New strategies and building blocks for functionalised 9,10-bis(1,3-dithiol-2-ylidene)-9,10-dihydroanthracene derivatives, including pyrrolo-annelated derivatives and pi-extended systems with intramolecular charge-transfer.

Article abstract of DOI:10.1039/b211153p

A range of new functionalised 9,10-bis(1,3-dithiol-2-ylidene)-9,10-dihydroanthracene (TTFAQ) derivatives have been synthesised from the key di(halomethyl) building blocks, 10-[4,5-bis(bromomethyl)-1,3-dithiol-2-ylidene]-anthracene-9(10H)-one 10, 10-[4,5-bis(chloromethyl)-1,3-dithiol-2-ylidene]anthracene-9(10H)-one 11 and 9-[4,5-bis(chloromethyl)-1,3-dithiol-2-ylidene]-10-[4,5-bis(hexylsulfanyl)- 1,3-dithiol-2-ylidene]-9,10-dihydroanthracene 18. A Diels-Alder strategy comprising trapping of the transient exocyclic diene 19, which is derived from 18, with 1,4-naphthoquinone leads to the aromatised TTFAQ anthraquinone system 21. Horner-Wadsworth-Emmons olefination of 21 with the anion generated from reagent 22 gave the fused bis(TTFAQ) structure 23. Pyrrolo-annelated derivatives 30-34 have been obtained in a sequence of reactions from compound 10. Mono-formylation of the pyrrole ring of 32 and 33 under Vilsmeier conditions gave 35 and 36 which upon reaction with 2,4,5,7-tetranitrofluorene gave the donor-pi-acceptor diads 38 and 39. Cyclic voltammetry (CV) in solution for all the TTFAQ derivatives shows the typical quasi-reversible two-electron oxidation wave of the TTFAQ core at potentials which vary slightly depending on the substituents. For example, the value of Eox is raised by the electron withdrawing anthraquinone and tetranitrofluorene units of 21 and 38, respectively. The CV of the conjugated TTFAQ dimer 23 showed two, two-electron oxidation waves corresponding to the sequential formation of 23(2+) and 23(4+) (delta Eox = 130 mV) providing evidence for a significant intramolecular electronic interaction, i.e. the dication 23(2+) acts as a conjugated donor-pi-acceptor diad, thereby raising the oxidation potential of its partner TTFAQ unit. Spectroelectrochemical studies on 23 support this explanation. A strong intramolecular charge transfer band at lambda max 538 nm is seen in the UV-Vis spectra of the TTFAQ-pi-tetranitrofluorene diads 38 and 39. The X-ray crystal structures are reported for compounds 30, 33 and 34. The pyrrolo-TTFAQ moiety adopts a saddle-shape with the central ring of the dihydroanthracene moiety folded along the C(9) ... C(10) vector in each case. Significant intermolecular interactions are observed in the structures.

Full text of DOI:10.1039/b211153p

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New strategies and building blocks for functionalised 9,10-bis(1,3-
dithiol-2-ylidene)-9,10-dihydroanthracene derivatives, including
pyrrolo-annelated derivatives and ꢀ-extended systems with
intramolecular charge-transfer†‡
Christian A. Christensen,a Martin R. Bryce,*a Andrei S. Batsanova and Jan Becherb
a Department of Chemistry, University of Durham, Durham, UK DH1 3LE.
E-mail: m.r.bryce@durham.ac.uk
b Department of Chemistry, Odense University, Campusvej 55, DK 5230 Odense M, Denmark
Received 12th November 2002, Accepted 12th December 2002
First published as an Advance Article on the web 24th January 2003
A range of new functionalised 9,10-bis(1,3-dithiol-2-ylidene)-9,10-dihydroanthracene (TTFAQ) derivatives have
been synthesised from the key di(halomethyl) building blocks, 10-[4,5-bis(bromomethyl)-1,3-dithiol-2-ylidene]-
anthracene-9(10H)-one 10, 10-[4,5-bis(chloromethyl)-1,3-dithiol-2-ylidene]anthracene-9(10H)-one 11 and
9-[4,5-bis(chloromethyl)-1,3-dithiol-2-ylidene]-10-[4,5-bis(hexylsulfanyl)-1,3-dithiol-2-ylidene]-9,10-dihydro-
anthracene 18. A Diels–Alder strategy comprising trapping of the transient exocyclic diene 19, which is derived
from 18, with 1,4-naphthoquinone leads to the aromatised TTFAQ anthraquinone system 21. Horner–Wadsworth–
Emmons olefination of 21 with the anion generated from reagent 22 gave the fused bis(TTFAQ) structure 23.
Pyrrolo-annelated derivatives 30–34 have been obtained in a sequence of reactions from compound 10. Mono-
formylation of the pyrrole ring of 32 and 33 under Vilsmeier conditions gave 35 and 36 which upon reaction with
2,4,5,7-tetranitrofluorene gave the donor–π-acceptor diads 38 and 39. Cyclic voltammetry (CV) in solution for
all the TTFAQ derivatives shows the typical quasi-reversible two-electron oxidation wave of the TTFAQ core at
potentials which vary slightly depending on the substituents. For example, the value of E ox is raised by the electron
withdrawing anthraquinone and tetranitrofluorene units of 21 and 38, respectively. The CV of the conjugated
TTFAQ dimer 23 showed two, two-electron oxidation waves corresponding to the sequential formation of 232ϩ
and 234ϩ (∆E ox = 130 mV) providing evidence for a significant intramolecular electronic interaction, i.e. the
dication 232ϩ acts as a conjugated donor–π-acceptor diad, thereby raising the oxidation potential of its partner
TTFAQ unit. Spectroelectrochemical studies on 23 support this explanation. A strong intramolecular charge
transfer band at λmax 538 nm is seen in the UV-Vis spectra of the TTFAQ–π-tetranitrofluorene diads 38 and 39.
The X-ray crystal structures are reported for compounds 30, 33 and 34. The pyrrolo–TTFAQ moiety adopts
a saddle-shape with the central ring of the dihydroanthracene moiety folded along the C(9). . .C(10) vector
in each case. Significant intermolecular interactions are observed in the structures.
between the sulfur atoms and the hydrogen atoms at the peri
Introduction
sites.2b Calculated energies predict that the HOMO in 2 lies
slightly below that of TTF 1, and these data support the
experimental evidence that the two, one-electron oxidations of
2 coalesce under the same oxidation wave.2b The cation radical
of system 2 is a transient species which has been generated
by flash photolysis3c and pulse radiolysis experiments.4 This
fascinating interplay of redox and conformational properties
has led to derivatives of 2 being employed as building blocks
for charge-transfer salts,3a,5 nonlinear optical materials,6
multi-stage redox assemblies,7 cyclophanes,8 dendrimers9 and
compounds for photosynthetic models.4a,7c,10
The anthraquinone-derived “extended TTF” (TTF = tetra-
thiafulvalene 1) π-electron donor unit 9,10-bis(1,3-dithiol-
2-ylidene)-9,10-dihydroanthracene 21 (herein abbreviated to
TTFAQ) offers a unique combination of redox and structural
properties which are very different from those of TTF. Solution
electrochemical studies2 have established that whereas TTF 1
undergoes two, reversible, one-electron oxidation waves, system
2 undergoes a single, two-electron oxidation process to yield
a thermodynamically stable dication [E ox ϩ0.30 Ϫ ϩ0.40 V
(vs Ag/AgCl in MeCN) depending upon the substituents
present]. This redox process, which is electrochemically
quasi-reversible and chemically reversible, is accompanied by
a dramatic conformational change,3 as shown by X-ray crystal-
Derivatives of 2 have generally been prepared by two-fold
Horner–Wadsworth–Emmons olefination of the appropriate
anthraquinone starting material with 1,3-dithiole-phosphonate
reagents,11 or by stepwise reactions on anthrone.11b,12 Lithiation
of the dithiole ring(s) of 2 (or, more efficiently the di- or tri-
methyl derivatives)13 followed by trapping with electrophiles
provides a means of attaching other substituents, e.g. -CO2Me,
-C(S)NHMe and -SC(O)Ph.
Herein we report new functionalised TTFAQ derivatives
obtained from key di(halomethyl) building blocks 10, 11 and
18, including a Diels–Alder strategy using the transient exo-
cyclic diene 19.14 Most notably the π-extended systems 21
and 23, and pyrrolo-annelated derivatives 30–36 and 38–39
have been obtained. Solution electrochemical studies and X-ray
crystallographic data are also reported.
lographic studies on 3,3a 32ϩ 3a 3b and 42ϩ 3c The neutral mole-
, 4 .
cules are saddle-shaped comprising a concave cavity and a
folded anthracenediylidene unit, whereas in the dications the
anthracene ring system becomes planar and aromatic, with
bond lengths similar to anthracene itself, and the hetero-
aromatic 1,3-dithiolium cations are almost orthogonal to this
plane. These structures are supported by theoretical studies on
2 which show that the saddle shape arises from steric hindrance
† This paper is Molecular Saddles Part 10. For Part 9 see reference 5c.
‡ Electronic supplementary information (ESI) available: NOE spectra
for compound 23. See http://www.rsc.org/suppdata/ob/b2/b211153p/
T h i s j o u r n a l i s © T h e R o y a l S o c i e t y o f C h e m i s t r y 2 0 0 3
O r g . B i o m o l . C h e m . , 2 0 0 3 , 1, 5 1 1 – 5 2 2
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Scheme 1 Reagents and conditions: i, MeOTf, CH2Cl2, 20 ЊC; ii, pyridine–AcOH; iii, Bu4NF, THF, 20 ЊC, iv, PBr3, DMF, 0 ЊC to 20 ЊC; v, SOCl2,
DMF, 0 ЊC to 20 ЊC; vi DMAD, KI, 18-crown-6, PhMe, 100 ЊC; vii, DDQ, PhMe, 100 ЊC.
dicyanobenzoquinone (DDQ) and further heating (Scheme 1).
These experiments established that the transient diene 12 could
be efficiently generated and trapped in situ.
Results and discussion
Generation and trapping of exocyclic dienes 12 and 19
Reactions of the anion of anthrone with 1,3-dithiolium cations
are known to proceed readily to yield 10-(1,3-dithiol-2-ylide-
ne)anthracene-9(10H )-one derivatives15 which can function as
precursors to unsymmetrical TTFAQ systems.11b,12 Following
this strategy, the bis-DPTBS protected diol 516 was methylated
using methyl triflate to give the unstable salt 6 which was
sufficiently pure (1H NMR evidence) for immediate reaction
with anthrone 7 in the presence of pyridine and acetic acid to
yield product 8 in 91% overall yield from thione 5 (Scheme 1).
As a model for subsequent TTFAQ systems we initially
explored the conversion of 8 into the exocyclic diene 12. Other
reports have addressed related reactions of TTF17 and 1,3-
dithiole-2-one derivatives.11c Deprotection of compound 8 with
tetrabutylammonium fluoride gave the di(hydroxymethyl)
derivative 9 (84% yield) which was brominated using PBr3 in
DMF to give the di(bromomethyl) derivative 10 (89% yield).
Similarly di(chloromethyl) derivative 11 was obtained using
SOCl2 in DMF (83% yield). Both compounds 10 and 11 are
shelf-stable yellow solids.
Derivative 11 was tested as a diene precursor using the con-
ditions of Müllen et al17d and Gorgues et al.17c with dimethyl
acetylenedicarboxylate (DMAD) as the dienophile for in situ
trapping. A mixture of 11, potassium iodide, 18-crown-6 and
DMAD was heated in dry toluene at 100 ЊC until all compound
11 was consumed and two new products were obtained (TLC
evidence): these were presumably the adduct 13 and the derived
aromatised product 14. Separation of these was not attempted;
instead the mixture was converted cleanly into 14 as the sole
product (61% yield from 11) by addition of 2,3-dichloro-5,6-
We next turned to the analogous diene 19 (Scheme 2) with the
hexylsulfanyl substituents chosen to enhance the solubility of
the derived TTFAQ systems. Horner–Wadsworth–Emmons
olefination of 8 with the anion generated from reagent 1518
(LDA at –78 ЊC) gave compound 16 (77% yield) which upon
deprotection gave the diol 17 (88% yield). Conversion of 17 into
di(chloromethyl) derivative 18 was achieved using either SOCl2
in CCl4 (10% yield) or, more efficiently, by reaction with PPh3 in
a mixture of CCl4 and MeCN19 (optimised 66% yield). (No
reaction occurred in neat CCl4). Formation of aldehyde 24 in
this transformation has been discussed previously:14 its form-
ation was suppressed when as high a concentration of reactants
as possible was used. By analogy with the generation of 12
described above, diene 19 was generated in situ and trapped
with 1,4-naphthoquinone 20 followed by aromatisation with
DDQ to yield the black crystalline product 21 (63% yield) com-
prising a rigid donor–π-acceptor system. Reaction of 21 with
the anion generated from reagent 2218 gave the fused bis-
(TTFAQ) structure 23 as a yellow powder in 88% yield. To
ensure reaction of both carbonyl groups of 21, an excess of 22
(10 equivalents) was used, as noted by Gorgues et al for similar
reactions.20 The solubility of 23 in organic solvents was con-
siderably greater than that of its precursor 21. Concurrent with
our initial report on the synthesis of 21,14 Herranz and Martín
described the generation of an analogue of 19 (possessing SMe
substituents instead of SC6H13) from the corresponding
di(bromomethyl) precursor and its trapping with C60 (25%
yield).21
Previous studies have shown that the TTFAQ unit flips in
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Scheme 2 Reagents and conditions: i, LDA, THF, Ϫ78 ЊC to 20 ЊC; ii, Bu4NF, THF, 20 ЊC; iii, PPh3, CCl4, MeCN, 80 ЊC; iv, KI, 18-crown-6, PhMe,
90 ЊC; v, DDQ, PhMe, 90 ЊC; vi, LDA, THF, Ϫ78 ЊC to 20 ЊC.
solution between two different saddle conformations.13c The 1H
NMR spectrum of 23 (Fig. 1a) is, therefore, complicated by the
fact that the two TTFAQ units are joined in a rigid and locked
fashion. They have no possibility to rotate relative to each
other, hence the molecule can adopt two different conform-
ations, one where each TTFAQ moiety is flipped up [(up, up) =
(down, down)] and another where one moiety is up and the
other is down [(up, down) = (down, up)] which explains the two
pairs of singlets observed for the two non-equivalent SMe
groups. The larger pair integrated to ca. four protons for each
singlet, whereas the smaller pair integrated to two protons for
each singlet, consistent with twelve protons for the four SMe
groups. Also the aromatic multiplets at 7.80 and 7.72 ppm
integrated to ca. 0.6 and 1.4 protons, respectively, and two
triplets were seen for the terminal Me groups of the hexyl-
sulfanyl chains, which also integrated in a ca. 1 : 2 ratio. This
suggests that 23 is approximately twice as long in one conform-
ation as in the other. Oxidation of 23 to its tetracation 234ϩ was
achieved with iodine in CDCl3 to afford a red precipitate, the 1H
NMR spectrum of which in (CD3)2SO is shown in Fig. 1b. This
spectrum is simplified compared to that of neutral 23 because
234ϩ consists of planar moieties free to rotate with respect to
each other, and hence due to the symmetry of the tetracation
only one SMe singlet is seen, integrating to 12H. Also, the
multiplets and the singlet in the aromatic region of the
spectrum now all have integrals divisible by two, and the two
triplets arising from the terminal methyl groups of the hexyl-
sulfanyl chains have collapsed into one triplet integrating to 6H.
An NOE experiment further proved the existence of two con-
formers of 23. (See the Electronic supplementary information).
Pyrrolo-annelated TTFAQ derivatives
By analogy with pyrrolo–TTF syntheses,22 we recognised that
di(bromomethyl) derivative 10 could serve as a precursor to
pyrrolo-annelated TTFAQ derivatives. An extension of the
π-system of TTFAQ in this way would be novel and could
provide interesting solid state structures. Furthermore, the
pyrrole unit should give new reactive sites for the attachment of
functional groups. Accordingly, the dihydropyrrolo derivative
26 was prepared in 82% yield by reaction between 10 and two
equivalents of sodium tosylamide 25 (1 equiv. of 25 reacts with
the HBr which is formed) (Scheme 3). Oxidation of 26 to the
pyrrolo derivative 27 was achieved using DDQ in refluxing
chlorobenzene (92% yield). Reaction of 27 with reagents 22 and
29 (as described above for the synthesis of 16) cleanly afforded
TTFAQ derivatives 30 and 31, respectively, in 86–91% yields.
Detosylation of 30 and 31 using sodium methoxide gave
compounds 32 and 33 as yellow solids in high yields: they have
good solubility in a range of organic solvents and can be
synthesised on a multi-gram scale.
The potential for N-functionalisation of the pyrrolo–TTFAQ
system was demonstrated in the clean conversion of 33 into
34 (97% yield) upon deprotonation with sodium hydride in
DMF, followed by reaction with iodomethane. High-yielding
mono-formylation of 32 and 33 was achieved by analogy with
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Scheme 3 Reagents and conditions: i, MeCN–DMF, 80 ЊC; ii, DDQ, PhCl, reflux; iii, LDA, THF, Ϫ78 ЊC to 20 ЊC; iv, NaOMe, MeOH, THF, reflux;
v, NaH, DMF, 20 ЊC, then MeI, DMF, 20 ЊC; vi, POCl3, DMF, 20 ЊC; vii, DMF, 20 ЊC.
pyrrolo–TTF,23 upon reaction with phosphorus oxychloride
and DMF under standard Vilsmeier conditions to give 35 and
36, respectively. To demonstrate that the aldehyde group of 35
and 36 can serve as a reactive ‘handle’ for further functionalis-
ation, a condensation reaction with 2,4,5,7-tetranitrofluorene
3724 in DMF gave the π-extended donor–acceptor diad
molecules 38 and 39 as black powders in 80 and 87% yields,
respectively. The butylsulfanyl chains of the latter greatly
increased the solubility in organic solvents, compared to its
reduction wave of the anthraquinone moiety was also observed.
An increase in the oxidation potential when electron withdraw-
ing groups are attached has precedent in TTFAQ–C60 diads
studied by Martín and Herranz,21 and rigid TTF–quinone
triads studied by Frenzel and Müllen.25 The relatively high
oxidation potential of compound 16 is harder to explain; it is
raised by 90 mV compared to compound 17 and ∆E (defined as
E ox Ϫ E oxpc) is the highest (310 mV) in this series. This is
pa
possibly due to steric effects of the bulky DPTBS groups.
The CV of the conjugated TTFAQ dimer 23 showed two,
well-resolved, two-electron oxidation waves (∆E ox = 130 mV)
(Fig. 2). The difference in oxidation potentials for the two
TTFAQ moieties in 23 cannot be explained by their different
substituents, rather it is more likely to be due to a significant
intramolecular electronic interaction, as seen for other TTFAQ–
donor diads (donor = TTF or ferrocene) with conjugative
links.2c,d Whichever TTFAQ unit in 23 is oxidised first will
become a good electron acceptor, and thus the dication 232ϩ
acts as a conjugated donor–π–acceptor diad,26 thereby raising
the oxidation potential of the second (neutral) TTFAQ unit in
the molecule.
1
methylsulfanyl analogue 38. The H NMR spectra of both 38
and 39 displayed two sets of broad peaks as a result of the
ability of the molecules to adopt two different conformations,
as described for compound 23 above.
Solution electrochemical and UV-Vis spectroscopic properties
Solution electrochemical properties of the TTFAQ derivatives
were studied by cyclic voltammetry (CV) and the data are
collated in Table 1. All the derivatives show the typical
quasi-reversible two-electron oxidation wave of the TTFAQ
core2 at potentials which vary slightly depending on the sub-
stituents which are attached to the dithiole rings. For example,
the value of E ox is raised (i.e. the TTFAQ dication is destabil-
ised) by the electron withdrawing chloromethyl groups in 18,
and, more notably by the anthraquinone unit of donor–
acceptor diad 21; for this compound a reversible one-electron
Spectroelectrochemical studies were performed on com-
pound 23 (Fig. 3). Upon oxidation to the dication 232ϩ the
UV-Vis spectrum resembles the sum of the spectra for neutral
4 and 42ϩ. However, the broad band at λmax 540 nm extends to
840 nm, whereas for 42ϩ there is no absorption beyond 600
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Table 1 Cyclic voltammetric dataa
Compound
E oxpa /V
E oxpc /V
E redpc /V
E redpa /V
16
17
18
21
23
30
31
32
33
34
35
36
38
39
0.54
0.45
0.58
0.71
0.23
0.32
0.48
0.61
—
—
—
—
—
—
Ϫ0.85 (1e)
—
—
—
—
—
—
—
Ϫ0.79 (1e)
0.54 (E1), 0.67 (E2)
0.45 (E1), 0.62 (E2)
—
—
—
—
—
—
—
—
—
—
0.63
0.66
0.50
0.49
0.50
0.55
0.58
0.63
0.64
0.45
0.46
0.35
0.34
0.32
0.48
0.47
0.42
0.45
—
Ϫ0.41 (1e)b
Ϫ0.41 (1e)b
a Data recorded vs. Ag/AgCl; compound ca. 1 × 10Ϫ3 M, electrolyte 0.1 M Bu4NPF6 in CH2Cl2, 20 ЊC, scan rate 100 mV sϪ1. All waves are two-
electron processes, unless otherwise designated. b Irreversible.
Fig. 2 Cyclic voltammogram of compound 23 under the conditions
stated in Table 1.
different from the yellow TTFAQ precursors 35 and 36. The
UV-Vis absorption spectra of 38 and 39 were almost identical
(see Fig. 4 for 39). In addition to the two bands typical of
TTFAQ derivatives (λmax 357 and 428 nm) a lower energy band
was present at λmax 538 nm. The intensity of this band, relative
to the two higher energy bands, was independent of con-
centration, and is thus assigned to an intramolecular CT band.
Similar ICT bands have been observed for other conjugatively
linked donor–π-tetranitrofluorene molecules.24b,27
X-Ray crystal structures of compounds 30, 33 and 34
Fig. 1 IH NMR spectra of (a) 23 in CDCl3; (b) 234ϩ in (CD3)2SO.
The molecular structures and conformations of 33 and 34 are
similar (Fig. 5). The TTFAQ core of the molecule adopts the
nm.3c This could indicate the presence of a charge-transfer (CT)
band in 232ϩ overlaid with the characteristic TTFAQ2ϩ absorp-
tion (λmax 500 nm). The CT band at λmax 650 nm is clearly
seen to collapse upon further oxidation by which the donor–
π-acceptor system 232ϩ is destroyed. Since no intermolecular
usual saddle-shape,3a,3b,5b,13c with the central ring of the di-
hydroanthracene moiety folded along the C(9). . .C(10) vector by
39.5Њ and 38.1Њ, respectively, while the inclination between the
two benzene rings is slightly larger (50.6Њ and 43.6Њ, respect-
ively). The pyrrole ring and the adjacent S(1) and S(2) atoms are
co-planar within experimental error, and since both dithiole
rings are folded inward along the S(1). . .S(2) and S(3). . .S(4)
vectors, respectively, (by 14.8Њ and 14.7Њ in 33 and by 14.1Њ and
11.9Њ in 34) the S(3)C(21)C(22)S(4) plane forms a slightly acute
angle (82.0Њ in 33 and 84.5Њ in 34) with the pyrrole ring system.
In both structures the n-butyl chain at the S(5) atom is dis-
ordered between two conformations in a 10 : 1 (33) or 2 : 1 (34)
ratio. The major component and the other (ordered) n-butyl
chain adopt the planar all-trans conformations and lie prac-
tically parallel to the pyrrole ring. Two molecules, related via
CT band was seen upon oxidation of 4 to 42ϩ 3c
, we assign the
CT band of 232ϩ as being intramolecular as a result of con-
jugative interaction between the two redox active moieties. For
the oxidation of both 23 and 232ϩ isosbestic points indicate the
clean formation of 232ϩ and 234ϩ, respectively. The spectra of
both 232ϩ and 23 could be fully recovered upon sequential
reduction of 234ϩ showing that the λmax 650 nm band is not due
to decomposition products.
The donor–π-acceptor diads 38 and 39 are black powders,
with an intensely dark red appearance in solution, clearly
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Fig. 4 UV-VIS absorption spectrum of compound 39 in CH2Cl2.
Fig. 3 UV-VIS-NIR Spectroelectrochemistry of compound 23 in
CH2Cl2. (a) Oxidation to form 232ϩ; (b) oxidation to form 234ϩ. (Note
the collapse of the CT band at 650 nm).
an inversion centre, form a typical pseudo-dimer3a,3b,5b,13c,14 in
which n-butyl chains of one molecule are engulfed between the
pyrrole ring and n-butyl chains of the other, their separations
corresponding to normal van der Waals distances.28 The
shortest intradimer contacts are S(6). . .NЈ of 3.43 Å in 33 and
3.54 Å in 34, and it is noteworthy that the NH group in 33
forms no hydrogen bond.
Packing of the dimers in 33 and 34 is different. In the triclinic
structure 33, all the dimers have the same orientation and form
a succession of layers (Fig. 6a). Within a layer, each dimer inter-
acts with four others through two face-to-face contacts between
dithiole rings and two face-to-face contacts between dithiole–
pyrrole systems; the shortest contact distances S. . .S 3.63–3.73 Å
and S. . .C 3.54–3.61 Å are close to the sums of the van der
Waals radii (S, 1.81 Å; C, 1.77 Å).28 In the monoclinic structure
34, the dimers are arranged in rows, parallel to the x axis,
but dimers in adjacent layers have non-parallel (herringbone)
orientations (Fig. 6b). Thus face-to-face contacts of dithiole
rings exist only within the row; the shortest distances therein
(S. . .S 3.73 and S. . .C 3.69–3.72 Å) are comparable to those in 33.
The molecular geometry of 33 and 34 can be compared with six
Fig. 5 X-Ray molecular structures of (a) compound 33 and (b)
compound 34 showing thermal ellipsoids at the 50% probablity level.
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Fig. 6 Crystal packing of (a) compound 33 and (b) compound 34.
structurally characterised pyrrolo-annelated TTF derivatives29
(all with N-alkyl substituents) which have both the pyrrole ring
and the N atom bonding essentially planar. Even when the
molecule is sterically strained, as in some N,N-cyclophane
derivatives, the bis(pyrrolo–TTF) system folds only along the
S. . .S vectors of the dithiole rings. Structures of such TTF
systems with an SO2Ph substituent at the N atom are unknown,
but 30 can be compared with N-(benzenesulfonyl)pyrrole and a
number of its derivatives30 some of which display small but
significant non-planarity of the N atom with the sum of bond
angles being 350–356Њ.
The asymmetric unit of 30 comprises two molecules (A and
B) of broadly similar, but not identical, conformation (Fig. 7).
The dihydroanthracene moiety is folded along the C(9). . .C(10)
vector by 39.0Њ (A) and 40.0Њ (B) into two practically planar
moieties, and both dithiole rings are folded inwards. In mole-
cule A the folding along the S(1). . .S(2) and S(3). . .S(4) equals
11.6Њ and 15.2Њ; the corresponding angles in B are 17.4Њ and
7.3Њ. Thus, the angle between the S(1)C(16)C(17)S(2) and
S(3)C(21)C(22)S(4) planes is reduced to 76.0Њ in both
independent molecules. Whilst in 33 and 34 the pyrrole ring
with immediately adjacent atoms comprise a planar system, in
30 (molecule A) the ring is folded along the C(18). . .C(19) vector
by 2.7Њ and the N–S bond tilts out of the C(18)NC(19) plane
by 20.6Њ (in molecule B by 2.4Њ and 13.5Њ, respectively). As
expected,30 the E–N–S–C torsion angles (E is the pπ(N) orbital
direction) are small viz. 9.5(2)Њ in A and 15.1(2)Њ in B. However,
the orientation of the benzene ring is not the expected one: the
torsion angles N–S–C–C of 62.1(2)Њ (A) and 62.6(2)Њ (B) are far
from the 90Њ expected for Cs molecular symmetry.
Fig. 7 Two independent molecules of 30 in the crystal structure.
the long n-butyl chains, in 30 the dithiole ring itself and its
methylsulfanyl substituents are accommodated therein, with
short intradimer contacts S(2). . .S(5ii) 3.59 Å and S(8). . .S(13iii)
3.60 Å for A and B, respectively. Dimers of each type, related by
the a–b translation, contact by their dithiole–pyrrole systems in
a face-to-face fashion, thus forming an infinite chain (Fig. 8).
The contact between BBiii dimers is rather close: the dithiole–
pyrrole systems overlap in a nearly eclipsed manner (pyrrole
over dithiole ring, and vice versa) with the interplanar separ-
ation of 3.52 Å. For AAii dimers the separation is larger (3.66
Å) and there is a large lateral shift between the fused systems.
The chains can also be described as combining into a layer,
parallel to the (1 Ϫ1 0) plane. Thus, pronounced intermolecular
π–π interactions were indeed observed in the crystal structures
of 30, 33 and 34, as a consequence of the extension of the
π-system of one of the 1,3-dithiole rings.
In conclusion, a range of new TTFAQ derivatives has been
obtained, using the di(halomethyl) compounds 10, 11 and 18
as key reagents which are available in synthetically-useful
quantities. Their derived products display interesting redox
and structural properties, and TTFAQ–π-acceptor systems
(acceptor = anthraquinone, TTFAQ2ϩ and tetranitrofluorene)
have been characterised. These compounds are versatile redox-
active systems, and by virtue of their synthetic utility and
molecular electronic properties these TTFAQ derivatives
Each of the independent molecules and its own inversion
equivalent form a mutually engulfing dimer. In contrast with
structures 33 and 34, where the molecular cavity is occupied by
O r g . B i o m o l . C h e m . , 2 0 0 3 , 1, 5 1 1 – 5 2 2
517

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fluoride (115 cm3 of a 1.0 M solution in tetrahydrofuran, 115
mmol) over 15 min. Stirring under argon at room temperature
was continued for 2 h, whereupon water (500 cm3) was added to
afford a red precipitate. The precipitate was filtered, washed
with water (40 cm3) and methanol (3 × 40 cm3), and dried in
vacuum over phosphorus pentoxide to give 9 as an orange
powder sufficiently pure for further reaction (11.48 g, 84%).
Compound 9 could be recrystallised from ethanol–hexane to
1
give small red needles, mp 245Ϫ247 ЊC (decomp.). H NMR
(DMSO-d6): δ 8.13 (2 H, d, J = 7.6 Hz), 7.94 (2 H, d, J = 7.6 Hz),
7.78 (2 H, t, J = 7.6 Hz), 7.50 (2 H, t, J = 7.6 Hz), 5.61 (2 H, t,
J = 5.6 Hz), 4.33 (4 H, d, J = 5.6 Hz). 13C NMR (CDCl3):
δ 182.1, 144.5, 138.4, 132.3, 130.6, 129.5, 126.5, 126.44, 126.43,
115.6, 56.0. MS (EI): m/z (%) 354 (45, Mϩ), 336 (100). Calcd.
for C19H14O3S2: 354.03844. HRMS (EI): 354.03791 (Ϫ1.5 ppm).
10-[4,5-Bis(bromomethyl)-1,3-dithiol-2-ylidene]anthracene-
9(10H)-one (10)
Compound 9 (11.40 g, 32.16 mmol) was dissolved in dry N,N-
dimethylformamide (150 cm3) and stirred at 0 ЊC under argon.
Phosphorus tribromide (9.07 cm3, 96.50 mmol) was added via
syringe over 5 min, accompanied by a colour change from red
to yellow–orange. Stirring at 0 ЊC was continued for 30 min
followed by another 2 h at room temperature, after which a
yellow precipitate was formed. Methanol (500 cm3) was added
to precipitate the remaining product, whereupon the reaction
mixture was filtered. The yellow precipitate was washed with
water (30 cm3) and methanol (3 × 30 cm3), and dried in a
vacuum over phosphorus pentoxide to give 10 as a yellow
powder sufficiently pure for further reaction (13.76 g, 89%), mp
228Ϫ230 ЊC (from dichloromethane–hexane, decomp.). 1H
NMR (CDCl3): δ 8.27 (2 H, d, J = 7.2 Hz), 7.82 (2 H, d, J = 7.6
Hz), 7.67 (2 H, t, J = 7.6 Hz), 7.46 (2 H, t, J = 7.6 Hz), 4.23 (4 H,
s). 13C NMR (CDCl3): δ 183.5, 138.6, 137.8, 131.9, 130.7, 129.6,
127.3, 127.1, 126.1, 119.4, 21.3. MS (EI): m/z (%) 482 (4, [M ϩ
4]ϩ), 480 (7, [M ϩ 2]ϩ), 478 (4, Mϩ), 320 (100). Anal. calcd. for
C19H12Br2OS2 (MW 480.24): C, 47.52; H, 2.52. Found C, 47.70;
H, 2.53.
Fig. 8 Crystal packing of 30. Symmetry operations: (i) x ϩ 1, y Ϫ 1, z;
(ii) 1 Ϫ x, Ϫy, Ϫz; (iii) 1 Ϫ x, 2 Ϫ y, 1 Ϫ z; (iv) 2 Ϫ x, Ϫy Ϫ 1, Ϫz;
(v) 1 Ϫ x, 1 Ϫ y, 1 Ϫ z.
should continue to attract attention among the organic and
materials chemistry communities.
Experimental
General procedures and equipment
These are the same as those reported previously.9
4,5-Bis(tert-butyldiphenylsiloxymethyl)-2-methylsulfanyl-1,3-
dithiolium trifluoromethanesulfonate (6)
Compound 516 (28.50 g, 42.47 mmol) was dissolved in dry
degassed dichloromethane (200 cm3) and stirred under argon at
room temperature. Methyl triflate (5.00 cm3, 44.18 mmol) was
added in one portion and the stirring was continued for 1 h,
whereupon the solution changed from yellow to almost colour-
less. Concentration in vacuo afforded a pale yellow salt 6, which
10-[4,5-Bis(chloromethyl)-1,3-dithiol-2-ylidene]anthracene-
9(10H)-one (11)
1
was used without further purification, mp 90–91 ЊC. H NMR
(CDCl3): δ 7.57–7.52 (8 H, m), 7.44–7.35 (12 H, m), 4.66 (4 H,
s), 3.17 (3 H, s), 1.04 (18 H, s).
To a stirred solution of 9 (0.210 g, 0.59 mmol) in dry N,N-
dimethylformamide (7 cm3) at 0 ЊC under argon was added
thionyl chloride (0.211 g, 1.78 mmol) dropwise via syringe,
whereupon the colour changed from dark red to pale brown.
The reaction mixture was stirred for 30 min, whilst slowly
warming to room temperature, and diluted with dichloro-
methane (100 cm3). The organic phase was washed with water
(3 × 100 cm3), dried (MgSO4) and concentrated in vacuo. Purifi-
cation of the residue by column chromatography (silica gel,
dichloromethane–hexane, 2 : 1 v/v) afforded 11 as small yellow
crystals (0.192 g, 83%), mp 230 ЊC (decomp.). 1H NMR
(CDCl3): δ 8.27 (2 H, d, J = 8.0 Hz), 7.83 (2 H, d, J = 8.0 Hz),
7.67 (2 H, t, J = 7.5 Hz), 7.46 (2 H, t, J = 7.5 Hz), 4.36 (4 H, s).
13C NMR (CDCl3): δ 183.5, 138.6, 138.2, 131.9, 130.7, 129.3,
127.3, 127.0, 126.1, 119.6, 36.1. MS (EI): m/z (%) 394 (2, [M ϩ
4]ϩ), 392 (5, [M ϩ 2]ϩ), 390 (6, Mϩ), 208 (100). Anal. calcd. for
C19H12Cl2OS2 (MW 391.34): C, 58.31; H, 3.09. Found C, 58.35;
H, 3.05.
10-[4,5-Bis(tert-butyldiphenylsiloxymethyl)-1,3-dithiol-2-
ylidene]anthracene-9(10H)-one (8)
Salt 6 (from 28.50 g, 42.47 mmol of 5) and anthrone 7 (8.24 g,
42.4 mmol) were dissolved in a 3 : 1 (v/v) mixture of pyridine–
acetic acid (400 cm3) and stirred under argon at 60 ЊC for 3 h
and then at 120 ЊC for another 3 h. The dark red mixture was
concentrated under reduced pressure, redissolved in dichloro-
methane (500 cm3), washed with water (2 × 400 cm3) and brine
(400 cm3), dried (MgSO4) and concentrated in vacuo. The resi-
due was chromatographed (silica gel, dichloromethane–hexane,
3 : 1 v/v) affording 8 as an orange powder (32.00 g, 91% from 5),
mp 128Ϫ129 ЊC (from chloroform–methanol). 1H NMR
(CDCl3): δ 8.32 (2 H, d, J = 8.0 Hz), 7.93 (2 H, d, J = 8.0 Hz),
7.67Ϫ7.63 (2 H, m), 7.59Ϫ7.56 (8 H, m), 7.46–7.30 (14 H, m),
4.19 (s, 4 H), 1.02 (s, 18 H). 13C NMR (CDCl3): δ 183.6, 143.9,
139.1, 135.5, 132.4, 131.5, 130.5, 129.9, 129.2, 127.8, 127.0,
126.3, 126.1, 116.6, 59.0, 26.6, 19.2. MS (PD): m/z = 831.2
(theory: 831.2). Anal. calcd. for C51H50O3S2Si2 (MW 831.24): C,
73.69; H, 6.06. Found C, 73.45; H, 6.22.
Compound 14
Compound 11 (0.115 g, 0.294 mmol), dimethyl acetylene-
dicarboxylate (0.14 cm3, 0.167 g, 1.18 mmol), potassium iodide
(0.146 g, 0.882 mmol) and 18-crown-6 (0.233 g, 0.882 mmol)
were dissolved in dry toluene (70 cm3) and stirred under argon
at 100 ЊC for 2 h, in which time the colour changed from yellow
to brown. DDQ (0.133 g, 0.588 mmol) was added to the
reaction mixture, which was stirred for another 1 h at 100 ЊC.
10-[4,5-Bis(hydroxymethyl)-1,3-dithiol-2-ylidene]anthracene-
9(10H)-one (9)
To a stirred solution of 8 (32.00 g, 38.50 mmol) in dry tetrahydro-
furan (200 cm3) was added a solution of tetrabutylammonium
O r g . B i o m o l . C h e m . , 2 0 0 3 , 1, 5 1 1 – 5 2 2
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The mixture was diluted with dichloromethane (200 cm3),
washed with an aqueous 0.5% sodium thiosulfate solution
(3 × 200 cm3) and water (200 cm3), dried (MgSO4) and filtered
through a short silica column, eluting with dichloromethane–
toluene, 1 : 1 v/v. The filtrate was concentrated in vacuo and the
residue purified by column chromatography (silica gel, di-
chloromethane–ethyl acetate, 95 : 5 v/v) affording 14 as small
golden needles (0.082 g, 61%), mp >250 ЊC. 1H NMR (CDCl3):
δ 8.26 (2 H, d, J = 7.8 Hz), 7.90 (2 H, d, J = 7.8 Hz), 7.69 (2 H, t,
J = 7.5 Hz), 7.60 (2 H, s), 7.49 (2 H, t, J = 7.5 Hz), 3.89 (6 H, s).
13C NMR (CDCl3): δ 183.6, 166.8, 138.7, 138.6, 137.8, 131.9,
131.0, 130.2, 127.5, 127.3, 126.3, 121.3, 121.2, 52.9. MS (EI):
m/z (%) 460 (100, Mϩ). Anal. calcd. for C25H16O5S2 (MW
460.52): C, 65.20; H, 3.50. Found C, 64.80; H, 3.44.
9-[4,5-Bis(chloromethyl)-1,3-dithiol-2-ylidene]-10-[4,5-bis-
(hexylsulfanyl)-1,3-dithiol-2-ylidene]-9,10-dihydroanthracene
(18)
To a solution of 17 (0.600 g, 0.891 mmol) in dry degassed
acetonitrile (10 cm3) was added dry carbon tetrachloride (3.0
cm3) and triphenylphosphine (0.701 g, 2.67 mmol) whereupon
the reaction was stirred under argon at 80 ЊC for 20 min, in
which time the colour changed from yellow to dark brown. The
reaction mixture was cooled to room temperature and immedi-
ately filtered through a plug of silica, eluting with ethyl acetate,
to remove the brown baseline material. The yellow solution was
concentrated in vacuo and the product was triturated with
cyclohexane to give a yellow solid which was filtered off, washed
with methanol and dried, affording 18 as a yellow powder
1
(0.415 g, 66%), mp 97–99 ЊC. H NMR (CDCl3): δ 7.61–7.58
9-[4,5-Bis(tert-butyldiphenylsiloxymethyl)-1,3-dithiol-2-
ylidene]-10-[4,5-bis(hexylsulfanyl)-1,3-dithiol-2-ylidene]-9,10-
dihydroanthracene (16)
(4 H, m), 7.32–7.30 (4 H, m), 4.31 (4 H, s), 2.86–2.74 (4 H, m),
1.65–1.59 (4 H, m), 1.42–1.36 (4 H, m), 1.30–1.26 (8 H, m), 0.87
(6 H, t, J = 7.0 Hz). 13C NMR (CDCl3): δ 134.7, 134.6, 131.9,
129.0, 128.8, 126.5, 126.2 (2C), 125.4, 125.2, 123.9, 122.5, 36.5,
36.3, 31.3, 29.6, 28.2, 22.5, 14.0. UV-vis (CH2Cl2): λmax (lg ε)
361 (4.21), 430 (4.47) nm. MS (ES): m/z (%) = 712 (16, [Mϩ4]ϩ),
710 (84, [Mϩ2]ϩ), 708 (100, Mϩ). Calcd. for C34H38Cl2S6:
708.06749. HRMS (ES): 708.06777 (ϩ0.4 ppm).
To a solution of the phosphonate ester 1518 (1.35 g, 3.05 mmol)
in dry tetrahydrofuran (100 cm3) at Ϫ78 ЊC under argon was
added lithium diisopropylamide (2.23 cm3 of a 1.5 M solution
in cyclohexane, 3.35 mmol) via syringe and the resultant cloudy
yellow mixture was stirred for 2 h. Compound 8 (2.11 g, 2.54
mmol) was added to the mixture as a solid, against a positive
pressure of argon, which afforded an orange suspension. The
suspension was stirred at Ϫ78 ЊC for another 2 h, whereupon
it was allowed to slowly attain room temperature overnight.
Evaporation of the solvent gave a red residue which was dis-
solved in dichloromethane (200 cm3), washed with water (200
cm3) and brine (200 cm3), dried (MgSO4) and concentrated
in vacuo. Purification by column chromatography (silica gel,
dichloromethane–hexane, 1 : 3 v/v) afforded 16 as a yellow foam
Compound 21
Compound 18 (0.100 g, 0.141 mmol), naphthoquinone 20
(0.089 g, 0.563 mmol), potassium iodide (0.070 g, 0.423 mmol)
and 18-crown-6 (0.112 g, 0.423 mmol) were dissolved in dry
toluene (40 cm3) and stirred under argon at 90 ЊC for 5 h, in
which time the colour changed from yellow to dark brown.
DDQ (0.128 g, 0.563 mmol) was added to the reaction mixture,
which was stirred for another 4 h at 90 ЊC. The colour changed
to red–brown and a black precipitate formed. The mixture was
diluted with dichloromethane (200 cm3), washed with aqueous
0.5% sodium thiosulfate solutions (3 × 200 cm3) and water (200
cm3), dried (MgSO4) and filtered through a short silica column,
eluting with dichloromethane–toluene, 1 : 1 v/v. Evaporation of
the solvent under reduced pressure followed by column chrom-
atography (silica gel, dichloromethane–hexane, 1 : 1 v/v)
afforded 21 as shiny black–red crystals (0.070 g, 63%), mp 229–
230 ЊC. 1H NMR (CDCl3): δ 8.28–8.26 (2 H, m), 8.08 (2 H, s),
7.80–7.77 (2 H, m), 7.73–7.70 (2 H, m), 7.65–7.63 (2 H, m),
7.39–7.37 (4 H, m), 2.84–2.71 (4 H, m), 1.62–1.53 (4 H, m),
1.39–1.32 (4 H, m), 1.28–1.21 (8 H, m), 0.83 (6 H, t, J = 6.8 Hz).
13C NMR (CDCl3): δ 181.9, 143.7, 134.9, 134.4, 134.2, 133.2,
132.7, 131.4, 128.7, 127.2, 127.0, 126.3, 126.22, 126.19, 125.5
(2C), 122.1, 118.8, 36.2, 31.2, 29.6, 28.1, 22.5, 14.0. UV-vis
(CH2Cl2): λmax (lg ε) 350 (4.55), 427 (4.50) nm. MS (EI): m/z (%)
= 792 (Mϩ, 78), 502 (100). Calcd. for C44H40O2S6: 792.13526.
HRMS (EI): 792.13524 (ϩ0.0 ppm).
1
(2.26 g, 77%), mp 56–58 ЊC. H NMR (CDCl3): δ 7.72Ϫ7.70
(2 H, m), 7.60Ϫ7.56 (10 H, m), 7.39–7.28 (16 H, m), 4.18 (2 H,
d, J = 12.8 Hz), 4.11 (2 H, d, J = 13.2 Hz), 2.88–2.73 (4 H, m),
1.65–1.58 (4 H, m), 1.41–1.34 (4 H, m), 1.31–1.23 (8 H, m), 1.01
(18 H, s), 0.87 (6 H, t, J = 6.8 Hz). 13C NMR (CDCl3): δ 135.54,
135.52, 135.3, 134.7, 133.8, 132.6, 132.5, 130.4, 129.8, 128.4,
127.7, 126.1, 126.0, 125.7, 125.4, 125.2, 123.4, 121.1, 59.1, 36.2,
31.3, 29.7, 28.2, 26.6, 22.5, 19.2, 14.0. UV-vis (CH2Cl2): λmax (lg
ε) 366 (4.19), 438 (4.43) nm. MS (PD): m/z = 1148.6 (theory:
1149.9). Anal. calcd. for C66H76O2S6Si2 (MW 1149.88): C,
68.94; H, 6.66. Found C, 68.86; H, 6.73.
9-[4,5-Bis(hexylsulfanyl)-1,3-dithiol-2-ylidene]-10-[4,5-bis(hydr-
oxymethyl)-1,3-dithiol-2-ylidene]-9,10-dihydroanthracene (17)
Compound 16 (2.21 g, 1.93 mmol) was dissolved in dry tetra-
hydrofuran (25 cm3) and stirred under argon at room temper-
ature. A solution of tetrabutylammonium fluoride (5.78 cm3 of
a 1.0 M solution in tetrahydrofuran, 5.78 mmol) was added
dropwise via syringe over 15 min, inducing a colour change
from yellow to light brown. Further stirring for 1.5 h, followed
by addition of a few drops of water (0.1 cm3) and evaporation
of the solvent afforded a brown residue which was dissolved in
dichloromethane (200 cm3), washed with water (200 cm3) and
brine (200 cm3), dried (MgSO4) and concentrated in vacuo.
Chromatography using a short column (silica gel, dichloro-
methane until no more traces of by-products were visible on the
column, then dichloromethane–ethyl acetate, 2 : 1 v/v) afforded
Compound 23
To a stirred solution of compound 2218 (0.183 g, 0.60 mmol)
in dry tetrahydrofuran (50 cm3) at Ϫ78 ЊC under argon was
added lithium diisopropylamide (0.44 cm3 of a 1.5 M solution
in cyclohexane, 0.66 mmol) and the resultant cloudy yellow
mixture was stirred for 2 h at Ϫ78 ЊC. Compound 21 (0.045 g,
0.057 mmol) was dissolved in dry tetrahydrofuran (100 mL)
with sonication and added to the reaction mixture via syringe
over 1 h. The reaction mixture was stirred at Ϫ78 ЊC for another
1 h, whereupon it was allowed to slowly attain room temper-
ature for 12 h. Evaporation of the solvent afforded a red residue
which was dissolved in dichloromethane (100 cm3), washed
with water, dried (MgSO4) and concentrated in vacuo. Column
chromatography (silica gel, dichloromethane–hexane, 1 : 1 v/v)
afforded an orange powder which was purified using a short
column (silica gel, carbon disulfide) to give 23 as a yellow
1
17 as a yellow solid (1.14 g, 88%), mp 110–111 ЊC. H NMR
(CDCl3): δ 7.62–7.55 (4 H, m), 7.28–7.26 (4 H, m), 4.27–4.17
(4 H, m), 2.93 (2 H, t, J = 5.6 Hz), 2.80–2.75 (4 H, m), 1.63–1.56
(4 H, m), 1.40–1.33 (4 H, m), 1.29–1.24 (8 H, m), 0.87 (6 H, t,
J = 6.8 Hz). 13C NMR (CDCl3): δ 134.8, 134.5, 131.9, 131.4,
129.9, 126.1(2C), 125.9, 125.5, 125.1, 123.1, 122.6, 56.8, 36.2,
31.3, 29.6, 28.2, 22.5, 14.0. UV-vis (CH2Cl2): λmax (lg ε) 269
(4.24), 364 (4.20), 432 (4.45) nm. MS (PD): m/z = 672.2 (theory:
673.1). Anal. calcd. for C34H40O2S6 (MW 673.08): C, 60.67; H,
5.99. Found C, 60.51; H, 5.99.
1
powder (0.058 g, 88%), mp 154–156 ЊC. H NMR (CDCl3):
O r g . B i o m o l . C h e m . , 2 0 0 3 , 1, 5 1 1 – 5 2 2
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δ 7.80–7.78 (0.6 H, m), 7.71–7.69 (1.4 H, m), 7.62–7.60 (2 H,
m), 7.49–7.47 (2 H, m), 7.38–7.27 (8 H, m), 2.85–2.71 (4 H, m),
2.43 (1.9 H, s), 2.39 (1.9 H, s), 2.35 (4.1 H, s), 2.31 (4.1 H, s),
1.63–1.54 (4 H, m), 1.41–1.31 (4 H, m), 1.29–1.20 (8 H, m), 0.85
(4.1 H, t, J = 7.0 Hz), 0.81 (1.9 H, t, J = 7.0 Hz). UV-vis
(CH2Cl2): λmax (lg ε) 275 (4.74), 377 (4.51), 440 (4.73) nm.
MS (ES): m/z (%) 1187 (100, [MϩK]ϩ), 1171 (31, [MϩNa]ϩ),
1148 (28, Mϩ). Calcd. for C54H52S14: 1148.0159. HRMS (ES):
1148.0148 (Ϫ1.0 ppm).
in dry tetrahydrofuran (50 mL) at Ϫ78 ЊC under argon was
added lithium diisopropylamide (0.86 cm3 of a 1.5 M solution
in cyclohexane, 1.30 mmol) via syringe and the resultant cloudy
yellow mixture was stirred for 1.5 h at Ϫ78 ЊC. Ketone 27 (0.500
g, 1.03 mmol) was dissolved in dry tetrahydrofuran (25 cm3)
and added to the reaction mixture via syringe over 30 min. The
reaction mixture was stirred at Ϫ78 ЊC for another 2 h, where-
upon it was allowed to slowly attain room temperature for 12 h.
Evaporation of the solvent afforded a red residue which was
dissolved in dichloromethane (100 cm3), washed with brine,
dried (MgSO4) and concentrated in vacuo. Column chromato-
graphy (silica gel, dichloromethane–cyclohexane, 2 : 1 v/v)
afforded 30 as a yellow powder. Recrystallisation from dichloro-
methane–heptane gave yellow prisms suitable for X-ray crystal-
Generation and 1H NMR spectrum of the tetracation 234؉
To half the volume of the NMR sample of 23 was added a
solution of iodine (excess) in CDCl3 to give a red precipitate
which was filtered, dried in vacuo, dissolved in DMSO-d6 and
the 1H NMR spectrum of 234ϩ was recorded. 1H NMR (DMSO-
d6): δ 8.15 (2 H, s), 8.03–8.01 (2 H, m), 7.76–7.74 (4 H, m), 7.65–
7.64 (2 H, m), 7.50–7.43 (4 H, m), 2.99 (12 H, s), 2.81 (4 H, t,
J = 7.5 Hz), 1.54–1.47 (4 H, m), 1.35–1.29 (4 H, m), 1.23–1.17
(8 H, m), 0.78 (6 H, t, J = 7.0 Hz).
1
lography (0.590 g, 86%), mp 259–260 ЊC. H NMR (CDCl3):
δ 7.69 (2 H, d, J = 8.4 Hz), 7.66–7.64 (2 H, m), 7.56–7.54 (2 H,
m), 7.33–7.30 (4 H, m), 7.25 (2 H, d, J = 8.4 Hz), 6.85 (2 H, s),
2.38 (3 H, s), 2.35 (6 H, s). 13C NMR (CDCl3): δ 145.3, 138.8,
135.3, 134.9, 134.8, 131.5, 130.1, 126.9, 126.7, 126.6, 126.5,
126.3, 125.9, 125.7, 125.3, 123.3, 110.5, 21.6, 19.1. UV-vis
(CH2Cl2): λmax (lg ε) 353 (4.31), 422 (4.42) nm. MS (PD): m/z =
665.0 (theory: 666.0). Anal. calcd. for C31H23NO2S7 (MW
665.98): C, 55.91; H, 3.48; N, 2.10. Found C, 55.93; H, 3.42; N,
2.09.
10-{4,6-Dihydro-N-tosylpyrrolo[3,4-d]-1,3-dithiol-2-ylidene}-
anthracene-9(10H )-one (26)
Sodium tosylamide 2531 (2.68 g, 13.9 mmol) was suspended in
dry acetonitrile (50 cm3) and stirred under argon at 80 ЊC.
Compound 10 (3.33 g, 6.93 mmol) was dissolved in a minimum
of dry N,N-dimethylformamide (200 cm3) stirred at 80 ЊC and
transferred to the sodium tosylamide suspension over 10 min
using a double ended needle and a positive pressure of argon.
The dark brown reaction mixture was stirred for another 5 min
at 80 ЊC before being cooled to 0 ЊC, using an ice bath, and
concentrated under reduced pressure. To the residue was added
water (150 cm3) and the mixture was extracted with dichloro-
methane (3 × 100 cm3). The combined organic phases were
dried (MgSO4), filtered through a plug of silica and concen-
trated in vacuo. Column chromatography (silica gel, dichloro-
methane until two minor by-products were off the column, then
dichloromethane–ethyl acetate, 95 : 5 v/v) afforded 26 as an
9-{N-Tosylpyrrolo[3,4-d]-1,3-dithiol-2-ylidene}-10-{4,5-bis-
(butylsulfanyl)-1,3-dithiol-2-ylidene}-9,10-dihydroanthracene
(31)
This procedure is similar to the synthesis of 30 using compound
2918 (0.427 g, 1.10 mmol) in dry tetrahydrofuran (50 cm3),
lithium diisopropylamide (0.81 cm3 of a 1.5 M solution in
cyclohexane, 1.21 mmol) and ketone 27 (0.400 g, 0.82 mmol)
in dry tetrahydrofuran (20 cm3). Purification by column
chromatography (silica gel, dichloromethane–cyclohexane, 1 : 1
v/v) afforded 31 as a yellow powder (0.560 g, 91%), mp 191–192
1
ЊC. H NMR (CDCl3): δ7.69 (2 H, d, J = 8.5 Hz), 7.66–7.64
(2 H, m), 7.60–7.58 (2H, m), 7.33–7.30 (4 H, m), 7.26 (2 H, d,
J = 7.5 Hz), 6.85 (2 H, s), 2.84–2.72 (4 H, m), 2.38 (3 H, s), 1.61–
1
orange powder (2.77 g, 82%), mp 218–220 ЊC (decomp.). H
1.55 (4 H, m), 1.44–1.36 (4 H, m), 0.89 (6 H, t, J = 7.5 Hz). 13
C
NMR (CDCl3): δ 8.21 (2 H, d, J = 7.5 Hz), 7.76 (2 H, d, J = 8.0
Hz), 7.68 (2 H, d, J = 8.0 Hz), 7.61 (2 H, t, J = 7.5 Hz), 7.42
(2 H, t, J = 7.5 Hz), 7.30 (2 H, d, J = 8.5 Hz), 4.25 (4 H, s), 2.39
(3 H, s). 13C NMR (CDCl3): δ 183.4, 147.8, 144.3, 138.5, 133.3,
131.8, 130.6, 130.1, 127.3, 127.2, 127.1, 126.3, 126.0, 121.0,
52.4, 21.5. MS (EI): m/z (%) 489 (14, Mϩ), 91 (100). Calcd. for
C26H19NO3S3: 489.05271. HRMS (EI): 489.05200 (Ϫ1.5 ppm).
NMR (CDCl3): δ 145.3, 138.6, 135.3, 135.0, 134.9, 132.0, 130.0,
126.9, 126.7, 126.62, 126.57, 126.2 (2C), 125.9, 125.2, 122.4,
110.5, 35.9, 31.7, 21.61, 21.58, 13.6. UV-vis (CH2Cl2): λmax (lg ε)
353 (4.30), 423 (4.41) nm. MS (EI): m/z (%) 749 (100, Mϩ).
Calcd. for C37H35NO2S7: 749.0713. HRMS (ES): 749.0725
(ϩ1.6 ppm).
9-{Pyrrolo[3,4-d]-1,3-dithiol-2-ylidene}-10-{4,5-bis(methyl-
sulfanyl)-1,3-dithiol-2-ylidene}-9,10-dihydroanthracene (32)
10-{N-Tosylpyrrolo[3,4-d]-1,3-dithiol-2-ylidene}anthracene-
9(10H)-one (27)
Compound 30 (0.500 g, 0.751 mmol) was dissolved in dry
degassed tetrahydrofuran–methanol, 2 : 1 v/v (50 cm3). Sodium
methoxide (2.2 cm3 of a 30% solution in methanol, 11.3 mmol)
was added to the solution and the reaction refluxed for 15 min
under argon, in which time the colour changed from yellow to
brown. The reaction mixture was cooled to room temperature,
water was added (10 cm3) and the mixture was concentrated to
10 cm3 under reduced pressure. The residue was taken into
dichloromethane (100 cm3), washed with water and brine, dried
(MgSO4) and concentrated in vacuo. Column chromatography
(silica gel, dichloromethane–cyclohexane, 2 : 1 v/v) afforded 32
as a yellow powder which darkens upon standing (0.334 g,
87%), mp > 280 ЊC. 1H NMR (CDCl3): δ 8.17 (1 H, br s), 7.78–
7.76 (2 H, m), 7.54–7.53 (2 H, m), 7.35–7.29 (4 H, m), 6.56 (2 H,
d, J = 2.5 Hz), 2.36 (6 H, s). 13C NMR (CDCl3): δ 142.2, 135.4,
134.9, 130.6, 126.2 (2C), 126.0, 125.8, 125.3, 124.6, 124.1, 119.1,
109.0, 19.2. UV-vis (CH2Cl2): λmax (lg ε) 362 (4.21), 428 (4.46)
nm. MS (EI): m/z (%) 511 (100, Mϩ). Anal. calcd. for
C24H17NS6 (MW 511.79): C, 56.32; H, 3.35; N, 2.74. Found C,
56.54; H, 3.46; N, 2.76.
To a suspension of 26 (8.70 g, 17.8 mmol) in chlorobenzene
(200 cm3) was added DDQ (4.84 g, 21.3 mmol) and the mixture
was refluxed for 1 h. The reaction mixture was cooled to room
temperature and reduced to 50 mL in vacuo. The resulting
suspension was chromatographed (silica gel column, dichloro-
methane) to give 27 as a yellow powder (7.98 g, 92%), mp
250–251 ЊC (decomp.). 1H NMR (CDCl3): δ 8.21 (2 H, d, J = 7.5
Hz), 7.90 (2 H, d, J = 8.0 Hz), 7.69 (2 H, d, J = 8.5 Hz), 7.64 (2
H, t, J = 7.5 Hz), 7.46 (2 H, t, J = 7.5 Hz), 7.26 (2 H, d, J = 8.0
Hz), 6.94 (2 H, s), 2.38 (3 H, s). 13C NMR (CDCl3): δ 183.9,
146.9, 145.6, 139.1, 135.2, 131.7, 131.1, 130.1, 127.4, 127.1,
126.9, 126.7, 125.7, 122.4, 110.8, 21.6. MS (PD): m/z = 486.6
(theory: 487.6). Anal. calcd. for C26H17NO3S3 (MW 487.62): C,
64.04; H, 3.51; N, 2.87. Found C, 63.80; H, 3.35; N, 2.92.
9-{N-Tosylpyrrolo[3,4-d]-1,3-dithiol-2-ylidene}-10-{4,5-bis-
(methylsulfanyl)-1,3-dithiol-2-ylidene}-9,10-dihydroanthracene
(30)
To a solution of the phosphonate ester 2218 (0.359 g, 1.18 mmol)
O r g . B i o m o l . C h e m . , 2 0 0 3 , 1, 5 1 1 – 5 2 2
520

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9-{Pyrrolo[3,4-d]-1,3-dithiol-2-ylidene}-10-{4,5-bis(butyl-
sulfanyl)-1,3-dithiol-2-ylidene}-9,10-dihydroanthracene (33)
358 (4.18), 425 (4.45) nm. MS (EI): m/z (%) 539 (100, Mϩ).
Accurate mass calcd. for C25H17NOS6: 538.96345. HRMS (EI):
538.96323 (Ϫ0.4 ppm).
By a procedure similar to the conversion of 30 into 32, com-
pound 31 (1.60 g, 2.13 mmol) in dry degassed tetrahydrofuran–
methanol, 2 : 1 v/v (100 cm3) with sodium methoxide (4.8 cm3
of a 30% solution in methanol, 25 mmol) gave 33. Purification
by column chromatography (silica gel, dichloromethane–cyclo-
hexane, 1 : 2 v/v) afforded 33 as a yellow solid. Recrystallisation
from dichloromethane–heptane gave yellow–brown prisms,
(1.05 g, 83%), mp 221–222 ЊC. 1H NMR (CDCl3): δ 8.13 (1 H,
br s), 7.77–7.75 (2 H, m), 7.58–7.57 (2 H, m), 7.34–7.29 (4H, m),
6.52 (2H, d, J = 2.5 Hz), 2.84–2.79 (2H, m), 2.77–2.71 (2H, m),
1.61–1.55 (4 H, m), 1.44–1.36 (4 H, m), 0.88 (6 H, t, J = 7.5 Hz).
13C NMR (CDCl3): δ 142.0, 135.4, 135.0, 131.1, 126.2 (2C),
126.1, 126.0, 125.2, 124.6, 123.0, 119.0, 109.0, 36.0, 31.7, 21.6,
13.6. UV-vis (CH2Cl2): λmax (lg ε) 368 (4.21), 429 (4.45) nm. MS
(PD): m/z = 596.7 (theory: 596.0). Anal. calcd. for C30H29NS6
(MW 595.95): C, 60.46; H, 4.90; N, 2.35. Found C, 60.17; H,
4.87; N, 2.27.
9-{4-Formylpyrrolo[3,4-d]-1,3-dithiol-2-ylidene}-10-{4,5-
bis(butylsulfanyl)-1,3-dithiol-2-ylidene}-9,10-dihydro-
anthracene (36)
By analogy with the synthesis of aldehyde 35, phosphorus
oxychloride (0.036 cm3, 0.059 g, 0.385 mmol) in dry N,N-
dimethylformamide (2 cm3) with 33 (0.153 g, 0.257 mmol) in
dry N,N-dimethylformamide (2 cm3) and column chromato-
graphy (silica gel, dichloromethane–ethyl acetate, 1 : 1 v/v)
afforded 36 as a yellow powder (0.146 g, 91%), mp 169–170 ЊC.
1H NMR (CDCl3): δ 9.86 (1 H, br s), 9.32 (1 H, s), 7.73–7.59 (4
H, m), 7.36–7.31 (4 H, m), 6.74 (1 H, br s), 2.83–2.69 (4 H, m),
1.59–1.50 (4 H, m), 1.41–1.33 (4 H, m), 0.88–0.85 (6 H, m).
UV-vis (CH2Cl2): λmax (lg ε) 306 (4.37), 359 (4.20), 427 (4.46)
nm. MS (PD): m/z = 622.9 (theory: 624.0). Anal. calcd. for
C31H29NOS6 (MW 623.96): C, 59.67; H, 4.68; N, 2.24. Found C,
59.82; H, 4.75; N, 2.23.
9-{N-Methylpyrrolo[3,4-d]-1,3-dithiol-2-ylidene}-10-{4,5-bis-
(butylsulfanyl)-1,3-dithiol-2-ylidene}-9,10-dihydroanthracene
(34)
Compound 38
Compound 35 (0.038 g, 0.070 mmol) and 2,4,5,7-tetranitro-
fluorene 3724a (0.029 g, 0.084 mmol) were dissolved in dry
degassed N,N-dimethylformamide (2 cm3) and stirred at room
temperature under argon for 2.5 h. The black mixture was
concentrated in vacuo and the residue purified by column
chromatography (silica gel, dichloromethane) to give 38 as
a black powder (0.049 g, 80%), mp >280 ЊC. 1H NMR
(DMSO-d6): δ 12.32 (1 H, s), 9.57 (1 H, s), 9.16 (1 H, s), 8.77–
8.66 (2 H, m), 7.74–7.65 (3 H, m), 7.58–7.55 (3 H, m), 7.48–7.41
(4 H, m), 2.36–2.33 (6 H, m). UV-vis (CH2Cl2): λmax (lg ε) 356
(4.51), 427 (4.47), 539 (4.22) nm. MS (PD): m/z = 867.8 (theory:
868.0). Accurate mass calcd. for C38H21N5O8S6: 866.97144.
HRMS (EI): 866.97188 (ϩ0.5 ppm).
To a stirred suspension of sodium hydride (0.020 g of a 60%
dispersion in mineral oil, 0.50 mmol) in dry degassed N,N-
dimethylformamide (20 cm3) under nitrogen was added
a degassed solution of 33 (0.100 g, 0.168 mmol) in dry N,N-
dimethylformamide (10 cm3) over 5 min, whereupon the
reaction mixture turned red. The reaction was stirred for
another 15 min at room temperature followed by addition of
methyl iodide (0.10 cm3, 0.227 g, 1.60 mmol): the colour turned
yellow. Stirring was continued for a further 15 min after which
time the reaction mixture was concentrated, taken into
dichloromethane (50 cm3), washed with water and dried
(MgSO4). Purification by column chromatography (silica gel,
dichloromethane–cyclohexane, 1 : 1 v/v) afforded 34 as a yellow
powder. Recrystallisation from dichloromethane–heptane gave
yellow prisms (0.099 g, 97%), mp 214–215 ЊC. 1H NMR
(CDCl3): δ 7.77–7.75 (2 H, m), 7.58–7.56 (2 H, m), 7.33–7.28
(4 H, m), 6.37 (2 H, s), 3.60 (3 H, s), 2.85–2.79 (2 H, m),
2.77–2.72 (2 H, m), 1.62–1.54 (4 H, m), 1.45–1.37 (4 H, m), 0.89
(6 H, t, J = 7.5 Hz). 13C NMR (CDCl3): δ 141.9, 135.5, 135.0,
131.0, 126.2, 126.1, 126.0 (2C), 125.1, 124.4, 123.0, 118.0, 112.8,
37.1, 36.0, 31.7, 21.6, 13.6. UV-vis (CH2Cl2): λmax (lg ε) 267
(4.32), 366 (4.19), 433 (4.46) nm. MS (PD): m/z = 611.4 (theory:
610.0). Anal. calcd. for C31H31NS6 (MW 609.98): C, 61.04; H,
5.12; N, 2.30. Found C, 60.92; H, 5.17; N, 2.32.
Compound 39
By analogy with the synthesis of 38 compound 36 (0.025 g,
0.040 mmol) and 2,4,5,7-tetranitrofluorene 37 (0.015 g, 0.043
mmol) in dry degassed N,N-dimethylformamide (2 cm3) and
column chromatography (silica gel, dichloromethane) afforded
39 as a black powder (0.033 g, 87%), mp 192–194 ЊC (decomp.).
1H NMR (CDCl3): δ 9.05 (0.2 H, s), 8.91 (0.2 H, s), 8.83 (0.8 H,
s), 8.74 (0.8 H, s), 8.70 (2 H, s), 8.52 (1 H, br s), 7.64–7.58 (4 H,
m), 7.48–7.41 (3 H, m), 7.31–7.19 (2 H, m), 6.87 (1 H, s), 2.73–
2.70 (4 H, m), 1.53–1.47 (4 H, m), 1.39–1.29 (4 H, m), 0.89–0.81
(6 H, m). UV-vis (CH2Cl2): λmax (lg ε) 357 (4.50), 428 (4.48), 538
(4.23) nm. MS (PD): m/z = 951.2 (theory: 952.2). Anal. calcd.
for C44H33N5O8S6 (MW 952.16): C, 55.50; H, 3.49; N, 7.36.
Found C, 55.51; H, 3.67; N, 7.22.
9-{4-Formylpyrrolo[3,4-d]-1,3-dithiol-2-ylidene}-10-{4,5-bis-
(methylsulfanyl)-1,3-dithiol-2-ylidene}-9,10-dihydroanthracene
(35)
Crystallographic studies
Phosphorus oxychloride (0.042 cm3, 0.069 g, 0.450 mmol) was
added to dry N,N-dimethylformamide (2 cm3) under nitrogen
and stirred for 10 min at room temperature. A solution of 32
(0.150 g, 0.293 mmol) in dry N,N-dimethylformamide (2 cm3)
was added dropwise over 5 min, whereupon the resulting dark
violet reaction mixture was stirred for another 20 min. A 10%
aqueous solution of sodium acetate (15 cm3) and water (10 cm3)
was added to the reaction mixture, which caused precipitation
of a yellow solid. The solid was filtered and redissolved in di-
chloromethane (50 cm3), washed with water, dried (MgSO4) and
concentrated under reduced pressure. The crude product was
columned (silica gel, dichloromethane–ethyl acetate, 1 : 1 v/v)
to give 35 as a yellow powder (0.145 g, 92%), mp >280 ЊC
(yellow microcrystals from chlorobenzene–heptane, decomp.).
1H NMR (CDCl3): δ 9.45 (1 H, s), 9.07 (1 H, br s), 7.76–7.76
(2 H, m), 7.60–7.56 (2 H, m), 7.39–7.34 (4 H, m), 6.83 (1 H, d,
J = 2.8 Hz), 2.37 (6 H, s). UV-vis (CH2Cl2): λmax (lg ε) 306 (4.36),
X-Ray diffraction experiments (see Table 2) were carried out on
a SMART 3-circle diffractometer with a 1K CCD area detector,
with graphite-monochromated Mo–Kα radiation (λ = 0.71073
Å) and a Cryostream open-flow N2 cryostat (Oxford Cryo-
systems). Full sphere of reciprocal space was covered by five
sets of 0.3Њ ω scans, each set with different φ and/or 2θ angles.
The intensities were corrected for absorption by numerical
integration based on real crystal shape. The structures were
solved by direct methods and refined by full-matrix least
squares against F2 of all data, using SHELXTL software.32 Full
crystallographic data, excluding structure factors, are provided
in Electronic Supplementary Information and have been
deposited at the Cambridge Crystallographic Data Centre.
CCDC reference numbers(s) 197523–197525. See http://
www.rsc.org/suppdata/ob/b2/b211153p/ for crystallographic
files in .cif or other electronic format.
O r g . B i o m o l . C h e m . , 2 0 0 3 , 1, 5 1 1 – 5 2 2
521

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Table 2 Crystal data
8 (a) T. Finn, M. R. Bryce, A. S. Batsanov and J. A. K. Howard,
Chem. Commun., 1999, 1835; (b) N. Godbert, A. S. Batsanov,
M. R. Bryce and J. A. K. Howard, J. Org. Chem., 2001, 66, 713;
(c) C. A. Christensen, A. S. Batsanov, M. R. Bryce and J. A. K.
Howard, J. Org. Chem., 2001, 66, 3313.
Compound
30
33
34
Formula
Formula weight
T /K
Symmetry
Space group
a/Å
b/Å
c/Å
α/Њ
β/Њ
C31H23NO2S7
665.92
120
Triclinic
P 1 (#2)
14.013(1)
14.151(1)
17.216(1)
88.99(1)
70.38(1)
68.04(1)
2959.5(3)
4
0.56
33907
15459
0.025
12754
0.035
0.092
0.47, Ϫ0.45
C30H29NS6
595.90
120
Triclinic
P 1 (#2)
9.226(1)
12.541(1)
12.760(2)
99.64(1)
95.44(1)
108.73(1)
1360.9(2)
2
0.52
16873
7114
0.033
6268
0.031
0.084
0.45, Ϫ0.30
C31H31NS6
609.93
296
Monoclinic
P21/n (#14)
12.276(3)
9.688(2)
25.605(5)
90
100.73(1)
90
2992(1)
4
0.48
35752
7991
0.053
5753
0.049
0.133
0.40, Ϫ0.42
9 N. Godbert and M. R. Bryce, J. Mater. Chem., 2002, 12, 27.
10 (a) G. Kodis, P. A. Liddell, L. de la Garza, A. L. Moore, T. A. Moore
and D. Gust, J. Mater. Chem., 2002, 12, 2100; (b) D. M. Guldi,
Chem. Soc. Rev., 2002, 31, 22.
11 (a) Y. Yamashita, Y. Kobayashi and T. Miyashi, Angew. Chem., Int.
Ed. Engl., 1989, 28, 1052; (b) A. J. Moore and M. R. Bryce, J. Chem.
Soc., Perkin Trans. 1, 1991, 157; (c) C. Boulle, O. Desmars,
N. Gautier, P. Hudhomme, M. Cariou and A. Gorgues, Chem.
Commun., 1999, 2197.
12 M. R. Bryce, A. J. Moore, D. Lorcy, A. S. Dhindsa and A. Robert,
J. Chem. Soc., Chem. Commun., 1990, 471.
13 (a) M. R. Bryce, T. Finn and A. J. Moore, Tetrahedron Lett., 1999,
40, 3221; (b) M. R. Bryce, T. Finn, A. J. Moore, A. S. Batsanov and
J. A. K. Howard, Eur. J. Org. Chem., 2000, 51; (c) N. Godbert,
M. R. Bryce, S. Dahaoui, A. S. Batsanov, J. A. K. Howard and
P. Hazendonk, Eur. J. Org. Chem., 2001, 749.
¯
¯
γ/Њ
V, Å3
Z
µ/mmϪ1
Refls collected
Unique refls
Rint
Refls F 2>2σ(F 2)
R[F 2>2σ(F 2)]
wR(F 2), all data
∆ρ/eÅϪ3
14 Preliminary communication: C. A. Christensen, M. R. Bryce,
A. S. Batsanov, J. A. K. Howard, J. O. Jeppersen and J. Becher,
Chem. Commun., 1999, 2433.
15 R. Gompper and E. Kutter, Chem. Ber., 1965, 98, 2825.
16 J. O. Jeppesen, K. Takimiya, N. Thorup and J. Becher, Synthesis,
1999, 803.
17 (a) J. Llacay, M. Mas, E. Molins, J. Veciana, D. Powell and
C. Rovira, Chem. Commun., 1997, 659; (b) J. Llacay, J. Veciana,
J. Vidal-Gancedo, J. L. Bourdelande, R. Gonzalez-Moreno and
C. Rovira, J. Org. Chem., 1998, 63, 5201; (c) P. Hudhomme, S. G.
Liu, D. Kreher, M. Cariou and A. Gorgues, Tetrahedron Lett., 1999,
40, 2927; (d ) P. Belik, A. Gügel, J. Spickermann and K. Müllen,
Angew. Chem., Int. Ed. Engl., 1993, 32, 78.
Acknowledgements
We thank EPSRC and the Danish Research Academy (C. A. C.)
for funding, and Dr D. F. Perepichka for providing a sample of
compound 37.
18 A. J. Moore and M. R. Bryce, Tetrahedron Lett., 1992, 33, 1373 and
references therein.
19 R. Appel, Angew. Chem., Int. Ed. Engl., 1975, 14, 801.
20 N. Gautier, N. Mercier, A. Riou, A. Gorgues and P. Hudhomme,
Tetrahedron Lett., 1999, 40, 5997.
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