Tetrathiafulvalene (TTF)-bridged resorcin[4]arene cavitands: Towards new electrochemical molecular switches

Article abstract of DOI:10.1002/hlca.200690194

We report the synthesis of novel resorcin[4]arene-based cavitands featuring two extended bridges consisting of quinoxaline-fused TTF (tetrathiafulvalene) moieties. In the neutral form, these cavitands were expected to adopt the vase form, whereas, upon oxidation, the open kite geometry should be preferred due to Coulombic repulsion between the two TTF radical cations (Scheme 2). The key step in the preparation of these novel molecular switches was the P(OEt) ₃-mediated coupling between a macrocyclic bis(1,3-dithiol-2-thione) and 2 equiv. of a suitable 1,3-dithiol-2-one. Following the successful application of this strategy to the preparation of mono-TTF-cavitand 3 (Scheme 3), the synthesis of the bis-TTF derivatives 2 (Scheme 4) and 19 (Scheme 5) was pursued; however, the target compounds could not be isolated due to their insolubility. Upon decorating both the octol bowl and the TTF cavity rims with long alkyl chains, the soluble bis-TTF cavitand 23 was finally obtained, besides a minor amount of the novel cage compound 25a featuring a highly distorted TTF bridge (Scheme 6). In contrast to 25a, the deep cavitand 23 undergoes reversible vase → kite switching upon lowering the temperature from 293 to 193 K (Fig. 1). Electrochemical studies by cyclic voltammetry (CV) and differential pulse voltammetry (DPV) provided preliminary evidence for successful vase → kite switching of 23 induced by the oxidation of the TTF cavity walls.

Full text of DOI:10.1002/hlca.200690194

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040
Helvetica Chimica Acta – Vol. 89 (2006)
Tetrathiafulvalene (TTF)-Bridged Resorcin[4]arene Cavitands: Towards New
Electrochemical Molecular Switches
by Markus Frei and FranÅois Diederich*
Laboratorium für Organische Chemie, ETH-Zürich, Hçnggerberg, HCI, CH-8093 Zürich
(
e-mail: diederich@org.chem.ethz.ch)
and
Rolando Tremont, Tanya Rodriguez, and Luis Echegoyen*
Department of Chemistry, Clemson University, SC 29634 Clemson, USA
We report the synthesis of novel resorcin[4]arene-based cavitands featuring two extended bridges
consisting of quinoxaline-fused TTF (tetrathiafulvalene) moieties. In the neutral form, these cavitands
were expected to adopt the vase form, whereas, upon oxidation, the open kite geometry should be pre-
ferred due to Coulombic repulsion between the two TTF radical cations (Scheme 2). The key step in the
preparation of these novel molecular switches was the P(OEt) -mediated coupling between a macrocy-
3
clic bis(1,3-dithiol-2-thione) and 2 equiv. of a suitable 1,3-dithiol-2-one. Following the successful applica-
tion of this strategy to the preparation of mono-TTF-cavitand 3 (Scheme 3), the synthesis of the bis-TTF
derivatives 2 (Scheme 4) and 19 (Scheme 5) was pursued; however, the target compounds could not be
isolated due to their insolubility. Upon decorating both the octol bowl and the TTF cavity rims with
long alkyl chains, the soluble bis-TTF cavitand 23 was finally obtained, besides a minor amount of the
novel cage compound 25a featuring a highly distorted TTF bridge (Scheme 6). In contrast to 25a, the
deep cavitand 23 undergoes reversible vase ! kite switching upon lowering the temperature from 293
to 193 K (Fig. 1). Electrochemical studies by cyclic voltammetry (CV) and differential pulse voltammetry
(
DPV) provided preliminary evidence for successful vase ! kite switching of 23 induced by the oxidation
of the TTF cavity walls.
1
. Introduction. – Quinoxaline-bridged resorcin[4]arene-based cavitands such as 1
[
1] can be reversibly switched, under the influence of various external stimuli, between
a closed vase form, capable of guest inclusion [2][3], and an open kite form, featuring an
extended flattened surface [1] (Scheme 1). The vase conformer is prevalent at room
temperature at neutral pH, whereas the kite geometry is predominant at low tempera-
tures (ꢀ213 K) [1], upon protonation with acids such as CF COOH (TFA) [4], or in the
3
II
presence of Zn ions [5]. At low temperature, solvation of the more extended surface
stabilizes the kite geometry, whereas, at higher temperature, the entropic term TDSsolv
becomes unfavorable, and the vase conformation is dominant [1]. More recent investi-
gations also showed that suitably sized solvent molecules (such as small benzene deriv-
atives) favorably solvate (stabilize) the vase form and reduce the propensity for vase !
kite transition [6]. On the other hand, the kite conformation is additionally stabilized by
solvents with substantial H-bonding acidity: weak H-bonding interactions between the
mildly basic quinoxaline N-atoms, and solvent molecules are more efficient in the open
kite than in the closed vase form [6b]. Acid-induced switching from the vase to the kite
ꢀ
2006 Verlag Helvetica Chimica Acta AG, Zürich

Helvetica Chimica Acta – Vol. 89 (2006)
2041
form is attributed to protonation of the mildly basic quinoxaline N-atoms in 1, resulting
in electrostatic repulsion between the cationic cavitand walls in the vase form [4]. This
switching is reversed upon addition of base. Noticeably, both partially and differentially
bridged resorcin[4]arene cavitands have been shown to undergo vase ! kite conforma-
tional switching [7] (for a review, see [8]).
Scheme 1. Temperature- or pH-TriggeredConformational vase Ð kite Equilibration of Quinoxaline-
Bridged Resorcin[4]arene 1
Here, we report the synthesis and conformational switching properties of novel
resorcin[4]arene-based cavitands featuring two extended bridges consisting of quinoxa-
line-fused TTF (=tetrathiafulvalene) moieties, such as in 2 (Scheme 2) [9]. Our aim was
to realize for the first time vase Ð kite interconversion under the stimulus of electro-
chemical electron-transfer processes (for examples of TTF-based electrochemical
switches see [10]). In the neutral form, cavitand 2 was expected to adopt the vase
form (for another deep cavitand with expanded cavity walls, see [11]), whereas, upon
oxidation to the bis(TTF radical cation) or the bis(TTF dication), the open kite geom-
etry should be preferred due to Coulombic repulsion between the two cationic wall
flaps in the vase form. Upon electrochemical reduction, the initial vase form should
be regained (for molecular switches, see [12]).
2
. Results and Discussion. – 2.1. Synthesis of Mono-TTF Cavitand 3. We first
approached the synthesis of mono-TTF-cavitand 3 (Scheme 3) to develop the synthetic
strategy that would subsequently enable the preparation of the desired bis-TTF deriv-
ative 2. The most common protocol for the synthesis of ꢁasymmetricꢂ TTF derivatives is
the coupling of two 1,3-dithiol-2-thiones or 1,3-dithiol-2-ones [13] in the presence of tri-
alkyl or triaryl phosphites or phosphines [14] (for a mechanistic proposal, see [15]).
Hence, our route towards mono-TTF-cavitand 3 involved the macrocyclic 1,3-dithiol-
2-thione 4 as an intermediate, which we intended to couple with 1,3-benzodithiol-2-
one (5) [16] (Scheme 3). The preparation of 4 was envisaged by bridging the two free
phenolic OH groups of cavitand 6 [2b][7b] with dichloroquinoxaline-fused 1,3-
dithiol-2-thione 7.
The synthesis of the key building block 7 started from bis-thiocyanate 8, which was
obtained in 57% yield from benzene-1,2-diamine by oxidative thiocyanation using Br2
and KSCN in MeOH [17] (Scheme 3). Reductive cleavage of the thiocyanate substitu-

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042
Helvetica Chimica Acta – Vol. 89 (2006)
Scheme 2. Electrochemically Induced vase ! kite Switching of Bis-TTF Cavitand 2. TTF=tetrathia-
fulvalene.
ents [18], followed by condensation with CS , afforded the desired 1,3-dithiol-2-thione
2
9
(52%) together with thiourea side product 10 (16%). Subsequent bridging of the 1,2-
diamino groups in 9 with diethyl oxalate [19] provided the dihydroquinoxaline-dione 11
in 90% yield. Halogenation under aromatization to 7 with SOCl at 758 [20] proceeded
2
in only 25% yield. The yield was substantially improved (56%) by using phosgene at
room temperature.
Cavitand 6 was subsequently bridged under standard conditions (Cs CO ,
2
3
Me SO)[1][6][7] with dichloroquinoxaline 7 to afford the macrocyclic bis(1,3-dithiol-
A
H
R
U
G
2
2-thione) 4 in 74% yield. Subsequent coupling of 4 with dithiolone 5 (fourfold excess)
in the presence of P(OEt) led to the targeted TTF cavitand 3, which was isolated as a
3
red solid in 9% yield besides dibenzo-fused TTF 12 as the major product (42% yield).
Products from homo-coupling of 4 were not observed in the conversion, which required
addition of toluene to enhance the solubility of the macrocyclic dithiolone. The struc-
1
13
ture of 3 was established by H- and C-NMR spectroscopy as well as by high-resolu-
tion matrix-assisted laser-desorption-ionization mass spectrometry (HR-MALDI-MS;
matrix: 3-hydroxypicolinic acid (3-HPA)), which showed the protonated molecular ion
+
þ
as base peak at m/z 1555.5180([ M+H] , C
A
T
E
N
A
H
R
U
G
A
T
E
N
A
T
E
N
9
2
83
8
2
.2. Synthesis of Bis-TTF Cavitands. In analogy to the preparation of 3, the anti-bis-
(quinoxaline)-bridged resorcin[4]arene 13 [7][21a] was reacted with 2 equiv. of 7 to give
cavitand 14 (56%; Scheme 4). The coupling of 14 with benzo-1,3-dithiol-2-one (5; 6
equiv.) produced the desired target molecule 2 as revealed by HR-MALDI-MS
(
matrix: 3-HPA) after workup. The parent peak in the spectrum was the protonated
+
molecular ion at m/z 1782.422 ([M+H] , C H N O S ; calc. 1782.429). However,
100 85
8
8 8
the solubility of 2 in all common organic solvents was extremely low, and isolation in
pure form could not be accomplished. While the viability of the synthetic strategy
towards bis-TTF cavitands was unambiguously established with the mass-spectrometric
detection of 2, changes in functionalization were clearly required to obtain a system
with sufficient solubility for isolation and subsequent physical study.

Helvetica Chimica Acta – Vol. 89 (2006)
2043
Scheme 3. Synthesis of the Mono-TTF Cavitand 3
a) Na S·9 H O, H O, 708, 1 h. b) CS , 508, 2 h; 52% (9), 16% (10). c) (COOEt) , 1658, 16 h; 90%. d)
2
2
2
2
2
COCl , DMF, toluene, 208, 3 d; 56%. e) Cs CO , Me SO, 508, 2 d; 74%. f) P(OEt) , toluene, 1308,
A
H
R
U
G
2
2
3
2
3
6
h; 9% (3), 42% (12).
A first approach to enhance the solubility consisted in enlarging the size of the alkyl
legs of the cavitand from C to C chains. For this purpose, octol 15 was prepared (71%)
6
11
by acid-catalyzed condensation (HCl/EtOH) of resorcinol with dodecanal, as previ-

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044
Helvetica Chimica Acta – Vol. 89 (2006)
Scheme 4. Synthesis of the Insoluble Bis-TTF Cavitand 2
a) 7, K CO , Me SO, 608, 16 h; 56%. b) 5, P(OEt) , toluene, 1308, 16 h.
A
H
R
U
G
2
3
2
3
ously reported by Aoyama et al. [22] (Scheme 5). Bridging with 2,3-dichloroquinoxaline
afforded cavitand 16 (73%). Selective removal of the two quinoxaline flaps in the anti-
position by reaction with catechol (CsF/DMF) [21a] provided tetrol 17 in 58% yield.
Subsequent bridging with 2 equiv. of 7 led to bis-dithiolthione 18 in 72% yield.
P(OEt) -mediated coupling of 18 with dithiolone 5 produced bis-TTF derivative 19
3
(HR-MALDI-MS). However, similar to the attempted preparation of 2, isolation of
19 was not successful due to low solubility. It, therefore, became apparent that function-
alization of the upper rim of the cavitand was additionally required to provide sufficient
solubility to the targeted bis-TTF cavitand.
We finally succeeded in producing a soluble target compound by adding two addi-
tional hexylthio chains to each of the two TTF moieties in the cavitand. The required
starting dithiolone intermediate 20 was prepared by reduction of CS with Na [23] to
2
give the unstable intermediate dianionic 1,3-dithiol-2-one-4,5-thiolate [24], which
II
was immediately converted into the Zn complex 21 (60% yield; Scheme 6). Subse-
quent alkylation with hexyl bromide [25] afforded dithiolthione 22, which was trans-
formed with Hg(OAc) into the desired dithiolone 20. P(OEt) -Mediated coupling of
2
3
macrocyclic dithiolthione 18 with 20 (6 equiv.) provided the red-colored bis-TTF cav-
itand 23 (9%), besides the corresponding TTF derivative 24 as the major product
(45%) and a third macrocyclic TTF derivative 25a (<1% yield), whose proposed struc-
ture will be further discussed below. Separation and purification of the three products
required affinity chromatography on SiO (CH Cl ), followed by gel permeation chro-
2
2
2
matography (GPC, BioBeads S-X1; CH Cl ).
2
2
The structure assigned to the targeted cavitand 23 was fully supported by spectro-
scopic analysis. The HR-MALDI-MS (3-HPA) depicted the molecular ion as the parent
+
þ
ion at m/z 2424.9562 (M , C
A
T
E
N
A
H
R
U
G
A
T
E
N
A
T
E
N
1
36 168
8
of major fragment ions, confirming the stability of the macrocycle. The UV/VIS spec-
ꢁ1
ꢁ1
trum (CH Cl , 293 K) featured absorption bands at l 269 (e=24200 l mol cm ),
2
2
max
320 (17500), and 463 nm (4400). The weak band at 463 nm is characteristic for TTF
derivatives in the neutral (reduced) form [26] and confers the red color to 23. The
13
C-NMR spectra (75 MHz, CDCl ) confirmed the C2v symmetry, with 17 (expected)
3
resonances appearing in the aromatic and olefinic spectral region between 107.9 and

Helvetica Chimica Acta – Vol. 89 (2006)
2045
Scheme 5. Synthesis of the Insoluble Bis-TTF Cavitand 19
a) 2,3-Dichloroquinoxaline, K CO , Me
A
H
R
U
G
2
3
2
5
8%. c) 7, K CO , Me SO, 608, 16 h; 72%. d) 5, P(OEt) , toluene, 1308, 16 h.
A
H
R
U
G
2
3
2
3
1
1
52.5 ppm. In the H-NMR spectrum (300 MHz, CDCl /CS 1:1) at 298 K, all aromatic
3 2
resonances could be unambiguously assigned (Fig. 1,a). Moreover, the presence of two
a
overlapping ꢁtripletsꢂ at 5.57 and 5.51 ppm, respectively, for the methine H-atoms H
b
and H in the octol bowl clearly demonstrates the preference of the vase conformation
at or above the room temperature [1].
Gratifyingly, the deep cavitand 23 undergoes vase ! kite switching upon cooling: at
a
b
1
93 K, the methine protons H and H appear strongly upfield-shifted, as a broad signal
around 3.67 ppm (Fig. 1,b). This position is highly characteristic for the kite conformer

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Helvetica Chimica Acta – Vol. 89 (2006)
Scheme 6. Synthesis of the Soluble Bis-TTF Cavitand 23
a) Na, DMF, 208,16 h. b) ZnCl , NH /MeOH. c) Et NBr, H O, 208, 16 h; 60% (steps a–c). d) Hexyl
A
H
R
U
G
2
3
4 2
bromide, MeCN, 808, 24 h; 81%. e) Hg(OAc) , CH Cl , 208, 1 h; 81%. f) P(OEt) , toluene, 1308,
2
2
2
3
16 h; 9% (23), 45% (24), <1% (25a).
[
1]. Acid (TFA)-induced switching of 23 is not advised in view of the instability of the
TTF moieties in acidic environments. In contrast, both 1,3-dithiol-2-thione-fused cavi-
tands 14 and 18 could be reversibly switched in CDCl or CH Cl from the vase to the
3
2
2
kite form either by lowering the temperature or by addition of TFA [4].

Helvetica Chimica Acta – Vol. 89 (2006)
2047

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048
Helvetica Chimica Acta – Vol. 89 (2006)
With less than 1% yield, a second macrocyclic TTF derivative was isolated during
the preparation of 23 (Scheme 6), and HR-MALDI-MS (3-HPA) suggested the forma-
+
þ
tion of structure 25a (m/z 1757.790([ M+H] , C
A
T
E
N
A
H
R
U
G
A
H
R
U
G
A
T
E
N
1
06 117
8
by intramolecular homo-coupling of bis(1,3-dithiol-2-thione) 18. This structural assign-
1
ment was also supported by H-NMR spectroscopy (not shown). Consequently, pure 14
(
the analog of 18 with hexyl instead of undecyl legs) was subjected to P(OEt) -medi-
3
ated coupling in toluene (1308, 16 h), and chromatographic workup (SiO ; CH Cl fol-
2
2
2
lowed by BioBeads S-X1, CH Cl ) afforded pure 25b in 8% yield. Computer modeling,
2
2
using PM3 implemented in Spartan 02, suggested that the TTF moiety in 25a/25b would
be highly strained [27] (Fig. 2,a). The bent angle between the plane through the central
TTF C=C bond, and each of the two planes encompassing the two S-atoms and the
C=C bond fused to the adjacent quinoxaline amounts to ca. 518. However, such a dis-
tortion is not without precedence and Müllen and co-workers reported in 1988 cage
compound 26 with a similarly bent TTF moiety [28] (for another strained cage com-
pound, see [29]). X-Ray crystallography revealed a similar bent angle (as defined
above) of 508 for this stable compound (Fig. 2,b).
Fig. 2. a) Energy-minimizedstructure (PM3, Spartan 02) of the strainedTFF cage 25. Alkyl legs are
omitted for clarity. b) X-Ray crystal structure (CSD code 53228) of cage compound 26 [28a]. Color
coding: C-atoms: grey; O-atoms: red; N-atoms: blue; S-atoms: yellow.
1
The H-NMR spectrum (CDCl ) confirms the C -symmetric structure of 25b (Fig.
3
2v
3
). All aromatic resonances are fully assignable, and their positions further support the
close proximity between quinoxaline flaps and bridging TTF moiety, suggested by the
modeling. The signals of the resorcin[4]arene H-atoms at C(1) and C(5) (see Fig. 3 for
arbitrary numbering) appear only slightly shifted upon changing from 23 (8.19 and 7.17
ppm) to 25b (8.22 and 7.11 ppm). The resonance of the TTF-fused quinoxaline
(
HꢁC(4)) moves slightly upfield, from 7.49 (23) to 7.25 (25b) ppm. A remarkable
downfield shift is seen for the resonances of HꢁC(2) and HꢁC(3) in the free quinoxa-

Helvetica Chimica Acta – Vol. 89 (2006)
2049
1
Fig. 3. H-NMR Spectra (300 MHz) of 25b in CDCl at 298 K. The aromatic resonances are enlarged
3
and assigned. The weak peaks around 7.8 and 7.6 ppm belong to a non-identified impurity, which,
according to MALDI-MS, is not the ꢁdimerꢂ from intermolecular homo-coupling of two molecules of 14.
line flaps, from ca. 7.80and 7.67 in 23 to ca. 8.15 and 8.04 ppm, respectively, in 25b. This
downfield shift presumably is a result of the anisotropic deshielding caused by the TTF
bridge.
13
The C-NMR spectrum (CDCl ) depicts 15 resonances in the aromatic/olefinic
3
range between 153.4 and 119.4 ppm, as expected for C -symmetric 25b. Particularly
2v
2
revealing is the position of the central C(sp ) resonance in the bridging TTF moiety.
In planar TTF derivatives such as 12 (110.8 ppm), 24 (110.4 ppm), or 23 (107.9 and
115.1 ppm), this signal appears around 110ppm. In contrast, this resonance is substan-
tially downfield shifted to 137.0ppm in 25b, as a result of the strong pyramidalization of

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Helvetica Chimica Acta – Vol. 89 (2006)
2
the sp -hybridized C-atom (similar to the curvature effects in fullerenes [30]). Notably,
the corresponding signal in the strained TTF cage 26 (Fig. 2,a) also appears downfield
shifted at 134.5 ppm [28a].
The bridging TTF moiety strongly enforces the vase conformation of 25b. On the
other hand, cooling from 298 down to 193 K induces an upfield shift of the HꢁC(6) res-
onance (numbering of Fig. 3) adjacent to the free quinoxaline flap from 5.71 to 5.42
ppm, while the signal of HꢁC(7) remains unchanged at 5.57 ppm. The specific upfield
shift of HꢁC(6) suggests some degree of conformational change in the flexible, non-
bridged parts of the molecule upon lowering the temperature, but not a transition
towards an open kite geometry.
2
.3. Electrochemical Investigations. Cyclic voltammetry (CV) and differential pulse
voltammetry (DPV) studies were conducted in CH Cl in the presence of Bu NPF
6
2
2
4
+
(
0.1 M). All potentials were referenced against the ferricinium/ferrocene (Fc /Fc)
couple. The CV and DPV traces of bis-TTF-cavitand 23 are shown in Fig. 4.
ꢁ
Compound 23 expectedly undergoes two reversible 2e oxidation steps, the first one
leading to the bis(TTF radical cation) and the second one to the bis(TTF dication). The
first redox couple shows a broad oxidation and a broad reduction peak with a half-wave
1
=2
potential E1 =+0.26 V (DE=99 mV). In contrast, the oxidation and reduction peaks
1=2
of the second redox couple are much narrower with E2 =+0.58 V and DE=60mV.
For comparison, the parent tetrathiafulvalene (TTF) undergoes the two oxidation
1=2
1=2
steps at E1 =0.03 and E2 =0.40 V under the same conditions [31]. Both the elec-
tron-accepting effect of the hexylsulfanyl substituents [32] and the fused quinoxaline
render the two oxidation steps in 23 more difficult than in the parent TTF.
If two TTF moieties in a molecule are in sufficiently close proximity to each other,
the first oxidation to the bis(radical cation) is split into two steps [33]. In this case, the
electronic stabilization of the first-formed radical cation by the p electrons of the sec-
ꢁ
ond TTF moiety reduces the potential of the first 1e oxidation step. Furthermore, the
ꢁ
second 1e oxidation step becomes more difficult as a result of the proximity of the
first-formed radical cation. If the distance between the two TTF moieties is slightly
ꢁ
increased, the two 1e oxidation peaks merge into a single, broadened peak. If the dis-
tance is further increased, thereby eliminating any electronic coupling between the two
ꢁ
TTF chromophores, a single, narrow peak for both 1e oxidations to the bis(radical cat-
ion) is observed. Such influences of the interactions between two TTF moieties on the
electrochemical properties have most recently been described by SallØ and co-workers
in the study of a calix[4]arene–bis-TTF conjugate [34].
Based on this reasoning, we propose an explanation for the observed broadening of
the first and the sharpening of the second oxidation peaks (Fig. 4). In the vase confor-
mation, the two TTF moieties in 23 are sufficiently close to exhibit some degree of elec-
ꢁ
tronic coupling, which results in a broadened peak for the first 2e oxidation step to the
bis(radical cation). Attempts to further resolve this broad peak by changing the exper-
imental conditions (temperature, scan rate, nature of the working electrode (Pt, Au,
glassy carbon)) were not successful.
ꢁ
On the other hand, the reversible second 2e oxidation step to the bis(TTF dica-
tion) suggests that the two chromophores are at larger distance and no longer in elec-
tronic communication. We take this as the first evidence for a possible electrochemi-
cally induced conformational switching from the vase to the kite form as a result of

Helvetica Chimica Acta – Vol. 89 (2006)
2051
Fig. 4. a) CV of 23 (0.5 mM) in CH Cl (+0.1M Bu NPF ) at 293 K. Scan rate: 100 mV/s. b) DPV of
2
2
4
6
23 under the same conditions. Scan rate: 4 mV/s.
the Coulombic repulsion between the two TTF radical cations. Additional experiments
to validate the electrochemical vase ! kite conformational switching are under way.
3
. Conclusions. – In this paper, we report new fascinating functional molecular
architectures, merging TTF redox chemistry with the unique vase ! kite switching
properties of bridged resorcin[4]arene cavitands. As in many projects targeting molec-
ular nanoscale devices, solubility has been a serious issue and compound 23 required
decoration both of the octol bowl and of the TTF cavity rims with long alkyl chains

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Helvetica Chimica Acta – Vol. 89 (2006)
to become soluble in common organic solvents. The formation and isolation of cage
compounds 25a/25b was quite unexpected, in view of their severely distorted TTF
bridge. While their characterization and structural assignment are unambiguous, we
became nevertheless more assured of the assigned structure when we found literature
precedence by Müllen and co-workers for the similarly strained TTF cage 26 for which
an X-ray crystal structure had been obtained [28]. Whereas the deep cavitand 23 under-
goes reversible vase ! kite isomerization upon passing from 293 to 193 K, the strained,
rigid TTF bridge in 25a/25b prevents such large conformational change. Preliminary
evidence for the targeted vase ! kite switching of 23 induced by oxidation of the
ꢁ
TTF cavity walls was obtained by electrochemical studies. Whereas the first 2e oxida-
tion wave in CV and DPV is broadened, as a result of electronic coupling between the
ꢁ
two TTF chromophores in the vase form, the second 2e oxidation step leads to a sharp
wave, which would be expected if the two TTF radical cations are located at substan-
tially larger distance, as in the kite form. Obviously, more experiments will be required
to fully validate this hypothesis. Furthermore, future investigations will address the
host–guest binding properties of the bis-TTF cavitands, and how complexation affects
the redox processes.
We thank the Swiss National Science Foundation for support of this work via the National Research
Program (NRP) ꢀSupramolecular Functional Materialsꢁ and the NCCR ꢀNanoscale Scienceꢁ. Support from
the US National Science Foundation, grant CHE-0408367, is also gratefully acknowledged. We thank Dr.
C. Thilgen (ETH) for help with the nomenclature.
Experimental Part
General. Solvents and reagents were purchased reagent-grade and used without further purification
(
except for 2,3-dichloroquinoxaline, which was recrystallized from EtOH or MeOH). Solvents for extrac-
tions and chromatography were of technical grade and were distilled prior to use. All reactions were car-
ried out under an Ar atmosphere unless otherwise stated. Toluene was distilled from sodium, CH Cl
2
2
from CaH . Anh. Me SO and DMF, stored over molecular sieves, were purchased from Fluka. All prod-
A
H
R
U
G
2
2
ꢁ2
ucts were dried under high vacuum (10 Torr) before anal. characterization. The preparation of the fol-
lowing compounds has been reported in the literature: 5 [16], 6 [2b][7b], 8 [17], 12 [35], 13 [7], 15 [22], 16
[
36], 17 [36], 21 [24]. Flash chromatography (FC): SiO from Fluka or Merck 230–400mesh. Prep. grav-
2
ity gel permeation chromatography (GPC): BIO-RAD Beads SX-1 (pore size 200–400 mm) as stationary
ꢁ1
phase at amb. pressure and temp.; eluent: CH Cl ; 10–20drops min ; fractions of 5–10ml. Anal. TLC:
2
2
precoated SiO glass plates with F-254 fluorescent indicator; visualization by UV light at 254 nm or by
2
staining with a soln. of (NH ) Mo O ·6 H O (20g) and Ce(SO ) (0.4 g) in 10% aq. H
A
H
R
U
G
A
H
R
U
G
4
6
7
24
2
4
2
2
M.p.: Büchi Melting Point B-540; uncorrected. UV/VIS Spectra [nm]: Varian Cary 500 Scan spectropho-
ꢁ1
tometer. IR Spectra [cm ]: Perkin-Elmer 1600-FT-IR spectrometer or a Perkin-Elmer Spectrum BX II.
1
13
NMR ( H and C) Spectra [ppm]: Varian Gemini 300, Varian Mercury 300, or Bruker AMX-500 spec-
trometers; spectra were recorded at r.t. with the solvent peak as reference. FT-ICR-MALDI-MS: Ion
Spec Ultima FT-ICR-MS (337 nm N laser system); matrix: 3-HPA (3-hydroxypicolinic acid) or DCTB
2
(
{(2E)-3-[4-(tert-butyl)phenyl]-2-methylprop-2-enylidene}malonitrile). EI-MS: VG Analytical Tribrid,
USA. Elemental analyses were performed by the Mikrolabor at the Laboratorium für Organische
Chemie, ETH-Zürich. The names of compounds 3, 4, 14, 18, 23, and 25 were generated using the cyclo-
phane nomenclature [37].
Electrochemical Measurements. All electrochemical measurements were performed with the CHI
4
40 Electrochemical Workstation (CH Instruments Inc., Austin, Texas). 0.1M Bu NPF6 (from Fluka)
4
was used as the supporting electrolyte in redistilled CH Cl , degassed with Ar. Pt Wire was employed
2
2
as the counter electrode. An aq. Ag/AgCl electrode, separated by a 0.1M Bu NPF salt-bridge, was
4
6

Helvetica Chimica Acta – Vol. 89 (2006)
2053
used as the reference. Ferrocene (Fc) was added as an internal reference, and all potentials were refer-
+
enced relative to the Fc/Fc couple. A glassy C electrode (CHI, 3 mm in diameter), polished with 1.0–0.3
mm Al paste and ultrasonicated in deionized H O and a CH Cl bath, was used as the working electrode.
2
2
2
The scan rates for cyclic voltammetry (CV) and differential pulse voltammetry (DPV) were 100 and 4
mV/s, resp. For the DPV measurements, the amplitude was 50 mV, and the pulse width was 0.05 s. All
experiments were performed at 293ꢂ2 K.
5,6-Diamino-1,3-benzodithiol-2-thione (9) and5 H-[1,3]Dithiolo[4,5-f]benzimidazol-2,6(7H)-di-
thione (10). Compound 8 (2.44 g, 11 mmol) was added as a solid to a soln. of Na S·9 H O (8.71 g, 96.3
2
2
mmol) in degassed H O (135 ml), and the mixture was stirred for 1 h at 708. After cooling to 508, CS
2
2
(
1.4 ml, 23.2 mmol) was added dropwise, and stirring was continued for 2 h at 508 and 3 h at 208. The yel-
ꢁ2
low precipitate was isolated by filtration, washed with H O, and dried under high vacuum (10 Torr). FC
2
(
SiO ; pentane/THF 1:1) afforded 9 (1.20g, 52%) and 10 (0.46 g, 16%).
2
Data of 9. Orange solid. M.p.: 213–2158. IR (neat): 3375, 3292, 3188, 1615, 1553, 1481, 1405, 1282,
1
13
1
2
046, 1026. H-NMR (300 MHz, (CD )
A
H
R
U
G
A
H
R
U
G
3
2
+
þ
3
09.8; 136.6; 127.7; 105.3. EI-HR-MS: 213.9687 (M , C
A
T
E
N
H
A
H
R
U
G
A
H
R
U
G
7
6
Data of 10. Yellow solid. M.p. >3008. IR (neat): 3147, 3039, 2910, 2357, 1597, 1489, 1455, 1325, 1166,
1
13
1
(
057, 1031, 1018. H-NMR (300 MHz, (CD3)2
A
H
R
N
þ
4
CD3)2
-Thioxo-5,8-dihydro[1,3]dithiolo[4,5-g]quinoxaline-6,7-dione (11). A suspension of 9 (890mg, 4.2
mmol) in diethyl oxalate (50ml) was stirred for 16 h at 165 8, then cooled to 208, and filtered. The product
was washed with EtOH and dried (10 Torr) to give 11 (1.00 g, 90%). M.p. >3008. IR (neat): 3256, 3028,
914, 1682, 1439, 1377, 1328, 1197, 1057. H-NMR (300 MHz, (CD )
A
H
R
U
G
A
H
R
U
G
A
H
R
U
G
A
T
E
N
8
4
2
ꢁ
2
1
13
2
A
T
E
N
3
NMR (75 MHz, (CD
3
)
2
A
H
R
U
G
6,7-Dichloro[1,3]dithiolo[4,5-g]quinoxaline-2-thione (7). To a suspension of 11 (2.00 g, 7.5 mmol) in
DMF (22 ml), COCl (20% soln. in toluene, 12.6 ml, 24 mmol) was added. After stirring for 3 d, CH Cl
2
2
2
2
was added, and the mixture was filtered through SiO and concentrated in vacuo. The residue was puri-
fied by FC (SiO ; pentane/CH Cl 1:1) to give 11 (1.27 g, 56%). Yellow solid. M.p. 2408. IR (neat): 3059,
2
2
2
1
2
920, 2852, 1651, 1587, 1437, 1328, 1259, 1145, 1091, 1060, 1005. H-NMR (500 MHz, CDCl ): 8.02 (s, 2
H). C-NMR (500 MHz, CDCl ): 210.8; 146.7; 145.4; 139.1; 119.9. HR-MALDI-MS (DCTB):
03.8758 (M , C
3
13
3
+
þ
3
3
A
H
R
U
G
A
H
E
N
Cl
A
H
R
U
A
H
R
U
G
9
2
2
9
.18; found: C 35.55, H 0.72, N 9.19.
17S,18R,19R,20S)-17,18,19,20-Tetrahexyl-2,4,6,8,10,12,14,16-octaoxa-3(6,7)-([1,3]dithiolo[4,5-g]-
(
1,5 5,9 9,13
quinoxalina)-7,11,15(2,3)-triquinoxalina-1,5,9,13(1,2,4,5)-tetrabenzenapentacyclo[11.3.1.1 .1 .1 ]icosa-
phane-3 -thione (4). A suspension of 6 (150mg, 0.12 mmol), 7 (38 mg, 0.12 mmol), and Cs CO (48 mg,
2
2
3
0
.15 mmol) in dry Me2
A
H
R
U
G
into H O. The formed precipitate was isolated by filtration, air-dried, and purified by FC (SiO ; CH Cl /
2
2
2
2
AcOEt 97:3) to give 4 (127 mg, 74%). Yellow solid. M.p. >3008. IR (neat): 3064, 2925, 2853, 1734, 1576,
1
1
7
5
478, 1413, 1396, 1328, 1264, 1158, 1062. H-NMR (300 MHz, CDCl ): 8.18 (s, 2 H); 8.11 (s, 2 H);
3
.90–7.75 (m, 6 H); 7.73 (s, 2 H); 7.63–7.48 (m, 6 H); 7.23 (s, 2 H); 7.21 (s, 2 H); 5.66–5.56 (m, 3 H);
.51 (t, J=8.2, 1 H); 2.35–2.20( m, 8 H); 1.58–1.30( m, 32 H); 0.94 (t, J=6.7, 12 H). C-NMR (75
13
MHz, CDCl ): 211.3; 153.2; 152.4; 152.3; 152.2; 152.1; 142.0; 139.5; 139.4; 139.3; 138.0; 135.9; 135.6;
3
1
3
35.6; 135.4; 129.2; 129.2; 128.9; 127.8; 127.6; 127.2; 123.4; 123.2; 119.2; 118.6; 118.6; 34.4; 32.7; 32.4;
+
þ
3
2.0; 29.5; 28.0; 22.8; 14.2. HR-MALDI-MS (DCTB): 1434.5124 ( M , C
A
H
R
U
G
A
H
R
U
G
A
T
E
N
A
H
R
U
G
8
5
78
8
2
(
17S,18R,19R,20S)-3 -(1,3-Benzodithiol-2-ylidene)-17,18,19,20-tetrahexyl-2,4,6,8,10,12,14,16-octaoxa-
3
(6,7)-([1,3]dithiolo[4,5-g]quinoxalina)-7,11,15(2,3)-triquinoxalina-1,5,9,13(1,2,4,5)-tetrabenzenapenta-
1,5 5,9 9,13
cyclo[11.3.1.1 .1 .1 ]icosaphane (3). To a stirred suspension of 4 (100 mg, 70 mmol) in P(OEt) (0.7
3
ml) at 1308, a soln. of 5 (51 mg, 280 mmol) in toluene (1 ml) was added. After stirring for 6 h at 1308,
the mixture was cooled to 208 and the solvent removed in vacuo. Purification by FC (SiO ; CH Cl )
2
2
2
afforded 3 (9 mg, 9%) and 12 (18 mg, 42%).
Data of 3: Red solid. M.p. >3008. IR (neat): 2924, 2853, 2289, 2050, 1979, 1700, 1602, 1570, 1481,
1
1
414, 1398, 1363, 1328, 1263, 1221, 1186, 1158, 1118, 1097, 1062. H-NMR (300 MHz, CDCl , 508): 8.20
3
(
s, 2 H); 8.13 (s, 2 H); 7.86–7.74 (m, 8 H); 7.66–7.44 (m, 10H); 7.24 ( s, 2 H); 7.23 (s, 2 H); 5.70–5.55
13
(m, 4 H); 2.35–2.20( m, 8 H); 1.58–1.27 (m, 32 H); 0.94 (t, J=6.6, 12 H). C-NMR (75 MHz, CDCl3,

2
054
Helvetica Chimica Acta – Vol. 89 (2006)
5
1
1
08): 152.5; 152.4; 152.3; 152.3; 140.0; 139.6; 139.6; 139.5; 138.2; 135.8; 135.8; 135.7; 135.7; 129.1; 129.1;
29.0; 128.9; 127.8; 127.6; 127.4; 123.3; 123.2; 118.9; 118.7; 118.7; 34.3; 32.5; 31.9; 29.7; 29.4; 28.0; 22.7;
+
þ
4
4.0. HR-MALDI-MS (3-HPA): 1555.5180 ([M+H] , C92
A
H
R
U
G
A
H
R
U
G
A
H
R
U
G
A
H
R
U
G
83
8
(
17s,18s,19s,20s)-17,18,19,20-Tetrahexyl-2,4,6,8,10,12,14,16-octaoxa-3,11(6,7)-bis([1,3]dithiolo[4,5-g]-
1,5 5,9 9,13
quinoxalina)-7,15(2,3)-diquinoxalina-1,5,9,13(1,2,4,5)-tetrabenzenapentacyclo[11.3.1.1 .1 .1 ]icosapha-
2
2
ne-3 ,11 -dithione (14). A suspension of 13 (505 mg, 0.47 mmol), 7 (287 mg, 0.94 mmol), and K CO (155
2
3
mg, 1.12 mmol) in dry Me2
A
H
R
U
G
poured into H O. The formed precipitate was isolated by filtration, washed with H O, air-dried, and puri-
2
2
fied by FC (SiO ; CH Cl /AcOEt 99 :1 ! 98 :2) to give 14 (400 mg, 56%). Yellow solid. M.p. >3008. IR
2
2
2
1
(
neat): 3070, 2920, 2848, 1576, 1478, 1414, 1396, 1328, 1261, 1197, 1155, 1065. H-NMR (300 MHz,
CDCl ): 8.07 (s, 4 H); 7.79 (s, 4 H); 7.80–7.75 (m, 4 H); 7.61–7.55 (m, 4 H); 7.19 (s, 4 H); 5.49 (t,
3
13
J=7.7, 2 H); 5.41 (t, J=7.8, 2 H); 2.26–2.18 (m, 8 H); 1.58–1.24 (m, 32 H); 0.92 (t, J=6.7, 12 H). C-
NMR (75 MHz, CDCl ): 210.6; 153.2; 152.8; 152.5; 142.7; 139.7; 138.4; 136.1; 135.6; 129.6; 127.8;
3
1
1
23.7; 119.5; 118.7; 34.7; 34.7; 32.6; 32.6; 32.1; 29.5; 28.1; 22.9; 14.3. HR-MALDI-MS (3-HPA):
+
þ
6
541.4156 ([M+H] , C
A
H
R
U
G
A
T
E
N
N
A
T
U
A
H
R
U
G
86
77
8
(
17s,18s,19s,20s)-17,18,19,20-Tetrahexyl-2,4,6,8,10,12,14,16-octaoxa-3,11(6,7)-bis([1,3]dithiolo[4,5-g]-
1,5 5,9 9,13
quinoxalina)-7,15(2,3)-diquinoxalina-1,5,9,13(1,2,4,5)-tetrabenzenapentacyclo[11.3.1.1 .1 .1 ]icosapha-
2
2
ne-3 ,11 -dithione (18). A suspension of 17 (360mg, 0.27 mmol), 7 (162 mg, 0.53 mmol), and K CO (88
2
3
mg, 0.63 mmol) in dry Me2
A
H
R
U
G
poured into H O. The formed precipitate was isolated by filtration, washed with H O, air-dried and puri-
2
2
fied by FC (SiO ; CH Cl ! CH Cl /AcOEt 98 :2) to give 18 (347 mg, 72%). Yellow solid. M.p. > 2808.
2
2
2
2
2
1
IR (neat): 2921, 2850, 1647, 1559, 1415, 1399, 1368, 1330, 1259, 1160, 1115, 1066, 1014. H-NMR (300
MHz, CDCl ): 8.07 (s, 4 H); 7.80( s, 4 H); 7.81–7.75 (m, 4 H); 7.62–7.56 (m, 4 H); 7.18 (s, 4 H); 5.49
dd, J=8.2, 7.4, 2 H); 5.41 (dd, J=8.2, 8.0, 2 H); 2.30–2.18 (m, 8 H); 1.50–1.20 ( m, 72 H); 0.89 (t,
3
(
1
3
J=6.5, 12 H). C-NMR (75 MHz, CDCl ): 210.6; 153.2; 152.8; 152.5; 142.7; 139.7; 138.4; 136.0; 135.6;
3
1
1
6
29.6; 127.8; 123.7; 119.5; 118.7; 34.7; 32.6; 32.2; 30.0; 29.7; 28.1; 22.9; 14.4. HR-MALDI-MS (3-HPA):
+
þ
6
821.7279 ([M+H] , C
A
H
R
U
G
A
H
R
U
G
A
H
R
U
G
A
T
E
N
1
06 117
8
9.86, H 6.42, N 6.15; found: C 69.93, H 6.55, N 6.31.
,5-Bis(hexylsulfanyl)-1,3-dithiol-2-thione (22). To a suspension of 21 (354 mg, 0.49 mmol) in MeCN
7 ml), 1-bromohexane (0.34 ml, 2.45 mmol) was added, and the mixture was heated to reflux for 24 h.
After cooling to 208, the mixture was filtered, and the filtrate was concentrated in vacuo. After addition
of CH Cl and washing with H O, the org. phase was dried (MgSO ) and concentrated in vacuo. Purifi-
4
(
A
H
R
U
G
ACHTREUNG
2
2
2
4
cation by FC (SiO ; pentane/CH Cl 1:1) afforded 22 (290mg, 81%). Yellowish oil. IR (neat): 2955,
2
2
2
1
2
922, 2854, 2359, 2127, 1759, 1671, 1459, 1375, 1288, 1244, 1062. H-NMR (300 MHz, CDCl ): 2.85 (t,
J=7.3, 4 H); 1.63 (quint., J=7.3, 4 H); 1.45–1.20( m, 12 H); 0.87 (t, J=6.9, 6 H). C-NMR (75 MHz,
CDCl ): 210.9; 136.1; 36.8; 31.4; 29.7; 28.3; 22.6; 14.2. EI-HR-MS: 366.0634 (M , C
3
13
+
þ
5
A
H
E
N
A
H
R
U
G
3
3
66.0638).
,5-Bis(hexylsulfanyl)-1,3-dithiol-2-one (20). To a soln. of 22 (1.80g, 4.9 mmol) in CH Cl (150ml),
4
2
2
Hg(OAc) (4.64 g, 14.7 mmol) was added. The mixture was stirred for 1 h at 208, then it was filtered and
2
the filtrate concentrated in vacuo. Purification by FC (SiO ; pentane/CH Cl 1:1) afforded 20 (1.39 g,
2
2
2
1
8
1%). Yellowish oil. IR (neat): 2924, 2854, 2360, 2217, 1752, 1668, 1605, 1455, 1293, 1101. H-NMR
(
300 MHz, CDCl ): 2.83 (t, J=7.4, 4 H); 1.70–1.58 (m, 4 H); 1.46–1.21 (m, 12 H); 0.88 (t, J=6.9, 6
3
13
H). C-NMR (75 MHz, CDCl ): 190.4; 127.4; 36.9; 31.5; 29.8; 28.4; 22.7; 14.2. EI-HR-MS: 350.0859
3
+
þ
4
(M , C
A
H
R
U
G
A
T
E
N
1
5
2
2
(
17s,18s,19s,20s)-3 ,11 -Bis[4,5-bis(hexylsulfanyl)-1,3-dithiol-2-ylidene]-17,18,19,20-tetraundecyl-2,4,
6
,8,10,12,14,16-octaoxa-3,11(6,7)-bis([1,3]dithiolo[4,5-g]quinoxalina)-7,15(2,3)-diquinoxalina-1,5,9,13-
1,5 5,9 9,13
(
1,2,4,5)-tetrabenzenapentacyclo[11.3.1.1 .1 .1 ]icosaphane (23), 4,4’,5,5’-Tetrakis(hexylsulfanyl)-2,2’-
bi-1,3-dithiol (24), and(17 S,18S,19S,20S)-17,18,19,20-Tetraundecyl-2,4,6,8,10,12,14,16-octaoxa-3,11(6,7)-
bis([1,3]dithiolo[4,5-g]quinoxalina)-7,15(2,3)-diquinoxalina-1,5,9,13(1,2,4,5)-tetrabenzenahexacyclo-
1,5 5,9 9,13 3,11
2
2
[
11.3.1.1 .1 .1 .0 ]icosaphan-3 (11 )-ene (25a). To a stirred suspension of 18 (100 mg, 55 mmol) in
P(OEt) (0.7 ml) at 1308, a soln. of 20 (115 mg, 330 mmol) in toluene (1 ml) was added. After stirring
3
for 16 h at 1308, the mixture was cooled to 208, and the solvent was removed in vacuo. Purification by
FC (SiO ; CH Cl ) and GPC (CH Cl ) afforded 23 (12 mg, 9%), 24 (99 mg, 45%), and 25a (1 mg, <1%).
2
2
2
2
2

Helvetica Chimica Acta – Vol. 89 (2006)
2055
Data of 23. Red solid. M.p. >2808. IR (neat): 3069, 2924, 2852, 2324, 2050, 1979, 1694, 1607, 1576,
1
1
481, 1467, 1456, 1414, 1398, 1363, 1329, 1262, 1221, 1186, 1159, 1117, 1062, 1019. H-NMR (300 MHz,
CDCl ): 8.19 (s, 4 H); 7.82–7.78 (m, 4 H); 7.70–7.63 (m, 4 H); 7.49 (s, 4 H); 7.17 (s, 4 H); 5.57 (t,
3
J=8.4, 2 H); 5.51 (t, J=7.9, 2 H); 2.97–2.77 (m, 8 H); 2.29–2.16 (m, 8 H); 1.73–1.62 (m, 8 H);
1
3
1
1
3
.50–1.22 (m, 96 H); 0.94–0.86 (m, 24 H). C-NMR (75 MHz, CDCl ): 152.5; 152.4; 152.3; 152.2;
3
40.4; 139.5; 138.2; 135.6; 135.5; 129.4; 127.8; 127.5; 123.3; 118.7; 118.6; 115.1; 107.9; 36.4; 34.1; 32.4;
2.2; 31.9; 31.2; 29.6; 29.3; 28.1; 27.8; 22.6; 22.5; 14.0; 14.0. HR-MALDI-MS (3-HPA): 2424.9562 ( M ,
+
þ
C136
A
H
R
U
G
A
H
R
U
G
A
H
R
U
G
A
H
R
U
G
; calc. 2424.9633).
168
8
8
12
Data of 24. Orange solid. M.p. 26–288. IR (neat): 2951, 2921, 2854, 2359, 1674, 1458, 1418, 1374, 1306,
1
1
(
1
258, 1206, 1109. H-NMR (300 MHz, CDCl ): 2.81 (t, J=7.4, 8 H); 1.62 (quint., J=7.4, 8 H); 1.47–1.20
3
13
m, 24 H); 0.87 (t, J=6.9, 12 H). C-NMR (75 MHz, CDCl ): 128.0; 110.4; 36.5; 31.5; 29.9; 28.4; 22.8;
3
+
4.3. EI-HR-MS: 668.1830( M , C
þ
8
A
H
R
U
G
A
T
E
N
3
0
Data of 25a. White solid. M.p. 239–2428. IR (neat): 2921, 2848, 2358, 2051, 1979, 1732, 1576, 1466,
1
1
414, 1399, 1366, 1330, 1259, 1159, 1115, 1075. H-NMR (300 MHz, CDCl ): 8.22 (s, 4 H); 8.20–8.12
3
(
m, 4 H); 8.08–8.00 (m, 4 H); 7.25 (s, 4 H); 7.11 (s, 4 H); 5.71 (t, J=8.4, 2 H); 5.57 (t, J=8.1, 2 H);
13
2
1
3
.34–2.08 (m, 8 H); 1.60–1.20 ( m, 72 H); 0.92–0.80 (m, 12 H). C-NMR (75 MHz, CDCl ): 153.2;
3
53.0; 152.9; 152.3; 139.8; 138.8; 137.8; 136.8; 136.0; 135.7; 130.6; 127.6; 123.2; 121.6; 119.2; 34.0; 33.7;
+
3.3; 31.9; 31.6; 29.8; 29.7; 29.4; 29.4; 27.9; 22.7; 14.1. HR-MALDI-MS (3-HPA): 1757.790([ M+H] ,
þ
C106
A
H
R
U
G
A
H
R
U
G
A
H
R
U
G
A
H
E
N
S ; calc. 1757.787).
117
8
8
4
(
17s,18s,19s,20s)-17,18,19,20-Tetrahexyl-2,4,6,8,10,12,14,16-octaoxa-3,11(6,7)-bis([1,3]dithiolo[4,5-g]-
1,5 5,9 9,13 3,11
quinoxalina)-7,15(2,3)-diquinoxalina-1,5,9,13(1,2,4,5)-tetrabenzenahexacyclo[11.3.1.1 .1 .1 .0 ]ico-
saphan-3 (11 )-ene (25b). A suspension of 14 (100 mg, 65 mmol) in P(OEt) was heated to 1308. Toluene
2
2
3
(
1 ml) was added, and heating at 1308 was continued for 16 h. Evaporation in vacuo and FC (SiO
2
;
CH Cl ), followed by GPC (CH Cl ), provided 25b (7 mg, 8%). White solid. M.p. 2278. IR (neat):
2
2
2
2
2
1
7
920, 2851, 2358, 2051, 1979, 1734, 1580, 1479, 1466, 1443, 1414, 1396, 1361, 1329, 1262, 1222, 1186,
1
3
154, 1116, 1075. H-NMR (300 MHz, CDCl ): 8.22 (s, 4 H); 8.20–8.12 (m, 4 H); 8.08–8.00 (m, 4 H);
.25 (s, 4 H); 7.11 (s, 4 H); 5.71 (t, J=8.4, 2 H); 5.57 (t, J=8.1, 2 H); 2.34–2.08 (m, 8 H); 1.56–1.24
13
(m, 32 H); 0.96–0.86 (m, 12 H). C-NMR (75 MHz, CDCl ): 153.4; 153.3; 153.1; 152.5; 140.0; 139.0;
3
1
38.0; 137.0; 136.2; 135.9; 130.8; 127.9; 123.4; 121.8; 119.4; 33.9; 33.6; 31.9; 31.5; 29.6; 27.9; 22.6; 14.0.
+
þ
4
HR-MALDI-MS (3-HPA): 1477.4771 ([M+H] , C
A
H
R
U
H
A
H
R
U
G
A
H
R
U
G
A
H
R
U
G
86
77
8
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ReceivedJune 27, 2006