On the phosphite-mediated synthesis of dithiafulvenes and π-extended tetrathiafulvalenes

Article abstract of DOI:10.1055/s-0032-1317921

By phosphite-mediated couplings between functionalized benzaldehydes and 1,3-dithiole-2-thiones we have obtained a variety of π-extended tetrathiafulvalenes (TTF). In particular, this method has provided a new stilbene-extended TTF with lateral alkyne functionalities, an H-type cruciform structure. This outcome is the result of a phosphite-mediated coupling between two aldehydes. Georg Thieme Verlag Stuttgart New York.

Full text of DOI:10.1055/s-0032-1317921

LETTER
▌231
letter
On the Phosphite-Mediated Synthesis of Dithiafulvenes and π-Extended
Tetrathiafulvalenes
Extended Tetrathiafulvalenes by Phosphite-Mediated Couplings
Simon Stubbe Schou, Christian Richard Parker, Kasper Lincke, Karsten Jennum, Johan Vibenholt, Anders Kadziola,
Mogens Brøndsted Nielsen*
Department of Chemistry, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen Ø, Denmark
Fax +45 35320212; E-mail: mbn@kiku.dk
Received: 30.10.2012; Accepted after revision: 23.11.2012
degassed with argon prior to use, but not distilled). This
Abstract: By phosphite-mediated couplings between functional-
compound was next successfully subjected to a cross-cou-
ized benzaldehydes and 1,3-dithiole-2-thiones we have obtained a
pling reaction with the known diethynyl compound 58 to
variety of π-extended tetrathiafulvalenes (TTF). In particular, this
method has provided a new stilbene-extended TTF with lateral
furnish the cruciform 1 in a yield of 60%.9
alkyne functionalities, an H-type cruciform structure. This outcome
is the result of a phosphite-mediated coupling between two alde-
hydes.
S
S
S
S
S
S
S
RCHO
X
P(OR)3
P(OR)3
S
R
Key words: cruciform, heterocycles, phosphite, sulfur, tetrathia-
fulvalene
TTF
X = S, O
DTF
Scheme 1 Phosphite-mediated couplings
The phosphite-mediated coupling of two 1,3-dithiole-2-
(thi)ones has been employed extensively for preparing de-
rivatives of the redox-active molecule tetrathiafulvalene
(TTF, Scheme 1).1 This method has also been employed
to prepare dithiafulvenes (DTF) and π-extended TTFs via
coupling between a central unit containing one, two, or
three aldehyde functionalities and a 1,3-dithiole-2-
(thi)one2,3 or coupling of the latter to an anthraquinone.4
Very recently we prepared the cruciform structure 1
(Figure 1) that is composed of two orthogonally situated
extended TTFs.3 The final step in the synthesis involved a
triethylphosphite-mediated coupling of an OPE3 (oligo-
phenyleneethynylene) containing an aldehyde group in
each end. In general, π-conjugated cruciform motifs are
interesting as molecular wires for organic electronics or as
molecular sensors.3,5 Here we present an alternative syn-
thesis of the cruciform 1 and the broader scope of the
phosphite-mediated coupling; in particular, its use for pre-
paring a stilbene unit (or OPV2, oligophenylenevinylene)
as the central part of a new H-type extended TTF cruci-
form.
CO2Pr
PrO2C
S
phosphite
coupling
RS
phosphite
S
coupling
SR
S
S
S
S
RS
S
SR
S
CO2Pr
PrO2C
1 (R = CH2CH2CN)
Figure 1 Extended TTF cruciform molecule prepared by final
phosphite-mediated couplings
Next, we investigated the possibility for generating bis-
and tris-DTF-substituted benzenes by phosphite cou-
plings. Related DTF compounds were previously pre-
pared
by
Wittig–Horner
reactions.10
First,
terephthalaldehyde (6) was treated with the thione 7,6
which gave the benzene-extended TTF 811 (Scheme 3).
The yield varied from 54% to 79% when increasing the
molar equivalents of 7 relative to 6 from 2.2 to 4. Next,
1,3,5-triformylbenzene 9 was treated with 7 (ratio of 1:9)
to generate the tris-DTF 1012 in a yield of 20%, corre-
sponding to a yield of 58% for each DTF formation. The
reaction was very slow as it took four days for consump-
tion of the aldehyde starting material 9 (possibly, in part,
due to the insolubility of the mono- and di-DTF adducts),
while consumption of 6 only took two hours.
Our first objective was to prepare a simple but useful DTF
building block containing an iodophenyl functionality
that could subsequently be used in palladium-catalyzed
cross-coupling reactions and hence be used in an alterna-
tive procedure for making the cruciform 1. Indeed, heat-
ing a mixture of 4-iodobenzaldehyde (2) and the 1,3-di-
thiole-2-thione 36 (ratio of 1:2.5) in triethylphosphite to
110 °C for two hours produced the DTF 4 in almost quan-
titative yield (Scheme 2)7 (note: all reactions were con-
ducted under an argon atmosphere and with
triethylphosphite that had been stored under argon and
In an original attempt to prepare a derivative of 5 contain-
ing alkylthio substituents at the DTF rings rather than es-
ter groups, we subjected the dialdehyde 1113 and each of
the thiones 1214 and 1314 to phosphite-mediated couplings
SYNLETT 2013, 24, 0231–0235
Advanced online publication: 12.12.2012
0
9
3
6
-
5
2
1
4
1
4
3
7
-
2
0
9
6
DOI: 10.1055/s-0032-1317921; Art ID: ST-2012-D0931-L
© Georg Thieme Verlag Stuttgart · New York

232
S. S. Schou et al.
LETTER
kene, the oxygen of one aldehyde has to act as an electro-
phile towards phosphorus, and the carbon of this aldehyde
thereafter becomes nucleophilic towards another electro-
philic aldehyde carbon. Indeed, Ramirez et al.16 have pre-
viously shown that two molecules of o- or p-nitro-
benzaldehyde, that is, an aldehyde containing an electron-
withdrawing substituent, can react with trialkylphosphites
at 20 °C to furnish a 2,2,2-trialkoxy-1,3,2-dioxaphos-
pholane (Figure 2), while m-nitrobenzaldehyde did not
undergo reaction under these conditions. In our reaction,
we cannot say whether the aldehyde–aldehyde coupling
occurs before or after the aldehyde–thione coupling as
both the DTF and aldehyde para substituents as well as
the one ortho-ethynyl substituent should allow for meso-
meric delocalization of the negative charge formed at the
carbonyl carbon after nucleophilic attack by phosphorus
on the neighboring carbonyl oxygen (Figure 3). Compet-
ing reaction channels should thus influence the yields of
14 and 15. It should be noted that isolation of 14 was per-
formed by pouring the reaction mixture onto methanol, re-
sulting in precipitation of the compound. We cannot
exclude that some of the originally targeted products are
formed, but they were not isolated in our hands from the
mother liquor after 14 had been precipitated. The only by-
product we could unambiguously assign was the TTF re-
sulting from homocoupling of two thiones. The longer
alkyl groups in 15 resulted in increased solubility and ren-
dered purification by column chromatography necessary,
and again the tetraalkylthio-substituted TTF was identi-
fied as a byproduct. As a test experiment, we subjected
benzaldehyde itself to the phosphite conditions in the ab-
sence of a thione; no reaction was observed after six hours
of heating in agreement with the work of Ramirez et al.16
The formation of small amounts of stilbene has, neverthe-
less, previously been observed when heating benzalde-
hyde in triethylphosphite at 220 °C in an ampul for 8.5
hours as has the formation of difurylethylene by heating
furfural and triethylphosphite at 160 °C.17 We also con-
ducted test reactions on the dialdehyde 11 with trieth-
ylphosphite in the absence of the thione at 100 °C and at
room temperature. When heated, reactions occur readily
giving a mixture of products. Attempts to precipitate these
compounds with methanol failed, but removal of the sol-
vents gave a solid which was highly luminescent under
UV-light irradiation (also on TLC plates and in solution).
At ambient temperatures, 11 was also found to react slow-
ly with triethylphosphite; however, there were again many
R
S
+
I
CHO
S
S
3
R
2
96% P(OEt)3
RS
R = CH2CH2CN
SR
S
S
I
CO2Pr
S
4
PrO2C
S
PdCl2(PPh3)2, CuI
THF, Et3N
60%
S
S
CO2Pr
PrO2C
1
5
Scheme 2 Alternative synthesis of 1 via a new DTF building block
MeS
S
MeS
S
SMe
S
MeS
S
7
S
P(OEt)3
OHC
CHO
79%
S
6
S
MeS
SMe
8
SMe
S
SMe
S
7
CHO
MeS
P(OEt)3
S
MeS
20%
S
OHC
CHO
9
S
MeS
S
SMe
10
Scheme 3 Synthesis of benzene-extended TTF
1
products observed when monitoring the reaction by H
as shown in Scheme 4 (using 3–4 mol equiv of the thi-
ones). Surprisingly, these reactions generated the stilbene
(OPV2) derivatives 14 and 1515 in reasonable yields con-
sidering the fact that three couplings have occurred. It is
noteworthy that a similar compound did not seem to form
even as a byproduct in the 79% yielding synthesis of 8, al-
though we cannot account for the exact fate of the remain-
ing 21% of the dialdehyde 6. Thus, the presence of the
electron-withdrawing ethynyl substituents in 11 enhances
the electrophilicity of both the carbonyl carbon and its
neighboring oxygen, the latter towards phosphite. For
phosphite-mediated coupling of two aldehydes to an al-
13
NMR and C NMR spectroscopy, there were also some
signals observed in 31P NMR spectra. However, these
products were not as highly luminescent as those formed
upon heating the reaction mixture. Although the exact
products from these reactions were not identified, the re-
sults confirm that 11 by itself readily reacts with trieth-
ylphosphite.
Although not an aldehyde substrate, it is worth mention-
ing that reductive dimerization of phthalic anhydride to
biphthalyl by triethylphosphite was found to occur in
yields of 65–70%.18
Synlett 2013, 24, 231–235
© Georg Thieme Verlag Stuttgart · New York

LETTER
Extended Tetrathiafulvalenes by Phosphite-Mediated Couplings
233
The 1H NMR spectra of cruciforms 14 and 15 showed four
CH resonances in the region δ = 6.9–7.8 ppm, which are
assigned to the fulvenes (two identical protons), the cen-
tral alkene (two identical protons), and the two different
aryl protons (two identical pairs). The assignment of the
central double bond to an E configuration seems reason-
able from steric reasons, but was confirmed by X-ray
crystallographic analysis of 14 as shown in Figure 4. The
two 1,3-dithiole rings are not in the same plane as the cen-
tral OPV2 plane; thus, the angle between the least squares
plane defined by a dithiole ring and the least squares plane
defined by the neighboring benzene ring is 37°.
SiMe3
CHO
RS
RS
S
S
S
+
OHC
12 (R = Et)
13 (R = Bu)
Me3Si
11
P(OEt)3
SiMe3
SR
SiMe3
RS
S
S
S
S
SR
Me3Si
RS
Me3Si
14 (R = Et, 27%)
15 (R = Bu, 17%)
Scheme 4 Synthesis of H-type extended TTF cruciforms
O2N
NO2
O
O
P
RO
OR
R = Me or Et
OR
Figure 2 2,2,2-Trialkoxy-1,3,2-dioxaphospholane products (mixture
of diastereomers) formed from p-nitrobenzaldehyde and a trialkyl-
phosphite at 20 °C.16
Figure 4 Two different views of the molecular structure of 14
(CCDC 908191); crystals were grown from CH2Cl2–heptane
SiMe3
SiMe3
•
The new extended TTFs are all strong chromophores. Fig-
ure 5 shows the absorption spectra of the benzene-extend-
ed TTF 8 and 10 and the new H-type cruciform 15 in
comparison to the previously reported cruciform 1.3 Com-
pound 15 has a lowest-energy absorption (λmax = 464 nm)
that is slightly red-shifted relative to the similar absorp-
tions of 8 (λ = 407 and 424 nm) and of 1 [λ = 402, 437 nm
(shoulder)]. The intensities of these absorptions are simi-
lar for 8 and 15, but significantly lower than those of 1, in
accordance to the fact that 1 has two more DTF units. In
addition, compound 15 exhibits two absorptions at λ =
276 and 313 nm (shoulder). For comparison, (E)-stilbene
has absorptions at λ = 295 and 307 nm (MeCN)19 and 1,4-
bis(trimethylsilylethynyl)benzene has absorptions at λ =
279, 288, and 294 nm (CHCl3).20 Compound 10 exhibits
absorption maxima at λ = 246 and 371 nm. The lowest-en-
ergy absorption is thus significantly blue-shifted relative
to those of the other compounds. The three DTF are in 10
positioned in meta positions relative to each other, which
accounts for a less efficient π-electron delocalization
between them.
X
X
O
P(OEt)3
O P(OEt)3
X = O
or 1,3-dithiole
Me3Si
Me3Si
SiMe3
SiMe3
SR
RS
S
S
O
O
P(OEt)3
O P(OEt)3
Me3Si
Me3Si
Figure 3 Selected resonance formulas for the intermediates (with X
equal to either O or the 1,3-dithiole ring) resulting from attack of tri-
alkylphosphite on aldehyde oxygen
© Georg Thieme Verlag Stuttgart · New York
Synlett 2013, 24, 231–235

234
S. S. Schou et al.
LETTER
Fueno, H.; Tanaka, K.; Misaki, Y. Chem. Lett. 2008, 37, 82.
(e) Guerro, M.; Pham, N. H.; Massue, J.; Bellec, N.; Lorcy,
D. Tetrahedron 2008, 64, 5285. (f) Cocherel, N.; Leriche, P.;
Ripaud, E.; Gallego-Planas, N.; Frère, P.; Roncali, J. New J.
Chem. 2009, 33, 801. (g) Ripaud, E.; Leriche, P.; Cocherel,
N.; Cauchy, T.; Frère, P.; Roncali, J. Org. Biomol. Chem.
2011, 9, 1034. (h) Bouzan, S.; Chen, G.; Mulla, K.; Dawe, L.
N.; Zhao, Y. Org. Biomol. Chem. 2012, 10, 7673.
(3) Parker, C. R.; Wei, Z.; Arroyo, C. R.; Jennum, K.; Li, T.;
Santella, M.; Bovet, N.; Zhao, G.; Hu, W.; van der Zant, H.
S. J.; Vanin, M.; Solomon, G. C.; Laursen, B. W.; Nørgaard,
K.; Nielsen, M. B. Adv. Mater. 2012, in press; DOI:
10.1002/adma.201201583.
(4) (a) Christensen, C. A.; Batsanov, A. S.; Bryce, M. R. J. Org.
Chem. 2007, 72, 1301. (b) Chen, G.; Bouzan, S.; Zhao, Y.
Tetrahedron Lett. 2010, 51, 6552.
(5) Zucchero, A. J.; McGrier, P. L.; Bunz, U. H. F. Acc. Chem.
Res. 2010, 43, 397.
(6) Simonsen, K. B.; Svenstrup, N.; Lau, J.; Simonsen, O.;
Mørk, P.; Kristensen, G. J.; Becher, J. Synthesis 1996, 407.
(7) (a) Synthesis of 4
Figure 5 UV-vis absorption spectra in CH2Cl2
In conclusion, by phosphite-mediated couplings we have
obtained a variety of DTF/extended TTF compounds. The
serendipitous formation of a stilbene-extended TTF from
a diethynyl-substituted terephthalaldehyde, while tere-
phthalaldehyde itself furnished the expected benzene-ex-
tended TTF, demonstrates how a subtle balance of
electronic effects determines the outcome of phosphite-
mediated couplings of benzaldehyde derivatives. In this
work we focused attention on triethylphosphite as re-
agent; it would be interesting to investigate in future work
the outcome when using instead trimethylphosphite.
Moreover, it is worth noting that the stilbene/H-type cru-
ciform derivatives 14 and 15 resemble previously
reported21 OPE/OPV H-mers without DTF units and they
might indeed be interesting as functional wires for molec-
ular electronics after further functionalization. We are
currently exploring these molecules for further acetylenic
scaffolding via the four ethynyl groups. Gratifyingly, pre-
liminary experiments show that good stability of the com-
pound is maintained after removal of the silyl protecting
groups.
A suspension of 4-iodobenzaldehyde (2, 1.005 g, 4.34
mmol) and the thione 2 (3.303 g, 10.85 mmol) in dry
degassed P(OEt)3 (12.5 mL) was heated to 110 °C under an
atmosphere of Ar. During the heating, the solid dissolved,
and the color of the solution was a brown yellow color.
Monitoring the reaction by TLC revealed that the reaction
was complete after 2 h. The solvent was removed under
reduced pressure. The brown-yellow colored residue was
washed with PE to remove any excess P(OEt)3. The residue
was dissolved in minimal CH2Cl2 and purified by flash
column chromatography (SiO2, PE–CH2Cl2 = 1:4); the first
yellow fraction gave the desired compound as a yellow oil or
as a fine pale yellow crystalline material (2.043 g, 96%),
which darkens over time; mp 97–100 °C. 1H NMR (500
MHz, CDCl3): δ = 7.67 (d, J = 8.4 Hz, 2 H), 6.93 (d, J = 8.4
Hz, 2 H), 6.42 (s, 1 H), 3.12–3.04 (m, 4 H), 2.79–2.71 (m, 4
H). 13C NMR (125 MHz, CDCl3): δ = 137.77, 135.23,
131.27, 128.65, 127.85, 125.02, 117.60, 117.54, 115.54,
91.53, 31.15, 31.13, 19.07, 19.02. IR (ATR): ν = 2995 (m),
2870 (m), 2926 (m), 2246 (m, CN), 1738 (s), 1679 (m), 1571
(s), 1543 (s), 1491 (m), 1478 (s), 1407 (s), 1391 (s) cm–1.
MS–FAB: m/z = 487 [M]+. Anal. Calcd (%) for C16H13IN2S4:
C, 39.34; H, 2.68; N, 5.74. Found: C, 39.41; H, 2.54; N, 5.63.
(8) Jennum, K.; Vestergaard, M.; Pedersen, A. H.; Fock, J.;
Jensen, J.; Santella, M.; Led, J. J.; Kilså, K.; Bjørnholm, T.;
Nielsen, M. B. Synthesis 2011, 539.
Acknowledgment
(9) Synthesis of 1
This work was supported by The European Union seventh Frame-
work Programme (FP7/2007-2013) under the grant agreement no
270369 (‘ELFOS’). Moreover, support from the Lundbeck Founda-
tion is acknowledged, and we are grateful to Mr. Dennis Larsen for
the recording of MS.
To a mixture of the dialkyne 5 (50 mg, 0.072 mmol), thione
4 (105 mg, 0.214 mmol), PdCl2(PPh3)2 (5 mg, 0.0072
mmol), and CuI (1.4 mg, 0.0072 mmol) was added a
degassed solution of THF (7 mL) and Et3N (0.1 mL). The
reaction was stirred for 2 d during which time a red colored
precipitate formed. The solvent was removed, and the
residue was purified by flash column chromatography (SiO2)
initially with CH2Cl2 as eluent to remove some impurities
and unreacted 4, then a gradient of 1–20% EtOAc was added
to the eluent mixture to get the major orange/red band, which
afforded 1 as an orange-red colored solid (61 mg, 60%).
Characterization data are in accordance to previously
reported data.3
Supporting Information for this article is available online at
http://www.thieme-connect.com/ejournals/toc/synthesis.SnuIomprifgtooatrinSugpIoi
n
nfomartit
References and Notes
(1) Fabre, J. M. Chem. Rev. 2004, 104, 5133.
(2) (a) Leriche, P.; Roquet, S.; Pillerel, N.; Mabon, G.; Frère, P.
Tetrahedron Lett. 2003, 44, 1623. (b) Nielsen, M. B.;
Gisselbrecht, J.-P.; Thorup, N.; Piotto, S. P.; Boudon, C.;
Gross, M. Tetrahedron Lett. 2003, 44, 6721. (c) Andersson,
A. S.; Qvortrup, K.; Torbensen, E. R.; Mayer, J.-P.; Boudon,
C.; Gross, M.; Kadziola, A.; Kilså, K.; Nielsen, M. B. Eur.
J. Org. Chem. 2005, 3660. (d) Iwamoto, S.; Watanabe, S.;
(10) (a) Sallé, M.; Belyasmine, A.; Gorgues, A.; Jubault, M.;
Soyer, N. Tetrahedron Lett. 1991, 32, 2897. (b) Formigué,
M.; Johannsen, I.; Boubekeur, K.; Nelson, C.; Batail, P.
J. Am. Chem. Soc. 1993, 115, 3752.
(11) Synthesis of 8
A mixture of terephthalaldehyde 6 (100 mg, 0.74 mmol),
thione 7 (673 mg, 2.98 mmol), and P(OEt)3 (4 mL) was
Synlett 2013, 24, 231–235
© Georg Thieme Verlag Stuttgart · New York

LETTER
Extended Tetrathiafulvalenes by Phosphite-Mediated Couplings
235
heated to 100 °C under an argon atmosphere for 2 h. The
15.10, 0.23, 0.09. IR (ATR): ν = 2958 (s), 2923 (m), 2151 (s,
C≡C), 1694 (w), 1558 (vs), 1494 (s), 1474 (m), 1445 (m),
1402 (m), 1374 (m) cm–1. HRMS (ESI+): m/z calcd for
reaction mixture was then allowed to cool to r.t., and the
yellow precipitate was isolated and washed thoroughly with
MeOH (100 mL) to provide the product as yellow crystals
(286 mg, 79%); mp 164–165 °C. 1H NMR (500 MHz,
CDCl3): δ = 7.20 (s, 4 H), 6.45 (s, 2 H), 2.44 (s, 6 H), 2.43
(s, 6 H). 13C NMR (125 MHz, CDCl3): δ = 133.88, 131.87,
127.50, 127.06, 124.54, 114.66, 19.19, 19.07. MS
+
C50H65S8Si4 : 1033.1924; found: 1033.1901 [MH+].
(b) Synthesis of 15
Compounds 11 (0.22 g, 0.69 mmol) and 13 (0.64 g, 2.06
mmol) were dissolved in dry degassed P(OEt)3 (4 mL, 18
mmol). The mixture was stirred under argon at 100 °C for 5
h and then allowed to cool to r.t. The solvent was removed
under reduced pressure at 60 °C, and the crude residue was
subjected to flash column chromatography (SiO2, 10%
toluene in heptane) to give the product 15 as a red solid (67
mg, 17%); mp 188–190 °C (slight color change from ca.
110 °C). 1H NMR (500 MHz, CDCl3): δ = 7.82 (s, 2 H), 7.63
(s, 2 H) 7.39 (s, 2 H) 6.91 (s, 2 H) 2.85 (t, J = 7.4 Hz, 4 H),
2.85 (t, J = 7.4 Hz, 4 H), 1.68–1.61 (m, 8 H), 1.47 (q, J = 7.4
Hz, 4 H), 1.44 (q, J = 7.4 Hz, 4 H), 0.94 (t, J = 7.4 Hz, 6 H),
(MALDI): m/z = 490 [M+]. Anal. Calcd (%) for C18H18S8: C,
44.04; H, 3.70. Found: C, 44.02; H, 3.57.
(12) Synthesis of 10
A mixture of 9 (80.2 mg, 0.49 mmol) and thione 7 (1.01 g,
4.45 mmol) in dry degassed P(OEt)3 (5 mL) was stirred at
110 °C for 4 d. The mixture was then concentrated under
reduced pressure. The residue was subjected to dry column
vacuum chromatography (SiO2, heptane to heptane–EtOAc
= 4:1, 5% increase per fraction) to provide the product as a
brown solid (68 mg, 20%). 1H NMR (500 MHz, CDCl3): δ =
6.85 (s, 3 H), 6.46 (s, 3 H), 2.44 (s, 18 H). 13C NMR (125
MHz, CDCl3): δ = 136.85, 133.22, 127.20, 124.71, 122.70,
114.50, 19.29, 19.08. HRMS (ESI+): m/z calcd for
0.94 (t, J = 7.4 Hz, 6 H), 0.35 (s, 18 H), 0.27 (s, 18 H). 13
NMR (125 MHz, CDCl3): δ = 136.57, 136.14, 135.84,
128.65, 128.53, 128.43, 126.62, 125.04, 122.59, 121.40,
C
111.36, 103.03, 103.00, 101.74, 101.19, 36.16, 35.89, 31.94,
31.85, 21.84, 21.82, 13.81, 13.77, 0.20, 0.06. IR (ATR): ν =
2957 (vs), 2928 (s), 2871 (m), 2150 (s, C≡C), 1696 (w), 1672
(w), 1553 (vs), 1492 (s), 1464 (m), 1402 (m), 1340 (vw) cm–
C24H24S12+: 695.8521; found: 695.8496 [M+].
(13) Sørensen, J. K.; Vestergaard, M.; Kadziola, A.; Kilså, K.;
Nielsen, M. B. Org. Lett. 2006, 8, 1173.
(14) Le Narvor, N.; Robertson, N.; Wallace, E.; Kilburn, J. D.;
Underhill, A. E.; Bartlett, P. N.; Webster, M. J. Chem. Soc.,
Dalton Trans. 1996, 823.
+
1. HRMS (ESI+): m/z calcd for C58H81S8Si4 : 1145.3176;
found: 1145.3116 [MH+]. Anal. Calcd (%) for C58H80S8Si4:
C, 60.78; H, 7.04. Found: C, 60.26; H, 6.94.
(16) Ramirez, F.; Bhatia, S. B.; Smith, C. P. Tetrahedron 1967,
23, 2067.
(15) (a) Synthesis of 14
Compounds 11 (0.30 g, 0.92 mmol) and 12 (0.92 g, 3.62
mmol) were dissolved in P(OEt)3 (5 mL, 29 mmol). The
mixture was stirred under argon at 100 °C for 6 h. The
mixture was allowed to cool to r.t. and was then poured into
MeOH (100 mL). The product 14 precipitated and was
collected on a filter as a red solid (130 mg, 27%); mp 150–
170 °C (decomp.). 1H NMR (500 MHz, CDCl3): δ = 7.82 (s,
2 H), 7.63 (s, 2 H), 7.39 (s, 2 H), 6.91 (s, 2 H), 2.90 (q, J =
7.4 Hz, 4 H), 2.88 (q, J = 7.4 Hz, 4 H) 1.36 (t, J = 7.4 Hz, 6
H), 1.34 (t, J = 7.4 Hz, 6 H), 0.36 (s, 18 H), 0.28 (s, 18 H).
13C NMR (125 MHz, CDCl3): δ = 136.62, 136.03, 135.98,
128.79, 128.70, 128.48, 126.75, 125.09, 122.66, 121.52,
111.52, 103.11, 103.07, 101.81, 101.25, 30.72, 30.47, 15.20,
(17) Arbuzov, A.; Zoroastrova, V. M. Izv. Akad. Nauk. U.S.S.R.,
Otd. Khim. Nauk 1960, 1030; Chem. Abstr. 1960, 54,
24627g.
(18) (a) Ramirez, F.; Yamanaka, H.; Basedow, O. H. J. Org.
Chem. 1959, 24, 1838. (b) Ramirez, F.; Yamanaka, H.;
Basedow, O. H. J. Am. Chem. Soc. 1961, 83, 173.
(19) Tamura, H.; Shinohara, Y.; Arai, T. Chem. Lett. 2010, 40,
129.
(20) Yamaguchi, S.; Iimura, K.; Tamao, K. Chem. Lett. 1998, 27,
89.
(21) Zhou, N.; Wang, L.; Thompson, D. W.; Zhao, Y.
Tetrahedron 2011, 67, 125.
© Georg Thieme Verlag Stuttgart · New York
Synlett 2013, 24, 231–235