¨
O. Dogˇan et al.
NMR Spectroscopy
2.52 (q, 2H,
(t, 1H,
J
=
8 Hz, NCH2CH2CHO2CH2CH2CH2), 4.79
J
=
8 Hz, NCH2CH2CHO2CH2CH2CH2), 3.88 (t,
8 Hz, NCH2CH2CHO2CH2CH2CH2), 3.71 (t, 2H,
8 Hz, NCH2CH2CHO2CH2CH2CH2), 1.81 (m, 2H,
1H NMR and 13C NMR spectra were recorded using a Varian As
400 Merkur spectrometer operating at 400 MHz (1H), 100 MHz
2H,
J
=
=
J
(
13C) in CDCl3 with tetramethylsilane as an internal reference.
NCH2CH2CHO2CH2CH2CH2). 13C NMR (100.5 MHz, CDCl3)
δ
The NMR studies were carried out in high-quality 5 mm NMR
tubes. Signals are quoted in parts per million as δ downfield
from tetramethylsilane (δ 0.00) as an internal standard. Coupling
constants (J-values) are given in hertz. NMR multiplicities are
abbreviated as follows: s = singlet, d = doublet, t = triplet, m =
multiplet signal.
(ppm) = 143.1 (NCHN), 131.8; 131.5; 127.2, 127.1; 113.9;
113.5 (C6H4), 139.9; 138.3; 130.3; 125.4 [2,4,6-(CH3)3C6H2CH2],
20.4 [2,6-(CH3)3C6H2CH2], 21.3 [4-(CH3)3C6H2CH2], 47.3
[2,4,6-(CH3)3C6H2-CH2], 42.8 (NCH2CH2CHO2CH2CH2CH2), 34.1
(NCH2CH2CHO2CH2CH2CH2), 99.5 (NCH2CH2CHO2CH2CH2CH2),
66.9 (NCH2CH2CHO2CH2CH2CH2), 25.6 (NCH2CH2CHO2CH2C
H2CH2). Anal. calcd for C23H30O2N2Br: C, 61.88; H, 6.77; N, 6.28.
Found: C, 61.86; H, 6.67; N, 6.25.
Gas Chromatography
All reactions were monitored on an Agilent 6890N GC system by
GC-FID with an HP-5 column of 30 m length, 0.32 mm diameter
and 0.25 µm film thickness.
[1-(3,4,5-trimethoxybenzyl)-3-(2-(ethyl)-1,3-
dioxane)benzimidazolium bromide, 1c
Yield: 4.55 g (90%); m.p.: 218–219 ◦C. ν(CN) = 1595 cm−1. 1H NMR
(399.9 MHz, CDCl3) δ (ppm) = 11.41 (s, 1H, NCHN), 7.56–7.83
(m, 4H, C6H4), 6.93 [s, 2H, 3,4,5-(OCH3)3C6H2CH2], 5.82 [s, 2H,
3,4,5-(OCH3)3C6H2CH2], 3.84 [s, 6H, 3,5-(OCH3)3C6H2 CH2], 3.77
[s, 3H, 4-(OCH3)3C6H2CH2], 4.77 (t, 2H, J = 5.6 Hz, NCH2CH2CH),
2.89 (q, 2H, J = 5.6 Hz, NCH2CH2CH), 4.72 (t, 1H, J = 8.0 Hz,
NCH2CH2CH), 3.67 (t, 2H, J = 6.8 Hz, NCH2CH2CHO2CH2CH2CH2),
3.87 (t, 2H, J = 6.8 Hz, NCH2CH2CHO2CH2CH2CH2), 1.84 (m,
2H, NCH2CH2O2CH2CH2CH2). 13C NMR (100.5 MHz, CDCl3) δ
(ppm) = 143.3 (NCHN), 153.7; 138.5; 126.9; 106.3 (3,4,5-
(OCH3)3C6H2CH2), 131.4; 131.1; 128.6;127.0; 113.7; 113.0 (C6H4),
56.8 [3,5-(OCH3)3C6H2CH2], 60.8 [4-(OCH3)3C6H2CH2], 51.2
[3,4,5-(OCH3)3C6H2CH2], 42.5 (NCH2CH2CH), 33.9 (NCH2CH2CH),
99.0 (NCH2CH2CH), 66.7 (NCH2CH2CHO2CH2CH2CH2), 25.3
(NCH2CH2CHO2CH2CH2CH2). Anal. calcd for C23H29O5N2Br: C,
55.99; H, 5.92; N, 5.68. Found: C, 55.94; H, 5.95; N, 5.61.
Column Chromatography
Column chromatography was performed using silica gel 60
(70–230 mesh). Solvent ratios are given as v/v.
GeneralProcedureforthePreparationoftheBenzimidazolium
Salts (1)
To a solution of 1-alkylbenzimidazole (5 mmol) in DMF (10 ml) was
added under argon slowly 2-(2-bromoethyl)-1,3-dioxane (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
(3 × 15 ml), and dried under vacuum. The crude product was
recrystallized from EtOH/Et2O. Melting points were measured in
open capillary tubes.
[1-(methoxyethyl)-3-(2-(ethyl)-1,3-dioxane)]benzimidazolium
bromide, 1a
General procedure for the preparation of the palladium(NHC)
complexes, 2
Yield: 3.14 g (87%); m.p.: 152–153 ◦C, ν(CN) = 1567 cm−1
.
To a solution of benzimidazolium salts (10 mmol) in DMSO (5 ml)
was added under argon palladium(II) acetate (5 mmol) and the
resulting mixture was stirred at room temperature for 2 h, 60 ◦C
for 4 h, at 80 ◦C for 2 h and finally at 110 ◦C for 2 h. Volatiles were
removedinvacuoandtheresiduewaswashedtwicewithTHF(5 ml)
and then crude product was recrystallized from CH2Cl2 –Et2O.
1H NMR (399.9 MHz, CDCl3) δ (ppm) = 11.0 (s, 1H, NCHN),
7.61–7.89 (m, 4H, C6H4), 3.36 (s, 3H, NCH2CH2OCH3), 4.77
(t, 2H, J = 4 Hz, NCH2CH2OCH3), 4.91 (t, 2H, J = 4 Hz,
NCH2CH2OCH3), 4.01 (t, 2H, J = 4 Hz, NCH2CHO2CH2CH2), 2.32
(m, 2H, J = 4 Hz, NCH2CH2CHO2CH2CH2CH2), 4.82 (t, 1H,
J
=
4 Hz, NCH2CH2CHO2CH2CH2CH2), 3.96 (t, 2H,
J
=
4 Hz, NCH2CH2CHO2CH2CH2CH2), 3.78 (t, 2H,
J
=
4 Hz,
NCH2CH2CHO2CH2CH2CH2), 1.92 (m, 2H, NCH2CH2CHO2
CH2CH2CH2). 13C NMR (100.5 MHz, CDCl3) δ (ppm) = 143.5
Bis[1-(methoxyetyl)-3-(2-(ethyl)-1,3-dioxane)]benzimidazol-2-
ylidene]dibromo palladium(II),2a
(NCHN),
132.2;
131.3;
127.1;
113.0
(C6H4),
59.3
Yield: 0.35 g, (75%); m.p.: 312–313 ◦C, ν(CN) = 1472 cm−1
.
1H
(NCH2CH2OCH3), 70.7 (NCH2CH2OCH3), 47.9 (NCH2CH2OCH3),
42.8 (NCH2CH2CHO2CH2CH2CH2), 34.2 (NCH2CH2CHO2CH2CH2
CH2), 99.2 (NCH2CH2CHO2CH2CH2CH2), 66.9 (NCH2CH2CHO2CH2
CH2CH2), 25.6 (NCH2CH2CHO2CH2CH2CH2). Anal. calcd for
C16H24O3N2Br: C: 51.62; H: 6.50; N: 7.52 Found C: 51.68; H: 6.57; N:
7.59.
NMR (399.9 MHz, CDCl3) δ (ppm) = 7.27–7.73 (m, 4H, C6H4), 3.31
(s, 3H, NCH2CH2OCH3), 4.68 (t, 2H, J = 6.6 Hz, NCH2CH2OCH3),
4.89 (t, 2H, J = 6.6 Hz, NCH2CH2OCH3), 4.39 (t, 2H, J = 4.8 Hz,
NCH2CHO2CH2CH2), 2.48 (m, 2H, NCH2CH2CHO2CH2CH2CH2),
4.94 (t, 1H,
J
=
4.8 Hz, NCH2CH2CHO2CH2CH2CH2),
4.06 (m, 4H, NCH2CH2CHO2CH2CH2CH2), 2.06 (m, 2H,
NCH2CH2CHO2CH2CH2CH2). 13C NMR (100.5 MHz, CDCl3)
[1-(2,4,6-trimethylbenzyl)-3-(2-(ethyl)-1,3-
dioxane)]benzimidazolium bromide, 1b
δ
(ppm)
=
173.5 (Pdcarbene), 134.4; 133.8; 123.5;
112.5 (C6H4), 58.9 (NCH2CH2OCH3), 70.7 (NCH2CH2OCH3),
49.3 (NCH2CH2OCH3), 43.6 (NCH2CH2CHO2CH2CH2CH2), 34.1
(NCH2CH2CHO2CH2CH2CH2), 99.3 (NCH2CH2CHO2CH2CH2CH2),
66.7 (NCH2CH2CHO2CH2CH2CH2), 25.8 (NCH2CH2CHO2CH2CH2
CH2). Anal. calcd for C16H23Br2N2O3Pd: C: 34.46; H: 4.16; N: 5.02
Found: C: 34.41; H: 4.12; N: 4.95.
Yield: 3.87 g (85%); m.p.: 203–204 ◦C, ν(CN) = 1571 cm−1. 1H NMR
(399.9 MHz, CDCl3) δ (ppm) = 10.68 (s, 1H, NCHN), 7.36–7.80 (m,
4H, C6H4), 6.94 [s, 2H, 2,4,6-(CH3)3C6H2CH2], 5.85 [s, 2H, 2,4,6-
(CH3)3C6H2CH2], 2.34 [s, 6H, 2,6-(CH3)3C6H2CH2], 2.30 [s, 3H, 4-
(CH3)3C6H2CH2], 4.81 (t, 2H, J = 8 Hz, NCH2CH2CHO2CH2CH2CH2),
c
wileyonlinelibrary.com/journal/aoc
Copyright ꢀ 2010 John Wiley & Sons, Ltd.
Appl. Organometal. Chem. 2011, 25, 163–167