Synthesis of 2,3-diiodoindenes and their applications in construction of 13H-indeno[1,2-l]phenanthrenes

Article abstract of DOI:10.1016/j.tet.2012.01.093

A series of 2,3-diiodoindene were synthesized at first, and 13H-indeno[1,2-l]phenanthrenes were then constructed via a Suzuki coupling reaction and subsequently a Scholl reaction. Structures of synthesized compounds were fully characterized by ¹H NMR, ¹³C NMR, and HRMS. Their photophysical properties, such as UV-vis and FL spectra were investigated, and electronic properties were theoretically calculated by the software of Gaussian 03. The results suggested that these modified indene and indenophenanthrene compounds might have potential applications as light emitting materials.

Full text of DOI:10.1016/j.tet.2012.01.093

Tetrahedron 68 (2012) 2844e2850
Contents lists available at SciVerse ScienceDirect
Tetrahedron
journal homepage: www.elsevier.com/locate/tet
Synthesis of 2,3-diiodoindenes and their applications in construction of
13H-indeno[1,2-l]phenanthrenes
*
*
Chao Zhou, Xiaopeng Chen, Ping Lu , Yanguang Wang
Department of Chemistry, Zhejiang University, Hangzhou 310027, China
a r t i c l e i n f o
a b s t r a c t
Article history:
A series of 2,3-diiodoindene were synthesized at first, and 13H-indeno[1,2-l]phenanthrenes were then
constructed via a Suzuki coupling reaction and subsequently a Scholl reaction. Structures of synthesized
compounds were fully characterized by 1H NMR, 13C NMR, and HRMS. Their photophysical properties, such
as UVevis and FL spectra were investigated, and electronic properties were theoretically calculated by the
software of Gaussian 03. The results suggested that these modified indene and indenophenanthrene
compounds might have potential applications as light emitting materials.
Received 25 November 2011
Received in revised form 13 January 2012
Accepted 31 January 2012
Available online 6 February 2012
Keywords:
2,3-Diiodoindenes
Ó 2012 Elsevier Ltd. All rights reserved.
Indenophenanthrene
Iodine-mediated electrophilic cyclization
Scholl oxidative coupling
Fluorescent materials
1. Introduction
the synthesis of diiodonated carbocyclic compounds in good to
excellent yields under normal reaction condition, the application of
Polysubstituted indene has played an important role in chemical
and pharmaceutical industries.1 Recently, efficient methods for the
synthesis of various carbo- and heterocyclic compounds through
electrophilic cyclization of appropriate ortho-functionalized aro-
matic acetylenes have been developed.2e11 Due to the excellent
alkynophilicity of molecular iodine, much attention has been paid
to iodine-based alkyne activation as an attractive protocol for de-
veloping new and efficient iodocyclizations. Many important
carbo- and heterocyclic compounds, such as furans,2 benzofurans,3
pyrones,4 isocoumarins,5 pyrroles,6 indoles,7 quinolines, isoquino-
lines,8 isoxazoles,9 benzo[b]thiophenes,10 naphthalenes, and
naphthols11 have been synthesized based on this strategy. Thus,
iodine-mediated electrophilic cyclizations continue to be an area of
active research in the field of synthetic chemistry.
However, almost all of these iodine-mediated electrophilic
cyclizations could only construct monoiodonated compounds, and
rare works were reported about the synthesis of diiodonated
compounds. Recently, Liang’s group has reported an iodine-medi-
ated construction of diiodinated carbocycles and oxygen hetero-
cycles via electrophilic carbocyclization of aryl propargylic alcohols,
and mentioned that the diiodinated products can be used to pre-
pare more complex products by using known organopalladium
chemistry.12 Herein, we are pleased to report a similar proposal of
the construction of 13H-indeno[1,2-l]phenanthrenes, which could
be used as potential light emitting materials.
2. Results and discussion
2.1. Iodine-mediated construction of 2,3-diiodoindenes
Firstly we examined the reaction between 2-methyl-4-
phenylbut-3-yn-2-ol (1a) and molecular iodine, it led to the for-
mation of 2,3-diiodo-1,1-dimethyl-1H-indene (2a) in methylene
chloride solution at 25 ꢀC as expected.12 The skeleton of 2,3-diiodo-
1H-indene was comparatively established by the single crystal
analysis of 2e (Fig. 1). So, we tried to optimize the reaction condi-
tions for this transformation, and the result was listed in Table 1.
Initially, we tested the molar ratio of iodine to 1a. The suitable ratio
of iodine to 1a was found to be 3:1 (Table 1, entries 1e3). The de-
hydration product, enyne (3a) was observed as a by-product. When
the reaction was conducted in dry dichloromethane (DCM), trace
amount of 2a could be detected while most of 1a was remained
(Table 1, entry 4). It meant that trace of water was necessary for this
reaction to be proceeded. Subsequently, the reaction was tested in
other solvents (Table 1, entries 5e10). It was indicated that di-
chloroethane (DCE) and acetonitrile (MeCN) were also benefited to
this reaction as DCM did. Both the reaction temperature and the
reaction time played key roles in this transformation (Table 1,
entries 11e15). By lowering the temperature of the reaction to
* Corresponding authors. E-mail addresses: pinglu@zju.edu.cn (P. Lu), orgwyg@
zju.edu.cn (Y. Wang).
0040-4020/$ e see front matter Ó 2012 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2012.01.093

C. Zhou et al. / Tetrahedron 68 (2012) 2844e2850
2845
ꢁ20 ꢀC and extending the reaction time to 12 h, the yield of 2a
increased up to 95% (Table 1, entry 15). In this case, the formation of
3a was effectively inhibited. Finally, the optimized reaction condi-
tion was established as 1 (0.30 mmol) and iodine (0.90 mmol,
3 equiv) were mixed in DCM at ꢁ20 ꢀC for a certain period of time.
worked completely, while the reaction did not work for the pyri-
dine ring because of the electron deficient.
Fig. 1. ORTEP image of 2e.
Scheme 1. Effect of aromatic part of propargylic alcohols (1aei) on the cyclization.
Table 1
Optimization of the reaction conditions for the iodine-mediated electrophilic cy-
clizations of 1aa
Secondly, we investigated the effect of R1 and R2 of propargylic
alcohols (1jeq) (Scheme 2). Compound 1j could be transferred into
2j in 84% yield under optimized reaction condition. With cyclo-
alkyl substituents, 1kem afforded the desired spiro products
2kem, but in relatively lower yield. Interestingly, when R1 was
phenyl and R2 was H, the corresponding 2,3-diiodoindene 2n
could be isolated in yield of 65%. When R1 was phenyl, R2 was
methyl or phenyl, only trace of corresponding 2,3-diiodoindene
(2o and 2p, respectively) could be detected by TLC. It was also
noticeable that 2q could be isolated in 96% yield. In this case, the
two aryl groups were fixed.
Entry
Solvent
Time (h)
Temp (ꢀC)
2a (%)b
3a (%)b
1c
2d
3
4
5
6
7
8
9
10
11
12
13
14
15
DCM
DCM
DCM
4
1
25
25
25
25
25
25
25
25
25
25
20
10
0
30
32
73
Trace
72
71
20
19
45
21
73
83
92
94
95
8
15
12
d
0.75
36
0.75
0.75
0.75
18
16
5
1
5
8
10
12
DCM (dry)
MeCN
DCE
CHCl3
CCl4
Hexane
Ethyl acetate
DCM
DCM
DCM
DCM
DCM
9
18
46
39
<5
21
12
<5
<5
<5
<5
ꢁ10
ꢁ20
a
All reactions were run under the following condition, unless otherwise in-
dicated: 1a (0.30 mmol) and I2 (0.90 mmol, 3.0 equiv) in relevant solvent (3 mL).
b
Isolated yield.
I2 (1.0 equiv, 0.30 mmol).
I2 (1.5 equiv, 0.75 mmol).
c
d
Under the optimized reaction condition in hand, we tested the
substrate diversity. Firstly, we tested the aromatic part of the
propargylic alcohol of 1 (Scheme 1). Electronic effect was signifi-
cant. When the para-substituent of the aryl of 1 was electron do-
nating, it was benefited to this cyclization. Yields of 2b, 2d, and 2e
were determined to be 97%, 90%, and 97%, respectively. As a com-
parison, the bromo-substituted propargylic alcohol 1c only affor-
ded 2c in a trace amount even though the reaction time was
extended to 72 h. In addition, cyclization to the thiophene ring
Scheme 2. Effect of R1 and R2 of propargylic alcohols (1jeq) on the cyclization.

2846
C. Zhou et al. / Tetrahedron 68 (2012) 2844e2850
Based on the observation above, we proposed a possible mecha-
nism for this iodine-mediated cyclization (Scheme 3). In the pres-
ence of trace amount of water, iodine13 acted as a Lewis acid to
generate the propargylic carbocation A, which possessed an allenic
4. The electron-donating group, such as methoxy, had little in-
fluence on the absorption spectra of 4. However, they moved to
about 350 nm after the intramolecularly oxidative coupling. Ab-
sorption around 350 nm might be assigned to
pep* transition of
carbocation
B
via MeyereSchuster rearrangement.14
B
sub-
the indenephenanthrene core of 5.19 This was also noticeable that
there was a relatively tiny shoulder peak at about 380 nm, which
might be the contribution of the lone pair electrons of the oxygen
via intramolecular charge transfer.20 These results were matched
with the energy gap calculated by the software of Gaussian 03 on
the basis set of B3LYP/6-31G(d), which was shown in Table 2.
Emissive spectra of 4aeh and 5aeh were measured in cyclo-
hexane and the results were listed in Table 2. Emission spectra of 4
and 5 were slightly changed even though their skeletons were al-
tered from indene to indenephenanthrene. For example, the
emissive spectra of 4a and 5a were almost similar with a light
emitting at 436 nm. Similar phenomenon was observed in the
previous study, which was reported by Hursthouse’s group.20
However, the quantum yield was increased significantly after the
oxidative coupling. It might be explained by the decreased non-
radiative decay of the excited state in the rigid indenophenan-
threne system of 5.
sequently abstracted the iodide to form iodoallene C. Iodination on
the electron richer double bond of C created an iodonium in-
termediate D. Finally, intramolecular FriedeleCrafts alkylation of D
afforded the final product 2.
3. Conclusions
Scheme 3. Proposed mechanism for the formation of 2.
In conclusion, an efficient synthesis of highly substituted 2,3-
diiodoindenes 2 from substituted propargylic alcohols has been
developed. In this reaction, trace amounts of water are necessary
and both iodine atoms are used efficiently. Moreover, 13H-indeno
[1,2-l]phenanthrenes 5 could be constructed easily from the
substituted 2,3-diiodoindenes 2 via Suzuki coupling reaction and
the subsequential Scholl oxidative coupling. By the investigation of
their photophysical properties, compounds 4 and 5 show potential
applications as light emitting materials.
2.2. Extension of indene to construct the skeleton of
indenophenanthrenes
As the importance of polycyclic aromatic hydrocarbons
(PAHs),15 in optoelectronic materials, it could be a potential appli-
cation of 2 for the synthesis of materials for organic solar cells and
organic light emitting diodes.16 Compound 2 could be easily con-
verted into 5 as shown in Scheme 4. Compounds 5 are typical ar-
omatic hydrocarbons (PAHs) that possess both fluorene and
phenanthrene skeletons. In this synthetic route, 2 was firstly ap-
plied for synthesizing 2,3-diarylindenes 4 via Suzuki coupling.17 (4-
Alkoxyphenyl)boronic acid was used for the Suzuki coupling as the
subsequent Scholl reaction could only be conducted with electron-
rich aromatic system.18 Finally, 5 could be obtained in relatively
high yield. By this sequential method, 2,3-diarylindenes 4aei and
13H-indeno[1,2-l]phenanthrenes 5aei (Scheme 5) are constructed
for photophysical investigation.
4. Experimental
4.1. General
Melting points were measured with micro melting point appa-
ratus. NMR spectra were recorded for 1H NMR at 400 or 500 MHz,
using TMS as internal standard and 13C NMR at 100 or 125 MHz
using CDCl3 as internal standard. The following abbreviations are
used to describe peak patterns where appropriate: br¼broad,
Scheme 4. Synthetic strategy of the synthesis of 13H-indeno[1,2-l]phenanthrenes 5.
2.3. Photophysical properties of diarylindenes and
indenophenanthrenes
s¼singlet, d¼doublet, t¼triplet, q¼quartet, m¼multiplet. Coupling
constants are reported in Hertz (Hz). All high-resolution mass
spectra (HRMS) were obtained using EI ionization. Flash column
chromatography was performed employing 300e400 mesh silica
gel. Thin layer chromatography (TLC) was performed on silica gel.
Fluorescence measurements were made with an RF-5301pc spec-
trofluorometer (Shimadzu, Kyoto, Japan) equipped with a xenon
lamp. UVevis absorption spectra were recorded on Shimadzu UV-
2450 spectrophotometer. The solvents were distilled before used.
Commercially available reagents were used without further puri-
fication unless otherwise.
Photophysical data of 4 and 5 were summarized in Table 2. The
UVevis absorption wavelengths of 4aeh and 5aeh were shown in
Table 2, while the spectra of 4aeh and 5aeh were given in
Supplementary data. The absorptive spectra of these compounds
were complex with multiple overlapping broad bands. With the
similar conjugation lengths, all the absorptive bands of 4 exhibited
similar patterns and the maximum absorptive wavelengths were
focused around 300 nm, which was attributed to indene skeleton of

C. Zhou et al. / Tetrahedron 68 (2012) 2844e2850
2847
Scheme 5. Structures of 2,3-diarylindenes 4aeh and 13H-indeno[1,2-l]phenanthrenes 5aeh.
Table 2
Absorption and emission data of 4 and 5, as well as their calculated energy levels
Cpds.
labsa/nm (
3
ꢂ10ꢁ5 Mꢁ1 cmꢁ1
)
lema/nm
Fb
HOMO/LUMOc (eV)
4a
4b
4c
4d
4e
4f
283 (0.138)
271 (0.444)
296 (0.090)
305 (0.173)
321 (0.061), 336 (0.059)
321 (0.060), 336 (0.059)
314 (0.187)
391, 413, 436
390, 412, 435
398, 420, 446
417
419
419
0.09
0.11
0.12
0.06
0.11
0.11
0.06
0.02
ꢁ5.14/ꢁ0.73
ꢁ5.07/ꢁ0.70
ꢁ4.92/ꢁ0.59
ꢁ5.10/ꢁ0.96
ꢁ5.07/ꢁ1.04
ꢁ5.02/ꢁ1.02
ꢁ5.05/ꢁ0.91
ꢁ5.00/ꢁ0.73
4g
4h
437
433
296 (0.070)
5a
5b
5c
5d
5e
5f
328 (0.313), 342 (0.310), 368 (0.065), 388 (0.066)
330 (0.204), 343 (0.197), 368 (0.045), 388 (0.043)
331 (0.156), 345 (0.155), 374 (0.029), 394 (0.028)
344 (0.075), 389 (0.018)
331 (0.116), 371 (0.048), 391 (0.047)
329 (0.118), 348 (0.118), 370 (0.048), 391 (0.047)
335 (0.097), 348 (0.091), 386 (0.024)
391, 413, 437
390, 412, 436
398, 421, 443
392, 413, 434
396, 419, 442
396, 418, 442
389, 410, 437
402, 426, 449
0.19
0.24
0.23
0.37
0.26
0.26
0.21
0.12
ꢁ4.94/ꢁ1.05
d
ꢁ4.76/ꢁ0.94
ꢁ4.92/ꢁ1.19
ꢁ4.89/ꢁ1.17
ꢁ4.80/ꢁ1.25
ꢁ5.02/ꢁ1.88
ꢁ4.83/ꢁ0.93
5g
5h
346 (0.069), 371 (0.018), 391 (0.017)
a
Absorption and emission spectra were measured in cyclohexane (1ꢂ10ꢁ5 M).
b
c
Fluorescence quantum yields were calculated using DPA as standard.
The results were calculated via the software of Gaussian 03 on the basis set of B3LYP/6-31G(d).
4.2. General procedure for the synthesis of compounds 2
solution. The aqueous solution was then extracted by dichloro-
methane (2ꢂ10 mL). The combined dichloromethane layers were
dried over anhydrous MgSO4 and concentrated under vacuum The
residue was purified through column chromatography (silica gel,
hexane/ethyl acetate as eluent) to afford a yellow oil.
These compounds were obtained following an essentially
similar procedure. An illustrative example is provided for 2a.
Compound 2a: To a solution of CH2Cl2 (5 mL), was added
2-methyl-4-phenylbut-3-yn-2-ol (0.25 mmol). After the solution
was cooled down to ꢁ20 ꢀC for 10 min, 3 equiv of I2 was added. The
reaction mixture was allowed to stir at required temperature for
the desired time. The excess I2 was removed by saturated Na2S2O3
4.2.1. Compound 2a. Yellow oil: 1H NMR (400 MHz, CDCl3)
d
7.35e7.17 (m, 4H), 1.26 (s, 6H); 13C NMR (125 MHz, CDCl3)
d
150.23, 144.02, 129.52, 127.65, 126.53, 123.43, 121.90, 106.79,

2848
C. Zhou et al. / Tetrahedron 68 (2012) 2844e2850
56.46, 25.91. HRMS: calcd for C11H10 2
I
[Mþ] (m/z) 395.8872, found
25.17, 22.20. HRMS: calcd for C15H16I2O [Mþ] (m/z) 465.9291, found
395.8879.
465.9286.
4.2.2. Compound 2b. Yellow oil: 1H NMR (400 MHz, CDCl3)
d
7.20
4.2.12. Compound 2n. Yellow oil: 1H NMR (500 MHz, CDCl3)
d 7.59
(d, J¼8.3 Hz, 1H), 6.89 (d, J¼2.3 Hz, 1H), 6.79 (dd, J¼8.3, 2.3 Hz, 1H),
(d, J¼7.3 Hz, 1H), 7.53e7.40 (m, 5H), 7.25e7.15 (m, 3H); 13C NMR
3.84 (s, 3H),1.24 (s, 6H); 13C NMR (125 MHz, CDCl3)
d
159.26, 151.60,
(125 MHz, CDCl3) d 148.57, 147.94, 140.83, 134.86, 129.06, 129.02,
137.34, 125.61, 124.01, 112.31, 108.82, 105.91, 56.34, 55.98, 26.12.
128.85, 128.42, 127.03, 126.25, 121.09, 104.23, 35.05. HRMS: calcd
HRMS: calcd for C12H12I2O [Mþ] (m/z) 425.8978, found 425.8976.
for C15H10 2
I
[Mþ] (m/z) 443.8872, found. 443.8867.
4.2.3. Compound 2d. Yellow oil: 1H NMR (400 MHz, CDCl3)
4.2.13. Compound 2q. Yellow solid: mp 155e160 ꢀC. 1H NMR
(400 MHz, CDCl3)
d
7.19e7.13 (m, 1H), 7.13e7.09 (m, 1H), 7.08e7.02 (m, 1H), 2.38 (s,
d
7.80 (d, J¼7.6 Hz, 2H), 7.41 (t, J¼7.4 Hz, 3H), 7.30
3H),1.23 (s, 6H); 13C NMR (100 MHz, CDCl3)
d
150.25, 141.58,136.48,
(t, J¼7.6 Hz, 2H), 7.18 (t, J¼7.5 Hz, 2H), 7.01 (t, J¼7.5 Hz, 1H), 6.80 (d,
128.25, 127.94, 123.06, 122.73, 106.57, 56.17, 25.98, 21.80. HRMS:
J¼7.6 Hz, 1H), 6.63 (d, J¼7.5 Hz, 1H); 13C NMR (400 MHz, CDCl3)
calcd for C12H12I2 [Mþ] (m/z) 409.9028, found 409.9031.
d 146.97, 146.18, 144.55, 142.49, 128.92, 128.39, 127.38, 124.13,
123.37, 123.22, 120.65, 120.52, 110.29, 75.01. HRMS: calcd for
4.2.4. Compound 2e. Yellow solid: mp 158e160 ꢀC. 1H NMR
C21H12 2
I
[Mþ] (m/z) 517.9028, found 517.9022.
(400 MHz, CDCl3)
d
7.61 (d, J¼7.2 Hz, 2H), 7.54e7.48 (m, 2H), 7.45 (t,
J¼7.5 Hz, 2H), 7.39e7.32 (m, 2H), 1.31 (s, 6H); 13C NMR (125 MHz,
4.3. General procedure for the synthesis of compounds 4
CDCl3) d 150.75, 143.32, 141.31, 139.80, 129.49, 129.19, 127.71, 127.62,
126.74, 123.62, 120.81, 106.33, 56.62, 26.01. HRMS: calcd for
These compounds were obtained following an essentially sim-
ilar procedure. An illustrative example is provided for 4a.
C17H14I2 [Mþ] (m/z) 471.9185, found 471.9183.
Compound 4a: To a well-mixed solution of toluene (9 mL), water
(5 mL), and ethanol (1 mL), were added 2,3-diiodo-1,1-dimethyl-
1H-indene (1 mmol), (4-methoxyphenyl)boronic acid (2.5 mmol),
and potassium carbonate (10 mmol) in was added. The reaction
mixture was stirred for 2 min. After the solution was purged with
4.2.5. Compound 2f. Yellow oil: 1H NMR (400 MHz, CDCl3)
d
9.65e9.58 (m, 1H), 7.85 (d, J¼8.2 Hz, 1H), 7.76 (d, J¼8.3 Hz, 1H),
7.61e7.55 (m, 1H), 7.50e7.42 (m, 2H), 1.29 (s, 6H); 13C NMR
(100 MHz, CDCl3) 150.25, 135.18, 133.77, 133.69, 129.19, 127.88,
127.72, 126.17, 125.65, 123.27, 120.05, 101.08, 56.28, 25.85. HRMS:
calcd for C15H12 2
[Mþ] (m/z) 445.9029, found 445.9025.
d
nitrogen for half an hour,
a catalytic amount of Pd(PPh3)4
I
(0.5 mol %) was added and the flask was flushed with N2, sealed and
allowed to stir at 90 ꢀC for 48 h. The resulting reaction mixture was
concentrated under vacuum and then was extracted with
dichloromethane (3ꢂ25 mL). The combined dichloromethane ex-
tracts were washed with water, dried over anhydrous MgSO4, and
then concentrated under vacuum. The residue was purified through
column chromatography (silica gel, hexane/ethyl acetate as eluent)
to afford a white solid.
4.2.6. Compound 2g. Yellow oil: 1H NMR (400 MHz, CDCl3)
d 9.62
(d, J¼8.7 Hz,1H), 7.87 (d, J¼8.2 Hz,1H), 7.78 (d, J¼8.3 Hz,1H), 7.59 (t,
J¼7.7 Hz, 1H), 7.52e7.43 (m, 2H), 1.30 (s, 6H); 13C NMR (100 MHz,
CDCl3) d 150.24, 135.17, 133.77, 133.58, 129.19, 127.88, 127.72, 126.17,
125.65, 123.26, 120.04, 101.08, 56.27, 25.85. HRMS: calcd for
C15H12 2
I
[Mþ] (m/z) 445.9029, found 445.9023.
4.2.7. Compound 2h. Yellow oil: 1H NMR (400 MHz, CDCl3)
d
7.25
4.3.1. Compound 4a. White solid: mp 143e145 ꢀC. 1H NMR
(d, J¼4.7 Hz, 1H), 6.88e6.81 (m, 1H), 1.27 (s, 6H); 13C NMR
(400 MHz, CDCl3) d 7.43e7.32 (m, 2H), 7.29e7.18 (m, 4H), 7.11e7.05
(100 MHz, CDCl3)
d
149.87, 148.54, 126.89, 124.34, 120.34, 98.73,
(m, 2H), 6.85e6.77 (m, 4H), 3.77 (d, J¼2.8 Hz, 6H), 1.38 (s, 6H); 13C
55.78, 26.84. HRMS: calcd for C9H8I2S [Mþ] (m/z) 401.8436, found
NMR (100 MHz, CDCl3) d 158.71, 158.64, 153.72, 152.51, 143.34,
401.8428.
137.40, 131.23, 130.97, 129.43, 127.97, 126.76, 125.53, 121.78, 120.82,
113.86, 113.80, 55.43, 51.51, 24.95. HRMS: calcd for C25H24O2 [Mþ]
(m/z) 356.1776, found 356.1771.
4.2.8. Compound 2j. Yellow oil: 1H NMR (400 MHz, CDCl3)
d
7.33e7.17 (m, 4H), 1.94e1.68 (m, 2H), 1.24 (s, 3H), 0.30 (t, J¼7.3 Hz,
3H); 13C NMR (100 MHz, CDCl3)
148.14, 145.40, 127.90, 127.62,
126.42, 123.26, 121.92, 107.13, 60.52, 32.21, 25.49, 8.29. HRMS: calcd
for C12H12 2
[Mþ] (m/z) 409.9028, found 409.9033.
d
4.3.2. Compound 4b. Yellow oil: 1H NMR (400 MHz, CDCl3)
d
7.42e7.32 (m, 2H), 7.24 (t, J¼4.2 Hz, 2H), 7.19 (d, J¼8.5 Hz, 2H),
I
7.06 (d, J¼8.5 Hz, 2H), 6.79 (d, J¼8.5 Hz, 4H), 3.91 (t, J¼6.5 Hz, 4H),
1.82e1.71 (m, 4H), 1.48e1.27 (m, 26H), 0.88 (t, J¼6.2 Hz, 6H); 13C
4.2.9. Compound 2k. Yellow oil: 1H NMR (500 MHz, CDCl3)
J¼7.5 Hz, 1H), 7.29e7.24 (m, 2H), 7.22e7.12 (m, 1H), 2.17e1.96 (m,
6H), 1.83e1.68 (m, 2H); 13C NMR (125 MHz, CDCl3)
152.90, 143.82,
d
7.31 (d,
NMR (100 MHz, CDCl3) d 158.29, 158.22, 153.74, 152.51, 143.41,
137.35, 131.20, 130.94, 129.22, 127.75, 126.74, 125.47, 121.77, 120.82,
114.36, 114.29, 68.16, 51.50, 32.17, 29.73, 29.68, 29.59, 26.44, 24.97,
23.01, 14.46. HRMS: calcd for C39H52O2 [Mþ] (m/z) 552.3967, found
552.3973.
d
129.92, 127.38, 126.55, 123.21, 121.45, 106.63, 66.49, 37.52, 27.04.
HRMS: calcd for C13H12I2 [Mþ] (m/z) 421.9028, found 445.9029.
4.2.10. Compound 2l. Yellow oil: 1H NMR (500 MHz, CDCl3)
d
7.77
4.3.3. Compound 4c. Yellow solid: mp 128e130 ꢀC. 1H NMR
(d, J¼7.6 Hz, 1H), 7.34 (m, J¼12.2, 8.2, 3.8 Hz, 2H), 7.17 (m, J¼7.5,
(400 MHz, CDCl3)
d
7.25 (q, J¼3.8 Hz,1H), 7.20 (d, J¼8.4 Hz, 2H), 7.07
1.2 Hz, 1H), 2.12e1.78 (m, 7H), 1.52e1.37 (m, 1H), 1.21 (dd, J¼8.3,
(d, J¼8.4 Hz, 2H), 6.98 (d, J¼2.1 Hz, 1H), 6.86e6.76 (m, 5H), 3.86 (s,
6.4 Hz, 2H); 13C NMR (100 MHz, CDCl3)
d 148.52, 144.93, 132.46,
3H), 3.78 (d, J¼2.9 Hz, 6H), 1.36 (s, 6H); 13C NMR (100 MHz, CDCl3)
127.71, 125.27, 123.94, 123.82, 107.81, 58.99, 33.78, 25.25, 22.44.
d 158.61, 155.64, 150.46, 136.88, 136.37, 131.34, 130.90, 129.62,
HRMS: calcd for C14H14 2
I
[Mþ] (m/z) 435.9185, found 435.9182.
128.20, 121.28, 113.84, 113.76, 111.57, 108.75, 55.92, 55.42, 51.40,
25.21. HRMS: calcd for C26H26O3 [Mþ] (m/z) 386.1882, found
386.1886.
4.2.11. Compound 2m. Yellow oil: 1H NMR (500 MHz, CDCl3)
d 7.38
(d, J¼2.1 Hz, 1H), 7.25 (d, J¼3.5 Hz, 1H), 6.84 (dd, J¼8.3, 2.2 Hz, 1H),
3.85 (s, 3H), 2.07e1.77 (m, 7H), 1.41 (dt, J¼12.8, 3.8 Hz, 1H),
4.3.4. Compound 4d. Yellow solid: mp 169e170 ꢀC. 1H NMR
1.28e1.15 (m, 2H); 13C NMR (125 MHz, CDCl3)
d
157.88, 149.61,
(400 MHz, CDCl3)
d 7.70e7.61 (m, 3H), 7.55e7.40 (m, 4H), 7.34 (t,
138.30, 128.76, 124.17, 112.06, 111.33, 106.92, 58.76, 56.00, 33.70,
J¼7.3 Hz, 1H), 7.24 (d, J¼7.7 Hz, 3H), 7.10 (d, J¼8.6 Hz, 2H), 6.83 (d,

C. Zhou et al. / Tetrahedron 68 (2012) 2844e2850
2849
J¼8.6 Hz, 4H), 3.79 (s, 6H), 1.44 (s, 6H); 13C NMR (100 MHz, CDCl3)
122.32, 116.62, 116.42, 106.21, 106.01, 55.84, 48.24, 26.88. HRMS:
d
158.78, 158.72, 154.40, 152.95, 142.72, 142.20, 138.81, 137.20,
calcd for C25H22O2 [Mþ] (m/z) 354.1620, found 354.1629.
131.23, 130.97, 129.40, 129.07, 127.96, 127.57, 127.24, 125.96, 121.06,
120.77, 113.94, 113.84, 55.46, 51.68, 25.07. HRMS: calcd for C31H28O2
[Mþ] (m/z) 432.2089, found 432.2092.
4.4.2. Compound 5b. Yellow oil. 1H NMR (400 MHz, CDCl3)
d 8.83
(d, J¼9.1 Hz,1H), 8.34 (d, J¼7.7 Hz,1H), 8.24 (d, J¼8.9 Hz,1H), 8.10 (s,
2H), 7.58 (d, J¼7.5 Hz, 1H), 7.49e7.43 (m, 1H), 7.36 (m, 3H), 4.21 (t,
J¼6.4 Hz, 4H),1.99e1.84 (m, 4H),1.75 (s, 5H),1.56 (dt, J¼13.5, 6.7 Hz,
4H), 1.49e1.27 (m, 17H), 0.90 (t, J¼6.8 Hz, 6H); 13C NMR (100 MHz,
4.3.5. Compound 4e. Yellow solid: mp 189e190 ꢀC. 1H NMR
(400 MHz, CDCl3)
d
7.85 (d, J¼8.2 Hz,1H), 7.78 (d, J¼8.2 Hz,1H), 7.59
(d, J¼8.2 Hz, 1H), 7.51 (d, J¼8.6 Hz, 1H), 7.33 (t, J¼7.5 Hz, 1H),
7.22e7.11 (m, 3H), 7.04 (d, J¼8.6 Hz, 2H), 6.84 (d, J¼8.6 Hz, 2H), 6.78
(d, J¼8.6 Hz, 2H), 3.82 (s, 3H), 3.77 (s, 3H), 1.43 (s, 6H); 13C NMR
CDCl3) d 157.38, 156.71, 145.32, 140.44, 132.47, 132.34, 130.35,
127.93, 127.21, 126.89, 126.27, 126.09, 124.40, 124.03, 122.85, 122.27,
116.89, 116.68, 107.16, 106.98, 68.64, 48.20, 32.19, 29.79, 29.64,
26.89, 26.51, 23.03, 14.46. HRMS: calcd for C39H50O2 [Mþ] (m/z)
550.3811, found 550.3816.
(100 MHz, CDCl3)
d 158.71, 158.53, 155.35, 151.49, 139.42, 137.73,
134.01, 131.45, 131.19, 130.63, 129.20, 129.02, 128.97, 126.43, 125.43,
124.78, 124.76, 120.38, 113.85, 113.59, 55.46, 55.40, 51.49, 24.28.
HRMS: calcd for C29H26O2 [Mþ] (m/z) 406.1933, found 406.1942.
4.4.3. Compound 5c. Yellow solid: mp 215e217 ꢀC. 1H NMR
(400 MHz, CDCl3)
d
8.77 (d, J¼9.0 Hz,1H), 8.23 (d, J¼8.8 Hz, 2H), 8.09
4.3.6. Compound 4f. Yellow solid: mp 189e190 ꢀC. 1H NMR
(d, J¼2.2 Hz, 2H), 7.35 (m, 2H), 7.13 (d, J¼2.3 Hz, 1H), 6.98 (dd, J¼8.5,
(400 MHz, CDCl3)
d
7.86 (d, J¼8.2 Hz,1H), 7.78 (d, J¼8.3 Hz,1H), 7.59
2.3 Hz, 1H), 4.03 (d, J¼2.0 Hz, 6H), 3.92 (s, 3H), 1.74 (s, 6H); 13C NMR
(d, J¼8.2 Hz, 1H), 7.51 (d, J¼8.6 Hz, 1H), 7.33 (t, J¼7.2 Hz, 1H),
7.23e7.11 (m, 3H), 7.04 (d, J¼8.7 Hz, 2H), 6.85 (d, J¼8.6 Hz, 2H), 6.78
(d, J¼8.7 Hz, 2H), 3.83 (s, 3H), 3.77 (s, 3H), 1.43 (s, 6H); 13C NMR
(100 MHz, CDCl3) d 158.84, 158.81, 157.68, 157.45, 144.24, 133.31,
132.20, 131.81, 130.44, 126.60, 126.30, 124.31, 124.27, 123.46, 116.53,
116.40, 112.19, 108.79, 106.19, 105.94, 55.83, 55.80, 48.19, 27.09.
HRMS: calcd for C26H24O3 [Mþ] (m/z) 384.1725, found 384.1731.
(100 MHz, CDCl3)
d 158.72, 158.54, 155.35, 151.49, 139.43, 137.73,
134.02, 131.45, 131.19, 130.64, 129.21, 129.03, 128.98, 126.43, 125.44,
124.79, 124.76, 120.39, 113.85, 113.59, 55.47, 55.41, 51.50, 24.28.
HRMS: calcd for C29H26O2 [Mþ] (m/z) 406.1933, found 406.1927.
4.4.4. Compound 5d. Yellow solid: mp 249e250 ꢀC. 1H NMR
(400 MHz, CDCl3)
d
8.86 (d, J¼9.1 Hz,1H), 8.39 (d, J¼8.1 Hz,1H), 8.28
(d, J¼9.1 Hz, 1H), 8.12 (s, 2H), 7.80 (s, 1H), 7.71 (dd, J¼16.5, 8.0 Hz,
3H), 7.49 (t, J¼7.6 Hz, 2H), 7.38 (td, J¼11.4, 2.3 Hz, 3H), 4.05 (d,
J¼1.9 Hz, 6H),1.81 (s, 6H); 13C NMR (100 MHz, CDCl3) 157.86,157.82,
157.40, 145.75, 141.80, 139.62, 139.13, 132.42, 132.31, 129.17, 127.53,
127.47, 127.04, 126.45, 126.33, 124.47, 124.21, 123.09, 121.04, 116.69,
116.48, 106.27, 106.05, 55.88, 48.39, 26.99. HRMS: calcd for
C31H26O2 [Mþ] (m/z) 430.1933, found 430.1938.
4.3.7. Compound 4g. White solid: mp 250e253 ꢀC. 1H NMR
(400 MHz, CDCl3)
d
7.77 (d, J¼7.6 Hz, 2H), 7.40 (t, J¼7.8 Hz, 3H), 7.33
(t, J¼7.5 Hz, 2H), 7.21 (d, J¼7.5 Hz, 1H), 7.14 (t, J¼7.5 Hz, 2H),
7.06e6.91 (m, 5H), 6.58 (d, J¼7.5 Hz,1H), 6.52 (d, J¼8.2 Hz, 2H), 6.35
(d, J¼8.4 Hz, 2H), 3.84 (s, 3H), 3.55 (s, 3H); 13C NMR (100 MHz,
CDCl3)
d 159.18, 158.40, 149.20, 146.99, 145.92, 144.88, 142.53,
141.66, 131.17, 130.12, 128.23, 128.05, 127.95, 127.29, 126.25, 123.98,
122.59, 120.71, 120.52, 114.41, 113.30, 70.35, 55.53, 55.10. HRMS:
calcd for C35H26O2 [Mþ] (m/z) 478.1993, found 478.1991.
4.4.5. Compound 5e. Yellow solid: mp 182e184 ꢀC. 1H NMR
(400 MHz, CDCl3)
d
8.98 (d, J¼9.1 Hz, 1H), 8.60 (d, J¼8.7 Hz, 1H),
8.38 (t, J¼8.2 Hz, 2H), 8.13 (d, J¼1.9 Hz, 2H), 7.99 (t, J¼7.5 Hz, 2H),
7.61 (t, J¼7.6 Hz, 1H), 7.49 (t, J¼7.4 Hz, 1H), 7.39 (m, 2H), 4.03 (s, 6H),
4.3.8. Compound 4h. Yellow solid: mp 65e67 ꢀC. 1H NMR
(400 MHz, CDCl3)
4.9 Hz, 3H), 6.84 (d, J¼8.4 Hz, 2H), 6.76 (d, J¼8.5 Hz, 2H), 3.80 (s,
3H), 3.76 (s, 3H), 1.40 (s, 6H); 13C NMR (101 MHz, CD3Cl)
158.75,
d
7.27 (dd, J¼11.8, 7.3 Hz, 3H), 7.09 (dd, J¼6.1,
1.99 (s, 6H); 13C NMR (100 MHz, CDCl3)
d 157.71, 150.86, 147.84,
137.87, 133.08, 132.42, 132.29, 130.31, 129.89, 128.87, 128.57, 126.79,
126.37, 126.22, 124.89, 124.39, 124.32, 123.49, 121.81, 116.56, 116.42,
106.39, 106.15, 55.86, 49.73, 26.44. HRMS: calcd for C29H24O2 [Mþ]
(m/z) 404.1776, found 404.1787.
d
158.59, 154.14, 152.33, 146.06, 134.22, 131.37, 130.13, 129.66, 128.47,
126.37, 120.01, 113.97, 113.75, 55.28, 50.92, 25.81. HRMS: calcd for
C23H23O2S [Mþ] (m/z) 362.1341, found 362.1343.
4.4.6. Compound 5f. Yellow solid: mp 182e184 ꢀC. 1H NMR
4.4. General procedure for the synthesis of the compounds 5
(400 MHz, CDCl3)
d
9.00 (d, J¼9.1 Hz, 1H), 8.62 (d, J¼8.7 Hz, 1H),
8.48e8.34 (m, 2H), 8.15 (d, J¼2.1 Hz, 2H), 8.01 (dd, J¼8.2, 5.1 Hz,
2H), 7.63 (t, J¼7.6 Hz, 1H), 7.51 (t, J¼7.5 Hz, 1H), 7.41 (m, 2H), 4.07 (d,
These compounds were obtained following an essentially sim-
ilar procedure. An illustrative example is provided for 5a.
J¼1.6 Hz, 6H), 2.02 (s, 6H); 13C NMR (100 MHz, CDCl3)
d 157.74,
Compound 5a: A solution of 2,3-bis(4-methoxyphenyl)-1,1-di-
methyl-1H-indene (0.1 mmol) in dichloromethane (10 mL) was
cooled to w0 ꢀC. After the solutionwas purged with nitrogen for half
an hour, FeCl3 (0.5 mol) was added and the flask was flushed with N2,
sealed and allowed to stir at required temperature for the desired
time. After completion of the reaction, it was quenched with a sat-
urated aqueous solution of NaHCO3 (20 mL). The dichloromethane
layer was separated, washed with water and brine solution, dried
over anhydrous MgSO4, and concentrated under vacuum. The resi-
due was purified through column chromatography (silica gel, hex-
ane/ethyl acetate as eluent) to afford a white solid.
137.88, 133.10, 132.44, 132.31, 130.35, 129.90, 128.88, 128.58, 126.82,
126.41, 126.23, 124.92, 124.41, 124.35, 123.50, 121.83, 116.59, 116.45,
106.39, 106.17, 55.91, 49.75, 26.47. HRMS: calcd for C25H24O2 [Mþ]
(m/z) 404.1776, found 404.1780.
4.4.7. Compound 5g. Yellow solid: mp 264e266 ꢀC. 1H NMR
(400 MHz, CDCl3)
d
8.95 (d, J¼9.0 Hz,1H), 8.40 (d, J¼7.8 Hz,1H), 8.11
(d, J¼2.5 Hz, 1H), 7.97 (d, J¼7.4 Hz, 3H), 7.47 (dd, J¼9.0, 2.5 Hz, 1H),
7.39 (td, J¼7.5, 3.6 Hz, 3H), 7.05 (dd, J¼13.4, 6.8 Hz, 3H), 6.77 (dd,
J¼9.0, 2.4 Hz, 1H), 6.72e6.67 (m, 3H), 6.64 (d, J¼7.5 Hz, 1H), 4.07 (s,
3H), 3.86 (s, 3H); 13C NMR (100 MHz, CDCl3)
d 158.14, 158.03, 151.11,
149.31, 142.68, 141.89, 139.92, 134.56, 133.08, 132.10, 128.38, 128.19,
128.10, 127.70, 126.67, 126.47, 124.29, 124.13, 123.60, 123.38, 122.79,
120.85, 116.80, 116.65, 106.17, 105.88, 66.65, 55.92, 55.69. HRMS:
calcd for C35H24O2 [Mþ] (m/z) 476.1776, found 476.1775.
4.4.1. Compound 5a. Yellow solid: mp 147e150 ꢀC. 1H NMR
(500 MHz, CDCl3)
d
8.84 (d, J¼9.0 Hz, 1H), 8.34 (d, J¼7.8 Hz, 1H),
8.26 (d, J¼9.0 Hz, 1H), 8.10 (t, J¼2.2 Hz, 2H), 7.58 (d, J¼7.4 Hz, 1H),
7.51e7.42 (m, 1H), 7.36 (m, 3H), 4.03 (s, 6H), 1.75 (s, 6H); 13C NMR
(125 MHz, CDCl3)
d
157.81, 157.74, 156.71, 145.42, 140.35, 132.38,
4.4.8. Compound 5h. Yellow solid: mp 180e181 ꢀC. 1H NMR
132.27, 130.48, 127.25, 127.03, 126.41, 126.19, 124.53, 124.18, 122.88,
(400 MHz, CDCl3)
d
8.48 (d, J¼8.9 Hz,1H), 8.15 (d, J¼9.1 Hz, 3H), 8.08

2850
C. Zhou et al. / Tetrahedron 68 (2012) 2844e2850
6. (a) Knight, D. W.; Redfem, A. L.; Gilmore, J. J. Chem. Soc., Perkin Trans. 1 2002,
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7.40e7.31 (m, 2H), 4.04 (d, J¼2.4 Hz, 6H), 1.80 (s, 6H); 13C NMR
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d 158.87, 157.96, 157.05, 146.36, 142.24, 131.65,
130.80, 130.38, 127.45, 126.90, 125.59, 124.57, 123.08, 121.02, 116.80,
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Supplementary data
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