Benzylic imidazolidinium, 3,4,5,6-tetrahydropyrimidinium and benzimidazolium salts: Applications in ruthenium-catalyzed allylic substitution reactions

Article abstract of DOI:10.1002/ejoc.200800007

Imidazolidinium, tetrahydropyrimidinium and benzimidazolium salts were prepared. Upon reaction with tBuOK, they generate carbene ligands, which were associated in situ to [RuCp*(MeCN)₃]PF₆ to produce ruthenium catalysts that are acti

Full text of DOI:10.1002/ejoc.200800007

FULL PAPER
DOI: 10.1002/ejoc.200800007
Benzylic Imidazolidinium, 3,4,5,6-Tetrahydropyrimidinium and
Benzimidazolium Salts: Applications in Ruthenium-Catalyzed Allylic
Substitution Reactions
Sedat Yasar,[a] Ismail Özdemir,[a] Bekir Cetinkaya,[b] Jean-Luc Renaud,[c] and
Christian Bruneau*[c]
Keywords: Carbene ligands / Nitrogen heterocycles / Ruthenium / Allylation / Homogeneous catalysis
Imidazolidinium, tetrahydropyrimidinium and benzimidazol-
ium salts were prepared. Upon reaction with tBuOK, they
generate carbene ligands, which were associated in situ to
[RuCp*(MeCN)3]PF6 to produce ruthenium catalysts that are
active for the substitution of allylic substrates by dimethyl
malonate as a carbonucleophile and phenol. The influences
of the N-heterocyclic structures, as well as that of the ben-
zylic N-substituents, on the reactivity and regioselectivity
were examined.
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2008)
Introduction
The substitution of allylic substrates via π-allyl or σ-allyl range of metal-catalyzed transformations.[14] As far as ru-
metal intermediates is recognized as a powerful reaction in thenium is concerned, the main applications are in the field
organic synthesis for C–C and C-heteroatom bond forma- of olefin and enyne metathesis,[15] but a few examples have
tion in a controlled manner.[1] Several transition metals in- appeared in other catalytic reactions such as enyne cyclo-
cluding palladium,[2] molybdenum,[3] iridium,[4] rhodium,[5] isomerization,[16] hydrogen transfer reduction of ketones,[17]
tungsten,[6] nickel,[7] iron[8] and ruthenium,[9] which exhibit oxidative cleavage of alkenes[18] or Friedlaender quinoline
different specificities in terms of regioselectivity properties, synthesis.[19]
have been used for this purpose. In this context, the regiose-
In a previous communication, we showed that N-alkyl-
lectivity control is of crucial importance when unsymmetri- substituted benzimidazolylidene–ruthenium complexes
cal allylic derivatives are involved. We reported that cationic were also efficient catalysts to perform regioselective alky-
Cp*-containing ruthenium(II) complexes provided easy ac- lation of cinnamyl carbonate by dimethyl malonate and 1,3-
tivation of allylic halides and carbonates to form allylic ru- diketones, as well as etherification of allylic halides by phe-
thenium(IV) complexes. They were also excellent catalysts nols, respectively.[20] It is noteworthy that only a few exam-
for nucleophilic substitution with a large scope of nucleo- ples of the use of N-heterocyclic carbene complexes have
philes, which led to highly regioselective formation of been reported in allylic substitution reactions.[21]
branched allylic products from unsymmetrical allylic sub-
With the objective of understanding the influence of
strates.[10] The nature of the other ancillary ligands associ- their steric and electronic effects, we prepared a variety of
ated to Cp* had a determining influence on the activity and new N-heterocyclic carbene precursors such as imidazolidi-
regioselectivity of the catalyst. [RuCp*(MeCN)3]PF6 (I),[11] nium A, tetrahydropyrimidinium B and benzimidazolium C
[12]
[RuCp*(bipyridine)(MeCN)]PF6
phane)(MeCN)2]PF6
tivities.
and [RuCp*(phos- halides (Figure 1), and we studied the catalytic efficiencies
[13]
have shown remarkable regioselec- of in situ generated ruthenium systems on the basis of the
association of the corresponding carbenes with the RuCp*
Recently, N-heterocyclic carbene-containing metal com- motif.
plexes have revealed excellent catalytic properties in a wide
[a] Inönü University, Faculty of Science and Art, Department of
Chemistry,
44069 Malatya, Turkey
[b] Ege University, Department of Chemistry, Bornova,
35100 Izmir, Turkey
[c] Université de Rennes, UMR 6226: CNRS – Université de
Figure 1. N-Heterocyclic carbene precursors: imidazolidinium A,
tetrahydropyrimidinium B and benzimidazolium C chlorides.
Rennes, Sciences Chimiques de Rennes,
Campus de Beaulieu, 35042 Rennes, France
2142
© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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Ruthenium-Catalyzed Allylic Substitution Reactions
continuous elimination of ethanol led to the formation of
the expected imidazolidinium, tetrahydropyrimidinium and
benzimidazolium chlorides in excellent yields.
Results and Discussion
Synthesis of Imidazolinium, Tetrahydropyrimidinium and
Benzimidazolium Salts
The nonsymmetrical imidazolidinium salts A1–5 were
also synthesized. They were obtained upon reaction of a
benzyl halide (chloride or bromide) with 1-(2,4,6-trimeth-
ylbenzyl)imidazoline in dimethylformamide at room tem-
perature.[23] All these salts (Figures 2, 3 and 4) were isolated
A series of symmetrical and unsymmetrical 1,3-N,N-het-
erocyclic azolium salts were prepared according to known
methods.[22] The symmetrical N-heterocyclic carbene pre-
cursors A6–9, B1–7 and C1–4 were prepared according to
the general reaction pathway depicted in Scheme 1. Treat-
ment of 1,2-ethylenediamine, 1,3-propylenediamine and
1,2-diaminobenzene with an aromatic aldehyde (2 equiv.) in
methanol at room temperature led to the formation of the
corresponding diimine. Their reduction with sodium
borohydride in methanol, followed by treatment with trieth-
ylorthoformate in the presence of ammonium chloride with
1
as solids in very good yields and fully characterized by H
NMR, 13C NMR and IR spectroscopy, elemental analyses,
and their melting points were determined.
Scheme 1. Preparation of symmetrical N-heterocyclic salts.
Figure 3. Tetrahydropyrimidinium salts.
Figure 4. Benzimidazolium salts.
A fine study of the chemical shifts of the acidic C(2) pro-
tons shows that they are located in the range 7.82–
11.70 ppm, which indicates a significant difference in the
acidity of these protons (Table 1). Comparison of the chem-
ical shifts in the three series where the aromatic substituents
Figure 2. Imidazolidinium salts.
Eur. J. Org. Chem. 2008, 2142–2149
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FULL PAPER
1
Table 1. H NMR spectroscopic data for the C(2)–H proton (δ, ppm); ν(CN) [cm–1] of the NHC salts.
A1
A5
A9
B1
B5
C1
10.38; 1658
9.94; 1660
11.40; 1685
8.56; 1688
8.68; 1670
10.37; 1609
A2
A6
10.39; 1658
10.96; 1611
A3
A7
10.41; 1662
10.18; 1660
A4
A8
9.88; 1664
9.77; 1642
B2
B6
C2
9.32; 1690
7.82; 1682
10.44; 1603
B3
B7
C3
10.43; 1701
10.80; 1685
11.62; 1615
B4
C4
10.00; 1685
11.70; 1617
are identical as in (A7, B4, C3), (A8, B5, C4) and (A9, B7) malonate (6; 1.2 mmol) were successively added to the cata-
reveals the order δ(B) Ͻ δ(A) Ͻ δ(C), which is an indication lytic material (0.03 mmol based on ruthenium) dissolved in
of the influence of the core structure of the properties of acetonitrile (6 mL), and the resulting mixture was stirred
these salts. The position of the three methoxy groups on the for 16 h at room temperature [Equation (1)].
phenyl rings also have a strong influence on the acidity of
the proton, as a chemical shift of 7.82 ppm is observed in
the case of the 2,4,6-substitution in B6, whereas the 3,4,5-
substitution pattern in B3 leads to 10.43 ppm.
There is also a noticeable influence of the aromatic sub-
stituents on the infrared C–N vibration, as the observed
wavelengths vary from 1611 to 1701 cm–1. The lowest fre-
(1)
quencies located in the narrow range (1609–1617 cm–1)
correspond to the benzimidazolium salts, which is an indi-
After concentration under vacuum and flash chromatog-
cation of the strong influence of the benzimidazole struc-
raphy over silica gel, the crude product was analyzed by 1H
ture (due to higher electron delocalization) relative to the
NMR spectroscopy, which provided both the conversion
aromatic substituents at the periphery of the molecule. In
and the branched-to-linear ratio (7B/7L). The results are
gathered in Table 2. A blank experiment carried out with-
out the ruthenium source led to no conversion of the start-
ing substrates. Similarly, the reaction performed with
[RuCp*(MeCN)3]PF6 gave no products without prior de-
protonation of malonate. These observations provide clear
contrast, salts A and B exhibit vibration frequencies centred
around 1670–1680 cm–1; a more pronounced influence of
the substituents and a slight tendency to higher frequencies
for six-membered rings B can be seen from comparison of
(A6, B2), (A7, B4), (A8, B5) and (A9, B7).
evidence of the crucial role of the carbene ligands in these
new catalytic systems. All the catalytic systems resulting
from coordination of imidazolinylidene, tetrahydropyrimid-
Generation of Ruthenium Catalysts
inylidene and benzimidazolylidene ligands show good re-
gioselectivity in favour of branched isomer 7B. However,
The characterization of complexes arising from coordi-
nation of the carbenes resulting from deprotonation of salts
A, B and C to a [RuCp*] centre could not be achieved.
Thus, the carbene was generated first by treatment of the
azolium salt with a stoichiometric amount of tBuOK in
THF at 50 °C for 2 h.[24] [RuCp*(MeCN)3]PF6 (I)
(0.5 equiv. with respect to the carbene), which contains la-
bile acetonitrile able to exchange with more coordinating
ligands such as phosphane or bipyridine, was then added
to the solution, and the mixture was heated at 50 °C for
2 h. After removal of the solvent, an air-sensitive solid was
collected. Even if we were not able to fully characterize an
organometallic complex, it is assumed on the basis of pre-
vious work[25] that coordination of one carbene moiety is
involved in the formation of [RuCp*(carbene)] species. This
Table 2. Ruthenium-catalyzed allylic alkylation of cinnamyl car-
bonate 5.[a]
Entry
NHC precursor
Conversion [%]
7B/7L ratio
1
2
3
4
5
6
7
8
9
10
A1
A2
A3
A4
A5
A6
A7
A8
A9
B1
B2
B4
B5
B6
B7
C1
C2
C3
C4
13
10
36
89:11
90:10
93:7
51
94:6
18
74:16
66:34
87:13
82:18
97:3
84:16
88:12
89:11
82:18
81:19
81:19
89:11
91:9
14[b]
17
17[b]
72
26
solid was directly used in catalytic nucleophilic substitution 11
26[b]
10
12
reactions from allylic substrates.
13
14
15
12
94
8
19
60
11
10
Allylic Alkylation of Cinnamyl Carbonate in the Presence
of Ruthenium Catalysts
16
17
18
19
90:10
86:14
The substitution starting from carbonate 5 and carbo-
nucleophile precursor 6 was investigated in the presence of
the previously generated catalytic systems. In a typical ex-
[a] Conditions: dimethyl malonate (6; 1.2 mmol), allylic carbonate
(5; 1 mmol), (A–C)-based catalyst (0.03 mmol based on ruthenium)
periment, cinnamyl carbonate (5; 1 mmol) and dimethyl in MeCN (6 mL) at r.t. for 16 h. [b] 50 °C for 16 h.
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© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Ruthenium-Catalyzed Allylic Substitution Reactions
these catalytic systems have limited application due to their Table 3. Ruthenium-catalyzed allylic etherification of cinnamyl
chloride by phenolate.[a]
relatively low activities. The most efficient systems combin-
ing a good compromise in terms of reactivity and regio-
selectivity appear to be the catalysts resulting from A9 and
B6. It is worth mentioning that relative to C1–4, benzimid-
azolium salts C5–8 containing 2-methoxyethyl, 2-diethyl-
aminoethyl or homobenzyl N-substituents (Figure 5) led to
more reactive catalytic systems, which provides complete
conversion of the substrates within 16 h, but with slightly
lower regioselectivity (B/L ratios in the range 71–88:29–12
as compared to Entries 16–19 in Table 2).[20]
Entry
NHC precursor
Conversion [%]
10B/10L ratio
1
2
3
4
5
6
7
8
A1
A2
A2
A3
A4
A5
A7
A7
A8
A9
A9
B3
B4
B4
B5
B5
B5
B6
C1
C2
C3
100
100
100[c]
100
100
100
90
9:91
–:100
–:100
–:100
–:100
–:100
92:8
–:100
–:100
67:33
9:91
56:44
86:14
83:17
76:24
87:13
32:68
2:98
22:78
41:59
5:95
100[c]
37
9
10
11
12
13
14
15
16
17
18
19
20
21
50[b]
90
20
95
100[c]
9[b]
95
100[c]
32
Figure 5. Benzimidazolium salts with alkyl and homobenzyl N-sub-
stituents.
50
60
10
[a] Conditions: phenol 9 (1.2 mmol), K2CO3 (1.2 mmol), cinnamyl
chloride (8; 1 mmol), (A–C)-based catalyst (0.03 mmol based on
ruthenium) in MeCN (6 mL) at r.t. for 16 h. [b] Dichloromethane
as solvent. [c] THF as solvent.
Allylic Etherification of Cinnamyl Chloride in the Presence
of Ruthenium Catalysts
We previously reported that [RuCp*(MeCN)3]PF6 (I) as
a catalyst led to outstanding regioselectivity in the substitu-
tion of allylic chlorides by phenoxides. To evaluate the in-
fluence of our new catalytic systems based on ruthenium
carbene active species, we studied the reaction of cinnamyl
chloride with phenol in the presence of a base [Equation
(2)].
of the branched product observed with benzimidazolium
salts C5–8 (Figure 5) under similar conditions.[20]
With these carbene-containing catalysts, the solvent also
showed a drastic influence on both activity and regioselec-
tivity. For instance, with ligand A7, similar conversions
were observed but regioselectivities were reversed in aceto-
nitrile and tetrahydrofuran (10B/10L, 92:8 and 0:100,
respectively; Table 3, Entries 7, 8). It is worth noting that
in the presence of catalyst I without any other ligand, a
regioselectivity of 50:1 was obtained in acetonitrile.[12] This
selectivity in favour of the branched isomer is much higher
than the results presented in Table 3 and reveals the strong
influence of the carbene ligands in this catalytic reaction.
The ligands themselves show a general tendency to lower
the regioselectivity in favour of the branched product but
can also lead to the linear ether with perfect regioselectivity.
(2)
Thus, phenol
9 (1.2 mmol), cinnamyl chloride (8;
1 mmol), potassium carbonate (1.2 mmol), ruthenium
catalyst (0.03 mmol) and K2CO3 (1.2 mmol) were stirred in
acetonitrile at room temperature for 16 h. The results are
collected in Table 3. In this reaction, the blank experiment
carried out without ruthenium catalyst during the same re-
action time led to a very low yield of linear ether 10L, exclu-
sively. In acetonitrile, all imidazolidinium salts A led to
Allylic Etherification of 3-Chloro-4-phenylbut-1-ene in the
Presence of Ruthenium Catalysts
We already experienced that the formation of branched
complete conversion with preferred formation of the linear isomers from aliphatic allylic substrates was more challeng-
cinnamyl phenyl ether, except A7, which gave a 10B/10L ing than starting from cinnamyl derivatives. The best of
ratio of 92:8.
our ruthenium catalysts to perform the regioselective
With tetrahydropyrimidinium salts B3 and B6, the con- substitution of 3-chloro-4-phenylbut-1-ene (11) by phenol
versions were modest, but with B4 and B5 they were good [Equation (3)] is the phosphane-containing catalyst
and satisfactory regioselectivities in favour of the branched [RuCp*(MeCN)2(MeOPPh2)]PF6, which leads to
a
isomer were observed (10B/10L, 86:14, 87:13; Table 3, En- branched/linear ratio of 92/8. However, catalytic ruthenium
tries 13, 16). Benzimidazolium salts C1–3 produced cata- systems generated from benzimidazolium salts C5–8 pro-
lytic systems with lower activities and formation of the lin- duced 12B/12L ratios up to 85:15, whereas ruthenium pre-
ear ethers as major products. These results are in contrast cursor I led to only a 60:40 ratio. From the new salts where
to the complete conversion and the regioselective formation the N-atoms are substituted by benzylic groups, the reac-
Eur. J. Org. Chem. 2008, 2142–2149
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2145

S. Yasar, I. Özdemir, B. Cetinkaya, J.-L. Renaud, C. Bruneau
FULL PAPER
tions were not complete within 16 h at room temperature benzimidazolium salts that are N-substituted by an alkyl
and some reactions required heating to 50 °C (Table 4, En- chain featuring a coordinating heteroatom (C5–7) or a
tries 5–8, 10, 12, 13) to give satisfactory conversion, which homobenzylic group (C7 and C8).
reveals a decrease in activity relative to N-heterocyclic salts
C5–8 with aliphatic N-substituents. In all cases, except from
A8 (Table 4, Entry 7), branched compound 12B is formed
as the major isomer, but the regioselectivities are modest
(54:46 to 79/21). In this allylic substitution example, there
is no important influence of the nature of the benzylic car-
Experimental Section
General Preparation of Nonsymmetrical N-Heterocyclic Salts
(A1–5)
N-(2,4,6-Trimethylbenzyl)ethylenediamine: Li (0.34 g, 48.02 mmol)
was added to H2NCH2CH2NH2 (1.2 mol, 80 mL), and the mixture
was heated on a sand bath (ca. 110 °C) for 1 h. After gas evolution,
2,4,6-trimethylbenzyl chloride (8.0 g, 47.42 mmol) was slowly
added at room temperature. Toluene (50 mL) was then added, and
the resulting mixture was heated at 110 °C for 2 h. After cooling,
(3) the mixture was filtered and the volatiles were removed under vac-
uum. The residue was distilled to give a colourless liquid (b.p. 98–
100 °C/0.01 Torr). Yield: 7.63 g (83%).
bene precursors A, B or C on the fate of the reaction.
1-(2,4,6-Trimethylbenzyl)imidazoline: A mixture of N-(2,4,6-tri-
methylbenzyl) ethylenediamine (7.63 g, 39.74 mmol) and N,N-di-
methylformamide dimethylacetal (5.8 mL, 43.07 mmol) was heated
on a steam bath (90–95 °C) for 2 h to remove MeOH and HNMe2.
The residue was then heated to 120 °C for 1 h. The volatiles were
removed under vacuum, and the remaining yellow viscous liquid
was distilled under vacuum (108–109 °C/0.01 Torr) to give a
colourless liquid, which solidified on standing, and was then crys-
tallized from hexane (10 mL). White hygroscopic crystals were col-
lected and dried. Yield: 7.39 g (93%).
Table 4. Ruthenium-catalyzed allylic etherification of 11 by aryl-
oxide anions.[a]
Entry
NHC precursor
Conversion [%]
12B/12L ratio
1
2
3
4
5
6
7
8
A1
A2
A3
A5
A6
A7
A8
A9
B1
B2
B3
B4
B5
B6
B7
C1
C3
C4
93
80
90
66:34
60:40
70:30
73:27
70:30
63:37
36:64
79:21
60:40
54:46
65:35
68:32
72:28
58:42
60:40
74:26
69:31
60:40
87
91[b]
93
79[b]
88
Preparation of A1 as a Typical Procedure: To a solution of 1-(2,4,6-
trimethylbenzyl)imidazoline (2.02 g, 10 mmol) in DMF (5 mL) was
slowly added 2-methylbenzyl chloride (1.41 g, 10.1 mmol) at 25 °C,
and the resulting mixture was stirred at room temperature for 8 h.
Diethyl ether (15 mL) was added to obtain a white crystalline solid,
which was filtered off. The solid was washed with diethyl ether
(3ϫ10 mL) and dried under vacuum, and the crude product was
recrystallized from ethanol/diethyl ether (2:1).
9
60
10
11
12
13
14
15
16
17
18
86[b]
88
93[b]
90[b]
7
80
70
65
80
1-(2,4,6-Trimethylbenzyl)-3-(2-methylbenzyl)imidazolinium Chloride
(A1): Yield: 3.08 g (90%). M.p. 241–242 °C. IR: IR: ν = 1658
˜
ν(CN) cm–1. 1H NMR (400 MHz, CDCl3): δ = 2.09 [s, 3 H,
CH2C6H2(CH3)3-4], 2.18 [s, 6 H, CH2C6H2(CH3)3-2,6], 2.39 [s, 3
H, CH2C6H4(CH3)-2], 3.63 and 3.6 9 (m, 4 H, NCH2CH2N), 4.80
[s, 2 H, CH2C6H2(CH3)3-2,4,6], 4.84 [s, 2 H, CH2C6H4(CH3)-2],
[a] Conditions: phenol 9 (1.2 mmol), K2CO3 (1.2 mmol), allylic
chloride 11 (1 mmol), (A–C)-based catalyst (0.03 mmol based on
ruthenium) in MeCN (6 mL) at r.t. for 16 h. [b] 50 °C for 16 h.
6.68 [s,
2 H, CH2C6H2(CH3)3-2,4,6], 7.01–7.24 [m, 4 H,
CH2C6H4(CH3)-3], 10.38 (s, 1 H, NCHN) ppm. 13C{H}NMR
(100 MHz, CDCl3): δ = 19.52 [CH2C6H4(CH3)-2], 20.3 [CH2C6H2-
(CH3)3-2,6], 21.1 [CH2C6H2(CH3)3-6], 46.2 [CH2C6H2(CH3)3-
2,4,6], 47.6 and 47.9 (NCH2CH2N), 50.0 [CH2C6H4(CH3)-6],
129.9, 131.2, 137.1 and 138.0 [CH2C6H2(CH3)3-2,4,6], 125.8, 126.7,
129.0, 129.9, 131.1 and 138.6 [CH2C6H4(CH3)-2], 158.9 (NCHN)
ppm. C21H27ClN2 (342.91): calcd. C 73.56, H 7.94, N 8.17; found
C 73.57, H 7.93, N 8.16.
Conclusions
New imidazolidinium, 3,4,5,6-tetrahydropyrimidinium
and benzimidazolium salts, precursors of N-heterocyclic
carbenes upon deprotonation, were prepared. They were as-
sociated to [RuCp*(MeCN)3]PF6 to generate new catalytic
species, which are active in the nucleophilic substitution of
allylic carbonates and chlorides by malonate and phenol.
The observed regioselectivities differ from those obtained
with [RuCp*(MeCN)3]PF6, which reveals that the active
catalytic species are different. However, the regioselectivities
strongly depend on the type of substrates and carbene pre-
cursors, without any obvious rule, and even perfect selectiv-
ity in favour of the undesired linear product is sometimes
obtained. It is worth noting that the activities and regio-
selectivities in favour of the branched isomers obtained with
1-(2,4,6-Trimethylbenzyl)-3-(3-methylbenzyl)imidazolinium Chloride
(A2): Yield: 3.02 g (88%). M.p. 246–247 °C. IR: ν = 1658 ν(CN)
˜
cm–1. 1H NMR (400 MHz, CDCl3):
δ = 2.19 [s, 3 H,
CH2C6H4(CH3)-4], 2.22 [s, 6 H, CH2C6H2(CH3)3-2,6], 2.27 [s, 3 H,
CH2C6H2(CH3)3-2,6], 3.57 and 3.74 (m, 4 H, NCH2CH2N), 4.78
[s, 2 H, CH2C6H2(CH3)3-2,4,6], 4.84 [s, 2 H, CH2C6H4(CH3)-4],
6.78 [s,
2 H, CH2C6H2(CH3)3-2,4,6], 7.05–7.26 [m, 4 H,
CH2C6H4(CH3)-4], 10.39 (s, 1 H, NCHN) ppm. 13C{H}NMR
(100 MHz, CDCl3): δ = 21.1 [CH2C6H4(CH3)-4], 20.3 [CH2C6H2-
these new benzylic salts are lower than those obtained with (CH3)3-2,6], 21.5 [CH2C6H2(CH3)3-6], 46.4 [CH2C6H2(CH3)3-
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Ruthenium-Catalyzed Allylic Substitution Reactions
2,4,6], 47.6 and 47.7 (NCH2CH2N), 52.3 [CH2C6H4(CH3)-4], colourless solid precipitated, which was collected by filtration and
125.9, 132.8, 138.0 and 139.2 [CH2C6H2(CH3)3-2,4,6], 125.5, 129.3,
dried under vacuum. Crude product A, B or C was recrystallized
129.9, and 139.3 [CH2C6H4(CH3)-4], 158.8 (NCHN) ppm. from absolute ethanol to give colourless needles, and the solid was
C21H27ClN2 (342.91): calcd. C 73.56, H 7.94, N 8.17; found C washed with diethyl ether (2ϫ10 mL) and dried under vacuum.
73.52, H 7.95, N 8.14.
1,3-Bis(4-benzyloxybenzyl)imidazolinium Chloride (A6): Yield:
4.49 g (90%). M.p. 224–225 °C. IR: ν = 1611 ν(CN) cm–1. 1H NMR
˜
1-(2,4,6-Trimethylbenzyl)-3-(4-methylbenzyl)imidazolinium Chloride
(A3): Yield: 2.91 g (85%). M.p. 279–280 °C. IR: ν = 1662 ν(CN)
(200 MHz, CDCl3): δ = 3.62 (s, 4 H, NCH2CH2N), 4.65 [s, 4 H,
CH2C6H4(OCH2)C6H5], 5.02 [s, 4 H, CH2C6H4(OCH2)C6H5],
7.34–6.75 [m, 18 H CH2C6H4(OCH2)C6H5], 10.96 (s, 1 H, NCHN)
ppm. 13C{H}NMR (50 MHz, CDCl3): δ = 47.6 (NCH2CH2N),
56.7 [CH2C6H4(OCH2)C6H5], 71.2 [CH2C6H4(OCH2)C6H5], 112.9,
114.2, 121.6, 125.6, 127.4, 128.1; 128.7; 136.9; 148.9; 150.5
[CH2C6H4(OCH2)C6H5], 159.4 (NCHN) ppm. C31H31ClN2O2
(499.05): calcd. C 74.61, H 6.26, N 5.61; found C 74.65, H 6.29, N
5.60.
˜
cm–1. 1H NMR (400 MHz, CDCl3):
δ = 2.07 [s, 3 H,
CH2C6H4(CH3)-4], 2.16 [s, 6 H, CH2C6H2(CH3)3-2,6], 2.19 [s, 6 H,
CH2C6H2(CH3)3-2,6], 3.55 and 3.71 (m, 4 H, NCH2CH2N), 4.73
[s, 2 H, CH2C6H2(CH3)3-2,4,6], 4.74 [s, 2 H, CH2C6H4(CH3)-4],
6.78 [s,
2 H, CH2C6H2(CH3)3-2,4,6], 6.94–7.17 [m, 4 H,
CH2C6H4(CH3)-4], 10.41 (s, 1 H, NCHN) ppm. 13C{H}NMR
(100 MHz, CDCl3): δ = 21.0 [CH2C6H4(CH3)-2], 20.3 [CH2C6H2-
(CH3)3-2,6], 21.3 [CH2C6H2(CH3)3-6], 46.2 [CH2C6H2(CH3)3-
2,4,6], 47.5 and 47.6 (NCH2CH2N), 51.7 [CH2C6H4(CH3)-6],
128.8, 130.3, 137.9 and 138.5 [CH2C6H2(CH3)3-2,4,6], 125.8, 129.8,
139.6 [CH2C6H4(CH3)-2], 158.7 (NCHN) ppm. C21H27ClN2
(342.91): calcd. C 73.56, H 7.94, N 8.17; found C 73.51, H 7.97, N
8.21.
1,3-Bis(2,3,4-trimethoxybenzyl)imidazolinium Chloride (A7): Yield:
4.44 g (95%). M.p. 193–194 °C. IR: ν = 1660 ν(CN) cm–1. 1H NMR
˜
(200 MHz, CDCl3): δ = 3.72 [s, 6 H, CH2C6H2(OCH3)3-2], 3.85 [s,
6 H, CH2C6H2(OCH3)3-3], 3.96 [s, 6 H, CH2C6H2(OCH3)3-4], 4.77
[s, 4 H, CH2C6H2(OCH3)3], 3.86 (s, 4 H, NCH2CH2N), 6.63; 6.68;
7.17 and 7.21 [m, 4 H, CH2C6H2(OCH3)3], 10.18 (s, 1 H, NCHN)
ppm. 13C{H}NMR (50 MHz, CDCl3): δ = 48. 10 (NCH2CH2N),
56.5 [CH2C6H2(OCH3)3-2], 61.24 [CH2C6H2(OCH3)3-3], 61.79
[CH2C6H2(OCH3)3-4], 47.71 [CH2C6H2(OCH3)3], 107.71; 118.8;
126.09; 142.20; 152.56 and 155.24 [CH2C6H2(OCH3)3], 159.21
(NCHN) ppm. C23H31ClN2O6 (466.96): calcd. C 59.16, H 6.69, N
6.00; found C 59.15, H 6.72, N 6.02.
1-(2,4,6-Trimethylbenzyl)-3-(4-tert-butylbenzyl)imidazolinium Bro-
mide (A4): Yield: 3.74 g (87%). M.p. 290–291 °C. IR: ν = 1664
˜
ν(CN) cm–1. 1H NMR (400 MHz, CDCl3): δ = 1.22 {s, 9 H,
CH2C6H4[C(CH3)3]-4}, 2.18 [s, 6 H, CH2C6H2(CH3)3-4], 2.30 [s, 6
H, CH2C6H2(CH3)3-2,6], 3.66 and 3.82 (m, 4 H, NCH2CH2N),
4.78 [s, 2 H, CH2C6H2(CH3)3-2,4,6], 4.84 {s, 2 H, CH2C6H4-
[C(CH3)3-4]}, 6.79 [s, 2 H, CH2C6H2(CH3)3-2,4,6], 7.25–7.32 {m, 4
H, CH2C6H4[C(CH3)3-4]}, 9.88 (s,
1
H, NCHN) ppm. 1,3-Bis(2,4,5-trimethoxybenzyl)imidazolinium Chloride (A8): Yield:
13C{H}NMR (100 MHz, CDCl3): δ = 20.4 [CH2C6H2(CH3)3-2,6], 4.20 g (90%). M.p. 169–170 °C. IR: ν = 1642 ν(CN) cm–1. 1H NMR
˜
21.1 [CH2C6H2(CH3)3-6], 31.4 {CH2C6H4[C(CH3)3-3,5]}, 34.8
{CH2C6H4[C(CH3)3-3,5]}, 46.5 [CH2C6H2(CH3)3-2,4,6], 47.9 and
(200 MHz, CDCl3): δ = 3.70 [s, 6 H, CH2C6H2(OCH3)3-2], 3.74 [s,
6 H, CH2C6H2(OCH3)3-5], 3.77 [s, 6 H, CH2C6H2(OCH3)3-4], 4.68
48.0 (NCH2CH2N), 52.0 [CH2C6H4(CH3)2-3,5], 126.3, 129.8, [s, 4 H, CH2C6H2(OCH3)3], 3.81 (s, 2 H, NCH2CH2N), 3.82 (s, 2
138.1, and 139.2 [CH2C6H2(CH3)3-2,4,6], 125.5, 128.8, 130.1, and
152.3 {CH2C6H4[C(CH3)3-4]}, 157.8 (NCHN) ppm. C24H33BrN2
(429.44): calcd. C 67.12, H 7.75, N 6.52; found C 67.19, H 7.77, N
6.51.
H, NCH2CH2N), 6.45 and 7.11 [m, 4 H, CH2C6H2(OCH3)3], 9.77
(s, 1 H, NCHN) ppm. 13C{H}NMR (50 MHz, CDCl3): δ = 47.2
(NCH2CH2N), 56.6 [CH2C6H2(OCH3)3-2], 56.7 [CH2C6H2-
(OCH3)3-5], 57.4 [CH2C6H2(OCH3)3-4], 48.1 [CH2C6H2(OCH3)3],
97.41; 112.5; 115.4; 143.7; 150.9 and 152.6 [CH2C6H2(OCH3)3],
159.1 (NCHN) ppm. C23H31ClN2O6 (466.96): calcd. C 59.16, H
6.69, N 6.00; found C 59.12, H 6.73, N 5.98.
1-(2,4,6-Trimethylbenzyl)-3-(3,5-dimethylbenzyl)imidazolinium Bro-
mide (A5): Yield: 3.65 g (91%). M.p. 285–286 °C. IR: ν = 1660
˜
ν(CN) cm–1. 1H NMR (400 MHz, CDCl3): δ = 2.18 [s, 6 H,
CH2C6H2(CH3)3-4], 2.22 [s, 6 H, CH2C6H2(CH3)3-2,6], 2.29 [s, 6 H,
CH2C6H4(CH3)2-3,5], 3.65 and 3.79 (m, 4 H, NCH2CH2N), 4.71 [s,
2 H, CH2C6H2(CH3)3-2,4,6], 4.84 [s, 2 H, CH2C6H3(CH3)2-3,5],
6.79 [s, 2 H, CH2C6H2(CH3)3-2,4,6], 6.89 [s, 3 H, CH2C6H3-
(CH3)2-3,5], 9.94 (s, 1 H, NCHN) ppm. 13C{H}NMR (100 MHz,
CDCl3): δ = 20.4 [CH2C6H2(CH3)3-2,6], 21.1 [CH2C6H2(CH3)3-6],
21.4 [CH2C6H3(CH3)2-3,5], 46.5 [CH2C6H2(CH3)3-2,4,6], 47.9 and
48.0 (NCH2CH2N), 52.4 [CH2C6H4(CH3)2-3,5], 126.6, 130.8, 132.6
and 139.1 [CH2C6H2(CH3)3-2,4,6], 125.5, 130.0, 138.1 and 139.2
[CH2C6H4(CH3)2-3,5], 157.9 (NCHN) ppm. C22H29BrN2 (401.39):
calcd. C 65.83, H 7.28, N 6.98; found C 65.90, H 7.22, N 6.99.
For 1,3-Bis(9-anthracenomethyl)imidazolidinium Chloride (A9):
Yield: 3.90 g (80%). M.p. 224–225 °C. IR: ν = 1685 ν(CN) cm–1.
˜
1H NMR (200 MHz, DMSO): δ = 3.60 (s, 4 H, NCH2CH2N), 5.80
(s, 4 H, CH2C14H14), 7.20–8.10 (m, 28 H, CH2C9H14), 11.4 (s, 1 H,
NCHN) ppm. 13C{H}NMR (50 MHz, DMSO):
δ = 47.5
(NCH2CH2N), 50.4 (NCH2CH2CH2N), 56.4 (CH2C9H14), 123.1,
125.8, 126.4, 127.8, 128.4, 128.9, 129.6, 130.2, 130.7, 131.3, 134.0
(CH2C14H14), 157.2 (NCHN) ppm. C33H27ClN2 (487.04): calcd. C
81.38, H 5.59, N 5.75; found C 81.39, H 5.62, N 5.72.
1,3-Bis(2,4,6-trimethylbenzyl)-3,4,5,6-tetrahydropyrimidinium Chlo-
ride (B1)[26]: Yield: 3.77 g (98%). M.p. 288–289 °C. IR: ν = 1688
˜
ν(CN) cm–1. 1H NMR (300 MHz, CDCl3): δ = 8.56 (s, 1 H,
NCHN), 6.73 [s, 4 H, CH2C6H2(CH3)3-2,4,6], 4.74 [s, 4 H,
CH2C6H2(CH3)3-2,4,6], 3.36 (t, J = 5.7 Hz, 4 H, NCH2CH2CH2N),
2.16 and 2.20 [s, 18 H, CH2C6H2(CH3)3-2,4,6], 2.01 (quint., J =
5.3 Hz, 2 H, NCH2CH2CH2N) ppm. 13C NMR (75.5 MHz,
CDCl3): δ = 151.9 (NCHN), 125.3, 130.0, 137.9 and 138.9
[CH2C6H2(CH3)3-2,4,6], 52.1 [CH2C6H2(CH3)3-2,4,6], 42.6
(NCH2CH2CH2N), 19.8 and 20.9 [CH2C6H2(CH3)3-2,4,6], 19.1
(NCH2CH2CH2N) ppm. C24H33ClN2 (384.99): calcd. C 74.87, H
8.64, N 7.27; found C 74.83, H 8.66, N 7.30.
General Preparation of Symmetrical N-Heterocyclic Salts A6–9,
B1–7 and C1–4: Aromatic aldehyde 2 (20 mmol) and diamine 1
(10 mmol) were stirred overnight in methanol. The diimine was col-
lected as a white solid, filtered and recrystallized from an alcohol/
ether mixture. Diimine 3 (10 mmol) was subsequently reduced by
NaBH4 (30 mmol) in CH3OH (30 mL). The solution was then
treated with 1  HCl, and the organic phase was extracted with
CH2Cl2 (3ϫ30 mL). After drying over MgSO4 and evaporation,
diamine 4 was isolated as a solid. Diamine 4 was then treated with
a large excess of triethylorthoformate (50 mL) in the presence of
NH4Cl (10 mmol) at 110 °C in a distillation apparatus until re-
moval of ethanol ceased. Upon cooling to room temperature, a
1,3-Bis(4-benzyloxybenzyl)-3,4,5,6-tetrahydropyrimidinium Chloride
(B2): Yield: 4.36 g (85%). M.p. 238–239 °C. IR: ν = 1690 ν(CN)
˜
Eur. J. Org. Chem. 2008, 2142–2149
© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
2147

S. Yasar, I. Özdemir, B. Cetinkaya, J.-L. Renaud, C. Bruneau
19.4 (NCH2CH2CH2N) ppm. C24H33ClN2O6 (480.99): calcd. C
FULL PAPER
cm–1. 1H NMR (200 MHz, CDCl3):
δ = 4.64 [s, 4 H,
CH2C6H4(OCH2)C6H5], 5.13 [s, 4 H, CH2C6H4(OCH2)C6H5], 3.17 59.93, H 6.91, N 5.82; found C 59.89, H 6.94, N 5.80.
(t, J = 4.6 Hz, 4 H, NCH2CH2CH2N), 1.96 (quint., J = 4.2 Hz, 2
1,3-Bis(9-anthracenomethyl)-3,4,5,6-tetrahydropyrimidinium Chlo-
H, NCH2CH2CH2N), 7.06, 7.32, 7.34, 7.38, 7.40, 7.41, 7.44 and
ride (B7): Yield: 4.26 g (85%). M.p. 198–199 °C. IR: ν = 1685
˜
7.46 [m, 18 H, CH2C6H4(OCH2)C6H5], 9.32 (s, 1 H, NCHN) ppm.
ν(CN) cm–1. 1H NMR (200 MHz, CDCl3): δ = 1.90 (m, 2 H,
NCH2CH2CH2N), 3.2 (t, J = 5.6 Hz, 4 H, NCH2CH2CH2N), 5.5
(s, 4 H, CH2C14H14), 7.3–8.4 (m, 28 H, CH2C9H14), 10.8 (s, 1 H,
13C{H}NMR (50 MHz, CDCl3): δ = 19.2 (NCH2CH2CH2N), 57.7
(NCH2CH2CH2N), 70.13
[CH2C6H4(OCH2)C6H5], 127.27, 128.67, 128.79, 129.35, 130.83,
137.81 [CH2C6H4(OCH2)C6H5], 159.4 (NCHN) ppm.
[CH2C6H4(OCH2)C6H5], 115.93
NCHN) ppm. 13C{H}NMR (50 MHz, CDCl3):
δ = 18.7
(NCH2CH2CH2N), 42.1 (NCH2CH2CH2N), 60.1 (CH2C9H14),
123.2, 125.6, 126.2, 127.5, 128.4, 128.7, 129.3, 130.2, 131.9, 133.9,
140.2 (CH2C14H14), 156.3 (NCHN) ppm. C34H29ClN2 (501.07):
calcd. C 81.50, H 5.83, N 5.59; found C 81.49, H 5.85, N 5.58.
C32H33ClN2O2 (513.08): calcd. C 74.91, H 6.48, N 5.46; found C
74.96, H 6.44, N 5.47.
1,3-Bis(3,4,5-trimethoxybenzyl)-3,4,5,6-tetrahydropyrimidinium
Chloride (B3)[26]: Yield: 4.52 g (94%). M.p. 266–267 °C. IR: ν =
˜
1,3-Bis(4-benzyloxybenzyl)benzimidazolium Chloride (C1): Yield:
1701 ν(CN) cm–1. 1H NMR (300 MHz, CDCl3): δ = 10.43 (s, 1
H, NCHN), 6.72 [s, 4 H, CH2C6H2(OCH3)3-3,4,5], 4.75 [s, 4 H,
CH2C6H2(OCH3)3-3,4,5], 3.76 and 3.81 [s, 18 H, CH2C6H2-
(OCH3)3-3,4,5], 3.21 (t, J = 5.2 Hz, 4 H, NCH2CH2CH2N), 1.93
(quint., J = 5.2 Hz, 2 H, NCH2CH2CH2N) ppm. 13C NMR
(75.5 MHz, CDCl3): δ = 154.7 (NCHN), 106.6, 129.0, 138.7 and
153.9 [CH2C6H2(OCH3)3-3,4,5], 61.0 [CH2C6H2(OCH3)3-3,4,5],
56.8 and 59.0 [CH2C6H2(OCH3)3-3,4,5], 42.0 (NCH2CH2CH2N),
19.3 (NCH2CH2CH2N) ppm. C24H33ClN2O6 (480.99): calcd. C
59.93, H 6.91, N 5.82; found C 59.95, H 6.90, N 5.84.
4.37 g (80%). M.p. 135–136 °C. IR: ν = 1609 ν(CN) cm–1. 1H NMR
˜
(200 MHz, DMSO): δ = 5.11 [s, 4 H, CH2C6H4(OCH2)C6H5], 5.74
[s, 4 H, CH2C6H4(OCH2)C6H5], 8.05–7.046 [m, 22 H, C6H4N2CH
and CH2C6H4(OCH2)C6H5], 10.37 (s,
1 H, NCHN) ppm.
13C{H}NMR (50 MHz, DMSO): δ = 50.38 [CH2C6H4(OCH2)-
C6H5], 70.14 [CH2C6H4(OCH2)C6H5], 143.28, 137.70, 131.86,
131.1, 129.4, 128.78, 128.6, 127.54, 126.96, 116.05, 114.97
C6H4N2CH and [CH2C6H4(OCH2)C6H5], 159.48 (NCHN) ppm.
C35H31ClN2O2 (547.10): calcd. C 76.84, H 5.71, N 5.12; found C
76.83, H 5.75, N 5.10.
1,3-Bis(2,3,4-trimethoxybenzyl)-3,4,5,6-tetrahydropyrimidinium 1,3-Bis(3,4,5-trimethoxybenzyl)benzimidazolium Chloride (C2):
Chloride (B4): Yield: 4.28 g (89%). M.p. 184–185 °C. IR: ν = 1685
Yield: 4.63 g (90%). M.p. 248–249 °C. IR: ν˜ = 1603 ν(CN) cm–1.
1H NMR (200 MHz, [D6]DMSO): δ = 3.75 and 3.61 [s, 18 H,
˜
ν(CN) cm–1 1H NMR (200 MHz, CDCl3): δ = 3.85 [s, 6 H,
.
CH2C6H2(OCH3)3-2], 3.90 [s, 6 H, CH2C6H2(OCH3)3-3], 3.94 [s, 6 CH2C6H2(OCH3)3-3,4,5], 5.66 [s, 4 H, CH2C6H2(OCH3)3-3,4,5],
H, CH2C6H2(OCH3)3-4], 4.81 [s, 4 H, CH2C6H2(OCH3)3], 3.23 (t,
7.00 [s, 4 H, CH2C6H2(OCH3)3-3,4,5], 8.14 and 7.64 [m, 4 H,
J = 5.6 Hz, 4 H, NCH2CH2CH2N), 2.03 (quint., J = 4.8 Hz, 2 H, NC6H4N], 10.44 [s, 1 H, NCHN] ppm. 13C NMR (50 MHz, [D6]-
NCH2CH2CH2N), 6.64; 6.70; 7.22; 7.26 [m, 4 H, CH2C6H2-
DMSO): δ = 56.8 and 50.9 [CH2C6H2(OCH3)3-3,4,5], 60.6
(OCH3)3], 10.00 (s, 1 H, NCHN) ppm. 13C{H}NMR (50 MHz, [CH2C6H2(OCH3)3-3,4,5], 107.3, 131.7, 138.4 and 151.9
CDCl3): δ = 19.5 (NCH2CH2CH2N), 42.4 (NCH2CH2CH2N), [CH2C6H2(OCH3)3-3,4,5], 114.7,127.4, 129.9 and 143.2 [NC6H4N],
56.4 [CH2C6H2(OCH3)3-2], 61.2 [CH2C6H2(OCH3)3-3], 61.9 153.8 [NCHN] ppm. C27H31ClN2O6 (515.01): calcd. C 62.97, H
[CH2C6H2(OCH3)3-4], 54.2 [CH2C6H2(OCH3)3], 107.8, 119.4,
126.2, 142.3, 152.780 and 154.9 [CH2C6H2(OCH3)3], 155.2
(NCHN) ppm. C24H33ClN2O6 (480.99): calcd. C 59.93, H 6.92, N
5.82; found C 59.89, H 6.94, N 5.81.
6.07, N 5.44; found C 63.00, H 6.04, N 5.49.
1,3-Bis(2,3,4-trimethoxybenzyl)benzimidazolium Chloride (C3):
Yield: 4.12 g (80%). M.p. 187–188 °C. IR: ν = 1615 ν(CN) cm–1.
˜
1H NMR (200 MHz, DMSO): δ = 3.76 [s, 6 H, CH2C6H2-
(OCH3)3-2], 3.78 [s, 6 H, CH2C6H2(OCH3)3-3], 3.91 [s, 6 H,
CH2C6H2(OCH3)3-4], 5.72 [s, 4 H, CH2C6H2(OCH3)3], 7.72–6.62
[m, 8 H, C6H4N2CH and CH2C6H2(OCH3)3], 11.62 (s, 1 H,
1,3-Bis(2,4,5-trimethoxybenzyl)-3,4,5,6-tetrahydropyrimidinium
Chloride (B5): Yield: 4.09 g (85%). M.p. 129–130 °C. IR: ν = 1670.3
˜
ν(CN) cm–1 1H NMR (200 MHz, CDCl3): δ = 3.70 [s, 6 H,
.
NCHN) ppm. 13C{H}NMR (50 MHz, DMSO):
[CH2C6H2(OCH3)3-2], 60.98 [CH2C6H2(OCH3)3-3],
[CH2C6H2(OCH3)3-4], 46.69 [CH2C6H2(OCH3)3], 144.34, 142.02,
131.42, 126.80, 125.717, 118.73, 113.82 C6H4N2CH and
[CH2C6H2(OCH3)3], 155.18 (NCHN) ppm. C27H31ClN2O6
(515.01): calcd. C 62.97, H 6.07, N 5.44; found C 62.92, H 6.09, N
5.41.
δ
=
56.19
61.69
CH2C6H2(OCH3)3-2], 3.77 [s, 6 H, CH2C6H2(OCH3)3-5], 3.79 [s, 6
H, CH2C6H2(OCH3)3-4], 4.54 [s, 4 H, CH2C6H2(OCH3)3], 3.18 (t,
J = 4.2 Hz, 4 H, NCH2CH2CH2N), 1.80 (quint., J = 4.4 Hz, 2 H,
NCH2CH2CH2N), 6.73 and 7.01 [m, 4 H, CH2C6H2(OCH3)3], 8.68
(s, 1 H, NCHN) ppm. 13C{H}NMR (50 MHz, CDCl3): δ = 19.2
( N C H 2 C H 2 C H 2 N ) , 4 2 . 7 ( N C H 2 C H 2 C H 2 N ) , 5 6 . 6
[CH2 C6 H2 (OCH3 )3 -2], 57.0 [CH2C6H2(OCH3 )3 -3], 57.2
[CH2C6H2(OCH3)3-4], 53.45 [CH2C6H2(OCH3)3],99.02; 113.3;
116.1; 143.3; 151.0 and 153.1 [CH2C6H2(OCH3)3], 153.6 (NCHN)
ppm. C24H33ClN2O6 (480.99): calcd. C 59.93, H 6.92, N 5.82;
found C 59.92, H 6.95, N 5.83.
1,3-Bis(2,4,5-trimethoxybenzyl)benzimidazolium Chloride (C4):
4.48 g (87%). M.p. 166–167 °C. IR: ν = 1617 ν(CN) cm–1. 1H NMR
˜
(200 MHz, CDCl3): δ = 3.75 [s, 6 H, CH2C6H2(OCH3)3-2], 3.79 [s,
6 H, CH2C6H2(OCH3)3-5], 3.83 [s, 6 H, CH2C6H2(OCH3)3-4], 4.73
[s, 4 H, CH2C6H2(OCH3)3], 7.82–6.85 [m, 8 H, C6H4N2CH and
CH2C6H2(OCH3)3], 11.70 (s, 1 H, NCHN) ppm. 13C{H}NMR
(50 MHz, CDCl3): δ = 57.2 [CH2C6H2(OCH3)3-2], 57.8 [CH2C6H2-
(OCH3)3-5], 58.2 [CH2C6H2(OCH3)3-4], 48.1 [CH2C6H2(OCH3)3],
145.6, 143.08, 132.48, 127.2, 126.9, 119.3, 114.5 C6H4N2CH and
[CH2C6H2(OCH3)3], 158.42 (NCHN) ppm. C27H31ClN2O6
(515.01): calcd. C 62.97, H 6.07, N 5.44; found C 62.93, H 6.08, N
5.42.
1,3-Bis(2,4,6-trimethoxybenzyl)-3,4,5,6-tetrahydropyrimidinium
Chloride (B6)[26]: Yield: 4.28 g (89%). M.p. 233–234 °C. IR: ν =
˜
1
1682 ν(CN) cm–1. H NMR (300 MHz, CDCl3): δ = 7.82 (s, 1 H,
NCHN), 6.03 [s, 4 H, CH2C6H2(OCH3)3-2,4,6], 4.46 [s, 4 H,
CH2C6H2(OCH3)3-2,4,6], 3.69 and 3.75 [s, 18 H, CH2C6H2-
(OCH3)3-2,4,6], 3.32 (t, J = 5.6 Hz, 4 H, NCH2CH2CH2N), 1.96
(quint., J = 5.2 Hz, 2 H, NCH2CH2CH2N) ppm. 13C NMR
(75.5 MHz, CDCl3): δ = 162.7 (NCHN), 90.8, 101.7, 151.8 and
159.9 [CH2C6H2(OCH3)3-2,4,6], 58.1 [CH2C6H2(OCH3)3-2,4,6], Representative Procedure for Etherification of Cinnamyl Chloride by
55.7 and 56.1 [CH2C6H2(OCH3)3-2,4,6], 43.3 (NCH2CH2CH2N), Phenol: To a degassed THF (5 mL) suspension of imidazolium salt
2148
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Eur. J. Org. Chem. 2008, 2142–2149

Ruthenium-Catalyzed Allylic Substitution Reactions
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(0.030 mmol, 6 mol-%) was added tBuOK (3.4 mg, 0.030 mmol,
6 mol-%), and the mixture was heated at 50 °C for 2 h and then
cooled to room temperature. [Cp*Ru(CH3CN)3][PF6] (7.6 mg,
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was successively added acetonitrile (3 mL), cinnamyl chloride 15
(166 mg, 1 mmol, 1 equiv.), potassium carbonate (166 mg,
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Received: January 2, 2008
Published Online: February 27, 2008
Eur. J. Org. Chem. 2008, 2142–2149
© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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