Syntheses and X-ray crystal structures of functionalised 9,10-bis(1,3- dithiol-2-ylidene)-9,10-dihydroanthracene derivatives

Article abstract of DOI:10.1002/(SICI)1099-0690(200001)2000:1<51::AID-EJOC51>3.0.CO;2-K

The synthesis of new derivatives of 9,10-bis(1,3-dithiol-2-ylidene)- 9,10-dihydroanthracene has been achieved by two different routes. Deprotonation of 8 using LDA in THF at -78 °C, followed by in situ quenching of the lithiated intermediate 9 with N,N-dimethylformamide, N-methyl isothiocyanate and methyl chloroformate gave aldehyde, thioamide and methyl ester derivatives 10-12, respectively. Sulfur insertion into the lithiated species 9 followed by reaction of the transient thiolate anion with benzoyl chloride gave the thioester derivative 13 which served as a convenient shelf- stable precursor of other mono-functionalised derivatives of 8. Debenzoylation of 13 and trapping of the transient thiolate anion with iodomethane and 6-bromohexan-1-ol yielded 14 and 15, respectively. Reaction of cation salt 17 with the anion of anthrone 18 gave compound 20, the thiolate anion of which reacted with 6-bromohexan-1-ol to afford the alcohol derivative 21. Subsequent reactions gave alcohol derivative 25 of the title system. The unexpected product 29 was obtained from reaction of 28 with triethyl phosphite. The X-ray crystal structures of compounds 12, 14, 28, and 20 are reported. The molecules adopt a saddle-like conformation; the bis(1,3- dithiole) benzoquinone system is U-shaped through an 'accumulating bend' comprising the boat conformation of the central (quinonoid) ring, folding of both 1,3-dithiole rings along S···S vectors, and out-of-plane tilting of the exocyclic C=C bonds, all in the same (inward) direction.

Full text of DOI:10.1002/(SICI)1099-0690(200001)2000:1<51::AID-EJOC51>3.0.CO;2-K

FULL PAPER
Syntheses and X-ray Crystal Structures of Functionalised
9,10-Bis(1,3-dithiol-2-ylidene)-9,10-dihydroanthracene Derivatives
Martin R. Bryce,*[a] Terry Finn,[a] Adrian J. Moore,[a] Andrei S. Batsanov,[a]
and Judith A. K. Howard[a]
Keywords: Dithioles / Anthracenes / Lithiation / Electron donors / Crystal structures
The synthesis of new derivatives of 9,10-bis(1,3-dithiol-2-
ylidene)-9,10-dihydroanthracene has been achieved by two
Reaction of cation salt 17 with the anion of anthrone 18 gave
compound 20, the thiolate anion of which reacted with 6-
different routes. Deprotonation of 8 using LDA in THF at –78 bromohexan-1-ol to afford the alcohol derivative 21.
°C, followed by in situ quenching of the lithiated
intermediate with N,N-dimethylformamide, N-methyl
isothiocyanate and methyl chloroformate gave aldehyde,
Subsequent reactions gave alcohol derivative 25 of the title
system. The unexpected product 29 was obtained from
reaction of 28 with triethyl phosphite. The X-ray crystal
structures of compounds 12, 14, 28, and 29 are reported. The
9
thioamide and methyl ester derivatives 10–12, respectively.
Sulfur insertion into the lithiated species 9 followed by molecules adopt a saddle-like conformation; the bis(1,3-
reaction of the transient thiolate anion with benzoyl chloride
gave the thioester derivative 13 which served as
dithiole)benzoquinone system is U-shaped through an
‘accumulating bend’ comprising the boat conformation of the
a
convenient shelf-stable precursor of other mono- central (quinonoid) ring, folding of both 1,3-dithiole rings
functionalised derivatives of 8. Debenzoylation of 13 and along S···S vectors, and out-of-plane tilting of the exocyclic
trapping of the transient thiolate anion with iodomethane C=C bonds, all in the same (inward) direction.
and 6-bromohexan-1-ol yielded 14 and 15, respectively.
AgCl) in the cyclic voltammogram.[2b,6,7] A dramatic struc-
tural change accompanies oxidation to the dication: the
Introduction
In the context of new π-electron donor molecules related
to tetrathiafulvalene, bis(1,3-dithiole) systems with ex-
tended π-conjugation have received considerable attention
in the last few years, with emphasis on their use as compo-
nents of electronically conductive charge-transfer materials.
Representative structural modifications include derivatives
with the incorporation of vinylogous conjugation between
the two dithiole rings,[1] or those with quinonoid[2] or het-
eroaromatic[3] spacer units. The molecules which are planar
(or nearly planar) have been the most widely studied, with
the aim of obtaining face-to-face π dimers or stacks in the
solid state which generally favour highly conducting proper-
ties. In contrast to the planar extended π systems of this
type, we have a continuing interest in the saddle-shaped
9,10-bis(1,3-dithiol-2-ylidene)-9,10-dihydroanthracene sys-
tem 1, the first derivative of which, viz. 9,10-bis(benzo-1,3-
dithiol-2-ylidene)-9,10-dihydroanthracene, was synthesised
by Akiba et al.[4] We first reported the saddle-shaped struc-
ture of the neutral system in an X-ray crystallographic
study of the tetramethyl derivative 2,[5] and theoretical cal-
culations by other workers have established that steric hin-
drance introduced by benzoannulation of the quinonoidal
unit determines this loss of planarity.[6] Compounds 1 and
2 undergo a single, two-electron, oxidation wave to yield a
thermodynamically stable dication at Eox ca. ϩ0.3 V (vs Ag/
central anthracene ring becomes aromatic and planar, with
the 1,3-dithiolium cations almost orthogonal to this plane
(X-ray crystallographic evidence for 22ϩ).[5]
Herein we report our work on two different approaches
to a versatile range of derivatives of 1 which contain a reac-
tive functional group attached to one of the 1,3-dithiole
rings.[8] These derivatives are designed to enable system 1
to be exploited as a functionalised building block in the
fields of supramolecular and materials chemistry. This is a
new direction for studies on system 1. The known deriva-
tives of 1 are restricted to those with simple alkyl,[2b,5]
thioalkyl,[9] or aryl/thioaryl[4,10] substituents on the dithiole
rings, which are not suitable for further functionalisation.
Heterocyclic analogues,[11] and a few derivatives with sub-
stituents attached to the anthracenediylidene spacer[12] have
been reported. We also report the formation of an unexpec-
ted ring opened product obtained from derivative 28 during
the course of this work.
[a]
Department of Chemistry, University of Durham,
South Road, Durham DH1 3LE, UK
Fax: (internat.) ϩ44-191/3844737
E-mail: m.r.bryce@durham.ac.uk
Eur. J. Org. Chem. 2000, 51Ϫ60
WILEY-VCH Verlag GmbH, D-69451 Weinheim, 2000
1434Ϫ193X/00/0101Ϫ51 $ 17.50ϩ.50/0
51

M. R. Bryce, T. Finn, A. J. Moore, A. S. Batsanov, J. A. K. Howard
FULL PAPER
Results and Discussion
Synthesis
Our attempts to functionalise 1 via reaction of its mono-
lithio derivative with electrophiles were thwarted by the low
solubility of 1 in suitable solvents at low temperature. To
circumvent this problem, and to ensure that only mono-
lithiation occurred, we synthesised the new trimethyl deriva-
tive 8. For this we required the phosphonate ester reagent
6, which was synthesised from the known iminium salt 3
(81% overall yield) as shown in Scheme 1, using procedures
we have recently optimised for the dimethyl analogue.[13]
Scheme 2. Generation and trapping of species 9
utilises the cyanoethyl protecting group protocol developed
by Becher et al. in the 1,3-dithiole and TTF series.[15] Meth-
Scheme 1. Synthesis of reagent 6
Reaction of compound 7 (readily obtained in multi-gram ylation of thione 16[15a] with methyl triflate gave cation salt
quantities from anthrone)[2b] with the phosphonate anion 17 which was reacted, without purification, with the anion
obtained by deprotonation of reagent 6 using lithium diiso- of anthrone 18 (generated using LDA at room temperature)
propylamide (LDA) in THF at Ϫ78°C afforded compound to afford initially compound 19 (1H-NMR evidence) which
8 in 55% yield (Scheme 2). Deprotonation of 8 using LDA was converted into the desired compound 20 by treatment
in THF at Ϫ78°C, followed by quenching with an excess of with p-toluenesulfonic acid (18% yield, based on thione 16).
D2O gave a quantitative yield of the monodeuterio deriva- The low yield of this reaction was due to the competing
tive of 8 (1H-NMR evidence) confirming the very efficient deprotection of the cyanoethylthio group of 17 and/or 19
generation of lithiated species 9. The results of trapping under these basic conditions. The thiolate anion derived
species 9 with a selection of electrophiles are shown in from 20 was liberated cleanly using BecherЈs conditions (ce-
Scheme 2. The yields of the substituted products 10 and 11 sium hydroxide at room temperature)[15] and trapped in situ
were consistently lower than those for analogous trimethyl- with 6-bromohexan-1-ol to afford the alcohol derivative 21
TTF derivatives[13] (TTF ϭ tetrathiafulvalene): the ma- in 89% yield. Conversion of 21 into its tert-butyldiphenylsi-
jority of unchanged compound 8 was easily recovered. Al- lyl ether derivative 22 (90% yield) and subsequent reaction
dehyde and thioamide derivatives 10 and 11 were obtained with the anion derived from reagent 23[2b] gave compound
repeatedly in only 13Ϫ17% yields, with N,N-dimethylform- 24 (70% yield) desilylation of which (tetrabutylammonium
amide and N-methyl isocyanate as the electrophiles. For the fluoride) gave alcohol derivative 25 (79% yield). The suit-
synthesis of 10, dimethylformamide was preferable to N- ability of compound 25 for further elaboration was estab-
methylformanilide as the formylating reagent, in contrast to lished by reaction with benzoyl chloride in the presence of
the analogous reaction with TTF[14] or trimethyl-TTF.[13] triethylamine which gave the benzoyl ester derivative 26 in
A considerably more efficient trapping of intermediate 9 oc- 50% yield. Thus both routes (Schemes 2 and 3) afford de-
curred with methylchloroformate to yield the methyl ester rivatives of the parent system 1 which contain one reactive
derivative 12 (83% yield). Sulfur insertion into the lithiated substituent suitable for further functionalisation.
species 9 followed by reaction of the transient thiolate anion
During the course of this work we have explored a differ-
with benzoyl chloride gave the thioester derivative 13 (53% ent functional modification to system 1, namely, the attach-
yield). Compound 13 is a convenient shelf-stable precursor ment of a bicyclic 1,3-dithiole moiety. Reaction of com-
of other monofunctionalised derivatives of 8. Debenz- pound 7 with the anion generated from phosphonate ester
oylation of 13 was readily achieved (sodium methoxide, reagent 27[16] gave the expected product 28 (60% yield).
room temperature) and the transient thiolate anion thereby With the aim of synthesising a bis[9,10-bis(1,3-dithiol-2-yli-
generated was trapped efficiently with iodomethane and 6- dene)-9,10-dihydroanthraceno]TTF derivative by a stand-
bromohexanol to yield 14 and 15, respectively (80Ϫ93% ard phosphite-induced coupling reaction,[17] compound 28
yields). The X-ray crystal structures of compounds 12 and was heated in neat triethyl phosphite. However, no coupled
14 are discussed below.
product was obtained; the only isolated product was the
An alternative approach which has yielded a different unexpected compound 29 (50% yield) in which the 1,3-di-
series of derivatives of 1 is shown in Scheme 3. This route thiole-2-thione ring has been transformed into two ethylsul-
52
Eur. J. Org. Chem. 2000, 51Ϫ60

Molecular Saddles, 1
FULL PAPER
Scheme 4. Synthesis of compound 29
Scheme 5. Postulated mechanism for the conversion of 28 into 29
Scheme 3. Synthesis of compounds 24؊26
in accord with their structures. Cyclic voltammetric data
obtained in acetonitrile establish that the redox properties
are only slightly modified by the presence of the substitu-
ents: a predictable[13] trend is that the two-electron oxi-
dation wave[7] is anodically shifted by an electron-with-
drawing substituent on the 1,3-dithiole ring: cf. Eox values
for compound 8 (0.320 V), compound 10 (0.450 V) and
compound 12 (0.425 V). The lowest energy absorption in
the UV/Vis spectra is observed at λmax ϭ 420Ϫ430 nm, and
is essentially unaffected by the substituents. Comparable
data for the parent system 1 and benzo-annulated ana-
fanyl substituents (Scheme 4). The structures of both com-
pounds 28 and 29 were established unequivocally by single
crystal X-ray analysis (see below). The conversion of 28 into
29 under these reaction conditions appears to be an unpre-
cedented reaction of a 1,3-dithiole-2-thione derivative. Re-
actions of trialkylphosphite reagents with cyclic trithiocar-
bonates are generally assumed to proceed via an initial thi-
ophilic addition,[17Ϫ19] although a carbophilic mechanism
has been considered.[17a,b] It is not readily apparent how
a thiophilic addition can explain the formation of 29; we,
therefore, propose initial opening of the 1,3-dithiole-2-
thione ring of 28 induced by carbophilic addition of triethyl
phosphite, to form the zwitterionic intermediate 30 (Scheme
5). Ethylation of 30 then occurs by an O,S transfer of an
ethyl group from triethyl phosphite[19] to yield 31. This is
more likely to be an intermolecular transfer (as shown) than
´
´
logues have been discussed recently by Martın, Ortı et al.
on the basis of theoretical calculations.[6]
X-ray Crystal Structures of Compounds 12, 14, 28,
and 29
The asymmetric unit of 12 comprises one title molecule
an intramolecular process. Generation of a second thiolate (Figure 1a) and one CDCl3 molecule of crystallisation.
anion, and ethylation then gives product 29. Molecule 12 adopts a saddle-like conformation, relieving
Solution electrochemical and UV/Vis spectroscopic data steric repulsion between sulfur atoms and hydrogen atoms
for the new derivatives of the parent system 1 are entirely in peri positions of the anthracene moiety. The latter is
Eur. J. Org. Chem. 2000, 51Ϫ60
53

M. R. Bryce, T. Finn, A. J. Moore, A. S. Batsanov, J. A. K. Howard
FULL PAPER
Figure 1. Molecular structures of 12 (a), 14(b), 28 (c) (Molecule A), and 29 (d), showing the disorder in 29. Atomic displacement ellipsoids
at the 50% probability level.
folded along the C(9)···C(10) axis by a dihedral angle (␾)
Compound 14 exhibits a wider θ angle (86.9°) due to the
of 40.5°. The bis(1,3-dithiole)benzoquinone system is U- more planar dithiole rings, and in spite of more pronounced
shaped through an Јaccumulating bendЈ comprising the folding of the anthracene moiety (␾ ϭ 45.1°). It has the
boat conformation of the central (quinonoid) ring, folding same packing motif as 12, but without any solvent of crys-
of both 1,3-dithiole rings along S···S vectors, and out-of- tallisation. The SMe group is disordered over three posi-
plane tilting of the exocyclic CϭC bonds, all in the same tions, at C(16), C(17), and C(21), with occupancies of 80%,
(inward) direction. Thus the S(1)C(16)C(17)S(2) and 15%, and 5%, respectively. For the former two, the nearly-
S(3)C(22)C(23)S(4) moieties form an acute dihedral angle overlapping positions of the sulfur and the methyl carbon
(θ) of 75.6°. The CϪS bonds in the methoxycarbonyl-sub- atoms, S(5) and C(19), could not be resolved and were re-
stituted dithiole ring of 12 are rather asymmetrical, fined as a single atom; for the latter, the methyl group
˚
S(1)ϪC(16) shortened to 1.743(11) A and S(1)ϪC(15) bound to sulfur was not located. The major position only
˚
lengthened to 1.785(11) A [cf. S(2)ϪC(15) 1.757(10) and is shown in Figure 1b.
˚
S(2)ϪC(17) 1.756(10) A]. Such distortion was observed ear-
In compound 29 (Figure 1d), one of the ethylthio sub-
lier in thiocarbamoylϪTTF and thiocarbamoylϪ- stituents is disordered over two positions, S(6)C(19)C(20)
Me3TTF[20] and can be attributed to a mesomeric effect [i.e. and S(6Ј)C(19Ј)C(20Ј); their occupancies were refined to
a contribution from a canonical form with double S(1)ϭ 61.2 and 38.8(2)%, respectively. The conformation (␾ ϭ
C(16) and C(17)ϭC(19) bonds]. In the other (dimethyl-sub- 40.6, θ ϭ 79.1°) is practically identical with that of 12. The
stituted) dithiole ring of 12, the C(21)ϪS(3) and packing motif is similar to that of 12 and 14, but here the
˚
C(21)ϪS(4) bonds are equivalent [1.767(9) A] as are the ethylthio (rather than the methyl) groups enter the intra-
˚
S(3)ϪC(22) and S(4)ϪC(23) bonds [1.749(10) A]. Crystal molecular cavity of the opposing molecule (Figure 2b).
packing (Figure 2a) shows the motif reported earlier for the
tetra(methylsulfanyl) analogue:[9c] pairs of inversion-related (A and B) and one severely disordered molecule of CDCl3.
molecules engulf each otherЈs dimethyl-substituted dithiole Both molecules and have essentially planar
The asymmetric unit of 28 comprises two title molecules
A
B
moiety. These moieties contact face-to-face, but the in- S(1)C(1)S(2)S(3)C(2)C(3) systems, which form dihedral
˚
terplanar separation of ca. 3.7 A is rather long. CDCl3 mol- angles of 90.4° (A) and 94.1° (B) with the S(6)C(6)C(7)S(7)
ecules occupy cavities between these pairs and are dis- moieties. Folding of the anthracene system along the
ordered.
C(10)···C(11) axis is unequal (35.9° in A vs. 45.2° in B),
54
Eur. J. Org. Chem. 2000, 51Ϫ60

Molecular Saddles, 1
FULL PAPER
Figure 3. Crystal packing of 28, showing intermolecular contacts
˚
S···S (dashes) and S···C (dots) shorter than 3.7 A. The molecules
shown are related to the parent ones (A and B) by symmetry opera-
tions: (i) 1 Ϫ x, 1 Ϫ y, 1 Ϫ z; (ii) 3 Ϫ x, Ϫy, Ϫz; (iii) x ϩ 1, y, z
Ϫ 1; (iv) Ϫx, 1Ϫy, 2Ϫz; (v) 2 Ϫ x, Ϫy, 1 Ϫ z. Disordered CDCl3
molecules are omitted.
˚
(3.29 A each), as well as rather close ones with S(6B) and
˚
S(7B) (3.61 and 3.62 A respectively).
Figure 2. Crystal packing of 12 (a) and 29 (b); the disorder and H
In all four compounds, the two outer rings of the anthra-
cene moiety retain their aromatic character. The exocyclic
CϭC bond lengths [average 1.35(1), 1.366(3), 1.358(6), and
1.361(3), for 12, 14, 28, and 29, respectively] are common
for dithiolene groups.
atoms are not shown.
while folding along the S(4)···S(5) vector is of the opposite
sense (13.7° outward in A, vs. 7.6° inward in B). The crystal
packing of 28 (Figure 3) is rather dissimilar from that of
the other compounds studied herein. Molecule A and its
inversion equivalent engulf each otherЈs dimethyldithiole
ends, as does molecule B and its inversion equivalent. In
each dimer, the dithiole rings overlap in an antiparallel fa-
Conclusion
Two routes have been developed to gain access to deriva-
tives of the 9,10-bis(1,3-dithiol-2-ylidene)-9,10-dihydroant-
hracene system which contain a “reactive handle” suitable
for further chemical elaboration. The availability of these
new derivatives in synthetically-useful quantities paves the
way for the development of this very interesting strained
ring system as a redox-active building block in supramol-
ecular and materials chemistry.
˚
shion, with interplanar separations 3.64 A (A-AЈ) and 3.55
˚
˚
A (BϪBЈ) and shortest C···S contacts of 3.66 A in either
case. These two dimers are oriented in mutually perpendicu-
lar planes and give rise to an unusual three-dimensional
network of intermolecular contacts comparable to (or
shorter than) the standard van der Waals distances[21] S···S
˚
3.60 and C···S 3.61 A. Thus, dimethyldithiole rings of the
A-AЈ dimer are sandwiched between dithiolethione systems
Experimental Section
of two adjacent B molecules (interplanar angle 7°, shortest
˚
1H- and 13C-NMR spectra were obtained on Oxford 200, Varian
Unity 300 and Varian VXR 400S spectrometers operating at
S···S contacts 3.63 A). This tetramer is additionally
strengthened by interactions between molecules A and B:
S(2A)···S(2B) 3.66 A and S(2A)···S(4B) 3.49 A. However, 199.992 (1H) and 50.293 (13C), 299.908 (1H) and 75.420 (13C), and
˚
˚
400.0 (1H) and 100.6 (13C) MHz, respectively. Ϫ Mass spectra were
recorded on a Micromass Autospec spectrometer operating at
no continuous stacks exist in the structure, and the afore-
mentioned BAAЈBЈ stack is ЈunderpinnedЈ at either end by
70 eV. Ϫ Infrared spectra were recorded using a golden gate on a
the thione C(1A)ϭS(1A) bond of another A molecule. This
Paragon 1000 FTIR spectrometer operated from a Grams Analyst
bond is aligned perpendicular to the stacked planes and
1600. Ϫ Electronic absorption spectra were obtained using a PerkinϪ
points towards the midpoint of the C(1B)ϪS(3B) bond
Elmer II UV/Vis spectrophotometer operating with 1 mL quartz
˚
˚
[S(1A)···S(3B) 3.52 A, S(1A)···C(1B) 3.45 A]. On the other
hand, the dimethyldithiole rings of the BϪBЈ dimer are con-
tacted on the outer sides by dithiolethione moieties of ad-
jacent A molecules, in an edge-to-face fashion. Thereby,
cells. Ϫ Melting points were obtained on a Philip Harris melting
point apparatus and are uncorrected. Ϫ All reagents were of com-
mercial quality; solvents were dried using standard procedures. Ϫ
All reactions were performed under an inert atmosphere of argon
S(3A) forms extremely short contacts with C(6B) and C(7B) in pre-dried glassware. Ϫ Cyclic voltammetric data were measured
Eur. J. Org. Chem. 2000, 51Ϫ60 55

M. R. Bryce, T. Finn, A. J. Moore, A. S. Batsanov, J. A. K. Howard
FULL PAPER
with iR compensation using a BAS CV50 electrochemical analyser.
The experiments were carried out with 5 mL of a ca. 10Ϫ4  solu-
tion of the compound in acetonitrile containing 0.1  tetrabu-
mixture was evaporated in vacuo and the residue was purified by
column chromatography on silica gel with hexane/dichloromethane
(2:1 v/v) as eluent to afford 8 as a yellow solid (474 mg, 55%). M.p.
tylammonium hexafluorophosphate (Fluka, puriss, electrochemical 288Ϫ290°C (from hexane/dichloromethane). Ϫ 1H NMR (CDCl3):
grade) as the supporting electrolyte, at scan rate 100 mV sϪ1. The
oxidation potentials (which represent a two-electron process) were
measured versus a platinum wire quasi-reference electrode and cor-
rected versus decamethylferrocene/decamethylferroceniumϩ by ad-
ding decamethylferrocene to the studied solution after the experi-
ment, and referenced versus Ag/AgCl.[22]
δ ϭ 2.02 (s, 6 H), 2.14 (s, 3 H), 5.93 (s, 1 H), 7.36 (m, 4 H), 7.75
(m, 4 H). Ϫ 13C NMR (CDCl3): δ ϭ 13.8, 15.9, 111.0, 120.8, 121.2,
122.1, 125.1, 125.3, 125.7, 129.3, 133.0, 135.1, 135.2, 136.0. Ϫ UV
(MeCN): λmax (lg ε) ϭ 360 nm (4.18), 430 (4.43). Ϫ CV: Eox
ϭ
0.320 V. Ϫ MS (EI); m/z (%): 422 (37) [Mϩ], 149 (50), 84 (100). Ϫ
HRMS: C23H18S4 (422.6): calcd. 422.0359; found 422.0359.
4-Methyl-2-piperidino-1,3-dithiole (4): To a stirred suspension of
salt 3[23] (75.0 g, 217 mmol) in dry tetrahydrofuran/2-propanol (1:1
v/v, 1.0 L) at 0°C, finely-ground sodium borohydride (37.8 g, 1.0
mol) was added in portions over ca. 6 h. The reaction was then
maintained at 0°C for a further 2 h, whereupon it was allowed to
warm to room temperature and stirred for a further 40 h. After
concentrating to ca. 150 mL, water (500 mL) was added cautiously
and the mixture extracted with diethyl ether (4 ϫ 125 mL). The
combined extracts were washed with water (3 ϫ 125 mL), dried
(MgSO4) and evaporated in vacuo to afford compound 4 (40.6 g,
93%) as a yellow oil of high purity (1H-NMR analysis) suitable for
use in the next step without further purification. Ϫ 1H NMR
(CDCl3): δ ϭ 1.41 (m, 2 H), 1.53 (m, 4 H), 2.02 (s, 3 H), 2.49 (t,
J ϭ 5.2 Hz, 4 H), 5.72 (s, 1 H), 6.18 (s, 1 H).
9-(4,5-Dimethyl-1,3-dithiol-2-ylidene)-10-(4-formyl-5-methyl-1,3-
dithiol-2-ylidene)-9,10-dihydroanthracene (10): Into a solution of 8
(159 mg, 0.376 mmol) in dry tetrahydrofuran (50 mL) at Ϫ78°C,
was added lithium diisopropylamide (0.26 mL of 1.5  solution in
cyclohexane, 0.39 mmol). The reaction was stirred for 3 h at Ϫ78°C
to give a yellow solution containing anion 9. N,N-Dimethylforma-
mide (0.055 mL, 0.71 mmol) was then added and the reaction was
stirred overnight at 20°C. The reaction mixture was acidified with
HCl (1 ), and then extracted into dichloromethane (3 ϫ 100 mL).
The organic layer was separated and dried (MgSO4) and evapo-
rated in vacuo and the residue was purified by column chromatog-
raphy on silica gel with hexane/dichloromethane (2:1 v/v) as the
eluent to afford 10 as an orange solid (22 mg, 13%). M.p. 160°C
1
(dec.). Ϫ H NMR (CDCl3): δ ϭ 1.93 (s, 6 H), 2.40 (s, 3 H), 7.26
(m, 4 H), 7.64 (m, 4 H), 9.67 (s, 1 H). Ϫ IR (powder): ν˜ ϭ 1635
(CϭO) cmϪ1. Ϫ UV (MeCN): λmax (lg ε) ϭ 358 nm (3.90), 422
(4.08). Ϫ CV: Eox ϭ 0.450 V. Ϫ MS (EI); m/z (%): 450 (100) [Mϩ],
306 (63), 252 (31). Ϫ HRMS: C24H18OS4 (450.6): calcd. 450.0308;
found 450.0308.
4-Methyl-1,3-dithiolium Iodide (5): To an ice-cooled, stirred solu-
tion of acetic anhydride (260 mL) was cautiously added hexafluoro-
phosphoric acid (60 wt% in water, 115.0 g, 0.788 mol) over ca. 2 h.
(CAUTION: vigorous exothermic reaction!). To the ice-cooled
solution of anhydrous hexafluorophosphoric acid thus formed, was
added dropwise over ca. 0.5 h a solution of compound 4 (38.0 g,
189 mmol) in dry diethyl ether (250 mL), precipitating immediately
the salt 5. The mixture was diluted with dry diethyl ether (250 mL),
stirred for a further 0.5 h, and the product was collected by fil-
tration and washed with diethyl ether (125 mL) affording hexa-
fluorophosphate salt 5 as an off-white solid. Purification was
achieved by anion exchange to the iodide salt. To a stirred solution
of the hexafluorophosphate salt in anhydrous acetone (125 mL) at
20°C was added a solution of sodium iodide (28.3 g, 189 mmol) in
anhydrous acetone (50 mL) to precipitate iodide salt 5 as a bright
yellow solid, which was collected by filtration and washed initially
with cold anhydrous acetone (25 mL) and then anhydrous diethyl
9-(4,5-Dimethyl-1,3-dithiol-2-ylidene)-10-(5-methyl-4-methylthio-
carbamoyl-1,3-dithiol-2-ylidene)-9,10-dihydroanthracene (11): Into a
solution of 8 (102 mg, 0.241 mmol) in dry tetrahydrofuran (50 mL)
at Ϫ78°C was added lithium diisopropylamide (0.17 mL of 1.5 
solution in cyclohexane, 2.55 mmol). The reaction was stirred for
3 h, then methyl isothiocyanate (0.10 mL, 1.46 mmol) was added
and the reaction was stirred overnight at 20°C. Workup and purifi-
cation as described for 10, gave 11 as an orange solid (20 mg, 17%).
1
M.p. 197Ϫ200°C. Ϫ H NMR (CDCl3): δ ϭ 1.92 (s, 6 H), 2.03 (s,
3 H), 2.99 (d, 3 H, J ϭ 4.8 Hz), 7.30 (m, 4 H), 7.52 (m, 2 H), 7.66
(m, 2 H), (NH not observed). Ϫ 13C NMR (CDCl3): δ ϭ 13.1,
15.0, 32.6, 120.9, 125.3, 125.3, 125.5, 125.6, 125.8, 125.9, 126.2,
127.3, 129.3, 131.1, 134.0, 134.3, 134.4, 135.1. Ϫ UV (MeCN): λmax
(lg ε) ϭ 362 nm (4.11), 430 (4.32). Ϫ CV: Eox ϭ 0.365 V. Ϫ MS
(EI); m/z (%): 495 (100) [Mϩ], 447 (36), 350 (40). Ϫ HRMS:
C25H21NS5 (495.8): calcd. 495.0362; found 495.0362.
1
ether (100 mL) to afford 40.6 g (88%) of 5, m.p. 98Ϫ101°C. Ϫ H
NMR [(CD3)2SO]: δ ϭ 2.91 (s, 3 H), 9.09 (s, 1 H), 11.47 (s, 1H).
Ϫ This salt can be stored under argon for 1 month or in a sealed
ampule for several months without any observable decomposition.
Dimethyl (4-Methyl-1,3-dithiol-2-yl)phosphonate (6): To a stirred
suspension of salt 5 (500 mg, 2.05 mmol) in dry acetonitrile
(100 mL) at 20°C, was added trimethyl phosphite (0.28 mL,
2.37 mmol) and the mixture was stirred for 1 h. The solvent was
evaporated in vacuo to afford compound 6 (460 mg, 99%) as a light
brown oil of high purity (1H-NMR analysis) suitable for use in the
next step without further purification. Ϫ H NMR (CDCl3): δ ϭ
1.95 (s, 3 H), 3.89 (d, J ϭ 10.5 Hz, 6 H), 4.97 (d, J ϭ 4.2 Hz, 1 H),
5.53 (s, 1 H ).
9-(4,5-Dimethyl-1,3-dithiol-2-ylidene)-10-(4-methoxycarbonyl-5-
methyl-1,3-dithiol-2-ylidene)-9,10-dihydroanthracene (12): Into
a
solution of 8 (504 mg, 1.19 mmol) in dry tetrahydrofuran (150 mL)
at Ϫ78°C was added lithium diisopropylamide (0.87 mL of 1.5 
solution in cyclohexane, 1.30 mmol) over a period of 15 min. The
reaction was stirred for 3 h, then methyl chloroformate (0.27 mL,
3.54 mmol) was added over 15 min and the reaction was stirred
overnight at 20°C. Workup and purification as described for 10,
with hexane/dichloromethane (3:1 v/v) as eluent, afforded 12 as a
1
9-(4,5-Dimethyl-1,3-dithiol-2-ylidene)-10-(4-methyl-1,3-dithiol-2- yellow solid (475 mg, 83%). M.p. 218Ϫ220°C. Ϫ 1H NMR
ylidene)-9,10-dihydroanthracene (8): Into a solution of reagent 6
(465 mg, 2.05 mmol) in dry tetrahydrofuran (150 mL) at Ϫ78°C,
was added lithium diisopropylamide (1.5 mL of 1.5  solution in
cyclohexane, 2.25 mmol) over a period of 15 min. The reaction was
stirred for 3 h at Ϫ78°C until a pale cloudy solution formed. Then
(CDCl3): δ ϭ 1.83 (s, 6 H), 2.28 (s, 3 H), 3.69 (s, 3 H), 7.20 (m, 4
H), 7.51 (m, 2 H), 7.57 (m, 2 H). Ϫ 13C NMR (CDCl3): δ ϭ 13.4,
15.7, 52.4, 117.2, 121.0, 121.2, 123.7, 125.4, 125.5, 125.7, 125.9,
126.1, 126.4, 129.5, 134.2, 134.8, 135.5, 145.8, 160.9. Ϫ IR (pow-
der): ν˜ ϭ 1714 (CϭO) cmϪ1. Ϫ UV (MeCN): λmax (lg ε) ϭ 358 nm
compound 7[2b] (725 mg, 2.25 mmol) was added portionwise over (4.18), 426 (4.40). Ϫ CV: Eox ϭ 0.425 V. Ϫ MS (EI); m/z (%): 480
15 min. The reaction was stirred overnight at 20°C. The reaction (100) [Mϩ], 306 (37), 175 (35). Ϫ C25H20O2S4 (480.0): calcd. C
56
Eur. J. Org. Chem. 2000, 51Ϫ60

Molecular Saddles, 1
FULL PAPER
62.47, H 4.19; found C 62.40, H 4.12. Ϫ Crystals for X-ray analysis
were grown from CDCl3.
(2-Cyanoethylsulfanyl)-2-methylsulfanyl-4-5-methylthio-1,3-di-
thiolium Trifluoromethylsulfonate (17): Into a solution of thione
16[15a] (1.029 g, 4.10 mmol) in dry dichloromethane (100 mL) at
20°C, was added methyl trifluoromethylsulfonate (0.90 mL,
7.97 mmol). The reaction was left for 1 h until a dark yellow solu-
tion formed. The reaction mixture was concentrated in vacuo to
ca. 10 mL and the resulting suspension washed with dry diethyl
ether (50 mL) which was then decanted off and discarded. The re-
action mixture was then evaporated in vacuo affording 17 as an
unstable red oil which was quickly used without further purifi-
cation. Ϫ 1H NMR (CDCl3): δ ϭ 2.85 (s, 3 H), 2.92 (t, J ϭ 6.6 Hz,
2 H), 3.22 (s, 3 H), 3.33 (t, J ϭ 6.4 Hz, 2 H).
9-(4-Benzoylsulfanyl-5-methyl-1,3-dithiol-2-ylidene)-10-(4,5-di-
methyl-1,3-dithiol-2-ylidene)-9,10-dihydroanthracene (13): Into
a
solution of compound 8 (199 mg, 0.471 mmol) in dry tetrahydrofu-
ran (50 mL) at Ϫ78°C was added lithium diisopropylamide
(0.38 mL of 1.5  solution in cyclohexane, 0.57 mmol) over a per-
iod of 15 min. The reaction was stirred for 3 h at Ϫ78°C. Finely-
powdered elemental sulfur (78 mg, 2.37 mmol) was added and the
reaction was stirred for a further 2 h at Ϫ78°C before benzoyl chlo-
ride (0.275 mL, 2.37 mmol) was added. The colour of the solution
turned darker yellow, and the reaction was stirred overnight at
20°C. Workup and purification as described for 12, gave 13 as a
yellow solid (138 mg, 53%). M.p. 160°C (dec.). Ϫ 1H NMR
(CDCl3): δ ϭ 1.84 (s, 6 H), 1.97 (s, 3 H), 7.19 (m, 4 H), 7.39 (t,
J ϭ 7.5 Hz, 2 H), 7.53 (m, 5 H), 7.86 (d, J ϭ 7.9 Hz, 2 H). Ϫ 13C
NMR (CDCl3): δ ϭ 13.1, 14.9, 108.1, 120.8, 120.9, 121.0, 123.0,
125.1, 125.2, 125.4, 125.5, 125.7, 125.8, 126.0, 126.1, 126.8, 126.9,
131.3, 133.9, 134.2, 134.7, 134.9, 135.3, 135.4, 135.7, 139.3, 187.7.
Ϫ IR (powder): ν˜ ϭ 1737 (CϭO) cmϪ1. Ϫ UV (MeCN): λmax (lg
ε) ϭ 364 nm (4.16), 430 (4.38). Ϫ CV: Eox ϭ 0.420 V. Ϫ MS (EI);
m/z (%): 558 (5) [Mϩ], 84 (100), 64 (71). Ϫ C30H22OS5 (558.0):
calcd. C 64.48, H 3.97; found C 64.29, H 4.25.
10-[4-(2-Cyanoethylsulfanyl)-5-methylsulfanyl-1,3-dithiol-2-ylidene]-
anthracene-9-(10H)-one (20): Into a solution of anthrone 18
(773 mg, 3.98 mmol) in dry 2-propanol (50 mL) at 20°C was added
lithium diisopropylamide (2.65 mL, of 1.5  solution in cyclohex-
ane, 3.98 mmol). The reaction was stirred for 15 min until a bright
yellow solution formed. Then salt 17 (1.653 g, 3.98 mmol) in dry
tetrahydrofuran (50 mL) was added and the reaction mixture was
stirred overnight. The mixture was evaporated in vacuo and the
residue was purified by column chromatography on silica gel with
hexane/dichloromethane (1:1 v/v) as the eluent to afford crude
compound 19 as a red solid. [1H NMR (CDCl3): δ ϭ 2.00 (s, 3 H),
2.26 (s, 3 H), 2.47 (m, 2 H), 2.73 (m, 2 H), 4.91 (s, 1 H), 7.51 (m,
4 H), 7.69 (m, 2 H), 8.15 (m, 2 H)]. This solid (398 mg, 0.889 mmol)
was dissolved in dry toluene (100 mL) at 20°C and p-toluene sul-
fonic acid (100 mg, 0.526 mmol) was added. The reaction mixture
was refluxed for 16 h to give a dark red solution. The mixture was
evaporated in vacuo and the residue purified by column chroma-
tography on silica gel with dichloromethane as eluent to afford 20
9-(4,5-Dimethyl-1,3-dithiol-2-ylidene)-10-(4-methylsulfanyl-5-
methyl-1,3-dithiol-2-ylidene)-9,10-dihydroanthracene (14): Into
a
solution of compound 13 (97 mg, 0.174 mmol) in dry tetrahydrofu-
ran (35 mL) at 20°C was added sodium methoxide (0.39 mL of
0.5  solution in methanol, 0.195 mmol). The reaction was stirred
for 1 h until a dark red solution formed. Then iodomethane was
added (0.10 mL, 1.61 mmol) and the reaction was stirred overnight
at 20°C. The reaction mixture was evaporated in vacuo and the
residue was purified by column chromatography on silica gel with
hexane/dichloromethane (2:1 v/v) as eluent to afford 14 as a yellow
1
as a red solid (293 mg, 18% based on 16). M.p. 142Ϫ145°C. Ϫ H
NMR (CDCl3): δ ϭ 2.04 (s, 3 H), 2.24 (t, J ϭ 6.8 Hz, 2 H), 2.58
(t, J ϭ 6.8 Hz, 2 H), 7.04 (t, J ϭ 7.8 Hz, 2 H), 7.26 (m, 4 H), 7.85
(d, J ϭ 7.4 Hz, 2 H). Ϫ 13C NMR (CDCl3): δ ϭ 18.7, 18.1, 31.3,
117.4, 119.6, 120.3, 126.1, 127.2, 127.3, 130.7, 131.9, 134.1, 138.2,
138.4, 183.4. Ϫ IR (powder): ν˜ ϭ 1635 (CϭO) cmϪ1. Ϫ MS (EI);
m/z (%): 425 (61) [Mϩ], 236 (100), 91 (66). Ϫ C21H15NOS4 (425.6):
calcd. C 59.27, H 3.55; found C 59.51, H 3.70.
1
solid (65 mg, 80%). M.p. 220°C (dec.). Ϫ H NMR (CDCl3): δ ϭ
1.86 (s, 6 H), 2.03 (s, 3 H), 2.20 (s, 3 H), 7.20 (m, 4 H), 7.51 (m, 2
H), 7.59 (m, 2 H). Ϫ 13C NMR (CDCl3): δ ϭ 13.1, 14.5, 19.3,
118.3, 120.8, 125.2, 125.3, 125.4, 125.6, 125.8, 125.9, 132.0, 134.8,
135.0, 135.2, 197.9. Ϫ UV (MeCN): λmax (lg ε) ϭ 360 nm (3.89),
432 (4.38). Ϫ CV: Eox ϭ 0.355 V. Ϫ MS (EI); m/z (%): 468 (100)
[Mϩ], 350 (50), 57 (60) Ϫ C24H20S5 (468.0): calcd. C 61.50, H 4.30;
found C 61.30, H 4.26. Ϫ Crystals for X-ray analysis were grown
from CS2/CH2Cl2.
10-[4-(6-Hydroxyhexylsulfanyl)-5-methylsulfanyl-1,3-dithiol-2-
ylidene]anthracene-9-(10H)-one (21): Into a solution of 20 (200 mg,
0.471 mmol) in dry tetrahydrofuran (50 mL) at 20°C was added
cesium hydroxide monohydrate (94 mg, 0.528 mmol). The reaction
was stirred for 1 h until a dark red solution formed. 6-Bromohexan-
1-ol (0.2 mL, 1.53 mmol) was added and the reaction was stirred
overnight at 20 °C then evaporated in vacuo and excess 6-bromo-
hexan-1-ol was removed by Kügelrohr distillation at 140°C at ca.
0.1 Torr, and the distillate was discarded. The residue was purified
by column chromatography on silica gel with hexane/dichlorometh-
ane (1:1 v/v) as eluent to afford 21 as a red oil (198 mg, 89%). Ϫ
1H NMR (CDCl3): δ ϭ 1.47 (m, 8 H), 2.41 (s, 3 H), 2.79 (t, J ϭ
7.2 Hz, 2 H), 3.60 (t, J ϭ 7.2 Hz, 2 H), 7.44 (t, J ϭ 7.8 Hz, 2 H),
7.65 (t, J ϭ 7.8 Hz, 2 H), 7.77 (d, J ϭ 7.8 Hz, 2 H), 8.26 (d, J ϭ
7.8 Hz, 2 H). Ϫ 13C NMR (CDCl3): δ ϭ 19.2, 25.1, 28.0, 29.4,
32.4, 36.2, 62.6, 119.0, 125.1, 126.1, 127.1, 127.6, 129.0, 130.5,
9-(4,5-Dimethyl-1,3-dithiol-2-ylidene)-10-[4-(6-hydroxyhexyl-
sulfanyl)-5-methyl-1,3-dithiol-2-ylidene]-9,10-dihydroanthracene
(15): Into a solution of compound 13 (100 mg, 0.179 mmol) in dry
tetrahydrofuran (50 mL) at 20°C was added sodium methoxide
(0.39 mL of 0.5  solution in methanol, 0.195 mmol). The reaction
was left for 1 h before 6-bromohexan-1-ol was added (0.07 mL,
0.535 mmol), and the reaction was stirred overnight at 20°C. The
reaction mixture was evaporated in vacuo and excess 6-bromo-
hexan-1-ol was removed by Kügelrohr distillation at 140°C at ca.
0.1 Torr, and the distillate was discarded. The residue was purified
by column chromatography on silica gel with ethyl acetate/di-
chloromethane (1:4 v/v) as eluent to afford 15 as a red oil (93 mg,
93%). Ϫ 1H NMR (CDCl3): δ ϭ 1.37 (m, 4 H), 1.55 (m, 4 H), 1.92
(s, 6 H), 2.09 (s, 3 H), 2.66 (m, 2 H), 3.60 (t, J ϭ 6.6 Hz, 2 H), 7.26
(m, 4 H), 7.58 (m, 2 H), 7.64 (m, 2 H), (OH not observed). Ϫ 13C
NMR (CDCl3): δ ϭ 13.1, 14.7, 25.2, 28.1, 28.9, 29.6, 32.5, 35.9,
62.8, 117.1, 120.8, 122.3, 125.2, 125.3, 125.6, 125.8, 125.8, 125.9,
131.8, 138.5, 140.3, 183.4. Ϫ IR (Powder): ν˜ ϭ 1649 (CϭO) cmϪ1
.
Ϫ MS (EI); m/z (%): 472 (100) [Mϩ], 236 (58), 55 (79). Ϫ HRMS:
C24H24O2S4 (472.7): calcd. 472.0659; found 472.0644.
10-[4-(6-tert-Butyldiphenylsilyloxyhexylsulfanyl)-5-methylsulfanyl-
131.3, 133.0, 133.1, 134.8, 135.0, 135.2. Ϫ UV (MeCN): λmax (lg 1,3-dithiol-2-ylidene]anthracene-9-(10H)-one (22): Into a solution of
ε) ϭ 366 nm (4.14), 432 (4.39). Ϫ CV: Eox ϭ 0.380 V. Ϫ MS (EI);
compound 21 (305 mg, 0.646 mmol) in dry dimethylformamide
m/z (%): 554 (100) [Mϩ], 350 (76), 220 (31). Ϫ HRMS: C29H30OS5 (50 mL) was added tert-butylchlorodiphenylsilane (0.18 mL,
(554.9): calcd. 554.0985; found 554.0985.
0.692 mmol) and imidazole (345 mg, 5.07 mmol). The reaction was
Eur. J. Org. Chem. 2000, 51Ϫ60
57

M. R. Bryce, T. Finn, A. J. Moore, A. S. Batsanov, J. A. K. Howard
FULL PAPER
stirred overnight at 20°C and then evaporated in vacuo and the
residue was purified by column chromatography on silica gel with
0.167 mmol) in dry tetrahydrofuran (50 mL) was added tetrabu-
tylammonium fluoride (0.5 mL of 1.0  solution in water,
0.5 mmol). After stirring for 1 h at 20°C a dark red solution had
hexane/dichloromethane (1:1 v/v) as eluent to afford 22 as a red oil
1
(413 mg, 90%). Ϫ H NMR (CDCl3): δ ϭ 1.06 (s, 9 H), 1.37 (m, 4 formed. The reaction mixture was stirred at 20°C overnight and
H), 1.55 (m, 4 H), 2.40 (s, 3 H), 2.79 (t, J ϭ 7.6 Hz, 2 H) 3.65 (t, then evaporated in vacuo and the residue was purified by column
J ϭ 6.4 Hz, 2 H), 7.42 (m, 8 H), 7.67 (m, 6 H), 7.79 (m, 2 H), 8.29 chromatography on silica gel with dichloromethane as eluent to
(d, J ϭ 7.6 Hz, 2 H). Ϫ 13C NMR (CDCl3): δ ϭ 19.5, 25.6, 27.2, afford 25 as a yellow oil (77 mg, 79%). Ϫ H NMR (CDCl3): δ ϭ
1
28.4, 29.8, 32.6, 36.7, 64.0, 119.3, 125.6, 126.5, 127.5, 127.9, 129.3,
1.39 ( m, 4 H), 1.56 (m, 4 H), 1.93 (s, 6 H), 2.37 (s, 3 H), 2.77 (m,
129.8, 130.9, 130.9, 132.1, 134.3, 135.8, 138.9, 140.7, 183.7. IR 2 H), 3.61 (t, J ϭ 6.5 Hz, 2 H), 4.35 (t, J ϭ 7.0 Hz, 1 H), 7.28 (m,
(Powder): ν˜ ϭ 1653 (CϭO) cmϪ1. Ϫ MS (EI); m/z (%): 710, (100)
[Mϩ], 653 (99), 135 (79). Ϫ HRMS: C40H42O2S4Si (711.1): calcd.
710.1904; found 710.1902.
4 H), 7.52 (m, 2 H), 7.66 (m, 2 H). Ϫ 13C NMR (CDCl3): δ ϭ
13.1, 19.1, 25.2, 28.1, 29.6, 32.5, 36.0, 60.4, 62.8, 120.9, 123.8,
124.0, 125.3, 125.7, 126.1, 127.7, 130.2, 133.5, 134.5, 135.2. Ϫ MS
(EI); m/z (%): 586 (21) [Mϩ], 350 (100), 220 (100). Ϫ HRMS:
C29H30OS6 (586.9): calcd. 586.0621; found 586.0634.
9-[4-(6-tert-Butyldiphenylsilyloxyhexylsulfanyl)-5-methylsulfanyl-
1,3-dithiol-2-ylidene]-10-(4,5-dimethyl-1,3-dithiol-2-ylidene)-9,10-
dihydroanthracene (24): Into
a
solution of 23[2b] (117 mg,
9-[4-(6-Benzoyloxyhexylsulfanyl)-5-methylsulfanyl-1,3-dithiol-2-
ylidene]-10-(4,5-dimethyl-1,3-dithiol-2-ylidene)-9,10-dihydro-
0.488 mmol) in dry tetrahydrofuran (150 mL) at Ϫ78°C was added
lithium diisopropylamide (0.34 mL of 1.5  solution in cyclohex-
ane, 0.506 mmol) over a period of 15 min. The reaction was stirred
for 3 h until a pale cloudy solution formed. Then compound 22
(171 mg, 0.241 mmol) was added over 15 min and the reaction was
stirred overnight at 20°C and then evaporated in vacuo and the
residue purified by column chromatography on silica gel with hex-
ane/dichloromethane (2:1 v/v) as eluent to afford 24 as a yellow oil
anthracene (26): Into
a solution of compound 25 (74 mg,
0.127 mmol) in dry dichloromethane (50 mL) was added triethyl-
amine (1 mL, excess) and benzoyl chloride (0.20 mL, 1.72 mmol).
The reaction was stirred overnight at 20 °C and then evaporated in
vacuo and the residue purified initially by column chromatography
on silica gel with hexane/dichloromethane (1:1 v/v) as eluent, and
then further purified by column chromatography on silica gel with
acetone/hexane (1:3 v/v) as eluent to afford 26 as a yellow oil
1
(138 mg, 70%). Ϫ H NMR (CDCl3): δ ϭ 1.05 (s, 9 H), 1.36 (m, 4
H), 1.56 (m, 4 H), 1.93 (s, 6 H), 2.36 (s, 3 H), 2.76 (m, 2 H), 3.65
(t, J ϭ 6.6 Hz, 2 H), 7.30 (m, 4 H), 7.41 (m, 6 H), 7.54 (m, 2 H),
7.66 (m, 6 H). Ϫ 13C NMR (CDCl3): δ ϭ 13.1, 19.2, 25.3, 26.9,
28.1, 29.6, 31.6, 32.3, 34.6, 36.2, 63.7, 120.8, 120.9, 123.7, 124.2,
125.8, 126.1, 127.6, 129.5, 130.4, 133.5, 134.0, 134.6, 135.2, 135.5.
Ϫ MS (EI); m/z (%): 824 (100) [Mϩ], 350 (89), 220 (66). Ϫ HRMS:
C45H48OS6Si (825.3): calcd. 824.1900; found 824.1900.
1
(44 mg, 50%). Ϫ H NMR (CDCl3): δ ϭ 1.38 (m, 4 H), 1.56 (m, 2
H), 1.67 (m, 2 H), 1.84 (s, 6 H), 2.28 (s, 3 H), 2.70 (m, 2 H), 4.21
(t, J ϭ 6.5 Hz, 2 H), 7.20 (m, 4 H), 7.35 (t, J ϭ 8.0 Hz, 2 H), 7.45
(m, 3 H), 7.59 (m, 2 H), 7.95 (d, J ϭ 8.5 Hz, 2 H). 13C NMR
(CDCl3): δ ϭ 13.1, 19.1, 25.6, 28.0, 28.5, 29.5, 36.0, 64.9, 120.8,
120.9, 123.8, 123.9, 125.3, 125.3, 125.8, 126.1, 127.9, 128.3, 129.5,
130.2, 130.4, 132.8, 133.5, 134.6, 135.2, 166.6. Ϫ UV (MeCN): λmax
9-(4,5-Dimethyl-1,3-dithiol-2-ylidene)-10-[4-(6-hydroxyhexyl- (lg ε) ϭ 366 nm (4.09), 434 (4.33). Ϫ CV: Eox ϭ 0.375 V. ؊ MS
sulfanyl)-5-methylsulfanyl-1,3-dithiol-2-ylidene]-9,10-dihydro-
(DCI); m/z (%): 691 (49) [Mϩϩ1], 322 (100), 105 (63). Ϫ HRMS:
anthracene (25): Into
a
solution of compound 24 (137 mg,
C36H34O2S6 (691.0): calcd. 690.0985; found 690.0988.
Table 1. Crystal data
Compound
12
14
28
29
Formula
C25H20O2S4 · CDCl3
C24H20S5
468.7
C23H14S7 · 0.5 CDCl3
C26H24S6
528.81
150
Molecular mass
T [K]
601.02
293
575.44
150
120
Crystal system
Space group
triclinic
triclinic
triclinic
triclinic
¯
¯
¯
¯
P1 (No. 2)
P1 (No. 2)
P1 (No. 2)
P1 (No. 2)
˚
a [A]
9.656(1)
11.290(1)
13.238(1)
94.27(1)
106.21(1)
96.56(1)
1368.1(2)
2
9.077(1)
10.287(1)
12.014(1)
84.79(1)
87.92(1)
76.02(1)
1084.0(2)
2
11.682(1)
13.483(1)
17.716(1)
79.481(4)
71.432(4)
69.885(4)
2475.3(2)
4
9.673(1)
9.793(1)
13.159(1)
98.34(1)
90.36(1)
93.09(1)
1231.4(2)
2
˚
b [A]
˚
c [A]
α [°]
β [°]
γ [°]
3
˚
U [A ]
Z
µ(Mo-Kα) [mmϪ1
]
0.66
0.54
0.81
0.57
Dx [g cmϪ3
2θmax [°]
]
1.46
1.44
1.54
1.43
50
55
61
55
Crystal size [mm]
0.48ϫ0.26ϫ0.02
8191
0.30ϫ0.10ϫ0.08
7879
0.25ϫ0.20ϫ0.06
19705
0.48ϫ0.24ϫ0.04
8965
Reflections measured
Unique reflections
Absorption correction
Transmission min, max
Rint
4809
N/A
4910
12778
5532
Integration
0.885, 0.966
0.028
Semi-empirical
0.786, 0.908
0.031
Integration
0.825, 0.979
0.022
0.757, 0.983
0.166
Reflections with IՆ2σ(I)
Refined variables
R[F2Ն2σ(F2)]
1835
3887
8252
4751
339
306
653
377
0.102
0.042
0.067
0.042
Goodness-of-fit
1.00
1.03
1.13
1.17
wR(F2), all data
0.347
0.101
0.175
0.113
Ϫ3
˚
∆ρmax,min [eA
]
0.85, Ϫ0.59
0.42, Ϫ0.31
1.14, Ϫ0.95
0.40, Ϫ0.35
58
Eur. J. Org. Chem. 2000, 51Ϫ60

Molecular Saddles, 1
FULL PAPER
9-(4,5-Dimethyl-1,3-dithiol-2-ylidene)-10-[(5-thio-1,3-dithiolo[4,5-
d][1,3]dithiol-2-ylidene]-9,10-dihydroanthracene (28): Into a solution
of 27[16] (216 mg, 0.63 mmol) in dry tetrahydrofuran (50 mL) at
Ϫ78°C, was added lithium diisopropylamide (0.46 mL of 1.5 
solution in cyclohexane, 0.69 mmol) over a period of 15 min. The
mixture was stirred at Ϫ78°C for 3 h until a dark red solution
formed. Then compound 7 (198 mg, 0.61 mmol) was added over
15 min and the mixture was stirred overnight at 20 °C. The reaction
mixture was evaporated in vacuo and the residue purified by col-
umn chromatography on silica gel with hexane/dichloromethane
(2:1 v/v) as eluent to afford 28 as a red solid (189 mg, 60%). M.p.
Acknowledgments
We are grateful to the EPSRC for funding.
[1]
[1a] Z. Yoshida, T. Sugimoto, Angew. Chem. Int. Ed. Engl. 1988,
[1b]
27, 1573Ϫ1157. Ϫ
T. Sugimoto, H. Awaji, I. Sugimoto, Y.
Misaki, T. Kawase, S. Yoneda, Z. Yoshida, Chem. Mater. 1989,
1, 535Ϫ547. Ϫ [1c] A. Khanous, A. Gorgues, M. Jubault, Tetra-
[1d]
hedron Lett. 1990, 31, 7311Ϫ7314. Ϫ
A. J. Moore, M. R.
Bryce, D. J. Ando, M. B. Hursthouse, J. Chem. Soc., Chem.
[1e]
Commun. 1991, 320Ϫ321. Ϫ
T. K. Hansen, M. V. Lakshmi-
kantham, M. P. Cava, R. M. Metzger, J. Becher, J. Org. Chem.
1991, 56, 2720Ϫ2722. Ϫ [1f] Y. Misaki, T. Ohta, N. Higuchi, H.
1
246Ϫ249°C. Ϫ H NMR (CDCl3): δ ϭ 1.93 (s, 6 H), 7.27 (t, J ϭ
Fujiwara, T. Yamabe, T. Mori, H. Mori, S. Tanaka, J. Mater.
7.6 Hz, 2 H), 7.35 (t, J ϭ 7.6 Hz, 2 H), 7.42 (d, J ϭ 7.6 Hz, 2 H),
7.71 (d, J ϭ 7.6 Hz, 2 H). Ϫ 13C NMR (CDCl3): δ ϭ 13.1, 29.7,
119.8, 121.0, 122.3, 125.2, 125.5, 125.8, 127.1, 128.8, 130.8, 133.7,
135.2, 135.9, 211.7. Ϫ CV: Eox ϭ 0.430 V. Ϫ MS (EI); m/z (%): 514
(82) [Mϩ], 350 (100), 220 (82). Ϫ C23H14S7 (514.8): calcd. C 53.66,
H 2.74; found C 53.80, H 3.19. Ϫ Crystals for X-ray analysis were
grown from CDCl3.
[1g]
Chem. 1995, 10, 1571Ϫ1579. Ϫ
M. R. Bryce, A. J. Moore,
B. K. Tanner, R. Whitehead, W. Clegg, F. Gerson, A. Lam-
[1h]
precht, S. Pfenninger, Chem. Mater. 1996, 8, 1182Ϫ1188. Ϫ
A. J. Moore, M. R. Bryce, A. S. Batsanov, A. Green, J. A. K.
´
Howard, M. A. McKervey, P. McGuigan, I. Ledoux, E. Ortı,
R. Viruela, P. M. Viruela, B. Tarbit, J. Mater. Chem. 1998, 8,
1173Ϫ1184. Ϫ [1i] Y. Yamashita, M. Tomura, M. B. Zaman, M.
Imaeda, Chem. Commun. 1998, 1657Ϫ1658.
[2] [2a]
Y. Yamashita, Y. Kobayashi, T. Miyashi, Angew. Chem. Int.
Ed. Engl. 1989, 28, 1052Ϫ1053. Ϫ [2b] A. J. Moore, M. R. Bryce,
J. Chem. Soc., Perkin Trans. 1 1991, 157Ϫ168.
9-(4,5-Diethylsulfanyl-1,3-dithiol-2-ylidene)-10-(4,5-dimethyl-1,3-
dithiol-2-ylidene)-9,10-dihydroanthracene (29): A solution of 28
(102 mg, 0.20 mmol) in triethylphosphite (10 mL) was heated at re-
flux for 3 h to give a pale orange solution. The reaction mixture
was evaporated in vacuo and the residue was purified by column
chromatography on silica gel with hexane/dichloromethane (2:1 v/
v) as eluent to afford 29 as a yellow solid (46 mg, 50%). M.p.
[3] [3a]
A. Ohta, Y. Yamashita, J. Chem. Soc., Chem. Commun.
[3b]
`
E. H. Elandaloussi, P. Frere, A. Be-
1995, 557Ϫ558. Ϫ
nahmed-Gasmi, A. Riou, A. Gorgues, J. Roncali, J. Mater.
[3c]
Chem. 1996, 6, 1859Ϫ1863. Ϫ
K. Takahashi, T. Shirahata,
[3d]
K. Tomitani, J. Mater. Chem. 1997, 7, 2375Ϫ2379. Ϫ
view: J. Roncali, J. Mater. Chem. 1997, 7, 2307Ϫ2321.
Re-
[4]
[5]
K. Akiba, K. Ishikawa, N. Inamoto, Bull. Chem. Soc. Jpn. 1978,
51, 2674Ϫ2683.
1
255Ϫ258°C. Ϫ H NMR (CDCl3): δ ϭ 1.22 (t, J ϭ 7.4 Hz, 6 H),
M. R. Bryce, A. J. Moore, M. Hasan, G. J. Ashwell, A. T.
Fraser, W. Clegg, M. B. Hursthouse, A. I. Karaulov, Angew.
Chem. Int. Ed. Engl. 1990, 29, 1450Ϫ1452.
1.87 (s, 6 H), 2.75 (m, 4 H), 7.21 (m, 4 H), 7.47 (m, 2 H), 7.60 (m,
2 H). Ϫ CV: Eox ϭ 0.345 V. Ϫ MS (EI); m/z (%): 528 (14) [Mϩ],
350 (45), 468 (38). Ϫ HRMS C26H24S6 (528.8): calcd. 528.0304;
found 528.0304. Crystals for X-ray analysis were grown from
CDCl3.
[6]
[7]
[8]
´
´
´
N. Martın, L. Sanchez, C. Seoane, E. Ortı, P. M. Viruela, R.
Viruela, J. Org. Chem. 1998, 63, 1268Ϫ1279.
M. R. Bryce, M. A. Coffin, M. B. Hursthouse, A. I. Karaulov,
K. Müllen, H. Scheich, Tetrahedron Lett. 1991, 32, 6029Ϫ6033.
Preliminary communication: M. R. Bryce, T. Finn, A. J. Moore,
Tetrahedron Lett. 1999, 40, 3271Ϫ3274.
[9] [9a]
[9b]
X-ray Crystallography: Single-crystal X-ray diffraction experiments
were carried out with a SMART 1 K CCD area detector mounted
on a 3-circle diffractometer, using graphite monochromated Mo-
A. J. Moore, M. R. Bryce, Synthesis 1991, 26Ϫ28. Ϫ
S.
Triki, L. Ouahab, D. Lorcy, A. Robert, Acta Cryst. 1993, C49,
1189Ϫ1192. Ϫ
A. Green, R. E. Hester, J. A. K. Howard, I. K. Lednev, N.
[9c]
A. S. Batsanov, M. R. Bryce, M. A. Coffin,
˚
Kα radiation (λ ϭ 0.71073 A). The data collection nominally co-
´
´
´
´
Martın, A. J. Moore, J. N. Moore, E. Ortı, L. Sanchez, M. Savı-
ron, P. M. Viruela, R. Viruela, T-Q. Ye, Chem. Eur. J. 1998,
4, 2580Ϫ2592.
vered over a hemisphere of reciprocal space,[24] by a combination
of 4 sets of ω scans (each scan 0.3°), each set at different ␾ and/or
2θ angles. Low temperature of the crystals was maintained with a
Cryostream (Oxford Cryosystems) open-flow N2 gas cryostat.[25]
Reflection intensities were integrated using SAINT software[24] and
corrected for absorption by semi-empirical method (SADABS pro-
gram[26]) based on multiple measurements of identical reflections
and Laue equivalents (for 28) or by numerical integration
(SHELXTL programs[27]) based on real shape of the crystal (for
14 and 29). No absorption correction was applied for 12. The struc-
tures were solved by direct methods and refined by full-matrix least
squares against F2 of all data, using SHELXTL software.[27] Non-
H atoms were refined in anisotropic approximation and H atoms
in isotropic one, except for disordered groups, where constrained
refinement was used. In 12 and 28, the complex disorder of CDCl3
molecules of crystallisation was only imperfectly approximated,
hence the high residual electron density. Crystal data and exper-
imental details are listed in Table 1. Atomic coordinates and ther-
mal parameters, bond lengths and angles for compounds 12, 14,
28, and 29 have been deposited at the Cambridge Crystallographic
Data Centre as supplementary publication numbers CCDC-116300
to Ϫ116303, respectively. Copies of these data can be obtained free
of charge on application to CCDC, 12 Union Road, Cambridge
CB2 1EZ, UK [Fax: (internat.) ϩ 44 (0)1223/336033; E-mail:
deposit@ccdc.cam.ac.uk].
[10] [10a]
M. R. Bryce, A. J. Moore, D. Lorcy, A. S. Dhindsa, A.
[10b]
Robert, J. Chem. Soc., Chem. Commun. 1990, 470Ϫ472. Ϫ
A. Robert, D. Lorcy in Molecular Engineering for Advanced
Materials, NATO ASI Series 456, (Ed.: J. Becher, K. Schaum-
burg) Kluwer Academic Publishers, Dordrecht, 1995, 251Ϫ275.
[11] [11a]
Y. Yamashita, S. Tanaka, K. Imaeda, H. Inokuchi, M.
[11b]
Sano, J. Chem. Soc., Chem. Commun. 1991, 1132Ϫ1133. Ϫ
Y. Yamashita, K. Ono, S. Tanaka, K. Imaeda, H. Inokuchi,
[11c]
Adv. Mater. 1994, 6, 295Ϫ298. Ϫ
J. Dong, K. Yakushi, Y.
Yamashita, J. Mater. Chem. 1995, 5, 1735Ϫ1740. Ϫ [11d] Review:
Y. Yamashita, M. Tomura, J. Mater. Chem. 1998, 8,
1933Ϫ1944.
[12] [12a]
G. J. Marshallsay, M. R. Bryce, J. Org. Chem. 1994, 59,
[12b]
´ ´ ´
N. Martın, I. Perez, L. Sanchez, C. Seoane,
[12c]
6847Ϫ6849. Ϫ
´ ´
N. Martın, I. Perez,
J. Org. Chem. 1997, 62, 870Ϫ877. Ϫ
´
L. Sanchez, C. Seoane, J. Org. Chem. 1997, 62, 5690Ϫ5695. Ϫ
[12d]
C. Boulle, O. Desmars, N. Gautier, P. Hudhomme, M. Ca-
riou, A. Gorgues, Chem. Commun. 1998, 2197Ϫ2198.
A. J. Moore, M. R. Bryce, A. S. Batsanov, J. C. Cole, J. A. K.
Howard, Synthesis 1995, 675Ϫ682.
[13]
[14]
´
J. Garın, J. Orduna, S. Uriel, A. J. Moore, M. R. Bryce, S. Weg-
ener, D. S. Yufit, J. A. K. Howard, Synthesis 1994, 489Ϫ493.
[15] [15a]
J. Becher, J. Lau, P. Leriche, P. Mørk, N. Svenstrup, J.
[15b]
Chem. Soc., Chem. Commun. 1994, 2715Ϫ2716. Ϫ
M. B.
Review: K. B. Simonsen, J. Becher, Synlett 1997,
Nielsen, Z-T. Li, J. Becher, J. Mater. Chem. 1997, 7, 1175Ϫ1187.
[15c]
Ϫ
1211Ϫ1220.
[16]
Y. Misaki, T. Ohta, N. Higuchi, H. Fujiwara, T. Yamabe, T.
Mori, H. Mori, S. Tanaka, J. Mater. Chem. 1995, 5, 1571Ϫ1579.
Eur. J. Org. Chem. 2000, 51Ϫ60
59

M. R. Bryce, T. Finn, A. J. Moore, A. S. Batsanov, J. A. K. Howard
FULL PAPER
[17]
[17a]
Reviews of TTF synthesis:
thesis 1976, 489Ϫ514. Ϫ
M. Narita, C. U. Pittman, Syn-
A. Krief, Tetrahedron 1986, 42,
1982, 104, 1882Ϫ1893. Ϫ [22b] P. G. Gassman, D. W. Macomber,
J. W. Hershberger, Organometallics 1983, 2, 1470Ϫ 1472.
[17b]
[17c]
[23]
1209Ϫ1252. Ϫ
G. Schukat, A. M. Richter, E. Fanghänel,
H. Mora, J.-M. Fabre, L. Giral, C. Montginoul, Bull. Soc.
[17d]
Sulfur Rep. 1987, 7, 155Ϫ240. Ϫ
G. C. Papavassiliou, A.
Chim. Belg. 1992, 101, 137Ϫ146.
[24]
`
Terzis, P. Delhaes, in: Handbook of Conductive Molecules and
Polymers, Vol. 1, (Ed.: H. S. Nalwa) J. Wiley and Sons, Chiches-
ter 1997, 152Ϫ227.
SMART and SAINT, Release 4.05, Area detector control and
integration software. Bruker AXS, Analytical X-Ray Instru-
ments, Madison, Wisconsin, USA, 1995.
[18]
[19]
[20]
[25]
R. P. Parg, J. D. Kilburn, T. G. Ryan, Synthesis 1994, 195Ϫ198.
Review: S. Masson, Main Group Chem. News 1994, 2, 18Ϫ25.
A. J. Moore, M. R. Bryce, A. S. Batsanov, J. N. Heaton, C. W.
Lehmann, J. A. K. Howard, N. Robertson, A. E. Underhill, I.
F. Perepichka, J. Mater. Chem. 1998, 8, 1541Ϫ1550.
R.S. Rowland, R. Taylor, J. Phys. Chem. 1996, 100, 7384Ϫ7391.
J. Cosier, A. M. Glazer, J. Appl. Crystallogr. 1986, 19, 105Ϫ107.
[26]
G. M. Sheldrick, SADABS: Program for scaling and correction
of area detector data. University of Göttingen, Germany, 1996.
[27]
G. M. Sheldrick, SHELXTL, Version 5/VMS, Siemens Analyti-
cal X-Ray Instruments Inc., Madison, USA, 1995.
Received May 14, 1999
[21]
[22] [22a]
J. L. Robbins, N. Edelstein, B. Spenser, J. Am. Chem. Soc.
[I99273]
60
Eur. J. Org. Chem. 2000, 51Ϫ60