Efficient conversion of acetophenones into 1,3,5-triarylbenzenes catalyzed by bismuth(III) trifluoromethanesulfonate tetrahydrate

Article abstract of DOI:10.1055/s-2008-1078012

Bismuth(III) trifluoromethanesulfonate tetrahydrate is found to efficiently catalyze the cyclotrimerization of acetophenones into 1,3,5-triarylbenzenes in good yields. Georg Thieme Verlag Stuttgart.

Full text of DOI:10.1055/s-2008-1078012

LETTER
2365
Efficient Conversion of Acetophenones into 1,3,5-Triarylbenzenes Catalyzed
by Bismuth(III) Trifluoromethanesulfonate Tetrahydrate
C
onversion of
u
A
cetopheno
m
ne
s
into 1,3, 5-Triary
i
lbenze
a
nes ki Ono, Yuichi Ishikura, Yuusuke Tada, Masato Endo, Tsuneo Sato*
Department of Life Science, Kurashiki University of Science and the Arts, Kurashiki 712-8505, Japan
Fax +81(86)4401062; E-mail: sato@chem.kusa.ac.jp
Received 14 April 2008
Table 1 Cyclotrimerization of Acetophenone in the Presence of
Abstract: Bismuth(III) trifluoromethanesulfonate tetrahydrate is
found to efficiently catalyze the cyclotrimerization of acetophe-
nones into 1,3,5-triarylbenzenes in good yields.
Various Lewis Acidsa
Ph
O
Key words: bismuth(III) trifluoromethanesulfonate, catalysis, ke-
Lewis acid
tones, Lewis acids, 1,3,5-triarylbenzenes
toluene, reflux
Ph
Ph
Ph
Entry
1
Lewis acid
Amberlyst 15c
TfOH
Yield (%)b
1,3,5-Triarylbenzenes are useful compounds in the fields
of electrode and electroluminescent devices1 and resist
materials2 or in the chemistry of conducting polymers.3
Their preparation via triple condensation of aryl methyl
ketones has been regarded as a useful general method and
has been extensively studied.4 Acid catalysts such as dry
3
2
55
3
AlCl3
0
4
SiCl4
0
8
HCl,4,5 PTSA/SnCl4,6 SiCl4,7 TiCl4 , TiCl3(OTf),9 and sol-
id acid catalysts10 are widely used for this transformation.
However, these methods often involve the use of large
amounts of catalysts which are expensive, moisture sensi-
tive, toxic, and produce unsatisfactory yields, especially
with ortho-substituted acetophenones.5,10b Therefore, the
introduction of a new and efficient method for this trans-
formation is still in demand. Recently, bismuth(III) tri-
fluoromethanesulfonate has attracted the attention of
synthetic organic chemists because it is relatively nontox-
ic, readily available at low cost, and is fairly insensitive to
small amounts of water. Owing to its unique catalytic
properties, bismuth(III) trifluoromethanesulfonate has
been extensively used for a plethora of organic transfor-
mations.11 However, there have been no reports on the use
of bismuth(III) trifluoromethanesulfonate for the cyclotri-
merization of acetophenones into 1,3,5-triarylbenzenes.
Here, we wish to report that bismuth(III) trifluo-
romethanesulfonate tetrahydrate (2.0 mol%) is a very ef-
ficient catalyst for the cyclotrimerization of
acetophenones into 1,3,5-triarylbenzenes (Scheme 1).
5
Me3SiOTf
Sc(OTf)3
TiCl4
43
6
0
7
0
8
TiCl3(OTf)d
FeCl3
14
9
0
10
11
12
13
14e
15
16
17
ZrCl4
0
InBr3
0
SnCl4
0
Bi(OTf)3·4H2O
Bi(OTf)3·4H2O
Bi(NO3)2
Bi2(SO4)3
BiCl3
85 (80)
(74)
0
0
0
a Reaction conditions: PhCOMe (6.0 mmol), Lewis acid (0.12 mmol),
toluene (3 mL), reflux, 5 h, unless otherwise noted.
b Based on GC. Isolated yield is given in the parentheses.
c Amberlyst 15 (100 mg) was used.
First, the cyclotrimerization of acetophenone was carried
out in the presence of various Lewis acids (2.0 mol%) in
toluene at refluxing temperature for five hours (Table 1).
d Prepared in situ from TiCl4 (0.12 mmol) and AgOTf (0.12 mmol).
e Bi(OTf)3·4H2O (0.024 mmol), 32 h.
Ar
O
Bi(OTf)3⋅4H2O (2.0 mol%)
3
3 H2O
+
After screening various conditions, we found that
Bi(OTf)3·4H2O is a very effective catalysis for the cyclo-
trimerization reaction (entry 13).
Ar
Ar
Ar
Scheme 1
Among bismuth(III) salts screened, we found
Bi(OTf)3·4H2O to be effective, while inferior results were
obtained with Bi(NO3)3, Bi2(SO4)3, and BiCl3 (entries 15–
17). Even with 0.40 mol% of Bi(OTf)3·4H2O, this trans-
SYNLETT 2008, No. 15, pp 2365–2367
Advanced online publication: 31.07.2008
DOI: 10.1055/s-2008-1078012; Art ID: U03208ST
© Georg Thieme Verlag Stuttgart · New York
1
5
.0
9
.2
0
0
8

2366
F. Ono et al.
LETTER
formation proceeded well, but took longer to complete ylphenyl)phenyl]-2-methylbenzene, which is a key inter-
(entry 14).
mediate for the synthesis of truxenone,7c in 71% yield.14
We next examined the same reaction using various struc- In a similar manner, 2-chloroacetophenone and 2,5-
turally diverse para- and meta-substituted acetophenones dimethylacetophenone15 underwent smooth cyclotrimer-
(Table 2). As shown in Table 2, acetophenones carrying ization to furnish the desired products in 80% and 70%
either electron-withdrawing or electron-donating groups yields, respectively.
could be efficiently converted into the corresponding
1,3,5-triarylbenzenes in good yields.
A typical procedure is as follows (Table 1, entry 13): To a
mixture of Bi(OTf)3·4H2O16 (87.4 mg, 0.12 mmol) and
toluene (3 mL), acetophenone (721 mg, 6.0 mmol) was
Table 2 Cyclotrimerization of Acetophenones into 1,3,5-Triaryl-
added. After the reaction mixture was kept stirring at re-
flux for five hours, it was quenched by adding saturated
NaHCO3 (15 mL). The resulting mixture was extracted
with CH2Cl2 (2 × 40 mL). The combined extracts were
washed with saturated NaCl (10 mL). The organic layer
was dried (Na2SO4) and concentrated. A GC analysis in-
dicated the formation of 1,3,5-triphenylbenzene in 85%
yield relative to n-C20H42 as an internal standard. The res-
idue was chromatographed on silica gel (20% CH2Cl2–
hexane) to afford pure 1,3,5-triphenylbenzene (490 mg,
80%).17
benzenes Using Bi(OTf)3·4H2Oa
Ar
O
Bi(OTf)3•4H2O
Ar
toluene, reflux
Ar
Ar
Entry
Ar
Time (h)
Yield (%)b
1
2
Ph
5
7
80
82
74
90
79
73
72
76
78
80
4-MeC6H4
4-Me2CHC6H4
4-PhC6H4
4-FC6H4
4-ClC6H4
4-BrC6H4
4-IC6H4
3-MeC6H4
3-ClC6H4
3
4.5
4
In conclusion, we have demonstrated an efficient method
for cyclotrimerization of acetophenones catalyzed by
Bi(OTf)3·4H2O. Further study on Bi(OTf)3·4H2O-cata-
lyzed reaction is currently under way in our laboratory.
4
5
18
5.5
11
4.5
4
6
7
References and Notes
(1) (a) Lindeman, S. V.; Struchkov, Yu. T.; Michailov, V. N.;
Rusanov, A. L. Izv. Akad. Nauk. Ser. Khim. 1994, 1986;
Chem. Abstr. 1995, 123, 32717p. (b) Aslam, M.; Aguilar,
D. A. WO 9314065, 1993; Chem. Abstr. 1993, 119,
270793x. (c) Plater, M. J.; McKay, M.; Jackson, T. J. Chem.
Soc., Perkin Trans. 1 2000, 2695.
(2) (a) Kadota, T.; Kageyama, H.; Wakaya, F.; Gamo, K.;
Shirota, Y. Chem. Lett. 2004, 706. (b) Shirota, Y. J. Mater.
Chem. 2005, 15, 75. (c) Ikadai, J.; Yoshida, H.; Ohshita, J.;
Kunai, A. Chem. Lett. 2005, 34, 56.
8
9
10
13
a Reaction conditions: ArCOMe (6.0 mmol), Bi(OTf)3·4H2O (0.12
mmol), toluene (3 mL), reflux.
b Isolated yield.
(3) (a) Rebourt, E.; Pepin-Donat, B.; Dinh, E. Polymer 1995, 36,
399. (b) Viallat, A.; Pepin-Donat, B. Macromolecules 1997,
30, 4679. (c) Pepin-Donat, B.; de Geyer, A.; Viallat, A.
Polymer 1998, 39, 6673.
(4) For a review, see: Wirth, H. O.; Kern, W.; Schmitz, E.
Makromol. Chem. 1963, 68, 69.
The noteworthy feature of our protocol is that ortho-sub-
stituted acetophenones, which are difficult to undergo cy-
clotrimerization by other methods,5,10b,12 could be easily
converted into the corresponding 1,3,5-triarylbenzenes
(Scheme 2). For example, treatment of 2-methylacetophe-
none with Bi(OTf)3·4H2O (2.0 mol%) at 140 °C for four
hours under neat conditions13 afforded 1-[3,5-bis(2-meth-
(5) Lyle, R. E.; DeWitt, E. J.; Nichols, N. M.; Cleland, W. J. Am.
Chem. Soc. 1953, 75, 5959.
R2
O
R1
R1
Bi(OTf)3⋅4H2O (2.0 mol%)
R1
R2
neat, 140 °C
R2
R1
R2
R1 = Me; R2 = H, 4 h, 71%
R
R
1 = Cl; R2 = H, 18 h, 80%
1 = R2 = Me, 13 h, 70%
Scheme 2
Synlett 2008, No. 15, 2365–2367 © Thieme Stuttgart · New York

LETTER
Conversion of Acetophenones into 1,3,5-Triarylbenzenes
2367
(6) (a) Jin, X.; Xu, F.; Zhu, Q.; Ren, X.; Yan, C.; Wang, L.;
Wang, J. Synth. Commun. 2005, 35, 3167. (b) Jin, X.; Xu,
F.; Zhu, Q.; Ren, X.; Li, D.; Yan, C.; Shi, Y. Indian J. Chem.,
Sect. B: Org. Chem. Incl. Med. Chem. 2006, 45, 2781.
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1991, 32, 4175. (b) Elmorsy, S. S.; Pelter, A.; Smith, K.;
Hursthouse, M. B.; Ando, D. Tetrahedron Lett. 1992, 33,
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(8) Li, Z.; Sun, W.-H.; Jin, X.; Shao, C. Synlett 2001, 1947.
(9) Iranpoor, N.; Zeynizaded, B. Synlett 1998, 1079.
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(c) Yamata, T.; Hideshima, C.; Nagano, Y.; Tashiro, M.
J. Chem. Res., Synop. 1996, 266.
(11) For reviews on bismuth(III) trifluoromethanesulfonate, see:
(a) Antoniotti, S. Synlett 2003, 1566. (b) Gaspard-
Iloughmane, H.; Le Roux, C. Eur. J. Org. Chem. 2004,
2517. For recent leading references, see: (c) Kamal, A.;
Ahmed, S. K.; Sandbhor, M.; Khan, M. N. A.; Arifuddin, M.
Chem. Lett. 2005, 1142. (d) Anderson, E. D.; Ernat, J. J.;
Nguyen, M. P.; Palma, A. C.; Mohan, R. S. Tetrahedron
Lett. 2005, 46, 7747. (e) Lacey, J. R.; Anzalone, P. W.;
Duncan, C. M.; Hackert, M. J.; Mohan, R. S. Tetrahedron
Lett. 2005, 46, 8507. (f) Ollevier, T.; Li, Z. Org. Biomol.
Chem. 2006, 4, 4440. (g) Ollevier, T.; Nadeau, E. Synlett
2006, 219. (h) Adinolfi, M.; Iadonisi, A.; Ravida, A.;
Valerio, S. Tetrahedron Lett. 2006, 47, 2595. (i) Ollevier,
T.; Mwene-Mbeja, T. M. Tetrahedron Lett. 2006, 47, 4051.
(j) Callens, E.; Burton, A. J.; Barrett, A. G. M. Tetrahedron
Lett. 2006, 47, 8699.
(12) To the best of our knowledge, there are only two successful
reports4,7c on the use of this type of compound in the
cyclotrimerization process.
(13) The reaction was very slow in refluxing toluene (12 h, 17%).
(14) Cyclotrimerization of 2-methylacetophenone by the Wirth
method [dry HCl(excess), (EtO)3CH (1.2 equiv), EtOH, r.t.,
24 h]4 and the Elmorsy method [SiCl4 (1.0 equiv), EtOH, D,
24 h]7c gave the product in 26% and 32% yields,
respectively.
(15) No desired product was obtained by Nafion-H-catalyzed
cyclotrimerization of 2,5-dimethylacetophenone.10b
(16) Bismuth(III) trifluoromethanesulfonate tetrahydrate was
prepared according to the method described in the literature:
Labrouillere, M.; Le Roux, C.; Gaspard, H.; Laporterie, A.;
Dubac, J. Tetrahedron Lett. 1999, 40, 285.
Mp 174.1–174.7 °C (Lit.4 175–176 °C). MS (EI): m/z = 306
[M]+.
1,3,5-Tris(4-methylphenyl)benzene
Mp 175.7–176.9 °C (Lit.5 178 °C). MS (EI): m/z = 348 [M]+.
1,3,5-Tris[4-(methylethyl)phenyl]benzene
Mp 167.5–168.1 °C (Lit.5 166 °C). MS (EI): m/z = 432 [M]+.
1,3,5-Tris(4-phenylphenyl)benzene
Mp 236.2–238.0 °C (Lit.4 241 °C). MS (EI): m/z = 534 [M]+.
1,3,5-Tris(4-fluorophenyl)benzene
Mp 236.5–238.0 °C (Lit.5 238 °C). 1H NMR (500 MHz,
CDCl3): d = 7.17 (t-like, J = 8.6 Hz, 6 H), 7.61–7.65 (m, 6
H), 7.66 (s, 3 H). 13C NMR (125 MHz, CDCl3): d = 115.8 (d,
J = 21.6 Hz), 124.8, 128.9 (d, J = 8.3 Hz), 137.0 (d, J = 4.1
Hz), 141.5, 162.7 (d, J = 245.8 Hz). MS (EI): m/z = 360
[M]+.
1,3,5-Tris(4-chlorophenyl)benzene
Mp 244.1–244.9 °C (Lit.5 246 °C). MS (EI): m/z = 408 [M]+.
1,3,5-Tris(4-bromophenyl)benzene
Mp 260.2–260.9 °C (Lit.5 262 °C). MS (EI): m/z 539 [M]+.
1,3,5-Tris(4-iodophenyl)benzene
Mp 264.6–265.9 °C (Lit.5 265 °C). MS (EI): m/z = 683 [M]+.
1,3,5-Tris(3-methylphenyl)benzene
Mp 116.8–118.1 °C (Lit.4 118 °C).1H NMR (500 MHz,
CDCl3): d = 2.45 (s, 9 H), 7.21 (d, J = 7.7 Hz, 3 H), 7.37 (t,
J = 7.7 Hz, 3 H), 7.50 (d, J = 7.7 Hz, 3 H), 7.51 (s, 3 H), 7.75
(s, 3 H). 13C NMR (125 MHz, CDCl3): d = 21.6, 124.4,
125.1, 128.1, 128.2, 128.7, 138.4, 141.2, 142.3. MS (EI): m/
z = 348 [M]+.
1,3,5-Tris(3-chlorophenyl)benzene
Mp 172.4–173.0 °C (Lit.5 171 °C). MS (EI): m/z = 408 [M]+.
1,3,5-Tris(2-methylphenyl)benzene
Mp 135.6–135.8 °C (Lit.4 134–135 °C). 1H NMR (500 MHz,
CDCl3): d = 2.37 (s, 9 H), 7.22–7.34 (m, 15 H). 13C NMR
(125 MHz, CDCl3): d = 20.6, 125.8, 127.3, 128.5, 129.9,
130.4, 135.4, 141.5, 141.7. MS (EI): m/z = 348 [M]+.
1,3,5-Tris(2-chlorophenyl)benzene
Mp 165.1–165.5 °C. 1H NMR (500 MHz, CDCl3): d = 7.28–
7.36 (m, 6 H), 7.45–7.52 (m, 6 H), 7.58 (s, 3 H). 13C NMR
(125 MHz, CDCl3): d = 126.9, 128.7, 129.8, 130.1, 131.6,
132.6, 138.9, 139.9. MS (EI): m/z = 408 [M]+. HRMS (EI):
m/z calcd for C24H15Cl3: 408.0242; found: 408.0236.
1,3,5-Tris(2,5-dimethylphenyl)benzene
Mp 148.3–149.4 °C (Lit.4 149 °C). 1H NMR (500 MHz,
CDCl3): d = 2.32 (s, 9 H), 2.35 (s, 9 H), 7.08 (d, J = 8.0 Hz,
3 H), 7.15 (s, 3 H), 7.17 (d, J = 8.0 Hz, 3 H), 7.26 (s, 3 H).
13C NMR (125 MHz, CDCl3): d = 20.2, 20.9, 127.9, 128.4,
130.3, 130.6, 132.2, 135.2, 141.5, 141.6. MS (EI): m/z = 390
[M]+.
(17) Selected Physical and Spectroscopic Data
1,3,5-Triphenylbenzene
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