Reusable resin Amberlyst 15 catalyzed new convenient protocol for accessing arylated benzene scaffolds

Article abstract of DOI:10.1016/j.tetlet.2009.05.029

Polyarylated benzene derivatives are useful molecular entities in chemical and material sciences owing to their unique photophysical properties associated with them. In this Letter, we report that 2-acetyl-benzofuran in the presence of Amberlyst 15 at reflux temperature furnished a mixture of dimer, trimer, and tetramer with interesting conformational properties. The protocol was generalized to prepare diverse arylated benzene scaffolds in good yields under similar reaction conditions.

Full text of DOI:10.1016/j.tetlet.2009.05.029

Tetrahedron Letters 50 (2009) 4335–4339
Contents lists available at ScienceDirect
Tetrahedron Letters
journal homepage: www.elsevier.com/locate/tetlet
Reusable resin Amberlyst 15 catalyzed new convenient protocol for accessing
q
arylated benzene scaffolds
a
a
a
b
b
a,*
Amit Kumar , Manish Dixit , Salil P. Singh , Resmi Raghunandan , Prakas R. Maulik , Atul Goel
a
Division of Medicinal and Process Chemistry, Central Drug Research Institute, Lucknow 226 001, India
Division of Molecular and Structural Biology, Central Drug Research Institute, Lucknow 226 001, India
b
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 23 February 2009
Revised 3 May 2009
Accepted 12 May 2009
Available online 18 May 2009
Polyarylated benzene derivatives are useful molecular entities in chemical and material sciences owing to
their unique photophysical properties associated with them. In this Letter, we report that 2-acetyl-ben-
zofuran in the presence of Amberlyst 15 at reflux temperature furnished a mixture of dimer, trimer, and
tetramer with interesting conformational properties. The protocol was generalized to prepare diverse
arylated benzene scaffolds in good yields under similar reaction conditions.
Ó 2009 Elsevier Ltd. All rights reserved.
Keywords:
Amberlyst 15
Aryl methyl ketone cyclotrimerization
2
-Acetylbenzofuran polymerization
X-ray analysis
1
2
Polyarylated benzene propellers have attracted a great deal of
of acid catalysts such as hydrochloric acid, sodium or potassium
1
3
14
enthusiasm toward leading edge carbon nanotechnology for devel-
oping new efficient molecular rotors and new electroluminescent
pyrosulfate in H
2
SO
4
,
aniline hydrochloride, titanium tetrachlo-
1
5
16
17
18
19
4
ride (TiCl ), SiCl
4
,
3
SmCl ,
CuCl
2
,
and Cp
2
ZrCl
2
and metal
1
20
materials for flat-panel displays. Owing to their unique chemical,
oxides of Al, Ti, Cr, and Mn at elevated temperature have been
employed to prepare arylated benzenes in moderate to good yields.
Recently an interesting article reported the use of cation rhodium
photophysical, and optical properties, these aromatic scaffolds are
1
21
not only useful as building blocks for material and biological sci-
2
*
6
ences, but also important for understanding the concept of aroma-
6 6 4 2
complex [Cp Rh(g -C H )](BF ) in under neutral conditions as
ticity, chemical reactivity, and reaction kinetics.3 Recently
catalyst for the conversion of cyclic ketones to polysubstituted
benzenes. Other common approaches for the preparation of poly-
aromatic compounds include cyclotrimerization of alkynes in the
presence of organometallic reagents, palladium- and nickel-cata-
lyzed multifold sequential Suzuki–Miyaura reaction between oli-
gohaloarenes with organometallic partners. However, except
few, most of these procedures are often complicated by harsh reac-
tion conditions, the lack of regioselectivity, formation of undesir-
polyaromatic hydrocarbons such as
p
-conjugated polyaromatics,
4
dendrimers and their derivatives find several applications in li-
5
6
7
22
quid crystals, laser dyes, electronic and opto-electronic devices,
and molecular wires.1 1,2-Terphenyl and 1,3-terphenyls have
been used industrially as heat storage and transfer agents and as
textile dye carriers whilst the 1,4-terphenyls have found applica-
c,8
2
3
9
20
tion as a laser dye. In addition, biaryls and teraryls are often pres-
ent as subunits in numerous biologically active natural products
able 1,2,4-trisubstituted byproducts, and the requirement of
expensive or specialized organometal catalysts. Herein, we re-
and pharmaceuticals.2
,10
Recently we have demonstrated that
21
1
,2,3-triarylbenzenes are potential compounds for fabricating ther-
port highly simple, economical, and environmentally benign reus-
able Amberlyst 15-catalyzed new protocol for the synthesis of
arylated benzenes in good yields.
11
mally stable blue organic light emitting diodes.
Numerous synthetic methodologies to highly functionalized
aromatic
p
-systems have been reported in the literature. A variety
Amberlyst 15 plays an important role in the synthesis of various
2
4
aliphatic and aromatic compounds. Recently Shen et al. reported
A-15-catalyzed unexpected synthesis of bis benzofuran from 1-(4-
2
4a
methoxyphenoxy)acetone in good yield.
During the studies on
q
CDRI Communication Number: 7119.
the chemistry of naturally occurring benzofuran derivatives, we
found that benzofurans functionalized on benzenoid ring with an
adjacent hydroxy and acetyl group undergoes pseudodimerization
to the corresponding bibenzofurans in the presence of Amberlyst
*
Corresponding author at present address: Institut für Organische Chemie,
Universität Würzburg, Am Hubland, 97074 Würzburg, Germany. Tel.: +49 931
8
885393; fax: +49 931 8884755.
E-mail addresses: goela@chemie.uni-wuerzburg.de, agoel13@yahoo.com
2
5
(
A. Goel).
15 in toluene at reflux temperature (Scheme 1). Some of these
0
040-4039/$ - see front matter Ó 2009 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tetlet.2009.05.029

4
336
A. Kumar et al. / Tetrahedron Letters 50 (2009) 4335–4339
COMe
Table 1
HO
Reaction of 2-acetyl-benzofuran (3) with A-15 in the presence of various solvents
HO
MeOC
HO
MeOC
A-15
Solvent
5(%)
6(%)
7(%)
toluene
reflux
a
b
c
d
e
f
Toluene
Fluorobenzene
Benzene
Dichloromethane
Tetrahydrofuran
Acetonitrile
58
35
30
20
0
23
10
5
0
0
3
0
0
0
0
0
O
O
O
1
2
(
75-92%)
Scheme 1.
0
0
bibenzofurans showed good protein tyrosine phosphatase 1B (PTP-
B) inhibitory activity for the treatment of diabetes.2
5b
1
R
In order to prepare diverse bibenzofuran derivatives for biolog-
ical screening, recently we attempted a similar reaction with 2-
acetyl-benzofuran (3) in the presence of Amberlyst 15 at reflux
temperature. Surprisingly, instead of obtaining bibenzofuran (4),
we isolated a mixture of dimer (5), trimer (6), and a tetramer (7)
of benzofuran as shown in Scheme 2. The structures of these com-
pounds were determined by spectroscopic analysis and unambigu-
O
2
5-30 mol% A-15
toluene
110-120 C
º
R
8
9
R
R
2
6
ously by
a
single crystal X-ray analysis (Scheme 2).
The
conformation of 6 and 7 along with the atom-numbering scheme
is shown in Scheme 2. The Trimer 6 and tetramer 7 crystallized
in space group C2/c and P4(2)/nbc, respectively. The structural
Scheme 3. Synthesis of 1,3,5-triphenylbenzene.
were found satisfactory. The procedure was tested using a variety
of aryl/alkyl methyl ketones to furnish useful aromatic scaffolds
9a–k) and results are presented in Table 2. It is evident from Table
analysis showed the presence of intermolecular
pÁ Á Áp interaction
and weak intra C–HÁ Á ÁO interactions in both the compounds. To
the best of our knowledge, it is the first report on such a highly hin-
dered, symmetrical, and uniquely formed cyclobutane ring bearing
four benzofuran moieties in a juxtaposed manner. In order to opti-
mize the reaction condition, reactions of 2-acetyl-benzofuran (3)
and A-15 were carried out in the presence of various solvents at
refluxing temperature for 10 h (Table 1).
(
2
that the reaction with unsubstituted or halogen-substituted ace-
tophenones (8a–i) in the presence of A-15 in reflux toluene affor-
ded 1,3,5-triarylbenzenes (9a–i) exclusively, whereas the reaction
with 4-methyl- and 4-methoxyacetophenone (8j,k) under similar
reaction conditions furnished low yields of aromatic carboxylic
acids (9j,k) together with more than 70% unreacted starting mate-
rial. The confirmation of isolated 4-methyl- and 4-methoxybenzoic
acid (9j,k) was done by comparing with the data of authentic sam-
ples. All the synthesized compounds were characterized by spec-
With the demonstration of the utility of this protocol in general,
we attempted a reaction with simple acetophenone (8a) in the
presence of Amberlyst 15 in toluene under reflux temperature
for 10 h. To our surprise, after cooling we obtained nice colorless
crystals from the reaction mixture. The crystals were filtered,
washed with hexane, and dried. The isolated compound was char-
acterized by spectroscopic analysis as 1,3,5-triphenylbenzene (9a)
2
6
troscopic analysis and known compounds were matched with
the data of the authentic samples.
A plausible mechanism for the formation of cyclotrimerized
products in the presence of Amberlyst 15 is depicted in Scheme
. The reaction may proceed through the protonation of acetophe-
(Scheme 3). Fortunately, in this case we only obtained trimerized
4
product and no dimer and tetramer were formed. The cyclotrimer-
izations of 8a and 8b were carried out in grams scale and the yields
none to form intermediates (a) and (b), followed by sequential
O
Me
O
Me
O
A-15
+
O
H
5
O
O
toluene
reflux
O
O
6
3
Dimer (58%)
Trimer (23%)
+
The crystal structure of 6
toluene
reflux
A-15 X
MeMe
COMe
O
O
O
O
MeOC
4
H
O
H
O
O
O
7
Tetramer (~2-3%)
The crystal structure of 7
Scheme 2. Synthesis of benzofuran dimer (5), trimer (6) and tetramer (7) and ORTEP structure of 6 and 7 with arbitrary numbering.

A. Kumar et al. / Tetrahedron Letters 50 (2009) 4335–4339
4337
Yield (%)
60
Table 2
Amberlyst 15-catalyzed synthesis of arylated benzenes (9a-i) and aromatic carboxylic acids (9j-k)
Reactant (8)
Product (9)
Time (h)
COCH3
a
b
c
10
Cl
COCH3
COCH3
COCH3
12
11
10
55
58
75
Cl
Br
F
Cl
Br
F
Cl
Br
Br
F
d
F
COCH3
e
18
75
f
COCH3
20
55
(continued on next page)

4
338
A. Kumar et al. / Tetrahedron Letters 50 (2009) 4335–4339
Table 2 (continued)
Reactant (8)
Product (9)
Time (h)
Yield (%)
Cl
Cl
COCH3
g
20
50
Cl
Cl
Cl
Cl
h
16
55
Cl
COCH3
Cl
Br
COCH3
i
20
45
Br
Br
Br
COCH3
COOH
j
30
32
15
10
Me
Me
COCH3
COOH
k
MeO
O
MeO
.
.
H
O
S
H
O-
H
O+
O
O
O
O
H
Ar
Ar
Ar
(b)
(a)
O
S
O
O
.
.
H
O
H
O
O+
H
H
O
O+
O
O
O
OH
Ar
-H O
Ar
2
Ar
(a)
+
Ar
H
H
A-15
Ar
Ar
Ar
Ar
Ar
Ar
Ar
OH
Ar
(
b)
(a)
-H O A-15
2
H
O+
O
OH
Ar
Ar OH
6
π-electrocyclization
Ar
Ar
-
H O
H
2
Ar
Ar
Ar
Ar
Ar
Ar
Ar
Scheme 4. Plausible reaction mechanism for the formation of triarylbenzene.

A. Kumar et al. / Tetrahedron Letters 50 (2009) 4335–4339
4339
reactions between the intermediates formed in situ, and further
16. Elmorsy, S. S.; Pelter, A.; Smith, K.; Hursthouse, M. B.; Ando, D. Tetrahedron Lett.
992, 33, 821–824.
1
internalization and
Amberlyst 15.
6p-electrocyclization in the presence of
17. Cheng, K. J.; Ding, Z. B.; Wu, S. H. Synth. Commun. 1997, 27, 11–15.
8. Mahmoodi, N. O.; Hajati, N. J. Chin. Chem. Soc. 2002, 49, 91–94.
1
In summary, we synthesized and characterized new molecular
propeller systems of benzofuran through unique polymerization
reaction of 2-acetylbenzofuran in the presence of Amberlyst 15.
The structural analysis of a trimer and tetramer of benzofuran re-
19. Shirai, H.; Amano, N.; Hashimoto, Y.; Fukui, E.; Ishii, Y.; Ogawa, M. J. Org. Chem.
991, 56, 2253–2256.
0. (a) Hopff, H.; Schweizer, H. R.; Ghertsos, A.; Heer, A.; Solarsky, A. Chimia 1958,
2, 143–146; (b) Fujii, R. J. Chem. Soc. Jp., Pure Chem. Sect. 1948, 69, 151–155.
21. Terai, H.; Takaya, H.; Naota, T. Tetrahedron Lett. 2006, 47, 1705–1708.
1
2
1
2
2. (a) Yong, L.; Butenschon, H. Chem. Commun. 2002, 2852–2853; (b) Hilt, G.;
Vogler, T.; Hess, W.; Galbiati, F. Chem. Commun. 2005, 1474–1475; (c) Conte, V.;
Elakkari, E.; Floris, B.; Mirruzzo, V.; Tagliatesta, P. Chem. Commun. 2005, 1587–
1588.
vealed the presence of intermolecular
pÁ Á Áp interaction and weak
intra C–HÁ Á ÁO interactions. The Tetramer 7 crystallized in space
group P4(2)/nbc, which rarely occurs in an organic molecule. The
new protocol is successfully applied to prepare different aromatic
scaffolds in good yields. This is a unique methodology for C–C
bond-forming reactions and may be applicable to the synthesis
of functionally congested aromatic propeller systems for their po-
tential applications in biological and material sciences. In addition,
our simple protocol and reusability of the catalyst are obvious
advantages over the known literature reports from both environ-
mental and industrial viewpoints.
23. Pena, M. A.; Perez, I.; Sestelo, J. P.; Sarandeses, L. A. Chem. Commun. 2002,
2246–2247.
24. (a) Shen, Y. D.; Wu, H. Q.; An, L. K.; Huang, Z. S.; Bu, X. Z.; Gu, L. Q. Chin. Chem.
Lett. 2005, 16, 1581–1583; (b) Das, B.; Chowdhury, N. J. Mol. Catal. A: Chem.
2007, 263, 212–215. and references cited therein.
2
5. (a) Dixit, M.; Sharon, A.; Maulik, P. R.; Goel, A. Synlett 2006, 1497–1502; (b)
Dixit, M.; Tripathi, B. K.; Tamrakar, A. K.; Srivastava, A. K.; Kumar, B.; Goel, A.
Bioorg. Med. Chem. 2007, 15, 727–734.
26. In a typical example, a solution of substituted acetophenone (1 mmol) in
toluene (7 mL) was added 25–30 mol % of Amberlyst 15 and the reaction
mixture was refluxed for 10–32 h. The reaction mixture was allowed to cool,
catalyst was filtered off, and washed several times with hot toluene. The
filtrate was concentrated under reduced pressure to afford the desired product
in good yield.
Acknowledgments
1
,3-Di(benzofuran-2-yl)but-2-en-1-one (5): White solid; mp 162–164 °C; 1H
A.G. thanks the Alexander von Humboldt Foundation, Bonn, and
Professor G. Bringmann for his research stay and kind support in
Germany. This work is supported by Department of Science and
Technology, New Delhi under Ramanna Fellowship Scheme to
A.G. (SR/S1/RFPC-10/2006). A.K. and M.D. are grateful to CSIR,
New Delhi for research fellowships. The authors thank Sophisti-
cated Analytical Instrument Facility (SAIF), Central Drug Research
Institute, Lucknow for providing spectroscopic data for the synthe-
sized compounds.
NMR (300 MHz, CDCl
ArH), 7.56 (d, J = 7.9 Hz, 1H, ArH), 7.58–7.67 (m, 3H, ArH), 7.73 (d, J = 8.8 Hz,
3
) d 2.69 (s, 3H, CH
H, ArH); 13C NMR (75.5 MHz, CDCl
) d 15.8, 109.47, 111.47, 112.48, 112.56,
3
3
), 7.15 (s, 1H, CH),7.21–7.52 (m, 4H,
2
1
1
17.79, 121.84, 123.22, 123.38, 123.87, 126.61, 127.44, 128.04, 128.60, 143.13,
À1
54.74, 155.37, 155.71, 156.12, 180.76; IR (KBr) 1649 cm (CO); MS (ESI) 303
+
(M +1).
1
(
,3,5-Tri(benzofuran-2yl)benzene (6): White solid; mp >250 °C; 1H NMR
300 MHz, CDCl ) d 7.21–7.38 (m, 9H, ArH), 7.59–7.67 (m, 6H, ArH), 8.31 (s,
3
+
3H, ArH); MS (FAB) 427 (M +1). X-ray analysis: The structural analysis shows
the presence of intermolecular
pÁ Á Áp
interaction (centroid separation
X1AÁ Á ÁX1D = 3.6472, X1AÁ Á ÁX1E = 3.7985 Å) [symmetry codes: x, 1 + y, z; x,
À1 + y, z]. The crystal packing further reveals the formation of intra C–HÁ Á ÁO
interactions
[H2Á Á ÁO2 = 2.53 Å,
\C2–H2–O2 = 100°,
C2–O2 = 2.8366 Å;
References and notes
H4Á Á ÁO1 = 2.44 Å, \C4–H4–O1 = 101°, C4–O1 = 2.6967 Å; H6Á Á ÁO3 = 2.44 Å,
C6–H6–O3 = 101°, C6–O3 = 2.7939Å].
(3,4-Di(benzofuran-2-yl)-3,4-dimethylcyclobutane-1,2-diyl)bis(benzofuran-2-yl-
methanone) (7): yellow solid; 1H NMR (200 MHz, CDCl
) d 1.37 (s, 6H, CH ),
5.58 (s, 2H, CH), 6.67 (s, 2H, CH), 7.14-7.39 (m, 10H, ArH), 7.40-7.71 (m, 8H,
\
1
.
(a) Kottas, G. S.; Clarke, L. I.; Horinek, D.; Michl, J. Chem. Rev. 2005, 105, 1281–
376; (b) Tour, J. M. Chem. Rev. 1996, 96, 537–553; (c) Tour, J. M. In Stimulating
1
3
3
Concepts in Chemistry; Vögtle, F., Stoddart, J. F., Shibasaki, M., Eds.; Wiley-VCH:
Weinheim, 2000; pp 237–253.
À1
+
ArH); IR (KBr) 1629 cm ; MS (FAB) 605 (M +1). X-ray analysis: The structural
analysis shows the presence of intermolecular (centroid separation
Á Á Á
X1BÁ Á ÁX1B = 3.5859) (centroid separation X1BÁ Á ÁX1C = 3.7095) [symmetry
2
.
(a) Trujillo, J. M.; Jorge, R. E.; Navarro, E.; Boada, J. Phytochemistry 1990, 29,
p p
2
991–2993; (b) Tsuji, K.; Nakamura, K.; Ogino, T.; Konishi, N.; Tojo, T.; Ochi, T.;
Seki, N.; Matsuo, M. Chem. Pharm. Bull. 1998, 46, 279–286; (c) Becker, F. F.;
Mukhopadhyay, C.; Hackfeld, L.; Banik, I.; Banik, B. K. Bioorg. Med. Chem. 2000,
code: 1/2 À x, y, Àz], C–HÁ Á Áp interaction [C13–H13Á Á ÁX1C, centroid distance
2.99 Å], (symmetry codes: Àx, 1 À y, Àz). The crystal packing further reveals
the formation of intra- and intermolecular C–HÁ Á ÁO interactions [H1–
O2 = 2.48 Å, \C1–H1–O2 = 108°, C1–O2 = 2.9344 Å).
8
, 2693–2699.
(a) Watson, M. D.; Fechtenkotter, A.; Mullen, K. Chem. Rev. 2001, 101, 1267–
300. and references cited therein; (b) Krishnamurthy, N.; Reddy, S. C.;
3
.
15b
1
1,3,5-Triphenylbenzene (9a): White solid; mp 170–172 °C (lit.
170–171 °C);
1
Sundaram, E. V. Indian J. Chem., Sect. A 1989, 28, 288–291.
Newkome, G. R.; Moorefield, C. N.; Vögtle, F. Dendrimers and Dendrons; Wiley-
VCH: Weinheim, 2001. p 1.
Ebert, M.; Jungbauer, D. A.; Kleppinger, R.; Wendorff, J. H.; Kohne, B.; Praefcke,
K. Liq. Cryst. 1989, 4, 53–67.
Schneider, D. J.; Landis, D. A.; Fleitz, P. A.; Seliskar, C. J.; Kaufman, J. M.; Steppel,
R. N. Laser Chem. 1991, 11, 49–62.
(a) Roncali, J. Chem. Rev. 1992, 92, 711–738; (b) Akcelrud, L. Prog. Polym. Sci.
H NMR (200 MHz, CDCl
ArH), 7.79 (s, 3H, ArH); IR (KBr) 3057, 2928, 1593 cm ; MS (FAB) 307 (M +1),
3
) d 7.34–7.53 (m, 9H, ArH), 7.71 (d, J = 8.2 Hz, 6H,
À1
+
4.
5.
6.
7.
8.
9.
+
+
(EI ) 306 (M ).
15b
1,3,5-Tris(4’-chlorophenyl)benzene (9b): White solid; mp 248–249 °C (lit.
1
257–259 °C); H NMR (200 MHz, CDCl
3
) d 7.45 (d, J = 8.4 Hz, 6H, ArH), 7.60 (d,
À1
J = 8.4 Hz, 6H, ArH), 7.69 (s, 3H, ArH); IR (KBr) 3020, 2920, 1593 cm ; MS
+
(FAB) 410 (M +1).
12b
1,3,5-Tris(4’-bromophenyl)benzene (9c): White solid; mp 260–261 °C (lit.
1
2
003, 28, 875–962.
261–262 °C); H NMR (200 MHz, CDCl
3
) d 7.49 (d, J = 8.6 Hz, 6H, ArH), 7.58 (d,
À1
(a) Berresheim, A. J.; Muller, M.; Mullen, K. Chem. Rev. 1999, 99, 1747–1785; (b)
Bunz, U. H. F.; Rubin, Y.; Tobe, Y. Chem. Soc. Rev. 1999, 28, 107–119.
(a) Goel, A.; Verma, D.; Singh, F. V. Tetrahedron Lett. 2005, 46, 8487–8491. and
references cited therein; (b) Goel, A.; Verma, D.; Dixit, M.; Raghunandan, R.;
Maulik, P. R. J. Org. Chem. 2006, 71, 804–807; (c) Goel, A.; Singh, F. V.; Dixit, M.;
Verma, D.; Raghunandan, R.; Maulik, P. R. Chem. Asian J. 2007, 2, 239–247.
J = 8.6 Hz 6H, ArH), 7.62 (s, 3H, ArH); IR (KBr) 3019, 2926, 1592 cm ; MS (FAB)
+
541 (M +1).
12b
1,3,5-Tris(4’-florophenyl)benzene (9d): White solid; mp 238–240 °C (lit.
244–
1
246 °C); H NMR (200 MHz, CDCl
3
) d 7.03–7.12 (m, 6H, ArH), 7.51–7.58 (m, 9H,
À1
+
ArH); IR (KBr) 3060, 2928, 1603 cm ; MS (FAB), 360 (M +1).
1,3,5-Tri(biphenyl)benzene (9e): White solid; mp 238–240 °C (lit.15b 239–
1
1
0. (a) Williams, D. H.; Bardsley, B. Angew. Chem., Int. Ed. 1999, 38, 1172–1193; (b)
241 °C); H NMR (200 MHz, CDCl
3
) d 7.36–7.52 (m, 10H, ArH), 7.57–7.85 (m,
À1
Nicolaou, K. C.; Boddy, C. N. C.; Brase, S.; Winssinger, N. Angew. Chem., Int. Ed.
17H, ArH), 7.90 (s, 3H, ArH); IR (KBr) 3050, 2930, 1594 cm ; MS (FAB) 534
+
1
999, 38, 2096–2152; (c) Singh, F. V.; Kumar, A.; Goel, A. Tetrahedron Lett. 2006,
(M ).
1,3,5-Tris(biphenylmethyl)benzene (9f): White solid; mp 112–114 °C (lit.15c
47, 7767–7770.
1
1
1. Goel, A.; Dixit, M.; Chaurasia, S.; Kumar, A.; Raghunandan, R.; Maulik, P. R.;
Anand, R. S. Org. Lett. 2008, 10, 2553–2556.
113–114 °C); H NMR (200 MHz, CDCl
3
) d 5.27 (s, 3H, CH), 6.61–7.06 (m, 33H,
+
ArH); MS (FAB) 576 (M ).
15d
1
2. (a) Dehmlow, E. V.; Kelle, T. Synth. Commun. 1997, 27, 2021–2031; (b) Lyle, R.
E.; DeWitt, E. J.; Nichols, N. M.; Cleland, W. J. Am. Chem. Soc. 1953, 75, 5959–
1,3,5-Tris(2’-chlorophenyl)benzene (9g): White solid; mp 162–164 °C (lit.
1
165 °C); H NMR (200 MHz, CDCl
3
) d 7.29–7.40 (m, 6H, ArH), 7.44–7.55 (m, 6H,
+
À1
5
961; (c) Wirth, H. O.; Kern, W.; Schmitz, E. Makromol. Chem. 1963, 68, 69–99.
ArH), 7.61 (s, 3H, ArH); IR (KBr) 3021, 2920, 1636 cm ; MS (FAB) 410 (M +1).
12b
1
3. (a) Lefeave, R. J. W. J. Chem. Soc. 1938, 1467–1471; (b) Sampey, J. R. J. Am. Chem.
Soc. 1940, 62, 1953; (c) Hopff, H.; Heer, A. Chimia 1959, 13, 105–108.
4. Clapp, D.; Morton, A. J. Am. Chem. Soc. 1936, 58, 2172.
5. (a) Li, Z.; Sun, W.-H.; Jin, X.; Shao, C. Synlett 2001, 1947–1949; (b) Iranpoor, N.;
Zeynizaded, B. Synlett 1998, 1079–1080; (c) Volz, H.; Lecea, M. J. V. Tetrahedron
Lett. 1966, 4683–4689; (d) Ono, F.; Ishikura, Y.; Tada, Y.; Endo, M.; Sato, T.
Synlett 2008, 2365–2367; (e) Lu, J.; Tao, Y.; D’iorio, M.; Li, Y.; Ding, J.; Day, M.
Macromolecules 2004, 37, 2442–2449.
1,3,5-Tris(3’-chlorophenyl)benzene (9h): White solid; mp 168–170 °C (lit.
1
171 °C); H NMR (200 MHz, CDCl
3
) d 7.33–7.49 (m, 6H, ArH), 7.52–7.61 (m, 3H,
À1
1
1
ArH), 7.67 (s, 3H, ArH), 7.73 (s, 3H, ArH); IR (KBr) 3022, 2926, 1635 cm ; MS
+
(FAB) 410 (M +1).
1,3,5-Tri(4’-bromobiphenyl)benzene (9i): White solid; mp >250 °C (lit.15e
1
280 °C); H NMR (200 MHz, CDCl
3
) d 7.53 (d, J = 8.4 Hz, 6H, ArH), 7.61 (d,
J = 8.4 Hz, 6H, ArH), 7.70 (d, J = 8.4 Hz, 6H, ArH), 7.81 (d, J = 8.4 Hz, 6H, ArH),
7.88 (s, 3H, ArH); IR (KBr) 3022, 2926, 1599 cm ; MS (FAB) 769 (M +1).
À1
+