Synthesis of vinyl-substituted polypyridyl ligands through suzuki-miyaura cross-coupling of potassium vinyltrifluoroborate with bromopolypyridines

Article abstract of DOI:10.1021/jo200590r

Suzuki-Miyauru cross-coupling of bromopolypyridines with potassium vinyltrifluoroborate affords vinyl-substituted polypyridyl ligands in moderate to good yields. This reaction allows simple and practical syntheses of numerous vinyl-substituted polypyridin

Full text of DOI:10.1021/jo200590r

NOTE
pubs.acs.org/joc
Synthesis of Vinyl-Substituted Polypyridyl Ligands through
SuzukiꢀMiyaura Cross-Coupling of Potassium Vinyltrifluoroborate
with Bromopolypyridines
Hai-Jing Nie, Jiannian Yao, and Yu-Wu Zhong*
Beijing National Laboratory for Molecular Sciences, CAS Key Laboratory of Photochemistry, Institute of Chemistry,
Chinese Academy of Sciences, Beijing 100190, People’s Republic of China
S Supporting Information
b
ABSTRACT: SuzukiꢀMiyauru cross-coupling of bromopoly-
pyridines with potassium vinyltrifluoroborate affords vinyl-
substituted polypyridyl ligands in moderate to good yields.
This reaction allows simple and practical syntheses of numerous
vinyl-substituted polypyridines, such as 40-vinyl-2,20:60,200-ter-
pyridine, 5,50-divinyl-2,20-bipyridine, and 4,40-divinyl-2,20-bi-
pyridine. In addition, a new ruthenium complex, [Ru(5,50-
divinyl-2,20-bipyridine)3]2þ, was synthesized and found to
undergo reductive electropolymerization smoothly.
inyl-substituted polypyridyl transition-metal complexes have
received considerable interest in the past three decades.
elimination of 40-(alkyloxy)ethylterpyridine.5 Both starting ma-
terials could be obtained through simple transformations from
40-methylterpyridine, which, however, needs multistep reactions
to prepare. An improved procedure was reported later, utilizing
the palladium-catalyzed Stille coupling of vinyltributyltin with
2,20:60,200-terpyridinyl triflate.14 However, the toxicities of orga-
nostannane reagents present a safety and environmental issue.
The most popular method for the synthesis of vbpy starts from
the treatment of 4,40-dimethyl-2,20-bipyridine with LDA or
nBuLi,15 followed by the addition of formaldehyde or (chloro-
methyl)methyl ether, respectively, and features a elimination of
the resulting 4-hydroxyethyl-40-methyl-2,20-bipyridine or 4-methoxy-
ethyl-40-methyl-2,20-bipyridine as the key step. The biggest
difficulty of this method lies in the separation of the final product
vbpy from 4,40-dimethyl-2,20-bipyridine.16 In this paper, we report a
general and practical method for the synthesis of vinyl-substi-
tuted polypyridines through SuzukiꢀMiyauru cross-coupling of
potassium vinyltrifluoroborate with corresponding bromo-sub-
stituted polypyridines.17 This new method is not only useful for
the synthesis of some known ligands, such as vtpy, 5,50-divinyl-
2,20-bipyridine, and 4,40-divinyl-2,20-bipyridine, in a very simple
way, but also produces a number of new vinyl-substituted
polypyridines.
V
Metallopolymers or copolymers are readily accessible from these
complexes by either chemically1 or electrochemically triggered
polymerization.2 In the latter case, the electrode used ends up
with a coated redox-active polymeric film whose composition,
electrochemistry, and thickness could be well controlled. Among
complexes studied, those coordinating with vbpy (4-methyl-40-
vinyl-2,20-bipyridine) or vtpy (40-vinyl-2,20:60,200-terpyridine) ligand
are very popular. For example, [Ru(vbpy)3]2þ,3 [Ru(vbpy)2-
(bpy)]2þ (bpy =2,20-bipyridine),3 [Ru(vbpy)2(py)2]2þ (py =
pyridine),3 [Ru(vbpy)2(dpp)]2þ (dpp =2,3-bis(2-pyridyl)-
pyrazine),4 [Ru(vbpy)(bpy)2]2þ,3 [Fe(vbpy)3]2þ,3 [Ru(vtpy)2]2þ 5
,
[Co(vtpy)2]2þ,6 [Fe(vtpy)2]2þ,5 and an iron porphyrin molecule7
containing four meso-appended [Ru(vbpy)2(bpy)] unit could be
readily deposited on various electrodes by reductive electropo-
lymerization to afford stable, adherent, electrochemically active
films. These films are found to be useful in electrocatalytic
reactions,6ꢀ8 generation of ECL (electrogenerated chemilumine-
scence)9 and spatial electrochromism,10 constructing rectifying
interfaces,11 and stabilizing TiO2 photoanodes,12 etc. In addition
to applications in polymer chemistry, vinyl-substituted polypyridyl
complexes, such as [Ir(ppy)2(vbpy)]þ (ppy =2-phenylpyridine),
were recently reported to boost the photocatalytic hydrogen
production compared to the analogous nonvinyl compounds.13
Although this chemistry has been explored for many years, it
should be noted that new methodology for the synthesis of vinyl-
substituted polypyridine ligands or complexes is still in demand.
Procedures developed to date suffer from long synthetic routes
and low overall yields, and they are only applicable for a specific
compound. The earliest report regarding the synthesis of vtpy
involves the Wittig reaction of 40-formylterpyridine or the
We decided to employ the above-mentioned reaction for the
synthesis of vinyl-substituted polypyridines based on the following
considerations. First, potassium vinyltrifluoroborate is a bench-
stable, commercially available, and environmentally benign solid,
and it has been proven successful in the vinylation of a vast number
of aryl and heteroaryl electrophiles.18 Second, bromo-substituted
Received: March 20, 2011
Published: April 27, 2011
r
2011 American Chemical Society
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Table 1. Synthesis of Vinyl-Substituted Polypyridyl Ligandsa
substituted cyclometalating ligand 4 was attempted. The pre-
vious conditions worked well for the reaction between potassium
vinyltrifluoroborate and 1,3-dipyridyl-5-bromobenzene to give 4
in 63% yield (84% based on recovered materials, entry 2). The
starting material 3 was prepared via a one-step Stille coupling
reaction between 1,3,5-tribromobenzene with tributyl(2-pyri-
dyl)stannane according to a reported procedure.21 Ligand 6,
with a phenyl linker between the tpy unit and vinyl substituent, was
synthesized in high yield from substrate 5 (entry 3), which was
obtained from one-step condensation of 2-acetylpyridine with 4-bro-
mobenzaldehyde in the presence of KOH and aqueous ammonia.22
However, the reaction of substrate 7, 4-(p-bromophenyl)-2,20-
bipyridine,23 with potassium vinyltrifluoroborate only gave 8 in
moderate yield (53%, entry 4).
5,50-Dibromo-2,20-bipyridine (9) and 5-bromo-2,20-bipyri-
dine (11) could be readily prepared from the bromination of
2,20-bipyridine hydrobromide salt.24 These two substrates are
widely used for the synthesis of 2,20-bipyridine derivatives with
substituents at the 5 and 50 positions.25 We found that the
vinylation of 9 and 11 proceeded smoothly under the same
conditions described above, giving 5,50-divinyl-2,20-bipyridine
(10) and 5-vinyl-2,20-bipyridine (12), respectively, in high yields
(entries 5 and 6). It should be noted that the synthesis of 5-vinyl-
2,20-bipyridine has recently been disclosed via Wittig reaction of
5-formyl-2,20-bipyridine.26 However, a tedious five-step proce-
dure for the synthesis of 5-formyl-2,20-bipyridine is necessary.
Next, we turned our attention to the vinylation of 4,40-dibromo-
2,20-bipyridine (13) and 4-bromo-2,20-bipyridine (16). These two
substrates were prepared from 2,20-bipyridine via straightforward
four-step procedures,27 and only the final step products needed
purification through flash column chromatography. The reaction
of 13 with 3 equiv of potassium vinyltrifluoroborate in 24 h
afforded monovinylated compound 15 as the main product (68%
yield, entry 8). Ontheother hand, 4,40-divinyl-2,20-bipyridine (14)
could be dominantly produced by increasing the amount of
potassium vinyltrifluoroborate to 4 equiv and prolonging the
reaction time to 4 h (70% yield, entry 7). It should also be noted
that 4,40-divinyl-2,20-bipyridine was previously prepared in 12%
overall yield from 4,40-dimethyl-2,20-bipyridine via a five-step
reaction sequence,28 and this procedure was later modified by
Bernhard and co-workers.13 In comparison, our method would
allow simpler, cheaper, and more practical preparation of 4,40-
divinyl-2,20-bipyridine. Finally, 4-vinyl-2,20-bipyridine (17) was
also obtained in good yield (entry 9).
a Conditions: bromide (1 equiv), potassium vinyltrifluoroborate (1.2 ꢀ
2.0 equiv), Pd(OAc)2 (2 mol %), PPh3 (6 mol %), Cs2CO3 (3 equiv) in a
mixture of THF/H2O, reflux for 48 h. b With 4 equiv of potassium
vinyltrifluoroborate. c With 3 equiv of potassium vinyltrifluoroborate
and reflux for 24 h.
The reductive electropolymerization of transition-metal 2,20-
bipyridine complexes with vinyl substituents on the 4 and 40
positions of the ligand is well established.2ꢀ4 However, the use of
5,50-divinyl-2,20-bipyridine in this area has remained unexplored.
As described above, 5,50-divinyl-2,20-bipyridine can be obtained
in a simple way. We decided to study the possibility of using this
ligand in reductive electropolymerization. Complex 18,
[Ru(5,50-divinyl-2,20-bipyridine)3](PF6)2, was prepared from
5,50-divinyl-2,20-bipyridine in 65% yield (Scheme 1). When a
Pt electrode was placed in an acetonitrile solution of 18 contain-
ing 0.1 M Bu4NClO4 and the potential was scanned repeatedly
between ꢀ0.8 and ꢀ1.6 V vs Ag/AgCl, the cyclic voltammetric
(CV) waves in this region grew gradually and continually. This
indicates that a smooth reductive electropolymerization of 18
took place and a polymerized film deposited on the surface of the
electrode. The CV profile of this film was recorded (Figure 1b) after
the above Pt electrode was rinsed with acetonitrile and transferred
to a clean supporting electrolyte solution. The metal-associated
polypyridines are readily accessible. This method would provide
a general approach to vinyl-substituted polypyridines with struc-
tural diversities. The experimental results are summarized in
Table 1. The vinylation of 40-bromoterpyridine is the first
substrate we attempted. Gratifyingly, the reaction of 1.2 equiv
of potassium vinyltrifluoroborate with 40-bromoterpyridine (1)
in the presence of 2 mol % of Pd(OAc)2, 6 mol % of PPh3, and 3
equiv of Cs2CO3 afforded vtpy (2) in high yield (89%, entry 1).
40-Bromoterpyridine is commercially available or could be pre-
pared by a straightforward known procedure.19 Recently, we and
others have been interested in the studies of cyclometalated
polypyridyl complexes.20 Thus, the synthesis of a potential vinyl-
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NOTE
Scheme 1. Synthesis of Complex 18
prove that this complex could undergo reductive electropolymer-
ization smoothly. Further results on the electropolymerization
processes of complexes with 5,50-divinyl-2,20-bipyridine ligands
and the nature of resulting films will be reported in due course.
’ EXPERIMENTAL SECTION
Synthesis of vtpy (2). A suspension of 40-bromoterpyridine 1
(100 mg, 0.32 mmol), potassium vinyltrifluoroborate (52 mg, 0.38
mmol, 1.2 equiv), Pd(OAc)2 (1.5 mg, 0.0064 mmol), PPh3 (5 mg, 0.02
mmol), and Cs2CO3 (313 mg, 0.96 mmol) in THF/H2O (24/1) (5 mL)
was heated at 85 °C under a N2 atmosphere in a sealed tube. After 48 h,
the reaction mixture was cooled to room temperature and diluted with
5 mL of H2O, followed by extraction with CH2Cl2 (20 mL ꢁ 3). The
organic phases were combined and washed with brine and dried with
Na2SO4. The solvent was removed under reduced pressure, and the
crude product was purified by silica gel chromatography (eluting with
65:65:1 petroleum ether/dichloromethane/NH4OH) to yield 2 as a
white solid (80 mg, 89%). 1H NMR (400 MHz, CDCl3): δ 5.58 (d, J =
10.9 Hz, 1H), 6.24 (d, J = 17.6 Hz, 1H), 6.88 (dd, J = 17.6, 10.8 Hz, 1H),
7.34 (dd, J = 7.3, 4.9 Hz, 2H), 7.88 (t, J = 7.7 Hz, 2H), 8.48 (s, 2H), 8.64
(d, J = 7.9 Hz, 2H), 8.73 (d, J = 4.6 Hz, 2H). 13C NMR (100 MHz,
CDCl3): δ 156.0, 155.6, 148.9, 146.7, 136.7, 135.1, 123.7, 121.2, 118.8,
118.0. EI-HRMS: calcd for C17H13N3 259.1109, found 259.1113.
Synthesis of Compound 4. A suspension of potassium vinyltri-
fluoroborate (58 mg, 0.43 mmol), 1,3-dipyridyl-5-bromobenzene (3)
(88 mg, 0.29 mmol), Pd(OAc)2 (1.3 mg, 0.0057 mmol), PPh3 (4.5 mg,
0.017 mmol), and Cs2CO3 (280 mg, 0.86 mmol) in THF/H2O (24:1, a
total of 5 mL) was heated for 48 h at 85 °C in a sealed tube. Then the
system was cooled to room temperature and diluted with H2O (5 mL),
followed by extraction with CH2Cl2 (20 mL ꢁ 3). The organic phases
were combined and washed with brine and dried over Na2SO4. The
solvent was removed under vacuum, and the crude product was purified
by silica gel chromatography (eluting with 50:1 dichloromethane/ethyl
acetate) to yield 46 mg of 4 as a white solid (63%, 84% based on
recovered material). 1H NMR (400 MHz, CDCl3): δ 5.36 (d, J = 10.9
Hz, 1H), 5.96 (d, J = 17.6 Hz, 1H), 6.89 (dd, J = 17.6, 10.8 Hz, 1H), 7.26
(t, J = 6.1 Hz, 2H), 7.78 (t, J = 7.7 Hz, 2H), 7.85 (d, J = 7.9 Hz, 2H), 8,12
(s, 2H), 8.48 (s, 1H), 8.73 (d, J = 4.6 Hz, 2H). 13C NMR (100 MHz,
CDCl3): δ 157.0, 149.6, 140.1, 136.7, 136.6, 125.3, 124.9, 122.3, 120.8,
114.8. EI-HRMS: calcd for C18H14N2 258.1157, found 258.1160.
Synthesis of Compound 6. A suspension of potassium vinyltri-
fluoroborate (42 mg, 0.31 mmol), 4-(4-bromophenyl)-2,6-di(pyridin-2-yl)
pyridine (5) (100 mg, 0.26 mmol), Pd(OAc)2 (1.2 mg, 0.0052 mmol),
PPh3 (4 mg, 0.015 mmol), and Cs2CO3 (252 mg, 0.77 mmol) in THF/
H2O (24:1, a total of 5 mL) was heated for 48 h at 85 °C in a sealed tube.
Then the system was cooled to room temperature and diluted with H2O
(5 mL), followed by extraction with CH2Cl2 (20 mL ꢁ 3). The organic
phases were combined and extracted with aqueous saturated NaCl
(50 mL) and dried over Na2SO4. The solvent was removed under
vacuum and the crude product was purified by silica gel chromatography
(eluting with 35:50:1 petroleum ether/dichloromethane/NH4OH) to
Figure 1. (a) Reductive electropolymerization of 18 on a Pt electrode
by 15 cyclic potential scans at 100 mV/s between ꢀ0.8 and ꢀ1.6 V vs
Ag/AgCl in 0.1 M Bu4NClO4/CH3CN. The concentration of 18 is
0.5 mM. (b) Cyclic voltammetry of above electrode at 100 mV/s in clean
0.1 M Bu4NClO4/CH3CN.
oxidation wave and ligand-based reduction waves remain ob-
servable. However, the former is somewhat reminiscent of a
diffusion-controlled process, and well-defined ligand-based re-
duction waves are not evident. We are currently carrying out a
more detailed study of the nature of this film and exploring the
usage of 5,50-divinyl-2,20-bipyridine in electropolymerization of
other transition-metal complexes.
In conclusion, this paper describes a successful SuzukiꢀMiyauru
cross-coupling of bromopolypyridines with potassium vinyltri-
fluoroborate, which affords numerous vinyl-substituted polypyridyl
ligands in moderate to good yields. This reaction represents a simple
and practical synthetic procedure for a number of known vinyl-
substituted polypyridines, such as 40-vinyl-2,20:60,200-terpyridine,
5,50-divinyl-2,20-bipyridine, and 4,40-divinyl-2,20-bipyridine. The
use of these ligands for the preparation of redox-active and
photofunctional metallopolymers is well established. We trust
that this improved procedure will further boost the chemistry of
metallopolymers and expand the application of vinyl-substituted
polypyridine ligands and complexes in other fields. Preliminary
electrochemical studies of [Ru(5,50-divinyl-2,20-bipyridine)3]2þ
1
yield 80 mg of 6 as a pale yellow solid (93%). H NMR (400 MHz,
CDCl3): δ 5.35 (d, J = 10.9 Hz, 1H), 5.86 (d, J = 17.6 Hz, 1H), 6.79 (dd,
J = 17.6, 10.8 Hz, 1H), 7.36 (t, J = 6.1 Hz, 2H), 7.55 (d, J = 8.0 Hz, 2H),
7.89 (m, overlapping, 4H), 8.68 (d, J = 8.0 Hz, 2H), 8.74 (d, J = 6.5 Hz,
2H), 8.75 (s, 2H). 13C NMR (100 MHz, CDCl3): δ 156.1, 155.8, 149.5,
149.0, 138.2, 137.6, 136.7, 136.2, 127.4, 126.7, 123.7, 121.3, 118.5, 114.7.
EI-HRMS: calcd for C23H17N3 335.1422, found 335.1427.
Synthesis of Compound 8. A suspension of potassium vinyltri-
fluoroborate (36 mg, 0.27 mmol), 4-(p-bromophenyl)-2,20-bipyridine (7)
(70 mg, 0.23 mmol), Pd(OAc)2 (1.0 mg, 0.0045 mmol), PPh3 (3.5 mg,
0.014 mmol), and Cs2CO3 (220 mg, 0.67 mmol) in THF/H2O (24:1, a
total of 5 mL) was heated at 85 °C for 48 h under a N2 atmosphere. Then
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NOTE
the solution was cooled to room temperature and diluted with 5 mL of H2O,
followed by extraction with CH2Cl2 (20 mL ꢁ 3). The organic phases were
combined and extracted with aqueous saturated NaCl (50 mL) and dried
over Na2SO4. The solvent was removed under vacuum and the crude
product was purified by silica gel chromatography (eluting with 100:50:1
petroleum ether/ethyl acetate/NH4OH) to yield 31 mg of 8 as a yellow
solid (53%). 1H NMR (400 MHz, CDCl3): δ 5.34 (d, J = 10.9 Hz, 1H), 5.85
(d, J=17.6 Hz, 1H), 6.78 (dd, J=17.6, 10.8 Hz, 1H), 7.34 (t, J=6.0 Hz, 1H),
7.54 (m, overlapping, 3H), 7.76 (d, J = 7.8 Hz, 2H), 7.85 (t, J = 7.7 Hz, 1H),
8.46 (d, J = 8.0 Hz, 1H), 8.69 (s, 1H), 8.72 (d, J = 4.6 Hz, 2H). 13C NMR
(100 MHz, CDCl3): δ 156.3, 155.8, 149.7, 149.2, 149.0, 138.4, 137.3, 137.1,
136.1, 127.3, 126.9, 124.0, 121.5, 121.3, 118.7, 114.9. EI-HRMS: calcd for
C18H14N2 258.1157, found: 258.1160.
(50 mg, 0.16 mmol), Pd(OAc)2 (0.7 mg, 0.0032 mmol), PPh3 (2.5 mg,
0.01 mmol), and Cs2CO3 (155 mg, 0.48 mmol) in THF/H2O (24:1, a
total of 5 mL) was heated at 85 °C for 48 h under an N2 atmosphere in a
sealed tube. The system was then cooled to room temperature and
diluted with H2O (5 mL), followed by extraction with CH2Cl2 (20 mL
ꢁ 3). The organic phases were combined and extracted with saturated
NaCl (50 mL) and dried over Na2SO4. The solvent was removed under
vacuum, and the crude product was purified by silica gel chromatography
(eluting with 50:1 petroleum ether/ethyl acetate) to yield 29 mg of 15 as
a white solid (68%). 1H NMR (400 MHz, CDCl3): δ 5.55 (d, J = 10.8
Hz, 1H), 6.10 (d, J = 17.6 Hz, 1H), 6.77 (dd, J = 17.6, 10.8 Hz, 1H), 7.34
(d, J = 7.0 Hz, 1H), 7.49 (d, J = 5.2 Hz, 1H), 8.39 (s, 1H), 8.50 (d, J = 5.2
Hz, 1H), 8.63 (d, J = 2.8 Hz, 1H), 8.64 (s, 1H). 13C NMR (100 MHz,
CDCl3): δ 157.3, 155.1, 149.7, 149.5, 146.0, 134.7, 134.0, 126.9, 124.8,
121.3, 118.6, 118.5. EI-HRMS: calcd for C12H9N279Br 259.9949, found
259.9952; calcd for C12H9N280Br 261.9929, found 261.9932.
Synthesis of Compound 17. A suspension of potassium vinyltri-
fluoroborate (49 mg, 0.36 mmol), 4-bromo-2,20-bipyridine (16) (57 mg,
0.24 mmol), Pd(OAc)2 (1.1 mg, 0.0048 mmol), PPh3 (3.8 mg, 0.014
mmol), and Cs2CO3 (236 mg, 0.72 mmol) in THF/H2O (24:1, a total of
5 mL) was heated at 85 °C for 48 h under an N2 atmosphere in a sealed
tube. The system was then cooled to room temperature and diluted with
5 mL of H2O, followed by extraction with CH2Cl2 (20 mL ꢁ 3). The
organic phases were combined and washed with brine and dried over
Na2SO4. The solvent was removed under vacuum, and the crude product
was purified by flash chromatography on silica gel (eluting with 50:1
petroleum ether/ethyl acetate) to yield 39 mg of 17 as a pale yellow solid
(89%). 1H NMR (400 MHz, CDCl3): δ 5.51 (d, J = 10.9 Hz, 1H), 6.09 (d,
J = 17.6 Hz, 1H), 6.74 (dd, J = 17.6, 10.8 Hz, 1H), 7.30 (m, overlapping,
2H), 7.81 (t, J = 7.7 Hz, 1H), 8.40 (d, J = 4.8 Hz, 1H), 8.41 (s, 1H), 8.61
(d, J=5.1 Hz, 1H), 8.68 (d, J= 4.6 Hz, 1H). 13C NMR (100 MHz, CDCl3):
δ 156.5, 156.1, 149.5, 149.1, 145.8, 136.9, 134.9, 123.7, 121.2, 120.6, 118.8,
118.3. EI-HRMS: calcd for C12H10N2 182.0844, found 182.0846.
Synthesis of Compound 10. A suspension of potassium vinyltri-
fluoroborate (170 mg, 1.27 mmol), 5,50-dibromo-2,20-bipyridine (9)
(100 mg, 0.32 mmol), Pd(OAc)2 (1.4 mg, 0.0064 mmol), PPh3 (5 mg,
0.02 mmol), and Cs2CO3 (311 mg, 0.96 mmol) in THF/H2O (24:1, a
total of 5 mL) was heated at 85 °C for 48 h under an N2 atmosphere in a
sealed tube. The system was then cooled to room temperature and diluted
with H2O (5 mL), followed by extraction with CH2Cl2 (20 mL ꢁ 3).
The organic phases were combined and extracted with aqueous saturated
NaCl (50 mL), and dried over Na2SO4. The solvent was removed under
vacuum, and the crude product was purified by silica gel chromatography
(eluting with 35:50:1 petroleum ether/dichloromethane/NH4OH) to
yield 61 mgof10asa yellow solid (93%). 1H NMR (400 MHz, CDCl3): δ
5.42 (d, J = 11.0 Hz, 2H), 5.89 (d, J = 17.6 Hz, 2H), 6.77 (dd, J = 17.6, 10.8
Hz, 2H), 7.87 (d, J = 8.2 Hz, 2H), 8.37 (d, J = 8.3 Hz, 2H), 8.67 (s, 2H).
13C NMR (100 MHz, CDCl3): δ 155.0, 147.8, 133.5, 133.4, 133.3, 120.7,
116.3. EI-HRMS: calcd for C14H12N2 208.1000, found 208.1003.
Synthesis of Compound 12. A suspension of potassium vinyltri-
fluoroborate (114 mg, 0.85 mmol), 5-bromo-2,20-bipyridine (11) (100 mg,
0.43 mmol), Pd(OAc)2 (1.9 mg, 0.0085 mmol), PPh3 (7 mg, 0.03
mmol), and Cs2CO3 (416 mg, 1.28 mmol) in THF/H2O (24:1, a total of
5 mL) was heated at 85 °C for 48 h under a N2 atmosphere in a sealed
tube. The system was then cooled to room temperature and diluted with
5 mL of H2O, followed by extraction with CH2Cl2 (20 mL ꢁ 3). The
organic phases were combined and extracted with aqueous saturated
NaCl and dried over Na2SO4. The solvent was removed under vacuum,
and the crude product was purified by silica gel chromatography (eluting
with 50:1 petroleum ether/ethyl acetate) to yield 66 mg of 12 as a pale
yellowsolid. Theyield is 85%. 1H NMR (400 MHz, CDCl3): δ5.41(d, J =
11.0 Hz, 1H), 5.89 (d, J = 17.6 Hz, 1H), 6.76 (dd, J = 17.6, 10.8 Hz, 1H),
7.30 (t, J = 7.2 Hz, 1H), 7.80 (t, J = 7.6 Hz, 1H), 7.87 (d, J = 8.3 Hz, 1H),
8.38 (t, J = 7.9 Hz, 2H), 8.68 (s, 2H). 13C NMR (100 MHz, CDCl3): δ
155.8, 155.3, 149.2, 147.7, 136.8, 133.4, 133.3, 133.0, 123.6, 121.0, 120.8,
116.3. EI-HRMS: calcd for C12H10N2 182.0844, found 182.0846.
Synthesis of Compound 14. A suspension of potassium vinyltri-
fluoroborate (341 mg, 2.55 mmol), 4,40-dibromo-2,20-bipyridine (13)
(200 mg, 0.64 mmol), Pd(OAc)2 (2.9 mg, 0.013 mmol), PPh3 (10 mg,
0.038 mmol), and Cs2CO3 (623 mg, 1.91 mmol) in THF/H2O (24:1, a
total of 10 mL) was heated at 85 °C for 48 h under an N2 atmosphere in a
sealed tube. The system was then cooled to room temperature and diluted
with H2O (10 mL), followed by extraction with CH2Cl2 (50 mL ꢁ 3).
The organic phases were combined and extracted with aqueous saturated
NaCl and dried over Na2SO4. The solvent was removed under vacuum,
and the crude product was purified by silica gel chromatography (eluting
with 50:1 petroleum ether/ethyl acetate) to yield 94 mg of 14 as a pale
yellow solid (70%). 1H NMR (400 MHz, CDCl3): δ 5.54 (d, J = 10.8 Hz,
2H), 6.10(d, J =17.6 Hz, 2H), 6.77(dd, J =17.6, 10.8Hz, 2H), 7.33 (d, J=
5.0 Hz, 2H), 8.40 (s, 2H), 8.64 (d, J = 5.0 Hz, 2H). 13C NMR (100 MHz,
CDCl3): δ 156.4, 149.4, 145.8, 134.9, 120.7, 118.9, 118.4. EI-HRMS:
calcd for C14H12N2 208.1000, found 208.1003.
Synthesis of Complex 18. To a mixed solvent of 10 mL of ethanol
and 5 mL of water were added RuCl3 3H2O (16 mg, 0.06 mmol) and
3
5,50-divinyl-2,20-bipyridine (39 mg, 0.18 mmol). The mixture was stirred
and refluxed for 24 h under a N2 atmosphere. After the mixture was
cooled to room temperature, ethanol was removed under reduced
pressure, followed by the addition of an excess of KPF6. The resulting
precipitate was collected by filtering and washing with water and Et2O.
The obtained solid was subject to flash column chromatography on silica
gel (eluent: saturated aq. KNO3/water/acetonitrile, 1/10/400) to give 40
mg of 18 in a yield of 65%. 1H NMR (400 MHz, CD3CN): δ 5.46 (d, J =
11.0 Hz, 6H), 5.85 (d, J = 17.7 Hz, 6H), 6.55 (dd, J = 17.7, 11.0 Hz, 6H),
7.62 (s, 6H), 8.16 (d, J = 8.5 Hz, 6H), 8.41 (d, J = 8.6 Hz, 6H). 13C NMR
(100 MHz, CD3CN): δ 155.6, 150.2, 136.5, 134.5, 131.4, 124.1, 119.7.
MALDI-MS: 870.4 for [M ꢀ PF6]þ, 726.3 for [M ꢀ 2PF6]2þ. ESI-
HRMS: calcd for C42H36N6Ru1 726.2050, found 726.2051.
’ ASSOCIATED CONTENT
S
Supporting Information. NMR and MS spectra of vinyl-
b
substituted polypyridines and complex 18. This material is
available free of charge via the Internet at http://pubs.acs.org.
’ AUTHOR INFORMATION
Corresponding Author
*E-mail: zhongyuwu@iccas.ac.cn.
’ ACKNOWLEDGMENT
Funding support from the 973 program (2011CB932301),
National Natural Science Foundation of China (No. 21002104),
Synthesis of Compound 15. A suspension of potassium vinyltri-
fluoroborate (64 mg, 0.48 mmol), 4,40-dibromo-2,20-bipyridine (13)
4774
dx.doi.org/10.1021/jo200590r |J. Org. Chem. 2011, 76, 4771–4775

The Journal of Organic Chemistry
NOTE
and Institute of Chemistry, Chinese Academy of Sciences (“100
Talent” Program) are greatly appreciated. We thank Chang-Jiang
Yao, Jing Wu, and Hong-Wei Kang in the same group for
preparing the starting materials 3, 9, and 13, respectively.
Am. Chem. Soc. 2002, 124, 14162. (c) Bair, J. S.; Harrison, R. G. J. Org.
Chem. 2007, 72, 6653.
(28) Ciana, L. D.; Dressick, W. J.; von Zelewsky, A. J. Heterocycl.
Chem. 1990, 27, 163.
’ REFERENCES
(1) (a) Schultze, X.; Serin, J.; Adronov, A.; Frꢀechet, J. M. J. Chem.
Commun. 2001, 1160. (b) Okeyoshi, K.; Yoshida, R. Chem. Commun.
2009, 6400.
(2) Abru~na, H. D. Coord. Chem. Rev. 1988, 86, 135.
(3) Denisevich, P.; Abru~na, H. D.; Leidner, C. R.; Meyer, T. J.;
Murray, R. W. Inorg. Chem. 1982, 21, 2153.
(4) Nallas, G. N. A.; Brewer, K. J. Inorg. Chim. Acta 1997, 257, 27.
(5) Potts, K. T.; Usifer, D. A.; Guadalupe, A. R.; Abru~na, H. D. J. Am.
Chem. Soc. 1987, 109, 3961.
(6) Guadalupe, A. R.; Usifer, D. A.; Potts, K. T.; Hurrell, H. C.;
Mogstad, A.-E.; Abru~na, H. D. J. Am. Chem. Soc. 1988, 110, 3462.
(7) Elliott, C. M.; Dunkle, J. R.; Paulson, S. C. Langmuir 2005,
21, 8605.
(8) Moss, J. A.; Leasure, R. M.; Meyer, T. J. Inorg. Chem. 2000,
39, 1052.
(9) Abru~na, H. D.; Bard, A. J. J. Am. Chem. Soc. 1982, 104, 2641.
(10) Leasure, R. M.; Ou, W.; Moss, J. A.; Linton, R. W.; Meyer, T. J.
Chem. Mater. 1996, 8, 264.
(11) Abru~na, H. D.; Denisevich, P.; Uma~na, M.; Meyer, T. J.;
Murray, R. W. J. Am. Chem. Soc. 1981, 103, 1.
(12) Moss, J. A.; Yang, J. C.; Stipkala, J. M.; Wen, X.; Bignozzi, C. A.;
Meyer, G. J.; Meyer, T. J. Inorg. Chem. 2004, 43, 1784.
(13) Metz, S.; Bernhard, S. Chem. Commun. 2010, 46, 7551.
(14) Potts, K. T.; Konwar, D. J. Org. Chem. 1991, 56, 4815.
(15) (a) Ghosh, P. K.; Spiro, T. G. J. Am. Chem. Soc. 1980, 102, 5543.
(b) Abru~na, H. D.; Breikss, A. I.; Collum, D. B. Inorg. Chem. 1985,
24, 987.
(16) Williams, C. E.; Lowry, R. B.; Braven, J.; Belt, S. T. Inorg. Chim.
Acta 2001, 315, 112.
(17) Joucla, L.; Cusati, G.; Pinel, C.; Djakovitch, L. Appl. Catal. A
2009, 360, 145.
(18) (a) Molander, G. A.; Brown, A. R. J. Org. Chem. 2006, 71, 9681.
(b) Molander, G. A.; Rivero, M. R. Org. Lett. 2002, 4, 107. (c) Molander,
G. A.; Ellis, N. Acc. Chem. Res. 2007, 40, 275.
(19) Carlson, B.; Phelan, G. D.; Kaminsky, W.; Dalton, L.; Jiang, X.;
Liu, S.; Jen, A. K.-Y. J. Am. Chem. Soc. 2002, 124, 14162.
(20) (a) J€ager, M.; Smeigh, A.; Lombeck, F.; G€orls, H.; Collin, J.-P.;
Sauvage, J.-P.; Hammarstr€om, L.; Johansson, O. Inorg. Chem. 2010,
49, 374. (b) Bomben, P. G.; Koivisto, B. D.; Berlinguette, C. P. Inorg.
Chem. 2010, 49, 4960. (c) Zhong, Y.-W.; Wu, S.-H.; Burkhardt, S. E.;
Yao, C.-J.; Abru~na, H. D. Inorg. Chem. 2011, 50, 517. (d) Yao, C.-J.; Sui,
L.-Z.; Xie, H.-Y.; Xiao, W.-J.; Zhong, Y.-W.; Yao, J. Inorg. Chem. 2010,
49, 8347.
(21) Farley, S. J.; Rochester, D. L.; Thompson, A. L.; Howard,
J. A. K.; Williams, J. A. G. Inorg. Chem. 2005, 44, 9690.
(22) Wang, J.; Hanan, G. S. Synlett 2005, 1251.
(23) (a) Querol, M.; Bozic, B.; Salluce, N.; Belser, P. Polyhedron
2003, 22, 655. (b) Montalti, M.; Wadhwa, S.; Kim, W. Y.; Kipp, R. A.;
Schmehl, R. H. Inorg. Chem. 2000, 39, 76.
(24) (a) Romero, F. M.; Ziessel, R. Tetrahedron Lett. 1995, 36, 6471.
(b) Zdravkov, A. B.; Khimich, N. N. Russ. J. Org. Chem. 2006, 42, 1200.
(25) (a) Grosshenny, V.; Romero, F. M.; Ziessel, R. J. Org. Chem.
1997, 62, 1491. (b) He, F.; Zhou, Y.; Liu, S.; Tian, L.; Xu, H.; Zhang, H.;
Yang, B.; Dong, Q.; Tian, W.; Ma, Y.; Shen, J. Chem. Commun.
2008, 3912.
(26) Li, G.-N.; Wen, D.; Jin, T.; Liao, Y.; Zuo, J.-L.; You, X.-Z.
Tetrahedron Lett. 2011, 52, 675.
(27) (a) Staats, H.; Eggers, F.; Hab, O.; Fahrenkrug, F.; Matthey, J.;
L€uning, U.; L€utzen, A. Eur. J. Org. Chem. 2009, 4777. (b) Carlson, B.;
Phelan, G. D.; Kaminsky, W.; Dalton, L.; Jiang, X.; Liu, S.; Jen, A. K.-Y. J.
4775
dx.doi.org/10.1021/jo200590r |J. Org. Chem. 2011, 76, 4771–4775