Silica-supported heteropolyacids readily induce cyclodimerization of styrenes and stilbenes

Article abstract of DOI:10.1081/SCC-120015399

Heteropolyacids such as molybdophosphoric and tungstophosphoric acids, supported over silica, readily induce cyclodimerisation reactions of styrenes and stilbenes affording a mixture of indane and/or tetraline derivatives with remarkably high efficiency and in reduced reaction time.

Full text of DOI:10.1081/SCC-120015399

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SILICA-SUPPORTED HETEROPOLYACIDS READILY INDUCE
CYCLODIMERIZATION OF STYRENES AND STILBENES
Elba Alesso a , Rosario Torviso a , Magali Erlich a , Liliana Finkielsztein a , Beatriz Lantaño a
,
Graciela Moltrasio a , José Aguirre b , Patricia Vázquez c , Luis Pizzio c , Carmen Cáceres c
Mirta Blanco c & Horacio Thomas c
,
a Departamento de Química Orgánica , Facultad de Farmacia y Bioquímica , Universidad de
Buenos Aires , Buenos Aires, Argentina
b Departamento de Ciencias Básicas , Universidad Nacional de Luján , Luján, Argentina
c Centro de Investigación y Desarrollo en Procesos Catalíticos (CINDECA) La Plata , Pcia. de
Buenos Aires, Argentina
Published online: 23 Aug 2006.
To cite this article: Elba Alesso , Rosario Torviso , Magali Erlich , Liliana Finkielsztein , Beatriz Lantaño , Graciela Moltrasio ,
José Aguirre , Patricia Vázquez , Luis Pizzio , Carmen Cáceres , Mirta Blanco & Horacio Thomas (2002) SILICA-SUPPORTED
HETEROPOLYACIDS READILY INDUCE CYCLODIMERIZATION OF STYRENES AND STILBENES, Synthetic Communications:
An International Journal for Rapid Communication of Synthetic Organic Chemistry, 32:24, 3803-3812, DOI: 10.1081/
SCC-120015399
To link to this article: http://dx.doi.org/10.1081/SCC-120015399
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SYNTHETIC COMMUNICATIONS
Vol. 32, No. 24, pp. 3803–3812, 2002
SILICA-SUPPORTED
HETEROPOLYACIDS READILY INDUCE
CYCLODIMERIZATION OF STYRENES
AND STILBENES
Elba Alesso,1, Rosario Torviso,1 Magali Erlich,1
*
Liliana Finkielsztein,1 Beatriz Lantano,1
Graciela Moltrasio,1 Jose Aguirre,2 Patricia Vazquez,3
Luis Pizzio,3 Carmen Caceres,3 Mirta Blanco,3
and Horacio Thomas3
1Departamento de Quımica Organica, Facultad de
Farmacia y Bioquımica, Universidad de Buenos Aires,
Buenos Aires, Argentina
2Departamento de Ciencias Basicas, Universidad
Nacional de Lujan, Lujan, Argentina
3Centro de Investigacion y Desarrollo en Procesos
Catalıticos (CINDECA) La Plata,
Pcia. de Buenos Aires, Argentina
ABSTRACT
Heteropolyacids such as molybdophosphoric and tungsto-
phosphoric acids, supported over silica, readily induce cyclo-
dimerisation reactions of styrenes and stilbenes affording a
mixture of indane and/or tetraline derivatives with remark-
ably high efficiency and in reduced reaction time.
*Corresponding author. E-mail: enalesso@ffyb.uba.ar
3803
DOI: 10.1081/SCC-120015399
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3804
ALESSO ET AL.
Key Words: Heteropolyacid; Cyclodimerisation; Styrenes;
Stilbenes; Indanes; Tetralines; Molybdophosphoric acid;
Tungstophosphoric acid; Supported
INTRODUCTION
Use of supported reagents and catalysts for organic syntheses is of
current research interest, since reactions under solid-solution biphasic
conditions provide many practical advantages unavailable by conventional
solution-phase counterparts.
Among frequently employed support materials, heteropolyacids
supported over silica have enjoyed extensive use as solid acid catalysts.
This is primarily due to the advantages associated with the use of solid
acids such as easy work-up, eco-friendly nature, regeneration and reversi-
bility, and on occasion, their shape-selective nature.
Recently, we have reported the preparation of silica-supported
molybdophosphoric acid and tungstophosphoric acid catalysts (MPA/S
and TPA/S, respectively)[1] and shown that they behaved as useful reagents
for the dehydration of some secondary as well as tertiary alcohols.[2] In some
cases, it has been found that not only olefin products, but also their dime-
rization derivatives were obtained.
Acid-catalysed dimerization of styrenes and stilbenes involves organic
reactions of commercial significance and academic interest, as a rule carried
out using mineral or Lewis acids.
Pursuing our interest in reactions catalysed by MPA/S and TPA/S, we
investigated their use in the formation of cyclodimerization products of
stilbene and styrene derivatives and compared the results with those
obtained employing mineral or Lewis acids.
RESULTS AND DISCUSSION
Acid-catalysed dimerization of a-methyl styrene (1) (AMS) with acidic
ion exchange resins, clays and aqueous sulphuric acid affords a number of
products (2–4) (Fig. 1).[3] Treated with ethyl-alumininum dichloride under
several conditions in a benzene solution, AMS rendered the indane-type
dimer 4 and trimer 5.[4] (Fig. 1).
When AMS was treated with TPA/S or MPA/S in chloroform, it
afforded the dimer 4[4] with a quantitative yield in barely 15 min.
The results obtained by the reaction of AMS with several acid
catalysts including MPA/S and TPA/S in different conditions are shown
in Table 1.

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CYCLODIMERIZATION OF STYRENES AND STILBENES
3805
Figure 1.
Table 1. Reaction Products of AMS Using Different Catalysts
Temp. Reaction AMS Yield
(ꢀC)
Reagents
Time
(%)
2
3
4
5
Other
4.55
H2SO4/H2O/
MeOH
80
7 h
45
37.4 3.0 0.05
EtAlCl2
EtAlCl2
EtAlCl2
TPA/S
MPA/S
MPA/S
4
25
80
60
r.t.
60
5 min
5 min
80 min
90 min
30 h
92
80
86
Quant.
Quant.
Quant.
37
52
73
>99
>99
>99
55
28
13
2 h
Scheme 1.
The above findings prompted us to repeat the experiment using styrene
(6) as starting material. In chloroform at reflux, after 2 h the open dimer (7)[5]
was isolated together with the cis and trans 1-methyl-3-phenylindanes (8)[6]
and (9),[6] respectively, in a 1 : 4 : 1 ratio (Sch. 1). The reaction products were
fully characterised by physical and spectral data.
Tricyclic dimers, obtained from styrenes with acidic reagents, have
been known for over ninety years.[7] The phenylindane structure was first
established for the anethole dimer and subsequently for the isohomogenol

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3806
ALESSO ET AL.
Scheme 2.
dimer and that of isosafrol (10), diisosafrole. Four racemates of these
indanes are possible (a, b, g, and d) but only two (a and g) have been
obtained from propenylbenzenes with acid reagents.[7]
In the present work, we explored the behavior of isosafrol (10) with
two acid catalysts (TPA/S, MPA/S) and compared them with the ones
obtained using EPP[8] (ethylpolyposphate) and 50% H2SO4.[7] Two race-
mates were obtained with all the acid catalysts. The major (11) and minor
(12) products were respectively, concluded to have the 1,2-cis-2,3-trans-
configuration (a racemate) and 1,2-trans-2,3-trans-configuration (g race-
mate)[7,8] (Sch. 2). The conditions used and the results obtained are listed
in Table 2. Once again, TPA/S and MPA/S showed exceptional catalytic
activity for the formation of indanes from styrenes and the isolation of
products, which were identified by comparison of NMR spectra with
those in the literature, was straightforward.
We also examined the cyclodimerization reaction of several stilbenes
with TPA/S or MPA/S. When 4-bromo-30,40-dimethoxystilbene (13) was
treated with TPA/S or MPA/S, a mixture of diasteroisomeric indanes was
obtained, namely 14 (g configuration) and 15 (a configuration)[9] (Sch. 3).
These results were compared with those obtained with EPP[9] and with 50%
[9]
H2SO4 and given in Table 2. Data show a higher efficiency of reactions
carried out with TPA/S or MPA/S in comparison to those performed with
EPP or 50% H2SO4.
Treatment of 3,4,30,40-tetramethoxystilbene 16 with EPP[9] or 50%
H2SO4 rendered only the tetraline 17[9] with all trans-configuration, but
[9]
with TPA/S or MPA/S stilbene 16 afforded a mixture of tetraline 17 with
a new compound 18 (Sch. 4). The choice between tetralinic and indanic
structure was made on the basis of the following data: (a) in the mass spectra
of 1-benzylindanes the base peak was originated from the loss of the benzyl
group, whereas in the case of tetralines, it derives from a retro Diels-Alder
type clevage[9]; (b) comparing chemical shift data of the carbon atoms of the
four racemic diasteroisomers of 1-benzyl-2,3-diphenylindane and also
of 1,2,3-triaryltetralines[9]; and (c) based on the values of the general coup-

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CYCLODIMERIZATION OF STYRENES AND STILBENES
3807

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3808
ALESSO ET AL.
Scheme 3.
Scheme 4.
Scheme 5.
ling constants of the benzyl methylene hydrogen atoms. The value is in
the order of 13 Hz for the exocyclic benzyl groups and of 16 Hz for the
endocyclic benzyl groups.[9] Table 2 summarizes these results.
When 3,4,40-trimethoxystilbene 19 was treated with TPA/S or MPA/S,
a mixture of tetraline 20 and indane 21 was obtained (Sch. 5).
Treatment of 19 with several acids in comparison to results
obtained with TPA/S or MPA/S are shown in Table 2. A complex mixture
of regio- and stereo-isomers was obtained by treatment of 19 with EPP or
50% H2SO4. The separation of this mixture proved impracticable.[9]
Lastly, when 4,40-dimethoxystilbene 22 was treated with TPA/S
or MPA/S, tetraline 23[10] was obtained with 99% yield (Sch. 6). All
efforts to achieve cyclodimerization products by treatment of 22
with EPP or 50% H2SO4 rendered only starting material.[9] This tetra-
line was obtained by other authors in reactions carried out in

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CYCLODIMERIZATION OF STYRENES AND STILBENES
3809
Scheme 6.
1,1,1,3,3,3-hexafluoropropan-2-ol, and in dichloromethane solutions
with catalytic amounts of tris-(2,4-dibromophenyl)aminium hexachloro
antimonate.[10]
In conclusion, the present new method for the preparation of indanes
and/or tetralines offers significant improvements over existing procedures
and provides a useful contribution to available methods. The main
advantages are mild reaction conditions, reduced reaction time, lack of
side-products, and excellent yields.
EXPERIMENTAL
1H and 13CNMR spectra were recorded with a Bruker AC-300 spectro-
meter with CDCl3 as solvent, employing Me4Si as internal standard (ꢀ: 0.00)
J values are given in Hz. Mass spectra were obtained by direct injection of
the sample as chloroform solution by using Shimadzu GCQP 1000 mass
spectrometer operating at an ionizing electron energy of 70 eV. Elemental
analysis was carried out in our laboratories with a Colleman Analyser.
Melting point (uncorrected) was obtained with a Thomas Hoover apparatus.
Preparative thin layer chromatography ( p-tlc) was performed on a
20 Â 20 cm glass plate coated with silica gel 60 F254 (0.50 mm).
General Procedure
Styrenes or stilbenes were mixed with the catalyst (0.1 meq of
catalyst/meq. of reactive) in chloroform. The resulting mixture was heated
at reflux temperature and the reaction was followed using thin layer
chromatography. After completion of the reaction, the catalyst was
removed by filtration, washed with chloroform and dried to be reused in
other reactions.[1] The solvent was evaporated under reduced pressure and
the residue was purified either by recrystallization or via p-tlc.

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3810
ALESSO ET AL.
Dimerization reaction of styrene 1: Oil (lit[11] 52ꢀC). Spectroscopy data
were coincident with those which appeared in the literature.[12]
Dimerization reaction of styrene 6: Reaction time: 2 h. The residue was
purified by p-tlc and developed with hexane. The upper band yielded a mix-
ture of cis and trans 1-metyl-3-phenylindane (8 and 9)[5] (8 : 9 ¼ 14 : 1). Yield: 47%.
The lower band yielded 1,3-diphenylbutene (7). Yield: 33%. 1H NMR
spectra of 7 correlated to the one which is shown in literature.[5] 13CNMR ꢀ
21.2 (CH3), 42.5 (CH), 126.1 (CH¼), 126.2 (CH¼), 127.0, 127.3, 128.4, 135.2,
137.5, 145.6. m/z: 208 (29, Mþ), 193 (30), 167 (28), 118 (91), 105 (100), 77 (86).
Dimerization reaction of styrene 10: Reaction time: 2 h. The residue
afforded a mixture of r-1-ethyl-c-2-methyl-t-3-(3,4-methylenedioxyphenyl)-
5,6-methylendioxyindane (11) and r-1-ethyl-t-2-methyl-c-3-(3,4-methylene-
dioxyphenyl)-5,6-methylendioxyindane (12). Yield 99.4%. Isomeric
relation: 11 : 12 ¼ 3 : 1. The mixture was separated by fractional crystalliza-
tion from ethanol and the spectroscopy data were coincident with those
which appeared in the literature.[7]
Dimerization reaction of stilbene 13: Reaction time: 2 h. The residue
a
afforded
mixture of r-1-(4-bromobenzyl)-t-2-(4-bromophenyl)-c-3-
(3,4-dimethoxyphenyl)-5,6-dimethoxyindane (14) and r-1-(4-bromobenzyl)-
c-2-(4-bromophenyl)-t-3-(3,4-dimethoxyphenyl)-5,6-dimethoxyindane (15).
Yield: 98%. Isomeric relation: 14 : 15 ¼ 3 : 2. The mixture was separated
by fractional crystallization from ethanol and the spectroscopy data were
coincident with those which appeared in the literature.[9]
Dimerization of 3,4,30,40-tetramethoxystilbene (16): Reaction time: 2 h.
The residue was purified by p-tlc using hexane : ethyl acetate (5 : 3) as
eluent to give r-1-(3,4-dimethoxyphenyl)-t-2,c-3-bis-(3,4-dimethoxyphenyl)-
6,7-dimethoxytetralin (17)[9] (lower band) and r-1-(3,4-dimethoxybenzyl)-
t-2-(3,4-dimethoxyphenyl)-c-3-(3,4-dimethoxyphenyl)-5,6-dimethoxyindane
(18) (upper band). Yield: 90% of cyclodimers.
r-1-(3,4-Dimethoxybenzyl)-t-2-(3,4-dimethoxyphenyl)-c-3-(3,4-dimethoxy-
phenyl)-5,6-dimethoxyindane (18): Oil. Yield: 43%. 1H NMR ꢀ 2.86 (dd, J 14,
J 8, 1H, CH2Ar), 2.96 (br t, 1H, H-2), 3.09 (dd, J 5, J 14, 1H, CH2Ar), 3.68,
3.72, 3.74, 3.76, 3.78, 3.83, 3.84, 3.85 (s, 24H, OCH3), 3.85 (m, 1H, H-1), 4.16
(d, J 9, 1H, H-3), 6.40 (d, J 1.9, 1H, Ar), 6.45 (s, 1H, Ar), 6.50 (dd, J 1.9, J 8,
1H, Ar), 6.57 (d, J 1.9, 1H, Ar), 6.63 (m, 3H, Ar), 6.72 (m, 4H, Ar). 13CNMR
ꢀ 39.4 (CH2), 51.7 (C-1), 55.6 (OCH3), 55.7 (OCH3), 55.8 (OCH3), 56.0
(OCH3), 59.1 (C-3), 63.0 (C-2), 107.0, 107.8, 110.7, 110.8, 110.9, 111.0,
112.5, 120.0, 120.5, 121.5, 132.5, 135.2, 136.4, 136.7, 137.2, 147.2, 147.4,
148.3, 148.5. m/z: 600 (15, Mþ), 449 (100, Mþ ꢁ 3,4-di-CH3OPhCH2).
Calcd. for C36H40O8: C, 71.98; H, 6.71. Found: C, 71.62; H, 6.80.
Dimerization of 3,4,40-trimethoxystilbene (19): Reaction time: 2 h.
The residue was purified by p-tlc using hexane : ethyl acetate (3 : 1) as

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CYCLODIMERIZATION OF STYRENES AND STILBENES
3811
eluent to give the r-1-(3,4-dimethoxyphenyl)-t-2-c-3-bis-(4-methoxyphenyl)-
6,7-dimethoxytetralin (20) (upper band) and the r-1-(4-methoxybenzyl)-
t-2-(4-methoxyphenyl)-c-3-(3,4-dimethoxyphenyl)-5,6-dimethoxyindane (21)
(lower band).
r-1-(3,4-Dimethoxyphenyl)-t-2,c-3-bis-(4-methoxyphenyl)-6,7-dimethoxy-
tetralin (20): Oil. Yield: 44%. 1H NMR ꢀ 3.00–3.50 (m, 4H, H-2, H-3, CH2),
3.62, 3.63, 3.71, 3.74, 3.82, 3.85 (s, 18H, OCH3), 4.10 (d, J 10.1, 1H, H-1), 6.19
(s, 1H, Ar), 6.30 (m, 2H, Ar), 6.50–6.80 (m, 8H, Ar), 6.95 (d, J 8.7, 2H, Ar).
13CNMR ꢀ 39.5 (CH2), 45.3 (C-3), 53.5 (C-1), 54.2 (OCH3), 54.4 (OCH3),
54.6 (OCH3), 55.1 (C-2), 110.5, 110.6, 112.5, 112.6, 113.0, 113.4, 120.3, 128.5,
129.3, 130.5, 131.6, 134.2, 136.7, 138.0, 146.9, 147.2, 148.1, 157.2, 157.4. m/z:
540 (25, Mþ), 419 (13.6), 389 (7.5), 269 (100, Mþ/2). Calcd. for C34H36O6:
C, 75.53; H, 6.71. Found: C, 75.62; H, 6.85.
r-1-(4-Methoxybenzyl)-t-2-(4-methoxyphenyl)-c-3-(3,4-dimethoxyphe-
nyl)-5,6-dimethoxyindane (21): Oil, Yield: 33%. 1H NMR ꢀ 2.85 (dd, J 14, J
8 Hz, 1H, CH2Ar), 2.96 (br t, 1H, H-2), 3.04 (dd, J 4.5, J 14, CH2Ar), 3.74,
3.77, 3.79, 3.82, 3.83, 3.86 (s, 18H, OCH3), 3.85 (m, 1H, H-1), 4.19 (d, J 9.3,
1H, H-3), 6.42 (s, 1H, Ar), 6.50 (s, 1H, Ar), 6.54 (s, 1H, Ar), 6.76 (m, 3H,
Ar), 6.82 (d, J 8.5, 1H, Ar), 6.90 (d, J 8.5, 2H, Ar), 6.99 (d, J 8.5, 2H, Ar),
7.05 (d, J 8.5, 2H, Ar). 13CNMR ꢀ 38.7 (CH2), 51.2 (C-1), 53.7 (OCH3), 54.5
(OCH3), 54.7 (OCH3), 57.9 (C-3), 62,9 (C-2), 107.1, 107.7, 112.1, 112.5,
112.8, 118.9, 119.3, 127.3, 128.2, 128.3, 128.7, 129.3, 131.1, 134.4, 138.2,
138.9, 139.0, 147.3, 148.1, 148.4, 156.9, 157.0. m/z: 540 (12.3, Mþ), 419
(100, Mþ ꢁ 4CH3OPhCH2). Calcd. for C34H36O6: C, 75.58; H, 6.71.
Found: C, 75.82; H, 6.78.
Dimerization fo 4,40-dimethoxystilbene (22): Reaction time: 12 h. The
crude product afforded r-1,t-2,c-3-tris(4-methoxyphenyl)-7-methoxytetralin
1
(23) as an oil. Yield: 99%. H NMR ꢀ 3.10 (dd, J 4.1, J 16, 1H, H-4),
3.13–3.28 (m, 2H, H-4, H-2), 3.37 (td, J 4.1, J 10.5, H-3), 3.72, 3.75, 3.81,
3.88 (s, 12H, OCH3), 4.19 (d, J 10.3, 1H, H-1), 6.27 (d, J 2.6, 1H, H-8), 6.53
(d, J 8.7, 2H, Ar), 6.51–6.77 (m, 9H, Ar), 6.98 (d, J 8.7, 2H, Ar), 7.03
(d, J 8.7, 1H, Ar). 13CNMR ꢀ 39.0 (CH2), 45.4 (C-3), 53.4 (OCH3),
53.6 (OCH3), 53.7 (OCH3), 54.4 (C-1), 55.0 (C-2), 111.8, 112.2,
112.4, 112.5, 113.0, 113.3, 126.4, 127.4, 127.9, 128.0, 128.2, 129.2, 134.1,
135.6, 136.6, 140.1, 156.4, 156.6, 156.8, 156.9. m/z: 480 (17.2, Mþ), 359
(18.3, Mþ ꢁ 4CH3OPhCH2), 240 (100, Mþ/2).
ACKNOWLEDGMENT
This work was financially supported by Grants 14-00059-01104
ANPCyT, X224 UNLP, TB50 UBA and CONICET.

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ALESSO ET AL.
REFERENCES
1. Vazquez, P.; Pizzio, L.; Caceres, C.; Blanco, M.; Thomas, H.; Alesso, E.;
Finkielsztein, L.; Lantano, B.; Moltrasio, G.; Aguirre, J. J. Mol. Catal.
A: Chemical 2000, 161, 223.
2. Alesso, E.; Torviso, R.; Finkielsztein, L.; Lantano, B.; Moltrasio, G.;
Aguirre, J.; Vazquez, P.; Pizzio, L.; Caceres, C.; Blanco, M.; Thomas, H.
J. Chem. Research, 2001, 1232.
3. Chaudhuri, B. Org. Proc. Res. Develop. 1999, 3(3), 220.
4. Wolovsky, R.; Maoz, N. J. Org. Chem. 1973, 38, 4040.
5. Mayo, F.R. J. Am. Chem. Soc. 1968, 90, 1289.
6. Xu, T.; Haw, J.F. J. Am. Chem. Soc. 1994, 116, 10188.
7. MacMillan, J.; Martin, I.L.; Morris, D.L. Tetrahedron 1969, 25, 905
and references therein.
8. Alesso, E.N.; Mufato, J.D.; Aguirre, J.M.; Moltrasio Iglesias, G.Y.
Aust. J. Chem. 1992, 45, 1753.
9. Alesso, E.N.; Aguirre, J.M.; Moltrasio Iglesias, G.Y. J. Chem. Soc.,
Perkin Trans. 1 1999, 1353.
10. Ciminale, F.; Lopez, L.; Farinola, G. Tetrahedron Lett. 1999, 40, 7267.
11. Adams, L.M.; Lee, R.J.; Wadsworth, F.T. J. Org. Chem. 1959, 24,
1186.
12. Benkeser, R.A.; Hooz, J.; Liston, T.V.; Tressilyan, E.A. J. Am. Chem.
Soc. 1963, 85, 3984.
Received in the USA December 7, 2001