5,5″-disubstituted 2,2′:6′,2″-terpyridines through and for metal-mediated cross-coupling chemistry

Article abstract of DOI:10.1002/(SICI)1521-3765(19990301)5:3<854::AID-CHEM854>3.0.CO;2-8

The 0.3-5 g scale syntheses of the 2,2′:6′,2″-terpyridines 3, 6, 9, and 10 are described. The pyridine units are connected to one another by Pd-catalyzed cross-coupling reactions. This method allows the easy introduction of halogen, stannyl, and boronic ester functionalities at positions C-5 and C-5″; this results in a novel functionality pattern for terpyridines that considerably widens the applicability of this class of tridentate ligands for supra- and macromolecular applications. The feasibility of growth reactions with these novel terpyridines was demonstrated by the synthesis of compounds 12a-c.

Full text of DOI:10.1002/(SICI)1521-3765(19990301)5:3<854::AID-CHEM854>3.0.CO;2-8

FULL PAPER
5,5''-Disubstituted 2,2':6',2''-Terpyridines through and for Metal-Mediated
Cross-Coupling Chemistry
Uwe Lehmann, Oliver Henze, and A. Dieter Schlüter*[a]
Abstract: The 0.3 ± 5 g scale syntheses of the 2,2':6',2''-terpyridines 3, 6, 9, and 10 are
described. The pyridine units are connected to one another by Pd-catalyzed cross-
coupling reactions. This method allows the easy introduction of halogen, stannyl, and
boronic ester functionalities at positions C-5 and C-5''; this results in a novel
functionality pattern for terpyridines that considerably widens the applicability of this
class of tridentate ligands for supra- and macromolecular applications. The feasibility
of growth reactions with these novel terpyridines was demonstrated by the synthesis
of compounds 12a ± c.
Keywords: cross-coupling ´ modu-
lar chemistry
´
supramolecular
chemistry ´ terpyridines
cross-coupling reactions,[5] b) to open up the possibility to
construct a variety of differently sized rings, c) to allow for
optimum complexation with transition metals, d) to be soluble
also when integrated into larger structures, and (e) to have the
potential to decorate the targeted rings in their periphery with
some relevant groups. To meet these criteria the following
measures seemed appropriate: For a) dihalo, distannyl (in
situ), and diboronic functionalities, for b) and c) attachment of
these functionalities at C-5 and C-5'', for d) flexible chains at
C-4',[6] and for e) the selection of such chains at C-4' that allow
them to be used as anchor groups after modification (depro-
tection).
The incorporation of the coupling functionalities at C-5 and
C-5'' (point b and c) should be addressed because of the many
terpyridines known,[7] those with a C-5, C-5'' substitution
pattern are the least common ones. Additionally, neither of
the present functionality patterns has ever been realized at
these positions. Two important reasons, nevertheless, led us to
undertake the considerable synthetic effort: First, to allow for
a variable linear extension of the two outer pyridine units of
the terpyridine into what later will become the side of an
hexagonal cycle, and, second, to account for the observation[8]
that complexation of terminally substituted terpyridines in
some cases proceed better if their substitutents are at C-5 and
C-5'' and not at C-6 and C-6''.[9]
Introduction
We have recently reported on repetitive syntheses of oligo-
phenylene hexagons with up to 24[1] phenylene rings that
make these compounds available at a reasonable quantity/
effort relationship. The main motivation for this research is
a) to approach extended honeycomblike, two-dimensional
networks for which these shape persistent, geometrically
regular molecules may serve as constituents,[2] and b) to apply
the developed methodology to the synthesis of shape-
persistent macrocycles with integral donor moieties like
2,2':6',2''-terpyridine for subsequent transition metal complex-
ation and supramolecular assembly.[3] The present contribu-
tion describes the synthesis of a number of terpyridine
building blocks that carry chloro-, bromo-, trimethylstannyl-
(in situ), and boronic acid ester functions at C-5 and C-5'' and
some of them hexoxymethyl or methoxy(ethoxy)methoxy-
methyl [(MEM)OCH2] substituents at C-4'. Some further
growth reactions with these terpyridines that lead to imme-
diate starting materials for ring closure reactions are also
reported.
Results and Discussion
Terpyridines to be used for the outlined project need a) to be
functionalized in a way that they can be used as building
blocks in Stille[4] and Suzuki-type transition metal catalyzed
The synthetic routes are summarized in Schemes 1 ± 4.
Scheme 1 describes the syntheses of the central dibromo
pyridines 1e and 1 f and the coupling of 1a and 1e with the tin
component 2b to give dichloroterpyridines 3a and 3e.
Scheme 2 describes the opposite approach, which involves
the synthesis of the central pyridine unit 4a, e, and f with two
trimethyltin (TMSn) groups (4e and 4 f in situ) and their
coupling with bromochloropyridine 2a (done for 4a only) to
[a] Prof. Dr. A. D. Schlüter, Dipl.-Chem. U. Lehmann, Dipl.-Chem. O. Henze
Freie Universität Berlin, Institut für Organische Chemie
Takustr. 3, D-14195 Berlin (Germany)
Fax : (‡ 49)30-838-3357
E-mail: adschlue@chemie.fu-berlin.de
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Chem. Eur. J. 1999, 5, No. 3

854±859
Scheme 1. a) LAH, THF, 208C, 58.1%; b) TfOTf, NEt3, CH2Cl2, 08C,
then: C6H13OH, 208C, 78.7%; c) MEMCl, N(iPr)2Et, CH2Cl2, 208C,
69.9%; d) BuLi, Me3SnCl, 788C, Et2O, 47.7%; e) Pd(PPh3)4, toluene,
reflux, 3a: 65.1%, 3e: 68.6%.
Scheme 2. a) NaSnMe3, 08C, DME; b) Pd(PPh3)4, toluene, reflux, 44.4%;
c) Pd(PPh3)4, toluene, reflux, 6a: 26.5%, 6e: 13.8%, 6 f: 26.4%.
more accurately 15.5 ± 26.4% for the two steps from the
corresponding pyridines 1. The coupling of 4e with 5 was
difficult to reproduce for unknown reasons. In the worst case,
the yield of the corresponding terpyridine 6e is only 8%. It
could nevertheless be obtained in amounts of 150 ± 300 mg per
run. Terpyridines 6a and 6 f were obtained on the 2.5 ± 5 g
scale. A reason for the moderate coupling yields may be the
occurance of some homocoupling of 5. This took place at C-2
and gave 5,5'-dibromo-2,2'-bipyridine (see below).
The proposed regiochemical course of the coupling of 4e
and 5 (with its two bromo functions) was verified by a control
experiment to make sure that the terpyridine obtained had
the proposed 2,2':6',2'' and not 3,2':6',3'' connectivity. Pyridine
4e was coupled with compound 7,[19] which should have a
much higher reactivity at C-2 than 5. The only isolable
product was identical with the one obtained in the above
reaction. Though its yield was only 8%, this finding never-
theless establishes the proposed structure of 6e. Additional
evidence comes from NMR heternuclear correlation experi-
ments with 6 f in which the coupling between H-3' and C-2 can
be unequivocally established. For a related experiment also
supporting the proposed structure, see compound 12c.
Kumada-type coupling reactions of 5 also proceeded at C-2.[20]
The coupling of 4a with 8 (Scheme 3) uses the fact that
boronic esters (apart from boronic acids[21]) do not get
involved into cross-couplings under Stille conditions, because
no base is present that could saponify the ester. It proceeds
with higher yields (approx. 50%) than the couplings in
Scheme 2. The synthesis of compound 8 involves the known
regiospecific lithiation of 5 at C-5[22] followed by the standard
procedure for the introduction
give dichloroterpyridine 3a and with 2,5-dibromo pyridine 5
to give dibromoterpyridines 6a, e, and f. The sequence in
Scheme 3 also uses the distannyl pyridine 4a, but converts this
now into terpyridine 9 which carries two boronic acid ester
functions, and Scheme 4 provides an example in which two of
the novel terpyridines, 9 and 10, are used for further ex-
tension.
The syntheses of 1e and 1 f (Scheme 1) starts from 2,6-
dibromopyridine-4-carboxylic acid (1b)[10], which was esteri-
fied to give 1c[11], which in turn was reduced with LAH to
afford 1d.[12] Whereas the conversion of 1d into 1 f could
easily be achieved by normal protecting-group chemistry, the
conversion into 1e had to be done via the corresponding
triflate intermediate (not shown). The presence of free
alkoxide otherwise led to an effective competition for the
nucleophiles by the reactive C-2 position of 1d. The tin
component 2b, prepared by electrophilic stannylation via the
corresponding bromochloropyridine (2a), was lithiated at
C-2.[13, 14] The coupling between the central pyridines 1a and
1e and tin compound 2b was achieved by the normal Stille
procedure with 4 mol% of Pd[(PPh3)4].[15]
The central pyridines 4e and 4 f with two TMSn groups
were synthesized by nucleophilic stannylation (Scheme 2) in
analogy to the known synthesis of 4a.[16, 17] Except for 4a the
distannyls 4 were not isolated, but rather used in situ.[18] The
coupling of 4a with 2a to give 3a (method B, see Exper-
imental Section) proceeded in yields comparable with the
opposite reaction between 1a and 2b (method A) leading to
the same compound (Scheme 1). Judged by the overall
synthetic effort, the latter route (method A) is somewhat
more convenient. Dibromoterpyridines 6a, e, and f were
obtained by Stille coupling between 2,5-dibromopyridine (5)
and 4a, 4e, and 4 f, respectively; these reactions proceeded
with yields of 22.8 ± 32.6% from the stannyl compounds and
of boronic acid esters.[23]
Scheme 4 shows the in situ
synthesis of building block 10,
the linear extension of terpyr-
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855

A. D. Schlüter et al.
FULL PAPER
these couplings because it carries a flexible chain and two
functional groups with a known coupling selectivity (I ꢀ
Br).[25] Considering the respective synthetic effort associated
with these different routes to 12a, the coupling of 9 and 11 is
to be favored. For example,the total sequence via 9 requires
only one nucleophilic stannylation,[26] whereas that via 10
requires two. Furthermore compound 9 is an easy to
recrystallize solid, whereas 10 is prepared and used in situ.
The conversion of building block 12a into the others, 12b
and 12c, went smoothly either by nucleophilic stannylation or
nucleophlic stannylation followed by iododestannylation.
Compounds 12 are available in amounts of 3.2 g (12a), 2.5 g
(12b), and 1.2 g (12c). The TMSn group in 12b serves two
important functions, it can act as both a coupling functionality
and a place holder for iodide.
Some further comments may be useful:
a) All Stille-type couplings to terpyridines involving C-2-
substituted pyridines 2a, 5, and 8 were accompanied by some
homocoupling of the respective pyridines to give the corre-
sponding 2,2'-bipyridines. This unusual homocoupling, whose
mechanism is not yet clear, could be substantiated by experi-
ments in which compounds 2a, 5, and 8 were subjected to
coupling conditions without a coupling partner present. This
also led to the same homocoupling products.
Scheme 3. a) BuLi, B(O-iPr)3, Et2O, 788C, then: pinacole, dioxane,
45.6%; b) Pd(PPh3)4, toluene, reflux, 55%.
b) The stannyl compounds 2b, 4e, 4 f, and 10, in which the
TMSn group is located at a pyridine nucleus, cannot be
chromatographed through silica or alumina without at least
substantial decomposition. Compound 12b, however, which
carries stannyl at phenyl, can be easily purified this way
(alumina).
c) Whereas pyridine boronic ester 8 can be chromatograph-
ed, the diboronic ester tpy 9 decomposes on both silica and
alumina. Fortunately it could be recrystallized from toluene.
d) NMR heternuclear correlation experiments with com-
pound 12c proved the coupling between H-3 and C-2' as well
as H-3' and C-2 and thus establish the proposed regiochemical
course of the reaction between 4a and 5 (Scheme 2)
The terpyridine syntheses presented in this paper start from
properly substituted pyridines that are connected to one
another. In this regard our approach differs from the known
syntheses[7] in which the central pyridine is built-up during the
sequence by some condensation chemistry. The terminal
pyridines are usually introduced starting from 2-acetylpyr-
idines. In order to obtain the C-5, 5'' substitution pattern
described here, these aldehydes would have to have a halogen
function at C-5, which may be difficult to synthesize. In this
regard the present strategy widens the substitution patterns
available for terpyridines and complements to the known
syntheses.
Experimental
Scheme 4. a) Pd(PPh3)4, toluene, 1m Na2CO3, reflux, 41.1%; b) NaSnMe3,
DME, 08C; c) Pd(PPh3)4, toluene, reflux, 26.7%; d) NaSnMe3, DME, 08C,
61.4%; e) I2, CH2Cl2, 208C, 97.8%.
General: Compounds 1a and 5 were purchased from Aldrich or Acros.
Compounds 1c[11] and 1d[12] are known, but were prepared alternatively.
Compounds 1b,[10] 2a,[13] 4a,
and 11[24] were prepared according to the
[16]
literature. For compounds 2b and 7, see references [14] and [19]. All other
compounds are new.[26] NaSnMe3 was prepared according to the litera-
ture.[16] All other reagents were purchased from Aldrich or Acros and used
without further purification. All chromatographic separations were done
idines 9 and 10 with iodobenzene 11 to give the identical
product 12a, and, finally, the conversion of 12a into the new
building blocks 12b and 12c. Compound 11[24] was selected for
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Disubstituted Terpyridines
854±859
with methylene chloride as eluent if not otherwise stated. Prior to
combustion microanalysis, the terpyridines were dried in high vacuum at
208C for 6 h to avoid eventual problems with hydrate formation.
gel with CH2Cl2 to afford 42.3 g of 1c (75.4%) as a white solid, m.p. 88 ±
898C. 1H NMR (270 MHz, CDCl3): d ˆ 3.94 (s, 3H), 7.96 (s, 2H); 13C NMR
(68 MHz, CDCl3): d ˆ 53.29, 126.67, 141.42, 141.50, 162.94; MS (80 eV, EI):
‡
m/z (%): 297 (49.73), 295 (100.00), 294 (7.53) [M ], 266 (16.19), 264 (30.01),
5-Chloro-2-trimethylstannylpyridine (2b): BuLi (1.6m, 34 mL) in hexane
was added dropwise to a solution of 5-bromo-2-chloropyridine (2a; 10.0 g,
52.0 mmol) in Et2O (200 mL), while the temperature was kept at 788C.
After stirring at 788C for 2 h a solution of trimethystannylchloride
12.42 g (62.3 mmol) in Et2O (50 mL) was added dropwise. Then the
mixture was allowed to warm up to room temperature overnight. The
insoluble inorganic precipitate was removed by filtration, and the solvent
was evaporated under reduced pressure. The residue was distilled to afford
6.84 g (24.79 mmol) of 2b (47.7%) as a colourless oil. 1H NMR (270 MHz,
CDCl3): d ˆ 0.32 [s, 3H; Sn(CH3)] 7.37 (d, JH-3,H-4 ˆ 8.2 Hz, 1H; H-3), 7.49
(dd, JH-4,H-6 ˆ 2.2 Hz, JH-4,H-3 ˆ 8.2 Hz, 1H; H-4), 8.69 (d, JH-6,H-4 ˆ 2.2 Hz,
1H; H-6); 13C NMR (68 MHz, CDCl3): d ˆ 131.30, 131.64, 133.05, 149.16,
171.02; MS (70 eV, EI): m/z (%): 281 (4.96), 279 (10.28), 278 (6.19), 277
‡
‡
262 (15.50) [M
OCH3], 238 (7.24), 236 (14.58), 234 (7.56) [M
‡
CO2CH3], 216 (23.20), 214 (23.42) [M
Br]; C7H5Br2NO2 (294.93): calcd
C 28.50, H 1.70, N 4.74; found C 28.49, H 1.71, N 4.59.
2,6-Dibromo-4-hydroxymethylpyridine (1d): A suspension of LiALH4
(8.13 g, 214.4 mmol) in dry THF (50 mL) was added dropwise to a solution
of 1c (97.3 g, 329.9 mmol) in THF (500 mL) over a period of 30 min at
208C. The mixture was allowed to warm to RT within 2 h and brine
(200 mL) was added carefully. The layers were separated and the aqueous
layer was extracted with CH2Cl2 (150 mL). The combined organic extracts
were dried over MgSO4, and the solvent was evaporated in vacuum.
Chromatographic separation on silica with hexane/ethyl ether (1:1) as
eluent gave 51.2 g of 1d (58.1%) as a white solid, m.p. 110 ± 1118C. 1H NMR
(270 MHz, [D6]DMSO): d ˆ 4.54 (brs, 2H) 5.68 (brs, 1H), 7.60 (s, 2H);
13C NMR (68 MHz, [D6]DMSO): d ˆ 60.53, 124.53, 139.76, 158.82; MS
‡
(26.99), 276 (13.42), 275 (21.45), 274 (9.96), 273 (11.22) [M ], 265 (4.28), 264
(36.82), 263 (16.75), 262 (100.00), 261 (34.75), 260 (72.85), 259 (24.09), 258
‡
(36.83) [M
CH3], 234 (19.55), 233 (7.86), 232 (50.71), 231 (17.57), 230
‡
(80 eV, EI): m/z (%): 269 (48.28), 267 (100.00), 265 (50.97) [M ], 188
‡
(36.45), 229 (12.65) [M
2CH3]; HRMS: m/z calcd for C8H12ClNSn
‡
(46.41), 186 (51.24) [M
Br]; C6H5Br2NO (266.91): calcd C 27.00, H 1.88,
276.96802; found 276.96832.
N 5.24; found C 27.16, H 1.82, N 5.07.
5,5''-Dichloro-2,2':6',2''-terpyridine (3a)
2,6-Dibromo-4-hexoxymethylpyridine (1e):
A mixture of 1d (4.73 g,
Method A: 2,6-Dibromopyridine (1a; 1.09 g, 4.60 mmol) and 2b (3 g,
10.85 mmol) were dissolved in toluene (70 mL). The solution was degassed
twice. Then (Ph3P)4Pd (0.228 g, 0.197 mmol) was added and the mixture
was degassed again. After the mixture was refluxed for 41 h, a saturated
solution of KF (50 mL) was added, and the inorganic precipitate was
filtered. The organic phase was separated, and the solvent was evaporated.
The aqueous layer was extracted with CH2Cl2 (2 Â 30 mL). The residue and
the organic layers were combined and diluted with 15% HCl (30 mL). The
solution was warmed and stirred for 5 min. The aqueos layer was separated,
made alkaline with Na2CO3, and washed with CH2Cl2 (2 Â 50 mL). The
organic phases were combined, dried over MgSO4, and evaporated to give
0.905 g of 3a (65.1%) as a white solid.
17.72 mmol) and NEt3 (2.47 mL, 17.72 mmol) in CH2Cl2 (40 mL) was
slowly added to a solution of triflate anhydride (2.98 mL, 17.72 mmol) in
dry CH2Cl2 (20 mL), within 45 min at 08C. After 15 min the mixture was
treated with hexanol (50 mL) and stirred at RT for 1 h. Solvent and excess
hexanol were removed under reduced pressure. The residue was dissolved
in CH2Cl2 (100 mL) and washed with H2O (20 mL). The organic phase was
separated, dried over MgSO4, and evaporated. Chromatography of the
compound on silica gel gave 4.9 g of 1e (78.7%) as a colourless oil. 1H NMR
(270 MHz, CDCl3): d ˆ 0.82 (t, J ˆ 6.6 Hz, 3H), 1.24 ± 1.35 (m, 6H), 1.56 (q,
J ˆ 6.6 Hz, 2H), 3.43 (t, J ˆ 6.6 Hz, 2H), 4.38 (s, 2H), 7.34 (s, 2H); 13C NMR
(68 MHz, CDCl3): d ˆ 13.92, 22.45, 25.62, 29.37, 31.46, 69.54, 71.41, 124.68,
140.55, 153.58; MS (70 eV, EI): m/z (%): 353 (0.5), 351 (0.98), 349 (0.53)
Method B: Compound 2a (19.9 g, 103.3 mmol) and 2,6-bis(trimethylstan-
nyl)pyridine (4a; 19.01 g, 47.0 mmol) were dissolved in toluene (400 mL).
The solution was degassed twice. Then (Ph3P)4Pd (2.17 g, 1.87 mmol) was
added, and the mixture was degassed again. After the mixture was heated
under reflux for 60 h, a saturated solution of KF (150 mL) was added, and
the inorganic precipitate removed by filtration. The organic phase was
separated, and the solvent was evaporated. The aqueous layer was
extracted with CH2Cl2 (2 Â 200 mL). The residue and the organic layers
were combined and diluted with 15% HCl (280 mL). The solution was
warmed and stirred for 5 min. The aqueous layer was separated, made
alkaline with Na2CO3, and washed with CH2Cl2 (300 mL). The organic
phases were combined, dried over MgSO4, and evaporated to give 6.3 g of
3a (44.4%) as a white solid, m.p. 1958C. The same experiment was also
carried out at a much smaller scale (0.457 g 4a) and gave 3a with higher
‡
‡
[M ], 269 (2.89), 267 (5.83), 265 (3.34) [M
C6H13‡H], 253 (49.32), 251
‡
(100.00), 249 (51.93) [M
OC6H13‡H]; C12H17Br2NO (351.08): calcd C
41.05, H 4.88, N 3.98; found C 40.83, H 4.74, N 3.87.
4-Hexoxymethyl-2,6-bis(trimethylstannyl)pyridine (4e): Compound 1e
(1.45 g, 4.13 mmol) dissolved in DME (10 mL) was added to a solution of
NaSn(CH3)3 in DME (20 mL), prepared from Na (0.842 g, 36.62 mmol) and
ClSn(CH3)3 (2.43 g, 12.19 mmol), over a period of 20 min at 08C. After 2 h
the solution was allowed to warm and stirred for 2 h at RT. The inorganic
precipitate was filtered and the solvent removed under reduced pressure to
give 1.46 g of 4e as crude product, which was used without further
purification. 1H NMR (270 MHz, CDCl3): d ˆ 0.30 (s, 18H; Sn(CH3)3), 0.88
(t, J ˆ 6.4, 3H), 1.28 ± 1.42 (m, 6H), 1.63 (q, J ˆ 6.4 Hz, 2H), 3.48 (t, J ˆ
6.4 Hz, 2H), 4.41 (s, 2H), 7.28 (s, 2H). 13C NMR (68 MHz, CDCl3): d ˆ
9.42 (s, Sn(CH3)3), 14.04, 22.60, 25.89, 29.68, 31.67, 70.99, 71.73, 128.18,
141.87, 173.63; MS (80 eV, EI): m/z (%): 508 (31.59), 507 (25.65), 506
1
yield (66.1%). H NMR (270 MHz, CDCl3): d ˆ 7.79 (dd, JH-4,H-6 ˆ 2.4 Hz,
JH-4,H-3 ˆ 8.6 Hz, 2H; H-4), 7.93 (t, JH-4',H-3' ˆ 7.8 Hz, 1H; H-4'), 8.40 (d,
JH-3'H-4' ˆ 7.8 Hz, 2H; H-3'), 8.52 (d, JH-3,H-4 ˆ 8.6 Hz, 2H; H-3), 8.62 (d,
JH-6, H-4 ˆ 2.4 Hz, 2H; H-6); 13C NMR (68 MHz, CDCl3): d ˆ 121.13, 121.85,
132.33, 136.55, 138.08, 148.00, 154.16, 154.40; MS (80 eV, EI): m/z (%): 305
(79.48), 505 (52.54), 504 (100), 503 (65.01), 502 (92.10), 501 (43.77), 500
‡
(45.31), 499 (18.15) [M
CH3], 476 (6.94), 475 (4.61), 474 (8.42), 473
‡
(5.69), 472 (7.39), 471 (3.84), 470 (4.11), 469 (4.66), 468 (3.30) [M
HRMS: m/z calcd for [M
3 CH3];
‡
‡
‡
(10.98), 303 (64.46), 301 (100), [M ], 268 (6.71), 266 (13.08) [M
Cl];
CH3] 504.052196; found 504.05481.
HMRS: m/z calcd for C15H9N3Cl2 301.017353; found 301.01809; C15H9Cl2N3
(302.15): calcd C 59.62, H 3.00, N 13.90; found C 59.79, H 3.16, N 13.34.
5,5''-Dibromo-4'-hexoxymethyl-2,2':6',2''-terpyridine (6e): A solution of
crude 4e and 5 (1.48 g, 6.24 mmol) in toluene (50 mL) was degassed twice.
Then (Ph3P)4Pd (0.065 g, 0.056 mmol) was added, and the system was
degassed again. The solution was refluxed and stirrred vigorously for 60 h,
then allowed to cool to RT and extracted with a saturated solution of KF
(20 mL). Removal of the solvent and chromatographic separation on silica
gel afforded 0.324 g of 6e (15.5% with reference to 1e) as a white solid,
m.p. 908C. 1H NMR (270 MHz, CDCl3): d ˆ 0.86 (t, J ˆ 6.9, 3H), 1.22 ± 1.43
(m, 6H), 1.64 (q, J ˆ 6.7 Hz, 2H), 3.52 (t, J ˆ 6.7 Hz, 2H), 4.61 (s, 2H), 7.90
(dd, J H-4,H-6 ˆ 1.8 Hz, JH-4,H-3 ˆ 8.8 Hz, 2H; H-4), 8.35 (s, 2H; H-3'), 8.40 (d,
JH-3,H-4 ˆ 8.8 Hz, 2H; H-3), 8.69 (d, JH-6,H-4 ˆ 1.8 Hz, 2H; H-6); 13C NMR
(68 MHz, CDCl3): d ˆ 13.94, 22.52, 25.74, 29.55, 31.57, 71.19, 71.28, 119.19,
121.03, 122.21, 139.11, 149.92, 150.14, 154.20, 154.33; MS (80 eV, EI): m/z
5,5''-Dibromo-2,2':6',2''-terpyridine (6a): Terpyridine 6a (5.7 g, 26.5%) was
obtained from 4a (22.24 g, 54.95 mmol), 5 (31.24 g, 131.9 mmol), and
(Ph3P)4Pd (2.53 g, 2.19 mmol) with the procedure described in method B
for 3a as a white solid, m.p. 1978C. 1H NMR (270 MHz, CDCl3): d ˆ 7.93 (t,
JH-4'H-3' ˆ 7.8 Hz, 1H; H-4'), 7.95 (dd, JH-4,H-6 ˆ 2.2 Hz, JH-4,H-3 ˆ 8.4 Hz, 2H;
H-4), 8.41 (d, JH-3',H-4' ˆ 7.8 Hz, 2H; H-3'), 8.47 (d, JH-3,H-4 ˆ 8.4 Hz, 2H;
H-3), 8.72 (d, JH-6,H-4 ˆ 2.2 Hz, 2H; H-6); 13C NMR (68 MHz, CDCl3): d ˆ
121.17, 121.23, 122.33, 138.10, 139.43, 150.18, 154.47; MS (80 eV, EI): m/z
‡
(%): 393 (51.13), 391 (100), 389 (53.41) [M ], 312 (10.72), 310 (10.84),
‡
[M
Br]; C15H9Br2N3 (391.06): calcd C 46.07, H 2.31, N 10.74; found C
45.85, H 2.40, N 10.74.
‡
2,6-Dibromo-4-methoxycarbonylpyridine (1c): A solution of 1b (53.4 g,
190.2 mmol) in MeOH (300 mL) was treated with conc. H2SO4 (2.4 mL)
and refluxed for 16 h. After the mixture was cooled to RT, a white solid
precipated. The crude product was filtered and chromatographed on silica
(%): 507 (1.09), 505 (2.20), 503 (1.13) [M ], 422 (8.10), 420 (15.09), 418
‡
‡
(7.60) [M
C6H13], 407 (52.10), 405 (100), 403 (53.80) [M
OC6H13‡H];
C22H23Br2N3O (505.25): calcd C 52.29, H 4.58, N 8.31; found C 52.19, H 4.41,
N 8.21.
Chem. Eur. J. 1999, 5, No. 3
ꢀ WILEY-VCH Verlag GmbH, D-69451 Weinheim, 1999
0947-6539/99/0503-0857 $ 17.50+.50/0
857

A. D. Schlüter et al.
FULL PAPER
5,5''-Dichloro-4'-hexoxymethyl-2,2':6',2''-terpyridine (3e): Terpyridine 3e
was obtained from 1e (1.73 g, 4.92 mmol), 2b (3.00 g, 10.84 mmol), and
(Ph3P)4Pd (0.228 g, 0.197 mmol) in 70 mL toluene with the procedure
described for 6e. The crude product was chromatographed on silica gel to
afford 1.40 g of 3e (68.6%) as a white solid, m.p. 888C. 1H NMR (270 MHz,
CDCl3): d ˆ 0.83 (t, J ˆ 7.0 Hz, 3H), 1.17 ± 1.37 (m, 6H), 1.60 (q, J ˆ 6.7 Hz,
144.84, 155.95; MS (80 eV, EI): m/z (%): 555 (7.10), 554 (8.49), 553 (23.37),
552 (18.92), 551 (25.11), 550 (16.94), 549 (12.35), 548 (5.72) [M ] (trimeric
anhydride), 474 (13.81), 473 (13.24), 472 (28.18), 471 (20.42), 470 (19.16),
‡
‡
‡
469 (11.43) [M
Br] (trimeric anhydride), 212 (21.41), 210 (24.48) [M
‡
2H‡B] (monomer), 186 (19.78), 184 (26.07) [M
OH] (monomer), 159
‡
‡
(77.05), 157 (100,00) [M
BO2H] (monomer), 104 (49.03) [M
H2O
‡
2H), 3.46 (t, J ˆ 6.7 Hz, 2H), 4.52 (s, 2H), 7.64 (dd, JH-4,H-6
ˆ
2.4 Hz,
Br] (monomer), 78 (64.20) [M
BO2H Br] (monomer); HRMS: m/z
JH-4,H-3 ˆ 8.6 Hz, 2H; H-4), 8.25 (s, 2H; H-3'), 8.33 (d, JH-3,H-4 ˆ 8.6 Hz, 2H;
H-3), 8.52 (d, JH-6,H-4 ˆ 2.4 Hz, 2H; H-6); 13C NMR (68 MHz, CDCl3): d ˆ
13.90, 22.49, 25.72, 29.52, 31.55, 71.14, 71.26, 119.08, 121.64, 132.02, 136.15,
147.67, 150.07, 153.86, 154.18; MS (80 eV, EI): m/z (%): 419 (0.59), 417
calcd for C15H9B3Br3N3O3 (trimeric anhydride) 550.845269; found
550.84564. The crude boronic acid and 2,3-dimethylbutane-2,3-diol
(12.44 g, 105.25 mmol) were dissolved in 1,4-dioxane (400 mL). The solvent
was evaporated under normal pressure, and the residue was chromato-
graphed on silica gel to give 13.66-17.04 g of 8 (45.6 ± 56.8% with reference
to 5) as white solid, m.p. 948C. 1H NMR (270 MHz, CDCl3): d ˆ 7.43 (d,
JH-3,H-4 ˆ 7.7 Hz,1H; H-3), 7.83 (dd, JH-4,H-6 ˆ 1.2 Hz, JH-4,H-3 ˆ 7.7 Hz, 1H;
H-4), 8.62 (d, JH-6,H-4 ˆ 1.2 Hz, 1H; H-6); 13C NMR (68 MHz, CDCl3): d ˆ
24.77, 84.44, 127.55, 144.33, 145.39, 156.00; MS (80 eV, EI): m/z (%): 286
‡
‡
(2.61), 415 (4.06) [M ], 334 (1.89), 332 (8.24), 330 (11.73) [M
C6H13], 319
‡
(11.40), 317 (64.52), 315 (100) [M
OC6H13]; C22H23Cl2N3O (416.34):
calcd C 63.46, H 5.56, N 10.09; found C 63.31, H 5.62, N 9.92.
2,6-Dibromo-4-methoxyethoxymethoxymethylpyridine (1 f): A suspension
of 1d (4.70 g, 17.6 mmol) in CH2Cl2 (30 mL) was added to a solution of
MEM chloride (3.29 g, 3.00 mL, 26.4 mmol) and diisopropylethylamine
(3.41 g, 4.50 mL, 26.4 mmol) in CH2Cl2 (100 mL) at RT. The mixture was
stirred for 3 h, and then H2O (50 mL) was added. The layers were separated
and the aqueous phase was extracted with CH2Cl2 (2 Â 60 mL). After the
combined organic phases were dried over MgSO4, and evaporated,
chromatography on silica gel gave 4.37 g of 1 f (69.9%) as a colorless oil.
1H NMR (270 MHz, CDCl3): 3.09 (s, 3H), 3.25 ± 3.31 (m, 2H), 3.43 ± 3.48
(m, 2H), 4.23 (s, 2H), 4.51 (s, 2H), 7.17 (s, 2H); 13C NMR (68 MHz,
CDCl3): d ˆ 58.52, 65.77, 66.56, 71.31, 94.92, 124.26, 140.00, 152.62; MS
‡
(7.20), 285 (53.22), 284 (25.70) 283 (55.89), 282 (23.45) [M ], 271 (12.88),
‡
270 (98.25), 269 (38.25), 268 (100), 267 (27.32) [M
(34.99), 227 (13.60), 226 (38.95), 225 (11.61) [M
CH3], 229 (3.18), 228
CH3 C3H6], 187 (4.30),
CH3 C3H6 CH2CO],
‡
‡
186 (57.80), 185 (22.56), 184 (57.01), 183 (19.58) [M
‡
104 (29.62) [M
C6H12O Br]; C11H15BBrNO2 (283.94) calcd C 46.52, H
5.32, N 4.93; found C 46.57, H 5.20, N 4.84.
5,5''-Bis[4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl]-2,2': 6',2''-terpyridine
(9): Boronic ester 8 (6.76 g, 23.80 mmol) and 4a (4.37 g, 10.79 mmol) were
dissolved in toluene (70 mL). The mixture was degassed twice. Then
(Ph3P)4Pd (0.249 g, 0.215 mmol) was added, and the system was degassed
again. After the mixture was refluxed for 15 h, a saturated solution of KF
(30 mL) was added, and the inorganic precipate was removed by filtration.
The layers were separated and the aqueous layer was washed with toluene
(2 Â 20 mL). The combined organic layers were dried over MgSO4 and
filtered, and the solvent was removed. Recrystallization from toluene
afforded 2.87 g of 9 (55.0%) as a white solid, m.p. 2518C. 1H NMR
(270 MHz, CDCl3): d ˆ 1.36 (s, 12H), 7.93 (t, JH-4',H-3' ˆ 7.8 Hz, 1H; H-4'),
8.20 (dd, JH-4,H-6 ˆ 1.5 Hz, JH-4,H-3 ˆ 7.8 Hz, 2H; H-4), 8.48 (d, J ˆ 7.8 Hz,
2H), 8.56 (d, J ˆ 7.8 Hz, 2H), 9.00 (d, JH-6,H-4 ˆ 1.5 Hz, 2H; H-6); 13C NMR
(68 MHz, CDCl3): d ˆ 24.86, 84.17, 120.24, 121.70, 137.81, 143.12, 155.05,
155.41, 158.08; MS (80 eV, EI): m/z (%): 487 (6.54), 486 (31.69), 485
‡
(70 eV, EI): m/z (%): 357 (1.05), 355 (2.18), 353 (1.09) [M ], 282 (7.83), 280
‡
(15.93), 278 (8.36) [M
248 (37.63) [M
O CH2 CH2 OCH3], 252 (40.66), 250 (75.80),
‡
‡
OMEM], 171 (15.70), 169 (14.57) [M
OMEM Br],
‡
45 (100) [CH2 OCH3 ]; C10H13Br2NO3 (355.02): calcd C 33.83, H 3.69, N
3.94; found C 33.64, H 3.50, N 3.87.
4-Methoxyethoxymethoxymethyl-2,6-bis(trimethylstannyl)pyridine (4 f):
Compound 4 f was obtained from 1 f (1.50 g, 4.22 mmol) with the procedure
described for 4e to give 1.79 g as crude product, which was used without
further purification. 1H NMR (270 MHz, CDCl3): 0.28 [s, 18H; Sn(CH3)3],
3.32 (s, 3H), 3.43 ± 3.56 (m, 2H), 3.60 ± 3.76 (m, 2H), 4.52 (s, 2H), 4.78 (s,
2H), 7.25 (s, 2H); 13C NMR (68 MHz, CDCl3): d ˆ 9.62 (s, Sn(CH3)3),
58.67, 66.77, 67.95, 71.51, 94.86, 128.01, 140.97, 173.39; MS (70 eV, EI): m/z
(%): 514 (50.90), 512 (57.96), 511 (53.73), 510 (87.30), 509 (70.26), 508
(100.00), 507 (78.94), 506 (94.23), 505 (65.32), 504 (66.41), 503 (47.23), 502
‡
‡
(100.00), 484 (48.89), 483 (8.68) [M ], 470 (6.13) [M
CH3], 428 (2.61)
‡
‡
[M
CH3 C3H6], 386 (16.04) [M
CH3 C3H6 CH2CO]; HRMS: m/z
‡
‡
calcd for C27H33B2N3O4 485.26518; found 485.26312.
(49.11) [M ], 465 (48.18), 463 (51.07), 462 (46.50), 461 (50.15) [M
‡
CH2 OCH3], 404 (47.71) [M
OMEM].
5,5''-Bis[5-bromo-3-hexoxymethylphenyl]-2,2':6',2''-terpyridine (12a)
5,5''-Dibromo-4'-methoxyethoxymethoxymethyl-2,2':6',2''-terpyridine (6 f):
Terpyridine 6 f was prepared from 4 f (1.79 g), 5 (1.78 g, 7.55 mmol), and
(Ph3P)4Pd (0.040 g, 0.034 mmol) in toluene (70 mL) with the procedure
desribed for 6e. Chromatographic separation on silica gel afforded 0.57 g of
6 f (26.4% with reference to 1 f) as a white solid. The same experiment was
also done on a larger scale starting from 7.42 g of 1 f to give 2.63 g of 6 f
(24.7%), m.p. 1348C. 1H NMR (270 MHz, CDCl3): 3.38 (s, 3H), 3.54 ± 3.57
Method A: A suspension of 6a (6.2 g, 15.85 mmol) in DME (50 mL) was
added to a solution of NaSn(CH3)3 in 60 mL DME, prepared as described
in the literature from Na (3.29 g, 143.3 mmol) and ClSn(CH3)3 (9.53 g,
47.82 mmol), over a period of 20 min at 08C. After 2 h the solution was
allowed to warm and was stirred for 2 h at RT. The inorganic precipate was
filtered off, and the solvent removed under reduced pressure to give crude
10. This material and 11 (13.84 g, 34.85 mmol) were dissolved in toluene
(150 mL). The mixture was degassed twice, then (Ph3P)4Pd (0.732 g,
0.634 mmol) was added, and the system was degassed again. After the
mixture was refluxed for 39 h, a saturated solution of KF (50 mL) was
added, and the inorganic precipate was removed by filtration. The layers
were separated, and the aqueous layer was washed with CH2Cl2 (30 mL).
The combined organic layers were dried over MgSO4 and filtered, and the
solvent removed. Chromatographic separation on aluminium oxide with
hexane/CH2Cl2 as eluent afforded 3.26 g of 12a (26.7% with reference to
6a) as white solid.
(m, 2H), 3.75 ± 3.79 (m, 2H), 4.77 (s, 2H), 4.88 (s, 2H), 7.94 (dd, JH-4,H-6
2.3 Hz, JH-4,H-3 ˆ 8.6 Hz, 2H; H-4), 8.40 (s, 2H; H-3'), 8.46 (d, JH-3,H-4
ˆ
ˆ
8.6 Hz, 2H; H-3), 8.72 (d, JH-6,H-4 ˆ 2.3 Hz, 2H; H-6); 13C NMR (68 MHz,
CDCl3): d ˆ 58.90, 67.00, 67.90, 71.59, 95.27, 119.13, 121.10, 122.25, 139.19,
149.46, 149.95, 154.14, 154.43; MS (80 eV, EI): m/z (%): 511 (1.01), 509
‡
‡
(3.09), 507 (1.61) [M ], 452 (7.48), 450 (14.44), 448 (7.85) [M
‡
CH2 CH2 OCH3], 422 (14.87), 420 (27.44), 418 (15.36) [M
MEM],
‡
407 (50.43), 405 (100.00), 403 (53.33) [M
OMEM‡H]; C20H19Br2N3O3
(509.19): calcd C 47.17, H 3.76, N 8.25; found C 47.08, H 3.60, N 7.91.
2-Bromo-5-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)pyridine (8): BuLi
(1.6m, 69 mL) in hexane was added dropwise to a solution of compound 5
(25 g, 105.5 mmol) in Et2O (800 mL), while the temperature was kept at
788C. After stirring at 788C for 6 h, a solution of triisopropyl borate
(41.67 g, 221.6 mmol) in Et2O (50 mL) was added dropwise. Then the
mixture was allowed to warm to room temperature overnight. The solvent
was evaporated under reduced pressure, and the residue was chromato-
graphed on silica gel first with EtOAc as eluent to remove impurities and
second with MeOH to wash the product off the column to give 21.26 g of
crude 2-bromopyridyl-5-boronic acid, which was used for the subsequent
esterification without further purification. 1H NMR (270 MHz,
Method B: Compounds 9 (2.0 g, 4.12 mmol) and 11 (3.6, 9.06 mmol) were
dissolved in toluene (40 mL) and a sodium carbonate solution (1m, 40 mL)
was added. The mixture was degassed twice. Then (Ph3P)4Pd (0.047 g,
0.041 mmol) was added, and the system was degassed again. The solution
was refluxed for 72 h with vigorous stirring. The mixture was allowed to
cool to RT, the layers were separated, and the aqueous layer was washed
with CH2Cl2 (2 Â 40 mL). The combined organic layers were dried over
MgSO4 and filtered, and the solvent removed. Chromatographic separation
on aluminium oxide with hexane/CH2Cl2 (3:2) as eluent afforded 1.30 g of
12a (41.1%) as white solid, m.p. 858C. 1H NMR (270 MHz, CDCl3): d ˆ
0.86 (t, J ˆ 6.5 Hz, 6H), 1.20 ± 1.39 (m, 12H), 1.60 (q, J ˆ 6.7 Hz, 4H), 3.45
[D6]DMSO): d ˆ 7.59 (d, JH-3,H-4 ˆ 8.2 Hz, 1H; H-3), 7.99 (dd, JH-4,H-6
ˆ
(t, J ˆ 6.7 Hz, 4H), 4.45 (s, 4H), 7.45 (s, 4H), 7.60 (s, 2H), 7.88 (t, JH-4',H-3' ˆ
2.0 Hz, JH-4,H-3 ˆ 8.2 Hz, H-4), 8.44 [brs, B(OH)2], 8.62 (d, JH-6,H-4 ˆ 2.0 Hz,
1H; H-6); 13C NMR (68 MHz, [D6]DMSO): d ˆ 127.48, 128.41, 143.79,
7.8 Hz, 1H; H-4'), 7.91 (dd, JH-4,H-6 ˆ 2.3 Hz, JH-4,H-3 ˆ 8.3 Hz, 2H; H-4), 8.41
(d, JH-3',H-4' ˆ 7.8 Hz, 2H; H-3'), 8.55 (d, JH-3,H-4 ˆ 8.3 Hz, 2H; H-3), 8.79 (d,
858
ꢀ WILEY-VCH Verlag GmbH, D-69451 Weinheim, 1999
0947-6539/99/0503-0858 $ 17.50+.50/0
Chem. Eur. J. 1999, 5, No. 3

Disubstituted Terpyridines
854±859
JH-6,H-4 ˆ 2.3 Hz, 2H; H-6); 13C NMR (68 MHz, CDCl3): d ˆ 13.93, 22.47,
25.72, 29.53, 31.51, 70.85, 71.63, 120.70, 120.95, 123.04, 124.24, 128.66,
129.70, 134.61, 134.72, 137.54, 139.41, 141.78, 147.21, 154.60, 155.19; MS
(70 eV, EI): m/z (%): 774 (22.23), 773 (54.89), 772 (45.56), 771 (100), 770
Lett. 1983, 24, 2707; T. W. Bell, A. Firestone, J. Am. Chem. Soc. 1986,
108, 8109; T. W. Bell, A. Firestone, R. Ludwig, J. Chem. Soc. Chem.
Commun. 1989, 1902; T. W. Bell, P. J. Cragg, M. G. B. Drew, A.
Firestone, D.-I. A. Kwok, Angew. Chem. 1992, 104, 319; Angew.
Chem. Int. Ed. Engl. 1992, 31, 345; T. W. Bell, P. J. Cragg, M. G. B.
Drew, A. Firestone, A. D.-I. Kwok, J. Liu, R. T. Ludwig, A. T.
Papoulis, Pure Appl. Chem. 1993, 65, 361; U. Velten, M. Rehahn,
Macromol. Chem. Phys. 1998, 199, 127. For some flexible cycles with
terpyridine units, see: E. C. Constable, Prog. Inorg. Chem. 1994, 42, 67.
For some other cycles with interior donor groups, see: Y. Tobe, N.
Utsumi, A. Nagano, K. Naemura, Angew. Chem. 1998, 110, 1347;
Angew. Chem. Int. Ed. 1998, 37, 1285; S. Höger, A.-D. Meckenstock,
H. Pellen, J. Org. Chem. 1997, 62, 4556.
‡
(24.34), 769 (48.05) [M ], 688 (16.24), 687 (41.96), 686 (33.51), 685 (78.08),
‡
684 (20.44), 683 (40.73) [M
C6H13 H], 673 (14.66), 672 (41.68), 671
‡
(36.01), 670 (79.52), 669 (32.04), 668 (41.67) [M
(11.54), 571 (28.25), 570 (13.11), 569 (48.77), 568 (17.04), 567 (22.57) [M
OC6H13 H], 572
‡
2OC6H13], 493 (13.71), 492 (38.66), 491 (24.32), 490 (43.64), 489 (16.49)
‡
[M
2OC6H13 Br‡H]; C41H45Br2N3O2 (771.63): calcd C 63.81, H 587, N
5.44; found C 63.71, H 5.74, N 5.48.
5,5''-Bis[5-trimethylstannyl-3-hexoxymethylphenyl]-2,2':6',2''-terpyridine
(12b): A solution of 12a (3.37 g, 4.36 mmol) in DME (10 mL) was added to
a solution of NaSn(CH3)3 in DME (60 mL), prepared as described in the
literature from Na (2.40 g, 104.6 mmol) and ClSn(CH3)3 (6.94 g,
34.88 mmol), over a period of 20 min at 08C. After 2 h the solution was
allowed to warm to RTand stirred for 2 h at this temperature. The inorganic
precipitate was filtered off, and the solvent was removed under reduced
pressure. The residue was chromatographed on aluminium oxide with
hexane/CH2Cl2 (3:2) as eluent to give 2.52 g of 12b (61.4%) as a white
solid, m.p. 98 ± 998C. 1H NMR (270 MHz, CDCl3): d ˆ 0.35 (s,18H), 0.88 (t,
J ˆ 6.5 Hz, 6H), 1.27 ± 1.45 (m, 12H), 1.65 (q, J ˆ 6.6 Hz, 4H), 3.53 (t, J ˆ
6.6 Hz, 4H), 4.59 (s, 4H), 7.52 (s, 2H), 7.58 (s, 2H), 7.76 (s, 2H), 7.98 (t,
JH-4',H-3' ˆ 7.9 Hz, 1H; H-4'), 8.07 (dd, JH-4,H-6 ˆ 2.3 Hz, JH-4,H-3 ˆ 8.2 Hz, 2H;
H-4), 8.50 (d, JH-3',H-4' ˆ 7.9 Hz, 2H; H-3'), 8.71 (d, JH-3,H-4 ˆ 8.2 Hz, 2H;
H-3), 8.95 (d, JH-6,H-4 ˆ 2.3 Hz, 2H; H-6); 13C NMR (68 MHz, CDCl3): d ˆ
14.01, 22.56, 25.87, 29.70, 31.64, 70.74, 72.76, 120.83, 120.91, 126.33, 133.47,
134.72, 135.18, 136.75, 137.25, 137.78, 138.85, 143.51, 147.67, 154.91, 155.12;
MS (70 eV, EI): m/z (%): 942 (6.74), 941 (12.25), 940 (10.97), 939 (14.79),
[4] J. K. Stille, Angew. Chem. 1986, 98, 504; Angew. Chem. Int. Ed. Engl.
1986, 25, 508.
[5] N. Miyaura, A. Suzuki, Chem. Rev. 1995, 95, 2457; A. D. Schlüter, G.
Wegner, Acta Polym. 1993, 59, 44.
[6] An option is of course to introduce flexible chains in a subsequent
growth step.
[7] A. M. W. Cargill Thompson, Coord. Chem. Rev. 1997, 160, 1.
[8] a) F. H. Burstall, J. Chem. Soc. 1938, 1662; b) A. A. Schilt, G. F.
Smith, Anal. Chim. Acta 1956, 15, 567; c) C. O. Dietrich-Buchecker,
P. O. Marnot, J.-P. Sauvage, J.-P. Kintzinger, P. Maltese, Nouv. J. Chim.
1984, 8, 573; d) J. R. Kirchhoff, D. R McMillon, P. A. Marnot, J.-P.
Sauvage, J. Am. Chem. Soc. 1985, 107, 1138; e) J.-P. Sauvage, M. Ward,
Inorg. Chem. 1991, 30, 3869.
[9] For terpyridines with bromo or chloro substituents at C-6 and C-6'',
see: ref. [8a]; a) D. C. Owsley, J. M. Nelke, J. J. Bloomfield, J. Org.
Chem. 1973, 38, 901; b) K. T. Potts, M. J. Cipullo, P. Ralli, G.
Theodoridis, J. Am. Chem. Soc. 1981, 103, 3585; c) G. R. Newkome,
D. C. Hager, G. E. Kiefer, J. Org. Chem. 1986, 51, 850; d) E. C.
Constable, J. M. Holmes, R. C. S. McQueen, J. Chem. Soc., Dalton
Trans. 1987, 5; e) Y. Uchida, M. Okabe, H. Kobayashi, S. Oae,
Synthesis, 1995, 939.
‡
938 (7.71), 937 (12.21), 936 (7.40), 935 (6.65) [M ], 928 (23.49), 927 (33.93),
926 (70.20), 925 (68.67), 924 (100), 923 (51.32), 922 (70.03), 921 (35.13)
‡
[M
CH3]; C47H63N3O2Sn2 (939.45) calcd C 60.09, H 6.75, N 4.47; found C
59.87, H 6.59, N 4.30.
5,5''-Bis[5-iodo-3-hexoxymethylphenyl]-2,2':6',2''-terpyridine (12c): A sol-
ution of I2 (0.767 g, 3.02 mmol) in CH2Cl2 (10 mL) was added to a solution
of 12b (1.42 g, 1.51 mmol) in CH2Cl2 (20 mL) over a period of 15 min at RT.
The reaction mixture was stirred for 1 h at this temperature, and then a
saturated solution of KF (10 mL) was added. The resulting mixture was
made alkaline with potassium carbonate and subsequently extracted with
CH2Cl2 (2 Â 20 mL). The combined organic layers were washed with a
saturated solution of KF and a saturated sodium thiosulfate solution, dried
over MgSO4, and concentrated under reduced pressure. Some impurities
were separated by chromatography on silica gel with hexane/CH2Cl2 (3:2)
as eluent. The product was eluted by CH2Cl2 affording 1.28 g of 12c
(97.8%) as a white solid, m.p. 718C. 1H NMR (270 MHz, CDCl3): d ˆ 0.87
(t, J ˆ 6.7 Hz, 6H), 1.25 ± 1.40 (m, 12H), 1.60 (q, J ˆ 6.6 Hz, 4H), 3.49 (t, J ˆ
6.6 Hz, 4H), 4.49 (s, 4H), 7.55 (s, 2H), 7.71 (s, 2H), 7.87 (s, 2H), 7.93 (t,
JH-4',H-3' ˆ 7.8 Hz, 1H; H-4'), 7.97 (dd, JH-4,H-6 ˆ 2.4 Hz, JH-4,H-3 ˆ 8.3 Hz, 2H;
H-4), 8.46 (d, JH-3',H-4' ˆ 7.8 Hz, 2H; H-3'), 8.64 (d, JH-3,H-4 ˆ 8.3 Hz, 2H;
H-3), 8.85 (d, JH-6,H-4 ˆ 2.4 Hz, 2H; H-6); 13C NMR (68 MHz, CDCl3): d ˆ
14.04, 22.60, 25.85, 29.67, 31.65, 71.03, 71.75, 95.02, 121.03, 121.20, 125.39,
134.98, 135.16, 136.00, 137.97, 139.84, 141.91, 147.52, 154.99, 155.50; MS
[10] K. Abe, Y. Kitagawa, A. Ishimura, J. Pharm. Soc. Jpn. 1953, 73, 969.
[11] Jpn. Kokai Tokkyo Koho, JP 63093766; Chem. Abstr. 1989, 110,
110110 (in Japanese).
[12] A. Levelt, B. Wibaut, Recl. Trav. Chim. Pays-Bas 1929, 48, 470; A.
Levelt, C. Overhoff, Recl. Trav. Chim. Pays-Bas 1933, 52, 55, 58; A.
Levelt, C. Overhoff, Recl. Trav. Chim. Pays-Bas 1933, 55, 57.
[13] F. Effenberger, A. Krebs, P. Willrett, Chem. Ber. 1992, 125, 1131.
[14] As the present work was in progress a patent was filed: C. Black, G.
Hughes, Z. Wang, PCT Int. Appl. WO 9740012; Chem. Abstr. 1998,
128, 13207
[15] Yamamoto was first to use the Stille reaction for terpyridine synthesis:
Y. Yamamoto, Y. Azuma, H. Mitoh, Synthesis 1986, 564; D. J.
Cardenus, J.-P. Sauvage, Synlett, 1996, 916.
[16] Y. Yamamoto, A. Yanagi, Chem. Pharm. Bull. 1982, 30, 1731.
[17] The related 2,6-bis(tributylstannyl)pyridine has also been prepared by
electrophilic stannylation from the corresponding dilithiopyridine.
The yields, however, were lower: G. S. Hanan, U. S. Schubert, D.
Á
Volkmer, E. Riviere, J.-M. Lehn, N. Kyritsakas, J. Fischer, Can. J.
Chem. 1997, 75, 169.
‡
(70 eV, EI): m/z (%): 866 (42.61), 865 (100.00) [M ], 781 (17.66), 780 (36.31)
[18] This holds true for all other stannyls in this paper all well. For the
toxicity of stannyl compounds, see: A. G. Davies, P. J. Smith,
Comprehensive Organometalic Chemistry (Ed.: E. W. Abel), Perga-
mon, Oxford, 1982, 2, 608.
‡
‡
‡
[M
C6H13], 766 (14.04), 765 (39.65) [M
OC6H13], 739 (14.04) [M
I‡H]; C41H45I2N3O2 (865.63) calcd C 56.88, H 5.24, N 4.85; found C 57.05, H
5.30, N 4.70.
[19] In analogy to: W. Baker, R. F. Curtis, M. G. Edwards, J. Chem. Soc.
1951, 83.
[20] A. Minato, K. Suzuki, K. Tamao, M. Kumada, J. Chem. Soc. Chem.
Commun. 1984, 511.
[21] Y. Yamamoto, T. Seko, H. Nemoto, J. Org. Chem. 1989, 54, 4734.
[22] W. E. Parham, R. M. Piccirilli, J. Org. Chem. 1977, 42, 257.
[23] F. C. Fischer, E. Havinga, Recl. Trav. Chim. 1965, 84, 439; S. R. L.
Fernando, U. S. M. Maharoof, K. D. Deshayes, T. H. Kinstle, M. Y.
Ogawa. J. Am. Chem. Soc. 1996, 118, 5783.
Acknowledgment
This work was supported by the Deutsche Forschungsgemeinschaft (Sfb
448, Project A1) and the Fonds der Chemischen Industrie and is gratefully
acknowledged.
[24] O. Henze, U. Lehmann, Synthesis, in press.
[25] G. W. Gray, M. Hird, D. Lacey, K. J. Toyne, J. Chem. Soc. Perkin Trans.
2 1989, 2041.
[1] V. Hensel, K. Lützow, J. Jakob, K. Gessler, W. Saenger, A. D. Schlüter,
Angew. Chem. 1997, 109, 2768; Angew. Chem. Int. Ed. Engl. 1997, 36,
2654; V. Hensel, A. D. Schlüter, Chem. Eur. J. 1999, 5, 421.
[26] According to a CAS-online search as of July 20, 1998.
[2] V. Hensel, A. D. Schlüter, Eur. J. Org. Chem., in press.
[3] For some rigid cycles with terpyridine units, see: G. R. Newkome, H.-
W. Lee, J. Am. Chem. Soc. 1983, 105, 5956; J. L. Toner, Tetrahedron
Received: August 3, 1998 [F1284]
Chem. Eur. J. 1999, 5, No. 3
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