π-extended conjugate phenylacetylenes. Synthesis of 4-[(E) and (Z)-2-(4-ethenylphenyl)ethenyl]pyridine. Dimerization, quaternation and formation of charge-transfer complexes

Article abstract of DOI:10.1016/S0040-4020(02)01628-9

The conjugate (E)- and (Z)-(4′-pyridylethenyl)-4-phenylethyne (E-4 and Z-4) has been satisfactorily prepared by two different routes: (a) by dehydrohalogenation of 4′-pyridylethenyl-4-phenyl-β-chloroethene; (b) by the Wittig reaction between p-(iodobenzyl)(triphenyl)phosphine ylide and 4-pyridinecarboxaldehyde, E/Z isomer separation, and cross-coupling with 2-methyl-but-3-yn-2-ol followed the propanone elimination. The Glaser oxidative dimerization of (Z)-4 yields (Z,Z)-1,4-di[(4′-pyridylethenyl)-4-phenyl]-buta-1,3-diyne in good yield, (Z,Z)-5. (E,E)-5 was obtained by phase transfer oxidative dimerisation of (E)-4 in presence of their N-methyl salt (E)-10. Mono- and di-N-methylated salts of conjugate (E,E)-5 and (Z,Z)-5, were obtained by quaternation with iodomethane. The (Z,Z)-5 di-N-methylated salt forms charge-transfer complexes with TCNE, TCNQ and TMPD.

Full text of DOI:10.1016/S0040-4020(02)01628-9

Tetrahedron 59 (2003) 1021–1032
p-Extended conjugate phenylacetylenes. Synthesis of 4-[(E) and
(Z)-2-(4-ethenylphenyl)ethenyl]pyridine. Dimerization,
quaternation and formation of charge–transfer complexes
*
J. Gonzalo Rodrıguez, Rosa Martın-Villamil and Antonio Lafuente
´
´
´ ´ ´
Departamento de Quımica Organica, Universidad Autonoma de Madrid, Cantoblanco, 28049-Madrid, Spain
Received 24 September 2002; revised 20 November 2002; accepted 12 December 2002
Abstract—The conjugate (E)- and (Z)-(400-pyridylethenyl)-4-phenylethyne (E-4 and Z-4) has been satisfactorily prepared by two different
routes: (a) by dehydrohalogenation of 4 -pyridylethenyl-4-phenyl-b-chloroethene; (b) by the Wittig reaction between p-(iodobenzyl)-
(triphenyl)phosphine ylide and 4-pyridinecarboxaldehyde, E/Z isomer separation, and cross-coupling with 2-methyl-but-3-yn-2-ol followed
the propanone elimination. The Glaser oxidative dimerization of (Z)-4 yields (Z,Z)-1,4-di[(40-pyridylethenyl)-4-phenyl]-buta-1,3-diyne in
good yield, (Z,Z)-5. (E,E)-5 was obtained by phase transfer oxidative dimerisation of (E)-4 in presence of their N-methyl salt (E)-10. Mono-
and di-N-methylated salts of conjugate (E,E)-5 and (Z,Z)-5, were obtained by quaternation with iodomethane. The (Z,Z)-5 di-N-methylated
salt forms charge–transfer complexes with TCNE, TCNQ and TMPD. q 2003 Elsevier Science Ltd. All rights reserved.
1. Introduction
The discovery of the one-dimensional metallic state in the
ion–radical solid formed from the p-donor tetrathiofulva-
lene (TTF) and the acceptor tetracyanoquinodimethane
(TCNQ) has stimulated the interest for structure–properties
relationship of novel donor and acceptors.7
The use of molecular organic materials for conductor and
non-linear optics applications is an area of considerable
recent activity. Interest in these materials is due to their
inherent synthetic flexibility, which permits the design of
molecular architectures with important properties. Com-
pounds containing the conjugate molecular fragment type
bistyryl are applied as carrier transport agents and electro-
photographic photoreceptors.1a Molecules showing
p-extended conjugation, in general exhibit high thermal
stability and can present electroconductive, magnetic and
optical properties.1b
Metallic conductivity and superconductivity are the
most important properties in these organic charge–
transfer salts. Recently attention has also been directed to
the novel magnetic and optical properties, which can
display.8
In this paper we report the synthesis of (E)- and (Z)-(40-
pyridylethenyl)-4-phenylethyne, the oxidative homo-
coupling to 1,3-butadiynes and the quaternation to give
molecules with strong acceptor character, which enables to
prepare charge–transfer complexes with donor and acceptor
molecules.
Solid state polymerisation of 1,3-diynes to form crystalline
conjugated poly(1,3-diynes) has attracted much attention.1b,2
Some of the recent interest is related to their large and fast
non-linear optical response, making them good potential
materials in ultrafast optical applications.3 Although the
electronic and optical properties of poly(1,3-diynes) are
primarily dominated by the p-conjugated backbone, the
acetylene substituents markedly influence the topopolymer-
isation behaviour and the physical and chemical properties
of the crystalline conjugated poly(1,3-diynes) because,
many of them, are inactive in the solid state,4,5 although
undergo liquid crystal polymerisa0tion. However, pre-
liminary studies show that 4-nitro, 4 -amino diphenyl-1,3-
diyne is solid state reactive.6
2. Results and discussion
2.1. Synthesis of p-extended conjugate phenylacetylene
derivatives
Synthesis of (E)- and (Z)-(40-pyridylethenyl)-4-phenyl-
ethyne (E-4 and Z-4) was outlined in two ways: (a) by
dehydrohalogenation of the appropriate halovinylarene
derivative, (E,E) or (Z,E) or the mixture9 and; (b) by
cross-coupling reaction of the corresponding haloarene with
2-methyl-but-3-yn-2-ol, catalysed by palladium, followed
of propanone elimination.10
Keywords: charge–transfer complex; oxidative dimerization;
dehydrohalogenation.
*
Corresponding author. Tel.: þ34-1397-4715; fax: þ34-1397-3966;
e-mail: gonzalo.rodriguez@uam.es
0040–4020/03/$ - see front matter q 2003 Elsevier Science Ltd. All rights reserved.
PII: S0040-4020(02)01628-9

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1022
2.2. (E)- and (Z)-(40-pyridylethenyl)-4-phenylethyne (4),
by dehydrohalogenation of the halovinylarene
derivatives
good yield, as a mixture of the (E,Z)-3 and (E,E)-3 isomers:
X¼Cl, 60:40, 84%; X¼Br, 53:47, 63%, Scheme 1.
Compounds 4 show structural evidence of the electronic
effect produced by the pyridine ring on the ethylene bridge
(1H NMR, (Z)-4; 6.71 and 6.52 ppm, J¼12.3 Hz) and (E)-4;
7.28 and 7.03 ppm, J¼16.1 Hz). Both isomers exhibit
conjugation of the aromatic rings through the double bond
but this effect is more relevant in the E isomer probably due
to steric hindrance of the aromatic rings in the Z isomer.
The synthesis of the conjugate (E)- and (Z)-(40-pyridyl-
ethenyl)-4-phenylethyne (E-4 and Z-4) was carried out by
dehydrohalogenation of (E,Z)-3 and (E,E)-3 (X¼chloro- or
bromo-) with potassium tert-butoxide in THF at room
temperature 0 and sunlight exposure during 24 h: (E,Z)-3
gives (Z)-(4 -pyridylethenyl)-4-phenylethyne (Z)-4, (66%,
X¼Br); and (E,E)-3 gives (E)-(40-pyridylethenyl)-4-phenyl-
ethyne, (E)-4 (75%, X¼Br). The reaction products and yield
in this elimination are temperature dependent.11 The
dehydrohalogenation in toluene, at the reflux temperature,
results unsuccessful.
2.2.1. From the appropriate haloarene with 2-methyl-
but-3-yn-2-ol catalysed by palladium. Because of the
difficulty in the dehydrohalogenation of the halovinyl
derivatives 3 in toluene, an alternative synthesis of the
stereoisomers of the acetylene 4 has been also outlined.
Hence, the heterocoupling reaction between p-(iodophenyl-
ethenyl)-4-pyridine (E-6 and Z-6) and 2-methyl-but-3-yn-2-
ol, catalysed by palladium, was applied. However, (E)-4-[40-
(pyridylethenyl)-4-phenyl]-4-(2-methyl-but-3-yn-2-ol) (7)
was only obtained from the iodo derivative (E/Z)-6, in
good yield (71%); for X¼Cl or Br, the cross-coupling
reaction was not observed, Scheme 2.
The b-haloethene 3 was obtained starting of p-(20-
halovinyl)toluene (1), which was prepared by reaction of
the halomethylene(triphenyl)phosphine ylide9,12 (X¼Cl or
Br) and p-tolualdehyde in THF, yielding a E/Z mixture (1:1)
(X¼Cl, 61%; X¼Br, 52%), Scheme 1. The mixture (E/Z)-1
was transformed in the phosphonium salt (E)-(b-halo-
ethenyl)-benzyl(triphenyl)phosphonium bromide (E)-2
(X¼Cl, Br), by treatment with NBS and a little amount of
benzoyl peroxide allowing only to the E-isomer of the
bromobenzyl derivative in moderate yield. Hence, during
the reaction, a complete Z!E isomerization takes place,
probably through an addition–elimination mechanism of
the bromine radical.13 Some amount of the starting product
1 was recovered but also only as the E-isomer. The
bromobenzyl derivative was transformed in the phos-
phonium bromide salt E-2 with triphenylphosphine in
toluene at the reflux temperature, (X¼Cl, Br), in excellent
yield. The phosphonium salt (E)-2 permits the preparation
in situ of the corresponding ylide with potassium tert-
butoxide in toluene, which with 4-pyridinecarboxaldehyde
gives 40-(pyridylethenyl)-4-phenyl-b-haloethene (3) in
The E/Z mixture of compound 7 was treated with a catalytic
amount of powdered sodium hydroxide, in toluene at reflux
temperature, to give (E/Z)-4 (1:1) in good yield (70%). Both
isomers (E)-4 and (Z)-4 were isolated by chromatographic
methods.
The isomers mixture of the haloarene E/Z-6 (1:1) was
obtained by the Wittig reaction of the appropriate
p-halobenzyl(triphenyl)phosphonium ylide, prepared in
situ from the corresponding phosphonium salt, and
4-pyridinecarboxaldehyde. The phosphonium salt results
in good yield by reaction of the p-halotoluene with NBS to
give the corresponding p-bromomethylhalobenzene, which
Scheme 1.

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J. G. Rodrıguez et al. / Tetrahedron 59 (2003) 1021–1032
1023
Scheme 2.
was finally treated with triphenylphosphine in toluene at
reflux temperature.
band of CuN and CuC bonds at 2200 cm21, while the free
TCNE shows two bands at 2260 and 2220 cm21 and the free
1,3-diyne at 2190 cm21. The CvC bond of the 1,3-diyne
moiety exhibits a new band at 1460 cm21, which corre-
sponds to the molecular complex. Moreover, the C–H
bending vibration of the benzene and pyridine rings and the
double bond shows some differences in the frequencies, at
950 and 890 cm21 (830 and 820 cm21 in the free diyne) and
at 715 cm21 due to the Z-isomer, (750 cm21 in the free
diyne).
2.3. 1,4-Di[(4-pyridylethenyl)-4-phenyl]-buta-1,3-diyne,
(Z,Z)-5
The conjugate 1,3-butadiyne (Z,Z)-5 was purely obtained by
oxidative homocoupling of the conjugate acetylene (Z)-4,
catalysed by cuprous chloride in pyridine under oxygen
atmosphere,12 in moderate yield (43%), Scheme 1. (Z,Z)-5
was obtained as a white powder stable to the sunlight.
The 1H NMR spectrum of complex 8 in acetone-d6 shows a
strong deshielding effect on the pyridine protons pairs H-30,
H-50 and H-20, H-60, diminishing in this order, with respect
to the free 1,3-diyne. This effect was also observed with
strong intensity on the phenyl proton pairs H-2, H-6 and
H-3, H-5 and also on the conjugated vinyl protons of the
complex part of the molecule. Moreover, the uncomplexed
part also exhibits a deshielding effect on the phenyl and the
vinyl protons of the molecule but in very lowest intensity;
H-30, H-50 and H-20, H-60 on the pyridine ring are practically
not affected, Table 1. The net deshielding effect for the
phenyl protons were not well observed because the grouping
of the signals in the spectrum. Hence, the deshielding effect
diminishes with the distance to the complex site and is less
intense through the 1,3-triple bond conjugation. On the basis
of the deshielding effect, the TCNE–(Z,Z)-5 binding site
must be close to the C3–C5 phenyl bond and the TCNE
double bond parallel to the 1,3-diyne axis,14 Scheme 3.
In contrast, the E-4 isomer, under the same Glaser
conditions used for Z-4, or with different bases as
diethylamine, piperidine, pyridine or TMEDA, at variable
temperatures does not transform to the corresponding 1,3-
diyne (E,E)-5.
2.4. Charge–transfer complex between (Z,Z)-1,4-di[(4-
pyridylethenyl)-4-phenyl]-buta-1,3-diyne, (Z,Z)-5, and
tetracyanoethene, TCNE, 8
2.4.1. Donor molecules. The presence of the pyridine ring
in the structure invites to the preparation of charge–transfer
complex with donor molecules. However, the isolation of a
pure charge–transfer complex between (Z,Z)-1,4-di[(4-
pyridylethenyl)-4-phenyl]-buta-1,3-diyne, (Z,Z)-5, with
donor molecules such as N,N,N0,N0-tetramethyl-p-phenyl-
endiamine (TMPD) results unsuccessful.
2.4.2. Acceptor molecules. In contrast, a charge–transfer
complex between (Z,Z)-5 and tetracyanoethene (TCNE) as
acceptor was obtained by slow addition of a solution of the
acceptor in acetonitrile to a solution of the 1,3-diyne (Z,Z)-5,
in nearly boiling acetonitrile. The starting yellow solution
turned orange and by slow evaporation of the solvent only
the charge–transfer complex 8 was isolated as a green solid
as little spheres. On the basis of the elemental analysis and
spectral data, the acceptor/donor molar ratio (A/D) was 1:1.
The UV–visible spectrum of complex 8 shows a new
charge–transfer band at 419 nm (e, 655 l mol21 cm21).
Table 1. 1H NMR of (Z,Z)-5 and the charge–transfer complex 8
(Z,Z)-5
Complex ring
Uncomplex ring
H-20 and H-60 Py
H-30 and H-50 Py
H-2 and H-6 Ph
H-3 and H-5 Ph
Py–CHvCH
8.49
7.13
7.41
7.19
6.75
6.55
9.02
8.40
7.9–7.4
7.9–7.4
7.9–7.4
7.9–7.4
8.49
7.21
7.51
7.31
6.90
6.71
2.4.3. Structure of (Z,Z)-1,4-di[4-pyridylethenyl)-4-
phenyl]-buta-1,3-diyne–TCNE molecular complex. The
IR spectrum (KBr) of 8 shows a broad stretching vibration
Py–CHvCH

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J. G. Rodrıguez et al. / Tetrahedron 59 (2003) 1021–1032
1024
Scheme 3.
Table 2. 1H NMR of (Z,Z)-5 and the charge–transfer complex 9
protons of the conjugate 1,3-diyne part with respect to the
free diyne (Z,Z)-5, Table 2. The net deshielding effect on
each proton was not well observed because the grouping of
the signals of the phenyl ring. However, the double bond is
polarised towards the phenyl ring due to the electron
demand of the acceptor molecule on the phenyl ring,
Table 2.
(Z,Z)-5
Complex 9
H-20 and H-60 Py
H-30 and H-50 Py
H-2 and H-6 Ph
H-3 and H-5 Ph
Py–CHvCH
8.49
7.13
7.41
7.19
6.75
6.55
8.68
7.82–7.42
7.82–7.42
7.82–7.42
6.95
Py–CHvCH
6.87
On the basis of the deshielding effect, the TCNQ–(Z,Z)-5
binding site must be close to the C3–C5 phenyl bond and
TCNQ the double bonds orthogonal to the 1,3-diyne axis,
Scheme 4.
2.5. Complex between (Z,Z)-1,4-di[(4-pyridylethenyl)-4-
phenyl]-buta-1,3-diyne, (Z,Z)-5, and 7,70,8,80-tetra-
cyanoquinodimethane, TCNQ, 9
The UV–visible spectrum of the complex 9 shows a new
absorption band at 506 nm (1, 710 l mol21 cm21).
Some charge–transfer complexes between conjugated
systems and the acceptor TCNQ showing conductive
properties are ready known.15
2.6. Quaternation of the pyridine ring
2.6.1. Methyl quaternation of (E)-4. Preparation of (E)-
10 and dimerisation to (E,E)-11. The p-electronic effect of
the pyridine rings and the p-extended conjugation to the
1,3-diyne chain, in 1,4-di(n-pyridyl)-buta-1,3-diyne deriva-
tives, seems not sufficient to prepare charge–transfer
complexes with some donors. In contrast, we reported that
the mono- and di-methylated salts of the 1,4-di(m-pyridyl)-
buta-1,3-diyne gives a charge–transfer complex with the
donor molecule N,N,N0,N0-tetramethyl-p-phenylenediamine
(TMPD).15b
The charge–transfer complex between (Z,Z)-5, and 7,7,8,8-
tetracyano-p-quinodimethane (TCNQ) was prepared by
slow addition of a solution of the acceptor in acetonitrile
to a solution of the 1,3-butadiyne in nearly boiling
acetonitrile giving 9 as a green solid after complete
evaporation of the solvent. On the basis of the elemental
analysis and the spectral data, the A/D molar ratio of the
complex was 2:1.
The IR spectrum (KBr) of the complex 9 shows a broad
stretching vibration band of CuN and CuC bonds at
2150 cm21, while the free TCNQ shows a band at
2210 cm21 and the free diyne at 2190 cm21. The C–H
bending vibration due to the phenyl substitution appears at
810 cm21 (830 and 820 cm21 in the free diyne) and at
705 cm21 due to the Z-isomer (750 cm21 in the free diyne).
Moreover, a plus extended p-conjugated family compounds
containing the pyridine and phenyl rings are now prepared
and charge–transfer complexes with acceptor and donor
molecules investigated.
Compound E-10 was obtained by quaternation of E-4 with
iodomethane in ethanol at 70–758C in good yield. The salt
E-10 was transformed in the dimer (E,E)-11 in excellent
The 1H NMR spectrum in DMSO-d6 of the complex 9
shows a strong deshielding effect on the pyridine and phenyl
Scheme 4.

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J. G. Rodrıguez et al. / Tetrahedron 59 (2003) 1021–1032
1025
Scheme 5.
yield (98%), by oxidative homocoupling in presence of
cuprous chloride in pyridine, Scheme 5. However, the
preparation of (E,E)-5 under the same conditions results
unsuccessful. An argument about the different behaviour,
found in the oxidative coupling of (Z)-4 and (E)-4 isomers,
can be due to the deactivation of the copper(I) catalyst by
coordination with the N-electron pair of the pyridine ring,
more effective for the (E)-isomer. To prove this premise, the
coupling reaction of (E)-4 was carried out in presence of the
salt (E)-10, in 0.5 molar ratio giving the mixture (E,E)-5
(yellow solid, mp 113–1158C) and the disalt (E,E)-11
(brown solid, mp 158–1598C), in 15 and 98%, respectively;
the mono-salt was not detected. Hence, on the basis of the
stoichiometry of the reaction, a plausible interpretation of
this fact must be related to the enhanced transfer phase
produced by the salt E-10. Moreover, a Cu(I)/Cu(III) redox
pair mechanism for the oxidative dimerisation of the
acetylenes has been recently reported.16
2.6.3. Mono- and di-methylated salts of (Z,Z)-1,4-di[(4-
pyridylethenyl)-4-phenyl]-buta-1,3-diyne, (Z,Z)-5, (Z,Z)-
14 and (Z,Z)-15. The 1,3-butadiyne (Z,Z)-5 shows some
difficulty to form charge–transfer complexes with some
acceptors as TMPD. The quaternation of the nitrogen atom
of the pyridine rings was outlined to increase the acceptor
character of the compound, Scheme 6.15b
The methylated salts of the 1,3-diyne (Z,Z)-5, were obtained
by treatment with iodomethane in a mixture of ethanol/ethyl
acetate as solvent at reflux temperature. Two products were
isolated as solids in a 1:1 ratio (94% of yield); an orange
solid partially soluble in ethanol (Z,Z)-14 identified as the
mono- and an insoluble yellow solid (Z,Z)-15 as the di-
methylated salt.
By DSC, both (Z,Z)-14 and (Z,Z)-15 exhibit an irreversible
endothermic peak up to 1258C which corresponds with the
decomposition of the respective compound.
2.6.2. Methyl quaternation of (E)-6. Preparation of (E)-
12 and dimerisation to (E,E)-13. The saline compound
(E)-12 was isolated by quaternation of E-6 with iodo-
methane in ethanol at the reflux temperature, as a yellow
solid, in excellent yield (92%). The salt E-12 yields the
homocoupling biphenyl salt (EE)-13, in the presence of
zero-valent nickel complexes, prepared in situ, with
dichlorobis(triphenyl)phosphine nickel (II) in THF and
zinc powder, in good yield (68%), as a yellow solid,
Scheme 5. In contrast, the synthesis of the non-saline
biphenyl derivative starting of E-6, under the same method
was unsuccessful.
In the IR spectrum (KBr) the mono- (Z,Z)-14 and di-
methylated salt (Z,Z)-15 exhibit two characteristic bands of
the CH3–N bond at 1330, 1185 and 1320, 1180 cm21
,
respectively. The stretching frequencies CvC and CvN
and the bending C–H phenyl and pyridine show important
differences with the free diyne (Z,Z)-5 (see Section 3).
The 1H NMR spectrum of the mono-salt (Z,Z)-14 in
methanol-d4, shows a strong deshielding effect on the
protons of N-methylated pyridine, double bond and phenyl
ring in this order of intensity, by reference with diyne
Scheme 6.

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J. G. Rodrıguez et al. / Tetrahedron 59 (2003) 1021–1032
1026
Table 3. 1H NMR of (Z,Z)-5, and the saline compounds (Z,Z)-14 and
(Z,Z)-15
In the DSC diagram of 16 was observed a broad irreversible
endothermic peak up to 1258C, which coincides with the
decomposition of the compound (Z,Z)-15.
(Z,Z)-5
(Z,Z)-14
Saline moiety
(Z,Z)-14
Non-saline
moiety
(Z,Z)-15
In the UV–visible spectrum of complex 16, were observed
two bands at 533 (1, 660) and 639 nm (1, 905 l mol21
cm21), probably due to the two different electronic transfer
H-20 and H-60 Py
H-30 and H-50 Py
H-2 and H-6 Ph
H-3 and H-5 Ph
Py–CHvCH
8.49
7.13
7.41
7.19
6.75
6.55
8.91
7.99
7.54
7.39
7.40
6.97
8.46
7.19
7.49
7.30
6.89
6.78
8.78
7.83
7.57
7.34
7.23
6.89
1
absorption band, which from the H NMR spectrum, show
a symmetric overlapping of the donor molecule on the
pyridinium salt.
Py–CHvCH
Scheme 7.
(Z,Z)-5. In contrast, in the non-saline moiety the deshielding
effect through the diyne conjugation is significant in the
phenyl and double bond protons but pyridine protons are
practically unperturbed. The N-methyl salt protons appear
as a singlet at 4.50 ppm.
2.8. Charge–transfer complex between the di-salt (Z,Z)-
15 and TCNQ, 17
The charge–transfer complex between the di-salt (Z,Z)-15
and TCNQ was obtained by slow addition of a solution of
TCNQ in hot acetonitrile to a solution of the salt (Z,Z)-15 in
hot acetonitrile and after complete evaporation of solvent,
the complex 17, was isolated as a black-green solid with
metallic shine.
The 1H NMR spectrum of the di-N-methylated salt (Z,Z)-15
in DMSO-d6, shows a strong deshielding effect on all the
protons of the conjugate system but in slightly lowest
intensity than the saline moiety of the mono-methylated salt,
Table 3. The N-methyl protons appear at 4.28 ppm.
The IR spectrum (KBr) of the complex 17 shows a broad
CvN and CvC stretching vibration band at 1610, 1590,
2.7. Charge–transfer complex between (Z,Z)-15 and
N,N,N0,N0-tetramethyl-p-phenylenediamine (TMPD), 16
Table 4. 1H NMR of (Z,Z)-15, and charge–transfer complex 16
(Z,Z)-15 16, Complexed ring 16, Uncomplexed ring
The charge–transfer complex 16 was prepared by addition
of TMPD acetone solution into a (Z,Z)-15 acetone/water
solution by slow evaporation. Complex 16 was isolated as a
blue–black solid with metallic shine. On the basis of the
elemental analysis and spectral data, the A/D molar ratio
was 1:1.
H-20 and H-60 Py 8.78
H-30 and H-50 Py 7.83
H-2 and H-6 Ph 7.57
H-3 and H-5 Ph 7.34
8.25
8.90
8.05
7.9–7.4
7.9–7.4
7.36
7.9–7.4
7.9–7.4
7.9–7.4
6.90
Py–CHvCH
Py–CHvCH
7.23
6.89
6.72
7.22
The IR spectrum (KBr) of the complex 16 shows a broad
CvN and CvC stretching band at 1610, 1590, 1540, 1510
and 1460 cm21. The Nþ–CH3 bond shows two absorption
bands at 1185 and 1170 cm21 (Scheme 7).
Table 5. 1H NMR of (Z,Z)-15, and charge–transfer complex 17
(Z,Z)-15
Complex 17
The 1H NMR spectrum of complex 16 in DMSO-d6 exhibits
a strong shielding effect on the pyridinium ring, and double
bond protons of the 1,3-diyne derivative. The phenyl
protons appear within a multiplet at 7.4–7.9 ppm but the
net effect of each proton was not well observed, Table 4. In
contrast, the uncomplexed ring moiety shows a deshielding
effect with respect to the free dimethylated salt (Z,Z)-15.
H-20 and H-60 Py
H-30 and H-50 Py
H-2 and H-6 Ph
H-3 and H-5 Ph
Py–CHvCH
8.78
7.83
7.57
7.34
7.23
6.89
8.90
8.25
7.9–7.5
7.9–7.5
7.39
Py–CHvCH
7.08

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J. G. Rodrıguez et al. / Tetrahedron 59 (2003) 1021–1032
1027
Scheme 8.
1540, 1510 and 1460 cm21. The Nþ–CH3 bond show two
toluene. The filtered solution was warmed at the reflux
temperature for 24 h, giving a new precipitate of the
phosphonium salt. The precipitate fractions were finally
dried at reduced pressure giving the phosphonium salt as a
white solid, 77.4 g. (75%), mp 238–2408C (lit.9 241–
2428C).
absorption bands at 1185 and 1170 cm21
.
1
The H NMR spectrum of 17 in DMSO-d6 shows a strong
general deshielding effect on the protons with respect to the
free di-salt (Z,Z)-15, Table 5.
On the basis of the elemental analysis and the spectral data,
was determined a stoichiometric ratio of 2:1 of the
components, Scheme 8.
Wittig reaction between bromomethyl(triphenyl)phos-
phonium ylide and 4-methylbenzaldehyde. To a solution of
bromomethyl(triphenyl)phosphonium bromide (18.69 g,
42.88 mmol) in dry THF (100 ml), under argon atmosphere
at 08C, was added potassium tert-butoxide (5.23 g,
42.88 mmol). The yellow solution was stirred for 30 min
and then was slowly added 4-methylbenzaldehyde (5.15 g,
42.88 mmol) and stirred at room temperature for 6 h. After,
solvent was removed and the residual oil was washed with
water (30 ml) and extracted with dichloromethane, dried on
magnesium sulfate, filtered and solvent removed giving an
oil which was purified by silica gel column chromatography
(hexane/dichloromethane, 4:1). The p-(2-bromoethenyl)-
toluene (1) was obtained, (4.32 g, 52%), as a yellow oil as an
E/Z isomer mixture (1:1, by NMR).
The DSC diagram of 17 shows an irreversible broad
exothermic peak (160–2258C) corresponding to the
decomposition of the complex, but no melting peaks of
the components were detected.
In the UV–visible spectrum of the complex 17, was
)
observed a weak band at 644 nm (1, 780 l mol21 cm21
due to the electronic transfer absorption band.
3. Experimental
(E)-p-(2-Bromoethenyl)toluene, (E)-1. IR (film): 2920 and
2860 (C–H); 1620 and 1520 (CvC, conj.); 950
(CHvCHBr, E); 820 and 805 (p-disubst.). 1H NMR
(CDCl3): 7.7–7.1 (m, 4H, Ar); 7.05 (d, 1H, J¼14.0 Hz,
CHvCHBr, E); 6.65 (d, 1H, J¼14.0 Hz, CHvCHBr, E);
2.33 (s, 3H, CH3). Calcd for C9H9Cl: C, 70.83; H, 5.94; N,
23.23. Found: C, 70.66; H, 6.24; N, 23.07%.
Melting points were determined in open capillary tubes or in
a Reichert hot stage microscope and are uncorrected.
Infrared spectra were recorded using a Bruker Vector 22
spectrophotometer. NMR spectra were recorded at 200 or
300 MHz using a Bruker Aspect spectrometer. Chemical
shifts are given in ppm, using TMS as internal reference.
UV–visible spectra were recorded using a Hewlett–
Packard 8453 spectrophotometer. Mass spectra were
recorded using electronic impact technique at 70 eV, in a
VG AutoSpec spectrometer. The DSC analyses were carried
out in a Perkin–Elmer calorimeter. Elemental analyses were
performed with a LECO CHN-600. All solvents and
chemicals were reagent grade.
(Z)-p-(2-Bromoethenyl)toluene, (Z)-1. IR (film): 2920 and
2860 (C–H); 1620 and 1520 (CvC, conj.); 820 and 805
1
(p-disubst.); 720 (CHvCHBr, Z). H NMR (CDCl3): 7.7–
7.1 (m, 4H, Ar); 7.00 (d, 1H, J¼8.2 Hz, CHvCHBr, Z);
6.32 (d, 1H, J¼8.2 Hz, CHvCHBr, Z); 2.35 (s, 3H, CH3).
Calcd for C9H9Cl: C, 70.83; H, 5.94; N, 23.23. Found: C,
70.52; H, 5.75; N, 23.12%.
3.1. (E)- and (Z)-(40-pyridylethenyl)-4-phenylethyne (4),
by dehydrohalogenation of the halovinylarene
derivatives
3.1.2. p-(2-Bromoethenyl)benzyl(triphenyl)phos-
phonium bromide, 2. p-(2-Bromoethenyl)bromomethyl-
benzene. To a solution of (E/Z)-p-(2-bromoethenyl)toluene
(1) (4.2 g, 21.33 mmol) in tetrachloromethane (10 ml), was
added N-bromosuccinimide (3.39 g, 19.04 mmol) and
benzoyl peroxide (100 mg). The mixture was warmed at
the reflux temperature for 16 h and after cooling, was
filtered and solvent removed, giving a residual oil that was
3.1.1. p-(2-Bromoethenyl)toluene, 1. A solution of tri-
phenylphosphine (60 g, 228 mmol) and dibromomethane
(89.2 g, 460 mmol) in dry toluene (500 ml) was warmed at
the reflux temperature for 24 h. The mixture was cooled at
08C and the precipitated of bromomethyl(triphenyl)-
phosphonium bromide was filtered and washed with

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1028
purified by pressurised silica gel column chromatography
(hexane/toluene, 16:1). The (E)-p-(2-bromoethenyl)bromo-
methylbenzene was isolated, as a yellow oil, 2.95 g (56%);
the starting product was recovered as the E isomer (1) and
3.1.4. 0(E) and (Z)-(40-Pyridylethenyl)-4-phenylethyne, 4.
(Z)-(4 -Pyridylethenyl)-4-phenylethyne (Z-4). To a solution
of
(E,Z)-(40-pyridylethenyl)-4-phenyl-b-bromoethene,
(E,Z)-3, (0.38 g, 1.34 mmol) in dry THF (10 ml), at 08C
was added potassium tert-butoxide (0.16 g, 1.34 mmol).
The mixture was stirred under sunlight exposure at room
temperature for 24 h and then was hydrolysed with a
saturated solution of ammonium chloride and extracted with
dichloromethane. The organic layer was dried on mag-
nesium sulfate, filtered and solvent removed to give a
residual brown oil, which was purified by silica gel
column chromatography (THF/hexane, 2:1). (Z)-(40-
pyridylethenyl)-4-phenylethyne (Z-4), was obtained as a
yellow oil, 180 mg (66%). IR (film): 3290 (uCH); 2260
(CuC); 1590 (Py); 1540 (CvC, conj.); 990 (Py); 830
(p-disubst.); 720 (CHvCH, Z). 1H NMR (CDCl3): 8.46 (d,
2H, J¼5.2 Hz, H-2 and H-6, Py); 7.31 (d, 2H, J¼8.2 Hz,
H-2 and H-6, Ph); 7.12 (d, 2H, J¼8.2 Hz, H-3 and H-5, Ph);
7.09 (d, 2H, J¼5.2 Hz, H-3 and H-5, Py); 6.72 (d, 1H,
J¼12.2 Hz, Py–CHvCH, Z); 6.51 (d, 1H, J¼12.2 Hz,
Py–CHvCH, Z); 3.12 (s, 1H, uCH). 13C NMR (CDCl3):
149.5 (C-2 and C-6, Py); 144.7 (C-4, Py); 136.3 (C-1, Ph);
133.0 and 131.9 (C-2 and C-6, Ph); 128.6 and 128.2 (C-3
and C-5, Ph); 125.4 (2C, CHvCH); 123.4 (C-3 and C-5,
Py); 120.8 (C-1, Ph); 80.0 (Ph–CuCH); 77.1 (Ph–
CuCH). MS (70 eV): 205 (Mþ, 95); 204 (100); 176 (31);
151 (13); 126 (11); 102 (12); 76 (17). Calcd for C15H11N: C,
87.78; H, 5.40; N, 6.82. Found: C, 87.49; H, 5.38; N, 6.52%.
1
reused, 1.68 g (40%). H NMR (CDCl3): 7.7–7.1 (m, 4H,
Ar); 7.07 (d, 1H, J¼13.8 Hz, CHvCHBr, E); 6.77 (d, 1H,
J¼13.8 Hz, CHvCHBr, E); 4.45 (s, 2H, CH2).
p-(2-Bromoethenyl)benzyl(triphenyl)phosphonium bromide,
2. A solution of triphenylphosphine (2.8 g, 10.68 mmol) and
p-(2-bromoethenyl)bromomethylbenzene (2.95 g, 10.68
mmol) in dry toluene (60 ml), was warmed at the reflux
temperature for 12 h. After, the mixture was cooled and the
precipitated phosphonium salt 2, was filtered and dried at
vacuum, giving a white solid, 5.27 g (92%), mp 213–2168C.
3.1.3. (E,E)-(40-Pyridylethenyl)-4-phenyl-b-bromo-
ethene, 3. To a suspension of the phosphonium salt 2
(X¼Cl, Br) (9.8 mmol) in dry toluene (10 ml), at 08C was
added potassium tert-butoxide (1.19 g, 9.8 mmol) and
stirred for 30 min. Then, pyridine-4-carboxaldehyde
(1.05 g, 9.8 mmol), was added and stirred at room
temperature for 4 h. Finally, solvent was removed at
reduced pressure and the residual oil was washed with
water (10 ml) and extracted with dichloromethane. After,
solvent was removed and the residual oil was purified by
silica gel column chromatography (hexane/THF, 1:1).
Compound 3 was isolated as a mixture of isomers, (E,E)-
(40-pyridylethenyl)-4-phenyl-b-bromoethene, 0.82 g (30%),
yellow solid, mp 117–1208C and (E,Z)-(40-pyridylethenyl)-
4-phenyl-b-bromoethene, 0.92 g (33%), as a yellow oil.
(E)-(40-Pyridylethenyl)-4-phenylethyne (E-4). To a solution
of (E,E)-(40-pyridylethenyl)-4-phenyl-b-chloroethene
(0.2 g, 0.699 mmol) in dry THF, at 08C was added
potassium tert-butoxide (85 mg, 0.699 mmol). The mixture
was stirred under sunlight exposure at room temperature for
24 h and then, hydrolysed with a saturated solution of
ammonium chloride and extracted with dichloromethane.
The organic layer was dried on magnesium sulfate, filtered
and solvent removed to give a residual brown oil, which was
purified by silica gel column chromatography (THF/hexane,
2:1). The (E)-(40-pyridylethenyl)-4-phenylethyne (E-4), was
isolated, 108 mg (75%), as a yellow solid, mp 187–1908C.
IR (KBr): 1630 (CvN); 1590, 1530 and 1490 (CvC); 995
(Py), 950 (E-isomer); 830 (p-subst. ArH). 1H NMR
(CDCl3): 8.58 (d, 2H, J¼6.8 Hz, H-3 and H-5 Py); 7.50
(s, 4H, Ph); 7.35 (d, 2H, J¼6.8 Hz, H-2 and H-6 Py); 7.25
(d, 1H, J¼16.3 Hz, PhCHv); 7.02 (d, 1H, J¼16.3 Hz,
PyCHv); 3.20 (s, 1H, CuCH). 13C NMR (CDCl3): 149.8
(C3, C5, Py); 144.0 (C1, Py); 136.2 (C1, Ph); 132.3 (C3, C5,
Ph); 131.9 and 126.8 (CHvCH); 126.7 (C2, C6, Ph); 122.0
(C4, Ph); 120.7 (C2, C6, Py); 83.2 (–Cu); 78.5 (uCH).
MS (70 eV): 205 (Mþ, 98); 204 (100); 180 (7); 176 (27);
151 (16); 126 (9); 102 (21); 76 (16). UV–visible (CH2Cl2):
233 (1, 5833); 299 (1, 7035); 456 (1, 11). Calcd for
C15H11N: C, 87.78; H, 5.40; N, 6.82. Found: C, 87.58; H,
5.23; N, 6.66%.
(E,E)-(40-Pyridylethenyl)-4-phenyl-b-bromoethene, (E,E)-
3. IR (KBr): 1590 (Py); 1550 (CvC, conj.); 990 (Py); 970
1
(CHvCHBr, E); 955 (CHvCH, E); 830 (p-disubst.). H
NMR (CDCl3): 8.59 (d, 2H, H-2 and H-6, Py); 7.8–6.8 (m,
6H, Ar); within of the multiplet was identified at 7.28 (d,
1H, J¼16.1 Hz, Py–CHvCH, E); 7.03 (d, 1H, J¼16.1 Hz,
Py–CHvCH, E); 7.04 (d, 1H, J¼14.0 Hz, CHvCHBr, E);
6.83 (d, 1H, J¼14.0 Hz, CHvCHBr, E). 13C NMR
(CDCl3): 150.0 (C-2 and C-6, Py); 144.4 (C-4, Py); 136.6
(CHvCHBr); 136.1 (C-4, Ph); 132.1 (C-1, Ph); 128.7 (C-2
and C-6, Ph); 127.3 (CHvCH); 126.8 (C-3 and C-5, Ph);
126.4 (CHvCH); 120.7 (C-3 and C-5, Py); 107.1
(CHvCHBr). MS (70 eV): 287 (Mþþ2, 61); 285 (Mþ, 66);
204 (100); 176 (36); 151 (26); 126 (15); 102 (61); 76 (43).
(E,Z)-(40-Pyridylethenyl)-4-phenyl-b-bromoethene, (E,Z)-
3. IR (film): 3020 (vC–H); 1590 (Py); 1565 (CvC,
conj.); 970 (CHvCHBr, E); 840 (p-disubst.); 710
1
(CHvCH, Z). H NMR (CDCl3): 8.46 (d, 2H, J¼5.7 Hz,
H-2 and H-6, Py); 7.43 (d, 2H, J¼8.4 Hz, H-2 and H-6, Ph);
7.19 (d, 2H, J¼8.4 Hz, H-3 and H-5, Ph); 7.09 (d, 2H,
J¼5.7 Hz, H-3 and H-5, Py); 7.03 (d, 1H, J¼14.0 Hz,
CHvCHBr, E); 6.75 (d, 1H, J¼14.0 Hz, CHvCHBr, E);
6.71 (d, 1H, J¼12.3 Hz, Py–CHvCH, Z); 6.52 (d, 1H,
J¼12.3 Hz, Py–CHvCH, Z). 13C NMR (CDCl3): 149.7
(2C, C-2 and C-6, Py); 144.7 (C-4, Py); 136.3 (CHvCHBr);
136.1 (C-4, Ph); 131.8 (C-1, Ph); 129.1 (CHvCH); 128.7
(C-2 and C-6, Ph); 128.3 (C-3 and C-5, Ph); 127.7
(CHvCH); 123.2 (C-3 and C-5, Py); 107.0 (CHvCHBr).
MS (70 eV): 287 (Mþþ2, 57); 285 (Mþ, 59); 204 (100); 176
(42); 151 (29); 126 (12); 102 (65); 76 (38).
3.2. From the appropriate haloarene with 2-methyl-but-
3-yn-2-ol catalysed by palladium
3.2.1. (E and Z)-1-(p-iodophenyl)-2-(4-pyridyl)ethene, 6.
4-(Bromomethyl) iodobenzene. To a solution of 4-iodo-
toluene (5.0 g, 22.9 mmol) in tetrachloromethane (10 ml),
was added N-bromosuccinimide (3.73 g, 20.0 mmol) and

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benzoyl peroxide (30 mg) and the mixture was warmed at
the reflux temperature for 16 h. After cooling, the mixture
was filtered and the solvent removed providing a residual
oil, which was purified by pressurised silica gel column
chromatography (hexane/dichloromethane, 5:1). The
p-(bromomethyl)iodobenzene was isolated, as a white–
sulfate, filtered and solvent removed giving a brown solid
that was purified by silica gel column chromatography
(hexane/THF, 4:1). The (E)-4-[40-(pyridylethenyl)-4-
phenyl]-4-(2-methyl-but-3-yn-2-ol (7), (E-7), was obtained,
1
110 mg (71%), as a white solid, mp 165–1678C. H NMR
(CDCl3): 8.50 (d, 2H, J¼6.8 Hz, H3 Py); 7.657.45 (m, 6H,
ArH and H2 Py); 7.52 (d, J¼16.3 Hz, CHv); 7.21 (d,
J¼16.3 Hz, CHv); 1.60 (s, 6H, CH3); 1.20 (broad s, 1H,
OH). MS (70 eV): 263 (Mþ, 69); 262 (41); 248 (100); 205
(18); 204 (29); 180 (10).
1
rose solid, 4.76 g (70%), mp 63–658C. H NMR (CDCl3):
7.68 (d, 2H, J¼8.7 Hz, H-2 and H-6); 7.10 (d, 2H,
J¼8.7 Hz, H-3 and H-5); 4.45 (s, 2H, CH2).
4-Iodobenzyl(triphenyl)phosphonium bromide. A solution
of triphenylphosphine (3 g, 11.5 mmol) and 4-(bromo-
methyl)iodobenzene, (2.25 g, 11.5 mmol) in dry toluene
(40 ml), was warmed at reflux temperature for 12 h. After
cooling, the precipitate of phosphonium salt was filtered and
dried at reduced pressure. The 4-iodobenzyltriphenyl-
phosphonium bromide was obtained as a white solid,
3.33 g (78%), mp 255–2568C.
3.2.3. (E)-(40-Pyridylethenyl)-4-phenyl)ethyne, (E)-4. A
solution of the propargylic derivative (E)-7 (110 mg,
0.42 mmol) in dry toluene (5 ml) was heated under reflux
temperature with a little amount of pulverised sodium
hydroxide for 2 h. Then, the solution was decanted and the
solvent was evaporated under reduced pressure giving a
brown residual solid that was purified by silica gel column
chromatography (hexane/THF, 4:1). The ((E)-(40-pyridyl-
ethenyl)-4-phenyl)ethyne, E-4), was obtained as a yellow
solid, 60 mg (70%), mp 187–1898C. Spectral data are given
above.
Wittig reaction between 4-iodobenzyl(triphenyl)phosphonium
ylide and pyridine-4-carboxaldehyde, 6. To a solution of
4-iodobenzyltriphenylphosphonium bromide (2.52 g,
4.8 mmol) in dry toluene (10 ml), under argon atmosphere
at 08C, was added potassium tert-butoxide (0.54 g,
4.8 mmol). The orange solution was stirred for 30 min and
then 4-pyridinecarboxaldehyde (0.46 ml, 4.8 mmol) was
slowly added. The mixture was stirred at room temperature
for 12 h and after, solvent was removed and the residual oil
was washed with water (10 ml) and extracted with
dichloromethane, dried on magnesium sulfate. After, the
mixture was filtered and solvent removed giving a solid,
which was purified by pressurized silica gel column
chromatography (hexane/THF, 2:3). The 1-(p-iodo-
phenyl)-2-(4-pyridyl)ethene, (6) was obtained as a yellow
solid, 1.1 g (79%), as a mixture of the E/Z isomers (10:1), by
NMR. A solution of the mixture of isomers in ethanol was
completely transformed to (E)-1-(p-iodophenyl)-2-(4-
pyridyl)ethene, by sunlight exposure for 48 h. Compound
(E)-6 was purely isolated as a yellow solid, mp 194–1978C,
1.1 g (80%). IR (KBr): 3040 (ArC–H); 1625 (CvN); 1590
and 1475 (CvC, conj.); 1065 (C-I); 990 (CHvCH, E); 815
(p-disubst.); 745 (CHvCH, Z). 1H NMR (CDCl3): 8.58 (d,
2H, J¼6.8 Hz, H-3 and H-5 Py); 7.71 (d, 2H, J¼8.4 Hz, H3
and H-5 Ph); 7.35 (d, 2H, J¼6.8 Hz, H-2 and H-6 and H-6
Py); 7.30 (d, 2H, J¼8.4 Hz, H-2 and H-6 and H-6 Ph); 7.22
(d, 1H, J¼16.3 Hz, PhCHv); 7.00 (d, 1H, J¼16.3 Hz,
PyCHv). 13C NMR (CDCl3): 150.2 (C3, C5, Py); 144.1
(C1, Py); 137.9 (C3, C5, Ph); 135.6 (C1, Ph); 132.1 and
131.9 (CHvCH); 126.7 (C2, C6, Ph); 120.7 (C2, C6, Py);
94.3 (C–I). Calcd for C13H10NI: C, 50.84; H, 3.28; N, 4.56.
Found: C, 51.18; H, 3.43; N, 4.65%.
3.2.4. (Z,Z)-1,4-Di[(4-pyridylethenyl)-4-phenyl]-buta-
1,3-diyne, (Z,Z)-5. To a dispersion of Cu2Cl2 (116 mg,
1.17 mmol) in dry pyridine (4 ml), under oxygen atmos-
phere, was added a solution of (Z)-4 (240 mg, 1.17 mmol) in
pyridine (6 ml). The mixture was stirred overnight and after
pyridine was removed. The residual solid was purified by
silica gel column chromatography (THF/hexane, 3:2) giving
the 1,3-diyne (Z,Z)-5 as a yellow solid, which was
crystallised from ethanol to provide a white solid, 102 mg
(43%), mp 200–2028C. IR (KBr): 2190 (CuC); 1590, 1540
and 1495 (CvC, conj.); 990 (subst. Py); 830 and 820
(p-disubst.); 750 (CHvCH, Z). 1H NMR (CDCl3): 8.49 (d,
4H, J¼5.9 Hz, H-2 and H-6 Py); 7.41 (d, 4H, J¼8.2 Hz, H-2
and H-6 Ph); 7.19 (d, 4H, J¼8.2 Hz, H-3 and H-5 Ph); 7.13
(d, 4H, J¼5.9 Hz, H-3 and H-5 Py); 6.75 (d, 2H, J¼12.7 Hz,
Py–CHvCH, Z); 6.55 (d, 2H, J¼12.7 Hz, Py–CHvCH,
Z). 13C NMR (CDCl3): 149.7 (4C, C-2 and C-6 Py); 144.5
(2C, C-4 Py); 137.0 (2C, C-4 Ph); 132.8 (4C, C-2 and C-6
Ph); 132.5 (4C, C-3 and C-5 Ph); 128.8 (CvC); 126.9 (2C,
C-1 Ph); 121.0 (4C, C-3 and C-5 Py); 81.7 (Ph–CuC); 74.7
(CuC–Ph). MS (70 eV): 408 (Mþ, 100), 204 (9). UV–
visible (CH2Cl2): 235 (1, 5800); 342 (1, 7300 l mol21
cm21). Calcd for C30H20N2: C, 88.21; H, 4.94; N, 6.86.
Found: C, 88.27; H, 4.77; N, 6.55%.
3.2.5. Charge–transfer complex of (Z,Z)-1,4-di[(4-pyr-
idylethenyl)-4-phenyl]-buta-1,3-diyne, (Z,Z)-5 with
TCNE, 8. A hot solution of tetracyanoethene (TCNE)
(25 mg (0.19 mmol) in acetonitrile (20 ml) was added to a
nearly boiling solution of Z,Z-5 (80 mg (0.19 mmol) in
acetonitrile (60 ml). The resulting orange solution was
allowed to cool and then to evaporate slowly to provide a
brown–green solid (8), which was continuously extracted
with hexane for 48 h in a soxhlet, giving a green solid as
little spheres, with a 1:1 stoichiometry between the
components. IR (KBr): 2200 (br, CuN and CuC); 1590,
1540, 1500 and 1460 (CvC, conj.); 1335 (C–N); 990, 950
and 890 (susbt. Py); 835 and 820 (p-disubst.); 750 and 715
(CHvCH, Z). 1H NMR (acetone-d6): 9.02 (d, 2H,
J¼5.7 Hz, H-2 and H-6, Py, complex); 8.49 (d, 2H,
3.2.2. (E)-4-[40-(Pyridylethenyl)-4-phenyl]-4-(2-methyl-
but-3-yn-2-ol (7), (E)-7. To a solution of 2-(4-iodo-
phenyl)-1-(4-pyridyl)ethene (180 mg, 0.58 mmol) and
2-methyl-but-3-yn-2-ol (58 mg, 0.69 mmol) in freshly
distilled diethylamine (7 ml), under argon atmosphere was
added dichlorobis(triphenyl)phosphine palladium (4.1 mg)
and a little amount of cuprous iodide. The mixture was
stirred at room temperature for 15 h. After, diethylamine
was removed at reduced pressure and the residual solid was
washed with water (10 ml) and extracted with dichloro-
methane. The organic layer was dried on magnesium

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1030
J¼5.7 Hz, H-2 and H-6, Py); 8.40 (d, 2H, J¼5.7 Hz, H-3
and H-5, Py, complex); 7.9–7.4 (m, 4H, Ph and 2H,
CHvCH, complex ring); 7.51 (d, 2H, J¼8.7 Hz, H-2 and
H-6, Ph); 7.31 (d, 2H, J¼8.7 Hz, H-3 and H-5, Ph); 7.21 (d,
2H, J¼5.7 Hz, H-3 and H-5, Py); 6.90 (d, 1H, J¼11.6 Hz,
Py–CHvCH, Z); 6.71 (d, 1H, J¼11.6 Hz, Py–CHvCH,
Z). UV–visible (CH2Cl2): 234 (5750); 347 (7240); 419
(655 l mol21 cm21). DSC: .2108C, dec. Calcd for
C36H20N6: C, 80.58; H, 3.76; N, 15.66. Found: C, 80.88;
H, 3.43; N, 15.45%.
removed, to give a residual solid that was washed with
ammonium hydroxide and extracted with dichloromethane.
The organic layer was dried on anhydrous magnesium
sulphate and after filtration and solvent evaporation a brown
solid was obtained that was purified by crystallisation in
warmed n-hexane to give 1,4-di[(E)-4-(p-ethenylphenyl-
ethynyl)pyridinium iodide], (E,E)-11, 63 mg (98%) as a
brown solid, mp .3008C. IR (KBr): 3418 (uC–H); 1617
(CvN); 1593 and 1517 (CvC); 1181 (þN–CH3); 986
(E-isomer); 834 (p-subst. ArH). 1H NMR ((CD3)2SO): 8.87
(d, 4H, J¼6.8 Hz, H-3 Py); 8.24 (d, 4H, J¼6.8 Hz, H-2 Py);
8.03 (d, 2H, J¼16.6 Hz, PhCHv); 7.82 (d, 4H, J¼8.7 Hz,
H-2 Ph); 7.56 (d, 2H, J¼16.6 Hz, PyCHv); 7.54 (d, 4H,
J¼8.7 Hz, H-3 Ph); 4.26 (s, 6H, þN–CH3). Calcd for
C32H26N2I2: C, 55.51; H, 3.79; N, 4.05. Found: C, 55.66; H,
3.48; N, 3.78%.
3.2.6. Charge–transfer complex between (Z,Z)-1,4-di[(4-
pyridylethenyl)-4-phenyl]-buta-1,3-diyne, (Z,Z)-5 and
TCNQ, 9. A hot solution of 7,7,8,8-tetracyano-p-quino-
dimethane (TCNQ) (100 mg, 0.48 mmol) in hot acetonitrile
(25 ml) was added to a nearly boiling solution of 1,4-di((Z)-
1-(4-phenyl)-2-(4-pyridyl)ethenyl(-1,3-butadiyne (Z,Z-5)
(100 mg, 0.24 mmol) in acetonitrile (50 ml). The mixture
was stirred at reflux temperature for 3 h. The resulting
brown solution was allowed to cool and then to evaporate
slowly to provide 9, which was continuously extracted with
hexane for 60 h in a soxhlet, giving as a green solid, with 2:1
stoichiometry ratio between the components. IR (nujol):
2150 (CuN); 1580 and 1550 (CvC, conj.); 950 (Py); 810
(p-disubst.); 705 (CHvCH, Z). 1H NMR (DMSO): 8.68 (m,
4H, H-2 and H-6 Py); 8.10 (m, 4H, TCNQ); 7.82–7.42 (m,
12H, H-3 and H-5 Py, H-2, H-3, H-5 and H-6 Ph); 6.92 (m,
4H, CHvCH). UV–visible (CH2Cl2): 233 (5860); 361
(6700); 396 (7200); 506 nm (710 l mol21 cm21). Calcd for
C54H28N10: C, 79.40; H, 3.45; N, 17.15. Found: C, 79.63; H,
3.67; N, 16.82%.
(E,E)-1,4-Di[(4-pyridylethenyl)-4-phenyl]-buta-1,3-diyne,
(E,E)-5. To a dispersion of Cu2Cl2 (66 mg, 0.67 mmol) in
dry and freshly distilled pyridine (5 ml), at 408C under
oxygen atmosphere, a solution of the acetylene derivatives
(E)-4 (88 mg, 0.43 mmol) and (E)-10 (336 mg, 0.97 mmol)
in dry pyridine (10 ml) was added. The mixture was stirred
for 12 h and after, pyridine was removed and the residual
solid was dissolved in dichloromethane and filtered. After
solvent elimination a brown solid was obtained which was
crystallised in hot ethanol, giving the saline 1,3-diyne (E,E)-
11 (328 mg, 98%), as a brown solid, mp 158–1598C. The
filtered dichloromethane solution was washed with
ammonium hydroxide and extracted with dichloromethane.
The organic layer was dried with MgSO4 and after filtration
and solvent elimination a residual solid was obtained and
purified by silica gel column chromatography (dichloro-
methane). The 1,3-diyne (E,E)-5 was isolated as a yellow
solid, 13 mg (15%). IR (KBr): 1595 and 1485 (CvC, conj.),
3.3. Quaternation of the pyridine ring
3.3.1. Methyl quaternation of (E)-4. Preparation of (E)-
10 and dimerisation to (E,E)-11. (E)-10. In a previously
flamed three-necked flask were placed under argon
atmosphere a solution of (E)-4 (150 mg, 0.73 mmol) and
of iodomethane (0.45 ml, 0.73 mmol) in ethanol (25 ml).
The solution that takes initially a dark-orange colour, was
stirred overnight at 70–758C. Finally, the solvent was
evaporated and chloroform (25 ml) was added and the
solution filtered to give (E)-10, 227 mg (89%) as a brown
solid, mp 197–1988C (darkness at 1958C). IR (KBr): 3424
(uC–H); 1620 (CvN); 1598 and 1517 (CvC); 1334
(N–CH3); 1185 (þN–CH3); 981 (E-isomer); 840 (p-subst.
1
995 (subst. Py); 973 (CvCH, E), and 828 (p-disubst.). H
NMR (CDCl3): 8.60 (d, 4H, J¼6.3 Hz, H-2 and H-6 Py),
7.66 (d, 4H, J¼7.8 Hz, H-3 and H-6, Ph), 7.47 (d, 4H,
J¼7.8 Hz, H-2 and H-6, Ph), 7.28 (d, 2H, J¼15.8 Hz,
PhCHvCH, E), 7.05 (d, 2H, J¼15.8 Hz, Py–CHvCH, E).
13C NMR (CDCl3): 149.5 (4C, C-2 and C-6 Py), 144.8 (2C,
C-4 Py), 136.8 (2C, C-1, Ph), 132.8 (4C, C-2 and C-6 Ph),
132.6 (2C, PhCHvCH, E), 127.1 (2C, PyCHvCH, E),
127.0 (4C, C-2 and C-6, Ph), 121.9 (2C, C-4, Ph), 121.1 (4C,
C-3 and C-5, Py), 82.1 (2C, Ph–CuC), 75.3 (2C, PhCuC).
MS (70 eV): 408 (Mþ, 100), 204 (9). UV–visible (CH2Cl2)
lmax (nm): 230 (15630); 361 (22705 l mol21 cm21). Calcd
for C30H20N2: C, 88.21; H, 4.94; N, 6.86. Found: C, 87.87;
H, 4.64; N, 6.75%.
1
ArH). H NMR (MeOD): 8.76 (d, 2H, J¼6.8 Hz, H-3 Py);
8.20 (d, 2H, J¼6.8 Hz, H-2 Py); 7.95 (d, 1H, J¼16.3 Hz,
PhCHv); 7.77 (d, 2H, J¼8.4 Hz, H-2 Ph); 7.57 (d, 2H,
J¼8.4 Hz, H-3 Ph); 7.49 (d, 1H, J¼16.3 Hz, PyCHv); 4.35
(s, 3H, þN–CH3); 3.71 (s, 1H, –CuCH). UV–visible
(EtOH), lmax (nm): 206 (31000); 250 (16180); 295 (10175);
360 (13565). Calcd for C16H14NI: C, 55.35; H, 4.06; N,
4.03. Found: C, 55.11; H, 4.25; N, 3.73%.
3.3.2. Methyl quaternation of (E)-6. Preparation of (E)-
12 and dimerisation to (E,E)-13. 4-[p-(2-Ethenyl)-iodo-
phenyl]pyridinium iodide (E)-12. In a three-necked flask
were placed E-6 (200 mg, 0.65 mmol) and iodomethane
(0.40 ml, 0.65 mmol) in ethanol (25 ml). The mixture that
takes initially a dark brown colour was heated at reflux
temperature and stirred overnight. Then, after ethanol
evaporation, chloroform (25 ml) was added and the solution
was filtered, to isolate (E)-12, 270 mg (92%) as a yellow
solid, mp 210–2128C (darkness at 2008C). IR (KBr): 1619
(CvN); 1576 and 1516 (CvC); 1231 (N–CH3); 1180
(þN–CH3); 1055 (C–I); 1000 (E-isomer); 816 (p-subst.
1,4-Di[(E)-4-(p-ethenylphenylethynyl)pyridinium iodide],
(E,E)-11. In a previously flamed three-necked flask, under
argon atmosphere, were placed a solution of cuprous
chloride (13.6 mg, 0.068 mmol) in anhydrous pyridine
(10 ml) and then oxygen was bubbled through the solution.
The mixture was heated at 408C and a solution of (E)-10
(65 mg, 0.181 mmol) in anhydrous pyridine (5 ml) was
added. The mixture was stirred for 4 h and after, solvent was
1
ArH). H NMR (MeOD): 8.75 (d, 2H, J¼6.8 Hz, H-3 Py);

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J. G. Rodrıguez et al. / Tetrahedron 59 (2003) 1021–1032
1031
8.21 (d, 2H, J¼6.8 Hz, H-2 Py); 7.90 (d, 1H, J¼16.3 Hz,
PhCHv); 7.89 (d, 2H, J¼8.4 Hz, H-3 Ph); 7.55 (d, 2H,
J¼8.4 Hz, H-2 Ph); 7.50 (d, 1H, J¼16.3 Hz, PyCHv); 4.38
(s, 3H, N–CH3). UV–visible (EtOH), lmax (nm): 223
(80225); 284 (27500); 355 (1260). Calcd for C14H13NI2: C,
37.44; H, 2.92; N, 3.12. Found: C, 37.18; H, 3.20; N, 2.94%.
Dimethylated salt (Z,Z)-15. IR (KBr): 1600, 1500 and 1450
(CvC, conj.); 1320 (N–CH3); 1180 (Pyþ–CH3); 975 and
880 (Py sust.); 840 and 830 (p-disubst.). 1H NMR (DMSO):
8.78 (d, 4H, J¼6.6 Hz, H-2 and H-6, Py); 7.83 (d, 4H,
J¼6.6 Hz, H-3 and H-5, Py); 7.57 (d, 4H, J¼8.3 Hz, H-2
and H-6, Ph); 7.34 (d, 4H, J¼8.3 Hz, H-3 and H-5, Ph); 7.23
(d, 2H, J¼12.3 Hz, Py–CHvCH, Z); 6.89 (d, 2H,
J¼12.3 Hz, Py–CHvCH, Z); 4.28 (s, 6H, CH3). MS
(FABþ): 438 (Mþ, 43); 423 (35); 219 (22). UV–visible
(CH2Cl2): 236 (6800); 292 (5080); 396 (6520 l mol21
cm21). Calcd for C33H26N2I2: C, 56.27; H, 3.72; N, 3.98.
Found: C, 56.09; H, 3.60; N, 3.78%.
Di-{4-[p-(2-ethenylphenyl)]pyridinium iodide}, (E,E)-13. A
solution of dichlorobis(triphenyl)phosphine nickel (II)
(245.1 mg, 0.377 mmol) in anhydrous THF (25 ml), tetra-
butylammonium iodide (139.4 mg, 0.377 mmol) and zinc
powder (36.6 mg, 0.56 mmol), under argon atmosphere,
was stirred for 30 min. The solution turns to red colour and
then a solution of (E)-4 (170 mg, 0.377 mmol) in anhydrous
THF (10 ml) was added. The mixture was stirred overnight
at room temperature. Finally, dichloromethane (25 ml) was
added, and the catalyst was filtered. Solvent was removed,
and compound 13 was obtained as a yellow solid, 82 mg
(68%). IR (KBr): 1624 (CvN); 1597 and 1516 (CvC);
1184 (þN–CH3); 997 (E-isomer); 838 (p-subst. ArH); 724
(Z-isomer). 1H NMR (MeOD): 8.86 (d, 4H, J¼6.7 Hz, H-3
Py, E-isomer); 8.82 (d, 4H, J¼6.7 Hz, H-3 Py, Z-isomer);
8.30 (d, 4H, J¼6.7 Hz, H-2 Py, E-isomer); 8.17 (d, 4H,
J¼6.7 Hz, H-2 Py, Z-isomer); 8.10 (d, 2H, J¼16.0 Hz, Ph–
CHv, E-isomer); 8.00–7.72 (m, 18H, Biph and Py–CHv
(E-isomer)); 7.31 (d, 2H, J¼11.6 Hz, Z-isomer); 7.09 (d,
2H, J¼11.6 Hz, Z-isomer); 4.41 (s, 6H, þN–CH3, E-
isomer); 4.37 (s, 6H, þN–CH3, Z-isomer). UV–visible
(EtOH), lmax (nm): 196 (1¼71460); 223 (1¼ 22085); 333
(1¼16500). Calcd for C28H26N2I2: C, 52.19; H, 4.07; N,
4.35. Found: C, 52.44; H, 3.93; N, 4.57%.
3.3.4. Charge–transfer complex between (Z,Z)-15 and
N,N,N0,N0-tetramethyl-p-phenylendiamine (TMPD), 16.
A hot solution of TMPD (100 mg, 0.61 mmol) in hot
acetonitrile (25 ml) was added to a nearly boiling solution of
(Z,Z)-15 (132 mg, 0.30 mmol) in acetonitrile (50 ml). The
mixture was stirred at reflux temperature for 2 h. The resulting
green solution was allowed to cool and then to evaporate
slowly to provide the complex 16 as a green solid. The solid
was continuously extracted with hexane in a soxhlet giving a
green solid with metallic bright. A 1:1 stoichiometry between
the components was deduced from the spectroscopic analysis.
IR (KBr): 1610, 1590, 1540, 1510 and 1460 (CvC, conj.);
1340 (N–CH3); 1185 and 1170 (Pyþ–CH3); 980, 950 and 880
(subst. Py);840(p-disubst.). 1H NMR (DMSO): 8.90(brs, 2H,
H-2 and H-6, Py); 8.25 (br s, 2H, H-2 and H-6, Py, complexed
ring); 8.05 (br s, 2H, H-3 and H-5, Py); 7.9–7.4 (m, 10H, Ph
and H-3 and H-5, Py, complexed ring); 7.36 (br d, 1H, Py–
CHvCH); 7.22 (br d, 1H, Py–CHvCH); 6.90 (br d, 1H, Py–
CHvCH, complexed ring); 6.72 (br d, 1H, Py–CHvCH,
complexed ring). UV–visible (CH2Cl2): 230 (6740), 265
(4400), 315 (5080), 401 (6600), 533 (660) and 639 nm
(905 l mol21 cm21). DSC: .1258C, broad endothermic peak
(decomposed). Calcd for C39H42N4I2: C, 57.08; H, 5.16; N,
6.83. Found: C, 57.16; H, 5.52; N, 6.54%.
3.3.3. Mono- and di-methylated salts, (Z,Z)-14 and (Z,Z)-
15, of (Z,Z)-1,4-di[(40-pyridylethenyl)-400-phenyl]-buta-
1,3-diyne, (Z,Z)-5. To a solution of (Z,Z)-5 (100 mg,
0.24 mmol) in ethanol (25 ml) and ethyl acetate (5 ml),
was added iodomethane (0.06 ml, 0.96 mmol). The mixture
was heated at reflux temperature and stirred overnight. After
cooling, a yellow precipitate was filtered and identified as
the dimethylated salt (Z,Z)-15, 70 mg (44%), mp 2308C
(dec.). The filtered solution was evaporated yielding an
orange solid identified as the monomethylated salt (Z,Z)-14,
70 mg (53%), mp 1808C (dec.).
3.3.5. Charge–transfer complex between (Z,Z)-15 and
7,7,8,8-tetracyano-p-quinodimethane (TCNQ), 17. A hot
solution of TCNQ (35 mg, 0.17 mmol) in hot acetonitrile
(15 ml) was added to a hot solution of (Z,Z)-15 (75 mg,
0.17 mmol) in acetonitrile (70 ml). The mixture was stirred
at reflux temperature for 20 min. After cooling the green
solution was slowly evaporated at room temperature
yielding the complex as a green solid, which was
continuously extracted with hexane in a soxhlet, giving
the complex 17 as a black–green solid. A 2:1 stoichiometry
between the components was deduced by spectroscopic and
combustion analysis. 1H NMR (DMSO): 8.9 (d, 4H, H-2 and
H-6, Py); 8.25 (d, 4H, H-3 and H-5, Py); 8.08 (m, 4H,
TCNQ); 7.9–7.5 (m, 8H, Ph); 7.39 (d, 2H, J¼12.5 Hz, Py–
CHvCH); 7.08 (d, 2H, J¼12.5 Hz, Py–CHvCH); 4.30 (s,
6H, CH3). UV–visible (CH2Cl2): 239 (6800), 400 (6520),
644 (780 l mol21 cm21). DSC: .1608C, decomposed.
Calcd for C57H31N10I2: C, 61.69; H, 2.82; N, 12.62.
Found: C, 61.45; H, 2.56; N, 12.25%.
Monomethylated salt (Z,Z)-14. IR (KBr): 1610, 1500 and
1460 (CvC and CvN, conj.); 1330 (N–CH3); 1185 (Pyþ–
CH3); 980, 890 and 880 (Py sust.); 835 (p-disust.).
1H NMR (MeOD): 8.91 (d, 2H, J¼6.7 Hz, H-2 y H-6,
methylated Py); 8.46 (d, 2H, J¼6.3 Hz, H-2 and H-6, Py);
7.99 (d, 2H, J¼6.7 Hz, H-3 and H-5, methylated Py); 7.54
(d, 2H, J¼8.7 Hz, H-2 and H-6, Ph near to methylated Py);
7.49 (d, 2H, J¼8.7 Hz, H-2 and H-6, Ph); 7.39 (d, 2H,
J¼8.7 Hz, H-3 and H-5, Ph near to methylated Py); 7.40 (d,
1H, J¼12.5 Hz, Me–Pyþ –CHvCH); 7.30 (d, 2H,
J¼8.7 Hz, H-3 and H-5 Ph); (7.19 (d, 2H, J¼6.3, H-3 and
H-5, Py); 6.97 (d, 1H, J¼12.5 Hz, Me–Pyþ–CHvCH);
6.89 (d, 1H, J¼12.0 Hz, Py–CHvCH); 6.78 (d, 1H,
J¼12.0 Hz, Py–CHvCH); 4.50 (s, 3H, CH3). UV–visible
(CH2Cl2): 230 (1, 7800); 292 (1, 4800); 340 (1, 5130);
385 (1, 6000 l mol21 cm21). Calcd for C31H23N2I: C,
67.64; H, 4.21; N, 5.09. Found: C, 67.47; H, 4.56; N,
5.05%.
Acknowledgements
We are greatly indebted to CICYT of Spain for financial
support (PB97-0060).

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1032
7. Ferraris, J. P.; Cowan, D. O.; Walatka, V.; Perlstein, J. J. Am.
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