New 1,2,4,5-tetrakis-(N-imidazoliniummethyl)benzene and 1,2,4,5-tetrakis-(N-benzimidazoliummethyl)benzene salts as N-heterocyclic tetracarbene precursors: synthesis and involvement in ruthenium-catalyzed allylation reactions

Article abstract of DOI:10.1016/j.tet.2009.12.004

New tetraimidazolinium and tetrabenzimidazolium salts have been prepared. Upon reaction with ^tBuOK, they generate carbene ligands, which were associated in situ to [RuCp*(MeCN)₃]PF₆ to produce new ruthenium catalysts that

Full text of DOI:10.1016/j.tet.2009.12.004

Tetrahedron 66 (2010) 1346–1351
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Tetrahedron
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New 1,2,4,5-tetrakis-(N-imidazoliniummethyl)benzene and 1,2,4,5-tetrakis-
(N-benzimidazoliummethyl)benzene salts as N-heterocyclic tetracarbene
precursors: synthesis and involvement in ruthenium-catalyzed allylation
reactions
a
a
a,
b
c,
*
*
¨
Nevin Gu¨rbu¨z , Serpil Demir , Ismail Ozdemir , Bekir Cetinkaya , Christian Bruneau
a Ino¨nu¨ University, Faculty of Science and Art, Department of Chemistry, 44280 Malatya, Turkey
b Ege University, Department of Chemistry, Bornova, 35100 Izmir, Turkey
c
´
´
´
Universite de Rennes, UMR 6226: CNRSdUniversite de Rennes, Sciences chimiques de Rennes, Catalyse et Organometalliques, Campus de Beaulieu, 35042 Rennes, France
a r t i c l e i n f o
a b s t r a c t
New tetraimidazolinium and tetrabenzimidazolium salts have been prepared. Upon reaction with tBuOK,
they generate carbene ligands, which were associated in situ to [RuCp*(MeCN)3]PF6 to produce new
ruthenium catalysts that are active for the substitution of allylic substrates by amines, phenols, and
carbonucleophiles. The influence of the N-heterocyclic core as well as that of the N-substitutents at the
periphery of the salts, on reactivity and regioselectivity have been examined.
Article history:
Received 21 September 2009
Received in revised form 24 November 2009
Accepted 1 December 2009
Available online 6 December 2009
Ó 2009 Elsevier Ltd. All rights reserved.
Keywords:
N-Heterocyclic carbene ligand
Ruthenium
Allylation
Homogeneous catalysis
13
1. Introduction
*
[RuCp (phosphine)(MeCN)2]PF6,
and [RuCp (allyl)(2-quinoline-
*
carboxylato)]PF614 have shown remarkable regioselectivities.
Recently, N-heterocyclic carbene-containing metal complexes
have revealed excellent catalytic properties in a wide range of metal-
catalyzed transformations.15 As far as ruthenium is concerned, the
main applications are in the field of olefin and enyne metathesis,16
and examples have also appeared in other catalytic reactions such as
enyne cycloisomerization,17 hydrogen transfer reduction of ke-
tones,18,19 oxidative cleavage of alkenes,19 Friedlaender quinoline
The substitution of allylic susbstrates via allyl-metal in-
termediates is recognized as a powerful reaction in organic synthesis
for C–C and C-heteroatom bond formation in a controlled manner.1
Several transition metals including palladium,2 molybdenum,3 irid-
ium,4 rhodium,5 tungsten,6 nickel,7 iron,8 and ruthenium,9 exhibiting
different specificities in terms of regioselectivity properties have
been used for this purpose. In this context, the regioselectivity
control is of crucial importance when unsymmetrical allylic sub-
strates are involved. We have reported that cationic Cp*-containing
ruthenium(II) complexes provided an easy activation of allylic ha-
lides and carbonates to form allylic ruthenium(IV) complexes, and
were excellent catalysts for nucleophilic substitution with a large
scope of nucleophiles, leading to highly regioselective formation of
branched allylic products from unsymmetrical allylic substrates.10
synthesis,20
actions,22 and aromatic C–H bond activation/functionalization.23
We have alreadyshown that in the presence of [RuCp (MeCN)3]PF6
b
-alkylation of secondary alcohols,21 tandem re-
*
and after deprotonation by tBuOK, N-alkyl- and N-benzyl-substituted
benzimidazolium24 as well as N-benzyl-substituted imidazolinium
and tetrahydropyrimidinium salts24b were able to generate efficient
catalysts, likely via Ru-carbene species, to perform regioselective al-
kylation of cinnamyl carbonate by dimethyl malonate and 1,3-dike-
tones, as well as etherification of allylic halides by phenols. With the
objective of understanding the influence of steric and electronic ef-
fects, we have prepared new N-heterocyclic tetracarbene precursors
namely tetraimidazolinium 1, and benzimidazolium 2 bromides
(Scheme 1), and studied the catalytic efficiencies of in situ generated
ruthenium systems based on the association of the corresponding
The nature of the other ancillary ligands associated to Cp
a determining influence on the activity and regioselectivity of the
catalyst. [RuCp
(MeCN)3]PF6(I),11 [RuCp (bipyridine)(MeCN)]PF6,12
*
have
*
*
* Corresponding authors.
polycarbenes with the RuCp motif.
*
E-mail address: christian.bruneau@univ-rennes1.fr (C. Bruneau).
0040-4020/$ – see front matter Ó 2009 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2009.12.004

N. Gu¨rbu¨z et al. / Tetrahedron 66 (2010) 1346–1351
1347
R
R
The 1H NMR data show that the acidic C(2) protons of the imi-
dazolinium salts (8.71–9.55 ppm) are less downfield shielded than
the benzimidazolium salts (10.31–10.61 ppm), which indicates
a significant difference of the acidity of these protons (Table 1).
Comparison of 13C chemical shifts of the C(2) carbon reveals that
the values are almost constant in a series but differ of about
14.5 ppm from one series to the other (157.5 ppm for compounds 1,
and 143 ppm for compounds 2).
R
R
N
N
N
N
+
+
+
+
N
N
N
N
, 4 Br-
, 4 Br-
N
+
N
+
N
+
N
+
N
N
N
N
Table 1
1H NMR data for H(2) (
salts
d
ppm); 13C NMR for C(2) (
d
ppm);
n
(CN) (cmꢁ1) of the NHC
R
R
R
R
1
2
1a
1b
1c
9.55; 157.6; 1661
8.71; 157.2; 1661
9.51; 157.6; 1653
2a
2b
2c
10.49; 142.9; 1569
10.61; 143.1; 1607
10.31; 142.9; 1569
Scheme 1. General formulae of the new tetrazolium 1 and 2.
2. Results and discussion
There is also a noticeable influence of the nature of the N-het-
erocycle on the infrared C–N vibration as the observed wavelengths
are around 1660 cmꢁ1 for compounds 1a–c and in the range 1569–
1607 for the benzimidazolium salts 2a–c. The lowest frequencies
correspond to the benzimidazolium salts, which is an indication of
the influence of the benzimidazole structure (due to higher elec-
tron delocalization). Apparently, as can be deduced from the
spectroscopic data of the azolium fragment, the electronic in-
fluence of the aromatic or aliphatic substituents at the periphery of
these salts is less important than that of the N-heterocycle core.
2.1. Synthesis of tetrazolium salts
Three tetraimidazolinium bromides (1a–c) and three tetrabenzi-
midazolium bromides (2a–c) were prepared according to a known
method.15f,25 The condensation of 1,2,4,5-tetrakis(bromomethyl)-
benzene with 1-alkylimidazoline or 1-alkylbenzimidazole in DMF at
80 ꢀC for 10 h led to the formation of the corresponding tetrabromide
salts in good yields (75–94%) (Scheme 2).
2.2. In situ generation of ruthenium catalysts
N
N
N
N+
N
+
The characterization of complexes arising from coordination of
the carbenes resulting from deprotonation of the salts 1 and 2 to
Br- Br-
Br- Br-
+
+
N
N
N
a [RuCp ] centre could not be achieved. However, catalytic systems
*
were generated as follows: the tetrazolium salts were first
1a (92%)
2a (81%)
t
treated with 4 equiv of BuOK in THF at 50 ꢀC during 2 h under
N
N
N
inert atmosphere, and cooled down to room temperature.24,26
N+
N
+
Br- Br-
+
Br- Br-
+
[RuCp (MeCN)3]PF6(I) (2 equiv with respect to the tetrazolium salt),
*
N
N
N
which contains labile acetonitrile able to exchange with more co-
ordinating ligands, such as bipyridine12 or phosphine,13 was then
added to the solution and the mixture was heated at 50 ꢀC for 2 h.
After removal of the solvent, a brown solid was collected. It was not
possible to obtain crystallization and it was impossible to analyze
the NMR spectra. Even though we were not able to characterize an
organometallic complex, it is assumed, based on previous works27
that coordination of carbene moiety was involved in the formation
MeO
MeO
OMe
OMe
OMe
MeO
N
N+
N
N
N
+
Br- Br-
Br- Br-
of [RuCp (carbene)x] species. The complexity of the mixture is
*
+
+
N
N
N
probably due to the presence of various species resulting from the
presence of uncoordinated carbene moieties that can either be de-
graded or coupled to give either intra- or intermolecular olefinic
linkage. This solid was directly used in catalytic nucleophilic sub-
stitution reactions from allylic substrates.
1b (94%)
2b (79%)
N
N+
N
N
N
+
Br- Br-
+
Br- Br-
+
N
N
N
3. Ruthenium-catalyzed nucleophilic allylic substitution
3.1. Substitution of cinnamyl chloride by amines
MeO
OMe
OMe
OMe
N
MeO
MeO
MeO
OMe
The substitution in the presence of catalytic amounts of the
previously prepared ruthenium species was first attempted
starting from cinnamyl chloride 3, and aniline as aromatic amine,
cyclohexylamine as primary aliphatic amine, and pyrrolidine and
piperidine as secondary aliphatic amines (Scheme 3). The catalyst
N
N+
N
N
+
Br- Br-
+
+
Br- Br-
N
N
N
1c (85%)
2c (75%)
precursor was prepared from 3 mol % of [RuCp (MeCN)3][PF6] and
*
N
N+
N
N
N
1.5 mol % of tetrazolium salt, which potentially represents two
carbene units per ruthenium centre. The reactions were per-
formed at room temperature for 10 h in acetonitrile. Comparative
results are presented in Table 2. The substitution with aniline in
the absence of ligand led to the formation of the linear product 6a
+
Br- Br-
+
Br- Br-
+
N
N
N
MeO
Scheme 2. Preparation of symmetrical tetrazolium salts.
OMe

1348
N. Gu¨rbu¨z et al. / Tetrahedron 66 (2010) 1346–1351
as major compound (Table 2, entry 1). The presence of a ligand had
an influence on the 5a/6a ratio but no good regioselectivity in
favour of the branched product 5a was observed. The reaction with
the primary aliphatic cyclohexylamine showed a slight favoured
formation of the branched product 5b (entries 9–14) as compared
to the reaction without additional ligand (entry 8), but the regio-
selectivity remained very poor. From the secondary amines 4c–d,
the regioselectivities in 5c–d and 6c–d were generally not high
and the formation of the major product could not be predicted.
However, the role of the ligand was clearly evidenced by the fact
that from pyrrolidine, it was possible to obtained 5c or 6c as major
product by changing from 2a (entry 18) to 1b (entry 16) as ligand
precursor. It is also noteworthy that the presence of the carbene
ligand enhanced the reaction rate as compared to experiments
we studied the reaction of cinnamyl chloride with various phenols
in the presence of K2CO3 as a base (Scheme 4). Thus, 0.6 mmol of
phenol 7, 0.5 mmol of cinnamyl chloride 3, 0.6 mmol of potassium
carbonate, 0.015 mmol of ruthenium catalyst were stirred in ace-
tonitrile at room temperature. Under these standard conditions full
conversion of cinnamyl chloride was obtained after 10 h reaction
time. In a blank experiment carried out with phenol and cinnamyl
chloride without ruthenium catalyst under the standard condi-
tions, a very low yield of the linear ether 9a, exclusively, was
detected. When the reaction was performed from cinnamyl chlo-
ride 3, p-methoxyphenol 7b, and the deprotonated tetrazolium salt
2a in the presence of potassium carbonate but without ruthenium
precursor at room temperature during 15 h, 50% conversion of
3 was observed but the linear product 9b was the major product
(8b/9b¼20/80) as compared to 91:9 in the presence of ruthenium.
This clearly shows that there is a ruthenium–ligand interaction
during the catalytic reaction.The results are collected in Table 3.
carried out from [RuCp
(entries 1, 8, 21).
*
(MeCN)3][PF6] without additional ligand
R1
Ph
R2
N
Ar
O
5a-d
8a-c
Ph
Cl
[Ru cat.] (3 mol-%)
Ph
Cl
Ph
3
[Ru cat.] (3 mol-%)
+
+
3
MeCN, K2CO3
r.t., 10 h
R1
+
+
R1R2NH
4a-d
MeCN, K2CO3
r.t., 10 h
Ph
N
ArOH
7a-c
Ar
9a-c
R2
6a-d
Ph
OH
O
ArOH :
OH
OH
MeO
NH2
NH
NH
NH2
a
b
c
d
a
c
b
Scheme 4. Substitution of cinnamyl chloride by phenols.
Scheme 3. Substitution of cinnamyl chloride by amines.
Table 3
Ruthenium-catalyzed allylic etherification of cinnamyl chloride by phenolatea
Table 2
Ruthenium-catalyzed allylic substitution of cinnamyl chloride by aminea
Entry
Ligand precursor
ArOH
Products
8:9 Ratiob
Entry
Ligand precursor
Amine
Products
Conversion (%)
5:6 Ratiob
1
2
3
4
5
6
7
8
1a
1b
1c
2a
2b
2c
1a
1b
1c
2a
2b
2c
1a
1b
1c
2a
2b
2c
7a
7a
7a
7a
7a
7a
7b
7b
7b
7b
7b
7b
7c
7c
7c
7c
7c
7c
8a, 9a
8a, 9a
8a, 9a
8a, 9a
8a, 9a
8a, 9a
8b, 9b
8b, 9b
8b, 9b
8b, 9b
8b, 9b
8b, 9b
8c, 9c
8c, 9c
8c, 9c
8c, 9c
8c, 9c
8c, 9c
88:12
87:13
78:22
73:27
67:33
68:32
89:11
93:7
1
2
3
4
5
6
7
8
no
1a
1b
1c
2a
2b
2c
no
1a
1b
1c
2a
2b
2c
1a
1b
1c
2a
2b
2c
no
1a
1b
1c
2a
2b
2c
4a
4a
4a
4a
4a
4a
4a
4b
4b
4b
4b
4b
4b
4b
4c
4c
4c
4c
4c
4c
4d
4d
4d
4d
4d
4d
4d
5a, 6a
5a, 6a
5a, 6a
5a, 6a
5a, 6a
5a, 6a
5a, 6a
5b, 6b
5b, 6b
5b, 6b
5b, 6b
5b, 6b
5b, 6b
5b, 6b
5c, 6c
5c, 6c
5c, 6c
5c, 6c
5c, 6c
5c, 6c
5d, 6d
5d, 6d
5d, 6d
5d, 6d
5d, 6d
5d, 6d
5d, 6d
67
73
82
60
89
73
87
78
100
100
100
100
100
100
98
96
100
95
100
100
76
100
100
100
100
100
100
2:98
d:100
59:41
22:78
75:25
13:87
52:48
49:51
67:33
74:26
70:30
66:34
58:42
69:31
49:51
5:95
9
75:25
91:9
9
10
11
12
13
14
15
16
17
18
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
77:23
83:17
74:26
74:26
17:83
82:18
83:17
29:71
53:47
91:9
a
Conditions: 0.6 mmol of ArOH, 0.6 mmol of K2CO3, 0.5 mmol of cinnamyl
chloride, 0.015 mmol of [Cp*Ru(NCCH3)3]PF6, 0.0075 mmol of 1or 2 in 3 mL of
CH3CN, 10 h, room temperature, 100% conversion.
69:31
58:42
27:73
69:31
69:31
65:35
71:29
19:81
58:42
b
Determined by 1H NMR spectroscopy.
With phenol 7a and p-methoxyphenol 7b, the formation of
branched compounds 8a,b is favoured and the imidazolinium led to
better regioselectivities than the benzimidazolium-derived cata-
lysts. Thus, the catalytic system generated from 1b gave 8a:9a and
8b:9b ratios of 87:13 and 93:7, respectively. On the contrary, with
p-tert-butylphenol, the tetrabenzimidazolium salts 2a and 2b
provided the best results (Table 3, entries 16, 17). Whereas 1a and
1b on one side (entries 1 and 2; 7 and 8; 13 and 14), and 2a and 2b
on the other side (entries 4 and 5; 16 and 17), induced the same
type of regioselectivity depending on the nature of the phenol, 1c
and 2c showed lower regioselectivities and sometimes led to the
reverse regioisomer (Table 3, entries 15, 18). This might be due to
the aliphatic side chain of 1c and 2c as compared to the aromatic
motives in 1a,b and 2a,b. It is worth noting that starting from
a
Conditions: 0.6 mmol of amine, 0.6 mmol of K2CO3, 0.5 mmol of cinnamyl
chloride, 0.015 mmol of [RuCp*(NCCH3)3]PF6 (3 mol %), 0.0075 mmol (1.5 mol %) of
1 or 2 in 3 mL CH3CN, 10 h at room temperature.
b
Determined by 1H NMR spectroscopy.
3.2. Substitution of cinnamyl chloride by phenols
We have previously reported that [RuCp (MeCN)3]PF6(I) as
*
catalyst led to a very good regioselectivity in the substitution of
allylic chlorides by phenoxides.11 To evaluate the influence of our
new catalytic systems based on ruthenium–carbene active species,

N. Gu¨rbu¨z et al. / Tetrahedron 66 (2010) 1346–1351
1349
Table 4
phenol, the catalytic system arising from the tetraimidazolinium
Ruthenium-catalyzed allylic alkylation of cinnamyl carbonatea
1a,b and tetrabenzimidazolium bromides 2a,b led to a regiose-
lectivity in favour of the branched isomer 8a, which contrasts with
the reverse regioselectivity observed with catalytic systems gen-
erated from monoimidazolinium 10 and monobenzimidazolium
salts 11, which favoured the formation of the linear product 9a.24b
However, under similar conditions, the regioselectivities induced
by the tetrazolium precursors 1a,b and 2a,b are in line with those
obtained with the monobenzimidazolium salts 12 with non-ben-
zylic N-substitutents24a (Scheme 5).
Entry
Ligand precursor
Nucleophile
Products
Ratio (7:8)b
1
2
3
4
5
6
7
8
no
1a
1b
1c
2a
2b
2c
1a
1b
1c
2a
2b
2c
no
1a
1b
1c
2a
2b
2c
no
1a
1b
1c
2a
2b
2c
14a
14a
14a
14a
14a
14a
14a
14b
14b
14b
14b
14b
14b
14c
14c
14c
14c
14c
14c
14c
14d
14d
14d
14d
14d
14d
14d
15a, 16a
15a, 16a
15a, 16a
15a, 16a
15a, 16a
15a, 16a
15a, 16a
15b, 16b
15b, 16b
15b, 16b
15b, 16b
15b, 16b
15b, 16b
15c, 16c
15c, 16c
15c, 16c
15c, 16c
15c, 16c
15c, 16c
15c, 16c
15d, 16d
15d, 16d
15d, 16d
15d, 16d
15d, 16d
15d, 16d
15d, 16d
80:20c
86:14
82:18
83:17
83:17
87:13
78:22
91:9
90:10
91:9
93:7
92:8
93:7
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
X
N
N
N
_
_
_
+
+
+
H, Cl
H, Cl
H, Cl
N
N
N
70:30d
85:15
82:18
78:22
91:8
88:12
84:16
74:26e
73:27
76:24
74:26
72:28
74:26
76:24
Y
Ar (or Ar')
Ar
10
11
12
X= OMe, Ph
Y= OMe, NEt2, Ph
Ar, Ar'= methyl- methoxy-, and benzyloxy-
substituted phenyl
Scheme 5. Monoazolium salts used as carbene precursors.
3.3. Substitution of cinnamyl carbonate by carbonucleophiles
In a typical experiment, cinnamyl carbonate 13 (0.5 mmol), the
nucleophile 14 (0.6 mmol) and potassium carbonate (0.6 mmol)
were successively added to 0.015 mmol (based on ruthenium) of
the catalytic material in 3 mL of acetonitrile, and the resulting
mixture was stirred for 10 h at room temperature (Scheme 6).
a
Conditions: 0.6 mmol of nucleophile, 0.5 mmol of cinnamyl carbonate, 0.6 mmol
of K2CO3, 0.015 mmol of RuCp*(NCCH3)3]PF6 (3 mol %), 0.0075 mmol (1.5 mol %) of 1
or 2 in 3 mL CH3CN, 10 h at room temperature, complete conversion.
b
Determined by 1H NMR spectroscopy.
87% yield.
88% yield.
84% yield.
Z1
Z2
c
15a-d
d
Ph
Ph
13
OCO2Et
Z2
e
[Ru cat.] (3 mol-%)
MeCN, r.t., 10 h
+
+
Z1
Z1
14a-d
Ph
16a-d
Z2
but in terms of regioselectivity, the different catalytic systems
arising from all these azolium precursors are located at the same
level and do not exceed 90% with methyl malonate as common
reference.24b
a: Z1= Z2 = CO2Me; b: Z1= Z2 = COMe; c: Z1= COMe, Z2 = CO2Me; d: Z1= Z2 = COPh
Scheme 6. Substitution of cinnamyl carbonate by soft carbonucleophiles.
After concentration under vacuum and flash chromatography
over silica gel, the crude product was analyzed by 1H NMR, which
provided both the conversion and the branched to linear ratio (15B/
16L). The results are gathered in Table 4. A blank experiment carried
out without ruthenium source led to no conversion of the starting
4. Conclusions
New tetraimidazolinium and tetrabenzimidazolium salts, sym-
metrically attached to a 1,2,4,5-phenyl unit have been prepared and
fully characterized. After deprotonation with BuOK, the resulting
t
substrates. The reaction performed with [RuCp (MeCN)3]PF6 in the
*
species have been associated to a RuCp centre in order to generate
*
presence of potassium carbonate but no additional ligand under
otherwise identical conditions gave the products but the conver-
sion were only about 85% (Table 4, entries 1,14, 21). On the contrary,
in the presence of ligand, complete conversion of the cinnamyl
carbonate was obtained after 10 h at room temperature. These
observations provide clear evidence of the crucial role of the car-
bene ligands in these new catalytic systems. In all cases, the
regioselectivites were better than without carbene ligand. For
a given carbonucleophile, the influence of the carbene ligand 1 or 2
on regioselectivity was not important and the branched product 15
was always formed as the major compound. The best regiose-
lectivities were obtained from penta-2,4-dione 14b (around
9:1dTable 4, entries 8–13), and 1,3-diphenylpropan-1,3-dione 14d
led to 15d/16d ratio of about 3:1 (Table 4, entries 22–27), whereas
the 15/16 ratios obtained from dimethyl malonate 14a (Table 4,
entries 2–7) and methyl 3-oxobutanoate 14c (Table 4, entries 15–
20) were located around 5.7:1.
catalyst precursors for nucleophilic allylic substitution of cinnamyl
chloride and carbonate by amines, phenols, and carbonucleophiles.
All the catalytic systems are active for nucleophilic substitution of
non-symmetrical allylic substrates, and most of them lead to the
regioselective formation of branched products. However, the
presence of potentially chelating carbene ligands does not bring
significant improvement with respect to monodentate ligands
resulting from monodentate azolium salts.
5. Experimental section
5.1. General procedure for the preparation of the tetrazolium
salts (1a–c and 2a–c)
To a solution of 1-alkylimidazoline/benzimidazole (10 mmol) in
DMF (10 mL) was slowlyadded1,2,4,5-tetrakis(bromomethyl)benzene
(2.5 mmol) at 25 ꢀC and the resulting mixture was stirred at 80 ꢀC for
10 h. Diethyl ether (15 mL) was added to obtain a white crystalline
solid, which was filtered off. The solid was washed with diethyl ether
(3ꢂ15 mL), dried under vacuum. The crude product was recrystallized
from EtOH/Et2O.
Similar regioselectivities were obtained with ligand precursors
1c and 2c for C-allylation, showing a weak influence of the N-alkyl
substituents for these substrates.
As compared to the monocarbene precursors 10 and 11, a much
higher reactivity is obtained with the tetrazolium precursors,24b

1350
N. Gu¨rbu¨z et al. / Tetrahedron 66 (2010) 1346–1351
5.1.1. 1,2,4,5-Tetrakis-(N-2,4,6-trimethylbenzylimidazoliniumme-
(CH2C6H2(OCH3)3-4),
56.9
(CH2C6H2(OCH3)3-3,5),
52.2
thyl)benzene tetrabromide (1a)15f. Yield: 1.16 g (92%). Mp: 267–
(CH2C6H2(OCH3)3-3,4,5), 48.4 ((CH2)4C6H2). Anal. Calcd for
C78H82N8O12Br4: C, 57.01; H, 5.03; N, 6.82. Found: C, 57.10; H,
5.08; N, 6.86%.
268 ꢀC, n(CN)¼1661 cmꢁ1. 1H NMR (399.9 MHz, CDCl3)
¼9.55 (s, 4H,
d
NCHN), 8.11 (s, 2H, (CH2)4C6H2), 6.85 (s, 8H, CH2C6H2(CH3)3-2,4,6),
5.15 (s, 8H, (CH2)4C6H2), 4.86 (s, 8H, CH2C6H2(CH3)3-2,4,6), 4.14 and
3.78 (t, J¼10.2 Hz, 16H, NCH2CH2N), 2.35 (s, 24H, CH2C6H2(CH3)3-
2,6), 2.29 (s, 12H, CH2C6H2(CH3)3-4). 13C NMR (100.5 MHz, CDCl3)
5.1.6. 1,2,4,5-Tetrakis-(N-2-methoxyethylbenzimidazoliummethyl)-
benzene tetrabromide (2c). Yield: 0.86 g (75%). Mp: 128–129 ꢀC,
n(CN)¼1569 cmꢁ1
.
1H NMR (399.9 MHz, CDCl3)
d
¼10.31 (s, 4H,
d
¼157.6 (NCHN), 132.7 and 133.6 ((CH2)4C6H2), 138.9, 137.9, 129.8
NCHN), 8.43 (d, J¼8.4 Hz, 4H, NC6H4N), 8.12 (s, 2H, (CH2)4C6H2),
7.54–7.17 (m, 8H, NC6H4N), 7.64 (d, J¼8.4 Hz, 4H, NC6H4N), 6.32
(s, 8H, (CH2)4C6H2), 4.66 (t, J¼4.2 Hz, 8H, CH2CH2OCH3), 3.89 (t,
J¼4.2 Hz, 8H, CH2CH2OCH3), 3.28 (s, 12H, CH2CH2OCH3). 13C NMR
and 125.3 (CH2C6H2(CH3)3-2,4,6), 49.2 ((CH2)4C6H2), 48.0 and 48.3
(NCH2CH2N), 46.5 (CH2C6H2(CH3)3-2,4,6), 20.9 (CH2C6H2(CH3)3-4),
20.3 (CH2C6H2(CH3)3-2,6). Anal. Calcd for C62H82N8Br4: C, 59.15; H,
6.56; N, 8.90. Found: C, 59.18; H, 6.61; N, 8.86%.
(100.5 MHz, CDCl3)
d
¼142.9 (NCHN), 131.1 and 131.6
((CH2)4C6H2), 134.3, 126.9, 114.6 and 113.6 (NC6H4N), 70.5
(CH2CH2OCH3), 59.0 (CH2CH2OCH3), 48.4 ((CH2)4C6H2), 48.2
(CH2CH2OCH3). Anal. Calcd for C50H58N8O4Br4: C, 52.01; H, 5.06;
N, 9.70. Found: C, 52.09; H, 5.15; N, 9.68%.
5.1.2. 1,2,4,5-Tetrakis-(N-2,3,4,5,6-pentamethylbenzylimidazolinium-
methyl)benzene tetrabromide (1b). Yield: 1.29 g (94%). Mp: 307–
308 ꢀC, n(CN)¼1661 cmꢁ1. 1H NMR (399.9 MHz, DMSO-d6)
¼8.71 (s,
d
4H, NCHN), 7.68 (s, 2H, (CH2)4C6H2), 4.84 (s, 8H, (CH2)4C6H2), 4.76
(s, 8H, CH2C6(CH3)5-2,3,4,5,6), 3.78–3.75 and 3.87–3.48 (m, 16H,
5.2. Procedure for amination of cinnamyl chloride by amine
NCH2CH2N), 2.25, 2.21 and 2.19 (s, 60H, CH2C6(CH3)5-2,3,4,5,6). 13
C
NMR (100.5 MHz, CDCl3)
d
¼157.2 (NCHN), 133.8 and 133.1
To a degassed THF (5 mL) suspension of tetrazolium salt
(0.0075 mmol, 1.5 mol %) was added BuOK (3.4 mg, 0.030 mmol,
6 mol %), and the mixture was heated at 50 ꢀC for 2 h and then
((CH2)4C6H2), 135.9 and 126.7 (CH2C6(CH3)5-2,3,4,5,6), 48.9
((CH2)4C6H2), 48.5 and 47.9 (NCH2CH2N), 47.2 (CH2C6(CH3)5-
2,3,4,5,6), 17.4, 17.1 and 17.0 (CH2C6(CH3)5-2,3,4,5,6). Anal. Calcd for
C70H96N8Br4: C, 61.41; H, 7.07; N, 8.18. Found: C, 61.43; H, 7.11;
N, 8.16%.
t
cooled to room temperature. [Cp Ru(CH3CN)3][PF6] (7.6 mg,
*
0.015 mmol, 3 mol %) was added, and the solution was heated at
50 ꢀC for 2 h under argon. After cooling to room temperature, THF
was removed under vacuum. To the crude ruthenium–carbene
catalyst was successively added acetonitrile (3 mL), cinnamyl
chloride (166 mg, 1 mmol, 1 equiv), potassium carbonate (166 mg,
1.2 mmol, 1.2 equiv) and amine (113 mg, 1.2 mmol, 1.2 equiv). The
resulting solution was stirred overnight at room temperature. The
mixture was filtered through Celite, and after concentration under
vacuum, the crude mixture was analyzed by 1H NMR spectroscopy.
The product was then purified by column chromatography on silica
gel by using heptane as the eluant.
5.1.3. 1,2,4,5-Tetrakis-(N-n-butylimidazoliniummethyl)benzene
tetrabromide (1c). Yield: 0.81 g (85%). Mp: 275–276 ꢀC, n(CN)
¼1653 cmꢁ1
.
1H NMR (399.9 MHz, CDCl3)
d
¼9.51 (s, 4H, NCHN),
8.01 (s, 2H, (CH2)4C6H2), 5.13 (s, 8H, (CH2)4C6H2), 4.02–3.94 and
4.21–4.09 (m, 16H, NCH2CH2N), 3.52 (t, J¼7.5 Hz, 8H,
NCH2CH2CH2CH3), 1.59 (quint, J¼7.5 Hz, 8H, NCH2CH2CH2CH3),
1.31 (hex., J¼7.5 Hz, 8H, NCH2CH2CH2CH3), 0.883 (t, J¼7.5 Hz, 12H,
NCH2CH2CH2CH3). 13C NMR (100.5 MHz, CDCl3)
d
¼157.6 (NCHN),
133.6 and 133.1 ((CH2)4C6H2), 49.2 ((CH2)4C6H2), 48.8 and 48.2
(NCH2CH2N), (48.4 NCH2CH2CH2CH3), 29.2 (NCH2CH2CH2CH3),
19.7 (NCH2CH2CH2CH3), 13.6 (NCH2CH2CH2CH3). Anal. Calcd for
C38H66N8Br4: C, 47.81; H, 6.97; N, 11.74. Found: C, 47.77; H, 7.01;
N, 11.76%.
5.3. Procedure for etherification of cinnamyl chloride
by phenol
To a degassed THF (5 mL) suspension of tetrazolium salt
t
(0.0075 mmol, 1.5 mol %) was added BuOK (3.4 mg, 0.030 mmol,
6 mol %), and the mixture was heated at 50 ꢀC for 2 h and then
5.1.4. 1,2,4,5-Tetrakis-(N-2,4,6-trimethylbenzylbenzimidazoliumme-
thyl)benzene tetrabromide (2a). Yield: 1.17 g (81%). Mp: 300–
cooled to room temperature. [Cp Ru(CH3CN)3][PF6] (7.6 mg,
*
301 ꢀC, n(CN)¼1569 cmꢁ1
.
1H NMR (399.9 MHz, CDCl3)
d¼10.49 (s,
0.015 mmol, 3 mol %) was added, and the solution was heated at
50 ꢀC for 2 h under argon. After cooling to room temperature, THF
was removed under vacuum. To the crude ruthenium–carbene
catalyst was successively added acetonitrile (3 mL), cinnamyl
chloride (166 mg, 1 mmol, 1 equiv), potassium carbonate (166 mg,
1.2 mmol, 1.2 equiv) and phenol (113 mg, 1.2 mmol, 1.2 equiv). The
resulting solution was stirred overnight at room temperature. The
mixture was filtered through Celite, and after concentration under
vacuum, the crude mixture was analyzed by 1H NMR spectroscopy.
The product was then purified by column chromatography on silica
gel by using heptane as the eluant.
4H, NCHN), 8.56 (d, J¼8.4 Hz, 4H, NC6H4N), 7.64 (s, 2H, (CH2)4C6H2),
7.47 (t, J¼8.1 Hz, 4H, NC6H4N), 7.33 (t, J¼8.1 Hz, 4H, NC6H4N), 6.94
(m, 4H, NC6H4N), 6.91 (s, 8H, CH2C6H2(CH3)3-2,4,6), 6.38 (s, 8H,
(CH2)4C6H2), 5.87 (s, 8H, CH2C6H2(CH3)3-2,4,6), 2.31 (s, 24H,
CH2C6H2(CH3)3-2,6), 2.29 (s, 12H, CH2C6H2(CH3)3-4). 13C NMR
(100.5 MHz, CDCl3)
139.6, 138.3, 129.9 and 125.3 (CH2C6H2(CH3)3-2,4,6), 134.0, 133.6,
127.4, 127.2, 115.3 and 113.4 (NC6H4N), 48.6 ((CH2)4C6H2), 48.3
d
¼142.9 (NCHN), 131.2 and 132.0 ((CH2)4C6H2),
(CH2C6H2(CH3)3-2,4,6),
(CH2C6H2(CH3)3-2,6). Anal. Calcd for C78H82N8Br4: C, 64.56; H, 5.70;
N, 7.72. Found: C, 64.63; H, 5.65; N, 7.76%.
21.1
(CH2C6H2(CH3)3-4),
20.7
5.4. Procedure for allylic alkylation of cinnamyl carbonate
by carbonucleophile
5.1.5. 1,2,4,5-Tetrakis-(N-3,4,5-trimethoxybenzylbenzimidazolium-
methyl)benzene tetrabromide (2b). Yield: 1.30 g (79%). Mp: 205–
206 ꢀC, n(CN)¼1607 cmꢁ1. 1H NMR (399.9 MHz, CDCl3)
d
¼10.61 (s,
To a degassed THF (5 mL) suspension of tetrazolium salt
(0.0075 mmol, 1.5 mol %) was added BuOK (3.4 mg, 0.030 mmol,
6 mol %), and the mixture was heated at 50 ꢀC for 2 h under argon
t
4H, NCHN), 8.27 (d, J¼8.4 Hz, 4H, NC6H4N), 8.49 (s, 2H,
(CH2)4C6H2), 7.38 (d, J¼8.4 Hz, 4H, NC6H4N), 7.29–7.13 (m, 8H,
NC6H4N), 6.96 (s, 8H, CH2C6H2(OCH3)3-3,4,5), 6.35 (s, 8H,
(CH2)4C6H2), 5.65 (s, 8H, CH2C6H2(OCH3)3-3,4,5), 3.79 (s, 24H,
CH2C6H2(OCH3)3-3,5), 3.76 (s, 12H, CH2C6H2(OCH3)3-4). 13C NMR
and then cooled to room temperature. [Cp Ru(CH3CN)3][PF6]
*
(7.6 mg, 0.015 mmol, 3 mol %) was added, and the solution was
heated at 50 ꢀC for 2 h. After cooling to room temperature, THF was
removed under vacuum. To the crude ruthenium–carbene catalyst
was successively added acetonitrile (3 mL), cinnamyl carbonate
(221 mg, 1 mmol, 1 equiv), potassium carbonate (166 mg, 1.2 mmol,
(100.5 MHz, CDCl3)
d
¼143.1 (NCHN), 131.4 and 130.5
((CH2)4C6H2), 153.6, 138.3, 128.2 and 106.7 (CH2C6H2(OCH3)3-
3,4,5), 134.3, 126.8, 114.4 and 113.6 (NC6H4N), 60.8

N. Gu¨rbu¨z et al. / Tetrahedron 66 (2010) 1346–1351
1351
10. (a) Renaud, J.-L.; Bruneau, C.; Demerseman, B. Synlett 2003, 408; (b) Mbaye, M.
D.; Demerseman, B.; Renaud, J.-L.; Bruneau, C. J. Organomet. Chem. 2005, 690,
2149; (c) Renaud, J.-L.; Bruneau, C.; Demerseman, B.; Mbaye, M. D. Curr. Org.
Chem. 2006, 10, 115; (d) Bruneau, C.; Renaud, J.-L.; Demerseman, B. Chem.dEur.
J 2006, 12, 5178.
11. Mbaye, M. D.; Demerseman, B.; Renaud, J.-L.; Toupet, L.; Bruneau, C. Adv. Synth.
Catal. 2004, 346, 835.
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Chem., Int. Ed. 2003, 42, 5066.
1.2 equiv) and dimethyl malonate (158 mg, 1.2 mmol, 1.2 equiv).
The resulting solution was stirred overnight at room temperature.
The mixture was filtered through Celite, and after concentration
under vacuum, the crude mixture was analyzed by 1H NMR spec-
troscopy. The product was then purified by column chromatogra-
phy on silica gel by using heptane as the eluant.
13. Demerseman, B.; Renaud, J.-L.; Toupet, L.; Hubert, C.; Bruneau, C. Eur. J. Inorg.
Chem. 2006, 1371.
Acknowledgements
14. (a) Zhang, H.-J.; Demerseman, B.; Toupet, L.; Xi, Z.; Bruneau, C. Adv. Synth. Catal.
2008, 350, 1601; (b) Achard, M.; Derrien, N.; Zhang, H.-J.; Demerseman, B.;
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The authors are grateful to the CNRS-TUBITAK (TBAG-U/181
(106T716)) bilateral agreement for financial support.
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