Convenient synthesis and photophysical properties of tetrabenzopentakisdehydro[12]annuleno[12]annulene

Article abstract of DOI:10.1246/cl.2004.972

A convenient synthesis of tetrabenzopentakisdehydro-[12]annuleno[12] annulene 2c with substantial solubility was achieved by double cyclization of tetrabromotolan 3 with o-diethynylbenzene 4.

Full text of DOI:10.1246/cl.2004.972

972
Chemistry Letters Vol.33, No.8 (2004)
Convenient Synthesis and Photophysical Properties
of Tetrabenzopentakisdehydro[12]annuleno[12]annulene
Motohiro Sonoda, Yu Sakai, Takashi Yoshimura, Yoshito Tobe,ꢀ and Kenji Kamaday
Department of Chemistry, Faculty of Engineering Science, Osaka University, and CREST,
Japan Science and Technology Agency (JST), Toyonaka, Osaka 560-8531
yPhotonics Research Institute, National Institute of Advanced Industrial Science and Technology (AIST),
Ikeda, Osaka 563-8577
(Received May 24, 2004; CL-040587)
A
convenient synthesis of tetrabenzopentakisdehydro-
[12]annuleno[12]annulene 2c with substantial solubility was
achieved by double cyclization of tetrabromotolan 3 with o-di-
ethynylbenzene 4.
Much attention has been focused in recent years on the de-
hydrobenzoannulene derivatives because of their potential as
functional materials such as nonlinear optical,1 conductive,2
and ferromagnetic materials3 and building blocks for the hitherto
unknown two-dimensional carbon networks,4 e.g., graphyne.
The ultimate carbon network was predicted to be moderately sta-
ble and to exhibit semiconductive as well as nonlinear optical
properties.5 Recently, Zhou and Feng reported that the ladder
oligomers of trisdehydrotribenzo[12]annulene, [12]DBA (1a),
would exhibit increasing second hyperpolarizabilities with in-
creasing number of the DBA unit based on the semi-empirical
molecular orbital calculations.6 Since the absorption ends of a
series of ladder oligomers would not exceed 350 nm, they pre-
dicted that these compounds would be promising as third-order
nonlinear optical materials. Although the parent [12]DBA 1a
and a number of its derivatives have been known for almost four
decades,7 a derivative of its dimer 2b has been prepared only re-
cently by Haley and co-workers.8,9 Despite the first synthesis of
2b utilizing protection/masking protocols was highly selective,
it required 13 steps and its solubility might not be enough to de-
termine its second hyperpolarizability. In this connection, we
planned to prepare tetrabenzopentakisdehydro[12]annuleno-
[12]annulene 2c having six alkyl chains, which would make it
soluble enough for the measurement of its photophysical proper-
ties. At the same time, we also planned to develop short and con-
venient method of the preparation of 2c that would also be appli-
cable to the synthesis of ladder oligomers. Namely, we
envisioned that 2c would be formed convergently from tetrabro-
motolan 3 and the protected o-diethynylbenzene 4 by the in-situ
deprotection Pd(0)-catalyzed coupling protocol developed by
Linstrumelle.10
Scheme 1. (a) (i) BTMABr3, K2CO3, CH2Cl2, rt, 87%; (ii)
(CH3)2CHCH2ONO, I2, C6H6, reflux, 70%. (b) Pd(PPh3)4, CuI,
Et3N, reflux, 62%. (c) (i) KOH, C6H6, reflux, 92%; (ii) 6,
Pd(PPh3)4, CuI, Et3N, reflux, 64%. (d) Br2, I2, Fe, CCl4, 0 ꢁC to
rt. (e) Pd(PPh3)4, CuI, piperidine, reflux, 65% for 4, 34% for 11
(2 steps from 9). (f) Pd(PPh3)4, CuI, PPh3, KOH, C6H6,
CH3N[(CH2)7CH3]3Cl, reflux, 9% for 2c, 5% for 1b.
followed by deaminative iodination using isoamyl nitrite and
12
I2 gave dibromoiodobenzene 6. Selective Sonogashira cou-
pling of 6 with 2-methyl-3-butyn-2-ol (7) occurred at the posi-
tion of iodo substituent, yielding ethynyldibromobenzene 8. De-
protection of the ethynyl end of 8 followed by the Sonogashira
coupling with 6 gave tetrabromotolan 3 in 22% overall yield
for 5 steps. Another building block 4 was prepared from 1,2-di-
chlorobenzene. 1,2-Didecylbenzene (9) was prepared from 1,2-
dichlorobenzene by the Tamao–Kumada–Corriu coupling13 us-
ing a Ni catalyst and n-decylmagnesium bromide. 4,5-Dibro-
mo-1,2-didecylbenzene (10),14 which was derived by bromina-
tion of 9, was reacted with excess 7 (9 equiv.) under the
Sonogashira coupling conditions to give diethynylbenzene 4 in
40% overall yield for 3 steps. The double cyclization of tetrabro-
motolan 3 with diethynylbenzene 4 using a palladium complex
and a copper salt in the presence of a phase-transfer catalyst10
gave the desired annulene 2c in 9% yield. Though the yield of
the final step is not good, each macrocyclization was estimated
to proceed in about 30% yield. Moreover, by this method a few
hundred milligrams of 2c was readily prepared in several steps.
As a reference compound we also prepared [12]DBA deriv-
ative 1b. Thus, cyclotrimerization10 of bromoethynylbenzene
11, derived by coupling of 10 with 1.6 equiv. of acetylene 7,
gave 1b in 5% yield.
In the 1H NMR spectrum, it shows only two singlets for ar-
omatic protons at ꢀ 7.07 and 6.93 ppm.15 In the 13C NMR spec-
trum, seven aromatic and three acetylenic carbon peaks are ob-
served. These spectral data are consistent with the highly
symmetrical structure of 2c.16 Attempts to obtain X-ray quality
crystals of 2c have been unsuccessful.
The building block 3 was prepared from 4-decylaniline (5)
11
as shown in Scheme 1. Dibromination of 5 using BTMABr3
Copyright Ó 2004 The Chemical Society of Japan

Chemistry Letters Vol.33, No.8 (2004)
973
J., 6, 2044 (2000). For recent reviews, see: b) J. A. Marsden, G. J.
Palmer, and M. M. Haley, Eur. J. Org. Chem., 2003, 2355. c) M. M.
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Kinder, C. A. Tessier, and W. J. Youngs, Synlett, 1993, 149. For
a recent review, see: c) W. J. Youngs, C. A. Tessier, and J. D.
Bradshaw, Chem. Rev., 99, 3153 (1999).
The electronic absorption spectra of 1b and 2c are shown in
Figure 1a. While the absorption spectrum of 1b is similar to that
of 1a,7a it exhibits a bathochromic shift (ca. 10 nm) relative to
that of 1a.17 The absorption of 2c shows further bathochromic
shift with an absorption maximum at 312 nm (" ¼ 4:5 ꢂ 105).
Absorption bands of 2c in the low energy region exhibit vibra-
tional fine structures (ꢁmax ¼ 433, 461 nm). Figure 1b shows
the fluorescence emission spectra of 1b and 2c. Like the absorp-
tion spectrum, the fluorescence emission spectrum of 2c exhibits
well resolved vibrational structures, reflecting the rigidity of the
macrocyclic framework. The quantum yields of the fluorescence
of 1b and 2c were determined to be 0.08 and 0.06, respectively,
which are slightly smaller than that of 1a (ꢀ ¼ 0:15).18
5
6
7
8
9
J. M. Kahoe, J. H. Kiley, J. J. English, C. A. Johnson, R. C.
Petersen, and M. M. Haley, Org. Lett., 2, 969 (2000).
For a [12]annuleno[12]annulene of different connectivity, see:
´
Ref. 8 and a) O. S. Miljanic, K. P. C. Vollhardt, and G. D. Whitener,
Synlett, 2003, 29. b) M. Iyoda, S. Sirinintasak, Y. Nishiyama, A.
Vorasingha, F. Sultana, K. Nakao, Y. Kuwatani, H. Matsuyama,
M. Yoshida, and Y. Miyake, Synthesis, in press.
10 a) C. Huynh and G. Linstrumelle, Tetrahedron, 44, 6337 (1988).
For the use of tricaprylmethylammonium salt in this reaction: b)
M. Ohkita, K. Ando, T. Suzuki, and T. Tsuji, J. Org. Chem., 65,
4385 (2000).
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M. Fujikawa, and T. Okamoto, Bull. Chem. Soc. Jpn., 61, 597
(1988). b) S. Kajigaeshi, T. Kakinami, H. Tokiyama, T. Hirakawa,
and T. Okamoto, Bull. Chem. Soc. Jpn., 60, 2667 (1987).
12 L. Friedman and J. F. Chlebowski, J. Org. Chem., 33, 1636 (1968).
13 a) K. Tamao, K. Sumitani, and M. Kumada, J. Am. Chem. Soc., 94,
4374 (1972). b) R. J. Corriu and J. P. Masse, Chem. Commun.,
1972, 144.
Figure 1. (a) Electronic absorption spectra of 1b (dashed line) and
2c (solid line) in CH2Cl2. (b) Fluorescence emission spectra of 1b
(dashed line) and 2c (solid line) in CH2Cl2 (5 ꢂ 10ꢃ6 M).
Next we inspected the third-order nonlinear optical proper-
ties of annulenes 1b and 2c to examine the theoretical prediction
of their second hyperpolarizabilities reported by Zhou and
Feng.6 They estimated that the static, orientationally averaged
values hꢂi of the second hyperpolarizability are 1:51 ꢂ 105 au
(equiv. to 1:27 ꢂ 10ꢃ35 esu)19 for 1a and 6:54 ꢂ 105 au (5:49 ꢂ
10ꢃ35 esu) for the parent 2a. We measured the nonlinear refrac-
tive index change and nonlinear absorption of the annulenes in
chloroform solutions (56 mM for 1b and 27 mM for 2c) by fem-
to-second Z-scan method20 at 1345 nm. However, the signals ob-
served for both solutions agreed with that of the blank solvent
within our experimental error (5% for nonlinear refractive, i.e.
closed aperture, measurements and 1% for nonlinear refractive,
i.e. open aperture, measurements). These results suggest that the
off-resonant ꢂ values of 1b and 2c are not larger than ꢄ4 ꢂ
10ꢃ35 esu.
In conclusion, a convenient synthesis of [12]annuleno[12]-
annulene 2c with substantial solubility was achieved by double
cyclization of tetrabromodiphenyltolan 3 with o-diethynylben-
zene 4. The annulene 2c and its parent annulene 1b did not show
obvious second hyperpolarizabilities contrary to the theoretical
predictions for the hyperpolarizabilities of a series of ladder
oligomers of annulenes.
14 H. Nishi and S. Ueno, Nippon Kagaku Kaishi, 1989, 983.
15 The 1H NMR chemical shift did not move in a concentration range
of 3–20 mM, indicating the absence of self-association of 2c.
16 2c: mp 110–111 ꢁC; 1H NMR (CDCl3) ꢀ 7.07 (s, 4H), 6.93 (s, 4H),
2.53–2.40 (m, 12H), 1.53–1.28 (m, 96H), 0.88 (t, J ¼ 6:6 Hz, 18H);
13C NMR (CDCl3) ꢀ 143.5, 141.7, 132.7, 131.5, 127.5, 127.1,
123.9, 95.9, 92.9, 91.5, 35.3, 32.3, 31.9, 30.7, 30.6, 29.7, 29.62,
29.58, 29.51, 29.4, 29.3, 29.2, 22.7, 14.1; UV (CH2Cl2, 25 ꢁC)
ꢁmax (log ") 328 (5.0), 312 (5.7), 301 (5.3), 292 (5.2) nm; fluores-
cence (CH2Cl2, 25 ꢁC, ꢁex ¼ 312 nm) ꢁem ¼ 467, 498, 518 nm;
MS (MALDI (negative mode)) m=z 1263 (Mꢃ).
17 1b: UV (CH2Cl2, 25 ꢁC) ꢁmax (log ") 301 (5.5), 291 (5.0), 284
(5.0) nm; fluorescence (CH2Cl2, 25 ꢁC, ꢁex ¼ 301 nm) ꢁem
484, 498, 524 (sh) nm.
¼
18 The quantum yield of the fluorescence of 1a normalized with qui-
nine sulfate was reported to be 0.15 (in methylcyclohexane, at room
temperature): K. Janecka-Styrcz, J. Lipinski, and Z. Ruziewicz,
J. Lumin., 17, 83 (1978).
19 To convert second hyperpolarizability from in the atomic unit (au)
system to in the esu-cgs system, the following relation is used:
1 au ¼ 5:0366 ꢂ 10ꢃ40 esu. However, further conversion is needed
because, in theoretical studies, ꢂ is preferably defined as p ¼
ꢃF þ ð1=2ÞꢄFF þ ð1=6ÞꢂFFF . . .(Conversion I) while in many ex-
perimental researches, p ¼ ꢃF þ ꢄFF þ ꢂFFF . . .(Conversion II)
is preferred. Therefore, in the text, a factor of (5:0366 ꢂ 10ꢃ40=6)
was multiplied by the values in au in order to convert to the value
in esu with Conversion II. See: K. Kamada, M. Ueda, T. Sakaguchi,
K. Ohta, and T. Fukumi, J. Opt. Soc. Am. B, 15, 838 (1998).
20 For our experimental technique, see the following references
and the references herein: a) R. R. Tykwinski, K. Kamada, D.
Bykowski, F. A. Hegmann, and R. J. Hinkle, J. Opt. A: Pure Appl.
Opt., 4, S202 (2002). b) K. Kamada, K. Matsunaga, A. Yoshino,
and K. Ohta, J. Opt. Soc. Am. B, 20, 529 (2003).
References and Notes
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3
4
a) Y.-J. Pu, M. Takahashi, E. Tsuchida, and H. Nishide, Mol. Cryst.
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Published on the web (Advance View) July 5, 2004; DOI 10.1246/cl.2004.972