (2H, m), 7.53–7.50 (4H, m). nmax(KBr)/
2
1
cm : 3064, 1660, 1594, 1450, 1211, 719, 643.
d : 8.38 (1H, d, J¼8.4 Hz), 8.17 (1H, d, J¼8.0 Hz), 7.96
H
(
4H, s), 7.73 (1H, t, J¼7.6 Hz), 7.57 (1H, t, J¼7.6 Hz).
4.2.10. 1,2-Di(3-chlorophenyl)-1,2-ethanedione (2b).
29
Yellow crystals, yield: 96%, mp:116–1178C (lit.,
n
(
(KBr)/cm2 : 1710, 1596, 1391, 937, 747. m/z (%): 349
1
max
þ
M , 17.31), 321 (100), 231 (81.44). Anal. C H IN O.
1
1158C). d : 7.97 (2H, s), 7.83–7.85 (2H, m), 7.64–7.66
H
3
8
3
(2H, m), 7.46–7.49 (2H, m). nmax(KBr)/cm2 : 3076, 3059,
1
Calcd C, 44.72; H, 2.31; N, 12.04. Found C, 44.76; H, 2.37;
N, 11.99%.
1673, 1588, 1570, 1198.
4.2.3. 1H-1,2,3-Benzotriazole-1-yl(4-methoxyphenyl)-
methanone (1o). White needles, yield: 73%, mp: 113–
4.2.11. 1,2-Di(4-chlorophenyl)-1,2-ethanedione (2c).
2
7
Yellow crystals, yield: 93%, mp:195–1988C (lit., 195–
1968C). d : 7.91 (4H, d, J¼8.4 Hz), 7.50 (4H, d, J¼8.4 Hz).
1
8
148C. d : 8.38 (1H, d, J¼8.4 Hz), 8.30 (2H, d, J¼8.8 Hz),
H
H
.17 (1H, d, J¼8.4 Hz), 7.70 (1H, t, J¼7.6 Hz), 7.54 (1H, t,
n
(KBr)/cm2 : 3010, 1659, 1586, 1571, 1404, 1209.
1
max
J¼7.6 Hz), 7.07 (2H, d, J¼8.8 Hz), 3.94 (3H, s). n (KBr)/
max
2
1
þ
100). Anal. C H N O . Calcd C, 66.40; H, 4.38; N,
cm : 1710, 1607, 1578. m/z (%): 253 (M , 6.87), 135
(
4.2.12. 1,2-Di(4-bromophenyl)-1,2-ethanedione (2d).
Yellow crystals, yield: 95%, mp: 227–2298C (lit., 228–
29
1
4 11 3 2
1
6.59. Found C, 66.45; H, 4.42; N, 16.55%.
2298C). d : 7.83 (4H, d, J¼8.4 Hz), 7.67 (4H, d, J¼8.4 Hz).
H
1
n
(KBr)/cm2 : 3150, 1664, 1586.
max
4.2.4. 1H-1,2,3-Benzotriazole-1-yl(2-chlorophenyl)metha-
none (1p). White crystals, yield: 70%, mp: 84–868C. dH:
4.2.13. 1,2-Di(4-iodophenyl)-1,2-ethanedione (2e). Golden
2
8b
8
.42 (1H, d, J¼8.0 Hz), 8.17 (1H, d, J¼8.4 Hz), 7.44–7.77
crystals, yield: 92%, mp: 243–2458C(lit.,
2558C).
2
1
(
(
6H, m). n (KBr)/cm : 1724, 1589, 1484. m/z (%): 257
max
M , 12.57), 139 (100). Anal. C H ClN O. Calcd C, 60.60;
1
d : 8.03 (4H, d, J¼8.4 Hz), 7.67 (4H, d, J¼8.4 Hz).
H
þ
21
n
(KBr)/cm : 3066, 1664, 1579.
max
3
8
3
H, 3.13; N, 16.31. Found C, 60.61; H, 3.20; N, 16.28%.
4.2.14. 1,2-Di(4-methylphenyl)-1,2-ethanedione (2f).
White crystals, yield: 68%, mp: 103–1058C (lit., 104–
2
7
4
(
.2.5. 1H-1,2,3-Benzotriazole-1-yl(n-hexyl)methanone
1n). White crystals, yield: 70%, mp: 50–528C. d : 8.29
1058C). d : 7.86 (4H, d, J¼8.0 Hz), 7.30 (4H, d, J¼8.0 Hz),
H
H
1
(
1H, d, J¼8.4 Hz), 8.12 (1H, d, J¼8.4 Hz), 7.63–7.67 (1H,
2.43 (6H, s). n (KBr)/cm2 : 2919, 1661, 1605, 1172.
max
m), 7.48–7.52 (1H, m), 3.42 (2H, t, J¼7.2 Hz), 1.87–1.94
(
n
2H, m), 1.32–1.50 (6H, m), 0.90 (3H, t, J¼6.8 Hz).
þ
.41; N, 18.17. Found C, 67.61; H, 7.47; N, 18.14%.
4.2.15. 1,2-Di(2-methoxyphenyl)-1,2-ethanedione (2g).
28a
Orange crystals, yield: 52%, mp: 123–1258C (lit.,
2
1
(KBr)/cm : 2946, 2919, 2867, 1746, 1589, 1484. m/z
max
(
%): 231 (M , 3.29). Anal. C H N O. Calcd C, 67.57; H,
3
1278C). d : 8.08 (2H, d, J¼8.0 Hz), 7.59–7.55 (2H, m),
1
3
17
H
7
7.14–7.10 (2H, m), 6.95 (2H, d, J¼8.0 Hz), 3.60 (6H, s).
1
n
(M , 3.74), 135 (M /2, 100).
(KBr)/cm2 : 2945, 1657, 1595, 1321. m/z (%): 270
max
þ
þ
4
(
.2.6. 1H-1,2,3-Benzotriazole-1-yl(n-octyl)methanone
1q). White crystals, yield: 82%, mp: 48–498C. d : 8.29
H
(
1H, d, J¼7.6 Hz), 8.12 (1H, d, J¼8.4 Hz), 7.63–7.67 (1H,
4.2.16. 1,2-Di(4-diethylaminophenyl)-1,2-ethanedione
(2h). Light yellow crystals, yield: 65%, mp: 85–878C;
m), 7.48–7.52 (1H, m), 3.42 (2H, t, J¼7.2 Hz), 1.87–1.94
(
n
2H, m), 1.29–1.51 (10H, m), 0.89 (3H, t, J¼6.8 Hz).
d : 7.85 (4H, d, J¼8.4 Hz), 6.70 (4H, d, J¼7.2 Hz), 3.43
H
2
1
21
(KBr)/cm : 2946, 2919, 2858, 1742, 1589, 1484. m/z
(8H, q, J¼7.0 Hz), 1.20 (12H, t, J¼7.0 Hz). n (KBr)/cm
:
max
max
þ
.16; N, 16.20. Found C, 69.45; H, 8.23; N, 16.17%.
(
%): 259 (M , 2.10). Anal. C H N O. Calcd C, 69.47; H,
1
2972, 2933, 2902, 2871, 1645, 1585, 1546, 1527. m/z (%):
5 21 3
þ þ
352 (M , 6.51), 176 (M /2, 100). Anal. C H N O .
22 28 2 2
8

4206
X. Wang, Y. Zhang / Tetrahedron 59 (2003) 4201–4207
Calcd C, 74.97; H, 8.01; N, 7.95. Found C, 74.93; H, 8.10; N,
7
(23.03). Anal. C H N Cl O. Calcd C, 62.84; H, 3.43; N,
20 13 3 2
10.99; Found C, 62.93; H, 3.56; N, 10.85%.
.86%.
4
crystals, yield: 53%, mp: 160–1628C (lit., 163–1658C).
.2.17. 1,2-Di(2-furyl)-1,2-ethanedione (2i). Yellow
2
4.2.24. 1-(n-Pentanoylamido)-2-(2-n-butyl) benzimida-
zole (4m). Oily compound. dH (CDCl ): 7.86 (1H, br),
7
3
d : 7.78–7.79 (2H, m), 7.65–7.66 (2H, m), 6.64–6.65 (2H,
H
6.89–6.91 (2H, m), 6.44–6.50 (2H, m), 2.68 (2H, t, J¼
m). nmax(KBr)/cm2 : 3150, 3125, 1647, 1551, 1454.
1
7.6 Hz), 2.22 (2H, t, J¼7.6 Hz), 1.60–1.70 (4H, m), 1.37–
1
.44 (4H, m), 0.92–0.96 (6H, m). n (KBr)/cm2 : 3260,
3128, 2958, 2931, 2872, 1627, 1588, 1492. m/z (%): 274
1
max
4.2.18. vic-Di(1H-1,2,3-benzotriazol-1-yl)alkene (3).
1
Yellow needles, yield: 68%, mp 138–1408C. H NMR
þ
C H N O. Calcd C, 70.30; H, 8.48; N, 15.37. Found C,
þ
(M þ1, 27.83), 273 (M , 17.94), 189 (100). Anal.
(
400 MHz, CDCl ): 8.72–8.74 (2H, d, J¼8.4 Hz), 8.50 (2H,
3
16 23 3
d, J¼8.4 Hz). 8.05 (2H, d, J¼8.0 Hz), 7.93–7.95 (2H, m),
70.45; H, 8.62; N, 15.29%.
7
1
.78–7.80 (2H, m), 7.10 (4H, d, J¼8.8 Hz), 3.93 (6H, s).
3
C NMR (100 MHz, CDCl ): 162.54, 159.74, 146.15,
3
4.2.25. 1-(n-Heptanoylamido)-2-(2-n-hexyl) benzimida-
zole (4n). White crystals, mp: 70–728C. d (CDCl ): 7.89
1
5
1
7
41.21, 135.40, 130.55, 129.32, 128.98, 128.25, 114.40,
5.48. nmax: 1605 (CvC), 1504 cm . m/z (%): 237 (M /2,
H
3
2
1
þ
.88), 209 (100), 166 (38.38). Anal. C H N O . Calcd C,
(1H, br), 6.91–6.94 (2H, m), 6.46–6.48 (1H, m), 5.90 (1H,
s), 2.66 (2H, t, J¼7.6 Hz), 2.23 (2H, t, J¼7.6 Hz), 1.60–
1.70 (4H, m), 1.25–1.40 (12H, m), 0.88–0.90 (6H, m).
nmax(KBr)/cm2 : 3259, 2920, 2926, 2855, 1628, 1589,
2
8 22 6 2
0.89; H, 4.64; N, 17.72. Found C, 70.80; H, 4.59; N, 17.65%.
1
þ
þ
4.2.19. 1-Benzoylamido-2-phenyl benzimidazole (4a).
Yellow crystals, mp: 184–1868C. d : 8.06 (1H, br),
1492. m/z (%): 330 (M þ1, 15.04), 329 (M , 12.43), 217
(100). Anal. C H N O. Calcd C, 72.91; H, 9.48; N, 12.75.
20 31 3
H
7
m), 6.61–6.69 (2H, m). nmax(KBr)/cm : 3262, 3056, 1621,
.78–7.80 (2H, m), 7.35–7.55 (8H, m), 7.01–7.06 (2H,
2
Found C, 72.78; H, 9.62; N, 12.66%.
1
þ
1
575, 1521. m/z (%): 313 (M , 30.94), 208 (100), 105
4.2.26. 1-(n-Octanoylamido)-2-(2-n-octyl) benzimidazole
(4q). Oily compound. d (CDCl ): 7.85 (1H, br), 6.88–6.90
(
32.50). Anal. C H N O. Calcd C, 76.66; H, 4.83; N,
20 15 3
H
3
1
3.41. Found C, 76.58; H, 4.88; N, 13.31.
(2H, m), 6.48–6.59 (2H, m), 2.67 (2H, t, J¼7.6 Hz), 2.21
(
2H, t, J¼7.6 Hz), 1.60–1.70 (4H, m), 1.27–1.38 (20H, m),
0.86–0.89 (6H, m). n (KBr)/cm2 : 3261, 2955, 2926,
1
4.2.20. 1-(3-Chloro-benzoylamido)-2-(3-chlorophenyl)
benzimidazole (4b). Yellow crystals, mp: 182–1858C.
max
þ
(100). Anal. C H N O. Calcd C, 74.76; H, 10.20; N,
10.90. Found C, 74.68; H, 10.32; N, 10.76%.
2855, 1628, 1589, 1492. m/z (%): 386 (M þ1, 6.21), 245
d : 8.07 (1H, m), 7.84 (1H, d, J¼8.1 Hz), 7.65 (1H, d, J¼
H
24 39 3
7
.6 Hz), 7.53 (1H, s), 7.33–7.46 (5H, m), 7.05–7.06 (2H,
:
337, 3062, 1622, 1588, 1569, 1497. m/z (%): 383 (M ,
þ
m), 6.68–6.69 (1H, m), 6.50 (1H, s). nmax(KBr)/cm2
1
þ
.47), 381 (M , 14.18), 242 (100), 244 (33.63), 139 (29.90).
3
9
4.2.27. 1-(n-Nonanoylamido)-2-(2-nonyl) benzimidazole
(4r). White crystals, mp: 42–438C. d (CDCl ): 7.89 (1H,
br), 6.91–6.94 (2H, m), 6.46–6.48 (1H, m), 5.86 (1H, s),
H
3
Anal. C H N Cl O. Calcd C, 62.84; H, 3.43; N, 10.99.
2
0
13
3
2
Found C, 62.92; H, 3.58; N, 10.83.
2.66 (2H, t, J¼7.6 Hz), 2.23 (2H, t, J¼7.6 Hz), 1.63–1.70
(4H, m), 1.27–1.38 (24H, m), 0.86–0.89 (6H, m).
nmax(KBr)/cm : 3256, 2924, 2853, 1627, 1588, 1492. m/z
2
1
4.2.21. 1-(4-Chloro-benzoylamido)-2-(4-chlorophenyl)
benzimidazole (4c). Yellow crystals, mp: 250–2528C. dH
þ
C H N O. Calcd C, 75.50; H, 10.48; N, 10.16. Found C,
þ
(%): 414 (M þ1, 1.92), 413 (M , 5.68), 259 (100). Anal.
(
DMSO): 9.70 (1H, s), 7.91 (1H, d, J¼8.0 Hz), 7.73 (2H, d,
2
6 43 3
J¼8.6 Hz), 7.66 (2H, d, J¼8.8 Hz), 7.50–7.60 (2H, m),
75.59; H, 10.56; N, 10.08%.
.08–7.10 (1H, m), 6.95–7.00 (2H, m). n (KBr)/cm2
1
:
7
3
7
max
þ
.88), 381 (M , 11.57), 242 (100), 244 (33.36), 139 (30.75).
358, 1653, 1619, 1589, 1568, 1559. m/z (%): 383 (M ,
þ
4.2.28. 1-(c-Hexylacetamido)-2-(2-c-hexyl) benzimida-
zole (4s). White crystals, mp: 229–2318C. d (CDCl ): 7.88
(1H, br), 6.89–6.92 (2H, m), 6.45–6.47 (1H, m), 5.81 (1H, s),
H
3
Anal. C H N Cl O. Calcd C, 62.84; H, 3.43; N, 10.99;
2
0
13
3
2
Found C, 62.72; H, 3.57; N, 10.84.
3.14–3.20 (1H, m), 2.11–2.17 (2H, m), 1.70–1.94 (10H, m),
1
1
.26–1.37 (10H, m). nmax(KBr)/cm2 : 3243, 3210, 3125,
þ
325(M , 7.76), 215(100). Anal. C H N O. Calcd C, 73.81;
4.2.22. 1-(4-Methyl-benzoylamido)-2-(4-methylphenyl)
benzimidazole (4f). Yellow crystals, mp: 197–1998C. dH:
2929, 2850, 1620, 1586, 1492. m/z (%): 326 (M þ1, 2.12),
þ
H, 8.36; N, 12.91. Found C, 73.90; H, 8.45; N, 12.83%.
20
27 3
8
.07 (1H, br), 7.71 (2H, d, J¼8.1 Hz), 7.46 (2H, d, J¼
8
s), 6.65–6.68 (1H, m), 2.40 (3H, s), 2.36 (3H, s). nmax(KBr)/
.2 Hz), 7.16–7.26 (4H, m), 6.99–7.02 (2H, m), 6.75 (1H,
4.2.29. 1-(Propionylamido)-2-(2-ethyl) benzimidazole
26
2
1
cm : 3245, 3198, 2967, 2919, 1610, 1586, 1532. m/z (%):
þ
(4t). White crystals, mp: 164–1668C (lit., 142–1488C).
d (CDCl ): 7.91 (1H, br), 6.90–6.94 (2H, m), 6.46–6.48
3
41 (M , 35.92), 222 (100), 119 (46.96). Anal. C H N O.
2
2
19
3
H
3
Calcd C, 77.40; H, 5.61; N, 12.31. Found C, 77.31; H, 5.70;
N, 12.19.
(1H, m), 5.94 (1H, s), 2.69 (2H, q, J¼7.6 Hz), 2.26 (2H, q,
1
3
J¼7.6 Hz), 1.15–1.23 (6H, m). C NMR: 172.14, 152.66,
1
32.04, 125.13, 124.97, 122.98, 121.03, 112.47, 27.02,
25.36, 9.63, 8.48. nmax (KBr)/cm2 : 3356, 3129, 2972,
1
4
.2.23. 1-(2-Chloro-benzoylamido)-2-(2-chlorophenyl)
benzimidazole (4p). Light yellow crystals, mp: 214–
168C. d (CDCl ): 8.16 (1H, s), 7.22–7.48 (8H, m), 7.10
2937, 1625, 1586, 1530, 1492.
2
H
3
2
1
(
3
2H, s), 6.66 (1H, s), 6.55 (1H, s). nmax(KBr)/cm : 3206,
123, 3065, 3000, 1629, 1586, 1518, 1491. m/z (%): 383
4.2.30. 1-(Acetamido)-2-(2-methyl) benzimidazole (4u).
2
6
White crystals, mp: 210–2128C (lit., 203–2048C). dH
(CDCl ): 7.88 (1H, br), 6.93–6.95 (2H, m), 6.46–6.48 (1H,
þ
þ
(
M , 11.84), 381 (M , 18.22), 242 (100), 244 (32.71), 139
3

X. Wang, Y. Zhang / Tetrahedron 59 (2003) 4201–4207
4207
1
3
m), 5.99 (1H, s), 2.30 (3H, s), 2.00 (3H, s). C NMR:
known for its rapid decarbonylation. See: (a) Lunazzi, L.;
Ingold, K. U.; Scalano, J. C. J. Phys. Chem. 1983, 87, 529.
(b) Turro, N. J.; Gold, I. R.; Baretz, B. H. J. Phys. Chem. 1983,
87, 531.
1
1
1
68.79, 148.89, 131.86, 125.29, 124.51, 123.15, 121.17,
2
1
12.49, 22.50, 18.19. nmax(KBr)/cm : 3257, 3127, 2972,
633, 1583, 1492.
1
4. Ogawa, A.; Takami, N.; Sekiguchi, M.; Ryu, I.; Kambe, N.;
Sonoda, N. J. Am. Chem. Soc. 1992, 114, 8729.
Acknowledgements
15. Katritzky, A. R.; Yang, B.; Jiang, J.; Steel, P. J. J. Org. Chem.
995, 60, 246.
1
We are grateful to the National Natural Science Foundation
of China (Project No. 29872010) and the NSF of Zhejiang
province for financial support.
16. (a) Ullmann, F. Liegigs. Ann. Chem. 1904, 332, 82. (b) Coker,
G. G.; Plant, S. G. P.; Turner, P. B. J. Chem. Soc. 1951, 110.
17. Ashton, B. W.; Suschitzky, H. J. Chem. Soc. 1957, 4559.
1
8. (a) Ohashi, M.; Tsujimato, K.; Yonezawa, T. J. Chem. Soc.,
Chem. Commun. 1970, 1089. (b) Hubert, A. J. J. Chem. Soc. C
1969, 1334. (c) Burgess, E. M.; Carithers, R.; Mccullagh, L.
J. Am Chem. Soc. 1968, 90, 1923.
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3
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23. N-Acylbenzotriazoles are efficient acylating agents which
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25. Thomas, L. G.; 3rd ed. Heterocyclic Chemistry; Addison
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8
210.
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1
2. (a) Evans, D. F.; Fazakerley, G. V.; Phillips, R. F. J. Chem.
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z
3. A relevant report was about PhCH
2
CO radical, which is