One-pot synthesis of oligomeric aryl-substituted PPV analogs with extended π-conjugation

Article abstract of DOI:10.1039/a905710b

A conceptually novel approach for a stepwise one-pot synthesis of oligomeric poly(phenylvinylene) (PPV, -[C₆H₄-CH=CH]-) analogs with extended π-conjugation of the type H-[CH=C(Ar)-C₆H₄-C(Ar)=CH]_n-H (n = 2, 4), from the corresponding dienic monomers (n = 1), has been studied. The oligomerizations were performed in high yields by repeating the sequential preparation of the mercuric trifluoroacetate derivative H-[CH=C(Ar)-C₆H₄-C(Ar)=CH]_n-HgCO₂CF ₃ (n = 1, 2) and its coupling in the presence of PdCl₂. The feasibility of this approach was demonstrated by a one-pot preparation of several tetramers, directly from the corresponding monomers.

Full text of DOI:10.1039/a905710b

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One-pot synthesis of oligomeric aryl-substituted PPV analogs with
extended ꢀ-conjugation
Ben-Ami Feit* and Ludmila Buzhansky
1
Raymond and Beverly Sackler Faculty of Exact Sciences, School of Chemistry,
Tel Aviv University, Tel-Aviv 69978, Israel
Received (in Cambridge, UK) 14th July 1999, Accepted 16th March 2000
A conceptually novel approach for a stepwise one-pot synthesis of oligomeric poly(phenylvinylene) (PPV,
–[C H –CH᎐CH]–) analogs with extended π-conjugation of the type H–[CH᎐C(Ar)–C H –C(Ar)᎐CH] –H (n = 2, 4),
᎐
᎐
᎐
6
4
6
4
n
from the corresponding dienic monomers (n = 1), has been studied. The oligomerizations were performed in high
yields by repeating the sequential preparation of the mercuric trifluoroacetate derivative H–[CH᎐C(Ar)–C H –
᎐
6
4
C(Ar)᎐CH] –HgCO CF (n = 1, 2) and its coupling in the presence of PdCl . The feasibility of this approach was
᎐
n
2
3
2
demonstrated by a one-pot preparation of several tetramers, directly from the corresponding monomers.
Existing methodologies for the construction of mono-dispersed
oligomers consist of a variety of approaches of repetitive multi-
step synthesis.1a All of these approaches involve isolation and
purification of each n-mer obtained (and in many cases, of
intermediate products as well), prior to subjecting it to the
sequence of reactions necessary to convert it to the (n ϩ 1)-mer
or to the (n ϩ 2)-mer.1 An effective and versatile approach for
converting an n-mer to the corresponding (n ϩ 2)-mer, is the
McMurry reaction.1b It has been successfully applied to the
preparation of cyclic sulfur-bridged annulenes1c and related
compounds.1d A one-pot stepwise sequential synthesis of a
mono-dispersed n-mer directly from the monomer, avoiding the
need to isolate each of the intermediate n-mers in a pure form,
has not yet been reported. The advantages and significance of
such an approach are obvious.
reported relevant example, is that of the preparation of a mix-
ture of oligotriacetylenes, and its separation into its pure
oligomeric constituents.3
A novel general strategy for a one-pot sequential synthesis
of mono-dispersed oligomers from bifunctional monomers is
presented here. The synthesis of the above mentioned target
oligomers is to be regarded as a specific example of this general
approach. According to this approach, transformation of each
n-mer (starting always with n = 1) to the (n ϩ 2)-mer consists of
two reactions, carried out consecutively and repeatedly (in one
pot). The first step consists of a monofunctionalization reac-
tion of the non-reactive bifunctional n-mer. The rate constant
(k1) of the reaction yielding this product [eqn. (2)] has to be
k1
H–[CH᎐C(Ar)–Y–C(Ar)᎐CH] –H
᎐
᎐
n
It was our aim to develop a conceptually novel approach to a
fully controlled one-pot sequential synthesis of conjugated olig-
omers, directly from the corresponding monomers. Ongoing
research in our laboratory involves the synthesis and oxidative-
coupling-type polymerization of a new class of conjugated
H–[CH᎐C(Ar)–Y–C(Ar)᎐CH] –Z (2)
᎐
᎐
n
much larger than the rate constant (k2) of the reaction of its
conversion to the bifunctional derivative [eqn. (3)], namely—
dienic monomers of the general type CH ᎐C(Ar)–Y–
᎐
2
k2
C(Ar)᎐CH 2 [eqn. (1)].
H–[CH᎐C(Ar)–Y–C(Ar)᎐CH] –Z
᎐
2
᎐
᎐
n
Z–[CH᎐C(Ar)–Y–C(Ar)᎐CH] –Z (3)
᎐
᎐
n
oxidation
nCH ᎐C(Ar)–Y–C(Ar)᎐CH
᎐
᎐
2
2
Ϫ2nHϩ
k1 ӷ k2, (n = 1, 2, 4, . . .). The second step is an in situ coupling
reaction, k3, of two such monofunctionalized n-mer molecules
to yield the corresponding 2n-mer [eqn. (4)]. It is obvious that in
H᎐[CH᎐C(Ar)᎐Y᎐C(Ar)᎐CH] ᎐H (1)
᎐
᎐
n
Thus, oligomers of the general structure H–[CH᎐C(Ar)–Y–
᎐
C(Ar)᎐CH] –H (n = 2, 4, 8 . . .), to be prepared by a one-pot
sequential synthesis of the nM→(M)n-type, were the target
᎐
k3
n
2 H–[CH᎐C(Ar)–Y–C(Ar)᎐CH] –Z
᎐
᎐
n
oligomers of the research reported here.
H–[CH᎐C(Ar)–Y–C(Ar)᎐CH] –H (4)
᎐
᎐
2n
An oxidative-coupling-type oligomerization based on the
above mentioned polymerization used for these monomers
[eqn. (1)] could in fact be considered as a one-pot reaction.
However, it would have resulted in a mixture of various n-mers,
that would need to be separated from each other. A recently
order for this approach to be applicable, each of these two
consecutive reactions has to take place in a very high yield.
Coupling reactions of symmetrically conjugated dienes of
the type CH ᎐C(Ar)–Y–C(Ar)᎐CH have not been reported,
᎐
᎐
2
2
DOI: 10.1039/a905710b
J. Chem. Soc., Perkin Trans. 1, 2000, 1777–1782
This journal is © The Royal Society of Chemistry 2000
1777

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Table 1 Preparation of Ar1(Ar2)C᎐CH–HgCl 2 from Ar1(Ar2)C᎐CH2 1—experimental conditions and resultsa
᎐
᎐
Hg(CO2CF3)2/
mmol
Product 2,
yield (%)
Mpb/ ЊC
(lit., mp/ ЊC)
Ar1
Ar2
1/mmol
–Ph
–Ph
–Ph
8.6
8.6
8.6
8.6
2a, 58
2b, 67
142
(143)c
133
4.0
5.7
4.0
5.7
2c, 60
2d, 56
146
(146.5)c
–Ph
–Ph
–Ph
125
165d
138
2.4
3.5
2.4
3.5
2e, 60
2k, 65
a The products were prepared according to the general procedure detailed in the Experimental section. b The products were crystallized from benzene.
c See ref. 8. d The product 2e was crystallized from a mixture of petroleum ether–ethyl acetate.
except for the above mentioned case of their oxidative-coupling-
type stepwise polymerization.2 However, several reports are
sponding 1,1,4,4-tetraarylbuta-1,3-dienes 3 in moderate yields.
The experimental conditions and the results obtained are sum-
marized in Table 2. It should be noted that 2k, derived from a
conjugated dienic monomer, was significantly less reactive
compared to the substrates 2a–2e.
available on the coupling of ArCH᎐CH–Z type compounds,
᎐
which could be used for our synthesis [eqn. (5)].
PdX2
The structures of the coupling products, 1,1,4,4-tetraaryl-
buta-1,3-dienes 3a–3e, were determined based on their 1H-
NMR, 13C-NMR and MS spectral data which are detailed in
Table 3.
2 PhCH᎐CH–Z
᎐
PhCH᎐CH–CH᎐CHPh ϩ 2 ZX ϩ Pd(0) (5)
᎐
᎐
2
(Z = –HgCl,5 –B(OH),5 –SiMe3,6 etc.)
The relatively low solubility of the Ar1(Ar2)C᎐CH–HgCl
᎐
type compounds 2 and their high stability, suggested that higher
yields of 3 could have been obtained using its in situ formed
Results and discussion
precursor, Ar1(Ar2)C᎐CH(HgCO CF ), which is soluble and
᎐
2
3
1,1-Diarylethylenes (1) were used as model compounds for the
monofunctionalization of the dienic n-mers (n = 1, 2, 4), and
for the subsequent coupling of the product of this reaction.
The two corresponding reactions applied in this case were the
chloromercuration of 1,1-diarylethylenes to give the derived
Ar1(Ar2)C᎐CH–HgCl 2,4 followed by PdCl -induced coupling
more reactive compared to 2. It was found that a two-step one-
pot synthesis of 3 directly from 1, bypassing the preparation
and isolation of Ar1(Ar2)C᎐CH–HgCl, could be carried out.
᎐
Several variations of experimental conditions for this one-pot
reaction [eqn. (8)] were studied. The optimal experimental con-
ditions found and the results obtained are given in the Table 4.
᎐
2
reaction7 of 2 to yield the corresponding 1,1,4,4-tetraarylbuta-
1,3-diene 3 [eqns. (6) and (7)].
2 Ar1(Ar2)C᎐CH
[Ar1(Ar2)C᎐CH]
(8)
᎐
᎐
2
2
1
3
1. HgX2
Ar1(Ar2)C᎐CH
Ar1(Ar2)C᎐CH–HgX
(6)
᎐
᎐
2
2. NaCl
1
2
The yields of the coupling products 3 obtained in this one-
pot synthesis were much higher than the corresponding ones
PdCl2
obtained by the coupling of Ar1(Ar2)C᎐CH–HgCl.
Ar1(Ar2)C᎐CH–HgX
᎐
᎐
2
The exclusive formation of the monochloromercury deriv-
Ar1(Ar2)C᎐CH–CH᎐C(Ar1)(Ar2) (7)
ative CH ᎐C(Ph)–C H –C(Ph)᎐CH–HgCl 2k, as opposed to
᎐
᎐
᎐
᎐
2
6
4
the corresponding dichloromercury derivative, indicates that
k1 ӷ k2 [eqns. (2) and (3)] for the oligomers H–[CH᎐C(Ar)-
3
᎐
The chloromercurations were carried out at room temper-
ature in benzene. Mercuric trifluoroacetate Hg(TFA)2 was more
efficient than Hg(NO3)2 as a mercurating agent. Equimolar
amounts of Hg(TFA)2 had to be used, since an excess could
result in the formation of by-products of the type Ar1(Ar2)-
C᎐C(HgX) .4 The monohalomercury derivative of the mono-
C H C(Ar)᎐CH] –H, at least for n = 1. Based on this observation
᎐
6 4
n
and on the encouraging results obtained for the one-pot dimer-
ization of Ar1(Ar2)C᎐CH 1 [eqn. (8), Table 3], a direct con-
᎐
2
secutive two-step one-pot dimerization of the monomer CH ᎐
᎐
2
C(Ar)–C H –C(Ar)᎐CH 4 to give the dimeric product H–[CH᎐
᎐
᎐
6
4
2
C(Ar)–C H –C(Ar)᎐CH] –H5,wascarriedout.Optimizationof
᎐
᎐
2
6
4
2
meric diene, CH ᎐C(Ph)–C H –C(Ph)᎐CH–HgCl, and several
the experimental conditions [eqn. (9)] led to a relatively short
reaction time (15 min) for each of the two reactions, namely the
in situ formation of the monomercuric trifluoroacetate deriv-
ative of 4 and its coupling to the dimeric product 5. Very high
yields (92–100%) of the dimers 5 were obtained within an over-
all reaction period of 30 min. The experimental conditions and
results are summarized in Table 5. The structures of the dimers
᎐
᎐
2
6
4
Ar1(Ar2)C᎐CH–HgCl type compounds, were prepared from the
᎐
corresponding diene and 1,1-diarylethylenes, respectively. The
experimental conditions and the results obtained are summar-
ized in Table 1.
The coupling of 2 [eqn. (7)] was carried out in benzene in the
presence of stoichiometric amounts of PdCl2, to give the corre-
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J. Chem. Soc., Perkin Trans. 1, 2000, 1777–1782

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Table 2 The preparation of the dimers [Ar1(Ar2)C᎐CH]2 3 by coupling of 2—experimental conditions and resultsa
᎐
PdCl2/
mmol
Reaction
time/h
Product 3,
yield (%)
Mpb/ ЊC
(lit., mp/ ЊC)
Ar1
Ar2
2/mmol
–Ph
–Ph
–Ph
0.34
0.36
0.34
0.36
18
4
3a, 62
3b, 56
207
215
(215)9
2.8
1.1
2.8
1.1
4
3c, 62
3d, 51
157c
(158)10
–Ph
–Ph
–Ph
18
215
0.45
0.48
0.45
0.48
18
18
3e, 60
102–105c
135
5ad,e, f 38
a The products were prepared according to the general procedure detailed in the Experimental section. b The products were crystallized from ethanol.
c The products were crystallized from benzene. d A mixture of THF and HMPA (4 equiv.) was used instead of benzene. e The spectral data of 5a are
given in Table 6. f The yield of 5a after a reaction time of 48 hours was 40%.
Table 3 Spectral data of Ar1(Ar2)C᎐CH–HgCl 2 and [Ar1(Ar2)C᎐CH]2 3
᎐
᎐
Compound
Spectral data
2a
2b
2c
2d
2e
δH 6.33 (1H, s), 6.95–7.33 (10H, m); m/z (EI) 415.9 (Mϩ, 20%), 178.9 ([(Ph2)C᎐CH]ϩ, 100%)
᎐
δH 3.82 (3H, s, OCH3), 6.24 (1H, s), 6.62–7.39 (9H, m); m/z (EI) 445.9 (Mϩ, 20%), 209 ([(Ph)(4-anisyl)C᎐CH]ϩ, 100%)
᎐
δH 3.84 (6H, s, OCH3), 6.22 (1H, s), 6.81–7.61 (8H, m); m/z (EI) 239 ([(4-anisyl)2C᎐CH]ϩ, 100%)
᎐
δH 6.41 (1H, s), 6.45 (1H, s), 7.29–7.95 (24H, m); m/z (EI) 466 (Mϩ, 20%), 229 ([(Ph)(α-naphthyl)C᎐CH]ϩ, 100%)
᎐
δH 3.66 (3H, s, OCH3), 3.86 (3H, s, OCH3), 6.50 (1H, s), 7.26–7.31 (8H, m); m/z (EI) 239 ([(Ph)(2,4-dimethoxyphenyl)C᎐CH]ϩ,
᎐
100%)
2k
3a
3b
3c
3d
3e
3i
δH 3.84 (3H, s, OCH3), 5.46 (1H, d, J 4), 5.48 (1H, d, J 4), 6.45 (1H, s), 7.2–7.4 (14H, m); δC 114.6 (C᎐CH2), 127.9–129.6 (14C,
᎐
Ar-CH), 136.4 (2C, C-C), 141.1 (C-C), 141.6 (C-C), 145.0 (C-C), 149.3 (C-C), 158.0 (C-Hg); m/z (EI) 518 (Mϩ, 100%)
δH 6.75 (2H, s), 7.23–7.45 (20H, m); δC 126.03 (2C, ᎐CH-), 127.34–128.25 (18C, Ar-CH), 130.7 (4C, C-C), 140.01 (2C, C-C), 142.53
᎐
(2C, C-C), 144.08 (2C, C-C); m/z (EI) 358 (Mϩ, 100%)
δH 3.86 (6H, s, OMe), 6.67–7.41 (20H, m, Ar ϩ vinyl H); δC 55.2 (4C, OMe), 113.5 (2C, ᎐CH2), 127.05, 127.15, 127.3, 127.8, 127.84
᎐
(5C, Ar–CH), 130.6, 131.9, 138.9, 172.4, (4C, C-C, Ar); m/z (EI) 418 (Mϩ, 28%)
δH 3.77 (12H, s, OMe), 6.64–7.50 (18H, m, Ar-H ϩ vinyl H); δC 55.2 (OMe), 113.5 (᎐CH2), 127.1 (4C, CH), 131.2, 141.11, 156.1,
᎐
(C-C, Ar); m/z (EI) 478.4 (Mϩ, 47%) 252.2 ([(4-anisyl)2C᎐CH]ϩ, 100%)
᎐
δH 6.91–7.91 (m, Ar ϩ vinyl H); δC 114.7 (C᎐CH2), 149.9, 148.1, 140.8, 138.8 (5C, C-C), 126.3–136.6 (12C, Ar-CH); m/z (EI) 458.2
᎐
(Mϩ, 100%)
δH 3.63 (6H, s, OMe), 3.81 (6H, s, OMe), 6.49 (2H, s, vinyl H), 7.26–7.28 (16H, m, Ar-H); δC 55.5 (C-OMe), 115.5 (C᎐CH2),
᎐
130.05, 132.10, 134.22, 140.07, 143.10 (5C, C-C), 124.66–128.00 (8C, CH-Ar); m/z (EI) 478 (Mϩ, 5%)
δH 3.83 (6H, s, OMe), 3.90 (6H, s, OMe), 6.69–7.38 (18H, m, Ar ϩ vinyl H); δC 55.9 (OMe), 113.1 (C᎐CH2), 125.8–129.8 (8C,
᎐
Ar-CH), 149.7, 148.8, 148.5, 141.5, 134.3 (5C, C-C); m/z (EI 239 ([(3,4-dimethoxyphenyl)(Ph)C᎐CH]ϩ, 100%)])
᎐
3j
δH 6.66 (2H, s, vinyl H), 7.25–7.60 (28H, m, Ar-H); δC 115.9 (᎐CH2), 126.9–128.8 (8C, Ar-CH), 143.5, 140.3, 138.9, 137.4, 129.8
᎐
(5C, C-C); m/z (EI) 268 ([(biphenyl-4-yl)(phenyl)C᎐CH-CH]ϩ, 100%)
᎐
(9)
5 were determined based on their 1H-NMR, and mass spectral
data, which are detailed in Table 6.
corresponding monomers described in this report, has been
verified and demonstrated quite impressively. This was done
by carrying out a one-pot synthesis of the same tetramers 6,
directly from the corresponding monomers 4, in four consec-
utive steps [eqn. (11)]. The tetramers were obtained in high
yields (86–90%) within an overall reaction time of one hour!
The results are summarized in Table 6.
In conclusion, the feasibility of applying a novel approach to
a consecutive stepwise one-pot synthesis of conjugated oligo-
mers [eqns. (2)–(4)], has been demonstrated. Conjugated
Several of the dimers 5 prepared by the one-pot synthesis
approach, were isolated and further dimerized to the corre-
sponding tetramers 6 in a two-step one-pot synthesis, applying
the same experimental conditions used for preparing these
dimers [eqn. (10)]. The results are summarized in Table 7. The
structure of the tetramers 6 obtained were determined based on
1
their H-NMR and mass spectral data, which are detailed in
Table 6.
The possibility of performing the novel approach for con-
struction of mono-dispersed n-mers (n = 2, 4) directly from the
oligomers of the type H–[CH᎐C(Ar)–C H –C(Ar)᎐CH] –H
᎐ ᎐
6 4 n
(n = 2, 4) were prepared directly from the corresponding
J. Chem. Soc., Perkin Trans. 1, 2000, 1777–1782 1779

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(10)
(11)
(12)
distilled from its mixture with LiAlH4 into the reaction flask.
Table 4 Preparation of [Ar1(Ar2)C᎐CH]2– 3 from Ar1(Ar2)C᎐CH2 1 in
Triethylamine was kept over sodium hydroxide and was distilled
from this mixture before use. PdCl2 (Merck, 99%) was used as
purchased. Mercuric trifluoroacetate was prepared according to
a known procedure11 and dried in a vacuum for 12 hours before
use. The 1,1-diarylethylenes12 and the α,αЈ-diaryl-p-divinyl-
᎐
᎐
a one-pot reaction—experimental conditions and resultsa
Product 3,
mpb/ЊC
yield (%)
lit., mp/ЊC Ar2
Ar1
benzene type compounds CH ᎐C(Ar)–C H –C(Ar)᎐CH were
᎐
᎐
2
6
4
2
3a, 88
3b, 85
3c, 89
3d, 91
207
prepared by a previously described methods2,13 and were dried
in a vacuum before use.
All reactions were carried out in a 100 ml three-neck flask.
The reaction setup consisted of a three-neck flask (100 ml) fit-
ted with a self-sealing rubber septum, equipped with magnetic
stirring and a dry nitrogen inlet. Liquid materials were intro-
duced into the reaction flask using a syringe. All glass parts,
syringes and needles were thoroughly dried at 130 ЊC and
assembled while warm. All the reactions for the synthesis of
the oligomers were carried out under nitrogen in anhydrous
conditions.
215
(215)9
157c
(158)10
215
3e, 92
3i, 64
3j, 59
102–105c
140
A general procedure for the preparation of Ar1(Ar2)C᎐CH–HgCl
(2)
᎐
A modification of a reported procedure8 was used.
A solution of Ar1(Ar2)C᎐CH (3.5–8.6 mmol) and an equiv-
᎐
2
alent amount of mercuric trifluoroacetate in benzene (8–15 ml),
or acetonitrile (8–15 ml), was stirred for 45 min at room tem-
perature. An aqueous solution (2 M) of sodium chloride (40 ml)
was then added and the mixture was further stirred for 1 h. The
solvents were removed and the white solid residue was washed
several times with water and then with hexane. The solid was
extracted with chloroform and filtered. The solvent was
removed from the filtrate. The residue was the practically pure
80
a Experimental conditions for the coupling reaction of 1 to yield 3: 1)
benzene, 0 ЊC, 1 (1 equiv.), Hg(CO2CF3)(2), (1 equiv.), 15 min; 2) PdCl2
(1 equiv.), Et3N (3 equiv.), 15 min at 0 ЊC. b The products were crystal-
lized from ethanol. c The products were crystallized from benzene.
product Ar1(Ar2)C᎐CH–HgCl 2, which was used without
᎐
further purification. This general procedure was used for the
preparation of compounds 2a–2e.
monomers (n = 1) by carrying out
according to the following general sequence of reactions
a
one-pot synthesis
A general procedure for the preparation of the dimers
[Ar1(Ar2)C᎐CH] (3) by coupling of 2
᎐
2
[eqn. (12)].
A modification of a reported procedure7 for the coupling of
Ar1(Ar2)C᎐CH–HgCl 2 was used. Dry benzene (5–20 ml),
᎐
PdCl2 (0.28–1.10 mmol) and a 3–4-fold excess of LiCl were
introduced into a three-neck flask. The mixture was cooled to
0 ЊC and magnetically stirred under nitrogen. To an equivalent
amount of organometallic the reactant 2 was then added, which
caused an immediate color change to dark brown. Stirring
was continued for 4–48 hours. Water, pentane and active
carbon were added, the reaction mixture was shaken and
filtered. The filtrate was extracted with pentane, the organic
layer washed with water, dried over anhydrous magnesium
Experimental
General
1H (200 MHz) and 13C (200 MHz) NMR spectra were obtained
in CDCl3 with SiMe4 as standard; J values are given in Hz.
Benzene (AR) was dried over sodium wire, tetrahydrofuran
(AR) was distilled before use from a colored THF solution of
sodium benzophenone ketyl. Acetonitrile (AR) was distilled
over P2O5 before use. HMPA (AR) was dried by LiAlH4 and
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Table 5 The preparation of H–[CH᎐C(Ar)–C6H4–C(Ar)᎐CH]2–H 5 from the corresponding monomers 4 in a one-pot synthesis—experimental
᎐
᎐
conditions and resultsa
PdCl2/
mmol
Hg(CO2CF3)2/
mmol
Et3N/
mmol
Product 5,
yield (%)
Ar
4/mmol
0.9
0.9
0.9
0.3
0.9
0.52
2.7
5a, 92
5b, 95
5c, 96
5d, 100
0.3
0.3
0.9
0.9
0.9
0.27
1.56
0.52
0.52
0.5
0.5
0.5
1.5
5e, 98
5f, 92
0.25
0.25
0.25
0.75
a The products were prepared according to the general procedure detailed in the Experimental section.
Table 6 Spectral data of the dimers H–[CH᎐C(Ar)–C6H4–C(Ar)᎐CH]2–H 5 and the tetramers H–[CH᎐C(Ar)–C6H4–C(Ar)᎐CH]4–H 6
᎐
᎐
᎐
᎐
Compound
Spectral data
5a
5b
δH 5.67 (2H, d, J 2), 5.71 (2H, d, J 2), 6.58 (2H, d, J 10), 7.48–7.67 (28H, m, Ar-H); m/z (EI) 562.2 (Mϩ, 100%)
δH 1.62 (12H, t, J 4.1, CH3), 2.68 (8H, q, J 4, CH2), 5.29 (2H, d, J 2), 5.43 (2H, d, J 2), 6.32 (2H, d, J 13), 7.16–7.79 (24H, m, Ar-H);
m/z (EI) 674.1 (Mϩ, 35%)
5c
δH 3.62 (12H, s, OMe), 5.38 (2H, d, J 2), 5.42 (2H, d, J 2), 6.25 (2H, d, J 9), 6.63–6.93, 7.21–7.37 (24H, m, Ar-H); m/z (EI) 682.3
(Mϩ, 80%)
5d
5e
δH 5.59 (2H, d, J 2), 5.64 (2H, d, J 2), 6.48 (2H, d, J 10), 7.25–7.98 (38H, m, Ar-H); m/z (FAB) 763.212 ([M ϩ 1]ϩ, 100%)
δH 3.61 (12H, s, OMe), 3.84 (12H, s, OMe), 5.29 (2H, d, J 2), 5.66 (2H, d, J 2), 6.48–6.52, 7.13–7.36 (22H, m, Ar ϩ vinyl H);
m/z (FAB) 803 ([M ϩ 1]ϩ, 10%)
5f
6b
6c
6f
δH 1.16 (12H, t, J 4.1, CH3), 1.63 (8H, m, CH2), 1.82 (8H, m, CH2), 2.62 (8H, t, J 4.3), 5.66 (2H, d, J 2), 5.68 (2H, d, J 2), 6.55 (2H,
d, J 11), 7.35–7.56 (24H, m, Ar-H); m/z (FAB) 787.335 ([Mϩ]ϩ, 100%)
δH 1.24 (24H, t, J 4, CH3), 2.66 (16H, q, J 4.1, CH2), 5.29 (2H, d, J 2), 5.43 (2H, d, J 2), 6.33 (6H, d, J 10), 7.19–7.43 (48H, m,
Ar-H); m/z (FAB) 1347.578 ([M ϩ 1]ϩ, 10%)
δH 3.62 (24H, s, OMe), 5.38 (2H, d, J 2), 5.42 (2H, d, J 2), 6.23 (6H, d, J 11), 6.85–6.92, 7.18–7.43 (48H, m, Ar-H); m/z (EI)
684.2 (100%)
δH 1.16 (24H, t, J 4, CH3), 1.63 (16H, m, CH2), 1.82 (16H, m, CH2), 2.62 (16H, t, J 4.1, CH2), 5.66 (2H, d, J 2), 5.68 (2H, d, J 2),
6.55 (6H, d, J 11), 7.35–7.56 (48H, m, Ar-H); m/z (EI) 1572.381 (Mϩ, 100%)
cedure was used for the preparation of the [Ar1(Ar2)C᎐CH]
type compounds 3a–3e.
Table 7 Preparation of the tetramers H–[CH᎐C(Ar)–C6H4–C(Ar)᎐
CH]4–H 6 from: a) from the dimers 5 in a one-pot synthesis; B) from
the monomers 4 in a one-pot synthesis
᎐
᎐
᎐
2
A general procedure for the preparation of the dimers [Ar1(Ar2)C᎐
᎐
Yield (%)
CH] (3) from Ar1(Ar2)C᎐CH (1) in a one-pot synthesis
᎐
2
2
A
B
Product
Ar
Benzene (10–12 ml) was introduced into a three-neck flask and
cooled to 0 ЊC. To it was added the 1,1-diarylethylene (0.8–1.2
mmol) followed by an equivalent amount of mercuric trifluoro-
acetate, PdCl2, and three equivalents triethylamine. The reac-
tion mixture was stirred for 15 min at 0 ЊC. Methylene chloride,
carbon black and water were added to the reaction mixture,
which was shaken and filtered. The aqueous layer was extracted
with methylene chloride, the organic layers were combined and
dried over anhydrous MgSO4. Column chromatography on
silica gel was applied to the residue after removing the solvent
from the dried extract to yield the corresponding pure 1,1,4,4-
tetraarylbuta-1,3-dienes 3a–3j.
71
86
6b
65
75
89
90
6f
6ca
a The terminal methylene groups of the tetramer 6c underwent reduc-
tion in the column when purified by column chromatography on silica
gel 60; 6c in this reduced form was the product isolated.
A general procedure for preparation of the dimers H–[CH᎐
᎐
C(Ar)–C H –C(Ar)᎐CH] –H (5) from the dienic monomers
᎐
6
4
2
sulfate and filtered. The residue recovered from the filtrate
was purified by column chromatography on silica gel, using
petroleum ether (bp 60–80 ЊC) as eluent. This general pro-
CH ᎐C(Ar)–C H –C(Ar)᎐CH (4)
᎐
᎐
2
6
4
2
The procedure used was the same as that described above under
J. Chem. Soc., Perkin Trans. 1, 2000, 1777–1782 1781

View Article Online
the conditions used for the preparation of the 1,1,4,4-
tetraarylbuta-1,3-dienes of type 3 from 1 in a one-pot synthesis,
except for the use of diene 4 (0.9 mmol) instead of Ar1(Ar2)-
equiv.) was added and the reaction mixture stirred for 15 min.
Palladium chloride (0.58 equiv.) and Et3N (1.5 equiv.) were then
added and stirring continued for 15 min. Work-up of the reac-
tion mixture was done as described for method A. The general
procedures of methods A and B were used for the preparation
of the tetramers 6b, 6c and 6f.
C᎐CH 1. This general procedure was used for the preparation
᎐
2
of the dimers 5a–5f.
A general procedure for preparation of the tetramers
H–[CH᎐C(Ar)–C H –C(Ar)᎐CH] –H (6)
᎐
᎐
6
4
4
References
Method A. Preparation of the tetramers 6 by a one-pot syn-
thesis from the corresponding dimers 5. Benzene (10 ml) was
introduced into a three-neck flask and cooled to 0 ЊC. To it was
added the dimer 5 (0.9 mmol) followed by mercuric trifluoro-
acetate (0.380 g, 0.9 mmol) and the reaction mixture stirred for
15 min at 0 ЊC. PdCl2 (0.150 g, 0.9 mmol) and Et3N (0.370 g, 2.7
mmol) were then added, and the reaction mixture was further
stirred for 15 min at 0 ЊC. The work-up was the same as
described above in the procedure for preparation of 3 via
coupling for 2 except for the use of cyclohexane as eluent
instead of petroleum ether.
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Method B. Preparation of the tetramers 6 by a one-pot syn-
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monomer 4 (0.18–0.58 mmol) was added to benzene (10 ml) in
a three-neck flask and cooled to a temperature of 0 ЊC, which
was maintained throughout the whole synthesis. One equivalent
of mercuric trifluoroacetate was added to this solution and the
mixture was stirred for 15 min. Palladium chloride (1.25 equiv.)
and Et3N (3 equiv.) were then added and stirring was continued
for 15 min. A second portion of mercuric trifluoroacetate (0.5
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1782
J. Chem. Soc., Perkin Trans. 1, 2000, 1777–1782