Highly efficient and novel method for synthesis of 1,3,5-triarylbenzenes from acetophenones

Article abstract of DOI:10.1080/00397910902885533

Heteropolyacid-phosphomolybdic acid has been found to be an efficient and recyclable catalyst for cyclotrimerization of acetophenones into 1,3,5-triarylbenzenes in good yields.

Full text of DOI:10.1080/00397910902885533

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Highly Efficient and Novel
Method for Synthesis of
1,3,5-Triarylbenzenes from
Acetophenones
Kiran Phatangare a , Vikas Padalkar a , Devidas
Mhatre a , Ketan Patil a & Atul Chaskar a b
a C. K. Thakur Research Centre, Navi Mumbai, India
b Department of Chemistry, Material and Engineering
Chemistry, “Giulio Natta” Politecnico di Milano,
Milan, Italy
Version of record first published: 16 Oct 2009.
To cite this article: Kiran Phatangare , Vikas Padalkar , Devidas Mhatre , Ketan Patil
& Atul Chaskar (2009): Highly Efficient and Novel Method for Synthesis of 1,3,5-
Triarylbenzenes from Acetophenones, Synthetic Communications: An International
Journal for Rapid Communication of Synthetic Organic Chemistry, 39:22, 4117-4121
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Synthetic Communications1, 39: 4117–4121, 2009
Copyright # Taylor & Francis Group, LLC
ISSN: 0039-7911 print=1532-2432 online
DOI: 10.1080/00397910902885533
Highly Efficient and Novel Method for Synthesis
of 1,3,5-Triarylbenzenes from Acetophenones
Kiran Phatangare,1 Vikas Padalkar,1 Devidas Mhatre,1 Ketan Patil,1
and Atul Chaskar1,2
1C. K. Thakur Research Centre, Navi Mumbai, India
2Department of Chemistry, Material and Engineering Chemistry,
‘‘Giulio Natta’’ Politecnico di Milano, Milan, Italy
Abstract: Heteropolyacid–phosphomolybdic acid has been found to be an
efficient and recyclable catalyst for cyclotrimerization of acetophenones into
1,3,5-triarylbenzenes in good yields.
Keywords: Acetophenones, heteropolyacid, 1,3,5-triarylbenzenes
1,3,5-Triarylbenzenes gained importance because of their uses in
electrode and electroluminescent devices, such as photocopiers and laser
printers,[1–3] resist materials,[4] and conducting polymers.[5] Triarylben-
zenes have been made by condensation of aryl acetones in various acidic
media, such as HCl, H2SO4, TiCl4, SiCl4, AlCl3, SnCl4, para toluene
sulfonic acid (PTSA), Bi(OTf)3 ꢀ 4H2O, BiCl3, FeCl3, and Amberlyst-15,
which are widely used for this transformation.[6–16] However, in spite of
their potential utility, these methods typically suffer from one or more
disadvantages, such as high cost, use of a stoichiometric amount of cat-
alyst, moisture sensitivity, specialized handling, tedious workup, and
nonrecyclability of the catalyst.
In recent decades, heteropolyacids (HPAs) as catalysts have become
important in pharmaceutical and fine chemical industries.[17] HPAs are
more active catalysts than conventional inorganic and organic acids for
Received December 10, 2008.
Address correspondence to Atul Chaskar, C. K. Thakur Research Centre,
Navi Mumbai 410206, India. E-mail: achaskar@rediffmail.com
4117

4118
K. Phatangare et al.
Scheme 1. Cyclotrimerization of acetophenone.
various reactions in solution.[18] Solid HPAs have gained importance
because of easy workup procedures, minimization of waste, mild reaction
conditions, cleaner products, enhancement in selectivity, and improved
reaction rates. They are noncorrosive and environmentally benign,
because they can be recycled and reused.[19]
Thus, considering the advantage and applications of HPAs and as
part of our ongoing project to explore the catalytic activities of HPAs
in organic transformations,[20,21] we attempted the convenient and prac-
tical synthesis of 1,3,5-triarylbenzenes using phosphomolybdic acid
(Scheme 1).
To compare catalytic efficiency of phosphomolybdic acid with
different acid catalysts, the cyclotrimerization of acetophenone with
5–10 mol% of acid catalyst in ethanol at reflux temperature was investi-
gated. Results are shown in Table 1.
The results mentioned in Table 1 demonstrate the effective use
of phosphomolybdic acid for the cyclotrimerization reaction. The
Table 1. Effect of different acid catalysts on percentage yield of
cyclotrimerization of acetophenone
Entry
Acid catalyst
Mole (%)
Time (h)
Yield (%)b
1
2
3
4
5
6
7
8
9
HCl
H2SO4
TiCl4
SiCl4
AlCl3
SnCl4
p-TSA
Bi(OTf)3
BiCl3
FeCl3
10
10
10
10
10
10
10
10
10
10
10
5
11
9
45
52
50
60
69
55
40
62
20
65
52
87
24
24
15
24
17
8
24
15
15
5
10
11
12
Amberlyst-15
Phosphomolybdic acid
aReaction conditions: ArCOMe (5 mmol), HPA (0.1 mmol), ethanol (4 ml),
reflux.
bIsolated yield.

1,3,5-Triarylbenzenes from Acetophenones
4119
Table 2. Cyclotrimerization of different acetophenones into 1,3,5-triarylbenzenes
using phosphomolybdic acid as a solid acid catalysta
Entry
Ar
Time (h)
Yield (%)b
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
Ph
5
7
6.5
6.2
6
7
8
6
4
5.5
9
8
4.2
4.6
12
87
68
70
72
75
78
73
88
92
76
80
72
78
90
30
2-Me-C6H4
2-MeO-C6H4
3-Me-C6H4
3-MeO-C6H4
3-F-C6H4
3-Cl-C6H
4-Me-C6H4
4-Ph-C6H4
4-Cl-C6H4
4-F-C6H4
4-Br-C6H4
4-I-C6H4
4-MeO-C6H4
4-NO2-C6H4
aReaction conditions: ArCOMe (5 mmol), HPA (0.1 mmol), ethanol (4 ml),
reflux.
bIsolated yield.
cyclotrimerization of different acetophenones was carried out by
refluxing the acetophenone with 5 mol% HPA in ethanol at reflux
temperature to obtained product in good yield (Table 2).
CONCLUSION
In conclusion, phosphomolybdic acid as a HPA catalyst has proved to be
a useful, efficient, and recyclable catalyst for cyclotrimerization of aceto-
phenones. The present protocol has several advantages over reported
literature methods from economical and environmental points of view,
such as operational simplicity, short reaction time, mild reaction
condition, good yield of the product, and recyclability of catalyst.
EXPERIMENTAL
All commercial reagents were used as received without purification, and
all solvents were of reagent grade. The reaction was monitored by
thin-layer chromatography (TLC) using 0.25-mm Merck silica-gel

4120
K. Phatangare et al.
60 F254 precoated plates, which were visualized with ultraviolet (UV)
light. Melting points were observed using open capillaries. 1H NMR
and 13C NMR spectra were recorded on a VXR 300-MHz instrument,
using tetramethylsilane (TMS) as an internal standard.
General Procedure for Conversion of Acetophenone into
1,3,5-Triphenylbenzene
Acetophenone (5 mmol) and phosphomolybdic acid (0.1 mmol) were
added to ethanol (4 ml), and the reaction mixture was stirred for 5 h at
reflux temperature. After completion of reaction, as indicated by TLC,
the solvent was removed under pressure. The solid product was washed
with water and recrystallized using a mixture of ethanol and dichloro-
methane (1:1). The aqueous part was concentrated to isolate the
phosphomolybdic acid. Yield 87%, mp 172–174ꢁC.
Data
1H NMR (CDCl3): d 7.18 (3H, s); 7.72 (6H, m); 7.50 (6H, m); 7.42
(3H, m) ppm. 13CNMR (CDCl3): d 142, 141, 129, 127.5, 127.3,
125 ppm. MS (EI, 70 eV) 306 (Mþ), 289, 232, 154, 136.
ACKNOWLEDGMENTS
The authors are grateful to the University Grants Commission,
New Delhi, the University of Mumbai for financial support, and to
Dr. S. T. Gadade, principal, C. K. Thakur College, for providing labora-
tory and other facilities.
REFERENCES
1. Horgan, A. M. Composite layered photoreceptor. US patent 4081274, 1978;
Chem. Abstr. 1978, 89, 120873.
2. Lindeman, S. V.; Struchkov, Y. T.; Michailov, V. N.; Resanov, A. L. Synth-
esis and crystal structure of 1,3,5-tris[4-(phenylethynyl)phenyl]benzene. Izu.
Akad. Nauk. Ser. Khim 1994, 1986; Chem. Abstr. 1995, 123, 32717.
3. Aslam, M.; Aguilar, D. A. Trimerization process for preparing
1,3,5-tris(40-hydroxyphenyl)benzenes. WO patent 9314065, 1993; Chem.
Abstr. 1993, 119, 270793.
4. Ikadai, J.; Yoshida, H.; Obshita, J.; Kunai, A. Facile synthesis of polycyclic
aromatic hydrocarbons via a trisaryne equivalent. Chem. Lett. 2005, 34, 56.

1,3,5-Triarylbenzenes from Acetophenones
4121
5. (a) Pepin-Donat, B.; Geyer, A.; Viallat, A. Structural and transport
properties in solid-state conducting gels: Influence of the crosslink density.
Polymer 1998, 39, 6673; (b) Robourt, E.; Pepin-Donat, B.; Dinh, E. Routes
towards three-dimensional fully conjugated conducting polymers,
1: Preparation of the kit of monomers. Polymer 1995, 36, 399.
6. Lyle, R. E.; Dewitt, E. J.; Nichols, M. M.; Cleland, W. Acid catalysed
condensations, I: 1,3,5-triarylbenzenes. J. Am. Chem. Soc. 1953, 75, 5959.
7. Jing, X.; Xu, F.; Zhu, Q.; Ren, X.; Yan, C.; Wang, L.; Wang, J. Novel
method for the synthesis of 1,3,5-triarylbenzenes from ketones. Synth.
Commun. 2005, 35, 3167.
8. Plater, M. J.; Praveen, M. A new synthesis of truxenone. Tetrahedron Lett.
1997, 38, 1081.
9. Li, Z.; Sun, W. H.; Jin, X.; Shao, C. Triple self-condensation of ketones yield-
ing aromatics promoted with titanium tetrachloride. Synlett 2001, 1947.
10. Iranpoor, N.; Zeynizaded, B. TiCl3(OTf) catalyses the efficient conversion of
acetophenones to 1,3,5-triarylbenzenes. Synlett 1998, 1079.
11. Lorette, N. B. Ketone condensations using a sulfonic acid ion exchange resin.
J. Org. Chem. 1957, 22, 346.
12. Odell, A. F.; Hines, C. W. The pyrosulfates of sodium and potassium as
condensing agents. J. Am. Chem. Soc. 1913, 35, 82.
13. Elmorsy, S. S.; Pelter, A.; Smith, K. The direct production of tri- and
hexa-substituted benzenes from ketones under mild conditions. Tetrahedron
Lett. 1991, 32, 4175.
14. Plater, M. J.; McKay, M.; Jackson, T. Synthesis of 1,3,5-tris[4-
(diarylamino)phenyl]benzene and 1,3,5-tris(diarylamino)benzene derivatives.
J. Chem. Soc., Perkin Trans. 1 2000, 2695.
15. Elmorsy, S. S.; Pelter, A.; Smith, K.; Hursthouse, M. B.; Ando, D. Investiga-
tions of the tetrachlorosilane-ethanol-induced self-condensations of ketones.
Tetrahedron Lett. 1992, 33, 821.
16. Ono, F.; Ishikura, Y.; Tada, Y.; Endo, M.; Sato, T. Efficient conversion of
acetophenones into 1,3,5-triarylbenzenes catalyzed by bismuth(III) trifluoro-
methanesulfonate tetrahydrate. Synlett 2008, 2365.
17. Okuhara, T.; Mizuno, N.; Misono, M. Catalytic chemistry of heteropoly
compounds. Adv. Catal. 1996, 41, 113.
18. Drago, R. S.; Dias, J. A.; Maier, T. O. An acidity scale for Brønsted acids
including H3PW12O40. J. Am. Chem. Soc. 1997, 119, 7702.
19. Schwegler, M. A.; Van Bekkum, H.; De Munck, N. Heteropolyacids as
catalysts for the production of phthalate diesters. Appl. Catal. 1991, 74, 191.
20. Chaskar, A.; Yadav, A.; Langi, B.; Murugappan, A.; Bodkhe, A. Heteropoly
acids as heterogeneous catalysis for a-thiocyanation of ketones. Adv. Synth.
Catal. (Communicated).
21. Chaskar, A.; Padalkar, V.; Phatangare, K.; Patil, K.; Bodkhe, A.; Langi, B.
Heteropoly acids as a useful recyclable heterogeneous catalyst for the facile
and highly efficient aza-cope rearrangement of N-allylanilines. Appl. Catal.
A: General 2009, 359, 84.