Approaches to fused tetrathiafulvalene/tetracyanoquinodimethane systems

Article abstract of DOI:10.1002/ejoc.200900985

In the search for transformations of quinone moieties into the corresponding tetracyano-p-quinodimethane (TCNQ) systems, Knoevenagel-type condensations of 2-thioxo-1,3-dithiole-p-benzoquinone systems, TTF-p-benzoquinone dyads and a p-benzoquinone-TTF-p-be

Full text of DOI:10.1002/ejoc.200900985

FULL PAPER
DOI: 10.1002/ejoc.200900985
Approaches to Fused Tetrathiafulvalene/Tetracyanoquinodimethane Systems
Fréderic Dumur,[a] Xavier Guégano,[b] Nicolas Gautier,[a] Shi-Xia Liu,*[b] Antonia Neels,[c]
Silvio Decurtins,[b] and Piétrick Hudhomme*[a]
Keywords: Quinones / Quinodimethanes / Sulfur heterocycles / Charge transfer / Donor-acceptor systems
In the search for transformations of quinone moieties into the
corresponding tetracyano-p-quinodimethane (TCNQ) sys-
tems, Knoevenagel-type condensations of 2-thioxo-1,3-dithi-
ole-p-benzoquinone systems, TTF-p-benzoquinone dyads
and a p-benzoquinone-TTF-p-benzoquinone triad with ma-
lononitrile under different experimental conditions were in-
vestigated. In order to avoid the well-known Michael 1,4-
addition onto the quinone moiety, cyclopentadiene or cyclo-
hexadiene units were incorporated as protecting groups
through [4+2] Diels–Alder cycloadditions. On the one hand,
aromatization leading to fused 2-thioxo-1,3-dithiole-hydro-
quinones was observed in the presence of acetic acid and
pyridine. With use, on the other hand, of the nucleophilic
malononitrile anion, an unprecedented ring-opening process
of the 1,3-dithiole moiety occurred, affording stable ketene
imines. Finally, successful conversion of 1,3-dithiole-p-
benzoquinones into the corresponding TCNQ systems was
achived by treatment with malononitrile in the presence of
titanium(IV) chloride and pyridine as Lehnert’s reagents. All
new TCNQ derivatives were unambiguously characterized.
So far, the application of such experimental conditions to pro-
tected TTF-p-benzoquinone dyads and a p-benzoquinone-
TTF-p-benzoquinone triad has been unsuccessful, maybe
due to the high reactivity of the TTF moiety.
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2009)
1 (Scheme 1).[4] This rectification behaviour was observed
in a molecular junction device based on a donor–acceptor
(D-A) TTF-σ-trinitrofluorene dyad, which exhibits an ex-
tremely low HOMO–LUMO gap (0.3 V).[5] However, the
combination of a strong donor with a high HOMO, such
as TTF, and a strong acceptor with a low LUMO, such as
TCNQ, still represents a real synthetic challenge because of
the formation of stable and insoluble intermolecular
charge-transfer complexes between the two counterparts
prior to their covalent linking. Historically, the investigated
synthetic method consisted of using the weaker acceptor p-
benzoquinone and its subsequent conversion into TCNQ.
This protocol was considered in many cases, but seemed to
be quite challenging.[6]
An alternative strategy based on the use of covalent link-
ing at –100 °C between highly reactive functionalities
grafted onto both TTF and TCNQ moieties to obtain the
first well-characterized TTF-σ-TCNQ dyad 2 has been re-
ported.[7] Its electrochemical HOMO–LUMO gap
(0.17 eV), suggested as the lowest gap known in an organic
molecule, leads to spontaneous electron transfer inside this
dyad. More recently, the elaboration of the TCNQ-σ-TTF-
σ-TCNQ system 3, involving a rigid saturated bridge, has
been investigated and its bent structure was suggested to be
responsible for a 20% through-space intramolecular charge
transfer.[8] We have been interested in the synthetic chal-
lenge in obtaining the planar and fused TCNQ-TTF-
TCNQ and TTF-TCNQ systems 4 and 5, respectively, be-
cause these would be expected to exhibit low HOMO–
Introduction
Tetrathiafulvalene (TTF) and its derivatives were histori-
cally prepared for their applications as strong electron-do-
nor molecules for the development of electrically conduct-
ing materials such as the famous tetrathiafulvalene/tetracy-
ano-p-quinodimethane
(TTF-TCNQ)
intermolecular
charge-transfer complex.[1] During the last few years, there
has been increasing interest in the search for covalent link-
age of TTFs to electron-acceptor moieties, because of the
potential applications of such attractive materials in molec-
ular electronics and optoelectronics.[2] The performances of
the corresponding devices clearly depend on the energies of
relevant molecular orbitals and, as a result, molecular sys-
tems presenting low HOMO–LUMO gaps are of particular
importance.[3] Covalent attachment of TTF to TCNQ as
an electron acceptor was initiated in a theoretical paper by
Aviram and Ratner, who proposed the concept of a uni-
molecular rectifier represented by the TTF-σ-TCNQ system
[a] Université d’Angers, CNRS, Laboratoire Chimie et Ingénierie
Moléculaire d’Angers, CIMA UMR 6200,
2 Boulevard Lavoisier, 49045 Angers, France
Fax: +33-2-41735405
E-mail: pietrick.hudhomme@univ-angers.fr
[b] Departement für Chemie und Biochemie, Universität Bern,
Freiestrasse 3, 3012 Bern, Switzerland
E-mail: liu@iac.unibe.ch
[c] XRD Application LAB, CSEM Centre Suisse d’Electronique et
de Microtechnique SA
Jaquet-Droz 1, Case postale, 2002 Neuchâtel, Switzerland
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejoc.200900985.
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Results and Discussion
Our first investigations focused on conversion of com-
pound 6[11a,12] into the corresponding TCNQ derivative by
treatment with malononitrile. Despite intensive efforts and
modifications of the experimental conditions, no evidence
for the formation of compound 9 was found in the resulting
crude mixtures, consistently with previous observations of
side reactions in attempted transformations of p-benzo-
quinone derivatives into their TCNQ analogues
(Scheme 3).[13]
Scheme 3. Attempts to transform the 2-thioxo-1,3-dithiole-p-
benzoquinone 6 into its TCNQ analogue.
Scheme 1. TTF-TCNQ systems: the Aviram–Ratner molecular rec-
tifier conceptual model 1, molecules 2 and 3 described in the litera-
ture, and the fused TTF-TCNQ target molecules 4 and 5.
Such reactions are known to be highly dependent on sub-
stituent effects, steric hindrance induced by bulky groups
and side reactions leading to the decomposition of the qui-
none derivatives under strongly acidic or basic conditions.
Therefore, in order to perform the synthesis of the TCNQ
systems 4, 5 and 9, a Diels–Alder protecting group strategy
was investigated. Yamashita’s methodology, as shown in the
retrosynthetic Scheme (Scheme 4), consists of successive
Diels–Alder (with cyclopentadiene) and thermal retro-
Diels–Alder reactions.[14] This strategy was successfully ap-
plied for the preparation of quinonoid π-extended TTF sys-
tems after the Horner–Wadsworth–Emmons (HWE) reac-
tion used for the creation of the extended TTF core had
been found to be subject to an unexpected electron transfer
between the phosphonate anion and the quinone moi-
ety.[11a,15] Use of an initial Diels–Alder reaction with the
quinone derivatives avoids such side reactions, thanks to
the weaker electron-accepting abilities of the corresponding
cyclopentadiene adducts.
LUMO gaps. Up to now, only one striking example of a
fused π-conjugated molecule incorporating TTF and a
TCNQ-type bithienoquinoxaline has been reported, exhib-
iting electrochemically amphoteric properties with a small
HOMO–LUMO gap of 0.52 V.[9] Obviously, the annulation
of the D and A moieties into a planar configuration facili-
tates photoinduced intramolecular charge-transfer (CT)
processes. As confirmation of the importance of this pa-
rameter of planarity, electroactive A2D triads incorporating
one π-extended TTF unit and two tetracyano-p-anthraquin-
odimethane (TCAQ) units have been described, but negligi-
ble electronic interaction between the redox chromophores
was observed, due to the distortion of the molecule out of
planarity.[10]
Some of us were previously interested in systems incor-
porating moderate acceptors such as p-benzoquinone,
which can be used as precursors for targets 4 and 5. Conse-
quently, the fused 2-thioxo-1,3-dithiole-p-benzoquinone 6,
the TTF-p-benzoquinone (TTF-Q) dyads 7 and the p-
benzoquinone-TTF-p-benzoquinone (Q-TTF-Q) triad 8
were chosen as starting materials (Scheme 2).[11] In this
work we focus on the feasibility of transforming such qui-
none functionalities through Knoevenagel condensations
with malononitrile under different experimental conditions.
Scheme 4. Retrosynthetic analysis of the protection/deprotection
strategy used for the quinone unit.
For this strategy, retrosynthetic analysis of intermediates
10 and 11, precursors of targets 4 and 5, respectively, sug-
gests two different routes. In route A, the disconnection of
Scheme 2. Starting materials: the 2-thioxo-1,3-dithiole-p-benzo-
quinone 6, the TTF-p-benzoquinone (TTF-Q) dyads 7 and the p-
benzoquinone-TTF-p-benzoquinone (Q-TTF-Q) triad 8.
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Fused Tetrathiafulvalene/Tetracyanoquinodimethane Systems
Scheme 5. Retrosynthetic analysis of the fused TTF-TCNQ assemblies 4 and 5.
the TTF central double bond leads to the 2-(thi)oxo-1,3- Supporting Information) exhibits the molecular peak at m/z
dithioles 12 and 13 as starting materials and implies classi- = 270 and shows some characteristic fragmentation pat-
cal self- or cross-coupling reactions in the TTF series.[16] terns. The 1H and 13C NMR spectra measured in [D6]-
Route B corresponds to functionalization of the protected DMSO suggest the presence of the ketene imine function-
triad 14 and dyad 15, originating from the Q-TTF-Q 8 and ality rather than the malononitrile –CH(CN)2 group.
the TTF-Q 7, respectively (Scheme 5).
Firstly, the expected singlet characteristic of the –CH-
Here we focus on our efforts devoted to transformations (CN)2 group at around δ = 3.70 ppm is absent and has been
of quinone derivatives to produce the 2-(thi)oxo-1,3-di- replaced by a broad singlet at δ = 8.50 ppm corresponding
thioles 12 and 13, with application to the TTF analogues to both SH and NH labile protons. Secondly, this structure
10 and 11.
is confirmed by the HMBC and HMQC 2D 13C NMR
The starting material 16 (Scheme 6) is easily available spectra, which show three quaternary carbons at δ = 81.3,
from compound 6 through a [4+2] cycloaddition with 113.7 and 170.2 ppm for the –C(CN)=C=NH group.
freshly distilled cyclopentadiene, either in THF (94%)[11a]
or in Et2O (97%). The first attempts to transform its car-
bonyl groups into dicyanomethylene moieties were carried
out through a typical Knoevenagel reaction procedure with
malononitrile in the presence of a mixture of glacial acetic
acid and pyridine. Under such conditions, however, only
aromatization leading to compound 17 was observed, as
has also been reported in the literature for other cyclopenta-
diene adducts of quinone derivatives.[17] We noted that this
phenomenon was rapid in the presence of a glacial acetic
acid/pyridine mixture but that the kinetics of this same re-
action were slower in acetic acid medium. The synthetic
strategy then evolved with the objective of generating the
malononitrile anion in situ. Two equivalents of malononitr-
Scheme 6. Reagents and conditions: i) cyclopentadiene, Et2O, room
temperature, overnight, 97%; ii) CH2(CN)2, AcOH, pyridine,
ile anion, prepared by addition of LDA in THF at –78 °C,
70 °C; iii) CH2(CN)2, LDA, THF, –78 °C to room temperature,
then H+/H2O, 45 %.
were added to compound 16. Surprisingly, after hydrolysis
and purification by column chromatography, compound 18
was isolated in 45% yield. The spectral characterization was
The formation of compound 18 could be explained in
consistent with the formation of this stable conjugated ke- terms of the mechanism presented in Scheme 7. The nucleo-
tene imine derivative, and the EI mass spectrum (see the philic attack of the malononitrile anion should proceed
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through a Michael 1,4-addition, and the lithium alkoxide treatment with glacial acetic acid led to the iminium salt 23
could then rearrange with spontaneous elimination of CS2 in 44% yield for the two steps. Transformation into the 2-
to afford the stable conjugated ketene imine after hydrolysis. thioxo-1,3-dithiole 24 with sodium sulfide was followed by
oxidation with DDQ to furnish the fused 2-thioxo-1,3-dithi-
ole-p-benzoquinone 25. Diels–Alder cycloaddition could
then be performed, affording the required electrophilic sub-
strate 26 in excellent yield. Subsequent treatment with two
equivalents of malononitrile anion was carried out. Con-
sistently with the mechanism previously observed for com-
pound 18, ketene imine 27 was isolated in 31% yield after
purification by column chromatography. It should be noted
1
that in the case of compound 27, the H NMR spectrum
measured in CDCl3 exhibits two broad singlets at δ = 7.96
and 8.73 ppm, which could be ascribed to both NH and SH
groups. This compound was also accompanied by the major
compound 28, obtained in 47% yield and the result of an
unprecedented Knoevenagel condensation occurring on the
2-thioxo-1,3-dithiole functionality.
Scheme 7. Proposed mechanism for the formation of the ketene
The experimental conditions for the Knoevenagel con-
imine 18 through 1,4-addition and ring opening of the 1,3-dithiole
densation between malononitrile and compound 16 were
moiety.
further modified. Finally, 16 was converted into compound
To the best of our knowledge, this reaction constitutes 13 by treatment with titanium(IV) chloride and pyridine
an unprecedented ring opening in the 1,3-dithiole series.[18] (Lehnert’s reagents[20]). The reaction was optimized by use
We then extended this synthesis to a quinonic electrophile of a malononitrile/titanium(IV) chloride/pyridine ratio of
in which both hydrogen atoms were replaced with meth- 6:8:16 in dichloromethane at reflux and compound 13 was
oxycarbonyl groups (Scheme 8). The synthesis of the key isolated in 67% yield after column chromatography
intermediate 25 started with the 2,3-dimethoxycarbonyl p- (Scheme 9). The MALDI-MS reveals a peak at m/z =
benzoquinone 19, which was prepared from succinic anhy- 309.95 corresponding to removal of the cyclopentadiene
dride as described in the literature.[19] A Michael addition during this measurement. This phenomenon has been ob-
of the dithiocarbamate salt 20 onto the quinone derivative served previously in the study of quinonoid π-extended
19 in the presence of glacial acetic acid afforded intermedi- TTF systems.[15] The IR spectrum of compound 13 shows
ate 21 in excellent yield. This was further oxidized to 22 the CϵN stretching vibration band at 2218 cm–1, whereas
with p-benzoquinone, and subsequent cyclisation upon the intense C=O stretching vibration band of starting mate-
Scheme 8. Reagents and conditions: i) salt 20, AcOH, DMF/DMSO, 96%; ii) p-benzoquinone; iii) glacial AcOH, 44% from 21;
iv) Na2S·9H2O, MeOH, 96%; v) DDQ, THF, 90%; vi) cyclopentadiene, THF, 95%; vii) CH2(CN)2, BuLi, THF, –78 °C to room tempera-
ture, then H+/H2O, 31 % for 27 and 47% for 28.
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Fused Tetrathiafulvalene/Tetracyanoquinodimethane Systems
rial 16 at 1662 cm–1 has disappeared. The 13C NMR spec- vibration band at 2224 cm–1 and the C=O stretching vi-
trum reveals the CN groups at δ = 111 ppm and the thione bration band at 1676 cm–1. Transchalcogenation of com-
at δ = 201 ppm. Compound 13 underwent transchalcogen- pounds 30 and 31 afforded the 2-oxo-1,3-dithiole deriva-
ation to afford the 2-oxo-1,3-dithiole derivative 12 in 97% tives 32 and 33, respectively in 96% yields.
yield.
The structure of the 2-oxo-1,3-dithiole 32 was verified by
X-ray crystallography. Single crystals were obtained by slow
evaporation of a dichloromethane/acetone (1:1) solution of
compound 32. It crystallises in an orthorhombic polar
space group (Cmc 21) with one molecule in the asymmetric
unit. An ORTEP view of compound 32 shows the atomic
labelling scheme (Figure 1). The X-ray crystallographic
analysis reveals that the molecule adopts an endo configura-
tion. The central quinonoid ring is in a boat conformation
in order to minimize the steric strain between the cyano
groups and the adjacent atoms in peri positions. The angle
describing the molecular distortion from planarity for 32 is
γ = 24.4° (tilting of the dicyanomethylene groups with re-
spect to the C10–C10a–C2–C2a plane). The C2–C1 single
bond (1.502 Å) in the quinonoid ring is significantly shorter
than the C3–C2 single bond (1.573 Å) as a consequence of
the steric strains of the quinonoid ring. The intramolecular
Scheme 9. Reagents and conditions: i) CH2(CN)2, pyridine, TiCl4,
CH2Cl2, 0 °C, then reflux for 2 h, 67%; ii) Hg(OAc)2, glacial
AcOH, CH2Cl2, reflux, 2 h, 97%.
With the aim of extending this synthesis of fused 1,3-
dithiole-TCNQ systems, we performed the same synthetic
strategy but with protection with cyclohexa-1,3-diene in-
stead of cyclopentadiene (Scheme 10). The Diels–Alder re-
action between compound 6 and a slight excess of cy-
clohexa-1,3-diene led to the formation of the Diels–Alder
adduct 29 in 76% yield. Knoevenagel condensation was
carried out with use of a malononitrile/titanium(IV) chlo-
ride/pyridine ratio of 6:8:50 at room temperature in dichlo-
romethane and compound 30 was isolated in 74% yield.
The IR spectrum of compound 30 shows the CϵN stretch-
ing vibration band at 2225 cm–1.
By modification of the experimental conditions, the
dicyanomethylene compound 31 could be also isolated.
Knoevenagel condensation carried out on adduct 29 with a
malononitrile/titanium(IV) chloride/pyridine ratio of 1:8:16
led to the formation of 31 in 69% yield. Clearly, high di-
lution, a short reaction time and a stoichiometric amount
of malononitrile favour the formation of 31. Compound 31
1
was fully characterized by its MS and H NMR spectra, as
well as by X-ray diffraction analysis (see the Supporting
Information). Its IR spectrum shows the CϵN stretching omitted for clarity.
Figure 1. ORTEP representation (ellipsoids at 50% probability) of
the molecular structure of compound 32. Hydrogen atoms are
Scheme 10. Reagents and conditions: i) cyclohexa-1,3-diene, Et2O, overnight, 76%; ii) CH2(CN)2, pyridine, TiCl4, CH2Cl2, 0 °C, then
reflux for 2 h, 74%; iii) CH2(CN)2, pyridine, TiCl4, CH2Cl2, 0 °C, then reflux for 1 h, 69%; iv) Hg(OAc)2, glacial acetic acid, CH2Cl2,
reflux, 2 h, 96% for 32 and 33.
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S···N contacts (S1···N1 3.346 Å) are of the same order as
the sum of the corresponding van der Waals radii
(3.35 Å).[21]
As a result of the presence of the bulky group in the
structure of 32, no intermolecular short S···S contacts were
observed in the crystal packing (Figure 2). Along the c-axis,
the molecules are connected by short intermolecular inter-
actions between the oxygen and the C2–C2a single bond
(O···C2, O···C2a 3.204 Å). Along the a-axis, the molecules
are connected by C–H···N hydrogen bonds (C3–H3···N2
2.575 Å).
Figure 3. UV/Vis absorption spectra of compounds 6 (solid), 16
(dash-dotted), 25 (dotted) and 26 (short-dashed) in CH2Cl2 (c =
10–4 ).
Figure 4. UV/Vis absorption spectra of compounds 13 (solid) and
16 (dash-dotted) in CH2Cl2 (c = 10–4 ).
Figure 2. Crystal packing of compound 32.
30 and 31, respectively, with an absorption band at λmax
=
The electronic absorption spectra of compounds 6, 16,
25 and 26 in dichloromethane (c = 10–4 ) are shown in
Figure 3. The UV/Vis spectrum of compound 6 displays a
broad absorption band in the 400–600 nm region, centred
at 510 nm. This band is attributed to intramolecular charge
transfer from the 1,3-dithiole-2-thione moiety to the p-
benzoquinone core.[11c] This absorption band was blue-
shifted (λmax = 397 nm) for cycloadduct 16, as a conse-
quence of the decreased acceptor strength. It should be
noted that the UV/Vis spectrum of the quinonic derivative
25 also shows this broad absorption band, now centred at
λmax = 547 nm. This red-shift of the absorption band rela-
tive to that of compound 6 (∆λ = 37 nm) is consistent with
the increase in the accepting character of the quinone
moiety due to the presence of the two methoxycarbonyl
groups. This phenomenon is less important for compound
26 (λmax = 407 nm) than for the analogous protected com-
pound 16 (∆λ = 10 nm).
478 nm for 30 and at λmax = 449 nm for 31, in comparison
with the absorption spectrum of starting material 29 (Fig-
ure 5).
Figure 5. UV/Vis absorption spectra of compounds 29 (solid), 30
(dotted) and 31 (dash-dotted) in CHCl3 (c = 10–4 ).
The absorption spectrum of the bis(dicyanomethylene)
derivative 13 in dichloromethane shows an absorption peak
As an extension to this strategy for the transformation
at 482 nm. This band, red-shifted relative to that in com- of quinones into bis(dicyanomethylene) intermediates, the
pound 16, is attributed to intramolecular charge transfer preparation of Diels–Alder adducts 15 (Scheme 12, below)
from the 1,3-dithiole-2-thione moiety to the electron-with- from TTF-p-benzoquinone dyads and their subsequent
drawing [=C(CN)2] groups (Figure 4).
Knoevenagel condensation with malononitrile were investi-
The same trend was observed in the absorption spectra gated. Several TTF-p-benzoquinone dyads 7 were prepared
(in chloroform) of the bis(dicyanomethylene) and mon- by a procedure that some of us had previously developed
o(dicyanomethylene) cyclohexadiene Diels–Alder adducts for 7a (Scheme 11).[11c] The key step in obtaining dyads 7
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Fused Tetrathiafulvalene/Tetracyanoquinodimethane Systems
Scheme 11. Reagents and conditions: i) nBuLi, THF, –78 °C to room temperature, overnight, 90% for 36a, 75% for 36b, 83% for 36c,
88% for 36d, 22% for 36e, 84% for 36f; ii) nBu4NF, THF, then p-benzoquinone, 75% for 7a, 59% for 7b, 63% for 7c, 42% for 7d, 63%
for 7e, 55% for 7f.
involved HWE olefination to construct the TTF core[15a]
with Akiba’s phosphonate reagent.[22] The phosphonates
35a–f were synthesized by a well-known and efficient pro-
cedure.[23] The phosphonate carbanions generated in situ by
deprotonation (n-butyllithium) were treated with the 2-thi-
oxo-1,3-dithiole derivative 34[11c] to afford the TTF deriva-
tives 36 in good yields. In the case of 36b, the structure has
been confirmed by X-ray crystallography (see the Support-
ing Information). Removal of the silyl groups of 36 and
subsequent oxidation with p-benzoquinone afforded the
TTF-p-benzoquinone dyads 7 in good yields.
Figure 6. ORTEP representation (ellipsoids at 50% probability) of
the molecular structure of 15b. Hydrogen atoms are omitted for
clarity.
Diels–Alder reactions with dyads 7a–d in the presence of
excess freshly distilled cyclopentadiene afforded the ex-
The mass spectra of compounds 15a–d each display the
pected Diels–Alder cycloadducts 15a–d in high yields monoisotopic molecular peak with the concomitant pres-
(Scheme 12). It should be noted that the multi-step trans- ence of the peak resulting from the retro-Diels–Alder frag-
formation of compound 36a into the protected compound mentation at m/z – 66. The UV/Vis spectra in dichlorometh-
15a could be carried out in an improved overall 79% yield ane each show an intramolecular charge-transfer band
without isolation of the intermediate TTF-p-benzoquinone around 600 nm (λmax = 603 nm for 15a, 582 nm for 15b,
7a.
586 nm for 15d), whereas the corresponding TTF-p-benzo-
Single crystals were obtained by slow evaporation of a quinone system 7a exhibits an intramolecular charge-trans-
dichloromethane/hexane (1:3) solution of 15b. Compound fer centred at λmax = 839 nm in dichloromethane (see the
15b crystallises in a monoclinic cell (C2/c) with one mole- Supporting Information).
cule in the asymmetric unit (Figure 6). The X-ray crystallo-
Knoevenagel condensations of 15a–d with malononitrile
graphic analysis reveals that 15b adopts an endo configura- were attempted either in the presence of glacial acetic acid
tion, this stereochemistry being consistent with the 1H and pyridine or by addition of the malononitrile anion gen-
NMR spectroscopy results.
erated by addition of LDA at –78 °C. The expected
Scheme 12. Reagents and conditions: i) cyclopentadiene, CH2Cl2 or THF, 93% for 15a, 92% for 15b, 85% for 15c, 74% for 15d.
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bis(dicyanomethylene) compounds 11a–d, however, were
not detected under such experimental conditions. The con-
densations were then attempted with use of different ma-
lononitrile/titanium(IV) chloride/pyridine ratios in dichlo-
romethane at room temperature or at reflux, as in the exper-
imental procedure used for compounds 13 and 30. Under
such conditions, the solutions turned green and thin layer
chromatography indicated the disappearance of the starting
materials 15. The solutions were washed with water and
concentrated to afford some green powders. The MALDI
MS and the 1H NMR spectra, however, showed no evidence
of the formation of the expected products. This could be
attributed to the sensitivity of the TTF nucleus to the strong
Lewis acid titanium(IV) chloride, which led to the decom-
position of starting materials and therefore prevented the
conversion into dicyanomethylene groups.
Conclusions
It has been shown that condensations between p-benzo-
quinones and malononitrile, depending on the experimental
conditions, can proceed through the expected Knoevenagel
condensation in the presence of Lehnert’s reagents to afford
the corresponding TCNQ analogues. Surprisingly, under
different conditions Michael addition can predominate to-
gether with the subsequent ring opening of the 1,3-dithiole
moieties, leading to unprecedented stable ketene imines. So
far, the application of Knoevenagel condensation condi-
tions to protected TTF-p-benzoquinone dyads and a p-
benzoquinone-TTF-p-benzoquinone triad has been unsuc-
cessful, maybe due to the high reactivity of the TTF moiety.
However, attachment of the electron-rich 2-thioxo-1,3-di-
thiole moiety to TCNQ electron acceptors leads to the for-
mation of the highly conjugated compounds 12, 13 and 30–
33, in which the remarkable redox properties are combined
with strong photoinduced intramolecular CT transitions.
Such a combination of optical and electronic properties
makes these compounds promising as nonlinear optical and
electro-optical materials. As a consequence, tests of the per-
formance of these π-conjugated materials for charge trans-
port in molecular electronic applications will be of particu-
lar interest.
The p-benzoquinone-TTF-p-benzoquinone triad
8
(Scheme 13) was synthesized by a three-step, one-pot se-
quence. Methanolysis of compound 37 and subsequent
acidic treatment afforded the bis(hydroquinone)-TTF inter-
mediate. Subsequent addition of DDQ to the solution led
to the triad 8, which was isolated in 88% yield after chro-
matographic purification on neutral alumina gel. We should
note that this constitutes an improvement on the previous
synthesis reported by some of us.[11c] Diels–Alder reactions
between triad 8 and cyclopentadiene afforded the expected
bis-Diels–Alder adduct 14 in high yield (Scheme 13). The
1H NMR spectrum corresponds to the superposition of two
isomers in a 65:35 ratio. This could be attributed to a mix-
ture of two stereoisomers (endo-syn-endo and endo-anti-
endo adducts). These isomers could be separated by thin-
Experimental Section
General Procedures: All reagents were of commercial quality and
were used without purification. Tetrahydrofuran was obtained by
layer chromatography with dichloromethane as the eluent distillation from Na/benzophenone. Thin-layer chromatography
(TLC) was performed on aluminium sheets coated with silica gel
(60 F254, Merck 5554) or ALUGRAM® SIL G/UV254 (Macherey–
Nagel) and on alumina plates (0.20 or 0.25 mm, POLYGRAM®
ALOX N/UV254, Macherey–Nagel). Column chromatography was
carried out on silica gel 60 (Merck 9385, 230–400 mesh), on neutral
and basic aluminium oxide (CAMAG) or on Florisil (Acros 200–
400 mesh). Melting points were determined with a Reichert hot-
plate microscope or a Büchi 510 apparatus and are uncorrected.
1H (300, 400, 500 MHz), and 13C (75, 100, 125 MHz) NMR spectra
were recorded variously with a Bruker Avance 300, a Bruker Av-
ance II 400 or a Bruker Avance II 500 instrument, with tetrameth-
ylsilane (TMS) or the residual solvent as the internal standard. In-
frared spectra were measured with a Perkin–Elmer Spectrum One
FT-IR spectrometer or a Perkin–Elmer 841 spectrometer as KBr
(Rf = 0.46 and 0.55). The Knoevenagel condensation condi-
tions used for the synthesis of compound 13 were applied
with use of different malononitrile/titanium(IV) chloride/
pyridine ratios in dichloromethane at room temperature or
at reflux, but no evidence for the formation of the expected
product 10 was found, consistently with our observations
for the attempted transformations of compounds 15 to pro-
duce derivatives 11.
pellets. UV/Vis spectra were obtained with
a Perkin–Elmer
Lambda 10 or a Perkin–Elmer Lambda 19 spectrometer. Mass
spectra were obtained with an AutoSpecQ or a JEOL JMS 700B/
ES spectrometer for the EI ionisation mode (70 eV). MALDI MS
were carried out with a FTMS 4.7T BioAPEX II spectrometer with
dithranol, DHB or DCTB as matrices. MALDI-TOF MS were
measured either with an Axima spectrometer from Shimadzu with
a nitrogen laser (337 nm) in the linear mode or with a Brucker
Biflex III spectrometer with DCTB, dithranol and DHB as matri-
ces. Elemental analyses were either measured with a Carlo Erba
EA 1110 CHNS instrument or were performed by the Central Ser-
vice of Microanalysis of the CNRS (France).
Scheme 13. Reagents and conditions: i) MeONa, MeOH/THF,
ii) PTSA, iii) DDQ, 88% from 37; iv) cyclopentadiene, CH2Cl2,
overnight, 94%.
Compound 7a: Bu4NF (0.26 mL, 0.26 mmol) was added to a solu-
tion of TTF 36a (100 mg, 0.1 mmol) in dichloromethane (10 mL).
6348
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Fused Tetrathiafulvalene/Tetracyanoquinodimethane Systems
The mixture was stirred for 30 min at room temperature and p-
benzoquinone (11 mg, 0.1 mmol) was added. Stirring was contin-
ued for a further 5 min. Purification by column chromatography
(Florisil gel, 100–200 mesh) with dichloromethane as the eluent was
followed by recrystallization from dichloromethane/petroleum
ether to afford compound 7a as green crystals (38 mg, 75%). 1H
NMR (500 MHz, CDCl3): δ = 0.92 (t, J = 7.1 Hz, 6 H, CH3CH2),
1.30–1.50 (2ϫm, 8 H, CH3CH2CH2), 1.63 (q, J = 7.1 Hz, 4 H,
CH2CH2S), 2.81 (t, J = 7.1 Hz, 4 H, CH2S), 6.75 (s, 2 H,
CH=CH) ppm. 13C NMR (125 MHz, CDCl3): δ = 14.2, 22.2, 29.5,
30.7, 36.4, 110.2, 115.4, 128.1, 143.6, 136.8, 177.9 ppm. IR (KBr):
136.8, 143.6, 177.9 ppm. IR (KBr): ν = 1648 (C=O) cm–1. MS
˜
(MALDI, dithranol as matrix, positive mode): calcd. for [M +
2H]+ 686.24; found 686.07.
Compound 7f: Bu4NF (2.6 mL, 2.6 mmol) was added to a solution
of TTF 36f (840 mg, 1.03 mmol) in dichloromethane (80 mL). The
mixture was stirred for 30 min and p-benzoquinone (112 mg,
1.03 mmol) was added. After concentration, the residue was puri-
fied by column chromatography on Florisil gel with dichlorometh-
ane/ethyl acetate (9:1) as a mixture of eluents to afford 7f (190 mg,
55%) as a green powder. Compound 7f was insoluble in solvents
commonly used for NMR spectroscopy. IR (KBr): ν = 1631
˜
ν = 1648 (C=O) cm–1. MS (EI): m/z (%) = 488 (100) [M]+·, 384
˜
(C=O) cm–1. MS (EI): m/z (%) = 334 (100) [M]+·, 304 (12), 196 (40),
152 (20), 120 (8), 108 (18). C14H16O2S4 (333.93): calcd. C 50.28, H
1.81, S 38.35; found C 50.16, H 1.86, S 38.15.
(13), 347 (12), 259 (10), 226 (22). C20H24O2S6 (488.77): calcd. C
49.15, H 4.95, S 39.36; found C 49.11, H 5.00, S 37.92.
Compound 7b: Bu4NF (0.3 mL, 0.303 mmol) was added to a solu-
tion of TTF 36b (100 mg, 0.116 mmol) in tetrahydrofuran (10 mL).
The mixture was stirred for 30 min and p-benzoquinone (18 mg,
0.166 mmol) was added. After concentration, the residue was redis-
solved in dichloromethane and washed with water and brine. The
organic layer was dried with sodium sulfate and the solvents were
evaporated. The green oil was purified by column chromatography
on neutral aluminium oxide gel with dichloromethane/ethyl acetate
(1:1) as a mixture of eluents to afford 7b (26 mg, 59%) as a green
powder. 1H NMR (300 MHz, CDCl3): δ = 2.42 (s, 6 H, SCH3),
Compound 8: Freshly prepared sodium methoxide (2.5 mL,
1.86 mmol) was added to a solution of compound 37 (100 mg,
0.186 mmol) in tetrahydrofuran (12 mL). The mixture was stirred
at 60 °C for 1 h, followed by the addition of p-toluenesulfonic acid
(354 mg, 1.86 mmol). The resulting solution was allowed to cool to
room temperature and DDQ (106 mg, 0.466 mmol) was added. The
mixture was stirred for 2 h. After evaporation of the solvent, the
residue was redissolved in dichloromethane and washed with water
and brine. The organic layer was dried with sodium sulfate and
the solvents were evaporated. The crude product was purified by
chromatography on neutral alumina gel with dichloromethane as
eluent to afford triad 8 (60 mg, 88%) as a blue-black powder. Spec-
troscopic characterizations are in agreement with those reported
previously.[11c]
6.76 (d, J = 7.5 Hz, 2 H, =CH) ppm. IR (KBr): ν
= 1651
˜
max
(C=O) cm–1. MS (MALDI, DCTB as matrix, positive mode) calcd.
for [M + 2H]+ 377.900; found 377.900.
Compound 7c: Bu4NF (0.57 mL, 0.57 mmol) was added to a solu-
tion of TTF 36c (200 mg, 0.219 mmol) in tetrahydrofuran (15 mL).
The mixture was stirred for 1 h and p-benzoquinone (40 mg,
0.370 mmol) was added. After concentration, the residue was redis-
solved in dichloromethane and washed with water and brine. The
organic layer was dried with sodium sulfate and the solvents were
evaporated. The black oil was purified by column chromatography
on neutral aluminium oxide gel with dichloromethane as eluent to
afford 7c (58 mg, 63%) as a dark green powder. 1H NMR
(300 MHz, CDCl3): δ = 1.04 (t, J = 7 Hz, 6 H, CH3), 1.69 (sextet,
J = 7.2 Hz, 4 H, CH2), 2.83 (t, J = 7 Hz, 4 H, SCH2), 6.75 (d, J =
7.3 Hz, 2 H, =CH) ppm.
Compound 12: A mixture of compound 13 (380 mg, 1 mmol), mer-
cury(II) acetate (636 mg, 2 mmol) in dichloromethane (80 mL) and
glacial acetic acid (40 mL) was heated at reflux for 2 h. The re-
sulting orange solution was extracted several times with dichloro-
methane. The combined organic layers were washed with water and
brine and dried with sodium sulfate, and the solvents were evapo-
rated. The orange residue was chromatographed on silica gel with
elution with dichloromethane/hexane (5:1) to afford compound 12
(349 mg, 97%) as red-orange microcrystals. 1H NMR (300 MHz,
CDCl3): δ = 1.75 (br. s, 2 H, CH2), 3.64–3.65 (m, 2 H, CH), 3.90–
3.91 (m, 2 H, CH), 5.98–5.99 (m, 2 H, =CH) ppm.
Compound 7d: Bu4NF (0.6 mL, 0.6 mmol) was added to a solution
of TTF 36d (200 mg, 0.234 mmol) in tetrahydrofuran (15 mL). The
mixture was stirred for 1 h and p-benzoquinone (38 mg,
0.351 mmol) was added. After concentration, the residue was redis-
solved in dichloromethane and washed with water and brine. The
organic layer was dried with sodium sulfate and the solvents were
evaporated. The green oil was purified by column chromatography
on neutral aluminium oxide gel with dichloromethane/ethyl acetate
(1:1) as a mixture of eluents to afford 7d (36 mg, 42%) as a green
Compound 13: Titanium(IV) chloride (0.875 mL, 8 mmol) was
added dropwise at 0 °C to a solution of compound 16 (280 mg,
1 mmol) in dichloromethane (40 mL). The reaction mixture was
stirred for 15 min, followed by the successive addition of malonon-
itrile (396 mg, 6 mmol) in dichloromethane (10 mL) and pyridine
(1.3 mL, 16 mmol) in dichloromethane (15 mL) over 15 min. The
mixture was heated at reflux for 2 h. The resulting black residue
was poured into ice/water and extracted with dichloromethane. The
combined organic layers were washed with water and brine and
dried with sodium sulfate, and the solvents were evaporated. The
black residue was purified by chromatography on silica gel with
dichloromethane/hexane (2:1, v/v) as a mixture of eluents to afford
compound 13 (252 mg, 67%) as a black solid. 1H NMR (400 MHz,
CDCl3): δ = 1.74–1.76 (m, 2 H, CH2), 3.65–3.66 (m, 2 H, CH),
3.89–3.91 (m, 2 H, CH), 6.05 (s, 2 H, =CH) ppm. 13C NMR
(100 MHz, CDCl3): δ = 45.0, 50.3, 53.0, 85.9, 111.6, 111.9, 135.5,
powder. 1H NMR (300 MHz, CDCl3):
SCH2CH2S), 6.75 (d, J = 7.5 Hz, 2 H, =CH) ppm.
δ = 3.31 (s, 4 H,
Compound 7e: Bu4NF (0.44 mL, 0.44 mmol) was added to a solu-
tion of TTF 36e (200 mg, 0.17 mmol) in dichloromethane (20 mL).
The mixture was stirred for 30 min and p-benzoquinone (18.7 mg,
0.173 mmol) was added. After concentration, the residue was puri-
fied by column chromatography on Florisil gel with dichlorometh-
ane as the eluent to afford 7e (74 mg, 63%) as green crystals; m.p.
72 °C (dichloromethane/petroleum ether). 1H NMR (500 MHz,
CDCl3): δ = 0.87 (t, J = 7 Hz, 6 H, CH3), 1.26–1.29 (m, 32 H,
144.3, 159.0, 201.1 ppm. IR (KBr):
ν = 2218 (CN), 1087
˜
(C=S) cm–1.
Compound 14: Freshly distilled cyclopentadiene (0.05 mL,
CH2), 1.39–1.42 (m, 4 H, SCH2CH2CH2), 1.59–1.65 (m, 4 H, 0.61 mmol) was added dropwise to a solution of triad 8 (20 mg,
SCH2CH2), 2.81 (t, J = 7.3 Hz, 4 H, SCH2), 6.76 (s, 2 H, =C– 59.4 µmol) in dichloromethane (3 mL). The green mixture was
H) ppm. 13C NMR (125 MHz, CDCl3): δ = 14.1, 22.7, 28.5, 29.1,
29.3, 29.5, 29.6, 29.65, 29.7, 29.8, 31.9, 36.4, 105.2, 115.4, 128.1,
stirred overnight. The solvent was evaporated under high vacuum
to afford, after chromatography on neutral aluminium oxide with
Eur. J. Org. Chem. 2009, 6341–6354
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
6349

S.-X. Liu, P. Hudhomme et al.
FULL PAPER
dichloromethane as eluent, compound 14 (27.7 mg, 94%) as a blue
overnight at room temperature and the solvent was evaporated un-
powder. 1H NMR (300 MHz, CDCl3): δ = 1.46 (35%) and 1.49 der high vacuum. The residue was purified by chromatography on
(65%) (m, 2 H), 1.57 (65%) and 1.61 (35%) (t, J = 1.8 Hz, 2 H,
CH2), 3.34 (dd, J = 1.2 and 2.3 Hz, 4 H, CH–CO), 3.56 (m, 4 H,
–CH–CH2), 6.12 (65%) and 6.13 (35%) (2ϫt, J = 1.9 Hz, 4 H,
=CH) ppm. 13C NMR (75 MHz, CDCl3): δ = 49.1, 49.2, 50.1,
135.2, 150.8, 189.2 ppm (some quaternary carbons are missing). IR
neutral aluminium oxide with dichloromethane as eluent to afford
compound 15d (19 mg, 74%) as a blue-green powder. 1H NMR
(300 MHz, CDCl3): δ = 1.43 (br. d, J = 7.9 Hz, 1 H from CH2
group), 1.55 (br. d, J = 7.9 Hz, 1 H from CH2 group), 3.34 (br. dd,
J = 1.5, 2.2 Hz, 2 H, CH), 3.29 (s, 4 H, SCH2CH2S), 6.09 (br. s, 2
H, CH), 3.54 (s, 2 H, =CH) ppm.
(KBr): ν = 1656 (C=O) cm–1. MS (EI): m/z (%) = 496 (2) [M]+·,
˜
430 (12), 364 (100), 226 (36), 66 (53). MS (FAB+ mNBA): m/z (%)
= 496 (75) [M]+·, 430 (42), 419 (45), 364 (78), 307 (100). MS
(MALDI, DHB as matrix, positive mode) calcd. for C24H16O4S4
495.993; found 495.990.
Compound 17: A solution of compound 16 (270 mg, 0.96 mmol)
and malononitrile (145 mg, 2.2 mmol) in glacial acetic acid (5 mL)
and pyridine (5 mL) was heated at 70 °C for 1 h. After addition of
dichloromethane (100 mL), the organic layer was washed with
water (2ϫ15 mL), an aqueous NaHCO3 saturated solution
(2ϫ15 mL) and water (15 mL) and dried with magnesium sulfate,
and the solvents were evaporated. The residue was purified by
chromatography on silica gel with dichloromethane/ethyl acetate
(9:1) as a mixture of eluents to afford compound 17 as white crys-
tals (221 mg, 82%); m.p. 234 °C (dec.). 1H NMR (500 MHz,
CD3COCD3): δ = 2.08 (dd, J = 7.3, 9.2 Hz, 2 H, CH2), 4.27 (t, J
= 7.3 Hz, 2 H, CH2–CH), 6.77 (s, 2 H, HC=CH), 9.81 (s, 2 H,
OH) ppm. 13C NMR (125 MHz, CD3COCD3): δ = 47.8, 69.0,
Compound 15a: Freshly distilled cyclopentadiene (0.02 mL,
0.25 mmol) was added dropwise to a solution of dyad 7a (25 mg,
51 µmol) in tetrahydrofuran (10 mL). The mixture was stirred for
30 min at room temperature and the solvent was evaporated under
high vacuum. The residue was purified by chromatography on silica
gel with dichloromethane/petroleum ether (1:1, v/v) as a mixture of
eluents to afford compound 15a (26 mg, 93%) as a blue powder;
m.p. 66 °C (dichloromethane/petroleum ether). 1H NMR
(500 MHz, CDCl3): δ = 0.89 (t, J = 7 Hz, 6 H, CH3CH2), 1.29–
1.39 (m, 9 H, CH3CH2CH2 and 1 H from CH2 group), 1.47 (d, J 127.2, 138.5, 139.1, 143.1, 214.9 ppm. IR (KBr): ν = 3387 (OH),
˜
= 8.7 Hz, 1 H, 1 H from CH2 group), 1.62 (q, J = 7 Hz, 4 H, 1071 (C=S) cm–1. MS (EI): m/z (%) = 280 (72) [M]+·, 203 (33), 171
CH2CH2S), 2.79 (t, J = 7 Hz, 4 H, CH2S), 3.33 (dd, J = 1.2, 2.3 Hz,
2 H, CH–CO), 3.55 (br. s, 2 H, CH–CH2), 6.12 (br. s, 2 H,
CH=CH) ppm. 13C NMR (125 MHz, CDCl3): δ = 13.9, 22.2, 29.4,
30.6, 36.4, 49.1, 49.2, 50.1, 106.2, 115.4, 127.9, 135.2, 151.0,
(13), 118 (10), 20 (100).
Compound 18: LDA (2  solution in hexane, 0.62 mL, 1.24 mmol)
was added under nitrogen at –78 °C to a solution of malononitrile
(74.4 mg, 1.13 mmol) in anhydrous tetrahydrofuran (10 mL). After
the system had been stirred at –78 °C for 10 min, a solution of
compound 16 (158 mg, 0.56 mmol) in tetrahydrofuran (15 mL) was
added dropwise. The reaction mixture was stirred at –78 °C for 1 h
30, and was then allowed to stand at room temperature. After hy-
drolysis with an aqueous saturated ammonium chloride solution
and extraction with ethyl acetate, the organic layer was dried with
magnesium sulfate and the solvent was concentrated under vac-
uum. The residue was purified by chromatography on silica gel with
dichloromethane/ethyl acetate (4:1) as a mixture of eluents to af-
ford compound 18 as a yellow powder (68 mg, 45%); m.p. 258 °C
189.3 ppm. IR (KBr): ν = 1662 (C=O) cm–1. MS (EI): m/z (%) =
˜
554 (65) [M]+·, 488 (100), 384 (10), 350 (10), 199 (15), 137 (12).
C25H30O2S6 (554.06): calcd. C 54.11, H 5.45, S 34.67; found C
53.70, H 5.62, S 33.92.
Compound 15b: Freshly distilled cyclopentadiene (0.03 mL,
0.37 mmol) was added dropwise to a solution of dyad 7b (20 mg,
53.1 µmol) in dichloromethane (3 mL). The mixture was stirred
overnight. The solvent was evaporated under high vacuum to af-
ford, after chromatography on neutral aluminium oxide with
dichloromethane as eluent, compound 15b (21.6 mg, 92%) as a
1
blue green powder; m.p. 154 °C. H NMR (300 MHz, CDCl3): δ =
(dichloromethane/ethyl
acetate).
1H
NMR
(400 MHz,
1.46 (br. d, J = 7.9 Hz, 1 H from CH2 group), 1.57 (br. d, J =
7.9 Hz, 1 H from CH2 group), 2.41 (s, 6 H, SCH3), 3.32 (br. dd, J
CD3SOCD3): δ = 1.43 (d, J = 8.4 Hz, 1 H, 1 H from CH2 group),
1.53 (d, J = 8.4 Hz, 1 H from CH2 group), 3.34 (m, 2 H, CH–CH–
= 1.5 and J = 2.2 Hz, 2 H, CH), 3.54 (s, 2 H, CH–CO), 6.11 (br. CO), 3.38 (d, J = 5.4 Hz, 2 H, CH–CH–CO), 6.05 (d, J = 7.2 Hz,
s, 2 H, =CH) ppm. IR (KBr): ν = 1658 (C=O) cm–1. MS (MALDI, 2 H, HC=CH), 8.47 (br. s, 2 H, NH + SH) ppm. 13C NMR
DCTB as matrix, positive mode) calcd. for C17H14O2S6 441.931; (100 MHz, CD3SOCD3): δ = 47.6, 47.9, 48.4, 49.0, 50.0 (CH and
˜
found 441.932. Single crystals suitable for X-ray analysis were ob-
tained by slow evaporation of a dichloromethane/hexane (1:3) solu-
tion of compound 15b.
CH2), 81.3 [–C(CN)=C=NH], 113.7 (CN), 131.6 (=C–SH), 134.9
(2ϫ=CH), 143.8 [=C–C(CN)=], 170.3 [–C(CN)=C=NH], 189.6
(C=O), 191.6 (C=O) ppm. IR (KBr): ν = 3422, 3324, 3209, 2216
˜
(CN), 1671, 1643, 1627, 1540, 1508, 1442 cm–1. MS (EI, positive
mode): m/z (%) = 270 (46) [M]+·, 242 (10), 204 (86), 176 (29), 148
(16), 121 (7), 66 (100). C14H10N2O2S (270.05): calcd. C 62.21, H
3.73, N 10.36, S 11.86; found C 62.06, H 3.84, N 10.32, S 11.98.
Compound 15c: Freshly distilled cyclopentadiene (0.2 mL,
2.45 mmol) was added dropwise to a solution of dyad 7c (193 mg,
446 µmol) in dichloromethane (15 mL). The mixture was stirred for
2 h at room temperature. The solvent was evaporated under high
vacuum. The residue was purified by chromatography on neutral
aluminium oxide with dichloromethane/hexane (1:1) as a mixture
of eluents to afford compound 15c (189 mg, 85%) as a blue powder.
Compound 21: A solution of compound 19 (4.63 g, 1 mmol) in
glacial acetic acid (10 mL) and DMF (10 mL) was added at 0 °C
to a solution of the dithiocarbamate salt 20 (4.63 g, 0.019 mol) in
1H NMR (300 MHz, CDCl3): δ = 1.01 (t, J = 7.2 Hz, 6 H, CH3), a mixture of DMF (10 mL) and DMSO (6 mL). The solution was
1.46 (br. d, J = 7.9 Hz, 1 H from CH2 group), 1.55 (br. d, J =
7.9 Hz, 1 H from CH2 group), 1.63 (sextet, J = 7.3 Hz, 4 H, CH2), precipitate was filtered to afford compound 21 as yellow crystals
2.77 (t, J = 7.2 Hz, 4 H, SCH2), 3.31 (br. dd, J = 1.5 Hz and J = (6.43 g, 96%); m.p. 166 °C (ethyl acetate). Compound 21 was insol-
stirred for 3 h at room temperature. After addition of water, the
2.2 Hz, 2 H, CH), 3.54 (s, 2 H, CH–CO), 6.11 (br. t, J = 1.7 Hz, 2 uble in solvents commonly used for NMR spectroscopy.
H, =CH) ppm.
Compound 23: p-Benzoquinone (1.95 g, 0.018 mol) was added to a
Compound 15d: Freshly distilled cyclopentadiene (0.03 mL,
0.37 mmol) was added dropwise to a solution of dyad 7d (22.5 mg,
60.1 µmol) in dichloromethane (3 mL). The mixture was stirred
suspension of compound 21 (6.43 g, 0.018 mol) in methanol
(120 mL). A bordeaux precipitate appeared and the mixture was
stirred for an additional 30 min and then filtered. The precipitate
6350
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Fused Tetrathiafulvalene/Tetracyanoquinodimethane Systems
was washed with methanol. After its dissolution in the minimum
possible amount of glacial acetic acid, the solution was heated for
10 min at 90 °C. After concentration under vacuum and precipi-
tation with ethyl acetate, compound 23 was isolated as yellow crys-
tals (3.55 g, 44%) that were used without further purification.
Compound 23 was insoluble in solvents commonly used for NMR
H, CH3), 3.67 (s, 3 H, CH3), 6.15 (s, 2 H, H–C=C–H), 7.96 (s, 1
H, NH), 8.73 (br. s, 1 H, SH) ppm. IR (KBr): ν = 2213 (CN), 1752
˜
(C=O ester), 1657 (C=O quinone) cm–1. MS (EI): m/z (%) = 386
(14) [M]+·, 355 (15), 327 (25), 322 (25), 320 (26), 295 (48), 289 (60),
174 (31), 109 (25), 66 (100). C18H14N2O6S (386.06): calcd. C 55.95,
H 3.65, N 7.25, S 8.30; found C 55.72, H 3.91, N 7.13, S 8.11.
spectroscopy. IR (KBr): ν = 2962 (OH), 1716 (C=O ester), 1558
˜
Compound 28: Yellow crystals (50 mg, 47%); m.p. 176 °C. 1H NMR
(500 MHz, CDCl3): δ = 1.80 (m, 1 H, 1 H from CH2 group), 2.59
(m, 1 H, 1 H from CH2 group), 3.73 (s, 6 H, CH3), 3.75 (m, 2 H,
CH–C–CO2Me), 6.22 (s,
(125 MHz, CDCl3): δ = 47.7, 52.5, 53.8, 70.2, 111.4, 138.8, 148.9,
(C=O) cm–1. MS (MALDI, dithranol as matrix, positive mode):
m/z (%) = 384 [M – OAc]+. C18H21NO8S2 (443.07): calcd. C 48.75,
H 4.77, N 3.16; found C 48.82, H 4.68, N 3.36.
2
H, H–C=C–H) ppm. 13C NMR
Compound 24: Sodium sulfide nonahydrate (3.96 g, 16.5 mmol) was
added to a solution of the iminium salt 23 (1.86 g, 4.2 mmol) in
methanol (20 mL). After stirring at room temperature for 5 h, the
solution was poured into a mixture of glacial acetic acid (10 mL)
and water (150 mL). The precipitate was filtered, washed with
water and dried under vacuum. Compound 24 was isolated as yel-
low crystals (1.32 g, 96%); m.p. 244 °C (dec.). 1H NMR (500 MHz,
CDCl3): δ = 3.93 (s, 6 H, CH3), 9.50 (br. s, 2 H, OH) ppm. 13C
NMR (125 MHz, CDCl3): δ = 53.2, 110.4, 135.1, 145.7, 168.9,
168.8, 184,4 ppm. IR (KBr): ν = 2213 (CN), 1761 (C=O ester),
˜
1669 (C=O quinone) cm–1. MS (EI): m/z (%) = 428 (17) [M]+·, 368
(12), 363 (25), 351 (15), 336 (34), 331 (72), 299 (48), 244 (14), 108
(19), 66 (100). C19H12N2O6S2 (428.01): calcd. C 53.27, H 2.82, N
6.54, S 14.97; found C 53.41, H 3.08, N 6.97, S 14.24.
Compound 29: Freshly distilled cyclohexa-1,3-diene (0.133 mL,
1.4 mmol) was added dropwise to a solution of compound 6[11a]
(214 mg, 1 mmol) in diethyl ether (30 mL). The solution was stirred
overnight, and after concentration compound 29 (223 mg, 76%)
was isolated as a yellow powder; m.p. 162 °C. 1H NMR (400 MHz,
CDCl3): δ = 1.39–1.42 (m, 2 H, CH2) 1.73–1.75 (m, 2 H, CH2),
3.14 (s, 2 H, CH), 3.27–3.29 (m, 2 H, CH–CO), 6.28 (dd, J = 3,
4.6 Hz, 2 H, =CH) ppm. 13C NMR (75 MHz, CDCl3): δ = 25.0,
211.2 ppm. IR (KBr): ν = 1752 (C=O), 1082 (C=S) cm–1. MS (EI):
˜
m/z (%) = 332 (70) [M]+·, 300 (100), 268 (73), 240 (13).
Compound 25: A solution of DDQ (350 mg, 1.54 mmol) in anhy-
drous tetrahydrofuran (5 mL) was added at –78 °C to a solution of
compound 24 (450 mg, 1.35 mmol) in anhydrous tetrahydrofuran
(10 mL). The reaction mixture was allowed to stand at room tem-
perature for 1 h. The solvent was evaporated under vacuum and
the residue was purified by flash chromatography on silica gel with
dichloromethane as eluent to afford compound 25 as orange crys-
tals (400 mg, 90%); m.p. 152 °C. 1H NMR (500 MHz, CDCl3): δ
= 3.93 (s, 6 H, CH3) ppm. 13C NMR (125 MHz, CDCl3): δ = 53.7,
36.3, 50.9, 134.0, 154.4, 189.1, 208.6 ppm. IR (KBr): ν = 1664
˜
(C=O), 1076 (C=S) cm–1. MS (EI): m/z (%) = 294 (74) [M]+, 266
(100).
Compound 30: Titanium(IV) chloride (0.57 mL, 5.16 mmol) was
added dropwise at 0 °C to a solution of compound 29 (190 mg,
0.64 mmol) in dichloromethane (30 mL). The mixture was stirred
for 5 min, followed by the successive addition of malononitrile
(255 mg, 3.87 mmol) in dichloromethane (10 mL) and pyridine
(0.83 mL, 32 mmol) in dichloromethane (10 mL) over 10 min. The
solution was kept at room temperature and stirred overnight. The
resulting dark red solution was poured into ice/water and extracted
with dichloromethane. The combined organic layers were washed
with water and brine and dried with sodium sulfate, and the sol-
vents were evaporated. The red residue was purified by chromatog-
raphy on silica gel with dichloromethane/hexane (2:1, v/v) as the
mixture of eluents to afford compound 30 (186 mg, 74%) as a red-
137.2, 146.7, 161.3, 172.7, 205.1 ppm. IR (KBr): ν = 1736 (C=O
˜
ester), 1673 (C=O), 1074 (C=S) cm–1. MS (EI): m/z (%) = 330 (100)
[M]+·, 299 (17), 271 (11).
Compound 26: Freshly distilled cyclopentadiene (0.25 mL, 3 mmol)
was added to a solution of compound 25 (200 mg, 61 mmol) in
anhydrous tetrahydrofuran (5 mL). The mixture was stirred for 1 h
at room temperature and the solvent was evaporated under vac-
uum. The residue was dissolved in dichloromethane (2 mL) and
methanol was added until precipitation of compound 26. After fil-
tration, compound 26 was isolated (227 mg, 95%) as orange crys-
tals; m.p. 204 °C (dec.). 1H NMR (500 MHz, CDCl3): δ = 1.77 (m,
1 H, 1 H from CH2 group), 2.58 (m, 1 H, 1 H from CH2 group),
3.73 (m, 8 H, CH3 and CH), 6.24 (s, 2 H, =CH) ppm. 13C NMR
(125 MHz, CDCl3): δ = 47.5, 52.5, 53.6, 69.5, 138.8, 152.5, 169.3,
1
brown powder. H NMR (300 MHz, CDCl3): δ = 1.47–1.49 (m, 2
H, CH2), 1.94–1.97 (m, 2 H, CH2), 2.95 (br. s, 2 H, CH), 3.70 (s,
2 H, CH–C=), 6.23 (dd, J = 3.2, 4.5 Hz, 2 H, =CH) ppm. IR (KBr):
ν = 2225 (CϵN), 1078 (C=S) cm–1. MS (EI): m/z (%) = 390 (32)
˜
[M]+, 337 (12), 310 (4). MS (MALDI, DCTB as matrix, negative
mode) calcd. for C19H10N4S3 390.006; found 390.01.
183.9, 207.4 ppm. IR (KBr): ν = 1739 (C=O ester), 1666 (C=O
˜
quinone), 1082 (C=S) cm–1. MS (EI): m/z (%) = 396 (78) [M]+·, 364
(36), 337 (25), 305 (62), 299 (61), 66 (100). C16H12O6S3 (395.98):
calcd. C 48.47, H 3.05, S 24.26; found C 48.26, H 3.11, S 24.66.
Compound 31: Titanium(IV) chloride (0.85 mL, 8 mmol) was added
dropwise at 0 °C to a solution of compound 29 (294 mg, 1 mmol)
in dichloromethane (100 mL). The reaction mixture was stirred for
15 min, followed by the successive addition of malononitrile
(66 mg, 1 mmol) in dichloromethane (15 mL) and pyridine
(1.28 mL, 16 mmol) in dichloromethane (15 mL) over 15 min. The
mixture was heated at reflux for 1 h. The resulting blue-black solu-
tion was poured into ice/water and extracted with dichloromethane.
The combined organic layers were washed with water and dried
with sodium sulfate, and the solvents were evaporated. The black
residue was purified by chromatography on silica gel with dichloro-
methane/hexane (2:1) as a mixture of eluents to afford compound
31 (235 mg, 69%) as an orange-brown powder. 1H NMR
Compounds 27 and 28: n-Butyllithium (0.31 mL, 0.55 mmol, 1.6 
in hexane) was added at –78 °C to a solution of malononitrile
(33.3 mg, 0.50 mmol) in anhydrous tetrahydrofuran (5 mL). After
the system had been stirred for 10 min at –78 °C, a solution of
compound 26 (100 mg, 0.25 mmol) in tetrahydrofuran (10 mL) was
added. The reaction mixture was allowed to stand at room tem-
perature. The solvent was evaporated under vacuum and the resi-
due was purified by chromatography on silica gel with dichloro-
methane as eluent, affording compound 28 as yellow crystals
(50 mg, 47%) in a first fraction, and compound 27 as yellow crys-
tals (30 mg, 31%) in a second fraction.
Compound 27: M.p. 198 °C. 1H NMR (500 MHz, CDCl3): δ = 1.65 (300 MHz, CDCl3): δ = 1.43–1.48 (m, 2 H, CH2), 1.74–1.82 (m, 1
(d, J = 9.5 Hz, 1 H, 1 H from CH2 group), 2.51 (d, J = 9.5 Hz, 1 H, 1 H from CH2 group), 1.93–2.01 (m, 1 H, 1 H from CH2 group),
H, 1 H from CH2 group), 3.58 (s, 2 H, CH–C–CO2Me), 3.64 (s, 3 2.94–2.96 (m, 1 H, CH), 3.08 (dd, J = 3.4, 8.3 Hz, 1 H, CH), 3.26–
Eur. J. Org. Chem. 2009, 6341–6354
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
6351

S.-X. Liu, P. Hudhomme et al.
FULL PAPER
3.28 (m, 1 H, CH–C=O), 3.76 [dd, J = 3.1, 9.9 Hz, 1 H, CH–
C=C(CN)2], 6.25 (td, J = J = 1.3 and 8.3 Hz, 1 H, =CH), 6.33 (td,
phosphonate 35c (777 mg, 2 mmol) in tetrahydrofuran (20 mL).
The solution was stirred for 15 min and a solution of compound
J = 1.3, 8.3 Hz, 1 H, =CH) ppm. IR (KBr): ν = 2224 (CϵN), 1676 34 (0.677 g, 1 mmol) in tetrahydrofuran (20 mL) was then added
˜
(C=O), 1078 (C=S) cm–1. MS (EI): m/z (%) = 342 (46) [M]+, 314 dropwise over 15 min. The solution was kept at room temperature
(82), 270 (19). MS (MALDI, DCTB as matrix, negative mode) and stirred overnight. After all solvents had been removed under
calcd. for C16H10N2OS3 341.995; found 341.99. Single crystals suit-
able for X-ray analysis were obtained by slow evaporation of a
dichloromethane/hexane (10:1) solution of compound 31.
vacuum, the crude oil was purified by chromatography on silica gel
with dichloromethane/hexane (1:3) as a mixture of eluents. Further
recrystallization from dichloromethane/petroleum ether afforded
compound 36c (763 mg, 83.7%) as a yellow powder; m.p. 148 °C.
1H NMR (300 MHz, CDCl3): δ = 1.02 (t, J = 7.0 Hz, 6 H, CH3),
1.06 (s, 18 H, tBu), 1.69 (sextet, J = 7.2 Hz, 4 H, CH2), 2.85 (t, J
= 7.0 Hz, 4 H, SCH2), 5.72 (s, 2 H, =CH), 7.31 (tt, J = 1.5, 7.4 Hz,
8 H, Hmeta), 7.35 (tt, J = 1.5 and 7.4 Hz, 4 H, Hpara), 7.60 (dt, J =
1.5, 6.5 Hz, 8 H, Hortho) ppm. MS (EI): m/z (%) = 910 (100) [M+].
MS (MALDI, DCTB as matrix, positive mode) calcd. for
C48H54O2S6Si2 910.198; found 910.204.
Compound 32: A mixture of compound 30 (50 mg, 0.13 mmol),
mercury(II) acetate (81 mg, 0.25 mmol) in dichloromethane
(40 mL) and glacial acetic acid (20 mL) was heated at reflux for
2 h and then filtered through sodium sulfate. The resulting orange
solution was extracted several times with dichloromethane. The
combined organic layers were washed with water and brine and
dried with sodium sulfate, and the solvents were evaporated. The
orange residue was chromatographed on silica gel with elution with
dichloromethane/hexane (3:1) to afford compound 32 (47 mg,
96%) as an orange powder. 1H NMR (500 MHz, CDCl3): δ = 1.48
(br. d, J = 8.4 Hz, 2 H, CH2), 1.96 (br. d, J = 8.4 Hz, 2 H, CH2),
2.94 (br. s, 2 H, CH), 3.71 (s, 2 H, CH–C=), 6.17 (dd, J = 3.1,
4.5 Hz, 2 H, =CH) ppm. MS (EI): m/z (%) = 374 (14) [M]+, 346
(8), 296 (13), 270 (9). Single crystals suitable for X-ray analysis were
obtained by slow evaporation of a dichloromethane/acetone (1:1)
solution of compound 32.
Compound 36d: A solution of n-butyllithium (1.25 mL, 2.17 mmol,
1.6  in hexane) was added dropwise at –78 °C to a solution of
phosphonate 35d[23] (596 mg, 1.97 mmol) in tetrahydrofuran
(20 mL). The solution was stirred for 15 min and a solution of 4,7-
bis(tert-butyldiphenylsilyloxy)-1,3-benzodithiole-2-one (34, 1.02 g,
1.51 mmol) in tetrahydrofuran was then added dropwise. The solu-
tion was kept at room temperature and stirred overnight. After
addition of methanol, the precipitate was filtered and washed with
methanol to afford compound 36d (1.13 g, 88%) as a yellow pow-
der; m.p. 206 °C (CH2Cl2/petroleum ether). 1H NMR (300 MHz,
CDCl3): δ = 1.05 (s, 18 H, tBu), 3.31 (s, 4 H, CH2), 5.73 (s, 2 H,
=CH), 7.31 (tt, J = 1.5, 7.4 Hz, 8 H, Hmeta), 7.37 (tt, J = 1.5,
7.4 Hz, 4 H, Hpara),7.60 (dt, J = 1.5, 6.6 Hz, 8 H, Hortho) ppm. 13C
NMR (300 MHz, CDCl3): δ = 19.4, 26.5, 30.3, 107.0, 114.1, 115.9,
116.6, 127.8, 128.0, 130.0, 132.2, 135.4, 143.6 ppm. MS (EI): m/z
= 852 [M]+·. C44H44O2S6Si2 (852.12): calcd. C 61.93, H 5.20; found
C 61.81, H 5.26.
Compound 33: A mixture of compound 31 (18 mg, 52.5 µmol), mer-
cury(II) acetate (33 mg, 105 µmol) in dichloromethane (10 mL) and
glacial acetic acid (5 mL) was heated at reflux for 2 h and then
filtered through sodium sulfate. The resulting orange solution was
extracted several times with dichloromethane. The combined or-
ganic layers were washed with water and brine and dried with so-
dium sulfate, and the solvents were evaporated. Compound 33 was
isolated as a yellow-orange powder in 96% yield after recrystalli-
zation from tetrahydrofuran/hexane (1:6). 1H NMR (300 MHz,
CDCl3): δ = 1.46–1.42 (br. m, 2 H, CH2), 1.76–1.81 (m, 1 H, 1 H
from CH2 group), 1.94–2.01 (m, 1 H, 1 H from CH2 group), 2.93–
2.95 (m, 1 H, CH), 3.09 (dd, J = 3.2, 8.3 Hz, 1 H, CH), 3.25–3.27
(m, 1 H, CH–C=O), 3.76 [dd, J = 3.2, 9.9 Hz, 1 H, CH–C=C-
(CN)2], 6.22 (td, J = 1.3, 8.3 Hz, 1 H, =CH), 6.28 (td, J = 1.3,
Compound 36e: A solution of n-butyllithium (1.6  in hexane,
0.73 mL, 1.15 mmol) was added dropwise at –78 °C to a solution
of phosphonate 35e (640 mg, 1.04 mmol) in tetrahydrofuran
(15 mL). The solution was stirred for 10 min and a solution of com-
pound 34 (800 mg, 1.04 mmol) in tetrahydrofuran (15 mL) was
then added dropwise. The solution was kept at room temperature
and stirred overnight. After all solvents had been removed under
vacuum, the crude oil was purified by chromatography on silica gel
with dichloromethane/petroleum ether (1:9) as a mixture of eluents
to afford compound 36e (300 mg, 22%) as yellow crystals; m.p.
179 °C. 1H NMR (500 MHz, CDCl3): δ = 0.89 (t, J = 6.8 Hz, 6 H,
CH3), 1.08 (s, 18 H, tBu), 1.20–1.50 (m, 36 H, CH2), 1.68 (q, J =
7.2 Hz, 4 H, CH2), 2.87 (t, J = 7.2 Hz, 4 H, CH2S), 5.75 (s, 2 H,
=CH), 7.34 (t, J = 7.2 Hz, 8 H, Hmeta), 7.39 (t, J = 7.2 Hz, 4 H,
Hpara), 7.62 (t, J = 7.2 Hz, 8 H, Hortho) ppm. 13C NMR (125 MHz,
CDCl3): δ = 14.1, 19.4, 22.7, 26.5, 29.1, 29.3, 29.4, 29.5, 29.6, 29.65,
29.7, 29.8, 31.9, 36.4, 109.3, 112.3, 115.8, 127.3, 127.8, 128.1, 129.9
132.2, 135.4, 143.6 ppm. C66H90O2S6Si2 (1162.48): calcd. C 68.10,
H 7.79; found C 68.36, H 7.87.
8.3 Hz, 1 H, =CH) ppm. IR (KBr): ν = 2223 (CϵN), 1716 (C=O),
˜
1658 (C=O) cm–1. MS (EI): m/z (%) = 326 (16) [M]+, 298 (18).
Compound 36b: A solution of n-butyllithium (2.7  in heptane,
0.7 mL, 1.8 mmol) was added dropwise at –78 °C to a solution of
phosphonate 35b (565 mg, 1.7 mmol) in tetrahydrofuran (15 mL).
The solution was stirred for 10 min and a solution of compound
34 (0.507 g, 0.75 mmol) in tetrahydrofuran (15 mL) was then added
dropwise over 15 min. The solution was kept at room temperature
and stirred for 3 h. After all solvents had been removed under vac-
uum, the crude oil was purified by chromatography on silica gel
with dichloromethane/hexane (1:3) as a mixture of eluents to afford
compound 36b (482 mg, 75%) as a yellow orange powder. 1H
NMR (400 MHz, CDCl3): δ = 1.06 (s, 18 H, tBu), 2.47 (s, 6 H,
SCH3), 5.73 (s, 2 H, =CH), 7.30 (tt, J = 1.5, 7.5 Hz, 8 H, Hpara),
7.38 (tt, J = 1.5, 7.5 Hz, 4 H, Hmeta),7.60 (dt, J = 1.5, 6.5 Hz, 8 H,
Hortho) ppm. 13C NMR (100 MHz, CDCl3): δ = 19.8, 26.9, 30.7,
116.3, 128.2, 130.4, 132.5, 135.8, 144.4 (some carbon signals are
missing due to the insolubility of 36b) ppm. MS (EI): m/z (%) =
854 (100) [M]+. MS (MALDI, dithranol as matrix, positive mode)
calcd. for C44H46O2S6Si2 854.136; found 854.135. C44H46O2S6Si2
(855.38): calcd. C 61.81, H 5.42; found C 62.31, H 5.58. Single
crystals suitable for X-ray analysis were obtained by slow evapora-
tion of a tetrahydrofuran/petroleum ether (1:7) solution of 36b.
Compound 36f: A solution of n-butyllithium (1.6  in hexane,
2.6 mL, 4.2 mmol) was added dropwise at –78 °C to a solution of
phosphonate 35f (1 g, 3.82 mmol) in tetrahydrofuran (15 mL). The
solution was stirred for 10 min and a solution of compound 34
(1.29 g, 1.91 mmol) in tetrahydrofuran (15 mL) was then added
dropwise. The solution was kept at room temperature and stirred
overnight. After all solvents had been removed under vacuum, the
residue was dissolved in dichloromethane. The organic layer was
washed with water and dried with magnesium sulfate, and the sol-
vents were evaporated. Crystallization with dichloromethane/petro-
Compound 36c: A solution of n-butyllithium (2.7  in heptane,
0.77 mL, 2.1 mmol) was added dropwise at –78 °C to a solution of
6352
www.eurjoc.org
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2009, 6341–6354

Fused Tetrathiafulvalene/Tetracyanoquinodimethane Systems
leum ether afforded compound 36f (1.3 g, 84%) as yellow crystals; PNANO) program entitled TTF-based Nanomat. This work was
m.p. 171 °C. 1H NMR (500 MHz, CDCl3): δ = 1.06 (s, 18 H, tBu), also supported by grants from the Ministère de l’Enseignement Su-
5.97 (s, 2 H, =CH), 7.30–7.48 (m, 16 H), 7.63–7.68 (m, 8 H) ppm.
C46H44O2S4Si2 (812.18): calcd. C 67.93, H 5.45; found C 67.66, H
5.69.
périeur de la Recherche et de la Technologie (MENRT) for Nicolas
Gautier, the “Ville d’Angers” for Frédéric Dumur, as well as by the
Swiss National Science Foundation for Xavier Guégano.
X-ray Crystallographic Study: Diffraction data for single crystals
of 32 and 15b were collected with a Stoe Mark II Imaging Plate
Diffractometer System (Stoe & Cie, 2002) fitted with a two-circle
goniometer and a graphite-monochromator and with a Stoe Im-
aging Plate Diffractometer System fitted with a one-circle goniome-
ter and a graphite-monochromator, respectively, at –100 °C with
use of Mo-Kα X-radiation (λ = 0.71073 Å). Crystal data for 32:
C19H10N4OS2, Mr = 374.03, T = 173(2) K, crystal dimensions
0.450ϫ0.383ϫ0.300 mm, orthorhombic, cmc21, a = 15.8506(11) Å,
b = 14.7266(8) Å, c = 7.3784(4) Å, α = β = γ = 90°, V =
1722.31(18) Å3, Z = 4, ρcalcd. = 1.444 gcm–3, F(000) = 768, µ =
0.325 mm–1, 2θmax = 29.26°, 16279 measured reflections, 2394 inde-
pendent reflections (Rint = 0.0421), 2174 strong reflections [I0 Ͼ 2σ
(I0)], 121 refined parameters, R1 = 0.0284 (strong data) and 0.0320
(all data), wR2 = 0.0780 (strong data) and 0.0792 (all data), GOF
= 1.053, 0.237 and –0.275 eÅ–3 max. and min. residual electron
density. A semiempirical absorption correction was applied with
the aid of MULABS (PLATON,[24] Tmin = 0.775, Tmax = 0.903).
The structure was solved by direct methods with the aid of the
SHELXS-97[25] program and refined by full-matrix least-squares
on F2 with SHELXL-97.[26] All hydrogen atoms were placed on
calculated positions derived from ideal geometries. All non-hydro-
gen atoms were refined anisotropically. The highest remaining elec-
tron density of 0.24 electrons/Å3 is located next to atom C10. The
molecule lies on a crystallographic mirror plane. The carbon atoms
C3, C4 and C5 of the bicyclooctene moiety show strongly aniso-
tropical adps.
[1] a) J. Ferraris, D. O. Cowan, V. Walatka Jr., J. H. Perlstein, J.
Am. Chem. Soc. 1973, 95, 948–949; b) L. B. Coleman, M. J.
Cohen, D. J. Sandman, F. G. Yamagishi, A. F. Garito, A. J.
Heeger, Solid State Commun. 1973, 12, 1125–1132.
[2] a) J. L. Segura, N. Martín, Angew. Chem. Int. Ed. 2001, 40,
1372–1409; Angew. Chem. 2001, 113, 1416–1455; b) J. Yamada,
T. Sugimoto (Eds.), TTF Chemistry. Fundamentals and applica-
tions of tetrathiafulvalene, Springer, 2004; c) D. Canevet, M.
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McInnes, J. P. Zhao, Angew. Chem. Int. Ed. 2003, 42, 4636–
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Crystal Data for 15b: C17H14O2S6, Mr = 442.64, T = 173(2) K,
crystal dimensions 0.45ϫ0.30ϫ0.20 mm, monoclinic, C2/c, a =
25.743(2) Å, b = 6.5857(4) Å, c = 22.842(2) Å, β = 108.529(9)°, V
= 3671.8(5) Å3, Z = 8, ρcalcd. = 1.601 gcm–3, F(000) = 1824, µ =
0.754 mm–1, 2θmax = 26.06°, 14044 measured reflections, 3604 inde-
pendent reflections (Rint = 0.0408), 2618 strong reflections [I0Ͼ 2σ
(I0)], 228 refined parameters, R1 = 0.0278 (strong data) and 0.0439
(all data), wR2 = 0.0623 (strong data) and 0.0655 (all data), GOF
= 0.891, 0.255 and –0.345 e/Å3 max. and min. residual electron
density. The structure was solved by direct methods with the aid of
the SHELXS-97[25] program and refined by full-matrix least-
squares on F2 with SHELXL-97.[26] The hydrogen atoms were in-
cluded in calculated positions and treated as riding atoms by use
of the SHELXL-97 default parameters. No absorption correction
was applied.
[10] M. A. Herranz, S. González, I. Pérez, N. Martín, Tetrahedron
2001, 57, 725–731.
[11] a) N. Gautier, N. Gallego-Planas, N. Mercier, E. Levillain, P.
Hudhomme, Org. Lett. 2002, 4, 961–963; b) N. Gautier, F. Du-
mur, V. Lloveras, J. Vidal-Gancedo, J. Veciana, C. Rovira, P.
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gew. Chem. 2003, 115, 2871–2874; c) F. Dumur, N. Gautier, N.
Gallego-Planas, Y. Sahin, E. Levillain, N. Mercier, P. Hud-
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CCDC-735636 (for 15b), -735637 (for 31), -735638 (for 32) and
-735639 (for 36b) contain the supplementary crystallographic data
for this paper. These data can be obtained free of charge from The
Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/
data_request/cif.
Supporting Information (see also the footnote on the first page of
this article): MS and NMR spectra of ketene imine 18, cyclic vol-
tammograms of compounds 6, 15b, 29 and 30, UV/Vis spectra of
7a and 15a and single-crystal structures of compounds 31 and 36b.
Acknowledgments
This work was supported by the French National Research Agency
in the framework of the Nanosciences and Nanotechnology (ANR
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Received: August 28, 2009
Published Online: November 11, 2009
6354
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Eur. J. Org. Chem. 2009, 6341–6354