Facile synthesis of polycyclic aromatic hydrocarbons via a trisaryne equivalent

Article abstract of DOI:10.1246/cl.2005.56

1,3,5-Tris[4-trifluoromethanesulfonyloxy-3-(trimethylsilyl)-phenyl]benzene (1), a trisaryne equivalent, was synthesized. The Diels-Alder reaction or the palladium-catalyzed hexasilylation by use of 1 gave modest to excellent yields of diverse polyaromatic

Full text of DOI:10.1246/cl.2005.56

56
Chemistry Letters Vol.34, No.1 (2005)
Facile Synthesis of Polycyclic Aromatic Hydrocarbons via a Trisaryne Equivalent
Junnai Ikadai, Hiroto Yoshida, Joji Ohshita, and Atsutaka Kunaiꢀ
Department of Applied Chemistry, Graduate School of Engineering, Hiroshima University,
Higashi-Hiroshima 739-8527
(Received October 13, 2004; CL-041211)
1,3,5-Tris[4-trifluoromethanesulfonyloxy-3-(trimethylsilyl)-
phenyl]benzene (1), a trisaryne equivalent, was synthesized. The
Diels–Alder reaction or the palladium-catalyzed hexasilylation
by use of 1 gave modest to excellent yields of diverse polyaro-
matic hydrocarbons straightforwardly.
Z
R
F
1
Diels−Alder adduct
THF, rt
Arynes are among the most important reactive intermediates
in organic synthesis, which are readily convertible into a variety
of substituted arenes through pericyclic reactions, electrophilic
couplings, and transition metal-catalyzed reactions.1 In particu-
lar, the use of arynes, bearing plural strained triple bonds, in
these transformations has proven to be a powerful tool for the
synthesis of polycyclic aromatic hydrocarbons (PAHs),2 which
have attracted considerable attention in materials science due
to their shapes and other properties arising from their extended
delocalized ꢀ-systems.3 Herein we report the synthesis of 1,3,5-
tris[4-trifluoromethanesulfonyloxy-3-(trimethylsilyl)phenyl]-
benzene (1), a trisaryne equivalent, and its transformations to
PAHs or their silicon-containing-analogues via the Diels–Alder
reaction or the palladium-catalyzed hexasilylation.
O
O
O
5: 93% yield (24 h)
6: 78% yield (48 h)
OMe
OH
Br
Br
OMe
O
Br
a
b
Zn
AcOH
reflux
Br
Br
O
MeO
OMe
HO
OH
O
Br
Br
O
2
3
4
OTf
SiMe3
7: 89% yield (48 h)
8: 67% yield (24h)
Scheme 2.
c
d
e
With this trisaryne equivalent in hand, we first investigated
the Diels–Alder reaction with furan in the presence of a fluoride
ion (KF/18-crown-6), and observed that all of the three triple
bonds were efficiently trapped to afford 1,3,5-tris(5,8-dihydro-
5,8-epoxy-2-naphthyl)benzene (5) in 93% yield (Scheme 2).8
Similarly, the reaction with tetraphenylcyclopentadienone took
place smoothly with release of carbon monoxide, providing
1,3,5-tris(5,6,7,8-tetraphenyl-2-naphthyl)benzene (6) in 78%
yield. Moreover, 1,3-diphenylisobenzofuran was also coupled
with 1 to give 89% yield of 1,3,5-tris(9,10-diphenyl-9,10-ep-
oxy-2-anthryl)benzene (7), which could be further converted in-
to 1,3,5-tris(9,10-diphenyl-2-anthryl)benzene (8)9 in 67% yield
under reductive deoxygenation conditions.10 Although the syn:
anti ratio of 7 was elucidated to be ca. 1:3 by 13C NMR spec-
trometry, we could not determine the diastereoselectivity of 5.
Figure 1 depicts the absorption and emission spectra of 8, in
comparison with those of 9,10-diphenylanthracene (DPA). The
Me3Si
TfO
OTf
SiMe3
1
Scheme 1. (a) Tf2O, toluene, reflux, 55%; (b) HBr, AcOH,
75 ꢁC, 67%; (c) HMDS, 70 ꢁC; (d) Me3SiCl, Na, toluene, reflux;
(e) (i) n-BuLi, Et2O, 0 ꢁC to rt; (ii) Tf2O, 0 ꢁC to rt, 27% (from
4).
Trisaryne equivalent 14 was prepared from readily available
3-bromo-4-methoxyacetophenone (2)5 as shown in Scheme 1.
According to a literature procedure,6 condensation of 2 in the
presence of Tf2O gave 1,3,5-tris(3-bromo-4-methoxyphenyl)-
benzene (3). Subsequent cleavage of the phenolic ether moieties
in 3 with HBr provided 4, which was converted into 1 in a similar
manner to the preparation of a simple aryne precursor (10%
overall yield from 2).7
Copyright Ó 2005 The Chemical Society of Japan

Chemistry Letters Vol.34, No.1 (2005)
57
250000
600
500
400
300
200
100
0
was also added to the trisaryne to offer 32% yield of 11, contain-
ing three benzodisilocine moieties.
In conclusion, we have disclosed the synthesis of the tris-
aryne equivalent and its utilization for assembling diverse PAHs
via the Diels–Alder reaction or the palladium-catalyzed hexasi-
lylation. Further studies on synthetic application of the trisaryne
equivalent to the construction of other PAHs are in progress.
← (i)
200000
← (iii)
150000
100000
50000
0
↑
(iv)
←
(v)
←
(ii)
This work was financially supported in part by the Sasakawa
Scientific Research Grant from The Japan Science Society. We
also thank Ms. Mihoko Yanai, the Natural Science Center
for Basic Research and Development (N-BARD) Hiroshima
University, for HRMS measurement.
200
300
400
500
600
Wavelength / nm
References and Notes
Figure 1. Absorption: (i) = 8, (ii) = DPA, Fluorescence:
(iii) = 8 (ꢃex ¼ ꢃmax), (iv) = 8 (ꢃex ¼ 350 nm), (v) = DPA
(ꢃex ¼ 350 nm);
absorption and emission maxima of 8 were somewhat red-shift-
ed from those of DPA probably owing to the elongated conjuga-
tion in 8, while the quantum yield of 8 (ꢀF ¼ 0:44) was lower
than that of DPA (ꢀF ¼ 0:90).
1
2
H. Pellissier and M. Santelli, Tetrahedron, 59, 701 (2003).
a) P. R. Ashton, U. Girreser, D. Giuffrida, F. H. Kohnke, J. P.
Mathias, F. M. Raymo, A. M. Z. Slawin, J. F. Stoddart, and
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¨
¨
Ber., 126, 2351 (1993). c) M. Loffler and A. D. Schluter, Synlett,
¨
1994, 75. d) A. Winling and R. A. Russell, J. Chem. Soc., Perkin
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J. Am. Chem. Soc., 126, 11168 (2004).
The trisaryne equivalent was found to be applicable to the
palladium-catalyzed coupling reaction with cyclic disilanes
(Scheme 3).11 Thus, treatment of 1 with a five-membered cyclic
disilane, 1,1,2,2-tetramethyl-1,2-disilacyclopentane or 1,1,2,2-
tetramethyl-1,2-(1,8-naphthylene)disilane, in the presence of a
palladium–t-OcNC complex provided the corresponding hexasi-
lylated products (9 or 10) in 38 or 16% yield, where all triple
bonds were inserted into the Si–Si ꢁ-bond. A six-membered cy-
clic disilane, 1,1,2,2-tetramethyl-1,2-(2,20-biphenylene)disilane,
3
4
a) A. J. Berresheim, M. Muller, and K. Mullen, Chem. Rev., 99,
¨ ¨
1747 (1999). b) M. D. Watson, A. Fechtenkotter, and K. Mullen,
Chem. Rev., 101, 1267 (2001).
1; 1H NMR (CDCl3) ꢂ 0.43 (s, 27 H), 7.47 (d, J ¼ 8:4 Hz, 3 H),
7.68 (s, 3 H), 7.70 (dd, J ¼ 8:4, 2.4 Hz, 3 H), 7.77 (d, J ¼ 2:4
Hz, 3 H); 13C NMR (CDCl3) ꢂ ꢂ0:8, 118.5 (q, J ¼ 320 Hz),
120.1, 125.9, 130.2, 133.5, 135.2, 140.0, 141.5, 154.8; Anal.
Calcd for C36H39O9F9S3Si3: C, 44.71; H, 4.06%. Found: C,
44.73; H, 3.99%.
¨
¨
KF
18-Crown-6
Pd(OAc) (12 mol%)
2
t-OcNC (36 mol%)
R
SiMe
SiMe
2
2
+
1
Hexasilylated product
THF, rt
n
5
6
K. Miyazawa, T. Inukai, H. Inoue, S. Saitou, and K. Ono,
Jpn. Kokai Tokkyo Koho 63048254 (1988); Chem. Abstr.,
109, 120286p (1988).
n: 1, 2
´
a) A. Jutand and S. Negri, Eur. J. Org. Chem., 1998, 1811. b) Y.
Me Si
2
Me Si
2
Yamamoto, C. Hideshima, Y. Nagano, and M. Tashiro, J. Chem.
Res., Synop., 28, 266 (1996).
SiMe
SiMe
2
2
7
8
Y. Himeshima, T. Sonoda, and H. Kobayashi, Chem. Lett., 1983,
1211.
Me
Si
Me
Si
2
2
A THF solution (1.0 mL) of 1 (0.195 g, 0.20 mmol), a 1,3-diene
(0.90 mmol), 18-Crown-6 (0.334 g 1.26 mmol) and KF (0.071 g,
1.23 mmol) was stirred for the time specified in Scheme 2.
The mixture was diluted with ethyl acetate, washed with brine
and concentrated. The residue was purified by GPC to give
the corresponding product.
SiMe
SiMe
2
2
Si
Me2
Si
Me
2
Me Si
Me Si
2
2
9: 38% yield (24 h)
10: 16% yield (24 h)
1
9
8; H NMR (50 ꢁC) (CDCl3) ꢂ 7.34 (dd, J ¼ 6:8, 3.4 Hz, 6 H),
7.43–7.62 (m, 36 H), 7.70 (dd, J ¼ 6:8, 2.9 Hz, 6 H), 7.74
(dd, J ¼ 8:8, 1.9 Hz, 3 H), 7.90 (s, 3 H); 13C NMR (50 ꢁC)
(CDCl3) ꢂ 124.8, 125.1, 125.2, 125.3, 125.7, 127.0, 127.6,
127.67, 127.72, 128.5, 129.2, 130.0, 130.2, 130.5, 131.3,
131.4, 137.1, 137.4, 137.6, 138.9, 139.1, 142.5; HRMS (FAB)
Calcd for C84H54: 1062.4226, Found 1062.4240.
Me Si
2
SiMe
2
Me
Si
2
SiMe
2
10 a) G. Witting, E. Knauss, and K. Neithammer, Justus Liebigs
Ann. Chem., 630, 10 (1960). b) G. S. Reddy and M. V. Bhatt,
Tetrahedron Lett., 21, 3627 (1980).
SiMe
2
Me Si
2
11 a) H. Yoshida, J. Ikadai, M. Shudo, J. Ohshita, and A. Kunai, J.
Am. Chem. Soc., 125, 6638 (2003). b) H. Yoshida, K. Tanino, J.
Ohshita, and A. Kunai, Angew. Chem., Int. Ed., 43, 5052 (2004).
11: 32% yield (24 h)
Scheme 3.
Published on the web (Advance View) December 4, 2004; DOI 10.1246/cl.2005.56