Alternating furanylene-meta-phenylene oligomers: synthesis and photophysics

Article abstract of DOI:10.1016/j.tet.2009.09.077

A range of alternating furanylene-meta-phenylene oligoaryls of different chain lengths is synthesized by a convergent/divergent protocol from the annulation of a propargylic dithioacetal and an aldehyde with a propargylic dithioacetal moiety as a substitu

Full text of DOI:10.1016/j.tet.2009.09.077

Tetrahedron 65 (2009) 9749–9755
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Tetrahedron
journal homepage: www.elsevier.com/locate/tet
Alternating furanylene-meta-phenylene oligomers: synthesis and photophysics
Chih-Ming Chou a, Chih-Hsien Chen a, Cheng-Lan Lin a, Kuang-Wei Yang a, Tsong-Shin Lim b,
,
Tien-Yau Luh a
*
a Department of Chemistry, National Taiwan University, Taipei 106, Taiwan
b Department of Physics, Tung Hai University, Taichung 407, Taiwan
a r t i c l e i n f o
a b s t r a c t
Article history:
A range of alternating furanylene-meta-phenylene oligoaryls of different chain lengths is synthesized by
a convergent/divergent protocol from the annulation of a propargylic dithioacetal and an aldehyde with
a propargylic dithioacetal moiety as a substituent. The emission properties of these oligomers showed
chain-length dependent in poor solvent such as cyclohexane. Time resolved fluorescence spectroscopic
analyses indicate that there might be intramolecular interaction between the chromophores in 2c–e and
such interaction became more prominent as the chain-lengths increased from 9 to 21. Since oligomers 2
have meta-phenylene and 2,5-furnaylene linkages, the oligomers 2e, may likely be folded to enable in-
trachain chromophore–chromophore interactions. In addition, these oligomers are electrochemically
active and the first oxidation potentials are chain-length dependent.
Received 1 August 2009
Received in revised form
12 September 2009
Accepted 18 September 2009
Available online 22 September 2009
Ó 2009 Elsevier Ltd. All rights reserved.
1. nBuLi
2.
1. Introduction
CHO
S
Bu
Bu
S
Bu
Studies on well-defined oligomers with interesting optoelec-
tronic properties remain to be rapidly burgeoning.1 A variety of
structurally sound scaffolds with diverse molecular architectures
has been designed and synthesized. Incorporation of hetero-
aromatic rings into these systems will tune the optoelectronic
properties of the oligomers, and studies on oligothiophenes or
pyrroles and related compounds abound.1,2 Relatively speaking,
investigations on furan-containing oligoaryls have been only
sporadically explored.3–6 Indeed, alternating benzene–furan olig-
omers 1 have been used as efficient hole transporting materials
with good charge mobility in electroluminescent applications.4
These furan containing oligoaryls are found to be stable towards
sunlight in the absence of oxygen (air).4 In addition, the bis-
mercaptan derivatives of alternating benzene–furan oligomers
have been shown to assemble nicely on gold (111) surface
S
S
S
S
O
3. TFA
CO2Me
Bu
MeO2C
S
S
R
O
Bu
n
Bu
Bu
R
O
O
with significant
p–p stacking and conformational dependent
R
conductivities of these oligoaryls by using STM break junction
techniques were also reported.5 Bidirectional iterative or conver-
gent-divergent3b,7 annulation of propargylic dithioacetals (Scheme
1) have been used for the synthesis of a range of these mono-
dispersed alternating benzene–furan oligomers with or without
repetitive units.8
n+1
n+1
Bu
1
Bu
Bu
MeO
OMe
O
O
Incorporation of meta-phenylene moiety into a conjugated
system occasionally acts as interrupting blocks so that the
m
n
2a: m = 0, n = 1; b: m = n = 1; c: m = n = 2; d: m = n = 3; e: m = n = 5
* Corresponding author. Tel.: þ886 2 2363 6299; fax: þ886 2 2364 4971.
E-mail address: tyluh@ntu.edu.tw (T.-Y. Luh).
Scheme 1.
0040-4020/$ – see front matter Ó 2009 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2009.09.077

9750
C.-M. Chou et al. / Tetrahedron 65 (2009) 9749–9755
photophysical properties can be well controlled.9 On the other
hand, the meta-connectivity furnishes a 120ꢀ angle, which can offer
a unique geometry poised to fold upon amalgamation with ap-
propriate linkers. To illustrate this, m-phenylene ethynylene olig-
omers of discrete length have been extensively examined, and their
Sequential treatment of 8 with 1 equiv of nBuLi, 7 and then TFA
afforded 9 in 63% yield. Attempts to oxidize of 9 with DDQ was
unsuccessful, no corresponding aldehyde 10 being obtained. In
a similar manner, 6 was allowed to react with nBuLi, 7 and TFA to
give 11 in 63% yield. Oxidation of 11 with MnO2 produced the 10 in
94% yield. Furan annulation procedure was repeated to couple 9
and 10 to furnish 12 in 52% yield (Scheme 3).
folding behavior through solvophobic
p–p-stacking is well docu-
mented.10–12 The role of linear alkynyl spacer is to limit the
conformational flexibility and, therefore, facilitate the foldability
of the oligomers. Incorporation of six-membered heteroaromatic
linkers, such as pyridine–pyrimidine and related helicity con-
dons, where transoid conformation around the interheterocyclic
bonds is imposed, has been shown to generate molecular he-
lices.13 However, the use of five-membered heteroaromatic ring
as the linker to tether meta-phenylene modules has not been
explored. The folding behavior of these oligomers containing
such five-membered heterocycles would, in general, be difficult
to control. As shown in Scheme 1, our furan annulation protocol
will introduce regioselectively an alkyl substituent at C3 position
of the furan ring. It is envisaged that the size and the nature of
these alkyl group on furan rings may dictate the conformation
of the carbon–carbon bond linking the furan and benzene rings
in furanylene-meta-phenylene oligomers 2, and hence, the
folding character of 2. In this paper, we report the synthesis
and photophysical properties of a series of 2.
S
S
Bu
a
b
8
6
O
Bu
R2
9 R = CH2
OMe
10 R = CHO
11 R = CH2OH
S
c
S
Bu
Bu
O
Bu
d
O
9
O
2. Results and discussion
2.1. Synthesis
MeO
Bu
Propargylic dithioacetal 3 was prepared according to Scheme 2.
Sequential treatment of 1-hexyne with nBuLi and 4 followed by
MnO2 oxidation gave the corresponding ketone 5, which was
dithioacetalized with ethanedithiol in the presence of BF3(OEt2) in
12
n
Scheme 3. Reagents and conditions: (a) (i) BuLi, ꢁ78 ꢀC; (ii) 7; (iii) TFA, Yield of 9:
63%; (b) (i) 2 equiv nBuLi, ꢁ78 ꢀC; (ii) 7; (iii) TFA, Yield of 11: 63%; (c) MnO2, 94%; (d) (i)
nBuLi, ꢁ78 ꢀC; (ii) 10; (iii) TFA, 52%.
By employing the same protocol, pentaaryl dialdehyde 14 was
obtained in 41% overall yield from 6 and isophthaldehyde 15 fol-
lowed by MnO2 oxidation (Scheme 4).
O
S
S
a
b
Bu
Bu
Bu
Bu
Bu
CO2Me
R
a
5
6
R
R
3 R = CO2Me
6 R = CH2OH
7 R = CHO
c
O
O
d
e
8 R = CH2OMe
13 R = CH2OH
14 R = CHO
b
n
Scheme 2. Reagents and conditions: (a) (i) BuLi, THF, ꢁ78 ꢀC; (ii) methyl 3-for-
mylbenzoate (4), THF, ꢁ78 ꢀC, rt; (iii) MnO2, rt, 97%; (b) 1,2-ethanedithiol, BF3(OEt2),
MeOH, ꢁ78 ꢀC to rt, 52%; (c) DIBAL, 97%; (d) MnO2, 92%; (e) NaH, MeI, 94%.
n
Scheme 4. Reagents and conditions: (a) (i) BuLi, ꢁ78 ꢀC; (ii) isophthaldehyde (15);
(iii) TFA, 43%; (b) MnO2, 95%.
Annulation using different combinations of propargylic
dithioacetals 8, 9, or 12, and 3-methoxymethylbenzaldehyde (16)
or 14 or 15 afforded the corresponding alternating furanylene-
meta-phenylene oligomers 2 and results are summarized in Table 1.
methanol to afford 3 in overall 50% yield. DIBAL reduction of 3 gave
97% yield of 6, which was oxidized with MnO2 to furnish aldehyde 7
in 92% yield. Methyl ether 8 was obtained from the reaction of 6
with NaH and MeI.
Table 1
Photophysical and electrochemical parameters of alternating furanylene-meta-phenylene oligomers 2
sc (ps)
E1p/2d (mV)
a
b
Dithioacetal
RCHO
2 (%yield)
lmax (nm)
lem (nm) (Ff
)
lemc (nm)
8
8
9
9
16
15
15
14
14
2a (65)
2b (55)
2c (35)
2d (20)
2e (40)
326
334
336
337
340
363, 382(0.87)
371, 386(0.55)
373, 389(0.23)
374, 392(0.54)
376, 392(0.65)
359, 378
363, 381
369, 387
371, 388
396
1350
1400
1350, 200(1.5%)
1350, 200(6.5%)
1350, 210(24%)
669
669
619
548
518
12
a
Absorption and fluorescence spectra were acquired at 10ꢁ5 M in CHCl3, unless otherwise specified.
b
c
The quantum yield was determined in EtOAc (2a–e) by employing coumarin-1 (Ff ¼ 0.99 in EtOAc)14 as the reference.
Measured in cyclohexane.
d
Measured by differential pulse voltammetry with referenced to the Cp2Fe/Cp2Feþ couple.

C.-M. Chou et al. / Tetrahedron 65 (2009) 9749–9755
9751
2.2. Photophysical investigations
(a)
1.0
The absorption and emission spectra of 2 are shown in Figure. 1
and the relevant spectroscopic data are summarized in Table 1. The
absorption maxima showed bathochromic shift from 2a to 2b and
almost reached the plateau as the chain lengths further increased
from 2c to 2e. No significant solvent effects were recorded in these
absorption properties, whereas the emission profiles were solvent
dependent. As shown in Figure 1b, lem in CHCl3 exhibited slightly
bathochromic shift as the chain lengths increased from 2a to 2e and
the spectra were structured. When cyclohexane was employed as
the solvent, the emission curves for 2 were perturbed and differ-
ences in lem became more apparent. In particular, the spectrum for
2d was less structured and that for 2e was structureless (Fig. 1c). It
is noteworthy that the emission profile of 2e in cyclohexane was
concentration independent.
0.8
0.6
0.4
0.2
0.0
300
325
350
375
400
Wavelength (nm)
The temperature dependent emission spectra of 2e in hexane
are shown in Figure. 1d. The lem shifted reversibly from 396 nm at
300 K to 407 nm at 220 K. Such slight bathochromic shifts suggest
that there might be persistent chromophore–chromophore in-
teraction in 2e in nonpolar solvent such as hexane. Structurally,
oligomers 2 have meta-phenylene and 2,5-furnaylene linkages.
Oligomer 2e might be expected to be somewhat folded.
(b)
1.0
0.8
0.6
0.4
0.2
0.0
Time resolved fluorescence spectroscopy was used to study the
lifetimes (s) of emission decay and the results are also outlined in
Table 1. Single exponential decay was observed for 2a and 2b and the
lifetimes were comparable. These results suggest that little con-
jugative interactions through meta-phenylene linkage might occur.
For oligoaryls with longer chain lengths, two parameters were
employedto fitthe fluorescencedecay. The longerlifetimes (1350 ps),
which were comparable with that observed for 2a, was attributed to
the decay of diphenylfuran module. The shorter lifetimes (ca. 200 ps)
were found in the emission of 2c–2e. These fast decay may be arisen
from the quenching due to chromophore–chromophore interactions.
Since the emission profiles were essentially concentration in-
dependent, it seemed likely that such interactions might occur
intramolecularly. In other words, as the chain lengths increased, the
chances for the diphenylfuran chromophores to meet through
space might be enhanced in poor solvent like cyclohexane. The fact
that the weight contribution of the short-life decay increased with
increasing chain lengths would be consistent with the folding
characters of furanylene-meta-phenylene oligomers.
350
375
400
425
450 475
500
525
550
Wavelength (nm)
(c)
1.0
0.8
0.6
0.4
0.2
0.0
2.3. Electrochemical investigations
Differential pulse voltammetry was employed to elucidate the
oxidation behavior of 2 and the potentials were reported against
Cp2Fe/Cp2Feþ pair (Fig. 2). It is interesting to note that, as the number
of furan moieties in 2 increases, the number of oxidation steps also
increased. Thus, only one oxidation wave at 669 mV was observed for
2a. Oligomer 2b exhibited two oxidation waves at 669 and 890 mV.
The same first oxidation potentials for 2a and 2b indicate that the
extension of aryl chain at the meta-linkage might play little role in the
electrochemical oxidation. Four electron transfer processes at 619,
719, 820, and 952 mV were clearly found for 2c, which contains four
furan moieties. The first oxidation for 2c shifted 50 mV towards more
negative potential in comparison with that for 2b. In addition, the
differencesinpotentialsbetweenthe each electron transferprocesses
for 2c were much smaller than that for 2b. In a similar manner, the
first oxidation potentials for 2d (containing six furan rings) appeared
at 548 mV, which was more negative than that of 2c. Three additional
sequential oxidation processes at 618, 756, and 860 mV were ob-
served and the separation between each oxidation steps was in the
range of 70–130 mV. As to 2e having ten furan rings, no discrete ox-
idation potentials besides the first one at 518 mV were clearly iden-
tified. Again, the first oxidation for 2e required 30 mV less than that
350
375 400
425 450
475 500
525 550
Wavelength (nm)
(d)
300K
260K
220K
= 396 nm
1.0
0.8
0.6
0.4
0.2
0.0
λ
λ
λ
em
em
em
= 403 nm
= 407 nm
350
375
400
425
450
475
500
525
550
Wavelength (nm)
Figure 1. Absorption and emission spectra (excitation at lmax) of 2 (a, red, b, green, c,
orange, d, blue and e, black) in (a, b) chloroform, (c) cyclohexane, and (d) Variable
temperature emission spectra of 2e in hexane (lex, 331 nm).

9752
C.-M. Chou et al. / Tetrahedron 65 (2009) 9749–9755
then slowly warmed to rt and further stirred for 2 h. The mixture
1.2x10-5
8.0x10-6
2a
2b
2c
2d
was quenched with saturated NH4Cl (500 mL), and the organic
layer was separated. The aqueous layer was extracted with Et2O
(300 mLꢂ3). The combined organic extracts were dried (MgSO4),
filtered, and evaporated in vacuo to afford the crude alcohol, which
was taken in CH2Cl2 (300 mL). The solution was added slowly to
4.0x10-6
0.0
1.2x10-5
8.0x10-6
4.0x10-6
0.0
a
suspension of activated MnO2 (170 g, 1.95 mol) in CH2Cl2
(500 mL) at rt and the mixture was stirred for 6 h. After passing
through silica gel bed (5 cm) and washing with EtOAc
1.2x10-5
8.0x10-6
a
4.0x10-6
0.0
(300 mLꢂ5), the combined filtrate was evaporated in vacuo to af-
ford 5 as an orange oil (77.0 g, 97%): 1H NMR (400 MHz, CDCl3)
1.2x10-5
8.0x10-6
d
0.90 (t, J¼7.3 Hz, 3H), 1.46 (sext, J¼7.3 Hz, 2H), 1.60 (tt, J¼7.3,
4.0x10-6
0.0
7.1 Hz, 2H), 2.46 (t, J¼7.1 Hz, 2H), 3.88 (s, 3H), 7.49 (t, J¼7.8 Hz, 1H),
8.17 (d, J¼7.8 Hz, 1H), 8.22 (d, J¼7.8 Hz, 1H), 8.69 (s, 1H); 13C NMR
1.2x10-5
2e
8.0x10-6
(100 MHz, CDCl3) d 13.7,19.1, 22.2, 29.8, 52.5, 79.4, 97.9,128.6, 130.5,
4.0x10-6
0.0
130.7, 133.1, 134.4, 137.0, 165.9, 177.0; IR (KBr)
n 2957, 2872, 1728,
1649, 1601, 1431, 1303, 1234, 1127, 923, 718 cmꢁ1; HRMS (FAB) calcd
0.4
0.5
0.6
0.7
0.8
Potential / V (vs. Fc/Fc+)
0.9
1.0
1.1
for C15H17O3 (MþþH): 245.1178; found: 245.1171.
4.1.2. 2-(2-Hex-1-ynyl)-2-(3-methoxycarbonylphenyl)-1,3-dithio-
lane (3). To a solution of 5 (77.0 g, 0.32 mol) in MeOH (500 mL) was
added BF3$Et2O (41.0 mL, 0.32 mol) and 1,2-ethanedithiol (27.0 mL,
0.32 mol) at ꢁ78 ꢀC. The mixture was slowly warmed to rt and
stirred for 12 h. After quenching with NaOH (10%, 300 mL), the or-
ganic layer was separated. The aqueous layer was extracted with
CH2Cl2 (200 mLꢂ3). The combined organic extracts were washed
with 10% NaOH (300 mLꢂ5), brine (300 mL), dried (MgSO4), filtered,
and evaporated in vacuo. The resulting residue was purified by flash
column chromatography (silica gel, CH2Cl2/hexane¼2/3) to afford 3
Figure 2. Differential pulse voltammograms of 2 (1 mM) in CH2Cl2 containing 0.1 M
Bu4NPF6. Scan rate¼5 mV sꢁ1
.
for 2d. The trend of decreasing first oxidation potentials from 2b to 2e
was interesting.
From the resonance point of view, furan moiety can be consid-
ered as an electron donating substituent with a negative Hammett
sþ value (–0.39).15 The presence of multiple furan moieties in the
oligomer chain may raise the corresponding HOMO energies so that
the oxidation would be easier as the chain length increased. Since
meta-phenylene linker can be considered essentially as an in-
sulator, no conjugation through this spacer being take place. The
diphenylfuran modules in the oligoaryls would be more or less
independent. Accordingly, the second oxidation might be easier as
the chain lengths of 2 became longer, because the electrostatic
interactions might be reduced. Similar situation might be expected
in further oxidation potentials.
as a pale yellow oil (53.4 g, 52%): 1H NMR (400 MHz, CDCl3)
d 0.91 (t,
J¼7.3 Hz, 3H),1.45 (sext, J¼7.3 Hz, 2H),1.56 (tt, J¼7.3, 7.0 Hz, 2H), 2.35
(t, J¼7.0 Hz, 2H), 3.64–3.70 (m, 4H), 3.89 (s, 3H), 7.38 (t, J¼7.8 Hz,1H),
7.93 (d, J¼7.8 Hz, 1H), 8.11 (d, J¼7.8 Hz, 1H), 8.59 (s, 1H); 13C NMR
(100 MHz, CDCl3)
d 14.4, 19.6, 22.7, 31.3, 42.0, 52.6, 62.1, 82.1, 88.9,
128.1, 128.8, 129.3, 130.0, 132.1, 140.2, 166.3; IR (KBr)
n 2954, 2929,
2870, 1724, 1437, 1275, 1203, 1141, 1104, 1082, 733, 690 cmꢁ1; HRMS
(FAB) calcd for C17H21O2S2 (MþþH): 321.0983; found: 321.0976.
3. Conclusions
4.1.3. 2-(2-Hex-1-ynyl)-2-(3-hydroxymethylphenyl)-1,3-dithiolane
(6). To a THF solution (120 mL) of 3 (10.7 g, 33.5 mmol), stirred
under N2 atmosphere, was added DIBAL (150.0 mL, 1.0 M in hexane
0.15 mol) slowly at 0 ꢀC and the reaction mixture was stirred for 2 h
at rt, quenched by slowly pouring into saturated NH4Cl (50 mL).
After the remaining DIBAL was completely quenched, the gel-like
organic layer was acidified with 6 M HCl (200 mL), and extracted
with EtOAc (100 mLꢂ3). The combined organic extracts were
washed with saturated NaHCO3 (150 mLꢂ2), brine (200 mL), dried
(MgSO4), filtered, and evaporated in vacuo to afford 6 as a pale
In summary, we have documented the synthesis and photo-
physical studies of a range of oligoaryls having alternating 2,5-
furanylene-meta-phenylene modules by convergent/divergent
approach from the corresponding propargylic dithioacetals. The
emissionproperties showed chain-length dependent. Time resolved
fluorescence spectroscopic analyses indicate that there might be
intramolecular interaction between the chromophores in 2c–e and
such interaction became more prominent as the chain-lengths in-
creased from 9 to 21. Because oligomers 2 have meta-phenylene and
2,5-furnaylene linkages, it seems likely that the oligomers 2e, in
particular, may be somewhat folded to enable intrachain chromo-
phore–chromophore interactions. Electrochemical behavior
showed that the first oxidation will gradually shift toward more
negative potentials as the chain-length grows. In addition, the dif-
ferences in potentials in the first and the second oxidation steps
appeared to decrease with the increase in chain-length.
yellow oil (9.4 g, 97%): 1H NMR (400 MHz, CDCl3)
d
0.93 (t, J¼7.2 Hz,
3H), 1.45 (sext, J¼7.2 Hz, 2H), 1.56 (tt, J¼7.2, 7.0 Hz, 2H), 2.35 (t,
J–7.0 Hz, 2H), 3.63–3.73 (m, 4H), 4.67 (d, J¼6.0 Hz, 2H), 7.27–7.34
(m, 2H), 7.85 (d, J¼8.0 Hz, 1H), 7.92 (s, 1H); 13C NMR (100 MHz,
CDCl3)
d 14.0, 19.3, 22.4, 31.0, 41.4, 62.3, 65.3, 82.3, 88.1, 125.7, 126.3,
126.6, 127.9, 139.6, 140.4; IR (KBr)
n
3363, 2956, 2927, 2869, 1601,
1580, 1482, 1460, 1430, 1275, 1177, 1018, 745, 698, 648 cmꢁ1; HRMS
(FAB) calcd for C16H21OS2 (MþþH): 293.1034; found: 293.1032;
Anal. Calcd for C16H20OS2: C 65.71, H 6.89; found: C 65.32, H 6.96.
4. Experimental
4.1. General
4.1.4. 2-(2-Hex-1-ynyl)-2-(3-formylphenyl)-1,3-dithiolane (7). A so-
lution of alcohol 6 (11.6 g, 40 mmol) in CH2Cl2 (100 mL) was added
slowly to a suspension of activated MnO2 (34.7 g, 400 mmol) in
CH2Cl2 (150 mL) at rt. The reaction mixture was stirred for 6 h at rt.
After passing through a silica gel bed (5 cm) and washing with
EtOAc (100 mLꢂ5), the combined filtrate was evaporated in vacuo
to afford 7 as a pale yellow oil (10.7 g, 92%): 1H NMR (400 MHz,
4.1.1. 3-Hept-2-ynoyl-benzoic acid methyl ester (5). To a solution of
1-hexyne (37.0 mL, 0.32 mol) in THF (200 mL), stirred under N2
atmosphere, was slowly added nBuLi (132.0 mL of 2.5 M solution in
hexane, 0.33 mol) at ꢁ78 ꢀC. The reaction mixture was stirred for
30 min. Then a solution of 4 (53.0 g, 0.32 mol) in THF (400 mL) was
added slowly and the mixture was stirred for 30 min at ꢁ78 ꢀC,
CDCl3)
d
0.92 (t, J¼7.3 Hz, 3H), 1.44 (sext, J¼7.3 Hz, 2H), 1.56 (tt,

C.-M. Chou et al. / Tetrahedron 65 (2009) 9749–9755
9753
J¼7.3, 7.0 Hz, 2H), 2.36 (t, J¼7.0 Hz, 2H), 3.66–3.73 (m, 4H), 7.48 (t,
J¼7.7 Hz, 1H), 7.78 (d, J¼7.7 Hz, 1H), 8.19 (d, J¼7.7 Hz, 1H), 8.43 (s,
1H), 10.01 (s, 1H); 13C NMR (100 MHz, CDCl3)
14.6, 19.8, 22.9, 31.4,
42.2, 62.1, 82.0, 89.3, 128.9, 129.2, 129.5, 133.8, 136.3, 141.3, 191.5; IR
129.0, 130.7, 131.3, 136.3, 139.5, 148.0, 149.8, 191.3; IR (KBr)
n
2955,
2927, 2859, 2729, 1698, 1666, 1463, 1453, 1161, 794, 692 cmꢁ1
;
d
HRMS (FAB) calcd for C30H32O2S2: 488.1844; found: 488.1833.
(KBr)
n
2956, 2929, 2860, 2725, 1700, 1596, 1581, 1431, 1379, 1277,
4.1.8. Dithioacetal (11). Under argon, nBuLi (0.88 mL, 2.5 M in
hexane, 2.2 mmol) was introduced dropwise to a solution of 6
(290 mg, 1.0 mmol) in THF (30 mL) at ꢁ78 ꢀC and the mixture was
stirred at ꢁ78 ꢀC for 70 min. A solution of 7 (270 mg, 0.93 mmol) in
THF (10 mL) was added at ꢁ78 ꢀC and the mixture was stirred at
ꢁ78 ꢀC for 1 h, then gradually warmed to rt. After further stirring
for 3 h at rt, TFA (0.27 mL, 3.0 mmol) was added and the mixture
was stirred at rt overnight. The reaction mixture was quenched
with saturated NH4Cl (50 mL), and the organic layer was separated.
The aqueous layer was extracted with EtOAc (20 mLꢂ3). The
combined organic extracts were washed with saturated NaHCO3
(20 mLꢂ3), brine (30 mL), dried (MgSO4), filtered and evaporated in
vacuo. The crude product was purified by flash column chroma-
tography (CHCl3) to give 11 as a pale yellow oil (308 mg, 63%): 1H
1239, 1176, 1164, 1117, 807, 747, 685, 650 cmꢁ1; HRMS (FAB) calcd
for C16H19OS2 (MþþH): 291.0877; found: 291.0875.
4.1.5. 2-(Hex-1-ynyl)-2-(3-methoxymethylphenyl)-1,3-dithiolane
(8). To a suspension of NaH (60% dispersion in mineral oil, 0.20 g,
4.9 mmol prewashed with hexane) in THF (20 mL) was introduced
a THF solution (10 mL) of 7 (0.96 g, 3.3 mmol) at rt under N2 at-
mosphere. After 1 h of stirring, MeI (0.4 mL, 6.6 mmol) was added
and the mixture was stirred for 3 h at rt, poured into saturated
NH4Cl (50 mL) and extracted with CH2Cl2 (20 mLꢂ3). The com-
bined organic extracts were washed with brine (100 mL), dried
(MgSO4), filtered, and evaporated in vacuo to afford 8 as a pale
yellow oil (0.95 g, 94%): 1H NMR (300 MHz, CDCl3)
d 0.92 (t,
J¼7.2 Hz, 3H), 1.44 (sext, J¼7.2 Hz, 2H), 1.56 (tt, J¼7.2, 7.0 Hz, 2H),
2.36 (t, J¼7.0 Hz, 2H), 3.37 (s, 3H), 3.63–3.71 (m, 4H), 4.46 (s, 2H),
7.23–7.33 (m, 2H), 7.85 (d, J¼7.8 Hz, 1H), 7.89 (s, 1H); 13C NMR
NMR (400 MHz, CDCl3)
d
0.92 (t, J¼7.2 Hz, 3H), 0.98 (t, J¼7.2 Hz,
3H), 1.43–1.52 (m, 4H), 1.58–1.63 (m, 2H), 1.65–1.74 (m, 2H), 2.08–
2.16 (br, 1H), 2.38 (t, J¼7.4 Hz, 2H), 2.73 (t, J¼7.8 Hz, 2H), 3.66–3.77
(m, 4H), 4.72 (s, 2H), 6.69 (s, 1H), 7.23 (d, J¼8.0 Hz, 1H), 7.37 (t,
J¼8.0 Hz, 1H), 7.42 (t, J¼8.0 Hz, 1H), 7.65 (d, J¼8.0 Hz, 1H), 7.70 (s,
1H), 7.88 (d, J¼8.0 Hz, 1H), 8.29 (s, 1H); 13C NMR (100 MHz, CDCl3)
(100 MHz, CDCl3)
d 14.1, 19.3, 22.4, 31.0, 41.4, 58.3, 62.2, 74.5, 82.2,
88.0, 126.5, 126.6, 127.1, 127.8, 137.6, 139.1; R (KBr)
n 2955, 2926,
2869, 2819, 1652, 1558, 1540, 1456, 1429, 1375, 1361, 1275, 1191,
1102, 963, 890, 790, 746, 696 cmꢁ1; HRMS (FAB) calcd for C17H23OS2
(MþþH): 307.1190; found: 307.1193.
d
13.7, 14.1, 19.0, 22.2, 22.7, 25.9, 30.8, 32.2, 41.3, 62.2, 65.1, 82.1, 88.1,
109.4, 121.9, 122.7, 124.2, 124.7, 125.0, 125.5, 125.8, 128.2, 128.7,
130.8, 131.2, 139.7, 141.1, 147.5, 151.4; IR (KBr)
n 3376, 2956, 2927,
4.1.6. Dithioacetal (9). Under argon, nBuLi (0.88 mL, 2.5 M in hex-
ane, 2.2 mmol) was introduced dropwise to a solution of 8 (0.61 g,
2.0 mmol) in THF (50 mL) at ꢁ78 ꢀC and the mixture was stirred at
ꢁ78 ꢀC for 50 min. A solution of 7 (0.57 g, 2.0 mmol) in THF (10 mL)
was added at ꢁ78 ꢀC and the mixture was stirred at ꢁ78 ꢀC for 1 h,
then gradually warmed to rt. After further stirring for 1 h at rt, TFA
(0.3 mL, 3.3 mmol) was added and the mixture was stirred at rt
overnight. The reaction mixture was quenched with saturated
NH4Cl (50 mL), and the organic layer was separated. The aqueous
layer was extracted with EtOAc (20 mLꢂ3). The combined organic
extracts were washed with saturated NaHCO3 (20 mLꢂ3), brine
(30 mL), dried (MgSO4), filtered and evaporated in vacuo. The crude
product was purified by flash column chromatography (silica gel,
CH2Cl2/hexane¼1/4) to give 9 as a pale yellow oil (845 mg, 65%): 1H
2869, 1597, 1464, 1378, 1265, 1199, 1024, 788, 738, 699 cmꢁ1; HRMS
(FAB) calcd for C30H34O2S2: 490.2000; found: 490.1996.
4.1.9. Dithioacetal (12). Under argon, nBuLi (0.44 mL, 2.5 M in
hexane, 1.1 mmol) was introduced dropwise to a solution of 9
(520 mg, 1.03 mmol) in THF (40 mL) at ꢁ78 ꢀC and the mixture was
stirred at ꢁ78 ꢀC for 50 min. A solution of 10 (439 mg, 0.9 mmol) in
THF (10 mL) was added at ꢁ78 ꢀC and the mixture was stirred at
ꢁ78 ꢀC for 1 h, then gradually warmed to rt. After further stirring
for 1 h at rt, TFA (0.18 mL, 2.0 mmol) was added and the mixture
was stirred at rt overnight. The reaction mixture was quenched
with saturated NH4Cl (50 mL), and the organic layer was separated.
The aqueous layer was extracted with EtOAc (30 mLꢂ3). The
combined organic extracts were washed with saturated NaHCO3
(20 mLꢂ3), brine (30 mL), dried (MgSO4), filtered and evaporated in
vacuo. The crude product was purified by flash column chroma-
tography (silica gel, ether/hexane¼1/4) to give 12 as a pale yellow
NMR (400 MHz, CDCl3)
d
0.91 (t, J¼7.2 Hz, 3H), 0.96 (t, J¼7.2 Hz,
3H), 1.40–1.46 (m, 4H), 1.48–1.61 (m, 2H), 1.62–1.71 (m, 2H), 2.38 (t,
J¼7.4 Hz, 2H), 2.71 (t, J¼7.8 Hz, 2H), 3.41 (s, 3H), 3.69–3.72 (m, 4H),
4.49 (s, 2H), 6.67 (s, 1H), 7.21 (d, J¼7.8 Hz, 1H), 7.35–7.41 (m, 2H),
7.61–7.66 (m, 3H), 7.82 (d, J¼7.8 Hz, 1H), 8.26 (s, 1H); 13C NMR
oil (468 mg, 52%): 1H NMR (400 MHz, CDCl3)
d
0.91 (t, J¼7.2 Hz, 3H),
0.91–1.27 (m, 9H), 1.43–1.63 (m, 8H), 1.63–1.68 (m, 2H), 1.68–1.80
(m, 6H), 2.38 (t, J¼7.0 Hz, 2H), 2.74–2.81 (m, 6H), 3.44 (s, 3H), 3.65–
3.77 (m, 4H), 4.52 (s, 2H), 6.71 (s, 1H), 6.73 (s, 1H), 6.75 (s, 1H), 7.24
(d, J¼8.0 Hz, 1H), 7.37–7.50 (m, 4H), 7.60–7.72 (m, 7H), 7.87 (d,
J¼7.6 Hz, 1H), 8.05 (s, 2H), 8.31 (s, 1H); 13C NMR (100 MHz, CDCl3)
(100 MHz, CDCl3)
d 14.1, 14.5, 19.4, 22.5, 23.1, 26.2, 31.1, 32.5, 41.5,
58.3, 62.3, 74.6, 82.1, 88.1, 109.3, 122.57, 122.63, 124.0, 124.5, 124.9,
125.6, 126.1, 128.0, 128.3, 130.5, 131.1, 138.1, 139.4, 147.3, 151.2; IR
(KBr)
HRMS (FAB) calcd for C31H36O2S2: 504.2157; found: 504.2163.
n ;
2955, 2927, 2859, 1597, 1455, 1194, 1102, 787, 695 cmꢁ1
d
14.1, 14.47, 14.51, 19.4, 22.5, 23.05, 23.11, 26.2, 31.1, 32.51, 32.54,
41.5, 58.3, 62.4, 74.6, 82.1, 88.1, 109.28, 109.34, 120.4, 121.8, 122.6,
122.7, 124.0, 124.1, 124.5, 124.8, 125.7, 126.2, 128.0, 128.4, 128.5,
128.6, 130.5, 130.60, 130.65, 131.1, 131.6, 138.2, 139.5, 147.3, 147.4,
4.1.7. Dithioacetal (10). A solution of alcohol 11 (490 mg, 1.0 mmol)
in CH2Cl2 (20 mL) was added slowly to a suspension of activated
MnO2 (867 mg, 10.0 mmol) in CH2Cl2 (10 mL) at rt. The reaction
mixture was stirred for 6 h at rt. After passing through a silica gel
bed (5 cm) and washing with EtOAc (10 mLꢂ5), the combined fil-
trate was evaporated in vacuo to afford aldehyde 10 as a pale yellow
151.2, 151.3; IR (KBr)
n 2955, 2928, 2869, 1597, 1465, 1378, 1275,
1194, 1103, 958, 889, 788, 753, 696 cmꢁ1; HRMS (FAB) calcd for
C59H64O4S2: 900.4246; found: 900.4258.
oil (458 mg, 94%): 1H NMR (400 MHz, CDCl3)
d
0.90 (t, J¼7.2 Hz, 3H),
4.1.10. Bismethanol (13). Under argon, nBuLi (4.4 mL, 2.5 M in
hexane, 11.0 mmol) was introduced dropwise to a solution of 6
(1.45 g, 5.0 mmol) in THF (150 mL) at ꢁ78 ꢀC and the mixture was
stirred at ꢁ78 ꢀC for 50 min. A solution of 15 (301 mg, 2.25 mmol)
in THF (20 mL) was added at ꢁ78 ꢀC and the mixture was stirred at
ꢁ78 ꢀC for 1 h, then gradually warmed to rt. After further stirring
for 3 h at rt, TFA (1.35 mL, 15.0 mmol) was added and the mixture
was stirred at rt overnight. The reaction mixture was quenched
0.96 (t, J¼7.6 Hz, 3H), 1.40–1.50 (m, 4H), 1.55–1.61 (m, 2H), 1.62–
1.72 (m, 2H), 2.39 (t, J¼7.0 Hz, 2H), 2.72 (t, J¼7.8 Hz, 2H), 3.66–3.77
(m, 4H), 6.76 (s, 1H), 7.41 (t, J¼7.8 Hz, 1H), 7.53 (t, J¼7.8 Hz, 1H), 7.63
(d, J¼7.8 Hz, 1H), 7.73 (d, J¼7.8 Hz, 1H), 7.86 (d, J¼7.8 Hz, 1H), 7.94
(d, J¼7.8 Hz, 1H), 8.17 (s, 1H), 8.27 (s, 1H), 10.04 (s, 1H); 13C NMR
(100 MHz, CDCl3)
d 14.1, 14.5, 19.3, 22.5, 23.0, 26.1, 31.1, 32.4, 41.5,
62.3, 82.1, 88.2, 110.3, 124.2, 124.6, 125.0, 126.0, 127.8, 128.1, 128.7,

9754
C.-M. Chou et al. / Tetrahedron 65 (2009) 9749–9755
with saturated NH4Cl (50 mL), and the organic layer was separated.
The aqueous layer was extracted with EtOAc (50 mLꢂ3). The
combined organic extracts were washed with saturated NaHCO3
(50 mLꢂ3), brine (50 mL), dried (MgSO4), filtered and evaporated in
vacuo. The crude product was purified by flash column chroma-
tography (silica gel, EtOAc/hexane¼2/3) to give 13 as a white solid
for 1 h, then gradually warmed to rt. After further stirring for 2 h at
rt, TFA (0.67 mL, 7.5 mmol) was added and the mixturewas stirred at
rt overnight. The reaction mixture was quenched with saturated
NH4Cl (50 mL), and the organic layer was separated. The aqueous
layer was extracted with EtOAc (50 mLꢂ3). The combined organic
extracts were washed with saturated NaHCO3 (50 mLꢂ3), brine
(50 mL), dried (MgSO4), filtered and evaporated in vacuo. The crude
product was purified by flash column chromatography (silica gel,
CH2Cl2/hexane¼1/1) to give 2b as a pale yellowoil (680 mg, 55%): 1H
(516 mg, 43%): mp 117–118 ꢀC; 1H NMR (400 MHz, CDCl3)
d 0.97 (t,
J¼7.2 Hz, 6H), 1.47 (sext, J¼7.2 Hz, 4H), 1.71 (tt, J¼7.2, 7.6 Hz, 4H),
1.81–1.98 (br, 2H), 2.75 (t, J¼7.6 Hz, 4H), 4.73 (s, 4H), 6.70 (s, 2H),
7.23 (d, J¼8.4 Hz, 2H), 7.37 (t, J¼7.6 Hz, 2H), 7.47 (t, J¼8.4 Hz, 1H),
7.59 (d, J¼7.6 Hz, 2H), 7.64 (d, J¼7.6 Hz, 2H), 7.75 (s, 2H), 8.03 (s,
NMR (400 MHz, CDCl3)
d
1.00 (t, J¼7.4 Hz, 6H), 1.51 (sext, J¼7.4 Hz,
4H),1.76 (tt, J¼7.4, 7.6 Hz, 4H), 2.80 (t, J¼7.6 Hz, 4H), 3.45 (s, 6H), 4.53
(s, 4H), 6.74 (s, 2H), 7.25 (d, J¼8.2 Hz, 2H), 7.40 (t, J¼8.2 Hz, 2H), 7.52
(t, J¼7.7 Hz,1H), 7.64 (d, J¼7.7 Hz, 2H), 7.69 (d, J¼8.2 Hz, 2H), 7.72 (s,
1H); 13C NMR (100 MHz, CDCl3)
d 14.8, 23.4, 26.5, 32.8, 65.6, 109.6,
122.0, 122.5, 122.9, 123.8, 124.3, 125.7, 128.7, 128.8, 130.9, 131.8,
141.2, 147.6, 151.5; IR (KBr)
n
3332, 2954, 2927, 2869, 1599, 1483,
2H), 8.03 (s, 1H); 13C NMR (100 MHz, CDCl3)
d 14.2, 22.8, 25.9, 32.2,
1453, 1378, 1209, 1016, 952, 896, 787, 693 cmꢁ1; HRMS (FAB) calcd
for C36H38O4: 534.2770; found: 534.2780.
58.2, 74.6, 109.3, 122.4, 122.7, 122.8, 123.8, 124.2, 126.4, 128.6, 128.7,
130.7, 131.7, 138.4, 147.6, 151.6; IR (KBr) 2955, 2928, 2858, 2819,
1600, 1484, 1467, 1453, 1379, 1194, 1110, 959, 888, 787, 694 cmꢁ1
n
;
4.1.11. Bisaldehyde (14). A solution of 13 (534 mg, 1.0 mmol) in
CH2Cl2 (30 mL) was added slowly to a suspension of activated
MnO2 (1.7 g, 20.0 mmol) in CH2Cl2 (10 mL) at rt. The reaction
mixture was stirred for 6 h at rt. After passing through a silica gel
bed (5 cm) and washing with EtOAc (10 mLꢂ5), the combined fil-
trate was evaporated in vacuo to afford 14 as a pale yellow solid
HRMS (FAB) calcd for C38H42O4: 562.3083; found: 562.3074; Anal.
Calcd for C38H42O4: C 81.10, H 7.52; found: C 80.61, H 7.60.
4.1.14. Oligomer (2c). Under argon, nBuLi (0.22 mL, 2.5 M in hexane,
0.55 mmol) was introduced dropwise to a solution of 9 (252 mg,
0.5 mmol) in THF (30 mL) at ꢁ78 ꢀC and the mixture was stirred at
ꢁ78 ꢀC for 50 min. A solution of 15 (27 mg, 0.2 mmol) in THF (5 mL)
was added at ꢁ78 ꢀC and the mixture was stirred at ꢁ78 ꢀC for 1 h,
then gradually warmed to rt. After further stirring for 2 h at rt, TFA
(0.09 mL, 1.0 mmol) was added and the mixture was stirred at rt
overnight. The reaction mixture was quenched with saturated
NH4Cl (20 mL), and the organic layer was separated. The aqueous
layer was extracted with EtOAc (20 mLꢂ3). The combined organic
extracts were washed with saturated NaHCO3 (20 mLꢂ3), brine
(20 mL), dried (MgSO4), filtered and evaporated in vacuo. The crude
product was purified by flash column chromatography (silica gel,
EtOAc/hexane¼1/9) to give 2c as a white solid (67 mg, 35%): mp
(503 mg, 95%): mp 131–132 ꢀC; 1H NMR (400 MHz, CDCl3)
d 0.97 (t,
J¼7.2 Hz, 6H), 1.48 (sext, J¼7.2 Hz, 4H), 1.74 (tt, J¼7.2, 7.4 Hz, 4H),
2.77 (t, J¼7.4 Hz, 4H), 6.80 (s, 2H), 7.50–7.65 (m, 3H), 7.64 (d,
J¼7.2 Hz, 2H), 7.74 (d, J¼8.2 Hz, 2H), 7.97 (d, J¼8.2 Hz, 2H), 8.01 (s,
1H), 8.20 (s, 2H), 10.01 (s, 2H); 13C NMR (100 MHz, CDCl3)
d 14.5,
23.0, 26.2, 32.4, 110.3, 122.4, 124.0, 124.15, 124.22, 128.0, 128.6,
128.8, 129.1, 131.3, 136.4, 148.0, 150.0, 191.3; IR (KBr) 3056, 2955,
n
2928, 2869, 2859, 2724, 1697, 1600, 1466, 1454, 1377, 1299, 1205,
1161, 957, 893, 790, 686 cmꢁ1; HRMS (FAB) calcd for C36H34O4:
530.2457; found: 530.2458; Anal. Calcd for C36H34O4: C 81.48, H
6.46; found: C 80.92, H 6.53.
79–80 ꢀC; 1H NMR (400 MHz, CDCl3)
d 0.95–1.00 (m, 12H), 1.45–
4.1.12. Oligomer (2a). Under argon, nBuLi (2.2 mL, 2.5 M in hexane,
5.5 mmol) was introduced dropwise to a solution of 8 (1.53 g,
5.0 mmol) in THF (100 mL) at ꢁ78 ꢀC and the mixture was stirred at
ꢁ78 ꢀC for 50 min. A solution of 16 (675 mg, 4.5 mmol) in THF
(15 mL) was added at ꢁ78 ꢀC and the mixture was stirred at ꢁ78 ꢀC
for 1 h, then gradually warmed to rt. After further stirring for 2 h at
rt, TFA (0.67 mL, 7.5 mmol) was added and the mixture was stirred
at rt overnight. The reaction mixture was quenched with saturated
NH4Cl (50 mL), and the organic layer was separated. The aqueous
layer was extracted with EtOAc (50 mLꢂ3). The combined organic
extracts were washed with saturated NaHCO3 (50 mLꢂ3), brine
(50 mL), dried (MgSO4), filtered and evaporated in vacuo. The crude
product was purified by flash column chromatography (silica gel,
CH2Cl2/hexane¼1/2) to give 2a as a pale yellow oil (1.06 g, 65%): 1H
1.53 (m, 8H), 1.68–1.78 (m, 8H), 2.73–2.82 (m, 8H), 3.43 (s, 6H), 4.51
(s, 4H), 6.70 (s, 2H), 6.75 (s, 2H), 7.24 (d, J¼7.7 Hz, 2H), 7.38 (t,
J¼7.7 Hz, 2H), 7.46 (t, J¼7.7 Hz, 2H), 7.52 (t, J¼7.7 Hz, 1H), 7.59 (d,
J¼7.7 Hz, 2H), 7.65–7.71 (m, 9H), 8.04 (s, 2H); 13C NMR (100 MHz,
CDCl3)
d 14.5, 23.1, 26.2, 26.3, 32.5, 58.3, 74.6, 109.3, 120.4, 121.8,
122.2, 122.6, 122.7, 123.6, 124.1, 126.2, 128.4, 128.5, 130.5, 130.6,
131.6, 131.7, 138.2, 147.3, 147.4, 151.3; IR (KBr)
n 2954, 2927, 2859,
1597, 1482, 1466, 1453, 1378, 1193, 1102, 943, 886, 788, 691 cmꢁ1
HRMS (FAB) calcd for C66H70O6: 958.5172; found: 958.5164.
;
4.1.15. Oligomer (2d). Under argon, nBuLi (0.32 mL, 2.5 M in hex-
ane, 0.8 mmol) was introduced dropwise to a solution of 9 (380 mg,
0.75 mmol) in THF (30 mL) at ꢁ78 ꢀC and the mixture was stirred at
ꢁ78 ꢀC for 50 min. A solution of 14 (146 mg, 0.32 mmol) in THF
(5 mL) was added at ꢁ78 ꢀC and the mixture was stirred at ꢁ78 ꢀC
for 1 h, then gradually warmed to rt. After further stirring for 2 h at
rt, TFA (0.14 mL, 1.5 mmol) was added and the mixture was stirred
at rt overnight. The reaction mixture was quenched with saturated
NH4Cl (20 mL), and the organic layer was separated. The aqueous
layer was extracted with EtOAc (20 mLꢂ3). The combined organic
extracts were washed with saturated NaHCO3 (20 mLꢂ3), brine
(20 mL), dried (MgSO4), filtered and evaporated in vacuo. The crude
product was purified by flash column chromatography (silica gel,
EtOAc/hexane¼1/9) to give 2d as a white solid (86 mg, 20%): mp
NMR (400 MHz, CDCl3)
d
0.99 (t, J¼7.2 Hz, 3H), 1.47 (sext, J¼7.2 Hz,
2H), 1.70 (tt, J¼7.2, 7.8 Hz, 2H), 2.72 (t, J¼7.8 Hz, 2H), 3.42 (s, 3H),
3.45 (s, 3H), 4.52 (s, 2H), 4.55 (s, 2H), 6.70 (s, 1H), 7.23 (d, J¼7.6 Hz,
1H), 7.27 (d, J¼7.6 Hz, 1H), 7.38 (t, J¼7.6 Hz, 1H), 7.42 (t, J¼7.6 Hz,
1H), 7.62 (d, J¼7.6 Hz, 1H), 7.66–7.71 (m, 3H); 13C NMR (100 MHz,
CDCl3) d 14.1, 22.7, 25.8, 32.1, 58.13, 58.15, 74.55, 74.62, 109.3, 122.8,
122.9, 124.1, 124.6, 124.7, 126.0, 126.4, 128.5, 128.6, 130.7, 131.6,
138.3, 138.4, 147.6, 151.5; IR (KBr)
n 2954, 2926, 2858, 2819, 1611,
1467, 1450, 1378, 1193, 1103, 959, 788, 699 cmꢁ1; HRMS (FAB) calcd
for C24H28O3: 364.2083; found: 364.2046; Anal. Calcd for C24H28O3:
C 79.09, H 7.74; found: C 79.63, H 7.88.
107–108 ꢀC; 1H NMR (400 MHz, CDCl3)
d 0.93–0.98 (m, 18H), 1.45–
1.51 (m, 12H), 1.68–1.76 (m, 12H), 2.72–2.80 (m, 12H), 3.42 (s, 6H),
4.50 (s, 4H), 6.68 (s, 2H), 6.71 (s, 2H), 6.73 (s, 2H), 7.22 (d, J¼7.7 Hz,
2H), 7.37 (t, J¼7.7 Hz, 2H), 7.43–7.52 (m, 5H), 7.58–7.70 (m, 15H),
4.1.13. Oligomer (2b). Under argon, nBuLi (2.2 mL, 2.5 M in hexane,
5.5 mmol) was introduced dropwise to a solution of 8 (1.53 g,
5.0 mmol) in THF (100 mL) at ꢁ78 ꢀC and the mixture was stirred at
ꢁ78 ꢀC for 50 min. A solution of 15 (290 mg, 2.2 mmol) in THF
(20 mL) was added at ꢁ78 ꢀC and the mixture was stirred at ꢁ78 ꢀC
8.04 (s, 2H), 8.06 (s, 2H); 13C NMR (100 MHz, CDCl3)
d 14.15, 14.17,
22.8, 26.0, 26.05, 32.25, 32.29, 58.2, 74.6, 109.4, 109.5, 120.6, 122.0,
122.4, 122.8, 122.9, 123.7, 124.22, 124.29, 124.32, 124.40, 126.4,

C.-M. Chou et al. / Tetrahedron 65 (2009) 9749–9755
9755
128.6, 128.8, 130.76, 130.82, 130.88, 131.8, 131.90, 131.94, 138.4,
Chang of Institute of Atomic and Molecular Science, Academia
Sinica for helpful discussion.
147.56, 147.62, 147.68, 151.6; IR (KBr) n 2955, 2926, 2857, 1596, 1481,
1467, 1451, 1378, 1194, 1103, 944, 813, 786, 688 cmꢁ1; HRMS (FAB)
calcd for C94H98O8: 1354.7262; found: 1354.7278.
Supplementary data
4.1.16. Oligomer (2e). Under argon, nBuLi (0.16 mL, 2.5 M in hexane,
0.4 mmol) was introduced dropwise to a solution of 12 (350 mg,
0.39 mmol) in THF (15 mL) at ꢁ78 ꢀC and the mixture was stirred at
ꢁ78 ꢀC for 50 min. A solution of 14 (73 mg, 0.16 mmol) in THF
(5 mL) was added at ꢁ78 ꢀC and the mixture was stirred at ꢁ78 ꢀC
for 1 h, then gradually warmed to rt. After further stirring for 3 h at
rt, TFA (0.07 mL, 0.8 mmol) was added and the mixture was stirred
at rt overnight. The reaction mixture was quenched with saturated
NH4Cl (20 mL), and the organic layer was separated. The aqueous
layer was extracted with EtOAc (20 mLꢂ3). The combined organic
extracts were washed with saturated NaHCO3 (20 mLꢂ3), brine
(20 mL), dried (MgSO4), filtered and evaporated in vacuo. The
resulting residue was recrystallized from ether/pentane (3/10) to
afford 2e as a white solid (139 mg, 40%): mp 135–136 ꢀC; 1H NMR
Supplementary data associated with this article can be found in
online version, at doi:10.1016/j.tet.2009.09.077.
References and notes
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(400 MHz, CDCl3)
d 0.94–0.97 (m, 30H), 1.45–1.48 (m, 20H), 1.67–
1.70 (m, 20H), 2.72–2.78 (m, 20H), 3.42 (s, 6H), 4.50 (s, 4H), 6.68–
6.70 (m, 10H), 7.23 (d, J¼7.6 Hz, 2H), 7.30–7.50 (m, 11H), 7.58–7.70
(m, 21H), 8.03–8.07 (m, 10H); 13C NMR (100 MHz, CDCl3)
d 14.0,
22.7, 22.9, 25.9, 26.0, 32.1, 58.1, 74.6, 109.6, 120.6, 120.7, 122.1, 122.9,
123.0, 124.1, 124.4, 124.5, 126.5, 128.8, 128.9, 130.9, 131.0, 131.9,
132.1, 138.6, 147.8, 151.7, 151.8; IR (KBr)
n 2952, 2923, 2853, 1593,
1455, 1374, 1243, 1095, 943, 786, 739, 687 cmꢁ1; HRMS (FAB) calcd
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Acknowledgements
This work was supported by the National Science Council and
the National Taiwan University. We thank Professor Huan–Cheng
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