Phenanthrene-tethered furan-containing cyclophenes: Synthesis and photophysical properties

Article abstract of DOI:10.1021/jo100873z

(Figure presented) Two phenanthrene-fused furan-containing teraryl cyclophenes 5 and 6 are synthesized. These cyclophenes exhibit charge transfer band in the absorption spectra, unusually large Stokes shifts in the emission spectra, and exceptionally high

Full text of DOI:10.1021/jo100873z

pubs.acs.org/joc
Phenanthrene-Tethered Furan-Containing Cyclophenes: Synthesis and
Photophysical Properties
Hao-Tien Bai, Hsin-Chieh Lin, and Tien-Yau Luh*
Department of Chemistry, National Taiwan University, Taipei, Taiwan 106
tyluh@ntu.edu.tw
Received May 7, 2010
Two phenanthrene-fused furan-containing teraryl cyclophenes 5 and 6 are synthesized. These
cyclophenes exhibit charge transfer band in the absorption spectra, unusually large Stokes shifts in
the emission spectra, and exceptionally high μβ values in the electric-field-induced second-harmonic
generation (EFISH) experiments. The μβ1.91 values for 5 and 6 are 438 and 777ꢀ10-48 esu, respec-
tively. The bridging double bond in 5 and 6 can serve as either an electron donor or acceptor
depending on the nature of the substituent on furan rings. DFT calculations at the B3LYP/6-31G**
level indicate that the electron density distributions in HOMO and LUMO are very different.
Interaction between the oligoaryl systems and the double bond may account for the significant
enhancement in hyperpolarizability.
Introduction
electron acceptor. The contribution of the resonance struc-
ture like 1a resulting in charge-transfer interactions between
two twisted π-systems may be responsible for these extra-
ordinary properties.1,2 The electron delocalization may take
place in their respective hemisphere where the electron-
vibration interaction may be strong enough to induce the
polar character of 1. This kind of resonance contribution has
been shown to lead to symmetry breaking of centrosym-
metric cyclophandienes 3 and 4 so that the similar remark-
able second-order optical nonlinearity is observed.3 It is
known that the dihedral angle between two twisted π-sys-
tems significantly dictates the second-order nonlinear optical
properties.1,2 It is envisaged that when one of the cis-stilbene
moieties in 4 is changed by a phenanthrene skeleton as in 5
the system would be more strained and the dihedral angle
between the remaining bridging double bond and the adj-
acent benzene ring would also increase. As such, the two
π systems would be more twisted, and the second-order NLO
might therefore be enhanced. In this paper, we wish to report
Cyclophenes 1 incorporated with electron-rich hetero-
aromatic-containing oligoaryls (e.g., furan or thiophene) have
recently been shown to furnish a unique structural feature
rendering unusual photophysical properties.1 To illustrate
this, cyclophenes 1 exhibit monomeric oligoaryl-like absorp-
tion spectra but large Stokes shift in the emission spectra and
unusual second-rder nonlinear optical (NLO) properties
with βo values comparable to that of 4-dimethylamino-40-
nitrostilbene (DANS, 2).1 The five-membered hetero-
aromatic rings in 1 may serve as an electron-donating group,
whereas the bridged double bond may be viewed as an
(1) (a) Lin, H.-C.; Lin, W.-Y.; Bai, H.-T.; Chen, J.-H.; Jin, B.-Y.; Luh,
T.-Y. Angew. Chem., Int. Ed. 2007, 46, 897–900. (b) Tseng, J.-C.; Lin, H.-C.;
Huang, S.-L.; Lin, C.-L.; Jin, B.-Y.; Chen, C.-Y.; Yu, J.-K.; Chou, P.-T.;
Luh, T.-Y. Org. Lett. 2003, 5, 4381–4384.
(2) (a) Albert, I. D. L.; Marks, T. J.; Ratner, M. A. J. Am. Chem. Soc.
1998, 120, 11174–11181. (b) Kang, H.; Facchetti, A.; Zhu, P.; Jiang, H.;
Yang, Y.; Cariati, E.; Righetto, S.; Ugo, R.; Zuccaccia, C.; Macchioni, A.;
Stern, C. L.; Liu, Z.; Ho, S.-T.; Marks, T. J. Angew. Chem., Int. Ed. 2005, 44,
7922–7925. (c) Isborn, C. M.; Davidson, E. R.; Robinson, B. H. J. Phys.
Chem. A 2006, 110, 7189–7196. (d) Kanis, D. R.; Ratner, M. A.; Marks, T. J.
ꢀ
Chem. Rev. 1994, 94, 195–242. (e) Di Bella, S.; Lanza, G.; Fragala, I.;
Yitzchaik, S.; Ratner, M. A.; Marks, T. J. J. Am. Chem. Soc. 1997, 119,
3003–3006.
(3) Lin, H.-C.; Hsu, J.-H.; Lee, C.-K.; Tai, O. Y.-H.; Wang, C.-H.; Chou,
C.-M.; Chen, K.-Y.; Wu, Y.-L.; Luh, T.-Y. Chem.;Eur. J. 2009, 15, 13201–
13209.
DOI: 10.1021/jo100873z
r
Published on Web 06/10/2010
J. Org. Chem. 2010, 75, 4591–4595 4591
2010 American Chemical Society

Bai et al.
JOCArticle
the synthesis and photophysical properties of phenanthrene-
tethered furan-containing cyclophenes 5 and 6.
SCHEME 1a
aKey: (a) (1) 1 equiv of nBuLi, THF, -78 °C, (2) phenanthrene-3,6-
dicarboxaldehyde, 8, -78 °C, (3) TFA, 45%; (b) DIBAL, THF, 94%;
(c) MnO2, 80%; (d) TiCl4, Zn, pyridine, 10%.
SCHEME 2a
aKey: (a) (1) TMSCtCLi, (2) MnO2, 95%; (b) HSCH2CH2SH,
BF3 OEt2, 90%; (c) K2CO3; (d) MeMgI, ClCO2Et, 76%; (e) (1) 1 equiv
3
of nBuLi, THF, -78 °C, (2) phenanthrene-3,6-dicarboxaldehyde, 8,
-78 °C, (3) TFA, 40%; (f) DDQ, 85%; (g) TiCl4, Zn, pyridine, 30%.
Results and Discussion
signals was observed, indicating these cyclophenes would be
relatively rigid.
Synthesis. The synthesis of 5 and 6 are shown in Schemes 1
and 2. In a manner similar to those described previously,1,3
annulation protocol starting from propargylic dithioacetals
7 was the key step to furnish the furan heterocycles.4,5 Intra-
molecular McMurry coupling reactions of bis-aldehydes 11
and 18 afforded the bridging double bond in 5 and 6,
respectively.6 The details are described in the Experimental
Section.
Photophysical Properties. The absorption and emission
spectra of 5 and 6 are shown in Figure 1, and these properties
are compared with those of 1 and 3 and related compounds in
Table 1. Like those of 1 and 3, both 5 and 6 exhibit similar
absorption maxima at ca. 330-335 nm, which is very differ-
ent from those of the oligoaryl precursors 9 and 17. These
results indicate that the conjugation lengths in 5 and 6 would
be very different from those of 9 and 17. In other words, little
contribution from the phenanthrene moiety in 5 and 6 to the
electronic transition in these cyclophenes would be expected.
In addition to the λmax in the region of 330 nm, the longer
wavelengths absorption around 400 nm for 5 and 6 could be
assigned to a symmetry-forbidden transition attributed to
electron-vibration interactions, which may have charge-
transfer character.8
Variable-temperature 1H NMR spectra of 5 and 6 showed
only slight changes in chemical shifts.7 No broadening of
(4) (a) Lee, C.-F.; Yang, L.-M.; Hwu, T.-Y.; Feng, A.-H.; Tseng, J.-C.;
Luh, T.-Y. J. Am. Chem. Soc. 2000, 122, 4992–4993. (b) Lee, C.-F.; Liu,
C.-Y.; Song, H.-C.; Luo, S.-J.; Tseng, J.-C.; Tso, H.-H.; Luh, T.-Y. Chem.
Commun. 2002, 2824–2825. (c) Chou, C.-M.; Chen, W.-Q.; Chen, J.-H.; Lin,
C.-L.; Tseng, J.-C.; Lee, C.-F.; Luh, T.-Y. Chem. Asian J. 2006, 1, 46–55.
(d) For a review, see: Luh, T.-Y.; Lee, C.-F. Eur. J. Org. Chem. 2005, 3875–
3885.
(5) It is worthy noting that the ester group in 7 and 16 were stable at
-78 °C upon treatment with BuLi under the reaction conditions.
(6) For a review, see: McMurry, J. E. Chem. Rev. 1989, 89, 1513–1524.
(7) See the Supporting Information.
(8) Walser, D.; Zumofen, G.; Plakhotnik, T. J. Chem. Phys. 2000, 113,
8047–8058.
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Bai et al.
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FIGURE 1. Absorption and emission spectra of 5 (blue), 6 (red),
9 (green), and 17 (black) in CHCl3.
FIGURE 2. Contour plots of the frontier molecular orbitals ob-
tained by DFT calculations at the B3LYP/6-31G** level (upper:
LUMO, lower: HOMO) of 5 (left) and 6 (right).
TABLE 1. Linear and Nonlinear Optical Properties of Cyclophenes and
Related Compounds in CHCl3
c
d
compd
λmax (nm)
λem (nm)
Φa
μb
μβ1.91
β1.32
This observation is similar to those found in 1,1a where the
electron delocalization from furan ring to the bridging dou-
ble bond might take place. As such, the dipolar character like
1a might contribute to the ground-state structures of 5.
Because of the presence of an electron-withdrawing group
on the furan moiety, the electron distribution in 6 would be
very different. DFT calculations shown in Figure 2 indicate
the electron flow from the bridging double bond in HOMO
to the ester moieties in LUMO. Owing to different electron
demand, the bridging double bond in 6 may serve as an
electron donating group.
Electric-Field-Induced Second-Harmonic Generation (EFISH)
Studies. As described above, both 5 and 6 exhibit unusual
photophysical behavior. Like 1 and 3, it seems likely that
these cyclophenes may also exhibit second order NLO
properties. As shown in Table 1, the μβ value for 5 (438 ꢀ
10-48 esu) measured by the EFISH method was comparable
with that of 2 (450 ꢀ 10-48 esu, μ = 6.6 D) and almost twice
of that of 1 (232 ꢀ 10-48 esu). It is noteworthy that the β1.32
values for 1 and 3 are comparable (Table 1). Both 3 and
5 were relatively nonpolar as revealed by their calculated
dipole moments (Table 1). Nevertheless, the presence of the
phenanthrene moiety in 5 may slightly change the polarity so
that the second-order nonlinearity for 5 is somewhat en-
hanced. In addition, 5 would be more strained than 3, and the
dihedral angle between the bridging double bond and the
carbon-carbon bond of the immediate adjacent benzene
ring in 5 would be somewhat larger than that of 3. The two π
systems would be more twisted in 5, and the second-order
optical nonlinearity might therefore be perturbed.
1
3
5
6
9
17
325
330
335
331
335, 376
290, 330, 378
501
550
479
516
426, 451
430, 456
0.28
0.01
0.01
0.03
0.90
0.75
1.12
0.27
0.50
2.80
232
220
208
438
777
aUsing coumarin I in EtOAc (Φ = 0.99) as reference. bCalculated by
DFT at the 6-31G** level. cIn 10-48 esu. dIn 10-30 esu.
As shown in Figure 1, the emission profiles for 5 and 6 are
very different from those of 9 and 17, respectively. Both 5
and 6 exhibit large Stokes shift (>160 nm) in their emission
spectra, and the quantum yields of 5 and 6, like 1 and 3, are
much smaller than those of 9 and 17. The bridging double
bond and the remaining oligoaryl moiety would be non-
planar, and interactions between the two π-systems in 5 and
in 6 may be different in the ground and the excited states
resulting in large Stokes Shift.
As described previously,1a,3 the furan moiety in 5 can be
considered as an electron-donating group with a σpþ value of
-0.39,9 and the bridging double bonds in 5 can serve as an
electron acceptor. On the other hand, the presence of an ester
substituent on the furan ring may change the electronic
structure of 6. In other words, the ethoxycarbonyl-
substituted furan moiety in 6 is an electron donating group
no more. Nevertheless, the absorption and emission profiles
for 6 were similar to those of 5, indicating that the impor-
tance of the twist π-interactions on the photophysical beha-
vior of these cyclophenes.
Density Functional Theory (DFT) Calculations. DFT cal-
culations at B3LYP/6-31G** level of 5 with full geometric
optimization showed that the electron-density distribution
shifted from the furan moieties in HOMO to the double bond
in LUMO (Figure 2). Such electron distributions in HOMO
and LUMO of 5 may resemble π(D) and π*(A), respectively.10
The presence of the ester substituent on the furan ring in 6
would significantly change the polarity of the molecule, and
the calculated dipole moment for 6 was 2.8 D. The μβ value
was 777ꢀ10-48 esu, which is also larger than that for 5. The
observation of second-order NLO properties for 6 indicates
that interaction between the two twisted π-systems would be
similar to those in 1, 3, and 5.
(9) Hansch, C.; Leo, A.; Taft, R. W. Chem. Rev. 1991, 91, 165–195.
(10) (a) Nalwa, H. S., Miyata, S. Eds. Nonlinear Optics of Organic Molecules
and Polymers; CRC Press: Boca Raton, FL, 1997. (b) Torre, G. D. L.; Vazquez, P.;
ꢁ
ꢁ
ꢁ
Agullo-Lopez, F.; Torres, T. Chem. Rev. 2004, 104, 3723–3750. (c) Delaire, J. A.;
Nakatani, K. Chem. Rev. 2000, 100, 1817–1846. (d) Kanis, D. R.; Ratner, M. A.;
Marks, T. J. Chem. Rev. 1994, 94, 195–242. (e) Marder, S. Chem. Commun.
2006, 131, 131–134. (f) Ahlheim, M.; Barzoukas, M.; Bedworth, P. V.; Blanchard-
Desce, M.; Fort, A.; Hu, Z.-Y.; Marder, S. R.; Perry, J. W.; Runser, C.; Staehelin,
M.; Zysset, B. Science 1996, 271, 335–337.
Conclusions
We have depicted that phenanthrene-incorporated furan-
containing cyclophanenes 5 and 6 exhibited extraordinarily
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Bai et al.
JOCArticle
large Stokes shifts and second-order nonlinear optical μβ
values which were comparable to those of parent cyclophene
1 and cyclophanediene 3. The substituents on furan rings in
5 and 6 may only perturb the polarity of these cyclophenes.
Interactions between two twisted π-systems (oligoaryl and
bridging double bond) would be the unique structural fea-
ture responsible for this unusual photophysical behavior.
residue was recrystallized from Et2O/CH2Cl2, to afford 11 as a
fluorescent yellow solid (1.11 g, 97%): mp 89-90 °C; 1H NMR
(400 MHz, CDCl3): δ = 0.93 (t, J = 7.4 Hz, 6 H), 1.50 (quint,
J = 7.4 Hz, 4 H), 1.79 (m, 4 H), 2.91 (t, J = 7.4 Hz, 4 H), 6.94 (s,
2 H), 7.75 (s, 2 H), 7.87 (d, J = 8.4 Hz, 4 H), 7.91 (d, J = 8.4 Hz,
4 H), 7.96 (br s, 4 H), 9.03 (s, 2 H), 9.96 (s, 2 H); 13C NMR (100
MHz, CDCl3): δ = 14.1, 22.7, 26.0, 32.1, 112.6, 119.5, 123.6,
124.3, 125.1, 126.8, 128.9, 129.3, 130.2, 130.3, 131.3, 134.6,
135.8, 149.8, 150.6, 191.1; IR (KBr) ν 3411, 2955, 2927, 2870,
2816, 1707, 1605, 1502, 1411, 1381, 1253, 1097, 1017, 915,
845, 754 cm-1; HRMS (FAB) (M þ Hþ) calcd for C44H39O4
631.2848, found 631.2848.
Experimental Section
Phenanthrene-Incorporated Oligoaryl 9. Under Ar atmo-
sphere, to a solution of 71a (752 mg, 2.4 mmol) in THF (60 mL)
at -78 °C was added dropwise nBuLi (1.1 mL, 2.5 M in hexane
2.8 mmol), and the mixture was stirred for 50 min. A solution of
dialdehyde 811 (250 mg, 1.1 mmol) in THF (30 mL) was then
added at -78 °C. The mixture was stirred for 1 h, then gradually
warmed to rt, and further stirred for 1 h. TFA (1.0 mL, 1.54 g/
mL, 12.0 mmol) was added, the mixture was stirred at rt over-
night, and the organic layer was separated. The aqueous layer
was extracted with Et2O (150 mLꢀ3). The combined organic
layer was washed with saturated NaHCO3 (100 mL ꢀ 2) and
brine (100 mL), dried (MgSO4), filtered, and evaporated in
vacuo. The resulting residue was suspended in Et2O, the solid
was filtered and washed with a mixture of Et2O/pentane (1:1),
and 9 was collected as a fluorescent yellow powder (2.20 g,
40%): mp 177-179 °C; 1H NMR (400 MHz, CDCl3): δ0.92 (t,
J = 7.5 Hz, 6 H), 1.44 -1.50 (sext, J = 7.5 Hz, 4 H), 1.76 (quint,
J = 7.5 Hz, 4 H), 2.91 (t, J = 7.5 Hz, 4 H), 3.91 (s, 6 H), 6.89 (s,
2 H), 7.74 (s, 2 H), 7.83 (d, J = 8.4 Hz, 4 H), 7.92-7.98 (m, 4 H),
8.02 (d, J = 8.4 Hz, 4 H), 9.05 (s, 2 H); 13C NMR (100 MHz,
CDCl3): δ14.1, 22.7, 26.1, 32.1, 52.1, 111.7, 119.3, 123.0, 124.2,
124.9, 126.6, 128.1, 128.8, 129.4, 130.0, 130.2, 131.1, 134.4,
1-(4-(Methoxymethyl)phenyl)-3-(trimethylsilyl)prop-2-yn-1-one
(13). Under N2, to a THF solution (200 L) of trimethylsilylace-
tylene (28.0 mL, 0.71 g/mL, 0.2 mol) was slowly added n-BuLi
(82.0 mL, 2.5 M in hexane 0.21 mol) at -78 °C. The mixture was
warmed to rt and stirred for 1 h. After the mixture was cooled to
-78 °C, a THF (200 mL) solution of 12 (30.0 g, 0.2 mol) was
added slowly, and the mixture was stirred for 10 min at -78 °C
and then slowly warmed to rt and further stirred for 1 h. The
mixture was quenched with saturated NH4Cl (800 mL), and the
organic layer was separated. The aqueous layer was extracted
with Et2O (200 mLꢀ2). The combined organic extracts were
dried (MgSO4), filtered, and evaporated in vacuo to afford the
crude ynol. A solution of crude ynol in CH2Cl2 (250 mL) was
added slowly to a suspension of activated MnO2 (87.0 g, 1.0 mol)
in CH2Cl2 (250 mL) at rt, and the mixture was stirred for 12 h at
rt. After being passed through a silica gel bed (7 cm) and washed
with EtOAc (200 mL ꢀ 2), the combined filtrate was evaporated
in vacuo to give crude 13 (49.6 g, 97%) as a yellow liquid.
Kugelrohr distillation (0.01 Torr, 80 °C) afforded pure 13 as
colorless oil: 1H NMR (400 MHz, CDCl3) δ 0.31 (s, 9 H), 3.40 (s,
3 H), 4.52 (s, 2 H), 7.41-7.44, 8.09-8.11 (m, 4 H); 13C NMR
(100 MHz, CDCl3) δ -0.5, 58.5, 73.9, 100.4, 100.8, 127.1, 129.7,
135.6, 144.9, 177.1; IR (KBr) ν 2955, 2924, 2854, 2153, 1647,
1607, 1572, 1458, 1414, 1379, 1308, 1253, 1195, 1171, 1034, 1014,
971, 924, 847, 761, 740; HRMS (FAB) (M þ Hþ) calcd for
C14H19O2Si 247.1154, found 247.1158.
4
149.1, 150.9, 166.5; UV-vis (CHCl3): 335 nm (ε = 5.0ꢀ10
M-1 cm-1); IR (KBr) ν 3487, 2955, 2930, 2870, 1720, 1609, 1435,
1277, 1178, 1109, 1017, 934, 848, 771, 669 cm-1; HRMS (FAB)
(Mþ) calcd for C46H42O6 690.2981, found 690.2993.
Diol 10. To a solution of diester 9 (1.30 g, 1.80 mmol) in THF
(80 mL) under Ar atmosphere was added slowly a solution of
DIBAL (17.0 mL, 1.0 M in hexane 17.0 mmol) at 0 °C, and the
mixture was stirred at rt for 3 h. The reaction was quenched by
pouring it into saturated NH4Cl (100 mL), and the mixture was
stirred for 30 min. The gel-like mixture was acidified with 6 M
HCl (50 mL) and extracted with CH2Cl2 (200 mL ꢀ 3). The
combined organic extracts were washed with saturated NaH-
CO3 (200 mL ꢀ 2) and brine (200 mL), dried (MgSO4), filtered,
and evaporated in vacuo to afford the crude product, which was
recrystallized from Et2O/CH2Cl2 to give 10 as a fluorescent
[2-[2-(4-Methoxymethylphenyl)-1,3-dithiolan-2-yl]ethynyl]tri-
methylsilane (14). To a solution of 13 (22.1 g, 0.09 mol) in MeOH
(400 mL) were added BF3 Et2O (13.1 mL, 0.1 mol) and 1,
3
2-ethanedithiol (7.6 mL, 0.09 mol) at -78 °C. The reaction
mixture was gradually warmed to rt and further stirred for 12 h.
After quenching with 10% NaOH (400 mL), the organic layer
was separated and the aqueous layer was extracted with CH2Cl2
(100 mL ꢀ 3). The combined organic layer was washed with
10% NaOH (200 mL) and brine (100 mL) and dried (MgSO4),
filtered, and evaporated in vacuo to give 14 (27.5 g, 95%) as
a yellow solid: mp 41-43 °C (Et2O and CH2Cl2); 1H NMR
(400 MHz, CDCl3) δ 0.22 (s, 9 H), 3.37 (s, 3 H), 3.70-3.66 (m,
4 H), 4.44 (s, 2 H), 7.28-7.30, 7.89-7.91 (m, 4 H); 13C NMR
(100 MHz, CDCl3) δ 0.49, 41.4, 58.2, 61.8, 74.1, 91.2, 106.3,
127.0, 127.3, 137.2, 137.9; IR (KBr) ν 2957, 2924, 2892, 2857,
2816, 2162, 1724, 1608, 1505, 1410, 1379, 1277, 1248, 1193,
1100, 1056, 1020, 837; HRMS (FAB) (M þ Hþ) calcd for
C16H23OSiS2 323.0960, found 323.0964.
1
yellow solid (1.235 g, 95%): mp 177-178 °C; H NMR (400
MHz, CDCl3) δ 0.96 (t, J = 7.6 Hz, 6 H), 1.46-1.51 (m, 4 H),
1.74-1.78 (m, 6 H), 2.87 (t, J = 7.6 Hz, 4 H), 4.68 (s, 4 H), 6.74
(s, 2 H), 7.32 (d, J = 8.2 Hz, 4 H), 7.71 (s, 2 H), 7.81 (d, J = 8.2
Hz, 4 H), 7.90-7.92 (AB q, J = 8.8 Hz, 4 H), 9.17 (s, 2 H); 13
C
NMR (100 MHz, CDCl3) δ 14.5, 23.0, 26.4 32.4, 65.1, 109.1,
109.4, 119.1, 123.4, 123.6, 124.5, 126.2, 127.2, 128.4, 129.4,
129.8, 130.6, 139.3, 151,4; IR (KBr) ν 3391, 2956, 2927, 2870,
2854, 1667, 1650, 1615, 1463, 1262, 1015, 847, 804, 738 cm-1
;
2-Ethynyl-2-(4-methoxymethylphenyl)-1,3-dithiolane (15). A
mixture of 14 (2.80 g, 10.0 mmol) and K2CO3 (20.0 g, 0.15 mol)
in MeOH (60.0 mL) was stirred at rt for 6 h, poured into water
(100 mL), and extracted with Et2O (20 mL ꢀ 3). The combined
organic extracts were dried (MgSO4), filtered, and evaporated in
vacuo to afford the residue, which was purified by flash column
chromatography (silica gel, hexane/EtOAc = 3/1) to afford 15
as oil (2.02 g, 98%): 1H NMR (400 MHz, CDCl3) δ 3.04 (s, 1 H),
3.37 (s, 3 H), 3.73-3.68 (m, 4 H), 4.44 (s, 2 H), 7.29-7.31,
7.91-7.93 (m, 4 H); 13C NMR (100 MHz, CDCl3) δ 41.5, 58.3,
61.2, 74.1, 75.2, 85.7, 127.1, 127.2, 136.7, 138.2; IR (KBr) ν 3410,
3055, 3024, 2958, 2929, 2870, 2854, 1665, 1600, 1503, 1446, 1378,
HRMS (FAB) (Mþ) calcd for C44H42O4 634.3083, found
634.3088.
Dialdehyde 11. A solution of 10 (1.13 g, 1.71 mmol) in CH2Cl2
(20 mL) was added slowly to a suspension of activated MnO2
(1.80 g, 20.52 mmol) in CH2Cl2 (30 mL) at rt. The reaction
mixture was stirred for 6 h at rt. After being passed through a
silica gel bed (2 cm) and washed with CH2Cl2 (120 mL ꢀ 3),
the combined filtrate was evaporated in vacuo. The resulting
(11) Wong, J. Y.; Manning, C.; Leznoff, C. C. Angew. Chem. 1974, 86,
743; Angew. Chem., Int. Ed. 1974, 13, 666-667.
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JOCArticle
1316, 1261, 1201, 1177, 1072, 1023, 913, 800, 755, 696 cm-1
;
and the suspension was refluxed for 1 h. A solution of dialde-
hyde 16 (1.00 g, 1.51 mmol) in THF (50 mL) was then syringed.
After being refluxed for 16 h, the mixture was cooled to rt.
Na2CO3 (10%, 100 mL) was carefully introduced with stirring,
the mixture was filtered, and the filtrate was extracted with
CH2Cl2 (2ꢀ100 mL). The organic solution was washed with
water (2 ꢀ 100 mL), dried (MgSO4), and evaporated in vacuo to
give the residue, which was purified by flash column chromato-
graphy (silica gel, hexane/CH2Cl2 = 4/1) to afford 5 (238 mg,
HRMS (FAB) (M þ Hþ) calcd for C13H15OS2 251.0564, found
251.0563.
Ethyl 3-[[2-(4-Methoxymethylphenyl)]-1,3-dithiolan-2-yl]pro-
piolate (16). Under N2, to 15 (2.5 g, 10.0 mmol) in THF (60 mL)
was added MeMgI (15 mL, 1 M, 15 mmol). After the mixture was
stirred for 30 min, ClCO2Et (1.25 mL, 14.1 mmol) was slowly
introduced, and the mixture was stirred for 6 h, quenched with
saturated NH4Cl (100 mL), and extracted with ether (100 mL ꢀ
3). The combined organic layer was washed with brine (100 mL),
dried (MgSO4), filtered, and evaporated in vacuo to afford
the residue which was chromatographed on silica gel (hexane/
EtOAc = 4/1) to afford 16 as an oil (3.00 g, 94%): 1H NMR (400
MHz, CDCl3) δ 1.32 (t, J = 6.8 Hz, 3 H), 3.36 (s, 3 H), 3.71 (br s, 4
H), 4.25 (q, J = 6.8 Hz, 2 H), 4.44 (s, 2 H), 7.30-7.32, 7.84-7.86
(m, 4 H); 13C NMR (100 MHz, CDCl3) δ 14.1, 41.4, 58.1, 60.4,
62.1, 73.9, 78.2, 87.4, 127.35, 127.43, 135.6, 138.9, 153.5; IR (KBr)
ν 2982, 2925, 2820, 2223, 1745, 1708, 1448, 1412, 1365, 1251, 1194,
1098, 1017, 851, 755 cm-1; HRMS (FAB) (M þ Hþ) calcd for
C16H19O3S2 323.0776, found 323.0766.
1
25%) as a pale yellow solid: mp 236-238 °C; H NMR (400
MHz, CDCl3) δ 0.99 (t, J = 7.2 Hz, 6 H), 1.50 (sext, J = 7.2 Hz,
4 H), 1.70-1.74 (m, 4 H), 2.80 (t, J = 7.2 Hz, 4 H), 6.55 (s, 2 H),
6.71 (s, 2 H), 7.06-7.08, 7.61-7.64 (m, 8 H), 7.59 (s, 2 H), 7.76
(dd, J = 8.2, 1.2 Hz, 2 H), 7.80 (d, J = 8.2 Hz, 2 H), 9.51 (d, J =
1.2 Hz, 2 H); 13C NMR (100 MHz, CDCl3): δ 14.2, 22.8, 26.6,
32.3, 109.3, 119.6, 122.6, 125.0, 126.3, 128.5, 129.8, 129.9, 130.0,
130.8, 130.9, 131.2, 136.1, 148.0, 152.5; ε = 7.7 ꢀ 10 3 M-1 cm-1
(335 nm), log ε = 3.9 M-1 cm-1 in CHCl3; IR (KBr) ν 3409,
2956, 2926, 2858, 1730, 1660, 1605, 1510, 1457, 1261, 1100, 1028,
798 cm-1; HRMS (FAB) (Mþ) calcd for C44H38O2 598.2872,
found 598.2875.
Bis-dimethoxy Ether 17. Under Ar atmosphere, a solution of
nBuLi (0.95 mL, 2.5 M in hexane, 2.4 mmol) was introduced
dropwise to a solution of 16 (757 mg, 2.4 mmol) in THF (70 mL)
at -78 °C, the mixture was stirred for 1 h, and a solution of
dialdehyde 8 (250 mg, 1.1 mmol) in THF (30 mL) was then added
at -78 °C. The mixture was stirred for 1 h, gradually warmed to rt,
and further stirred for 1 h. TFA (0.2 mL, 1.54 g/mL, 2.4 mmol)
was added, the mixture was stirred at rt overnight and quenched
with saturated NaHCO3 (100 mL ꢀ 2), and the organic layer was
separated. The aqueous layer was extracted with ether (150 mL ꢀ
3), and the combined organic layer was washed with brine
(100 mL), dried (MgSO4), filtered, and evaporated in vacuo to
give the residue which was chromatographed on silica gel
(hexane/EtOAc = 10/1) to afford 17 (300 mg, 40%) as a fluore-
scent yellow solid: mp 143-144 °C; 1H NMR (400 MHz,
CDCl3) δ 1.32 (t, J = 7.2 Hz, 6 H), 3.41 (s, 6 H), 4.35 (q, J =
7.2 Hz, 4 H), 4.48 (s, 4 H), 7.17 (s, 2 H), 7.38 (d, J = 8.2 Hz, 4 H),
7.80 (s, 2 H), 7.81 (d, J = 8.2 Hz, 4 H), 7.95 (d, J = 8.4 Hz, 2 H),
Ethoxycarbonyl-Substituted Cyclophene 6. In a manner simi-
lar to that described for the preparation of 5, 18 (211 mg,
0.32 mmol) was allowed to react with TiCl4 (0.5 mL, 1.73 g/
mL, 3.2 mmol) and zinc dust (420 mg, 6.4 mmol) in THF (200
mL) to give 6 (38 mg, 18%) as a pale yellow solid: mp >290 °C
dec; 1H NMR (400 MHz, CDCl3) δ = 1.42 (t, J = 7.2 Hz, 6 H),
4.39 (q, J = 7.2 Hz, 4 H), 6.77 (s, 2 H), 7.02 (s, 2 H), 7.05 (d, J =
8.0 Hz, 4 H), 7.61 (d, J = 8.0 Hz, 4 H), 7.70 (s, 2 H), 7.88 (d, J =
8.6 Hz, 2 H), 8.83 (d, J = 8.6 Hz, 2 H), 9.45 (s, 2 H); 13C NMR
(100 MHz, CDCl3): δ = 14.5, 60.8, 108.5, 116.5, 121.5, 125.3,
126.2, 127.5, 127.9, 128.4, 128.9, 130.0, 130.3, 131.3, 132.6,
3
136.9, 152.6, 155.9, 163.5; ε = 5.0 ꢀ 10 (330 nm), log ε =
3.7 in CHCl3; IR (KBr) ν 3464, 2953, 2923, 2920, 2868, 2851,
1717, 1647, 1457, 1376, 1223, 1093, 668 cm-1; ε = 5.6 ꢀ 10 3 M-1
cm-1 (330 nm), log ε = 3.7 M-1 cm-1 in CHCl3; HRMS (EI)
(Mþ) calcd for C42H30O6 630.2042, found 630.2050.
DFT Calculations. The ground state structures of 5 and 6 were
calculated by the DFT method which was implemented in
Gaussian 98 package.12 Geometry optimizations without any
symmetry constraints have been performed. The dipole mo-
ments were calculated on the basis of optimized geometries. All
DFT calculations were carried out with the 6-31G** split
valence plus polarization basis set.13 The B3LYP functional
was employed where Becke’s three-parameter hybrid exchange
functional was combined with the Lee-Yang-Parr correlation
functional.14
8.31 (dd, J = 8.4, 1.0 Hz, 2 H), 9.65 (d, J = 1.0 Hz, 2 H); 13
C
NMR (100 MHz, CDCl3) δ 14.7, 58.3, 60.9, 74.3, 108.1, 116.0,
122.9, 123.8, 126.0, 127.2, 127.6, 127.8, 127.9, 128.8, 129.9,
4
132.2, 137.7, 151.9, 155.8, 163.0; ε = 3.1 ꢀ 10 M-1 cm-1
(330 nm), log ε = 4.5 M-1 cm-1 in CHCl3; IR (KBr) ν 3435,
2923, 2853, 1717, 1605, 1444, 1497, 1378, 1231, 1094, 1025, 850,
776 cm-1; HRMS (FAB) (Mþ) calcd for C44H38O8 694.2567,
found 694.2556.
Bis-dialdehyde 18. A mixture of 17 (72 mg, 0.1 mmol) and
DDQ (98 mg, 0.4 mmol) in CH2Cl2/H2O (9:1, 1 mL) was stirred
at rt. After beign stirred for 24 h, the mixture was passed through
a silica gel bed (1 cm) and washed with CH2Cl2 (40 mL). The
filtrate was washed with saturated NaHCO3 (20 mL ꢀ 4) and
brine (20 mL), dried (MgSO4), and evaporated in vacuo to 18
(63 mg, 86%) as a yellow solid: mp 213-214 °C; 1H NMR
(400 MHz, CDCl3) δ 1.24 (t, J = 7.2 Hz, 6 H), 4.24 (q, J =
7.2 Hz, 4 H), 7.63 (s, 2 H), 7.72-7.78(m, 12H), 8.17(d, J=8.8Hz,
2 H), 9.50 (s, 2 H), 9.84 (s, 2 H); 13C NMR (100 MHz, CDCl3) δ
14.7, 61.0, 111.2, 116.3, 122.9, 123.7, 125.8, 127.0, 127.3, 127.9,
129.7, 129.9, 132.3, 134.4, 134.8, 150.2, 156.9, 162.5, 190.4; IR
(KBr) ν 3431, 2962, 2926, 2855, 1698, 1695, 1573, 1506, 1417,
1261, 1168, 1095, 1021, 800, 759, 667 cm-1; HRMS (FAB) (Mþ)
calcd for C42H30O8 662.1941, found 662.1933.
Acknowledgment. We thank the National Science Council
and the National Taiwan University for support.
Supporting Information Available: 1H and 13C NMR spec-
tra of all new compounds and variable-temperature H NMR
1
spectra of 5 and 6. This material is available free of charge via the
Internet at http://pubs.acs.org.
(12) Gaussian 98, revision A.9; Gaussian, Inc.: Pittsburgh, PA, 1998.
(13) (a) Ditchfield, R.; Hehre, W. J.; Pople, J. A. J. Chem. Phys. 1971, 54,
724–728. (b) Hehre, W. J.; Ditchfield, R.; Pople, J. A. J. Chem. Phys. 1972,
56, 2257–2261. (c) Hariharan, P. C.; Pople, J. A. Mol. Phys. 1974, 27, 209–
214. (d) Gordon, M. S. Chem. Phys. Lett. 1980, 76, 163–168. (e) Hariharan,
P. C.; Pople, J. A. Theor. Chim. Acta 1973, 28, 213–222.
(14) (a) Lee, C.; Yang, W.; Parr, R. G. Phys. Rev. B 1988, 37, 785–789.
(b) Becke, A. D. Phys. Rev. A 1988, 38, 3098–3100. (c) Becke, A. D J. Chem.
Phys. 1993, 98, 5648–5652.
Butyl-Substituted Cyclophene 5. To a suspension of zinc dust
(1.97 g, 30.2 mmol) in THF (50 mL) under nitrogen was added
TiCl4 (1.8 mL, 1.73 g/mL, 15.1 mmol) over a period of 30 min,
J. Org. Chem. Vol. 75, No. 13, 2010 4595