Star- and banana-shaped oligomers with a pyrimidine core: Synthesis and light-emitting properties

Article abstract of DOI:10.1002/ejoc.200800139

By using Suzuki-Miyaura cross-coupling reactions we have synthesised a series of star- and banana-shaped oligomers with a pyrimidine unit as the central core and π-conjugated arms consisting of aromatics bearing electron-donor substituents. The position of the arms as well as the nature of their substituents were investigated with a view to accessing compounds that exhibit interesting light-emitting properties. The best fluorescence quantum yields were obtained with banana-shaped pyrimidines substituted with p-(dimethyl-amino)phenyl or 2-furyl groups. Comparison of the optical properties of oligomers with benzene, pyrimidine or s-triazine as the central unit revealed that the pyrimidinic compounds gave the best results. Some of the oligomers synthesised exhibit solvatochromic properties and pH sensibility, which could allow their use as polarity or pH sensors. Wiley-VCH Verlag GmbH & Co. KGaA, 2008.

Full text of DOI:10.1002/ejoc.200800139

FULL PAPER
DOI: 10.1002/ejoc.200800139
Star- and Banana-Shaped Oligomers with a Pyrimidine Core: Synthesis and
Light-Emitting Properties
Sylvain Achelle,[a] Yvan Ramondenc,[a] Francis Marsais,[a] and Nelly Plé*[a]
Keywords: Pyrimidines / Cross-coupling / Conjugation / Solvatochromism / Fluorescence
By using Suzuki–Miyaura cross-coupling reactions we have
synthesised a series of star- and banana-shaped oligomers
with a pyrimidine unit as the central core and π-conjugated
arms consisting of aromatics bearing electron-donor substitu-
ents. The position of the arms as well as the nature of their
substituents were investigated with a view to accessing com-
pounds that exhibit interesting light-emitting properties. The
best fluorescence quantum yields were obtained with
banana-shaped pyrimidines substituted with p-(dimethyl-
amino)phenyl or 2-furyl groups. Comparison of the optical
properties of oligomers with benzene, pyrimidine or s-tri-
azine as the central unit revealed that the pyrimidinic com-
pounds gave the best results. Some of the oligomers synthe-
sised exhibit solvatochromic properties and pH sensibility,
which could allow their use as polarity or pH sensors.
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2008)
internal charge transfer (TICT) excited states is expected
with interesting solvatochromic properties. The aim of this
paper is to present the synthesis and physical properties of
various star- and banana-shaped oligomers with a central
pyrimidine core. The effect of the position of the arms as
well as the nature of their substituents has been investi-
gated. This study is a part of our work dedicated to the use
of diazines as building blocks for the synthesis of organic
molecular materials.[14]
Introduction
Over the past decade there has been considerable interest
in the synthesis and characterisation of conjugated organic
compounds, which are attractive candidates for numerous
applications in various fields, for example, as liquid crys-
tals,[1] components of organic light-emitting devices
(OLEDs) for display and lighting,[2] field-effect transistors
(FETs),[3] single molecular electronics[4] and non-linear op-
tical materials.[5] Fluorescent chromophores, generally
known to have planar and rigid π-conjugated systems, are
also of interest as functional materials in molecular
probes.[6] The advantages of molecular fluorescence for
sensing and switching are very important.[7] Indeed, they
enable high sensitivity in detection, “on–off” switchability,
subnanometre spatial resolution and submillisecond tempo-
ral resolution. Recently, star- and banana-shaped molecules
have become highly interesting as chemical materials with
greatly enhanced physical properties.[8] The incorporation
of a π-deficient heterocycle such as pyridine,[9] s-triazine,[10]
pyrazine,[11] quinoxaline[12] or pyrimidine[13] in the centre
of the backbone of such molecules leads to a significant
enhancement of some of their physical properties such as
mesomorphism, fluorescence and solvatochromism. If the
arms of these oligomers are substituted by donor groups,
fluorescence with internal charge transfer (ICT) or twisted
Results and Discussion
Synthesis
Two general methods for the synthesis of 2,4,6-triaryl-
pyrimidines are described in the literature. The first method
consists in the construction of the pyrimidine ring by con-
densation reactions,[15] the second involves the functionali-
sation of the pyrimidine ring.[13a–16] The advantages of this
latter method are a greater versatility and the use of easily
available starting materials. This led us to carry out the syn-
thesis of various star- and bent-shaped molecules with a
pyrimidine core by Suzuki cross-coupling of the commer-
cially available 2,4,6-trichloropyrimidine. It should be noted
that the π-electron-deficient character of the pyrimidine
ring makes easier the oxidative addition of palladium to a
chlorine–carbon bond without the use of specialised and
expensive ligands.[17] A range of star-shaped triarylpyrimid-
ines were synthesised in good yields under Suzuki condi-
tions with an excess of arylboronic acids (5 equiv.;
Scheme 1).
[a] Laboraroire de Chimie Organique Fine et Hétérocyclique,
UMR 6014 – CNRS, INSA et Université de Rouen, IRCOF
INSA de Rouen,
B. P. 08, 76131 Mont-Saint-Aignan Cedex, France
Fax: +33-2-35522962
E-mail: nelly.ple@insa-rouen.fr
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S. Achelle, Y. Ramondenc, F. Marsais, N. Plé
FULL PAPER
the di- and trifurylpyrimidines 8 and 9 were obtained in
equal amounts, whereas only the 2-chloro-4,6-dithienyl-
pyrimidine (10) was obtained in moderate yield (34%) when
the reaction was performed with 2-thienylboronic acid
(Scheme 3).
The formation of the dithienyl compound 10 can be ex-
plained by the lower stability of the thienylboronic acid and
palladium catalyst poisoning by the sulfur atom of the thio-
phene ring. However, as previously, reaction of 10 with [p-
(methylthio)phenyl]boronic acid under Suzuki conditions
allowed a further cross-coupling reaction with the residual
chlorine atom at C-2 to give 11 in good yield (Scheme 4).
Scheme 1. Reagents and conditions: i) p-RC6H4B(OH)2, [Pd-
(PPh3)4], Cs2CO3, toluene, H2O, ∆, 40 h.
When [4-(dimethylamino)phenyl]boronic acid was used,
despite a large excess of the reagent (5 equiv.), only the
monocoupled compound 5 was obtained. However, when a
further coupling reaction was performed with 5 and a fur-
ther 5 equiv. of boronic acid, the expected 2,4,6-triarylpyr-
imidines 6 and 7 were obtained in good yields (Scheme 2).
This result can be explained by the higher electron-donating
effect of the dimethylamino group, which makes the oxidat-
ive addition of palladium to the carbon–chorine bond more
difficult.
Scheme 4. Reagents and conditions: i) p-MeSC6H4B(OH)2,
[Pd(PPh3)4], Cs2CO3, toluene, H2O, ∆, 40 h.
In order to increase the electronic delocalisation along
each arm, star-shaped oligomers with seven rings were syn-
thesised by reaction of 2,4,6-trichloropyrimidine with (bi-
phenylyl)boronic acids. The lower yields observed are prob-
ably due to difficulties in purifying these oligomers by col-
umn chromatography (Scheme 5).
Scheme 2. Reagents and conditions: i) p-(Me2N)C6H4B(OH)2,
[Pd(PPh3)4], Cs2CO3, toluene, H2O, ∆, 40 h; ii) p-RC6H4B(OH)2,
[Pd(PPh3)4], Cs2CO3, toluene, H2O, ∆, 40 h.
By using this methodology, it is possible to link π-elec-
tron-donor five-membered heterocycles such as furan or
Scheme 5. Reagents and conditions: i) p-RC6H4C6H4B(OH)2,
thiophene to the pyrimidine ring. With 2-furylboronic acid, [Pd(PPh3)4], Cs2CO3, toluene, H2O, ∆, 40 h.
Scheme 3. Reagents and conditions: i) [Pd(PPh3)4], Cs2CO3, toluene, H2O, ∆, 40 h.
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Eur. J. Org. Chem. 2008, 3129–3140

Star- and Banana-Shaped Oligomers with a Pyrimidine Core
Scheme 6. Reagents and conditions: i) [Pd(PPh3)4], Cs2CO3, toluene, H2O, ∆, 40 h.
Following the same procedure, the conjugation could be to the dicoupled compound 22 or 23, respectively, in two
extended by introducing an acetylenic linkage between the steps by successive coupling reactions with 3 equiv. of bor-
two phenyl rings of each arm by reaction of 2,4,6-trichloro- onic acid in each step (Scheme 9).
pyrimidine with the {4-[(4-decyloxyphenyl)ethynyl]phenyl}-
boronic acid (14). Compound 15 was obtained in low yield,
as previously, due to the difficulties of purification
(Scheme 6).
Banana-shaped molecules were obtained by Suzuki
cross-coupling reactions either with 4,6-dichloropyrimidine
or with 2,4,6-trichloropyrididine. By using 2 or 3 equiv. of
arylboronic acid, the diaryl compounds 16–18 were synthe-
sised in good yields (Scheme 7).
Scheme 9. Reagents and conditions: i) p-Me2NC6H4B(OH)2,
[Pd(PPh3)4], Cs2CO3, toluene, H2O, ∆, 24 h; ii) p-Me2NC6H4B-
(OH)2, [Pd(PPh3)4], Cs2CO3, toluene, H2O, ∆, 48 h.
Note that 2,4-bis[4-(dimethylamino)phenyl]pyrimidine (24)
was obtained directly in one step by the coupling of 4 equiv.
of boronic acid with 2,4-dichloropyrimidine (Scheme 10).
Scheme 7. Reagents and conditions: p-RC6H4B(OH)2, [Pd(PPh3)4],
Cs2CO3, toluene, H2O, ∆, 40 h.
A banana-shaped conjugated structure with long alkoxy
groups on the termini with potential liquid crystal proper-
ties was synthesised by a Suzuki cross-coupling reaction of
2,4,6-trichloropyrimidine with (6-octyloxy-3-pyridinyl)bor-
onic acid (19). The reaction was performed with 5 equiv.
of the boronic acid in dioxane for 8 h; compound 20 was
isolated in 54% yield (Scheme 8).
With [4-(dimethylamino)phenyl]boronic acid, reaction
Scheme 10. Reagents and conditions: i) p-Me2NC6H4B(OH)2,
with 4,6-dichloropyrimidine or 2,4,6-trichloropyrididine led [Pd(PPh3)4], Cs2CO3, toluene, H2O, ∆, 40 h.
Scheme 8. Reagents and conditions: i) [Pd(PPh3)2Cl2], dioxane, Na2CO3, ∆, 8 h.
Eur. J. Org. Chem. 2008, 3129–3140
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S. Achelle, Y. Ramondenc, F. Marsais, N. Plé
FULL PAPER
The presence of a chlorine atom at the 2-position allows and reaction of 10 with sodium 2-hydroxyethoxide gave the
the easy replacement of chlorine by other groups by nucleo- derivative 26. This last compound, which possesses an al-
philic substitution. Reaction of 17 with sodium methoxide coholic function, could be used to form links with polymers
led to 2-methoxy-4,6-bis(4-methoxyphenyl)pyrimidine (25), or various biocompounds (Scheme 11).
In order to improve the electron-attracting character of
the pyrimidine core, incorporation of a phenyl group bear-
ing an electron-withdrawing substituent could be envisaged.
A Suzuki cross-coupling reaction with p-(trifluoromethyl-
phenyl)boronic acid was carried out on the residual chlo-
rine atom at the 2-position of compound 23 to give com-
pound 27 in good yield (Scheme 12).
With the aim of evaluating the effect of the central core
on the physical properties of such oligomers, analogous ba-
nana- or star-shaped molecules with a benzene or triazine
ring as the central core were synthesised. Compound 28,
analogous to 7 but with an s-triazine central core, was ob-
tained by a Suzuki coupling reaction of cyanuric chloride
with [4-(dimethylamino)phenyl]boronic acid (Scheme 13).
Structures analogous to compounds 1 and 13 with a ben-
Scheme 11. Reagents and conditions: i) MeONa/MeOH, 60 °C,
zene ring as the central core were obtained by cyclotrimeri-
24 h; ii) HOCH2CH2ONa/HOCH2CH2OH, 15 h, room temp.
zation of para-substituted acetophenones with silicon tetra-
chloride,[18] leading to compounds 29 and 30 (analogous to
1). A further Suzuki coupling reaction of the tribromide
derivative 29 with [p-(dimethylamino)phenyl]boronic acid
afforded compound 31 (analogous to 13) (Scheme 14).
The banana-shaped compound 32, analogous to 22 with
a benzene core, was obtained by Suzuki coupling reaction
of 1,3-dibromobenzene with [4-(dimethylamino)phenyl]-
boronic acid (Scheme 15).
Scheme 12. Reagents and conditions: i) p-F3CC6H4B(OH)2,
[Pd(PPh3)4], Cs2CO3, toluene, H2O, ∆, 40 h.
Scheme 15. Reagents and conditions: i) p-Me2NC6H4B(OH)2,
[Pd(PPh3)4], Cs2CO3, toluene, H2O, ∆, 24 h.
Geometric and Electronic Properties
The X-ray crystal structure of 1 is shown in Figures 1
and 2.[19] Single crystals of 1 suitable for X-ray analysis were
Scheme 13. Reagents and conditions: i) p-Me2NC6H4B(OH)2,
[Pd(PPh3)4], Cs2CO3, toluene, H2O, ∆, 24 h.
obtained by slow evaporation at room temperature from a
Scheme 14. Reagents and conditions: i) SiCl4, EtOH, room temp., 15 h; ii) p-Me2NC6H4B(OH)2, [Pd(PPh3)4], Cs2CO3, toluene, H2O, ∆,
24 h.
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Star- and Banana-Shaped Oligomers with a Pyrimidine Core
mixed solvent of chloroform/heptane (1:4). As shown in
Quantum mechanical calculations by DFT methods at
Figure 1, it can be observed that compound 1 is slightly the B3LYP level of theory with the 6-31G* basis set were
twisted; the dihedral angle between the pyrimidine central performed to determine the geometries and electronic struc-
core and the benzene ring at the 2-position is 3.58°, whereas tures of compounds 1 and 29. For compound 1, there is
the dihedral angles between the pyrimidinic central core generally a good agreement between the calculated and X-
and the benzene rings at the 4- and 6-positions are 13.05 ray experimental bond lengths; the mean discrepancies are
and 13.93°, respectively. These angles are sufficiently small less than 3%. However, the dihedral angles determined by
for the conjugation along the three arms of the molecule calculation correlate poorly with the experimental values:
to be preserved. Compound 1 crystallises in the form of a the calculated dihedral angle between the pyrimidine core
monoclinic array with the following parameters: a = 9.17, and the benzene ring at the 2-position (4.26°) is similar to
b = 14.43, c = 15.60 Å, α = 90.00, β = 103.15, γ = 90.00° the experimental value (3.58°), whereas those calculated be-
(Figure 2).
tween the pyrimidine central ring and the benzene rings at
the 4- and 6-positions (respectively, 17.07 and 18.32°) are
much higher than the experimentally determined values.
The results of the calculations performed for compound 30,
analogous to compound 1 with a benzene ring as the cen-
tral core, gave a value of about 38° for the dihedral angles
between the central benzene ring and those in the arms.
The high values of these dihedral angles are due to steric
hindrance between the ortho hydrogen atoms.
The electron-attracting nature of the pyrimidine ring and
the geometry of compound 1 allow high charge transfer
between the donor methoxy groups and the central core,
whereas the geometry of compound 30 reduces the amount
of charge transfer.
The energy levels of the HOMOs and LUMOs for com-
pounds 1 and 30 (Table 1) show a narrower HOMO–
LUMO gap for 1 than for 30.
Table 1. HOMO and LUMO energies and dipole moments for
compounds 1 and 30 from quantum mechanical calculations.
Compd.
HOMO
[eV]
LUMO
[eV]
∆EHOMO–
ʈµʈ [debye]
[eV]
LUMO
1
30
–6.61
–6.72
–1.31
–0.55
5.30
6.17
2.00
2.22
Figure 1. Molecular structure of compound 1 with the atomic
labelling scheme. Selected bond lengths [Å]: C(1)–C(17) 1.483,
C(2)–C(11) 1.501, C(1)–C(5) 1.479, C(1)–N(2) 1.355, N (2)-C(2)
1.361, C(2)–C(3) 1.314, C(3)–C(4) 1.332, C(4)–N(1) 1.400, N(1)–
C(1) 1.364.
Solution Electrochemical Properties
The redox properties of some of these compounds,
studied by cyclic voltammetry (CV) in dry deoxygenated
dichloromethane solution, are given in Table 2.
Table 2. Redox properties determined by cyclic voltammetry.
Compound
E1/2 [V][a]
E1/2 [V][a]
red
ox
2
–2.75 (R)
–2.55 (R)
–3.00 (R)
–2.80 (R)
–2.85 (R)
–2.85 (R)
–2.45 (R)
–1.35 (R),
–2.70 (R)
–2.70 (R)
–2.85 (R)
–2.95 (R)
–
–
–
4
5
6
+0.25 (NR)
+0.40 (NR)
–
7
8
9
–
11
+0.70 (NR)
13
16
23
+0.45 (NR)
–
+0.30 (NR)
[a] Potential values measured vs. Ag/Ag+ and standardised in com-
parison to Fc/Fc+. 1 m sample in dichloromethane/0.1 
Bu4NPF6 (20 °C), scan rate: 0.1 V/s, 20 °C. R indicates a reversible
peak and NR a non-reversible peak.
Figure 2. Crystal structure of 1.
Eur. J. Org. Chem. 2008, 3129–3140
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S. Achelle, Y. Ramondenc, F. Marsais, N. Plé
FULL PAPER
All the compounds showed a quasi-reversible reduction Table 3. Optical absorption and emission spectroscopic data for
compounds with a pyrimidine core in chloroform solution (10–4–
peak between –1.35 and –3.00 V. Non-reversible oxidation
peaks were only observed for the compounds substituted
10–7 ) at 25 °C.
[a]
Compound
λabs,max
[nm]
ε [–1cm–1]
λem,max
[nm]
ΦF
Stokes shift
[cm–1]
by strong electron-donating groups such as dimethylamino
groups (compounds 6, 7, 13 and 23) between +0.25 and
+0.45 V as well as for compound 11 at +0.70 V. For the
other compounds, determination of the Eox potentials,
which could be at much more positive potential values and
out of the range of the electrochemical transparency of
dichloromethane, was impossible.
1
2
4
5
6
7
8
9
296
297
321
382
269
349
352
302
339
314
323
366
348
29734
31277
51663
67965
61226
39286
26476
47284
18277
26177
64959
75772
66578
372
387
398
438
306
427
382
386
386
415
409
495
422
365
0.04[b]
0.04[b]
0.14[b]
0.34[b]
0.53[b]
0.14[c]
0.62[b]
0.17[b]
0.42[b]
0.04[c]
0.54[b]
0.57[c]
0.48[c]
0.04[b]
6902
7830
6027
3347
4495
5234
2231
7206
3592
7751
6510
7120
5039
3951
10
11
12
Absorption and Fluorescence Properties
The UV/Vis and fluorescence spectroscopic data of vari- 13
15
16
ous oligomers measured in chloroform at 25 °C are summa-
rised in Tables 3 and 4.
269/298/ 19692/23678/
319
317
323
27744
26306
25491
All the compounds collected in Table 3 have a pyrimidine
core; their absorption wavelengths (λabs) are in the UV re-
gion (269–394 nm) and their emission wavelengths (λem) in
the UV or blue region (306–495 nm). Star-shaped com-
pounds with one benzene ring per arm (compounds 1, 2
and 4) substituted by alkoxy or sulfanyl groups exhibit ab-
sorption and emission wavelengths in the UV region (λabs
= 296–321 nm, λem = 372–398 nm) with low quantum
yields. In the case of the unsymmetrical compound 6, with
a 4-(dimethylamino)phenyl group at the 4-position, we ob-
served lower λabs and λem values, a lower Stokes shift and a
marked increase in the quantum yield (ΦF = 0.53). When
each arm bears a p-(dimethylamino)phenyl group (com-
pound 7), higher λabs and λem values were observed, this
bathochromic shift due to the high electron-donating char-
acter of the dimethylamino group, with a decrease in ΦF.
Generally, when higher λabs and λem values are observed the
fluorescence quantum yield ΦF decreases, so, in order to
have the best fluorescence properties (high quantum yields
ΦF, large Stokes shifts), it seems important to find a com-
promise between the number and the strength of the periph-
eral electron-donor groups.
18
20
22
23
24
27
364
368
429
441
465
429
0.03[b]
0.18[b]
0.72[b]
0.57[c]
0.06[c]
0.39[c]
4073
3786
3145
2705
6743
3286
299/378 16025/38060
394
354
376
58182
50085
30739
[a] Ϯ10%. [b] Quantum yield of fluorescence determined using 2-
aminopyridine in 0.1  H2SO4 as standard (ΦF = 0.60),[20] exci-
tation at 299 nm. [c] Quantum yield of fluorescence determined
using harmane in 0.1  H2SO4 as standard (ΦF = 0.83),[20] exci-
tation at 366 nm.
donating substituent at the 2-position of the central pyrim-
idine core causes an notable increase in ΦF (0.72). Compari-
son of the data for compounds 22 and 23 reveals that the
presence of the chlorine atom in compound 23 lowers the
value of ΦF (0.57). The position of the two arms at the 2,4-
or the 4,6-positions is of high importance as compound 24,
disubstituted at the 2,4-positions, has a very low ΦF (0.06).
Thus, it seems that the presence of a strongly electron-do-
nating arm at the 2-position of pyrimidine is unfavourable
for a high quantum yield. The spectroscopic data for 27
compared with 22 show that incorporation of an electron-
attracting substituent at the 2-position does not increase the
fluorescence properties.
The star-shaped pyrimidinic compounds 12 and 13 (with
a biphenyl unit per arm) have higher values of λabs, λem and
ΦF than the analogous compounds 2 and 7 (with only one
benzene ring per arm). The bathochromic effect observed is
due to the extension of the conjugation. Comparison be-
tween compounds 12 and 15 reveals that incorporation of a
triple bond between the benzene rings does not significantly
influence the optical properties.
Comparison of the spectroscopic data for compounds 30,
31 and 32 with a benzene core (Table 4) with the analogous
compounds 1, 13 and 22 with a pyrimidine central unit
Table 4. Optical absorption and emission spectroscopic data for
benzenic and triazinic compounds in chloroform solution (10–4–
10–7 ) at 25 °C.
Banana-shaped compounds 8 and 10 with electron-do-
[a]
nor groups such as thienyl or furyl groups have λabs and Compd. λabs,max
ε
λem,max
[nm]
ΦF
Stokes shift
[cm–1]
[nm]
[–1 cm–1]
λem wavelengths in the UV region with high ΦF values of
28
30
31
32
368
270
333
309
62411
52298
33795
29190
419
367
416
0.15[b]
0.04[c]
0.21[c]
–
3308
9789
5992
–
0.62 and 0.42, respectively, whereas their Stokes shifts are
relatively low.
Note that replacement in compounds 8 and 10 of the
chlorine atom at the 2-position with an electron-donor aro-
matic fragment leads to compounds 9 and 11 which have
low ΦF (0.17 and 0.04).
[d]
–
[a] Ϯ10%. [b] Quantum yield of fluorescence determined using har-
mane in 0.1  H2SO4 as standard (ΦF = 0.83),[20] excitation at
366 nm. [c] Quantum yield of fluorescence determined using 2-ami-
nopyridine in 0.1  H2SO4 as standard (ΦF = 0.60),[20] excitation
When the banana-shaped compound 22 is compared
with the star-shaped compound 7, the lack of a electron- at 299 nm. [d] Compound 31 in not fluorescent.
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Star- and Banana-Shaped Oligomers with a Pyrimidine Core
(Table 3) enable us to appreciate the effect of the central
For compound 22, the solvatochromic properties
core. Replacement of the benzene by a pyrimidine ring (Table 6) indicate that λabs and λem increase with the po-
causes a bathochromic effect and increases significantly the larity of the solvent, but unlike the case of compound 13,
value of ΦF in the case of compounds 13 and 22, whereas the ΦF quantum yield increases with the polarity of the
compounds 30 and 1 with p-methoxyphenyl substituents solvent from a non-polar solvent (heptane, ε = 1.9) to a
have similar optical properties (λabs, λem and ΦF). The triaz- moderately polar solvent (chloroform, ε = 4.7), but with a
inic compound 28 and the pyrimidinic compound 7 can be high polar solvent (DMF, ε = 37.5) an unexpected decrease
compared and have similar values for λabs, λem and ΦF. in ΦF is observed. This indicates that two solvatochromic
However, the Stokes shift is superior in the case of the pyr- effects (negative and positive) coexist.[21]
imidinic compound 7.
Table 6. Optical absorption and emission spectroscopic data for
The pyrimidinic compound 13 exhibits fluorosolvatoch-
romism; its absorption and emission spectra in various sol-
vents are shown in Figure 3 and the data are summarised
in Table 5.
compound 22 in various solvents (10–4–10–7 ) at 25 °C.
[a]
Solvent
λabs,max
[nm]
λem,max
[nm]
ΦF
Stokes shift
[cm–1]
Heptane
Chloroform
DMF
275/363
299/374
378
393
429
470
0.42[b]
0.72[b]
0.63[b]
2103
3428
5178
[a] Ϯ10%. [b] Quantum yield of fluorescence determined using 2-
aminopyridine in 0.1  H2SO4 as standard (ΦF = 0.60),[19] exci-
tation at 299 nm.
The effect of protonation on the optical properties of
compounds 7 and 13 was also studied (Table 7). The ab-
sorption maxima λabs slightly decrease or remain constant,
whereas the emission maxima λem dramatically increase
when TFA is added to a chloroform solution. Significant
Stokes shifts (superior to 10000 cm–1) are observed, whereas
at the same time a decrease in the fluorescence quantum
yield ΦF is noted. A similar tendency is observed for the
quantum yield of compound 22. The spectroscopic data for
compound 5 are quite different: protonation does not mod-
ify the absorption and emission profiles but causes an in-
crease in the fluorescence quantum yield. These variations
in the fluorescence properties indicate an important modifi-
cation of the electronic state of the chromophores and/or
of the mechanism by which fluorescence is generated. The
spectroscopic data for compound 8 are unaltered after ad-
dition of TFA to the chloroform solution. In this case, only
the pyrimidine ring can be protonated, which does not lead
to a modification of the spectroscopic data. The modifica-
tions of the spectroscopic data observed during the proton-
ation of compounds 5, 7 and 13 bearing one or more di-
Figure 3. Normalised absorbance and emission (dotted line) spec-
tra of compound 13 in various solvents.
Table 5. Optical absorption and emission spectroscopic data for
compound 13 in various solvents (10–4–10–7 ) at 25 °C.
[a]
Solvent
λabs,max
[nm]
λem,max
[nm]
ΦF
Stokes shift
[cm–1]
Heptane
Chloroform
Acetone
DMF
359
366
363
378
377
427
495
552
573
0.77[b]
0.57[b]
0.14[b]
0.04[b]
Ͻ 0.01
4436
7120
9432
9003
–
[c]
Methanol
–
[a] Ϯ10%. [b] Quantum yield of fluorescence determined using 2-
aminopyridine in 0.1  H2SO4 as standard (ΦF = 0.60),[20] exci-
tation at 299 nm. [c] Compound 13 is not fluorescent in methanol.
A slight bathochromic shift of the absorption maximum
is observed when going from non-polar n-heptane (ε = 1.9)
to polar aprotic DMF (ε = 36.7): ∆λabs = 19 nm (positive
solvatochromism); the variation of the emission maximum
is more important (∆λem = 146 nm) and is associated with
a large increase in the Stokes shift. It should be noted that
the fluorescence quantum yield ΦF dramatically decreases
as the polarity of the solvent increases to become almost
null in methanol. This means that the dipole moment of the
molecule is higher in the excited state than in the ground
state, which indicates its aptitude for charge transfer in the
excited state. The fact that solvatochromism is more impor-
tant for emission than for absorption suggests that the
molecule is more solvated in the excited state than in the
ground state,[21] which implies charge transfer from the di-
methylamino groups to the π-deficient pyrimidine central
ring.
Table 7. Optical absorption and emission data in chlroform solu-
tion (10–4–10–7 ) with addition of TFA at 25 °C; data obtained
without the addition of TFA are given in parentheses.
[a]
Compd. λabs,max
λem,max
[nm]
ΦF
Stokes shift
[cm–1]
[nm]
5
382 (382) 431 (438)
350 (349) 539 (427)
351 (352) 383 (382)
300 (366) 512 (495)
484 (374) 530 (429)
0.77[b] (0.34[b]
)
2976 (3347)
10019 (5234)
2380 (2231)
13802 (7120)
1793 (3145)
7
0.11[c] (0.14[d]
)
8
13
22
0.62[b] (0.62[b]
0.15[b] (0.57[b]
0.17[d] (0.72[b]
)
)
)
[a] Ϯ10%. [b] Quantum yield of fluorescence determined using 2-
aminopyridine in 0.1  H2SO4 as standard (ΦF = 0.60),[19] exci-
tation at 299 nm. [c] Quantum yield of fluorescence determined
using fluorescein in 0.1  NaOH as standard (ΦF = 0.79),[19] exci-
tation at 442 nm. [d] Quantum yield of fluorescence determined
using harmane in 0.1  H2SO4 as standard (ΦF = 0.83),[19] exci-
tation at 366 nm.
Eur. J. Org. Chem. 2008, 3129–3140
© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
3135

S. Achelle, Y. Ramondenc, F. Marsais, N. Plé
FULL PAPER
1
(72%) of 1 as a pale-yellow solid; m.p. 182 °C (ref.[15a] 174 °C). H
methylamino groups could be due to protonation of the
nitrogen atom of the amino group and thus compounds 7
and 13 are pH sensors.
NMR (300 MHz, CDCl3): δ = 3.82 (s, 6 H, OCH3), 3.85 (s, 3 H,
OCH3), 7.01–6.97 (m, 6 H, Ph-H), 7.72 (s, 1 H, 5-H), 8.17 (d, J =
8.8 Hz, 4 H, Ph-H), 8.62 (d, J = 8.8 Hz, 2 H, Ph-H) ppm. 13C
NMR (75 MHz, CDCl3): δ = 55.8, 108.2, 114.0, 114.5, 129.1, 130.4,
130.6, 131.6, 162.0, 162.1, 164.1 ppm. IR: ν = 1606, 1510, 1364,
˜
Conclusions
1242, 1175, 1021, 844, 787 cm–1. C25H22N2O3 (398.16): calcd. C
75.36, H 5.57, N 7.03; found C 75.02, H 5.36, N 6.83.
By using Suzuki–Miyaura cross-coupling reactions we
have synthesised a series of star- and banana-shaped oligo-
mers with a pyrimidine as the central core and arms con-
sisting of aromatic groups bearing electron-donating sub-
stituents. The position of the arms as well as the nature of
their substituents were investigated with a view to accessing
compounds with interesting light-emitting properties. The
best fluorescence quantum yields were obtained with the
banana-shaped pyrimidines substituted with 4-(dimeth-
ylamino)phenyl or 2-furyl groups. Comparison of the op-
tical properties of oligomers with benzene, pyrimidine or s-
triazine as the central unit showed that the best results were
obtained for the pyrimidinic compounds. Some of the
oligomers synthesised exhibit solvatochromic properties
and pH sensibility, which could allow their use as polarity
or pH sensors.
2,4,6-Tris(4-decyloxyphenyl)pyrimidine (2): Suzuki cross-coupling
reaction of 2,4,6-trichloropyrimidine (250 mg, 1.4 mmol) with (4-
decyloxyphenyl)boronic acid (1.38 g, 7.0 mmol) according to the
general procedure (t = 40 h) gave after purification by column
chromatography [silica gel, eluent heptane/ethyl acetate (9:1)]
858 mg (79%) of 2 as a colourless solid; m.p. 70 °C. 1H NMR
(300 MHz, CDCl3): δ = 0.87 (t, J = 6.0 Hz, 9 H, 3ϫCH3), 1.42–
1.22 (m, 42 H, 21ϫCH2), 1.79–1.74 (m, 6 H, 3ϫOCH2CH2), 3.97
(t, J = 6.6 Hz, 4 H, OCH2), 4.02 (t, J = 6.6 Hz, 2 H, OCH2), 7.01–
6.97 (m, 6 H, Ph-H), 7.72 (s, 1 H, 5-H), 8.17 (d, J = 8.8 Hz, 4 H,
Ph-H), 8.62 (d, J = 8.8 Hz, 2 H, Ph-H) ppm. 13C NMR (75 MHz,
CDCl3): δ = 13.1, 27.7, 25.0, 28.2, 28.3, 28.4, 28.5, 28.6, 30.9, 66.8,
67.0, 106.5, 113.1, 113.6, 125.6, 127.0, 128.9, 129.1, 160.2, 162.6,
164.8 ppm. IR: ν = 2920, 2851, 1608, 1586, 1510, 1284, 1173,
˜
825 cm–1. C52H76N2O3 (776.59): calcd. C 80.36, H 9.86, N 3.60;
found C 80.99, H 10.02, N 3.55.
2,4,6-Tris(4-trimethylsilanylphenyl)pyrimidine (3): Suzuki cross-
coupling reaction of 2,4,6-trichloropyrimidine (500 mg, 2.7 mmol)
with [4-(trimethylsilanyl)phenyl]boronic acid[22] (2.90 g, 15 mmol)
according to the general procedure (t = 40 h) gave after purification
by column chromatography [silica gel, eluent heptane/ethyl acetate
(9:1)] 1.22 g (86%) of 3 as a colourless solid; m.p. 142 °C. 1H NMR
(300 MHz, CDCl3): δ = 0.27 [s, 27 H, Si(CH3)3], 7.66–7.61 (m, 6
H, Ph-H), 7.85 (s, 1 H, 5-H), 8.15 (d, J = 8.1 Hz, 4 H, Ph-H), 8.64
(d, J = 7.9 Hz, 2 H, Ph-H) ppm. 13C NMR (75 MHz, CDCl3): δ =
0.3, 111.5, 127.5, 128.8, 134.6, 135.0, 139.0, 139.7, 144.4, 144.8,
Experimental Section
General: Melting points were determined on an Electrothermal
1100 instrument. The 1H, 13C and 19F NMR spectra were recorded
with a Bruker AC 300 (300 MHz 1H, 75 MHz 13C, 282.5 MHz 19F)
instrument. Microanalyses were performed with a Carlo Erba
CHNOS 1160 apparatus. The IR spectra were obtained as potas-
sium bromide pellets with a Perkin-Elmer 16 PC FT-IR spectrome-
ter. Mass spectra were recorded with an ATI-Unicam Automass®
apparatus. UV/Vis spectra were obtained with a Varian Can 50
scan spectrophotometer in chloroform solution. Fluorescence spec-
troscopic studies were performed in chloroform solution in a semi-
micro fluorescence cell (Hellma®, 104F-QS, 10ϫ4 mm, 1400 µL)
with a Varian Cary Eclipse spectrophotometer. Fluorescence quan-
tum yields were determined by comparison with standards, as de-
scribed in literature.[19] Cyclic voltammetry was performed with a
Metrohm PGSTAT 100 potentiostat with a Pt auxiliary electrode,
a 100 micron diameter Pt working electrode and a double junction
Ag/AgCl reference electrode.
165.7 ppm. IR: ν = 2953, 1576, 1516, 1362, 1247, 1100, 857,
˜
821 cm–1. C31H40N2Si3 (524.25): calcd. C 70.93, H 7.68, N 5.34;
found C 70.87, H 7.61, N 5.35.
2,4,6-Tris(4-methylsulfanylphenyl)pyrimidine (4): Suzuki cross-
coupling reaction of 2,4,6-trichloropyrimidine (300 mg, 1.6 mmol)
with [4-(methylsulfanyl)phenyl]boronic acid (1.4 g, 8.1 mmol) ac-
cording to the general procedure (t = 40 h) gave after purification
by column chromatography [silica gel, eluent heptane/ethyl acetate
(9:1)] 596 mg (82%) of 4 as a colourless solid; m.p. 134 °C. 1H
NMR (300 MHz, CDCl3): δ = 2.45 (s, 6 H, 2ϫSCH3), 2.46 (s, 3
H, SCH3), 7.27–7.24 (m, 6 H, Ph-H), 7.72 (s, 1 H, 5-H), 8.05 (d, J
General Procedure A for Cross-Coupling Reactions Under Suzuki = 8.6 Hz, 4 H, Ph-H), 8.48 (d, J = 8.7 Hz, 2 H, Ph-H) ppm. 13C
Conditions: A mixture of chloropyrimidine (or bromobenzene) de-
rivatives, arylboronic acid, tetrakis(triphenylphosphane)palla-
dium(0) (0.05 equiv. per coupling reaction), caesium carbonate
(1 equiv. per coupling reaction), aqueous 2  potassium carbonate
(1 equiv. per coupling reaction.) and ethanol (1.5 mL) in degassed
toluene (20 mL) was heated at reflux under nitrogen for a time t.
The reaction mixture was cooled, diluted with a mixture of water
and ethyl acetate (20 mL, 1:1) and the organic layer separated. The
aqueous layer was extracted with ethyl acetate (3ϫ20 mL). The
combined organic extracts were dried with magnesium sulfate and
the solvents evaporated.
NMR (75 MHz, CDCl3): δ = 15.6, 109.1, 126.0, 126.3, 127.8, 129.1,
134.2, 135.2, 142.1, 142.7, 164.2 ppm. IR: ν = 1578, 1556, 1514,
˜
1491, 1362, 1088, 817, 776 cm–1. C25H22N2S3 (446.09): calcd. C
67.23, H 4.96, N 6.27, S 21.54; found C 67.41, H 5.21, N 6.32, S
21.39.
2,6-Dichloro-4-[4-(dimethylamino)phenyl]pyrimidine (5): Suzuki
cross-coupling reaction of 2,4,6-trichloropyrimidine (1 g,
5.4 mmol) with [4-(dimethylamino)phenyl]boronic acid (1.31 g,
8 mmol) according to the general procedure (t = 40 h) gave after
purification by recrystallisation in methylcyclohexane 1.18 g (81%)
1
of 5 as a yellow solid; m.p. 183 °C. H NMR (300 MHz, CDCl3):
2,4,6-Tris(4-methoxyphenyl)pyrimidine (1): Suzuki cross-coupling
reaction of 2,4,6-trichloropyrimidine (803 mg, 4.40 mmol) with (4-
methoxyphenyl)boronic acid (3.87 g, 22.1 mmol) according to the
general procedure (t = 40 h) gave after purification by column
chromatography [silica gel, eluent heptane/ethyl acetate (9:1)] 1.28 g
δ = 3.07 [s, 6 H, N(CH3)2], 6.68 (d, J = 9.0 Hz, 2 H, Ph-H), 7.42
(s, 1 H, 5-H), 7.94 (d, J = 9.0 Hz, 2 H, Ph-H) ppm. 13C NMR
(75 MHz, CDCl3): δ = 40.5, 111.9, 113.0, 121.0, 129.5, 153.5, 161.3,
162.1, 168.2 ppm. IR: ν = 1606, 1557, 1532, 1500, 1402, 1372, 1339,
˜
1261, 1199, 1123, 813 cm–1. MS (IC+): m/z (%) = 268 (100)
3136
www.eurjoc.org
© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2008, 3129–3140

Star- and Banana-Shaped Oligomers with a Pyrimidine Core
[MH]+, 270 (13) [MH]+, 272 (64) [MH]+. C12H11Cl2N3 (268.14):
calcd. C 53.75, H 4.13, N 15.67; found C 53.72, H 4.13, N 15.63.
2-(4-Methylsulfanylphenyl)-4,6-di(2-thienyl)pyrimidine (11): Suzuki
cross-coupling reaction of 10 (100 mg, 0.36 mmol) with (4-methyl-
sulfanylphenyl)boronic acid (1.1 g, 8.1 mmol) according to the ge-
neral procedure (t = 40 h) gave after purification by recrystalli-
sation in heptane 120 mg (91%) of 11 as a yellow solid; m.p.
192 °C. 1H NMR (300 MHz, CDCl3): δ = 2.59 (s, 3 H, SCH3), 7.22
(dd, J1 = 4.9, J2 = 3.8 Hz, 2 H, 4’-H), 7.39 (d, J = 8.8 Hz, 2 H,
Ph-H), 7.58 (dd, J1 = 4.9, J2 = 1.0 Hz, 2 H, 5’-H), 7.69 (s, 1 H, 5-
H), 7.91 (dd, J1 = 3.8, J2 = 1.0 Hz, 2 H, 3’-H) 8.56 (d, J = 8.8 Hz,
2 H, Ph-H) ppm. 13C NMR (75 MHz, CDCl3): δ = 15.7, 106.7,
126.0, 126.3, 127.5, 128.7, 129.1, 130.2, 134.4, 142.5, 143.6,
4-[4-(Dimethylamino)phenyl]-2,6-bis(4-methoxyphenyl)pyrimidine
(6): Suzuki cross-coupling reaction of 5 (100 mg, 0.37 mmol) with
(4-methoxyphenyl)boronic acid (281 mg, 1.85 mmol) according to
the general procedure (t = 40 h) gave after purification by column
chromatography [silica gel, eluent petroleum ether/ethyl acetate
(8:2)] 120 mg (75%) of 6 as an orange solid; m.p. 157 °C. 1H NMR
(300 MHz, CDCl3): δ = 3.00 [s, 6 H, N(CH3)2], 3.84 (s, 3 H, OCH3),
3.87 (s, 3 H, OCH3), 6.76 (d, J = 9 Hz, 2 H, Ph-H), 7.04–7.00 (m,
4 H, Ph-H), 7.74 (s, 1 H, 5-H), 8.22–8.16 (m, 4 H, Ph-H), 8.67 (d,
J = 9.0 Hz, 2 H, Ph-H) ppm. 13C NMR (75 MHz, CDCl3): δ =
40.4, 40.6, 55.8, 108.3, 114.0, 114.6, 125.3, 128.1, 129.0, 129.1,
159.8 ppm. IR: ν = 1575, 1557, 1524, 1365, 822, 716, 702 cm–1.
˜
C19H14N2S3 (366.52): calcd. C 62.26, H 3.85, N 7.64, S 26.25;
found C 62.60, H 3.61, N 7.41, S 25.93.
130.4, 131.0, 132.0, 152.5, 163.7, 164.1, 164.5 ppm. IR: ν = 1609,
˜
1568, 1510, 1363, 1245, 1170 cm–1. C26H25N3O2 (411.19): calcd. C
75.89, H 6.12, N 10.21; found C 75.85, H 6.09, N 10.15.
2,4,6-Tris[4Ј-(decyloxy)biphenyl-4-yl]pyrimidine (12): Suzuki cross-
coupling reaction of 2,4,6-trichloropyrimidine (103 mg, 0.55 mmol)
with [4Ј-(decyloxy)biphenyl-4-yl]boronic acid (990 mg, 2.79 mmol)
according to the general procedure (t = 40 h) gave after purification
by column chromatography [silica gel, eluent heptane/ethyl acetate
(9:1)] and by recrystallisation in methylcyclohexane 293 mg (53%)
of 12 as a pale-yellow solid; m.p. 191 °C. 1H NMR (300 MHz,
CDCl3): δ = 0.87 (t, J = 6.0 Hz, 9 H, 3ϫCH3), 1.42–1.22 (m, 42 H,
21ϫCH2), 1.79–1.74 (m, 6 H, 3ϫOCH2CH2), 3.92 (t, J = 6.6 Hz, 6
H, 3ϫOCH2), 7.07 (d, J = 8.8 Hz, 6 H, Ph-H), 7.68 (d, J = 8.8 Hz,
6 H, Ph-H), 7.78 (d, J = 8.8 Hz, 6 H, Ph-H), 8.06 (s, 1 H, 5-H),
8.35 (d, J = 8.8 Hz, 4 H, Ph-H), 8.82 (d, J = 8.8 Hz, 2 H, Ph-
H) ppm. 13C NMR (75 MHz, CDCl3): δ = 14.5, 23.1, 26.5, 29.7,
29.8 (2 C), 29.9, 30.0, 32.2, 68.5, 110.0, 115.2, 127.0, 127.4, 128.1,
128.6, 129.3, 132.9, 133.4, 136.1, 136.9, 143.2, 143.5, 159.6,
2,4,6-Tris[4-(dimethylamino)phenyl]pyrimidine (7): Suzuki cross-
coupling reaction of 5 (100 mg, 0.37 mmol) with [4-(dimeth-
ylamino)phenyl]boronic acid (305 mg, 1.85 mmol) according to the
general procedure (t = 40 h) gave after purification by column
chromatography [silica gel, eluent petroleum ether/ethyl acetate
1
(8:2)] 108 mg (67%) of 7 as a red solid; m.p. Ͼ250 °C. H NMR
(300 MHz, CDCl3): δ = 3.06 [s, 18 H, N(CH3)2], 6.85–6.81 (m, 6
H, Ph-H), 7.73 (s, 1 H, 5-H), 8.22 (d, J = 9.1 Hz, 4 H, Ph-H), 8.63
(d, J = 9.0 Hz, 2 H, Ph-H) ppm. 13C NMR (75 MHz, CDCl3): δ =
40.7, 40.8, 106.2, 112.0, 112.3, 126.2, 127.5, 128.8, 130.0, 152.3,
163.9, 165.0 ppm. IR: ν = 1610, 1570, 1523, 1361, 1193, 1169,
˜
810 cm–1. C28H31N5 (437.26): calcd. C 76.85, H 7.14, N 16.00;
found C 76.55, H 6.98, N 16.09.
164.7 ppm. IR: ν = 2923, 2852, 1604, 1574, 1497, 1248, 1192,
˜
821 cm–1. C70H88N2O3 (1004.68): calcd. C 83.62, H 8.82, N 2.79;
found C 83.61, H 8.79, N 2.81.
2-Chloro-4,6-di(furan-2-y)pyrimidine (8) and 2,4,6-Tri(furan-2-yl)-
pyrimidine (9): Suzuki cross-coupling reaction of 2,4,6-trichloropyr-
imidine (634 mg, 3.46 mmol) with (furan-2-yl)boronic acid (1.93 g,
17.3 mmol) according to the general procedure (t = 40 h) gave after
purification by column chromatography [silica gel, eluent heptane/
ethyl acetate (9:1)] 348 mg (41%) of 8 and 410 mg (43%) of 9 both
2,4,6-Tris[4Ј-(dimethylamino)biphenyl-4-yl]pyrimidine (13): Suzuki
cross-coupling reaction of 2,4,6-trichloropyrimidine (143 mg,
0.78 mmol) with (4Ј-decyloxybiphenyl-4-yl)boronic acid (937 mg,
3.0 mmol) according to the general procedure A (t = 40 h) gave
after purification by recrystallisation in methylcyclohexane 195 mg
1
as colourless solids. 8: M.p. 188 °C (ref.[23] 187–188 °C). H NMR
(300 MHz, CDCl3): δ = 6.64 (dd, J1 = 1.7, J2 = 3.6 Hz, 2 H, 4’-H),
7.41 (d, J2 = 3.6 Hz, 2 H, 5Ј-H), 7.67 (d, J1 = 1.7 Hz, 2 H, 3’-H),
7.85 (s, 1 H, 5-H) ppm. 13C (75 MHz, CDCl3): δ = 106.8, 113.3,
1
(39%) of 13 as a yellow solid; m.p. Ͼ250 °C. H NMR (300 MHz,
CDCl3): δ = 3.05 (s, 18 H, NCH3), 6.87 (d, J = 8.8 Hz, 6 H, Ph-
H), 7.65 (d, J = 8.8 Hz, 6 H, Ph-H), 7.78 (d, J = 8.8 Hz, 6 H, Ph-
H), 8.06 (s, 1 H, 5-H), 8.38 (d, J = 8.8 Hz, 4 H, Ph-H), 8.80 (d, J
= 8.8 Hz, 2 H, Ph-H) ppm. 13C NMR (75 MHz, CDCl3): δ = 40.9,
41.0, 109.7, 113.1, 126.5, 126.8, 128.0, 128.2, 128.5, 129.0, 129.3,
114.5, 146.3, 151.1, 158.5, 161.9 ppm. IR: ν = 1608, 1548, 1482,
˜
1265, 756 cm–1. C12H7ClN2O2 (246.02): calcd. C 58.43, H 2.86, N
1
11.36; found C 58.35, H 2.69, N 11.20. 9: M.p. 168 °C. H NMR
(300 MHz, CDCl3): δ = 6.64 (m, 3 H, 4Ј- and 4ЈЈ-H), 7.41 (d, J2 =
3.4 Hz, 2 H, 5’-H), 7.43 (d, J2 = 3.4 Hz, 1 H, 5’’-H), 7.66 (d, J1 =
1.7 Hz, 2 H, 3’-H), 7.68 (d, J1 = 1.7 Hz, 1 H, 3’’-H), 7.78 (s, 1 H,
5-H) ppm. 13C NMR (75 MHz, CDCl3): δ = 106.2, 112.4, 112.9,
135.6, 136.5, 143.5, 143.8, 150.6, 150.7, 164.7, 164.8 ppm. IR: ν =
˜
1603, 1501, 1361, 1200, 1166, 811, 787 cm–1. C46H43N5 (665.35):
calcd. C 82.97, H 6.51, N 10.52; found C 83.02, H 6.40, N 10.64.
113.0, 114.1, 145.4, 145.5, 152.3, 152.6, 156.6, 158.2 ppm. IR: ν =
˜
2,4,6-Tris{4-[4-(decyloxyphenyl)ethynyl]phenyl}pyrimidine (15): Su-
zuki cross-coupling reaction of 2,4,6-trichloropyrimidine (166 mg,
0.91 mmol) with 14[24] (1.72 g, 4.55 mmol) according to the general
1608, 1535, 1486, 1006, 760, 739 cm–1. C16H10N2O3 (278.0): calcd.
C 69.06, H 3.62, N 10.07; found C 68.96, H 3.75, N 9.95.
2-Chloro-4,6-di(2-thienyl)pyrimidine (10): Suzuki cross-coupling re-
action of 2,4,6-trichloropyrimidine (300 mg, 1.63 mmol) with 2-thi-
enylboronic acid (1.1 g, 8.1 mmol) according to the general pro-
cedure (t = 40 h) gave after purification by column chromatography
[silica gel, eluent heptane/ethyl acetate (9:1)] 155 mg (34%) of 10
as a yellow solid; m.p. 191 °C (ref.[23] 195–196°°C). 1H NMR
(300 MHz, CDCl3): δ = 7.20 (dd, J1 = 4.9, J2 = 3.8 Hz, 2 H, 4’-H),
procedure A (t = 40 h) gave after purification by column
chromatography [silica gel, eluent heptane/ethyl acetate (9:1)],
recrystallisation in a mixture of methylcyclohexane and ethyl ace-
tate and washings with toluene 157 mg (16%) of 15 as an orange
solid; m.p. 64 °C. 1H NMR (300 MHz, CDCl3): δ = 0.87 (t, J =
6.0 Hz, 9 H, 3ϫCH3), 1.42–1.22 (m, 42 H, 21ϫCH2),1.79–1.74
(m, 6 H, 3ϫOCH2CH2), 3.97 (t, J = 6.6 Hz, 6 H, OCH2), 6.90 (d,
7.59 (dd, J1 = 4.9, J2 = 1.0 Hz, 2 H, 5’-H), 7.67 (s, 1 H, 5-H), 7.87 J = 8.9 Hz, 6 H, Ph-H), 7.53–7.51 (d, J = 8.9 Hz, 6 H, Ph-H), 7.69
(dd, J1 = 3.8, J2 = 1.0 Hz, 2 H, 3’-H) ppm. 13C NMR (75 MHz,
CDCl3): δ = 106.3, 127.5, 127.6, 130.1, 139.6, 160.4, 160.8 ppm.
(d, J = 8.9 Hz, 6 H, Ph-H), 8.01 (s, 1 H, 5-H), 8.27 (d, J = 8.9 Hz,
4 H, Ph-H), 8.69 (d, J = 8.9 Hz, 2 H, Ph-H) ppm. 13C NMR
IR: ν = 1573, 1490, 1434, 1259, 714 cm–1. C H ClN S (277.97): (75 MHz, CDCl3): δ = 14.5, 23.1, 26.4, 29.6, 29.7, 29.8, 29.9, 30.0,
˜
12
7
2 2
calcd. C 51.70, H 2.53, N 10.05, S 23.00; found C 51.61, H 2.60,
N 10.03, S 22.78.
32.3, 68.5, 88.2, 88.7, 91.9, 92.4, 114.9, 115.0, 115.1, 115.3, 126.4,
126.7, 127.5 (2 C), 128.7, 132.3 (2 C), 133.6 (2 C), 138.8, 137.7,
Eur. J. Org. Chem. 2008, 3129–3140
© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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3137

S. Achelle, Y. Ramondenc, F. Marsais, N. Plé
FULL PAPER
159.8, 159.9, 164.3 (2 C) ppm. IR: ν = 2923, 2853, 2213, 1578, C30H41ClN4O2 (524.29): calcd. C 68.62, H 7.87, N 10.67; found C
˜
1514, 1248, 830 cm–1. MS (IC+): m/z (%) = 1078 (100) [MH]+. 68.41, H 7.60, N 10.90.
C76H88N2O3 (1076.68): calcd. C 84.71, H 8.23, N 2.60; found C
85.06, H 8.46, N 2.41.
6-Chloro-4-[4-(dimethylamino)phenyl]pyrimidine (21): Suzuki cross-
coupling reaction of 4,6-dichloropyrimidine (300 mg, 1.29 mmol)
with [4-(dimethylamino)phenyl]boronic acid (639 mg, 3.87 mmol)
according to the general procedure (t = 24 h) gave after purification
by column chromatography [silica gel, eluent petroleum ether/ethyl
acetate (9:1)] 156 mg (52%) of 21 as a yellow solid; m.p. 182 °C.
1H NMR (300 MHz, CDCl3): δ = 3.06 [s, 6 H, N(CH3)2], 6.74 (d,
J = 9.0 Hz, 2 H, Ph-H), 7.58 (s, 1 H, 5-H), 7.98 (d, J = 9.0 Hz, 2
H, Ph-H), 8.88 (s, 1 H, 2-H) ppm. 13C NMR (75 MHz, CDCl3): δ
4,6-Bis(4-methoxyphenyl)pyrimidine (16): Suzuki cross-coupling re-
action of 4,6-dichloropyrimidine (300 mg, 2.0 mmol) with (4-meth-
oxyphenyl)boronic acid (607 mg, 4.0 mmol) according to the gene-
ral procedure (t = 40 h) gave after purification by column
chromatography [silica gel, eluent petroleum ether/ethyl acetate
(5:5)] 456 mg (78%) of 16 as a colourless solid; m.p. 148 °C. 1H
NMR (300 MHz, CDCl3): δ = 3.90 (s, 6 H, OCH3), 7.04 (d, J =
9.0 Hz, 4 H, Ph-H), 7.98 (d, J = 1.1 Hz, 1 H, 5-H), 8.12 (d, J =
9.0 Hz, 4 H, Ph-H), 9.22 (d, J = 1.1 Hz, 1 H, 2-H) ppm. 13C NMR
(75 MHz, CDCl3): δ = 55.8, 111.4, 114.7, 129.0, 129.9, 159.4, 162.3,
= 40.6, 109.7, 112.2, 124.9, 128.6, 152.5, 159.2, 164.1 ppm. IR: ν =
˜
1610, 1556, 1456, 1199, 1105, 822, 752 cm–1. C12H12ClN3 (233.70):
calcd. C 61.67, H 5.18, N 17.98; found C 61.58, H 5.23, N 17.82.
164.3 ppm. IR: ν = 1600, 1590, 1575, 1510, 1405 cm–1. C H N O
˜
18 16
2
2
4,6-Bis[4-(dimethylamino)phenyl]pyrimidine (22): Suzuki cross-
coupling reaction of 21 (300 mg, 1.29 mmol) with [4-(dimeth-
ylamino)phenyl]boronic acid (659 mg, 4.0 mmol) according to the
general procedure (t = 40 h) gave after purification by column
chromatography [silica gel, eluent petroleum ether/ethyl acetate
(8:2)] 311 mg (76%) of 22 as an orange solid; m.p. 172 °C. 1H
NMR (300 MHz, CDCl3): δ = 3.08 [s, 12 H, N(CH3)2], 6.81 (d, J
= 9.0 Hz, 4 H, Ph-H), 7.92 (d, J = 1.1 Hz, 1 H, 5-H), 8.08 (d, J =
9.0 Hz, 4 H, Ph-H), 9.13 (d, J = 1.1 Hz, 1 H, 2-H) ppm. 13C NMR
(75 MHz, CDCl3): δ = 40.5, 112.1, 115.2, 122.5, 129.0, 153.1,
(292.33): calcd. C 73.95, H 5.52, N 9.58; found C 73.81, H 5.29, N
9.68.
2-Chloro-4,6-bis(4-methoxyphenyl)pyrimidine (17): Suzuki cross-
coupling reaction of 2,4,6-trichloropyrimidine (367 mg, 2.0 mmol)
with (4-methoxyphenyl)boronic acid (607 mg, 4.0 mmol) according
to the general procedure (t = 40 h) gave after purification by
recrystallisation in methylcyclohexane and ethyl acetate 450 mg
(69%) of 17 as an ivory solid; m.p. 182 °C (ref.[25] 187–189°°C). 1H
NMR (300 MHz, CDCl3): δ = 3.90 (s, 6 H, OCH3), 7.04 (d, J =
9.0 Hz, 4 H, Ph-H), 7.88 (s, 1 H, 5-H), 8.12 (d, J = 9.0 Hz, 4 H,
Ph-H) ppm. 13C NMR (75 MHz, CDCl3): δ = 55.9, 109.4, 114.7,
159.1 ppm. IR: ν = 1608, 1574, 1524, 1439, 1362, 1182, 819 cm–1.
˜
C20H22N4 (318.42): calcd. C 75.44, H 6.96, N 17.60; found C 75.31,
H 7.12, N 17.37.
128.5, 129.4, 160.7, 162.9, 167.1 ppm. IR: ν = 1584, 1575, 1512,
˜
1259, 1234, 1175, 825 cm–1. C18H15ClN2O2 (326.08): calcd. C
66.16, H 4.63, N 8.57; found C 66.22, H 4.70, N 8.70.
2-Chloro-4,6-bis[4-(dimethylamino)phenyl]pyrimidine (23): Suzuki
cross-coupling reaction of 5 (300 mg, 1.12 mmol) with [4-(dimeth-
ylamino)phenyl]boronic acid (221 mg, 1.34 mmol) according to the
general procedure (t = 40 h) gave after purification by column
chromatography [silica gel, eluent petroleum ether/ethyl acetate
(95:5)] 252 mg (64%) of 23 as a yellow solid; m.p. 172 °C. 1H NMR
(300 MHz, CDCl3): δ = 3.08 [s, 12 H, N(CH3)2], 6.77 (d, J = 9.0 Hz,
4 H, Ph-H), 7.77 (s, 1 H, 5-H), 8.06 (d, J = 9.0 Hz, 4 H, Ph-H) ppm.
13C NMR (75 MHz, CDCl3): δ = 40.5, 107.4, 112.0, 123.5, 129.0,
2-Chloro-4,6-bis(4-butylphenyl)pyrimidine (18): Suzuki cross-coup-
ling reaction of 2,4,6-trichloropyrimidine (149 mg, 0.81 mmol) with
(4-butylphenyl)boronic acid (430 mg, 2.43 mmol) according to the
general procedure (t = 40 h) gave after purification by column
chromatography [silica gel, eluent petroleum ether/dichlorometh-
ane (7:3)] 233 mg (76%) of 18 as a colourless solid; m.p. 54 °C. 1H
NMR (300 MHz, CDCl3): δ = 0.90 (t, J = 8 Hz, 6 H, CH3), 1.40–
1.28 (m, 4 H, CH2), 1.64–1.54 (m, 4 H, CH2), 2.63 (t, J = 7.7 Hz,
4 H, CH2), 7.25 (d, J = 8.2 Hz, 2 H, Ph-H), 7.80 (s, 1 H, 5-H), 7.98
(d, J = 8.2 Hz, 2 H, Ph-H) ppm. 13C NMR (75 MHz, CDCl3): δ
= 14.4, 22.8, 33.8, 36.0, 110.5, 127.7, 129.5, 133.5, 147.5, 162.3,
152.8, 160.6, 166.9 ppm. IR: ν = 2937, 1557, 1518, 1413, 1223,
˜
1185, 818 cm–1. C20H21ClN4 (352.15): calcd. C 68.08, H 6.00, N
15.88; found C 69.37, H 6.16, N 15.63.
2.4-Bis[4-(dimethylamino)phenyl]pyrimidine (24): Suzuki cross-
coupling reaction of 2,4-dichloropyrimidine (209 mg, 1.40 mmol)
with [4-(dimethylamino)phenyl]boronic acid (924 mg, 5.60 mmol)
according to the general procedure (t = 40 h) gave after purification
by column chromatography [silica gel, eluent petroleum ether/ethyl
167.7 ppm. IR: ν = 2952, 2930, 1588, 1501, 1233, 1065, 828 cm–1.
˜
MS (IC+): m/z (%) = 378 (100) [M]+, 379 (27) [M]+, 380 (33)
[M]+. C24H27ClN2 (378.19): calcd. C 76.07, H 7.18, N 7.39; found
C 76.15, H 7.09, N 7.45.
1
acetate (9:1)] 311 mg (70%) of 24 as a beige solid; m.p. 252 °C. H
2-Chloro-4,6-bis[6-(octyloxy)pyridin-3-yl]pyrimidine (20): A mixture
of [6-(octyloxy)pyridin-3-yl]boronic acid (19) (1.1 g, 4.43 mmol),
2,4,6-trichloropyrimidine (161 mg, 0.88 mmol), [Pd(PPh3)2Cl2]
(60 mg, 0.09 mmol) in degassed 1,4-dioxane (10 mL) was stirred at
20 °C for 30 min. A degassed 1  aqueous Na2CO3 solution
(4.4 mL) was added and the reaction mixture was heated under
nitrogen at reflux for 8 h. Solvent was removed in vacuo, ethyl ace-
tate was added and the organic layer was washed with brine, sepa-
rated and dried with MgSO4. The mixture was purified by column
chromatography (silica gel, eluent dichloromethane) to give 245 mg
(54%) of 20 as a pale-yellow solid; m.p. Ͻ50 °C. 1H NMR
NMR (300 MHz, CDCl3): δ = 3.06 [s, 6 H, N(CH3)2], 3.07 [s, 6 H,
N(CH3)2], 6.81 (d, J = 9.0 Hz, 4 H, Ph-H), 6.82 (d, J = 9.0 Hz, 4
H, Ph-H), 7.37 (d, J = 5.3 Hz, 1 H, 5-H), 8.17 (d, J = 9.0 Hz, 4 H,
Ph-H), 8.48 (d, J = 9.0 Hz, 4 H, Ph-H), 8.64 (d, J = 5.3 Hz, 1 H,
6-H) ppm. 13C NMR (75 MHz, CDCl3): δ = 39.2, 110.4, 110.6,
110.8, 123.6, 125.1, 127.3, 128.4, 151.0 151.2, 159.8, 162.3,
163.4 ppm. IR: ν = 1608, 1574, 1524, 1439, 1362, 1182, 819 cm–1.
˜
C20H22N4 (318.42): calcd. C 75.44, H 6.96, N 17.60; found C 75.09,
H 6.69, N 17.83.
2-Methoxy-4,6-bis(4-methoxyphenyl)pyrimidine (25): A solution of
(300 MHz, CDCl3): δ = 0.77 (t, J = 6.6 Hz, 6 H, CH3), 1.35–1.15 sodium methoxide prepared with Na (51 mg, 2.24 mmol) in meth-
(m, 20 H, 10ϫCH2), 1.71–1.67 (m, 4 H, 2ϫCH2), 4.25 (t, J =
6.7 Hz, 4 H, OCH2), 6.71 (d, J = 8.6 Hz, 2 H, 5’-H), 7.69 (s, 1 H,
5-H), 8.20 (d, J = 8.6 Hz, 2 H, 4’-H), 8.74 (s, 2 H, 2Ј-H) ppm. 13C
anol (15 mL) was added dropwise to 17 (180 mg, 1.12 mmol) in
methanol (5 mL) at 0 °C. The mixture was allowed to stir at 60 °C
during 24 h and then hydrolysed with water (20 mL). The methanol
NMR (75 MHz, CDCl3): δ = 14.5, 23.0, 26.4, 29.3, 29.6, 29.7, 32.2, was evaporated in vacuo, the aqueous layer extracted with dichloro-
67.2, 108.6, 111.8, 124.8, 137.7, 147.3, 162.4, 164.5, 166.6 ppm. IR: methane (3ϫ20 mL) and the combined organic extracts dried with
ν = 2927, 2856, 1604, 1579, 1493, 1397, 1290, 1234, 832 cm–1. magnesium sulfate and the solvents evaporated. The residue was
˜
3138
www.eurjoc.org
© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2008, 3129–3140

Star- and Banana-Shaped Oligomers with a Pyrimidine Core
purified by column chromatography [silica gel, eluent petroleum
TFA): δ = 47.7, 121.0, 125.8, 128.2, 128.5, 129.7, 138.4, 141.5,
ether/ethyl acetate (9:1)] to give 328 mg (91%) of 25 as a beige
solid; m.p. 134 °C. H NMR (300 MHz, CDCl3): δ = 3.84 (s, 6 H,
141.6, 142.2, 143.8 ppm. IR: ν = 1610, 1503, 1441, 1355, 1212,
˜
1
1196, 809, 754 cm–1. C48H45N3 (663.89): calcd. C 86.84, H 6.83, N
OCH3), 4.12 (s, 3 H, OCH3), 7.00 (d, J = 9 Hz, 4 H, Ph-H), 7.61 6.33; found C 86.91, H 6.81, N 6.39.
(s, 1 H, 5-H), 8.10 (d, J = 8.9 Hz, 4 H, Ph-H) ppm. 13C (75 MHz,
1,3-Bis[4Ј-(dimethylamino)phenyl]benzene (32): Suzuki cross-coup-
CDCl3): δ = 55.0, 55.8, 105.1, 114.5, 129.2, 129.8, 162.3, 166.5 (2
C) ppm. IR: ν = 1511, 1257, 1169, 1019, 825 cm–1. C H N O
3
ling reaction of 1,3-dibromobenzene (300 mg, 1.30 mmol) with [4-
(dimethylamino)phenyl]boronic acid (825 mg, 5.0 mmol) according
to the general procedure (t = 24 h) gave after purification by col-
umn chromatography [silica gel, eluent petroleum ether/ethyl ace-
tate (9:1)] 343 mg (83%) of 32 as a beige solid; m.p. 196 °C. 1H
NMR (300 MHz, CDCl3): δ = 3.03 (s, 12 H, NCH3), 6.85 (d, J =
8.7 Hz, 4 H, Ph-H), 7.49–7.46 (m, 3 H, Ph-H), 7.59 (d, J = 8.7 Hz,
4 H, Ph-H), 7.78 (s, 1 H, Ph-H) ppm. 13C NMR (75 MHz, CDCl3):
δ = 41.0, 113.2, 124.6, 124.9, 128.2, 129.4, 129.9, 142.0, 150.4 ppm.
˜
19 18
2
(322.13): calcd. C 70.79, H 5.63, N 8.69; found C 71.11, H 5.48, N
8.72.
2-[4,6-Di(2-thienyl)pyrimidin-2-yloxy]ethanol (26): NaH (60%) in a
mineral oil dispersion (50 mg, 1.25 mmol) was added to ethylene
glycol (5 mL) in an ice bath. After 5 min, 10 (27 mg, 0.1 mmol) was
added and the mixture was allowed to stir at room temperature
overnight, acidified with 10% aqueous HCl, diluted with H2O and
extracted twice with EtOAc (10 mL). The combined organic ex-
tracts were washed with H2O and brine, dried with MgSO4 and
concentrated in vacuo. The residue was purified by column
chromatography [silica gel, eluent petroleum ether/ethyl acetate
IR: ν = 1610, 1534, 1480, 1349, 1229, 1206, 708 cm–1. C H N
˜
22 24
2
(316.44): calcd. C 83.50, H 7.64, N 8.85; found C 83.71, H 7.79, N
8.54.
1
(9:1)] to give 15 mg (50%) of 26 as a beige solid; m.p. 108 °C. H
Acknowledgments
NMR (300 MHz, CDCl3): δ = 4.10–4.07 (m, 2 H, CH2), 4.69–4.66
(m, 2 H, CH2), 7.20 (dd, J1 = 4.9, J2 = 3.8 Hz, 2 H, 4’-H), 7.54 (s,
1 H, 5-H), 7.58 (dd, J1 = 4.9, J2 = 1.0 Hz, 2 H, 5’-H), 7.87 (dd, J1
= 3.8, J2 = 1.0 Hz, 2 H, 3’-H) ppm. 13C NMR (75 MHz, CDCl3):
δ = 62.2, 70.0, 104.0, 128.3, 128.8, 130.7, 142.2, 162.0, 165.6 ppm.
We thank Prof. André-Jean Attias and Dr. David Kreher (UMR
7610-CNRS, Pierre et Marie Curie University) for their collabora-
tion and the cyclic voltammetry experiments, and Prof. Georges
Dupas (UMR 6014-CNRS, IRCOF-INSA Rouen) for the quantum
mechanical DFT calculations.
IR: ν = 3413, 2928, 1580, 1528, 1404, 1347, 1327, 1060, 826,
˜
715 cm–1. C14H12N2O2S2 (304.39): calcd. C 55.24, H 3.97, N 9.20,
S 21.07; found C 55.56, H 4.29, N 8.84, S 20.72.
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4,6-Bis[4-(dimethylamino)phenyl]-2-[4-(trifluoromethyl)phenyl]-
pyrimidine (27): Suzuki cross-coupling reaction of 23 (115 mg,
0.32 mmol) with [4-(trifluoromethyl)phenyl]boronic acid (62 mg,
0.64 mmol) according to the general procedure (t = 40 h) gave after
purification by recrystallisation from methylcyclohexane 134 mg
(92%) of 27 as a colourless solid; m.p. 236 °C. 1H NMR (300 MHz,
CDCl3): δ = 3.07 [s, 12 H, N(CH3)2], 6.83 (d, J = 9.0 Hz, 4 H, Ph-
H), 7.77 (d, J = 9.0 Hz, 2 H, Ph-H), 7.84 (s, 1 H, 5-H), 8.20 (d, J
= 9.0 Hz, 4 H, Ph-H), 8.82 (d, J = 9.0 Hz, 2 H, Ph-H) ppm. 13C
NMR (75 MHz, CDCl3): δ = 39.2, 106.4, 110.8, 123.8, 124.1, 125.2,
127.3, 127.6, 130.3 (q), 141.3, 151.0, 161.4, 162.9 ppm. 19F NMR
(282.5 MHz, CDCl ): δ = –62.9 ppm. IR: ν = 1588, 1567, 1520,
˜
3
1324, 1194, 1167, 1118, 1066, 1017, 809 cm–1. C27H25F3N4 (462.51):
calcd. C 70.12, H 5.45, N 12.11; found C 70.34, H 5.21, N 12.37.
2,4,6-Tris[4-(dimethylamino)phenyl]-1,3,5-triazine (28): Suzuki
cross-coupling reaction of cyanuric chloride (184 mg, 1.0 mmol)
with [4-(dimethylamino)phenyl]boronic acid (825 mg, 5.0 mmol)
according to the general procedure (t = 24 h) gave after purification
by column chromatography [silica gel, eluent petroleum ether/ethyl
1
acetate (7:3)] 184 mg (42%) of 28 as a red solid; m.p. 116 °C. H
NMR (300 MHz, CDCl3): δ = 3.11 [s, 18 H, N(CH3)2], 6.82 (d, J
= 9.0 Hz, 6 H, Ph-H), 8.65 (d, J = 9.0 Hz, 4 H, Ph-H) ppm. 13C
NMR (75 MHz, CDCl3): δ = 40.6, 111.7, 124.9, 130.6, 153.3,
[5] a) M. Albota, D. Beljonne, J.-L. Brédas, J. E. Erhlich, J.-Y. Fu,
A. A. Heikel, S. E. Hess, T. Kogej, M. D. Levin, S. R. Marder,
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170.8 ppm. IR: ν = 3226, 2924, 1494, 1429, 1364, 1193, 1145,
˜
803 cm–1. C27H30N6 (438.25): calcd. C 73.94, H 6.89, N 19.16;
found C 74.26, H 6.98, N 18.89.
1,3,5-Tris[4Ј-(dimethylamino)biphenyl-4-yl]benzene (31): Suzuki
cross-coupling reaction of 29[18] (543 mg, 1.0 mmol) with [4-(di-
methylamino)phenyl]boronic acid (825 mg, 5.0 mmol) according to
the general procedure (t = 24 h) gave after purification by
recrystallisation in chloroform 570 mg (86%) of 31 as a yellow so-
1
lid; m.p. 236 °C. H NMR (300 MHz, CDCl3): δ = 3.03 (s, 18 H,
NCH3), 6.86 (d, J = 8.1 Hz, 6 H, Ph-H), 7.61 (d, J = 8.7 Hz, 6 H,
Ph-H), 7.70 (d, J = 8.1 Hz, 6 H, Ph-H), 7.78 (d, J = 8.4 Hz, 6 H,
Ph-H), 7.89 (s, 3 H, Ph-H) ppm. 13C NMR (75 MHz, CDCl3
+
Eur. J. Org. Chem. 2008, 3129–3140
© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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3139

S. Achelle, Y. Ramondenc, F. Marsais, N. Plé
FULL PAPER
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Received: February 5, 2008
Published Online: May 8, 2008
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Eur. J. Org. Chem. 2008, 3129–3140