Syntheses of p-terphenyls and 11,12-dihydroindeno[2,1-a]fluorene by one-pot benzannulation of Diels-Alder reactions of trans-1,2-dichloroethene and dienes

Article abstract of DOI:10.1016/j.tetlet.2013.02.002

A series of substituted p-terphenyls and 11,12-dihydroindeno[2,1-a]fluorene were successfully synthesized by one-pot benzannulation of Diels-Alder reaction with 1,2-dichloroethene as an acetylene equivalent dienophile. Two chlorine atoms could be good leaving groups to easily undergo subsequent elimination reactions of Diels-Alder products at a high temperature.

Full text of DOI:10.1016/j.tetlet.2013.02.002

Tetrahedron Letters 54 (2013) 1991–1993
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Tetrahedron Letters
journal homepage: www.elsevier.com/locate/tetlet
Syntheses of p-terphenyls and 11,12-dihydroindeno[2,1-a]fluorene by one-pot
benzannulation of Diels–Alder reactions of trans-1,2-dichloroethene and dienes
⇑
Jinn-Hsuan Ho , Yu-Chen Lin, Li-Ting Chou, Ying-Zhe Chen, Wei-Qi Liu, Chao-Li Chuang
Department of Chemical Engineering, National Taiwan University of Science and Technology, No. 43, Sec. 4, Keelung Road, Taipei 106, Taiwan
a r t i c l e i n f o
a b s t r a c t
Article history:
A series of substituted p-terphenyls and 11,12-dihydroindeno[2,1-a]fluorene were successfully synthe-
sized by one-pot benzannulation of Diels–Alder reaction with 1,2-dichloroethene as an acetylene equiv-
alent dienophile. Two chlorine atoms could be good leaving groups to easily undergo subsequent
elimination reactions of Diels–Alder products at a high temperature.
Received 23 September 2012
Revised 27 December 2012
Accepted 1 February 2013
Available online 8 February 2013
Ó 2013 Elsevier Ltd. All rights reserved.
Keywords:
One-pot benzannulation
Diels–Alder reaction
1,2-Dichloroethene
p-Terphenyls
Indenofluorene
H
Diels–Alder reaction is a traditional way to construct a six-
member ring by [4+2] annulations. But for achieving benzannula-
tion, an additional dehydrogenation step is usually applied after
Diels–Alder reaction.1 In order to carry out one-step benzannula-
tion of [4+2] cycloaddition, some modified synthetic methods have
been developed, such as cyclization of alkynes with enynes,2 ney-
nals,3 dienes containing fragmental parts4 or polycyclic aromatics5,
and cyclization of cyclopentadienone and phenylacetylenes under
sulfuric acid.6 Although these cases showed the convenience to
construct benzene rings in one-pot, they would produce specific
substituents unavoidably to limit their uses.
One way to establish simple benzene without extra substitu-
ents from dienophiles is to use an acetylene equivalent dienophile
in Diels–Alder reaction and other cycloadditions. These dieno-
philes, including phenyl vinyl sulfoxide7 and bis-sulfonyl ethyl-
ene,8 can construct simple benzene ring directly, but they are
relatively expansive and sometimes not easily acquired. And the
sulfonyl group is not a good leaving group for elimination reaction.
In the case of bis-sulfonyl ethylene, even sodium amalgam was
needed to eliminate sulfonyl groups.
Cl
Cl
Cl
+
-2HCl
Cl
H
Scheme 1. Concept of one-pot benzannulation of Diels–Alder reaction.
Elimination
- 2 HCl
DMF/ reflux
Diels-Alder
Cl
Cl
Cl
+
In sealed tube
~200 o
C
Cl
R
R
3a-3g
R
1a-1g
for 2c and 2e
> 240 oC in sealed tube
or ~200 oC, triethylamine added in sealed tube
To advance one-pot benzannulation of Diels–Alder reaction, we
planned to use trans-1,2-dichloroethene as the acetylene
equivalent dienophile, because the two chlorine atoms could be
good leaving groups to easily undergo subsequent elimination
reactions of Diels–Alder products (Scheme 1). In our preliminary
study, heating a mixture of 1,4-diphenyl-1,3-butadiene 1c and
R = OCH3 (a), CH3 (b), H (c), F (d), Cl (e), Br (f), CN (g)
Scheme 2. One-pot benzannulation of Diels–Alder reaction.
trans-1,2-dichloroethene in a high-pressure sealed glass tube at
about 250 °C afforded p-terphenyl 3c directly. This successful re-
sult provided a convenient way to synthesize p-terphenyls which
is still an interesting structure for organic materials.9 Compared
⇑
Corresponding author. Tel.: +886 2 2737 6642; fax: +886 2 2737 6644.
E-mail address: jhho@mail.ntust.edu.tw (J.-H. Ho).
0040-4039/$ - see front matter Ó 2013 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.tetlet.2013.02.002

1992
J.-H. Ho et al. / Tetrahedron Letters 54 (2013) 1991–1993
with other synthetic methods of p-terphenyls,10 this approach
would provide some benefits, such as one-pot, solvent-free, and
metal-free reaction. Herein, we would like to report this one-pot
syntheses of p-terphenyls.
A series of starting butadienes, 1-aryl-4-phenyl-1,3-butadienes
1a, 1b, and 1d–1g, were synthesized by the Wittig reactions of
3-phenylpropenal and the corresponding (4-substitutedbenzyl)-
triphenylphosphonium halides (see Supplementary data). Heating
compounds 1a–1g and trans-1,2-dichloroethene in a high-pressure
sealed glass tube above 240 °C for 24 h afforded a series of
p-terphenyls (Scheme 2) and the reaction yields are listed in
Table 1.
Cl
+
Cl
Cl
Cl
-HCl
high T
-
Cl
high T
Cl
+Cl
OMe
1a
OMe
OMe
OMe
unstable intermediate
2a
-HCl
3a
at high temperature
When the Diels–Alder reaction of 1c and trans-1,2-dichloroeth-
ene was carried out below 240 °C, the result is quite different.
There was no reaction happening between 1c and trans-1,2-dichlo-
roethene when the reaction temperature was below 180 °C. That
may be because chloro substituent is not a strong electron-with-
drawing group. When the reaction temperature was at around
200 °C, a common Diels–Alder product 2c, 4,5-dichloro-3,6-diphe-
nylcyclohexene, was obtained after 24-h reaction. During the range
of 200–240 °C, a mixture of 2c and 3c was obtained (Scheme 2).
The benzannulation product 3c was obtained at above 240 °C be-
cause subsequently twice eliminations of hydrochloride of com-
pound 2c could occur under this high temperature. Beside the
high temperature (>240 °C), there are still two methods able to
transform 2c into 3c, one is to react 2c in a general refluxing
DMF solution for 20 h and the other is to heat a mixture of 1c,
trans-1,2-dichloroethene, and triethylamine at around 200 °C in a
high-pressure sealed glass tube.11
In order to figure out the reason for the low yield of 3a (Table 1,
entry 1), the reaction of 1a and trans-1,2-dichloroethene at around
210 °C in a high-pressure sealed glass tube was done but few of 2a
could be obtained. Increasing the reaction temperature could only
enhance the formation of 3a. However, another comparative
experiment, the reaction of 1e and trans-1,2-dichloroethene at
210 °C, could apparently afford compound 2e.12 This meant the
methoxy group, an electron-donating group, made 1a an unfavor-
able diene in this Diels–Alder reaction and it also made the reac-
tion occur at a high temperature. This high temperature may not
only drive hydrochloride eliminated directly but also cause some
intermediates of 1a, only formed by the influence of methoxy
group, reacted to unwanted side products, so this may be the rea-
son for the low yield of 3a (Scheme 3). Compared with 1a, com-
pound 1g containing a cyano group, an electron-withdrawing
group, underwent this Diels–Alder reaction to afford 3g in a better
yield (Table 1, entry 7). Therefore, the yields of 3a–3g are roughly
affected by the substitution effect.
Scheme 3. A possibility of the low yields of 3a.
The synthetic method in ref. 14b
CO2Me
(A), (B)
CO2Me
CO2Me
(C)
+
CO2Me
(2,1-a)-IF
(A) Diels-Alder reaction (85%), (B) Dehydrogenation (91%)
(C) Reduction and Friedel-Craft reaction (24% for two steps)
The synthetic method in this work
230 oC
Cl
oil-bath
+
In sealed
glass tube
(41%)
Cl
(1,2-b)-IF
(2,1-a)-IF
2,2'-biindene
Scheme 4. Synthetic methods for (2,1-a)-IF.
Because of the successful syntheses of p-terphenyls by this one-
pot benzannulation of Diels–Alder reaction, it occurred to us that it
might be a good synthetic method for 11,12-dihydroindeno[2,1-
a]fluorene (2,1-a)-IF, an isomer of 6,12-dihydroindeno[1,2-b]fluo-
rene (1,2-b)-IF (Scheme 4) which has been used as a core structure
in many cases of optoelectronic materials.13 Compound (2,1-a)-IF
was not studied as much as (1,2-b)-IF because of its synthetic dif-
ficulty. A series of derivatives of (2,1-a)-IF were recently synthe-
sized by Poriel’s group,14 and one of the synthetic pathways of
(2,1-a)-IF they proposed was a four-step synthesis with a total
yield of 18%.14b However, the synthesis of (2,1-a)-IF by our
approach only need one-step reaction from 2,20-biindene, which
was synthesized by a palladium-catalyzed coupling reaction of
tributyl(inden-2-yl)-stannane and 2-bromoindene,15 and the yield
of (2,1-a)-IF was about 41%.
Unlike trans-1,2-dichloroethene, cis-1,2-dichloroethene is not a
good acetylene equivalent dienophile for this Diels–Alder reaction.
Heating of 1c and cis-1,2-dichloroethene in a high-pressure sealed
glass tube above 240 °C for 24 h caused a complicated result and
p-terphenyl 3c was only obtained in
a
8% yield after
chromatography.
It is worthy to mention that the simple workup procedure also
makes this reaction more practical. In the cases of compounds
3b–3e, the products with enough purity for organic synthesis were
obtained only by adding a large amount of hexane into the cooled
reaction mixture and then filtrating the gray precipitated solids.
In summary, a series of p-terphenyls 3a–3g and 11,12-dihydro-
indeno[2,1-a]fluorene (2,1-a)-IF have been conveniently synthe-
sized by a one-pot benzannulation of Diels–Alder reaction with
1,2-dichloroethene as a dienophile. A further study of this direct
benzannulation of Diels–Alder reaction between a variety of dienes
and dienophiles containing appropriate leaving groups is in
progress.
Table 1
Results of syntheses of p-terphenyls 3a–3g
Entry
Diene
R
p-Terphenyl
Yielda
1
2
3
4
5
6
7
1a
1b
1c
1d
1e
1f
OCH3
CH3
H
F
Cl
3a
3b
3c
3d
3e
3f
24
50
75
33
65
Br
CN
52b
68
1g
3g
a
Isolated yields.
A mixture of 3e and 3f (ratio = 1:2.2).
b

J.-H. Ho et al. / Tetrahedron Letters 54 (2013) 1991–1993
1993
5. Fort, E. H.; Donovan, P. M.; Scott, L. T. J. Am. Chem. Soc. 2009, 131, 16006–16007.
6. (a) Ogliaruso, M. A.; Romanelli, M. G.; Becker, E. I. Chem. Rev. 1965, 6, 261–367;
(b) Pearson, A. J.; Kim, J. B. Tetrahedron Lett. 2003, 44, 8525–8527; (c) Yang, J.-S.;
Huang, H.-H.; Lin, S.-H. J. Org. Chem. 2009, 74, 3974–3977.
7. (a) Paquette, L. A.; Moerck, R. E.; Harirchian, B.; Magnus, P. D. J. Am. Chem. Soc.
1978, 100, 1597–1599; (b) Mullen, G. B.; Georgiev, V. St. J. Org. Chem. 1989, 54,
2476–2478.
Acknowledgments
We are grateful to the National Science Council of the Republic
of China (Taiwan) for financial support.
8. López-Pérez, A.; Adrio, J.; Carretero, J. C. J. Am. Chem. Soc. 2008, 130, 10084–
10085.
Supplementary data
9. (a) Meng, W.; Clegg, J. K.; Thoburn, J. D.; Nitschke, J. R. J. Am. Chem. Soc. 2011,
133, 13652–13660; (b) Modjewski, M.; Lindeman, S. V.; Rathore, R. Org. Lett.
2009, 11, 4656–4659; (c) Maya, F.; Tour, J. M. Tetrahedron 2004, 60, 81–92.
10. Adrioa, L. A.; Míguezb, J. M. A.; Hii, K. K. M. Org. Prep. Proced. Int. 2009, 41, 331–
358.
Supplementary data associated with this article can be found, in
the online version, at http://dx.doi.org/10.1016/j.tetlet.2013.02.
002.
11. Two comparative experiments were done to see the effect of triethylamine in
this one-pot benzannulation of Diels–Alder reaction under 200 °C at the same
time. The result of the reaction of 1c and trans-dichloroethene is to produce 2c
as a major product but that of the reaction of 1c, trans-dichloroethene, and
triethylamine is only to produce 3c.
References and notes
1. (a) Kotha, S.; Misra, S.; Halder, S. Tetrahedron 2008, 64, 10775–10790; (b)
Wessig, P.; Müller, G. Chem. Rev. 2008, 108, 2051–2063.
12. The formation of 2e could be seen in accordance with 1H NMR spectrum of the
crude sample and most major peaks of 1H NMR can be assigned to 2e and 3e.
13. (a) Sonar, P.; Zhang, J.; Grimsdale, A. C.; Müllen, K.; Surin, M.; Lazzaroni, R.;
Leclère, P.; Tierney, S.; Heeney, M.; McCulloch, I. Macromolecules 2004, 37, 709–
715; (b) Tsai, T.-C.; Hung, W.-Y.; Chi, L.-C.; Wong, K.-T.; Hsieh, C.-C.; Chou, P.-T.
Org. Electron. 2009, 10, 158–162; (c) Cocherel, N.; Poriel, C.; Vignau, L.;
Bergamini, J.-F.; Rault-Berthelot, J. Org. Lett. 2010, 12, 452–455.
14. (a) Poriel, C.; Rault-Berthelot, J.; Barrière, F.; Slawin, A. M. Z. Org. Lett. 2008, 10,
373–376; (b) Thirion, D.; Poriel, C.; Rault-Berthelot, J.; Barrière, F.; Jeannin, O.
Chem. Eur. J. 2010, 16, 13646–13658.
2. (a) Gevorgyan, V.; Quan, L. G.; Yamamoto, Y. J. Org. Chem. 1998, 63, 1244–1247;
(b) Gevorgyan, V.; Quan, L. G.; Yamamoto, Y. J. Org. Chem. 2000, 65, 568–572;
(c) Rubina, M.; Conley, M.; Gevorgyan, V. J. Am. Chem. Soc. 2006, 128, 5818–
5827.
3. (a) Asao, N.; Takahashi, K.; Lee, S.; Kasahara, T.; Yamamoto, Y. J. Am. Chem. Soc.
2002, 124, 12650–12651; (b) Asao, N.; Aikawa, H.; Yamamoto, Y. J. Am. Chem.
Soc. 2004, 126, 7458–7459; (c) Asao, N.; Aikawa, H. J. Org. Chem. 2006, 71,
5249–5253.
4. (a) Delaney, P. M.; Moore, J. E.; Harrity, J. P. A. Chem. Commun. 2006, 3323–
3325; (b) Dai, M.; Sarlah, D.; Yu, M.; Danishefsky, S. J.; Jones, G. O.; Houk, K. N. J.
Am. Chem. Soc. 2007, 129, 649–657; (c) Auvinet, A.-L.; Harrity, J. P. A. Angew.
Chem., Int. Ed. 2011, 5, 2769–2772.
15. Hudkins, R. L.; Johnson, N. W.; Angeles, T. S.; Gessner, G. W.; Mallamo, J. P. J.
Med. Chem. 2007, 50, 433–441.