N′-activation of N-arylimidazoles: Facile syntheses of N-alkyl-N′-arylimidazolium iodides from less expensive chloro substrates

Article abstract of DOI:10.1055/s-0028-1088053

A series of N,N′-asymmetrically substituted imidazolium iodide salts have been synthesized, starting from N-arylimidazoles and the less expensive, but less reactive, 1-chlorobutane or (3-chloropropyl)trimethoxysilane. The addition of potassium iodide and

Full text of DOI:10.1055/s-0028-1088053

PAPER
1647
N¢-Activation of N-Arylimidazoles: Facile Syntheses of N-Alkyl-N¢-aryl-
imidazolium Iodides from Less Expensive Chloro Substrates
N¢-Activation of
N
n
-Arylimidazo
n
le
s
a Magdalena Oertel, Vincent Ritleng, Michael J. Chetcuti*
Laboratoire de Chimie Organométallique Appliquée, UMR CNRS 7509, Université de Strasbourg, Ecole Européenne de Chimie,
Polymères et Matériaux, 25 rue Becquerel, 67087 Strasbourg, France
Fax +33(3)90242639; E-mail: chetcuti@chimie.u-strasbg.fr
Received 4 December 2008
Known synthetic procedures for N-alkyl-N¢-arylimidazo-
lium salts often require the use of alkyl iodides3b,11 or
bromides12 when starting from the less reactive arylimid-
azoles. The chlorides are often inert or require forcing
Abstract: A series of N,N¢-asymmetrically substituted imidazoli-
um iodide salts have been synthesized, starting from N-arylimida-
zoles and the less expensive, but less reactive, 1-chlorobutane or (3-
chloropropyl)trimethoxysilane. The addition of potassium iodide
and the use of 1,2-dimethoxyethane as a solvent lead to multigram conditions.9,13 We present here a simple new synthetic
quantities of these salts becoming readily available, in yields rang-
ing from 50% to 94%. Direct combination of (3-chloropropyl)tri-
method to prepare not easily accessible N-alkyl-N¢-
arylimidazolium cations from the less reactive alkyl chlo-
methoxysilane with 1-mesityl-1H-imidazole was also effected, in
rides, under moderate conditions.
good yield, by using a microwave oven at 180 °C. The synthesis of
two 1-alkyl-3-isopropylimidazolium chlorides is also presented
herein.
R1
R2
R2Cl, (KI)
R1
+
N
N
N
N
I– or Cl–
DME, ∆
Key words: arylimidazoles, imidazolium salts, trimethoxysilyl,
chloroalkyls, N-heterocyclic carbenes
R1 = Ph, 2,4,6-Me3C6H2, 2,6-i-Pr2C6H3, i-Pr
2 = n-BuCl, (MeO)3SiCH2CH2CH2Cl
R
Equation 1 Synthesis of N,N¢-asymmetrically substituted imidazo-
lium salts 1–4
N,N¢-Disubstituted imidazolium salts are important inter-
mediates in the synthesis of transition metal complexes
that contain N-heterocyclic carbene (NHC) ligands.1
Complexes with NHC ligands have become increasingly
important in homogeneous2 and, more recently, in hetero-
geneous catalysis.3 N,N¢-Disubstituted imidazolium salts
have also found applications in their own right as ionic
liquids and ‘green’ solvents.4
All the N-alkyl-N¢-arylimidazolium salts were synthe-
sized by direct reaction of 1-chlorobutane or (3-chloro-
propyl)trimethoxysilane with the readily available
corresponding N-arylimidazoles using (i) 1,2-dimethoxy-
ethane as a solvent, and simultaneously (ii) an equimolar
(or larger) quantity of potassium iodide (Equation 1).14
The addition of potassium iodide leads to the formation by
precipitation of the sparingly soluble potassium chloride
from the reaction medium. The large N,N¢-disubstituted
imidazolium cations are presumably better stabilized in
the solid state with a big (I–) counteranion.
We have developed an interest in the synthesis and cata-
lytic properties of the nickel NHC complexes [Ni(h5-
C5R5)(NHC)X] [R = H (Cp) or Me (Cp*); X = Cl, I].5
These complexes may be prepared in a straightforward
manner by reaction of NiCp or Cp* species with imidazo-
lium salts. We are investigating the homogeneous catalyt-
ic properties of such species6 and are also looking into
grafting them with trimethoxysilyl-substituted NHC
ligands onto solid supports for heterogeneous catalytic ap-
plications.7
Preparations of the N-alkyl-N¢-isopropylimidazolium de-
rivatives 4a and 4b from the more reactive 1-isopropyl-
1H-imidazole do not require the addition of potassium io-
dide. Moreover, 4a does not even require any solvent ad-
dition, as simply refluxing neat 1-isopropyl-1H-imidazole
with an equimolar quantity of 1-chlorobutane affords 4a
in good yield. The synthesis of 4b is similar, but 1,2-
dimethoxyethane was added to slightly raise the reflux
temperature.
The repertoire of commercially available imidazolium
salts is limited. Herein we describe the easy syntheses of
N,N¢-asymmetrically substituted imidazolium salts,
which are either new (1b, 2a, 3a, 3b, 4b) or for which no
convenient route has been described (1a,8 2b,9 4a10). All
the prepared imidazolium salts contain either an N-bound
butyl group 1a–4a or else, an N-bound 3-(trimethoxysi-
lyl)propyl [CH2CH2CH2Si(OMe)3] group 1b–4b
(Equation 1, Table 1).7 Most contain N-arylimidazolium
moieties and have iodide as the anion.
The chloride salt of 2b, 2b¢, could be synthesized by heat-
ing 1-mesityl-1H-imidazole and (3-chloropropyl)tri-
methoxysilane in a microwave oven; the addition of
potassium iodide was not needed to form the cation, and
the chloride salt of 2b was obtained this way in 82% yield,
after 20 minutes of reaction time at 180 °C. Higher tem-
peratures led to decomposition, while addition of potassi-
um iodide or shorter reaction times produced less of the
desired cation.
SYNTHESIS 2009, No. 10, pp 1647–1650
x
x.
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x
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0
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Advanced online publication: 20.04.2009
DOI: 10.1055/s-0028-1088053; Art ID: P14008SS
© Georg Thieme Verlag Stuttgart · New York

1648
A. M. Oertel et al.
PAPER
Table 1 Preparation of N,N¢-Imidazolium Salts 1–4a
toluene (3 × 2 mL) and Et2O (3 × 2 mL) and dried in vacuo. The
product was obtained as a light brown solid (0.825 g, 50%).
R1
R1
1H NMR: d = 10.59 (br s, 1 H, NCHN), 7.80 (m, 2 H, Ph), 7.73 (dd,
J = 1.8 Hz, 1 H, NCH), 7.68 (t, J = 1.8 Hz, 1 H, NCH), 7.55 (m, 3
H, Ph), 4.59 (t, J = 7.4 Hz, 2 H, NCH2), 1.98 (tt, J = 7.4, 7.8 Hz, 2
H, NCH2CH2), 1.44 (qt, J = 7.8, 7.4 Hz, 2 H, CH2CH3), 0.97 (t,
J = 7.4 Hz, 3 H, CH3).
13C NMR: d = 135.4 (NCHN), 134.5 (ipso-CAr), 130.8 (o-CAr),
130.6 (p-CAr), 123.4 and 121.0 (NCH), 122.2 (m-CAr), 50.6 (NCH2),
32.4 (NCH2CH2), 19.7 (CH2CH3), 13.7 (CH3).
+
N
N
+
N
N
Si(OMe)3
X–
X–
1a–4a
1b–4b
Entry
Product
1a
R1
Ph
Ph
X
I
Yield (%)
1
2
3
4
5
6
7
8
9
50
1b
I
76
HRMS (MALDI TOF): m/z [M]+ calcd for C13H17N2: 201.1403;
found: 201.1386.
2a
2,4,6-Me3C6H2
2,4,6-Me3C6H2
2,4,6-Me3C6H2
2,6-i-Pr2C6H3
2,6-i-Pr2C6H3
i-Pr
I
87
2b
I
94
1-Phenyl-3-[3-(trimethoxysilyl)propyl]imidazolium Iodide (1b)
A suspension of 1-phenyl-1H-imidazole (1.586 g, 11.00 mmol), (3-
chloropropyl)trimethoxysilane (2.180 g, 2.00 mL, 10.97 mmol),
and KI (3.100 g, 18.67 mmol) in DME (40 mL) was vigorously
stirred at 85 °C for 63 h. The mixture was cooled to r.t. and the sol-
vent removed under vacuum. The residue was extracted with MeCN
(20 mL), filtered over Celite, and rinsed with MeCN (2 × 10 mL).
The MeCN was evaporated and the residue was washed with tolu-
ene (4 × 5 mL) and dried in vacuo for 3 h. The product was obtained
as a brown oil (3.631 g, 76%), that was contaminated with small
quantities of (3-chloropropyl)trimethoxysilane.
2b¢
3a
Cl
I
82b
79
3b
I
64
4a
Cl
Cl
quant.c
35d
4b
i-Pr
a Conditions: R1Cl, KI, DME, heat; unless otherwise stated.
b Microwave irradiation.
1H NMR: d = 10.57 (1 H, NCHN), 7.80–7.54 (m, 7 H, Ph, 2 NCH),
4.60 (t, J = 7.3 Hz, 2 H), 3.57 (9 H, Me), 2.10 (m, J = 8.1, 7.3 Hz, 2
H, NCH2CH2), 0.74–0.69 (m, 2 H, SiCH2).
c R1Cl, heat.
d R1Cl, DME, heat.
13C NMR: d = 135.3 (NCN), 134.5 (ipso-C, Ph), 130.8 and 122.2
(o-C, m-C, Ph), 130.6 (p-C, Ph), 123.5 and 121.0 (NCH), 52.5
(NCH2), 51.0 (Me), 24.3 (NCH2CH2), 6.1 (SiCH2).
HRMS (MALDI TOF): m/z [M]+ calcd for C15H23N2O3Si:
307.1472; found: 307.1457.
All the butylimidazolium iodide salts described here are
hydroscopic solids that appear to liberate traces of free io-
dine, in the presence of light, which makes the salts appear
cream colored, or even pale yellow unless very pure and/
or freshly prepared. The [3-(trimethoxysilyl)propyl]imi-
dazolium salts are nonvolatile oils that also often appear
slightly yellow colored. These oils are difficult to purify
1-Butyl-3-(2,4,6-trimethylphenyl)imidazolium Iodide (2a)
A suspension of 1-mesityl-1H-imidazole (1.856 g, 9.97 mmol), 1-
as they sometimes contain traces of (3-chloropropyl)tri- chlorobutane (2.835 g, 3.20 mL, 30.6 mmol), and KI (2.800 g, 16.9
mmol) in DME (40 mL) was vigorously stirred at 75 °C for 48 h.
methoxysilane and its hydrolysis products. Nevertheless
good spectroscopic data (1H, 13C{1H} and 13C DEPT
The mixture was cooled to r.t. and the solvent removed under vac-
uum. The residue was extracted with MeCN (30 mL), filtered over
a Celite pad, and rinsed with MeCN (2 × 10 mL). MeCN was evap-
orated, the resulting dense yellow oil was crystallized (toluene, 3
NMR and HRMS) were obtained for all the described
salts.
mL, r.t., 1 h). The crystals were washed with toluene (3 × 2 mL) and
Et2O (3 × 2 mL) and dried in vacuo. The product was obtained as a
All reactions were carried out using standard Schlenk techniques
under an atmosphere of dry argon. Solvents were distilled from ap-
propriate drying agents under argon prior to use. Solution NMR
white solid (3.221 g, 87%).
1H NMR: d = 10.06 (br s, 1 H, NCHN), 7.82 (dd, J = 1.7 Hz, 1 H,
spectra were recorded on a FT-Bruker Ultra Shield 300 spectrome-
NCH), 7.21 (dd, J = 1.7 Hz, 1 H, NCH), 6.99 (s, 2 H, m-H), 4.71 (t,
J = 7.3 Hz, 2 H, NCH2), 2.33 (s, 3 H, p-Me), 2.07 (s, 6 H, o-Me),
1,97 (tt, J = 7.3, 7.8 Hz, 2 H, NCH2CH2), 1.42 (qt, J = 7.8, 7.3 Hz,
2 H, CH2CH3), 0.97 (t, J = 7.3 Hz, 3 H, CH3).
1
ter operating at 300.13 MHz for H NMR, and at 75.47 MHz for
13C{1H} NMR. DEPT 13C spectra were obtained for all compounds
to help in the 13C signal assignments. Chemical shifts are referenced
to the residual deuterated solvent peaks. HRMS were recorded on a
MALDI-TOF Biflex Bruker mass spectrometer. Commercial com-
pounds were used as received. 1-Isopropyl-1H-imidazole,15 1-phe-
nyl-1H-imidazole,16 1-mesityl-1H-imidazole,17 and 1-(2,6-
diisopropylphenyl)-1H-imidazole16 were synthesized according to
published methods.
13C NMR: d = 141.6 (p-CAr), 137.5 (NCHN), 134.4 (o-CAr), 130.7
(ipso-CAr), 130.1 (m-CAr), 123.4 and 123.3 (NCH), 50.6 (NCH2),
32.7 (NCH2CH2), 21.3 (p-Me), 19.5 (CH2CH3), 18.0 (o-Me), 13.8
(CH3).
HRMS (MALDI TOF): m/z [M]+ calcd for C16H23N2: 243.1862;
found: 243.1856.
1-Butyl-3-phenylimidazolium Iodide (1a)
1-[3-(Trimethoxysilyl)propyl]-3-(2,4,6-trimethylphenyl)imida-
zolium Iodide (2b) by Thermal Synthesis
A suspension of 1-phenyl-1H-imidazole (0.720 g, 4.99 mmol), 1-
chlorobutane (0.470 g, 0.530 mL, 5.07 mmol), and KI (0.830 g, 5.00
mmol) in DME (10 mL) was vigorously stirred at 75 °C for 18 h.
The mixture was cooled to r.t. and the solvent removed under vac-
uum. The residue was extracted with MeCN (10 mL), filtered over
a Celite pad, and rinsed with MeCN (2 × 5 mL). The MeCN was
evaporated, the residue washed with toluene (5 × 3 mL), and crys-
tallized (toluene, 3 mL, r.t., 3 h). The crystals were washed with
A suspension of 1-mesityl-1H-imidazole (0.923 g, 4.96 mmol), (3-
chloropropyl)trimethoxysilane (1.003 g, 0.92 mL, 5.05 mmol), and
KI (0.996 g, 6.00 mmol) in DME (20 mL) was vigorously stirred at
85 °C for 60 h. The mixture was cooled to r.t. and the solvent re-
moved under vacuum. The residue was extracted with MeCN (12
mL), filtered over Celite, and rinsed with MeCN (3 × 4 mL). MeCN
Synthesis 2009, No. 10, 1647–1650 © Thieme Stuttgart · New York

PAPER
N¢-Activation of N-Arylimidazoles
1649
was evaporated and the residue was washed with hot toluene (3 × 5
mL) and dried in vacuo. The product was obtained as a pale yellow
solid (2.212 g, 94%).
(s, 9 H, OMe), 2.22 (hept, J = 6.8 Hz, 2 H, CHMe2), 2.06 (tt, J = 7.0,
8.1 Hz, 2 H, NCH2CH2), 1.16 (d, J = 6.8 Hz, 6 H, CHMe2), 1.09 (d,
J = 6.8 Hz, 6 H, CHMe2), 0.62 (m, J = 8.1 Hz, 2 H, CH2Si).
1H NMR: d = 9.99 (br s, 1 H, NCHN), 7.76 (dd, J = 1.7 Hz, 1 H,
NCH), 7.21 (dd, J = 1.7 Hz, 1 H, NCH), 6.99 (s, 2 H, m-H), 4.70 (t,
J = 7.2 Hz, 2 H, NCH2), 3.56 (s, 9 H, OMe), 2.33 (s, 3 H, p-Me),
2.10 (tt, J = 7.2, 7.9 Hz, 2 H, NCH2CH2), 2.08 (s, 6 H, o-Me), 0.68
(m, J = 7.9 Hz, 2 H, CH2Si).
13C NMR: d = 141.6 (p-CAr), 137.5 (NCN), 134.4 (o-CAr), 130.7 (ip-
so-CAr), 130.1 (m-CAr), 123.4 (2 NCH), 52.4 (NCH2), 51.0 (OMe),
24.6 (NCH2CH2), 21.3 (p-Me), 18.0 (o-Me), 5.8 (CH2Si).
13C NMR: d = 145.4 (o-CAr), 137.3 (NCHN), 132.0 (p-CAr), 130.0
(ipso-CAr), 124.7 (m-CAr), 124.6 and 123.8 (NCH), 52.1 (NCH2),
50.8 (OMe), 28.8 (CHMe2), 24.5 (CHMe2 and NCH2CH2), 24.2
(CHMe2), 5.6 (CH2Si).
HRMS (MALDI TOF): m/z [M]+ calcd for C21H35N2O3Si:
391.2423; found: 391.2411.
1-Butyl-3-isopropylimidazolium Chloride (4a)
1-Isopropyl-1H-imidazole (0.575 g, 5.22 mmol) was added to 1-
chlorobutane (0.930 g, 1.05 mL, 10.0 mmol). The mixture was
stirred at 75 °C for 12 h. The mixture was cooled to r.t. and excess
1-chlorobutane was removed under vacuum. The resultant oil was
further dried in vacuo (30 °C, 2 h). The product was obtained as a
colorless oil (1.059 g, quant.).
1H NMR: d = 10.80 (br s, 1 H, NCHN), 7.58 (dd, J = 1.8 Hz, 1 H,
NCH), 7.48 (dd, J = 1.8 Hz, 1 H, NCH), 4.85 (hept, J = 6.7 Hz, 1 H,
CHMe2), 4.30 (t, J = 7.5 Hz, 2 H, NCH2), 1.83 (tt, J = 7.5, 7.6 Hz,
2 H, NCH2CH2), 1.54 (d, J = 6.7 Hz, 6 H, CHMe2), 1.30 (qt, J = 7.6,
7.4 Hz, 2 H, CH2CH3), 0.87 (t, J = 7.4 Hz, 3 H, CH3).
13C NMR: d = 136.7 (NCHN), 122.2 and 120.1 (NCH), 53.2
(CHMe2), 49.7 (NCH2), 32.3 (NCH2CH2), 23.3 (CHMe2), 19.6
(CH2CH3), 13.5 (CH3).
HRMS (MALDI TOF): m/z [M]+ calcd for C10H19N2: 167.1543;
found: 167.1528.
HRMS (MALDI TOF): m/z [M]+ calcd for C18H29N2O3Si:
349.1942; found: 349.1940.
1-[3-(Trimethoxysilyl)propyl]-3-(2,4,6-trimethylphenyl)imid-
azolium Chloride (2b¢) by Microwave Synthesis
1-Mesityl-1H-imidazole (186 mg, 1.00 mmol) and (3-chloropro-
pyl)trimethoxysilane (204 mg, 0.19 mL, 1.03 mmol) were mixed in
a 10-mL sealed vessel and placed in a Discover CEM S-class micro-
wave oven operating at 2450 MHz. The mixture was heated rapidly
and kept at 180 °C for 20 min while stirred magnetically. The res-
inous product was purified following procedures described in the
thermal synthesis for 2b and was formed in 82% yield (by NMR).
1-Butyl-3-(2,6-diisopropylphenyl)imidazolium Iodide (3a)
A suspension of 1-(2,6-diisopropylphenyl)-1H-imidazole (2.310 g,
10.12 mmol), 1-chlorobutane (3.367 g, 3.80 mL, 36.37 mmol), and
KI (2.800 g, 16.87 mmol) in DME (40 mL) was vigorously stirred
at 75 °C for 50 h. The mixture was cooled to r.t. and the solvent re-
moved under vacuum. The residue was extracted with MeCN (20
mL), filtered over Celite, and rinsed with MeCN (3 × 3 mL). MeCN
was evaporated, the residue was washed with toluene (3 × 3 mL),
and crystallized (toluene, 3 mL, r.t., 2 h). The crystals were washed
with toluene (3 × 2 mL) and Et2O (3 × 2 mL) and dried in vacuo.
The product was obtained as a pale yellow solid (3.291 g, 79%).
1H NMR: d = 10.14 (br s, 1 H, NCHN), 7.88 (dd, J = 1.7 Hz, 1 H,
NCH), 7.54 (t, J = 8.0 Hz, 1 H, p-H), 7.31 (d, J = 8.0 Hz, 2 H, m-H),
7.21 (dd, J = 1.7 Hz, 1 H, NCH), 4.80 (t, J = 7.2 Hz, 2 H, NCH2),
2.29 (hept, J = 6.8 Hz, 2 H, CHMe2), 2.00 (tt, J = 7.2, 7.6 Hz, 2 H,
NCH2CH2), 1.43 (qt, J = 7.6, 7.4 Hz, 2 H, CH2CH3), 1.24 (d, J = 6.8
Hz, 6 H, CHMe2), 1.15 (d, J = 6.8 Hz, 6 H, CHMe2), 1.00 (t, J = 7.4
Hz, 3 H, CH3).
1-Isopropyl-3-[3-(trimethoxysilyl)propyl]imidazolium Chlo-
ride (4b)
A solution of 1-isopropyl-1H-imidazole (1.093 g, 9.92 mmol) and
(3-chloropropyl)trimethoxysilane (2.017 g, 1.85 mL, 10.15 mmol)
in DME (10 mL) was stirred at 85 °C for 96 h. The mixture was
cooled to r.t. and the solvent removed under vacuum. The resulting
oil was washed with toluene (5 × 3 mL) and dried in vacuo. The
product was obtained as a colorless oil (1.071 g, 35%).
1H NMR: d = 10.96 (br s, 1 H, NCHN), 7.49 (dd, J = 1.7 Hz, 1 H,
NCH), 7.33 (dd, J = 1.7 Hz, 1 H, NCH), 4.90 (hept, J = 6.7 Hz, 1 H,
CHMe2), 4.34 (t, J = 7.4 Hz, 2 H, NCH2), 3.52 (s, 9 H, OMe), 1.98
(tt, J = 7.4, 8.1 Hz, 2 H, NCH2CH2), 1.58 (d, J = 6.7 Hz, 6 H,
CHMe2), 0.61 (m, J = 8.1 Hz, 2 H, CH2Si).
13C NMR: d = 136.6 (NCHN), 122.1 and 120.4 (NCH), 53.2
(CHMe2), 51.7 (NCH2), 50.7 (OMe), 24.2 (NCH2CH2), 23.2
(CHMe2), 6.1 (CH2Si).
HRMS (MALDI TOF): m/z [M]+ calcd for C12H25N2O3Si:
273.1629; found: 273.1594.
13C NMR: d = 145.5 (o-CAr), 137.7 (NCHN), 132.2 (p-CAr), 130.2
(ipso-CAr), 124.9 (m-CAr), 124.5 and 123.5 (NCH), 50.6 (NCH2),
32.7 (NCH2CH2), 29.0 (CHMe2), 24.7 (CHMe2), 24.4 (CHMe2),
19.5 (CH2CH3), 13.8 (CH3).
HRMS (MALDI TOF): m/z [M]+ calcd for C19H29N2: 285.2325;
found: 285.2321.
Acknowledgment
1-(2,6-Diisopropylphenyl)-3-[3-(trimethoxysilyl)propyl]imida-
zolium Iodide (3b)
We thank the Ministère de l’Enseignement Supérieur et de la Re-
cherche (doctoral fellowship to A.M.O.), the CNRS and the Univer-
sité Louis Pasteur for financial support of this work. We gratefully
acknowledge the help of Dr. Baltenweck-Guyot in obtaining the
HRMS data, and of Dr. Benoit Louis for the microwave synthesis.
A suspension of 1-(2,6-diisopropylphenyl)-1H-imidazole (2.288 g,
10.02 mmol), (3-chloropropyl)trimethoxysilane (1.962 g, 1.80 mL,
9.87 mmol), and KI (1.999 g, 12.04 mmol) in DME (40 mL) was
vigorously stirred at 85 °C for 47 h. The mixture was cooled to r.t.
and the solvent removed under vacuum. The residue was extracted
with MeCN (20 mL), filtered over Celite, and rinsed with MeCN
(3 × 5 mL). MeCN was evaporated, the residue was washed with
hot toluene (3 × 5 mL) and dried in vacuo (30 °C, 2 h). The product
was obtained as a pale yellow solid (3.271 g, 64%).
References
(1) (a) Kissling, R. B.; Viciu, M. S.; Grasa, G. A.; Germaneau,
R. F.; Gueveli, T.; Pasareanu, M.-C.; Navarro-Fernandez,
O.; Nolan, S. P. Ionic Liquids As Green Solvents: Progress
and Prospects, ACS Symposium Series 856; Rogers, R. D.;
1H NMR: d = 9.90 (br s, 1 H, NCHN), 8.02 (dd, J = 1.7 Hz, 1 H,
NCH), 7.48 (t, J = 7.8 Hz, 1 H, p-H), 7.26 (t, J = 1.7 Hz, 1 H, NCH),
7.24 (d, J = 7.8 Hz, 2 H, m-H), 4.69 (t, J = 7.0 Hz, 2 H, NCH2), 3.50
Synthesis 2009, No. 10, 1647–1650 © Thieme Stuttgart · New York

1650
A. M. Oertel et al.
PAPER
(6) (a) Barth, C.; Milosevic, S.; Oertel, A. M.; Ritleng, V.;
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Conference, Nancy / France May 2008. (b) Ritleng, V.;
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(8) Compound 1a was prepared by addition of benzyne to 1-
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(9) The triethoxysilyl derivative of 2b was prepared by
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chloropropyl)triethoxysilane for five days: Koehler, K.;
Weigl, K. WO 2005016940, 2005.
(10) Compound 4a was briefly mentioned in the following
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(11) Cazin, C. S. J.; Veith, M.; Braunstein, P.; Bedford, R. B.
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(12) See for example: Tulloch, A. A. D.; Danopoulos, A. A.;
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(2) (a) See issues 5 and 6 of Coord. Chem. Rev. 2007, 251, 595–
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Chem. Soc. Rev. 2004, 33, 619. (c) Navarro, O.; Kelly, R. A.
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(d) Vasquez-Serrano, L. D.; Owens, B. T.; Buriak, J. M.
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(14) Another example where I– (in this case as NaI) was used in
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Organometallics 2004, 23, 6002.
(15) Starikova, O. V.; Dolgushin, G. V.; Larina, L. I.; Komarova,
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(17) Occhipinti, G.; Bjørsvik, H.-R.; Törnroos, K. W.; Fürstner,
A.; Jensen, V. R. Organometallics 2007, 26, 4383.
(5) (a) Ritleng, V.; Barth, C.; Brenner, E.; Milosevic, S.;
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(b) Milosevic, S.; Brenner, E.; Ritleng, V.; Chetcuti, M. J.
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Synthesis 2009, No. 10, 1647–1650 © Thieme Stuttgart · New York