A simple access to triarylmethane derivatives from aromatic aldehydes and electron-rich arenes catalyzed by FeCl3

Article abstract of DOI:10.1016/j.tet.2007.11.080

Under 'open-flask' and mild conditions, arenes condense smoothly with aromatic aldehydes in the presence of catalytic amount of FeCl₃. The reaction tolerated a variety of substitutions and functional groups. This method provides a facile and di

Full text of DOI:10.1016/j.tet.2007.11.080

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Tetrahedron 64 (2008) 1924e1930
www.elsevier.com/locate/tet
A simple access to triarylmethane derivatives from aromatic aldehydes
and electron-rich arenes catalyzed by FeCl3
*
Zhongxian Li, Zheng Duan , Jianxun Kang, Huaiqiu Wang, Liujian Yu, Yangjie Wu
*
Chemistry Department, Key Lab of Chemical Biology and Organic Chemistry of Henan Province, Key and Open Lab of Applied Chemistry
of Henan Universities, Zhengzhou University, Zhengzhou 450052, PR China
Received 15 August 2007; received in revised form 17 November 2007; accepted 23 November 2007
Available online 26 December 2007
Abstract
Under ‘open-flask’ and mild conditions, arenes condense smoothly with aromatic aldehydes in the presence of catalytic amount of FeCl3. The
reaction tolerated a variety of substitutions and functional groups. This method provides a facile and direct access to symmetrical and unsym-
metrical triarylmethane derivatives.
Ó 2007 Elsevier Ltd. All rights reserved.
Keywords: Triarylmethane; Diarylmethane; FeCl3; Catalyzed
1. Introduction
styrenes,10 benzylation of 1,3-dicarbonyl compounds,11 and
intramolecular hydroamination and hydroalkoxylation of al-
kenes12 have highlighted the applications of FeCl3 in organic
synthesis. In this contribution, we disclose a simple and prac-
tical synthesis of TRAMs derivatives from aromatic aldehydes
and arenes catalyzed by FeCl3. Mild reaction conditions and
environmentally friendly catalyst make this transformation
an attractive option for the straightforward preparation of
triarylmethanes.
Triarylmethanes (TRAMs) constitute an important class of
compounds1 that are ubiquitous in material,2 medicals,3 and
dyes.4 Numerous methods have been developed for the synthe-
sis of TRAMs. However, most of them require complex proce-
dures or harsh reaction conditions.5 The FriedeleCrafts6 type
catalytic alkylation of aromatic rings with aromatic aldehydes
and their imines are emerging as effective methods for
TRAMs formation.7 Very recently, several mild and efficient
triaryl- and triheteroarylmethanes formations were reported,
which used [Ir(COD)Cl]2eSnCl4,7a AuCl3,7b Cu(OTf)2, and
2. Results and discussion
7j
Sc(OTf)3 as catalysts. The quest for cheap, environmentally
friendly catalysts, and mild reaction conditions is still a major
challenge.
The initial FeCl3 catalyzed TRAMs formation13,14 was car-
ried out with benzaldehyde 1a and p-xylene 2a. After exten-
sive studies on the reaction conditions, we found that the
addition of acetic anhydride can improve the yield of 3a dra-
matically (Scheme 1).15 It was shown that, in the presence of
acetic anhydride, the reactions proceeded smoothly with both
electron-rich and electron-poor aromatic aldehydes and acety-
lation of arenes was not observed in these reactions. Longer
reaction times were required (50 h) when highly electron defi-
cient p-nitrobenzaldehyde was used (Scheme 1, 3e).
FeCl3 is a ‘green’ and efficient catalyst in modern organic
synthesis.8 It has become the focus of attention in several
environmentally friendly and atom-economical organic trans-
formations. Recent reports on FeCl3 catalyzed arylation of
benzyl alcohols and benzyl carboxylates,9 hydroarylation of
* Corresponding authors. Tel.: þ86 371 67767993; fax: þ86 371 67979408.
E-mail addresses: duanzheng@zzu.edu.cn (Z. Duan), wyj@zzu.edu.cn
(Y. Wu).
Further researches revealed that various arenes could be
condensed with aromatic aldehydes effectively (Table 1).
0040-4020/$ - see front matter Ó 2007 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2007.11.080

Z. Li et al. / Tetrahedron 64 (2008) 1924e1930
1925
Me
Me
Even the bulky 1,3,5-trimethylbenzene could be used and the
desired product was isolated in 70% yield (entry 8). When
high electron donating group (MeOe) substituted 2b and 2c
were used, the desired products were obtained with high regio-
selectivity (entries 1e5). Importantly, this method provides
a mild and controlled entry into halogen substituted TRAMs.
These halides are synthetically useful because they afford
a direct and regioselective introduction of a wide variety of
functional groups via simple cross-coupling reactions. Obvi-
ously, electron-rich aromatic rings are necessary for this
FriedeleCrafts type reaction.
CHO
Me
Me
Me
FeCl3(10 mol%)
Ac2O, 80 °C
+
R
R
1
2a
3
Me
3a(79%), R=H(1a), 22 h 3b(78%), R=Br(1b), 22 h
3c(75%), R=Cl(1c), 22 h 3d(85%), R=Me(1d), 10 h
3e(70%), R=NO2(1e), 50 h
Scheme 1. FeCl3 catalyzed TRAMs formations.
Interestingly, when the reaction between benzaldehydes 1a
and p-xylene was carried out at 0 ꢀC, the mono-aromatic sub-
stitution product 4a was isolated in 43% yield. The reaction
with bulky arenes 2d and 2e provided 4b and 4c, respectively,
in good to high yield at room temperature (Scheme 2).
Table 1
FeCl3 catalyzed reaction of arenes with aromatic aldehydesa
Ar'
FeCl3 10 mol%
Ar' CHO
Ar-H
+
Ac
2O, 80 °C, 22 h
Ar
Ar
1
2
3
OAc
Ar
FeCl3, Ac2O (2 mmol)
CH2Cl2
+
Ar-H
PhCHO
Entry
Ar0CHO
AreH
Product
Yieldb (%)
Ph
1a
2
4
Br
4a (43%) Ar-H = p-xylene (2a), 0 °C, 12 h
4b ( 92%) Ar-H = mesitylene (2d), r.t., 2 h
4c (70%) Ar-H=1,2,4,5-tetramethylbenzene (2e), r.t., 6 h
OMe
CHO
OMe
Br
Br
Scheme 2.
1
80
MeO
Br
1b
Br
2c
We considered whether our described mono-aromatic sub-
stitution procedure could be adapted toward a convenient
one-pot synthesis of unsymmetrical TRAMs starting from
aromatic aldehydes and arenes, thus avoiding the isolation of
the diarylmethane intermediates. To our delight, this sequen-
tial one-pot procedure proceeded very well with bulky arenes
2d and 2e (Table 2). A variety of unsymmetrical TRAMs and
thiophene, furan and indole substituted hetroaryldiaryl-
methanes were isolated in good yields.16
3f
Br
OMe
OMe
CHO
Cl
Cl
2
77
MeO
3g
Br
Cl
2b
Cl
1g
To extend this method further to synthesis of unsymmetri-
cal TRAMs that do not contain bulky arene, we also per-
formed aromatic substitution with 4d. As shown in Scheme
3, the bromine substituted 3u was obtained in high yield.
From these results, we proposed that aldehydes react with
acetic anhydride to form more reactive geminal diacetates in
situ,17 and the following arylation of diacetates provide
TRAMs or diarylmethane derivatives. The different reactivity
of aldehydes and benzyl acetate in the iron catalyzed arylation
reaction was also observed by Beller and co-workers.9d Fur-
ther research was carried out to clarify the role of Ac2O and
FeCl3. First, the reaction between benzaldehyde and Ac2O
was carried out and the diacetate 5a was obtained in 60% iso-
lated yield (Eq. 1). The purified 5a was reacted with 2a. To our
surprise, benzaldehyde was isolated in 46% yield and the
desired 3a was only isolated in 51% yield in this case (Eq.
2). We thought benzaldehyde came from the deprotected di-
acetate18 and there is an equilibrium between aldehyde 1a and
diacetate 5a. Next, we investigated the reaction between 2a
and purified 5a in the presence of Ac2O. The desired 3a was
isolated in 78% yield and a small amount of benzaldehyde
1a (Eq. 3). Following conclusions were drawn from these
results: (a) in the presence of Ac2O and catalytic amount of
OMe
Br
CHO
3
2b
59
Br
MeO
3h
Cl
1f
4
1b
1a
1g
2b
2b
2a
3i
3j
89
83
90
5
6c,d
3k
CHO
7c
2a
3l
80
70
Cl
1h
Me
8e
1a
3m
Me
Me
2d
a
Reaction conditions: aldehyde (1 mmol), arene (4 mmol), Ac2O (3 mmol).
Isolated yield.
b
c
d
e
The reaction was carried out with 2 mL 2a.
The reaction time was 16 h.
The reaction was carried out with 1 mL 2d.

1926
Z. Li et al. / Tetrahedron 64 (2008) 1924e1930
Table 2
One-pot FeCl3 catalyzed unsymmetrical triarylmethanes formationa
the presence of the Ac2O, we postulated that this equilibrium
would be mainly shifted to diacetate.
Ar1
1, Ar1H
2, Ar2H
Ar CHO
OAc
Ar2
Ar
FeCl3(10 mol%)
+ Ac O
CHO
2
ð1Þ
80 °C, 2h
OAc
Yieldb
(%)
Entry ArCHO Ar1H
Ar2H
Product
1a
5a
Ar1
OMe
Br
Me
Me
FeCl3(10 mol%)
80 °C, 5h
OAc
OAc
1c
1a
2d
2c
89
+
CHO
TRAM
+
3n
3a (iso.51%) 1a (iso.46%)
5a
2a
Ar1
OMe
OMe
ð2Þ
ð3Þ
2
3
1a
1a
2d
2d
47
65
OMe
Ac2O(2eq.)
MeO
MeO
OMe
3a
+
1a
5a
+
2a
2f
FeCl3(10 mol%)
80 °C, 3h
3o
(iso.78%)
(iso.8%)
Ar1
3. Conclusion
N
H
NH
2g
3p
Ar1
In summary, we have developed an efficient FeCl3 catalyzed
alkylation of arenes with aromatic aldehydes. This method
provides a facile and direct access to symmetrical and unsym-
metrical triarylmethane and diarylmethane derivatives. The
presence of acetic anhydride is crucial to this FeCl3 catalyzed
TRAMs formations. In addition, the reaction tolerated a variety
of substitutions and functional groups. The readily available,
cheap, low toxic, and easy-handling iron catalyst, plus the
‘open-flask’ and mild reaction conditions, is noteworthy.
Me
Me
Me
4
1g
2d
63
O
2h
O
Me
3q
Ar1
Br
CHO
Me
5
6
2d
2d
2h
91
61
O
Me
Me
3r
Me
1d
4. Experimental section
Ar1
4.1. General procedures
Me
Me
Me
1a
1b
S
2i
S
Me
3s
Ar1
All the reactions were carried out under air atmosphere. 1H
and 13C NMR spectra were recorded at room temperature on
a Bruker 400 MHz spectrometer with CDCl3 as solvent and
tetramethylsilane (TMS) as internal standard. Chemical shifts
were reported in units (ppm) by assigning TMS resonance in
OMe
OMe
Me
7
2e
65
Br
Me
2j
1
the H spectrum as 0.00 ppm and CDCl3 resonance in the
3t
13C spectrum as 77.0 ppm. All coupling constants (J values)
were reported in hertz (Hz). Elemental analyses are performed
on an Elementar Analysensysteme GmbH, VarioEL III or Flash
EA 1112 series of the Thermo Electron Corporation. High reso-
lution mass spectra were recorded on a Waters Q-Tof microÔ
spectrometer by electrospray ionization (ESI) mass spectrome-
ter; GC using an Agilent gas chromatograph 4890D. Prepara-
tive TLC was performed using silica gel as the stationary
phase. Unless otherwise noted, all starting materials were com-
mercially available and were used without further purification.
a
Reaction conditions: aldehyde (1 mmol), arene (4 mmol), FeCl3 (10 mol %),
Ac2O (2 mmol), CH2Cl2 (2 mL), rt.
b
Isolated yield.
The reaction with second arene was carried out at 80 ꢀC.
c
FeCl3, aldehyde was converted into more reactive geminal
diacetate in situ, (b) there is an equilibrium between aldehyde
and diacetate. Due to FeCl3 catalyzed TRAM formation and
Me
S
Me
OAc Me
S
FeCl3, Ac2O
Me
Me
Me
1b + 2a
Me
4.2. General procedure for synthesis of triarylmethanes
3a, 3b, 3c, 3d, 3e, 3k, and 3l
2 h
Br
Br
Me
4d (43%)
Scheme 3.
3u (96%)
To a 10-mL flask, benzaldehyde (1 mmol), acetic anhydride
(3 mmol), anhydrous FeCl3 (16.2 mg, 0.1 mmol), and p-xylene

Z. Li et al. / Tetrahedron 64 (2008) 1924e1930
1927
(2 mL) were successively added, and then the mixture was
4.7. General procedure for synthesis of diacetate 5a
magnetically stirred at 80 ꢀC for 22 h. The solvent was con-
centrated under reduced pressure by an aspirator, and the resi-
due was purified by preparative TLC using petroleum as an
eluent to afford 3a, 3b, 3c, 3d, 3k, and 3l; for 3e: 10:1 petro-
leum/ethyl acetate was used as an eluent.
Aldehyde (1 mmol), acetic anhydride (2 mmol), and anhy-
drous FeCl3 (16.2 mg, 0.1 mmol) were sequentially added to
a 10-mL flask, and the mixture was magnetically stirred at
80 ꢀC for 2 h and then the residue was purified by preparative
TLC using 10:1petroleum/ethyl acetateas an eluent to afford 5a.
4.3. General procedure for synthesis of triarylmethanes
3g, 3f, 3h, 3i, 3j, and 3m
4.8. The reaction of diacetate (5a) with p-xylene
Benzaldehyde (1 mmol), acetic anhydride (3 mmol), anhy-
drous FeCl3 (16.2 mg, 0.1 mmol), and electronic-rich arene
(4 mmol) were successively added to a 10-mL flask. The reac-
tion mixture was stirred at 80 ꢀC for 22 h. The mixture was
purified by preparative TLC using 10:1 petroleum/ethyl ace-
tate as eluent to afford 3g, 3f, 3h, 3i, and 3j; for 3m: 1 mL
mesitylene was used, and petroleum was used as an eluent
for purification.
To a 10-mL flask, diacetate (5a) (1 mmol), p-xylene
(2 mL), and anhydrous FeCl3 (16.2 mg, 0.1 mmol) were suc-
cessively added, and then the mixture was magnetically stirred
at 80 ꢀC for 5 h. The solvent was concentrated under reduced
pressure by an aspirator, and the residue was purified by pre-
parative TLC using 10:1 petroleum/ethyl acetate as an eluent
to afford 3a and 1a.
4.9. The reaction of diacetate (5a) with p-xylene in the
presence of acetic anhydride
4.4. General procedure for synthesis of diphenylmethyl
acetate 4a, 4b, 4c, and 4d
To a 10-mL flask, diacetate (5a) (1 mmol), acetic anhydride
(2 mmol), p-xylene (2 mL), and anhydrous FeCl3 (16.2 mg,
0.1 mmol) were successively added, and then the mixture
was magnetically stirred at 80 ꢀC for 3 h. The solvent was con-
centrated under reduced pressure by an aspirator, and the res-
idue was purified by preparative TLC using 10:1 petroleum/
ethyl acetate as an eluent to afford 3a and 1a.
Aldehyde (1 mmol), acetic anhydride (2 mmol), electronic-
rich arene (1 mmol), dichloromethane (DCM), (2 mL) and an-
hydrous FeCl3 (16.2 mg, 0.1 mmol) were sequentially added
to a 10-mL flask. Then the mixture was stirred at room temper-
ature for 2 h; for synthesis of 4a: 0 ꢀC, 12 h. The solvent was
concentrated under reduced pressure by an aspirator, and then
the residue was purified by preparative TLC using 10:1 petro-
leum/ethyl acetate as an eluent to afford 4a, 4b, 4c, and 4d.
4.10. Characterization data of compounds
4.5. General procedure for one-pot synthesis of
unsymmetrical triarylmethanes 3n, 3o, 3p, 3q, 3r, 3s,
and 3t
4.10.1. 2,20-(Phenylmethylene)bis(1,4-dimethylbenzene)
(3a)
1H NMR (400 MHz, CDCl3) d 7.27e7.23 (m, 2H), 7.20e
7.16 (m, 1H), 7.03e7.02 (m, 4H), 6.94e6.92 (d, J¼7.5 Hz,
2H), 6.54 (s, 2H), 5.63 (s, 1H), 2.18 (s, 6H), 2.11 (s, 6H); 13C
NMR (100 MHz, CDCl3) d 142.9, 141.8, 135.0, 133.5, 130.2,
129.9, 129.9, 128.3, 127.0, 126.1, 50.5, 21.3, 19.2. Calcd for
C23H24: C, 91.95; H, 8.05. Found: C, 91.77; H, 7.83.
Aldehyde (1 mmol), acetic anhydride (2 mmol), electronic-
rich arene (1 mmol), DCM (2 mL), and anhydrous FeCl3
(16.2 mg, 0.1 mmol) were sequentially added to a 10-mL
flask, and the mixture was magnetically stirred at room tem-
perature for 2 h. Then another arene (2 mmol) was added to
the system, and the reaction mixture was stirred at room tem-
perature; for synthesis of 3n: 80 ꢀC. The reaction was moni-
tored by GC until completion. The solvent was concentrated
under reduced pressure by an aspirator, and then the residue
was purified by preparative TLC using 10:1 petroleum/ethyl
acetate as an eluent to afford 3n, 3o, 3p, 3q, 3r, 3s, and 3t.
4.10.2. 2,20-((4-Bromophenyl)methylene)bis(1,4-dimethyl-
benzene) (3b)
1H NMR (400 MHz, CDCl3) d 7.39e7.36 (d, J¼8.4 Hz,
2H), 7.04e7.03 (d, J¼7.6 Hz, 2H), 6.95e6.94 (d, J¼8.6 Hz,
2H), 6.90e6.88 (d, J¼8.3 Hz, 2H), 6.50 (s, 2H), 5.57 (s,
1H), 2.20 (s, 6H), 2.09 (s, 6H); 13C NMR (100 MHz, CDCl3)
d 142.1, 141.1, 135.2, 133.3, 131.5, 131.3, 130.3, 129.7, 127.2,
120.0, 49.9, 21.2, 19.2. Calcd for C23H23Br: C, 72.82; H, 6.11.
Found: C, 72.88; H, 6.25.
4.6. Synthesis of unsymmetrical triarylmethanes 3u
Diphenylmethyl acetate 4d (0.5 mmol), 2,5-dimethylthio-
phene (0.5 mmol), DMC (2 mL), and anhydrous FeCl3
(0.05 mmol) were sequentially added to a 10-mL flask, and
the mixture was magnetically stirred at room temperature
for 2 h. The solvent was concentrated under reduced pressure
by an aspirator, and then the residue was purified by prepara-
tive TLC using 10:1 petroleum/ethyl acetate as an eluent to
afford 3u.
4.10.3. 2,20-((4-Chlorophenyl)methylene)bis(1,4-dimethyl-
benzene) (3c)
1H NMR (400 MHz, CDCl3) d 7.24e7.22 (d, J¼8.3 Hz,
2H), 7.05e7.03 (d, J¼7.6 Hz, 2H), 6.96e6.93 (d, J¼8.3 Hz,
4H), 6.50 (s, 2H), 5.59 (s, 1H), 2.20 (s, 6H), 2.10 (s, 6H); 13C
NMR (100 MHz, CDCl3) d 141.5, 41.2, 135.1, 133.3, 131.9,

1928
Z. Li et al. / Tetrahedron 64 (2008) 1924e1930
131.1, 130.3, 129.7, 128.4, 127.1, 49.8, 21.2, 19.1. Calcd for
C23H23Cl: C, 82.49; H, 6.92. Found: C, 82.68; H, 7.22.
6.79e6.77 (d, J¼8.7 Hz, 2H), 6.69e6.68 (d, J¼2.5 Hz, 2H),
5.99 (s, 1H), 3.67 (s, 6H); 13C NMR (100 MHz, CDCl3)
d 155.7, 141.3, 133.1, 131.4, 130.9, 129.5, 127.6, 125.3, 120.3,
112.0, 55.9, 43.0. Calcd for C21H17BrCl2O2: C, 55.78; H, 3.79.
Found: C, 56.06; H, 4.04.
4.10.4. 2,20-(p-Tolylmethylene)bis(1,4-dimethylbenzene)
(3d)
1H NMR (400 MHz, CDCl3) d 7.06e7.01 (m, 4H), 6.93e
6.89 (m, 4H), 6.55 (s, 2H), 5.58 (s, 1H), 2.31 (s, 3H), 2.18
(s, 6H), 2.10 (s, 6H); 13C NMR (100 MHz, CDCl3) d 142.5,
140.2, 135.9, 135.4, 133.9, 130.6, 130.3, 130.2, 129.4, 127.3,
50.5, 21.7, 21.5, 19.7; MS calcd for C24H26 (MþNa): 337.2,
found: 337.1. Calcd for C24H26: C, 91.67; H, 8.33. Found:
C, 91.43; H, 8.12.
4.10.10. 2,20-(Phenylmethylene)bis(4-chloro-1-methoxy-
benzene) (3j)
1H NMR (400 MHz, CDCl3) d 7.28e7.20 (m, 3H), 7.18e
7.15 (m, 2H), 7.04e7.02 (d, J¼7.1 Hz, 2H), 6.79e6.76 (d,
J¼8.6 Hz, 2H), 6.73e6.72 (d, J¼2.6 Hz, 2H), 6.06 (s, 1H),
3.66 (s, 6H); 13C NMR (100 MHz, CDCl3) d 155.7, 142.0,
133.8, 129.6, 129.2, 128.3, 127.3, 126.4, 125.2, 111.9, 55.9,
43.3. Calcd for C21H18Cl2O2: C, 67.57; H, 4.86. Found: C,
67.72; H, 5.12.
4.10.5. 2,20-((4-Nitrophenyl)methylene)bis(1,4-dimethyl-
benzene) (3e)
1H NMR (400 MHz, CDCl3) d 8.14e8.12 (d, J¼8.6 Hz,
2H), 7.20e7.18 (d, J¼8.6 Hz, 2H), 7.08e7.06 (d, J¼7.6 Hz,
2H), 6.99e6.98 (d, J¼7.3 Hz, 2H), 6.47 (s, 2H), 5.72 (s,
1H), 2.21 (s, 6H), 2.11 (s, 6H); 13C NMR (100 MHz, CDCl3)
d 151.2, 146.6, 140.4, 135.6, 133.5, 130.7, 129.8, 129.0, 127.7,
123.6, 50.4, 21.3, 19.3; HRMS calcd for C23H23NO2 (MþNa):
368.1627, found: 368.1631.
4.10.11. 2,20-((3-Bromophenyl)methylene)bis(1,4-dimethyl-
benzene) (3k)
1H NMR (400 MHz, CDCl3) d 7.35e7.33 (d, J¼7.8 Hz,
1H), 7.18 (s, 1H), 7.14e7.10 (m, 1H), 7.05e7.03 (d, J¼
7.6 Hz, 2H), 6.96e6.92 (m, 3H), 6.50 (s, 2H), 5.59 (s, 1H),
2.20 (s, 6H), 2.10 (s, 6H); 13C NMR (100 MHz, CDCl3)
d 145.6, 141.0, 135.3, 133.4, 132.8, 130.4, 129.9, 129.8,
129.5, 128.5, 127.3, 122.6, 50.2, 21.3, 19.2. Calcd for
C23H23Br: C, 72.82; H, 6.11. Found: C, 72.80; H, 6.26.
4.10.6. 2,20-((4-Bromophenyl)methylene)bis(4-bromo-
1-methoxybenzene) (3f)
1H NMR (400 MHz, CDCl3) d 7.39e7.37 (d, J¼8.4 Hz,
2H), 7.34e7.31 (m, 2H), 6.90e6.88 (d, J¼8.4 Hz, 2H),
6.82e6.81 (d, J¼2.4 Hz, 2H), 6.75e6.72 (d, J¼8.7 Hz, 2H),
5.98 (s, 1H), 3.67 (s, 6H); 13C NMR (100 MHz, CDCl3)
d 156.1, 141.2, 133.5, 132.2, 131.4, 130.9, 130.6, 120.3, 112.7,
112.4, 55.9, 42.9. Calcd for C21H17Br3O2: C, 46.62; H, 3.17.
Found: C, 46.47; H, 3.57.
4.10.12. 2,20-((2-Chlorophenyl)methylene)bis(1,4-dimethyl-
benzene) (3l)
1H NMR (400 MHz, CDCl3) d 7.37e7.35 (m, 1H), 7.18e
7.10 (m, 2H), 7.05e7.04 (d, J¼7.6 Hz, 2H), 6.96e6.94 (d,
J¼7.6 Hz, 2H), 6.85e6.83 (m, 1H), 6.49 (s, 2H), 5.94 (s,
1H), 2.19 (s, 6H), 2.11 (s, 6H); 13C NMR (100 MHz,
CDCl3) d 140.8, 140.3, 135.0, 134.7, 133.6, 131.0, 130.2,
129.6, 129.5, 127.6, 127.2, 126.5, 47.4, 21.3, 19.0. Calcd for
C23H23Cl: C, 82.49; H, 6.92. Found: C, 82.42; H, 7.19.
4.10.7. 2,20-((3-Bromophenyl)methylene)bis(4-chloro-
1-methoxybenzene) (3g)
1H NMR (400 MHz, CDCl3) d 7.36e7.34 (m, 1H), 7.20e
7.17 (m, 3H), 7.15e7.12 (m, 1H), 6.95e6.93 (d, J¼7.6 Hz,
1H), 6.80e6.78 (d, J¼8.7 Hz, 2H), 6.70e6.69 (d, J¼2.6 Hz,
2H), 6.02 (s, 1H), 3.68 (s, 6H); 13C NMR (100 MHz, CDCl3)
d 155.7, 144.7, 132.8, 132.1, 129.8(2C), 129.6, 127.8, 127.7,
125.4, 122.6, 112.0, 55.9, 43.1; HRMS calcd for
C21H17BrCl2O2 (MþNa): 472.9687, found: 472.9692.
4.10.13. 2,20-(Phenylmethylene)bis(1,3,5-trimethylbenzene)
(3m)
1H NMR (400 MHz, CDCl3) d 7.24e7.24 (m, 2H), 7.17 (m,
2H), 6.77 (s, 5H), 5.88 (s, 1H), 2.25 (s, 6H), 1.86 (s, 12H); 13
C
4.10.8. 2,20-((2-Bromophenyl)methylene)bis(4-chloro-
1-methoxybenzene) (3h)
NMR (100 MHz, CDCl3) d 144.3, 137.7, 137.0, 135.4, 130.4,
128.9, 128.2, 125.9, 50.9, 21.5, 20.6. Calcd for C25H28: C,
91.41; H, 8.59. Found: C, 91.25; H, 8.94.
1H NMR (400 MHz, CDCl3) d 7.57e7.55 (m, 1H), 7.21e
7.16 (m, 3H), 7.11e7.07 (m, 1H), 6.83e6.79 (m, 3H),
6.63e6.62 (d, J¼2.6 Hz, 2H), 6.31 (s, 1H), 3.69 (s, 6H); 13C
NMR (100 MHz, CDCl3) d 155.9, 141.8, 133.2, 132.5,
130.2, 129.4, 128.2, 127.7, 127.2, 125.5, 125.3, 112.0, 56.1,
43.6. HRMS calcd for C21H17BrCl2O2 (MþNa): 472.9687,
found: 472.9704.
4.10.14. 2-((5-Bromo-2-methoxyphenyl)(phenyl)methyl)-
1,3,5-trimethylbenzene (3n)
1H NMR (400 MHz, CDCl3) d 7.32e7.29 (m, 1H), 7.22e
7.13 (m, 3H), 6.95e6.91 (m, 3H), 6.79 (s, 2H), 6.75e6.73
(d, J¼8.8 Hz, 1H), 6.07 (s, 1H), 3.64 (s, 3H), 2.24 (s, 3H),
1.94 (s, 6H); 13C NMR (100 MHz, CDCl3) d 157.0, 142.4,
137.4, 136.2, 135.8, 133.1, 132.9, 130.2, 130.0, 128.5, 128.0,
125.6, 112.7, 112.0, 55.8, 45.3, 21.8. 20.8. Calcd for
C23H23BrO: C, 69.88; H, 5.86. Found: C, 69.67; H, 5.69.
4.10.9. 2,20-((4-Bromophenyl)methylene)bis(4-chloro-
1-methoxybenzene) (3i)
1H NMR (400 MHz, CDCl3) d 7.39e7.37 (d, J¼8.4 Hz,
2H), 7.19e7.16 (m, 2H), 6.91e6.89 (d, J¼8.4 Hz, 2H),

Z. Li et al. / Tetrahedron 64 (2008) 1924e1930
1929
4.10.15. 2-(Mesityl(phenyl)methyl)-1,3,5-trimethoxybenzene
(3o)
133.9, 130.9, 130.7, 130.4, 129.9, 129.6, 128.5, 128.1, 118.6,
110.3, 55.7, 45.2, 20.8 (2C), 17.6. Calcd for C25H27BrO: C,
70.92; H, 6.43. Found: C, 71.08; H, 6.52.
1H NMR (400 MHz, CDCl3) d 7.19e7.15 (m, 2H), 7.11e
7.09 (m, 1H), 7.02e7.00 (d, J¼7.6 Hz, 2H), 6.74 (s, 2H),
6.13 (s, 3H), 3.79 (s, 3H), 3.49 (s, 6H), 2.22 (s, 3H), 1.97 (s,
6H); 13C NMR (100 MHz, CDCl3) d 159.8, 159.5, 144.7,
138.2, 137.6, 134.5, 129.6, 128.4, 127.6, 124.9, 112.1, 91.5,
55.7, 55.2, 43.0, 21.3, 20.7. Calcd for C25H28O3: C, 79.75;
H, 7.50. Found: C, 79.47; H, 7.24.
4.10.21. 3-((4-Bromophenyl)(2,5-dimethylphenyl)methyl)-
2,5-dimethylthiophene (3u)
1H NMR (400 MHz, CDCl3) d 7.39e7.36 (m, 2H), 7.04e
7.02 (d, J¼7.6 Hz, 1H), 6.95e6.91 (m, 3H), 6.62 (s, 1H),
6.06 (s, 1H), 5.38 (s, 1H), 2.31 (s, 3H), 2.22 (s, 3H), 2.16 (s,
3H), 2.13 (s, 3H); 13C NMR (100 MHz, CDCl3) d 142.8,
141.6, 137.9, 135.4, 134.8, 133.2, 131.4 (2C), 130.9, 130.3,
129.2, 127.3, 127.2, 120.0, 46.5, 21.3, 19.2, 15.3, 13.0. Calcd
for C21H21BrS: C, 65.45; H, 5.49. Found: C, 65.50; H, 5.46.
4.10.16. 3-(Mesityl(phenyl)methyl)-1H-indole (3p)
1H NMR (400 MHz, CDCl3) d 7.89 (s, 1H), 7.36e7.34 (d,
J¼8.2 Hz, 1H), 7.29e7.27 (d, J¼7.9 Hz, 1H), 7.23e7.19 (m,
3H), 7.17e7.13 (m, 3H), 7.04e7.00 (m, 1H), 6.84 (s, 2H),
6.60e6.59 (m, 1H), 6.10 (s, 1H), 2.28 (s, 3H), 2.06 (s, 6H);
13C NMR (100 MHz, CDCl3) d 143.2, 137.7, 137.2, 136.5,
135.6, 130.0, 128.8, 127.9, 127.8, 125.5, 123.8, 122.0,
119.9, 119.3, 116.8, 111.0, 42.8, 21.6, 20.8; HRMS calcd for
C24H23N [MþNa]: 348.1728, found: 348.1731.
4.10.22. (2,5-Dimethylphenyl)(phenyl)methyl acetate (4a)
1H NMR (400 MHz, CDCl3) d 7.33e7.27 (m, 5H), 7.20 (s,
1H), 7.03 (s, 3H), 2.32 (s, 3H), 2.24 (s, 3H), 2.15 (s, 3H); 13C
NMR (100 MHz, CDCl3) d 170.1, 139.6, 137.8, 135.5, 132.6,
130.6, 128.7, 128.4, 127.8, 127.6, 127.5, 74.3, 21.3, 21.2, 19.0;
HRMS calcd for C17H18O2 (MþNa): 277.1205 found,
277.1212.
4.10.17. 3-((3-Bromophenyl)(mesityl)methyl)-2,5-dimethyl-
furan (3q)
1H NMR (400 MHz, CDCl3) d 7.30e7.28 (m, 1H), 7.24e
7.23 (d, J¼7.9 Hz, 1H), 7.11e7.07 (m, 1H), 7.01e6.99 (m,
1H), 6.83 (s, 2H), 5.57 (s, 1H), 5.54 (s, 1H), 2.26 (s, 3H), 2.18
(s, 3H), 2.05 (s, 3H), 2.05 (s, 6H); 13C NMR (100 MHz,
CDCl3) d 149.3, 146.6, 146.3, 136.8, 136.4, 135.9, 130.9,
130.1, 129.7, 128.7, 126.6, 122.5, 118.5, 107.9, 41.6, 21.7,
20.8, 13.5, 11.9. Calcd for: C, 68.93; H, 6.05. Found: C, 68.60;
H, 6.18.
4.10.23. Mesityl(phenyl)methyl acetate (4b)
1H NMR (400 MHz, CDCl3) d 7.37 (s, 1H), 7.29e7.23 (m,
3H), 7.13e7.11 (d, J¼7.5 Hz, 2H), 6.86 (s, 2H), 2.28 (s, 9H),
2.17 (s, 3H); 13C NMR (100 MHz, CDCl3) d 170.4, 139.7,
137.9, 137.8, 133.0, 129.9, 128.3, 127.1, 125.6, 72.7, 21.2,
21.0, 20.6; HRMS calcd for C18H20O2 (MþNa): 281.1361,
found: 291.1364.
4.10.24. Phenyl(2,3,5,6-tetramethylphenyl)methyl acetate
(4c)
4.10.18. 3-(Mesityl(p-tolyl)methyl)-2,5-dimethylfuran (3r)
1H NMR (400 MHz, CDCl3) d 7.04e7.03 (d, J¼7.2 Hz,
2H), 6.97e6.96 (d, J¼6.7 Hz, 2H), 6.82 (s, 2H), 5.60 (s, 1H),
5.56 (s, 1H), 2.30 (s, 3H), 2.25 (s, 3H), 2.17 (s, 3H), 2.05 (s,
6H), 2.03 (s, 3H); 13C NMR (100 MHz, CDCl3) d 148.8,
146.4, 140.3, 137.3, 137.0, 135.5, 134.9, 130.0, 128.8, 127.9,
119.6, 108.2, 41.5, 21.7, 21.0, 20.8, 13.6, 11.9. Calcd for
C23H26O: C, 86.75; H, 8.23. Found: C, 86.81; H, 7.98.
1H NMR (400 MHz, CDCl3) d 7.52 (s, 1H), 7.31e7.22 (m,
3H), 7.12e7.10 (m, 2H), 6.98 (s, 1H), 2.23 (s, 6H), 2.18 (s,
3H), 2.17 (s, 3H), 2.16 (s, 3H); 13C NMR (100 MHz,
CDCl3) d 170.5, 140.1, 135.7, 134.3, 133.8, 132.0, 128.2,
126.9, 125.6, 73.2, 21.1, 20.5, 16.2. Calcd for: C, 80.82; H,
7.85. Found: C, 80.66; H, 8.09.
4.10.25. (4-Bromophenyl)(2,5-dimethylphenyl)methyl
acetate (4d)
4.10.19. 3-(Mesityl(phenyl)methyl)-2,5-dimethylthiophene
(3s)
1H NMR (400 MHz, CDCl3) d 7.45e7.43 (m, 2H), 7.16e
7.14 (m, 3H), 7.03 (s, 2H), 6.96 (s, 1H), 2.32 (s, 3H), 2.22
(s, 3H), 2.15 (s, 3H); 13C NMR (100 MHz, CDCl3) d 170.0,
138.7, 137.3, 135.7, 132.6, 131.6, 130.7, 129.2, 128.9,
127.5, 121.9, 73.7, 21.3, 21.2, 19.0; HRMS calcd for
C17H17BrO2 (MþNa): 355.0310, found: 355.0312.
1H NMR (400 MHz, CDCl3) d 7.25e7.21 (m, 2H), 7.17e
7.16 (m, 1H), 7.04e7.02 (d, J¼7.6 Hz, 2H), 6.83 (s, 2H),
6.13e6.13 (d, J¼0.6 Hz, 1H), 5.68 (s, 1H), 2.30 (s, 3H),
2.26 (s, 3H), 2.10 (s, 3H), 2.00 (s, 6H); 13C NMR (100 MHz,
CDCl3) d 143.2, 137.3, 137.1, 137.1, 135.6, 134.2, 131.7, 130.0,
128.3, 128.2, 127.7, 125.6, 45.5, 21.7, 20.8, 15.3, 13.2.
Calcd for C22H24S: C, 82.45; H, 7.55. Found: C, 82.06; H, 7.32.
4.10.26. Diacetate (5a)
1H NMR (400 MHz, CDCl3) d 7.68 (s, 1H), 7.52e7.51 (m,
2H), 7.42e7.40 (m, 3H), 2.13 (s, 6H); 13C NMR (100 MHz,
CDCl3) d 168.8, 135.4, 129.8, 128.6, 126.7, 89.7, 20.9.
4.10.20. 3-((4-Bromophenyl)(2-methoxy-5-methylphenyl)-
methyl)-1,2,4,5-tetramethylbenzene (3t)
1H NMR (400 MHz, CDCl3) d 7.27e7.25 (m, 2H), 7.04e
7.04 (m, 1H), 6.93 (s, 1H), 6.84e6.82 (d, J¼8.3 Hz, 1H),
6.77e6.75 (d, J¼8.3 Hz, 2H), 6.74e6.73 (m, 1H), 6.14 (s,
1H), 3.69 (s, 3H), 2.20 (s, 6H), 2.18 (s, 3H), 1.89 (s, 6H);
13C NMR (100 MHz, CDCl3) d 155.7, 143.9, 140.3, 134.1,
Acknowledgements
The authors thank the National Natural Science Foundation
of China (no. 20472074), the Innovation Fund for Outstanding

1930
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