LETTER
A Facile Route to Sterically Hindered and Non-Hindered 4¢-Aryl-2,2¢:6¢,2¢¢-Terpyridines
1253
for 24 h. After cooling down to ambient temperature, the solution
was evaporated to dryness under reduced pressure. Recrystalliza-
tion of the residue from CHCl3–MeOH afforded a yellow crystalline
thesis of ligand 12 with the bulkier 9-anthryl group was
problematic due to the insolubility of the intermediate, 2-
[1-(9-anthryl)-3-oxo-3-prop-2-enyl] pyridine, in EtOH.
Treatment of the same starting materials at reflux kept the
enone intermediate in solution leading to a one-step syn-
thesis of 4¢-(9-anthryl)-tpy. It is noteworthy that this is the
first example of a one-step synthesis of tpy-based ligands
with bulky substituents in the 4¢-position.
1
solid (0.28 g, 0.68 mmol, 27%). H NMR (400 MHz, CDCl3): d =
8.82 (d, J = 7.9 Hz, 2 H, H3,3¢¢), 8.66 (d, J = 0.3 Hz, 2 H, H6,6¢¢), 8.63
(s, 2 H, H3¢,5¢), 8.57 (s, 1 H, HAn10), 8.09 (d, J = 8.7 Hz, 2 H, HAn1,8),
7.95 (t, J = 7.5 Hz, 2 H, H4,4¢¢), 7.73 (d, J = 8.7 Hz, 2 H, HAn2,7), 7.49
(t, J = 7.2 Hz, 2 H, HAn3,6), 7.39–7.36 (m, 4 H, H5,5¢¢,An4,5). 13C NMR
(100 MHz, CD3Cl): d = 156.5, 156.0, 150.0, 149.6, 137.4, 134.7,
131.6, 129.9, 128.8, 127.8, 126.8, 126.3, 125.6, 124.3, 124.3, 121.9.
FAB-MS: 409.5 [M]+. Anal. Calcd for C29H19N3: C, 85.06; H, 4.68;
N, 10.26. Found: C, 85.27; H, 4.65; N, 10.08.
To survey the scope of the reaction conditions for heteroa-
tom aromatic aldehydes, the 2-furyl-tpy (13) and 4-py-
ridyl-tpy (14) were also synthesized in moderate yield.
In conclusion, we have developed mild reaction condi-
tions for the synthesis of 4¢-aryl and 4¢-heteroaryl substi-
tuted tpys. These reaction conditions are compatible with
various functional groups and provide an efficient route to
tridentate 2,2¢:6¢,2¢¢-terpyridine-based ligands.
Acknowledgment
The authors thank the Natural Sciences and Engineering Research
Council (NSERC) of Canada and the Université de Montréal for fi-
nancial support.
References
Representative Procedure for Ligands 1–11, 13–16
Synthesis of 1
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2-Acetylpyridine (4.84 g, 40 mmol) was added into a solution of
benzaldehyde (2.12 g, 20 mmol) in EtOH (100 mL). KOH pellets
(3.08 g, 85%, 40 mmol) and aq NH3 (58 mL, 29.3%, 50 mmol) were
then added to the solution. The solution was stirred at r.t. for 4 h.
The off-white solid was collected by filtration and washed with
EtOH (3 × 10 mL). Recrystallization from CHCl3–MeOH afforded
white crystalline solid 1 (3.24 g, 10.5 mmol, 53%). 1H NMR (400
MHz, CDCl3): d = 8.76 (s, 2 H, H3¢, 5¢), 8.74 (d, J = 6.5 Hz, 2 H,
H6,6¢¢), 8.68 (d, J = 8.0 Hz, 2 H, H3,3¢¢), 7.92 (d, J = 6.9 Hz, 2 H, HPh),
7.90 (t, J = 7.5 Hz, 2 H, H4, 4¢¢), 7.52 (t, J = 6.9 Hz, 2 H, HPh2,6), 7.46
(t, J = 6.9 Hz, 1 H, HPh3,5), 7.37 (dd, J = 7.5, 5.0 Hz, 2 H, H5,5¢¢). 13
C
NMR (100 MHz, CDCl3): d = 156.5, 156.2, 150.8, 149.4, 138.8,
137.4, 129.5, 129.3, 127.8, 124.3, 121.9, 119.4. Anal. Calcd for
C21H15N3: C, 81.53; H, 4.89; N, 13.58. Found: C, 81.15; H, 4.98; N,
13.50.
4¢-(2,3-Dimethoxyphenyl)-2,2¢:6¢,2¢¢-terpyridine (9)
Yield 27%. 1H NMR (400 MHz, CDCl3): d = 8.72 (dt, J = 6.7, 0.7
Hz, 2 H, H6,6¢¢), 8.70 (s, 2 H, H3¢,5¢), 8.68 (d, J = 8.0 Hz, 2 H, H3,3¢¢),
7.88 (td, J = 7.7, 1.7 Hz, 2 H, H4,4¢¢), 7.34 (ddd, J = 7.4, 4.8, 0.8 Hz,
2 H, H5,5¢¢), 7.18–7.16 (m, 2 H, HPh5,6), 7.02 (m, 1 H, HPh4), 3.95 (s,
3 H, HCH3), 3.73 (s, 3 H, HCH3). 13C NMR (100 MHz, CDCl3): d =
156.8, 155.8, 153.5, 149.6, 148.7, 147.3, 137.2, 134.2, 124.6, 124.1,
122.8, 122.0, 121.7, 113.3, 61.5, 56.4. FAB-MS: 370.4 [M + 1]+.
Anal. Calcd for C23H19N3O2: C, 74.78; H, 5.18; N, 11.37. Found: C,
74.26; H, 5.15; N, 11.09.
(6) Goodall, W.; Williams, J. A. G. Chem. Commun. 2001,
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Ward, M. D.; Corr, S. Inorg. Chim. Acta 1988, 141, 201.
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4¢-(1-Naphthyl)-2,2¢:6¢,2¢¢-terpyridine (11)
Yield 32%. 1H NMR (400 MHz, CDCl3): d = 8.76 (d, J = 7.8 Hz, 2
H, H3,3¢¢), 8.71 (d, J = 3.7 Hz, 2 H, H6,6¢¢), 8.68 (s, 2 H, H3¢,5¢), 8.01–
7.90 (m, 5 H, H4,4¢¢,nap), 7.63–7.49 (m, 4 H, Hnap), 7.37 (t, J = 5.6 Hz,
2 H, H5,5¢¢). 13C NMR (100 MHz, CD3Cl): d = 156.7, 155.9, 151.3,
149.6, 138.4, 137.3, 134.1, 131.4, 129.1, 128.8, 127.5, 127.0, 126.4,
126.0, 125.7, 124.3, 122.8, 121.8. FAB-MS: 359.1 [M]+. Anal.
Calcd for C25H17N3: C, 83.54; H, 4.77; N, 11.69. Found: C, 83.27;
H, 4.79; N, 11.61.
4¢-(9-Anthryl)-2,2¢:6¢,2¢¢-terpyridine (12)
Ligand 12
2-Acetylpyridine (0.61 g, 5.0 mmol) was added into a solution of 9-
anthraldehyde (0.52 g, 2.5 mmol) in EtOH (25 mL). KOH pellets
(0.39 g, 85%, 5.0 mmol) and aq NH3 (7.5 mL, 29.3%, 6.3 mmol)
were then added to the solution. The solution was heated at reflux
Synlett 2005, No. 8, 1251–1254 © Thieme Stuttgart · New York