912
M.C. Jahnke et al. / Tetrahedron 65 (2009) 909–913
4.2.5. 1,10-(Pyrazine-2,3-diyldimethanediyl)bis(3-(2-
4.4. X-ray structure determination of 3$H2O and 8$2H2O
methylphenyl)-1H-imidazol-3-ium) dibromide 5
Yield: 61.5%. 1H NMR (400.1 MHz, CDCl3):
8.31 (s, 2H, pyrazine–H), 7.73 (s, 2H, imidazolium–H), 7.47–7.41 (m,
2H, Ar–H), 7.39–7.30 (m, 6H, Ar–H), 7.27 (s, 2H, imidazolium–H),
6.31 (s, 4H, pyrazine–CH2–N), 2.21 (s, 6H, o-CH3–Ph). 13C NMR
d
10.49 (s, 2H, NCHN),
4.4.1. X-ray structure determination of compounds 3$H2O
and 8$2H2O
Diffraction data for 3$H2O were obtained on a Bruker SMART
diffractometer equipped with a rotating anode using Cu K
tion (
¼1.54184 Å). Data for compound 8$2H2O were collected on
a Bruker AXS APEX CCD diffractometer equipped with a rotating
a radia-
(100.6 MHz, CDCl3):
d
145.7, 143.6 (pyrazine–C), 138.6 (NCN), 133.8,
l
133.4, 132.2, 131.2, 127.8, 126.2 (Ar–C), 124.5, 122.4 (imidazolium–
C), 50.9 (pyrazine–CH2–N), 17.8 (o-CH3–Ph). Anal. Calcd for
C26H26N6Br2 (582.3): C, 53.63; H, 4.50; N, 14.43. Found: C, 53.46; H,
4.27; N, 14.21%. MS (MALDI-TOF): m/z 503, 501 [MꢁBr]þ.
anode using graphite-monochromated Mo
Ka
radiation
(
l
¼0.71073 Å). The diffraction data were measured at 153(2) K in
the range 6.5ꢂ2
Q
ꢂ144.8ꢀ for 3$H2O and 3.3ꢂ2
Q
ꢂ53.0ꢀ for
8$2H2O. Structure solution26 and refinement27 were achieved with
standard Patterson and Fourier techniques. All non-hydrogen
atoms were refined with anisotropic displacement parameters.
Hydrogen atoms were added to the structure models on calculated
positions.
4.2.6. 1,10-(Pyrazine-2,3-diyldimethanediyl)bis(3-(2,4,6-
trimethylphenyl)-1H-imidazol-3-ium) dibromide 6
Yield: 64.9%. 1H NMR (400.1 MHz, CDCl3):
d 9.68 (s, 2H, NCHN),
8.29 (s, 2H, pyrazine–H), 8.24 (s, 2H, imidazolium–H), 7.20 (s, 2H,
imidazolium–H), 6.96 (s, 4H, Ar–H), 6.76 (s, 4H, pyrazine–CH2–N),
2.29 (s, 6H, Ar–CH3), 2.05 (s, 12H, Ar–CH3). 13C NMR (100.6 MHz,
4.4.2. Selected crystallographic details for 3$H2O
CDCl3):
d
¼147.5, 143.4 (pyrazine–C), 141.7 (Ar–C), 138.9 (NCN),
C20H32N6Br2O, M¼532.34, colorless crystal, 0.32ꢃ0.15ꢃ
134.8, 130.2, 129.8 (Ar–C), 126.4, 122.5 (imidazolium–C), 51.2 (pyr-
azine–CH2–N), 21.6 (Ar–CH3), 14.7 (Ar–CH3). Anal. Calcd for
C30H34N6Br2 (638.4): C, 56.44; H, 5.37; N, 13.16. Found: C, 55.98; H,
5.58; N, 12.66%. MS (MALDI-TOF): m/z 559, 557 [MꢁBr]þ.
0.08 mm3, triclinic, space group P-1, a¼8.4588(3), b¼10.8379(4),
c¼13.5766(5) Å,
a
¼95.392(3),
b
¼92.054(3),
g
¼95.207(3)ꢀ,
V¼1232.79(8) Å3, rcalcd¼1.434 g cmꢁ3
,
m
¼4.342 mmꢁ1, empirical
absorption correction (0.3372ꢂTꢂ0.7227), Z¼2, 7049 intensities
collected (ꢄh, ꢄk, ꢄl), 4165 independent intensities (Rint¼0.0659),
refinement of 264 parameters against all unique jF2j, R¼0.0659,
4.2.7. 1,10-(Pyrazine-2,3-diyldimethanediyl)bis(3-(2,6-diiso-
propylphenyl)-1H-imidazol-3-ium) dibromide 7
wR¼0.1590 for 2791 contributing intensities [Iꢅ2
s(I)].
Yield: 72.3%. 1H NMR (400.1 MHz, CDCl3):
d 9.64 (s, 2H, NCHN),
8.50 (s, 2H, pyrazine–H), 7.96 (s, 2H, imidazolium–H), 7.19 (s, 2H,
imidazolium–H), 7.49 (t, 2H, 3J¼7.8 Hz, Ar–H), 7.26 (d, 4H,
3J¼7.8 Hz, Ar–H), 6.75 (s, 4H, pyrazine–CH2–N), 2.42 (sept, 4H,
3J¼7.0 Hz, Ar–CH(CH3)2), 1.16, 1.14 (d, 12H, 3J¼7.0 Hz, Ar–CH(CH3)2).
4.4.3. Selected crystallographic details for 8$2H2O
C22H22N8Br2O2, M¼590.30, colorless crystal, 0.08ꢃ0.04ꢃ
0.02 mm3, monoclinic, space group P21/n, a¼14.983(3), b¼
10.100(2),
c¼16.163(3) Å,
b
¼105.566(2)ꢀ,
V¼2356.2(7) Å3,
13C NMR (100.6 MHz, CDCl3):
d
147.6 (pyrazine–C), 145.9 (Ar–C),
rcalcd¼1.664 g cmꢁ3
,
m
¼3.478 mmꢁ1, empirical absorption correc-
143.3 (pyrazine–C), 139.5 (NCN), 132.2, 130.6, 126.3 (Ar–C), 125.0,
123.5 (imidazolium–C), 51.2 (pyrazine–CH2–N), 29.0 (Ar–
CH(CH3)2), 24.9, 24.6 (Ar–CH(CH3)2). Anal. Calcd for C36H46N6Br2
(722.6): C, 59.84; H, 6.42; N, 11.63. Found: C, 59.46; H, 6.23; N,
tion (0.7683ꢂTꢂ0.9337), Z¼4, 21,019 intensities collected (ꢄh, ꢄk,
ꢄl), 4892 independent intensities (Rint¼0.0654), refinement of 307
parameters against all unique jF2j, R¼0.0752, wR¼0.1910 for 3740
contributing intensities [Iꢅ2
s(I)].
11.41%. MS (MALDI-TOF): m/z 643, 641 [MꢁBr]þ, 281 [Mꢁ2Br]2þ
.
Crystallographic data (excluding structure factors) have been
deposited with the Cambridge Crystallographic Data Centre as
supplementary publication. CCDC-702780 for 3$H2O and CCDC-
702781 for 8$2H2O. Copies of the data can be obtained free of
4.2.8. 1,10-(Pyrazine-2,3-diyldimethanediyl)bis(3-(2-pyridine)-1H-
imidazol-3-ium) dibromide 8
Yield: 58.7%. 1H NMR (400.1 MHz, DMSO-d6):
d 10.40 (s, 2H,
NCHN), 8.71–8.66 (m, 4H, pyrazine–H and pyridine–H), 8.64 (s, 2H,
imidazolium–H), 8.29–8.23 (m, 2H, pyridine–H), 8.21 (s, 2H, imid-
azolium–H), 8.17–8.13 (m, 2H, pyridine–H), 7.71–7.66 (m, 2H,
pyridine–H), 6.15 (s, 4H, pyrazine–CH2–N). 13C NMR (100.6 MHz,
Acknowledgements
Financial support by the Deutsche Forschungsgemeinschaft (SFB
424 and IRTG 1444) is gratefully acknowledged. M.H. wishes to
acknowledge the funding provided for his stay in Cardiff by the
Higher Education Commission of Pakistan.
DMSO-d6):
d
¼149.7 (pyridine–C), 147.4 (pyrazine–C), 146.6 (pyri-
dine–C), 144.2 (pyrazine–C), 141.1 (pyridine–C), 136.7 (NCN), 125.8,
125.3 (imidazolium–C), 119.5, 114.7 (pyridine–C), 50.3 (pyrazine–
CH2–N). Anal. Calcd for C22H20N8Br2 (556.3): C, 47.50; H, 3.62; N,
20.14. Found: C, 47.41; H, 3.23; N, 19.49%. MS (MALDI-TOF): m/z 477,
475 [MꢁBr]þ.
References and notes
1. Arduengo, A. J., III; Harlow, R. L.; Kline, M. J. Am. Chem. Soc. 1991, 113, 361.
2. (a) Hahn, F. E.; Jahnke, M. C. Angew. Chem., Int. Ed. 2008, 47, 3122; (b) Hahn, F. E.
Angew. Chem., Int. Ed. 2006, 45, 1348; (c) Bourissou, D.; Guerret, O.; Gabbai, F. P.;
Bertrand, G. Chem. Rev. 2000, 100, 39.
3. (a) Hahn, F. E.; Paas, M.; Le Van, D.; Lu¨ gger, T. Angew. Chem., Int. Ed. 2003, 42,
5243; (b) Bon, R. S.; de Kanter, F. J. J.; Lutz, M.; Spek, A. L.; Jahnke, M. C.; Hahn,
F. E.; Groen, M. B.; Orru, R. V. A. Organometallics 2007, 26, 3639.
4. (a) Bazinet, P.; Yap, G. P. A.; Richeson, D. S. J. Am. Chem. Soc. 2003, 125, 13314; (b)
Bazinet, P.; Ong, T.-G.; O’Brien, J. S.; Lavoie, N.; Bell, E.; Yap, G. P. A.; Korobkov, I.;
Richeson, D. S. Organometallics 2007, 26, 2885; (c) Otto, M.; Conejero, S.; Canac,
Y.; Romanenko, V. D.; Rudzevitch, V.; Bertrand, G. J. Am. Chem. Soc. 2004, 126,
1016.
5. (a) Iglesias, M.; Beetstra, D. J.; Stasch, A.; Horton, P. N.; Hursthouse, M. B.; Coles,
S.; Cavell, K. J.; Dervisi, A.; Fallis, I. A. Organometallics 2007, 26, 4800; (b) Ig-
lesias, M.; Beetstra, D. J.; Knight, J. C.; Ooi, L.-L.; Stasch, A.; Coles, S.; Male, L.;
Hursthouse, M. B.; Cavell, K. J.; Dervisi, A.; Fallis, I. A. Organometallics 2008, 27,
3279.
4.3. General procedure for the Heck coupling reaction
Heck coupling reactions were carried out using 4-bromo benz-
aldehyde (1.0 mmol), an olefinic substrate (1.4 mmol), and cesium
carbonate as base (0.65 g, 2.0 mmol) dissolved in 5 mL of N,N-
dimethylacetamide (DMAc). An appropriate amount of one of the
diimidazolium salts 1–8 (1.0 mol %), palladium acetate (2.0 mol %),
and di-(ethylene glycol) n-butyl ether as internal standard were
added to this mixture. The reaction mixture was heated to 110 ꢀC
for the selected reaction time. Coupling product yields were cal-
culated from GC data relative to the residual aryl halide. The
product identity was confirmed by GC–MS.
6. (a) Herrmann, W. A. Angew. Chem., Int. Ed. 2002, 41, 1290; (b) Peris, E.; Crabtree,
R. H. Coord. Chem. Rev. 2004, 248, 2239.