Tris(pentafluorophenyl)borane [B(C6F5) 3]-catalyzed Friedel-Crafts reactions of activated arenes and heteroarenes with α-amidosulfones: The synthesis of unsymmetrical triarylmethanes

Article abstract of DOI:10.1016/j.tet.2011.07.041

Tris(pentafluorophenyl)borane [B(C₆F₅)₃] has found to be an efficient catalyst for Friedel-Crafts reactions between activated arenes or heteroarenes and α-amidosulfones. The products undergo further Friedel-Crafts reaction

Full text of DOI:10.1016/j.tet.2011.07.041

Tetrahedron 67 (2011) 7301e7310
Contents lists available at ScienceDirect
Tetrahedron
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Tris(pentafluorophenyl)borane [B(C6F5)3]-catalyzed FriedeleCrafts reactions
of activated arenes and heteroarenes with
of unsymmetrical triarylmethanes
a-amidosulfones: the synthesis
*
*
Ponnaboina Thirupathi , Lok Nath Neupane, Keun-Hyeung Lee
Bioorganic Chemistry Lab, Department of Chemistry, Inha University, 253-Yunghyun-dong, Nam-gu, Incheon 402-751, South Korea
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 20 June 2011
Received in revised form 13 July 2011
Accepted 14 July 2011
Available online 23 July 2011
Tris(pentafluorophenyl)borane [B(C6F5)3] has found to be an efficient catalyst for FriedeleCrafts reactions
between activated arenes or heteroarenes and
a-amidosulfones. The products undergo further Frie-
deleCrafts reactions with activated heteroarenes leading to the synthesis of unsymmetrical triaryl-
methanes. The present synthetic method displayed significant advantages such as low catalyst loading,
mild reaction conditions, highly regioselective, high yield, and broad applicability to various substrates.
Ó 2011 Elsevier Ltd. All rights reserved.
Keywords:
FriedeleCrafts reactions
Tris(pentafluorophenyl)borane [B(C6F5)3]
a
-Amidosulf-ones
(1-Alkyl-1-aryl)methyl sulfones
Triarylmethanes (TRAMs)
1. Introduction
alkylation of electron-rich arenes or heteroarenes with a-amido-
sulfones using InBr3,7c Amberlyst-157d and FeCl3$6H2O7e as cata-
FriedeleCrafts alkylation reactions have proven to be an ex-
cellent and efficient method for CeC bond formation in organic
transformations.1,2 Generally, these reactions are carried out by
either protic acid or Lewis acid catalyst. The FriedeleCrafts al-
kylation reactions of carbonyl compounds,3 imines,4 epoxides,5
and electron-deficient olefins6 as substrates have been exten-
lysts, respectively.
O
Nu O
X
O
Nu-Y
-X-Y
Lewis acid
R1
R
N
H
R1
R
N
H
R1
R
N
H
sively studied. Recently, the
FriedeleCrafts alkylation reactions as alkylating agents.7 The ap-
plication of -amidosulfones has been explained through the
a-amidosulfones are subjected to
1
3
2
a
Scheme 1. Nucleophilic substitution of a-amidosulfones through N-acyliminium ion (2).
formation of N-acyl iminiumions on treatment with Lewis acid
(Scheme 1).8 Compared with N-alkylimines, N-acylimines and
their corresponding iminiumions are considerably more reactive
toward nucleophiles in the addition reactions. Similarly, the en-
With increasing environmental concern, the new environmen-
tally benign methods have been extensively studied. Thus synthetic
methods should be designed to use substances that exhibit little or
no toxicity to human health and environment.9 In this regard,
tris(pentafluorophenyl)borane [B(C6F5)3] have recently attracted
considerable attention because B(C6F5)3 is remarkably nontoxic,
air-stable, non-conventional, water-tolerant, and thermally stable
Lewis acid.10 Recently, various research groups were engaged in
exploring the potential utility of B(C6F5)3 for various organic
transformations, such as ring-opening of epoxides, aza-Ferrier
glycosylation,11e13 hydrosilylation of imines,14 reduction of alco-
hols with silane,15and hydrogenation of imines.16In this context,
B(C6F5)3 has been utilized to catalyze the regio- and stereoselective
cyclizations of unsaturated alkoxysilanes.17 B(C6F5)3 is also as an
efficient activator for polymethylhydrosiloxane in the reduction of
hanced electrophilic character of N-acyliminium ions of
a-ami-
dosulfones allows their reactions with a variety of nucleophiles.7,8
Petrini et al. have demonstrated that the Montmorillonite K-10
could be an efficient catalyst for the FriedeleCrafts reactions of a-
amidosulfones with indoles for the synthesis of 3-substituted
indoles.7a Reutrakul et al. have reported that the Yb(OTf)3-cata-
lyzed FriedeleCrafts reactions of a-amidosulfones with electron-
rich arenes.7b Kim et al. have developed FriedeleCrafts type
* Corresponding authors. E-mail addresses: pthiruchem2@gmail.com (P. Thir-
upathi), leekh@inha.ac.kr (K.-H. Lee).
0040-4020/$ e see front matter Ó 2011 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2011.07.041

7302
P. Thirupathi et al. / Tetrahedron 67 (2011) 7301e7310
different functional groups.18,19 In this present work, we would
like to report tris(pentafluorophenyl)borane [B(C6F5)3]-catalyzed
FriedeleCrafts alkylation reaction of activated arenes and hetero-
2. Result and discussion
Initially, we screened the reaction conditions for FriedeleCrafts
alkylation of 1,2,4-trimethoxy benzene 4a with N-benzylox-
ycarbonylamino phenyl p-tolylsulfone 5a in the absence and
presence of tris(pentafluorophenyl)borane [B(C6F5)3] (Table 1). In
the absence of catalyst, no product was detected (entry 1). When 4a
is treated with 5a using 1 mol % B(C6F5)3 in dichloromethane, the
FriedeleCrafts product 6a was isolated in 39% yield (entry 2). By
increasing the quantity of the catalyst results to an increased yields
(entries 3e5). Among the various solvents tested, dichloromethane
provided the expected product with high yield (entries 4 and
6e10). Thus, dichloromethane was selected as the solvent of choice.
Interestingly, when 4a was reacted with 5a in presence of 5 mol %
B(C6F5)3 in dichloromethane at 40 ꢀC, the corresponding product 6a
was obtained in an excellent yield (entry 11). The entry 11 was
found to be the best in terms of loading of catalyst, reaction time
and yield. This optimized reaction conditions were applied for the
various substrates in this study.
arenes with a-amidosulfones as an alkylating agent to synthesize
the (1-alkyl-1-aryl)methyl sulfones and triarylmethanes
(TRAMs).7c,e
The synthesis of triarylmethanes (TRAMs) has attracted con-
siderable attention due to their various biological activities.20 These
compounds have been found in widespread applications in syn-
thetic, medicinal, and industrial chemistry.21 The triarylmethyl
derivatives are useful as protective groups,22 photochromic agent-
s,23and dyes.24 The ring-hydroxylated triarylmethanes exhibit an-
titumor and antioxidant activities.24c Different types of methods
have been reported for the synthesis of symmetrical triaryl-
methanes from various substrates.25 The synthesis of un-
symmetrical triarylmethanes is far less explored.20f,26,27 In this
present paper, we also report the B(C6F5)3-catalyzed sequential
FriedeleCrafts alkylation reactions of
a-amidosulfones with dif-
ferent activated arenes leads to the selective synthesis of un-
symmetrical triarylmethanes. The present method displayed
significant advantages, such as low catalyst loading, mild reaction
conditions, highly regioselective, high yield, and broad applicability
to various substrates.
On the basis of the optimized reaction conditions, the reactivity
of various activated and non-activated arenes with N-benzylox-
ycarbonylamino phenyl p-tolylsulfone are investigated for the
FriedeleCrafts reaction (Table 2). The FriedeleCrafts alkylation
Table 1
Optimization of the reaction conditions for FriedeleCrafts reactions of 1,2,4-trimethoxy benzene with N-benzyloxycarbonylamino phenyl p-tolylsulfonea
OCH3
OCH3
NHCbz
H3CO
H3CO
B(C6F5)3
+
Ph
SO Tol-
p
2
CbzNH2
+
SO2Tol-p
Solvent, r. t.
OCH3
4a
OCH3 Ph
6a
5a
Entry
B(C6F5)3 mol %
Solvent
Reaction time (h)
Isolated yieldb (%)
1
2
3
4
5
6
7
8
d
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
CH3CN
1,4-Dioxane
CHCl3
THF
14.0
8.0
6.0
4.0
3.5
8.0
8.0
8.0
8.0
6.0
2.5
NR
39
58
87
89
56
23
42
34
69
91c
1.0
2.5
5.0
10.0
5.0
5.0
5.0
5.0
5.0
5.0
9
10
11
CH3NO2
CH2Cl2
a
Reaction condition: 1,2,4-trimethoxy benzene (1.0 mmol) and N-benzyloxycarbonylamino phenyl p-tolylsulfone (1.0 mmol) are used.
Isolated yield of product after column chromatography.
Reaction was carried out at 40 ꢀC.
b
c
Table 2
a
FriedeleCrafts reactions of various activated and non-activated arenes with N-benzyloxycarbonylamino phenyl p-tolylsulfone catalyzed by B(C6F5)3
SO2Tol-p
SO2Tol-p
B(C6F5)3 (5 mol%)
CbzNH
+
2
Ar-H
4a- k
+
Ph
NHCbz
5a
Ph
Ar
CH2Cl2, 40 o
C
6a- k
Entry
1
AreH
Product
Reaction time (h)
Isolated yieldb (%)
OCH3
p-TolO2S
OCH3
Ph
2.5
91
OCH3
OCH3
OCH3
OCH3
OCH3
OCH3
4a
6a
p-TolO2S
OCH3
OCH3
OCH3
2
Ph
2.5
87
OCH3
4b
6b

P. Thirupathi et al. / Tetrahedron 67 (2011) 7301e7310
7303
Table 2 (continued )
Entry
AreH
Product
Reaction time (h)
Isolated yieldb (%)
p-TolO2S
Ph
OCH3
OCH3
3
2.5
85
H3CO
OCH3
H3CO
OCH3
4c
6c
p-TolO2S
OCH3
OCH3
4
5
6
Ph
3.5
4.0
4.0
77
OCH3
OCH3
OCH3
CH3
6g
4d
6d
6e
p-TolO2S
OCH3
Ph
NR
NR
4e
p-TolO2S
CH3
Ph
4f
6f
p-TolO2S
7
8
6.0
6.0
NR
NR
Ph
4g
4h
p-TolO2S
Cl
Ph
Cl
6h
p-TolO2S
Ph
9
2.5
2.5
78
75
N
H
4i
N
H
6i
6j
p-TolO2S
Ph
10
N
N
CH3
CH3
4j
p-TolO2S
O
O
S
11
2.0
2.0
83
80
CH3
CH3
Ph
4k
4l
CH3
CH3
6k
p-TolO2S
S
12
Ph
6l
a
Reaction condition: Activated or non-activated arenes 4 (1.0 mmol), N-benzyloxycarbonylamino phenyl p-tolylsulfone 5a (1.0 mmol) and B(C6F5)3 (5 mol %) were used.
Isolated yield of product after column chromatography.
b
reactions between the activated trimethoxy benzenes (4a, 4b, or
1e3 (entry 4). Less activated arenes such as anisole 4e and toluene
4f as well as non-activated benzene 4g give no product under the
same reaction condition (entries 5e7). Similarly deactivated arene,
chlorobenzene 4h was also unable to give the corresponding Frie-
deleCrafts product at all (entry 8). The reactions of heteroarenes,
4c) and N-benzyloxycarbonylamino phenyl p-tolylsulfone 5a give
the products in high yield (entries 1e3). However, the 1,3-
dimehtoxy benzene 4d furnishes the product in less yield and the
reaction requires a longer reaction time in comparison with entries

7304
P. Thirupathi et al. / Tetrahedron 67 (2011) 7301e7310
Table 3 (continued)
such as indole 4i and N-methyl indole 4j gave the good yield of
corresponding products (entries 9e10). 2-Methyl furan 4k and
2-methyl thiophene 4l produce the products in 83 and 80% yield,
respectively (entries 11e12). The above results indicate that the
highly activated arenes (activation of CeH bond) are more facile
substrates for the FriedeleCrafts reactions over non-activated or
deactivated arenes (Table 2).
The substitution effect of the arenes on the reaction yield can be
well observed. The substitution of electron-donating group of the
arenes improves reaction with and decreases the completion of
reaction time.
Entry
R in 5
Product (7)
Reaction
time (h)
Isolated
yieldb (%)
6
7f
2.0
2.0
92
90
H3CO
H3CO
5g
5h
7
7g
CH3
The substrate scope of the FriedeleCrafts alkylation reactions of
1,2,4-trimethoxy benzene 4a with various a-amidosulfones 5 has
been examined and the results are summarized in Table 3. The 1,2,4-
trimethoxy benzene 4a reacts with N-benzyloxycarbonylamino 2-
naphthyl p-tolylsulfone 5b to afford the FriedeleCrafts product 7b
in high yield (entry 1). The reactions of p-chloro- 5c, m-chloro- 5d
8
9
7h
7i
2.5
2.0
89
92
H3CO
H3CO
F
5i
5j
and o-chloro a-amidosulfones 5e gave the corresponding products
in 90, 87, and 85% yield, respectively (entries 2e4). o-Chloro isomer
shows slight steric and electronic effects that are responsible for the
longer reaction time and less yield (entry 4). The electron-donating
OCH3
substituent’s attached to the phenyl ring of a-amidosulfones 5fek
H3CO
H3CO
react with 1,2,4-trimethoxy benzene 4a achieve the FriedeleCrafts
product in excellent yield (entries 5e10). The electron-withdrawing
10
7j
2.0
90
substituents like NO2e 5l and CNe 5m in
longer reaction time for the completion of the reaction (entries
11e12). The electron-donating substituent in -amidosulfones en-
a-amidosulfones require
OCH3
5k
a
hance the formation of oxonium ion intermediates compare with
electron-withdrawing substrates. As a result higher yield of the
FriedeleCrafts products were observed (entries 5e10; see the pro-
posed mechanism in Scheme 2). 2-Furyl 5n and 2-thiophenyl 5o
11
12
7k
7l
3.0
3.0
84
86
O2N
NC
5l
containing a-amidosulfones react with 1,2,4-trimethoxy benzene
5m
Table 3
FriedeleCrafts reactions of 1,2,4-trimethoxy benzene with various
catalyzed by B(C6F5)3
a
-amidosulfone
a
O
13
14
15
7m
7n
7o
3.0
3.0
3.0
88
85
83
OCH3
p-TolO2S
OCH3
5n
SO2Tol-p
R
B(C6F5)3 (5 mol%)
CH2Cl2, 40 o
CbzNH2
+
+
S
R
NHCbz
H3CO
C
OCH3
OCH3
4a
OCH3
7a- d
5o
5a- q
Entry
R in 5
Product (7)
Reaction
time (h)
Isolated
5p
yieldb (%)
16
7p
3.0
85
1
2
7a
7b
3.0
88
90
5q
5b
17
7q
3.0
78
2.5
2.5
5r
a-amidosulfone (1.0 mmol), 1,2,4-trimethoxy benzene
Cl
5c
a
Reaction condition:
(1.0 mmol), and B(C6F5)3 (5 mol %) were used.
3
7c
87
b
Isolated yield of product after column chromatography.
Cl
5d
5e
4a to afford the respective products in good yield (entries 13e14).
The reactions of arylalkyl 5p, cyclic aliphatic 5q or acyclic aliphatic
5r a-amidosulfones also result in the FriedeleCrafts products in 83,
4
5
7d
7e
3.0
2.5
85
90
Cl
85, and 78% yield, respectively (entries 15e17).
Table 4 shows the effect of sulfonyl group in a-amidosulfone.
1,2,4-Trimethoxy benzene 4a react with N-benzyloxycarbonylamino
phenyl- 8a or 4-methoxy phenyl phenylsulfone 8b to bring about the
H3C
5f

P. Thirupathi et al. / Tetrahedron 67 (2011) 7301e7310
7305
OCH3
OCH3
OCH3
H3CO
H3CO
R
OCH3
4a
OCH3
D
OCH3
OCH3
OCH3
B(C6F5)3
NHCbz
H3CO
4a
NHCbz
H3CO
NHCbz
B(C6F5)3
OCH3
NHCbzB(C6F5)3
R
-p-TolSO2H
R
SO Tol-
p
2
-TolSO B(C F )
p
H3CO
R
2
6
5 3
-B(C6F5)3
H3CO
R
C
5
A
B
-NH2Cbz
-B(C6F5)3
p-TolSO2H
OCH3
OCH3
B(C6F5)3
H3CO
OCH3
O
H3CO
H3CO
Tol-
p
B(C6F5)3
S
p-TolSO2 B(C6F5)3
1
SO Tol-
p
2
O
R
H3CO
H3CO
F
R
H3CO
R
R=
R1
N
H
R1
6a or 7
4i or 4n
OCH3
E
H3CO
-B(C6F5)3
-p-TolSO2H
R1
1
R
OCH3
H3CO
H3CO
N
H
H3CO
4i or 4n
NH
p-TolSO2 B(C6F5)3
-B(C6F5)3
H3CO
H3CO
R
10
-TolSO H
-p
2
R1
OCH3
G
Scheme 2. Plausible mechanism of B(C6F5)3 catalyzed (a) FriedeleCrafts reaction of activated arene with
arylmethanes from (1-alkyl-1-aryl)methyl p-tolylsulfones 7 (6a or7 to 10).
a-amidosulfone (5 to 6a or 7) and (b) Synthesis of unsymmetrical tri-
Table 4
a
FriedeleCrafts reactions of activated arenes with
a
-amidosulfone catalyzed by B(C6F5)3
SO2Ph
Ar
SO2Ph
B(C6F5)3 (5 mol%)
CbzNH2
+
Ar-H
+
R
CH2Cl2, 40 o
C
R
NHCbz
9a- c
4a and 4m
R (8)
8a: R= C6H5
8b: R= 4-CH3OC6H4
Entry
AreH (4)
Product (9)
Reaction time (h)
Isolated yieldb (%)
OCH3
PhO2S
OCH3
1
8a
2.5
89
OCH3
OCH3
OCH3
OCH3
OCH3
OCH3
4a
9a
PhO2S
OCH3
2
8b
8a
2.5
3.0
91
73
H3CO
OCH3
OCH3
OCH3
4a
9b
PhO2S
H3C
3
N
H
4m
NH
H3C
9c
a
Reaction condition:
Isolated yield of product after column chromatography.
a
-amidosulfone (1.0 mmol), electron-rich aromatic compound (1.0 mmol) and B(C6F5)3 (5 mol %) were used.
b

7306
P. Thirupathi et al. / Tetrahedron 67 (2011) 7301e7310
corresponding FriedeleCrafts product in 89 and 90% yield, re-
spectively (entries and -2). The reaction of N-benzylox-
derivatives generate additional oxonium ion G. Both the oxonium
ions F and G react with indole derivatives 4i or 4n to afford the cor-
responding unsymmetrical triarylmethanes 10 (Scheme 2).
1
ycarbonylamino phenyl phenylsulfone 8a and 2-methylindole 4m
gives 73% yield (entry 3). The substrates 8a or 8b did not provide the
product with considerable different yields in comparison to yields of
the substrate in Tables 2 and 3. The above results suggest that the
sulfonyl moiety does not show great influence on the FriedeleCrafts
alkylation reaction catalyzed by B(C6F5)3.
3. Conclusion
We have demonstrated an extremely facile and efficient Frie-
deleCrafts alkylation reactions of activated arenes and heteroarenes
The synthetic utility of the present method was explored further
for the synthesis of unsymmetrical triarylmethanes 10. The Frie-
deleCrafts alkylation reactions of activated heteroarenes, such as
indole 4i or 5-methoxyindole 4n and (1-alkyl-1-aryl)methyl p-
tolylsulfones 7 in the presence of tris(pentafluorophenyl)borane
[B(C6F5)3] at 40 ꢀC afforded the unsymmetrical triarylmethanes 10
(Table 5). The 4-methoxy-7f, 3-methyl-4-methoxy- 7g, and 3,4-
dimethoxy-7h substituted (1-alkyl-1-aryl)methyl p-tolylsulfones
react with indole 4i or 5-methoxyindole 4n smoothly to give rise to
the corresponding unsymmetrical triarylmethanes 10aef in mod-
erate yield (entries 1e6). The reaction of 4-nitro substituted (1-
alkyl-1-aryl)methyl p-tolylsulfones 7k and indole 4i or 5-
methoxyindole 4n were unable to produce the FriedeleCrafts
products at all (entry 7 and 8). Because, the electron-donating
substituent in (1-alkyl-1-aryl)methyl p-tolylsulfones 7 was more
favor the formation of oxonium ion G intermediates compare with
that of electron-withdrawing substrates. As a result the no reaction
took place in electron-withdrawing substrates (see the proposed
mechanism in Scheme 2).
with
a-amidosulfones using 5 mol % of tris(pentafluorophenyl)
borane [B(C6F5)3]. In addition, the present method utilized further
to synthesis of unsymmetrical triarylmethanes from (1-alkyl-1-
aryl)methyl p-tolylsulfones and heteroarenes. B(C6F5)3-Catalyzed
FriedeleCrafts reactions displayed significant advantages such as
low catalyst loading, easy-to-handle, mild reaction conditions,
highly regioselective, high yield, and broad applicability to various
substrates.
4. Experimental section
4.1. General procedures
In all the cases the 1H NMR spectra were recorded with Varian
Gemini 200 or 400 MHz instrument. Chemical shifts are reported in
parts per million in CDCl3 with tetramethylsilane as an internal
standard. 13C NMR data were collected on Varian Gemini 200 or
400 MHz instrument (50 or 100 MHz). Compounds have been also
identified by HRMS (EI) with Jeol DMX 303.
Table 5
a
Synthesis of unsymmetrical triarylmethanes catalyzed by B(C6F5)3
R1
p-TolO2S
OCH3
R
R1
OCH3
B(C6F5)3 (5 mol%)
CH2Cl2, reflux
R
p-TolSO2H
+
+
N
H
OCH3
HN
OCH3
4i = Ar-H, R1= H
OCH3
7a- d
OCH3
4n = Ar-H, R1= CH3O
10a- d
Entry
AreH (4)
7
Product (10)
Reaction time (h)
Isolated yieldb (%)
1
2
3
4
5
6
7
8
4i
4n
4i
4n
4i
4n
4i
7f
7f
7g
7g
7i
7i
7k
7k
10a
10b
10c
10d
10e
10f
4.5
4.0
4.5
4.5
4.5
4.0
6.0
6.0
53
58
52
55
54
58
NR
NR
10g
10h
4n
a
Reaction condition: (1-alkyl-1-aryl)methyl p-tolylsulfones 7 (1.0 mmol), indole 4i or 5-methoxyindole 4n (1.0 mmol), and B(C6F5)3 (5 mol %) were used.
Isolated yield of product after column chromatography.
b
A plausible mechanism for the FriedeleCrafts alkylation reactions
are shown in Scheme 2. (a) The -amidosulfone on treatment with
4.2. General Procedure for the B(C6F5)3-Catalyzed
FriedeleCrafts alkylation reactions of activated arenes with
amidosulfones
a
a-
tris(pentafluorophenyl)borane [B(C6F5)3] to produce the N-acylimi-
nium ion A through the elimination of p-tolunesulfinic acid. The N-
acyliminium ion A (more electrophilic in nature) react with 1,2,4-
trimethoxy benzene 4a gives the FriedeleCrafts product B. B(C6F5)3
catalyzes the elimination of carbamate from B generating the oxo-
nium ion C. The oxonium ion C undergoes second FriedeleCrafts
reactions with p-tolunesulfinic acid (p-TolSO2H) leading to the for-
mation of product 6a or 7. Along with the desired FriedeleCrafts
product 6a or 7, very small quantity of bis-arene D was also isolated.
The formation of bis-arene D explained by the reversible reaction
between the oxonium ion C and 1,2,4-trimethoxy benzene 5a.8 (b)
The Lewis acid B(C6F5)3 react with (1-alkyl-1-aryl)methyl p-tol-
ylsulfones 7 like E, which facilitate the removal of p-toluenesulfinic
acidfrom7 leadstothesecond oxoniumionF. IfR¼4-methoxyphenyl
To a solution of equimolar quantities of the
a-amidosulfones
(1 mmol) and electron-rich arenes or heteroarenes (1 mmol) in
dichloromethane (4 mL) at room temperature was added B(C6F5)3
(5 mol %) as a solid under a purge of nitrogen. Then the temperature
slowly rises to 40 ꢀC and stirred the reaction mixture for appro-
priate time. The reactions were monitored by TLC. After completion
of the reaction (monitored by TLC), the reaction mixture was di-
luted with dichloromethane (5 mL), washed with water (5 mL), and
followed by brine (5 mL). The organic layers were collected, dried
over Na2SO4 and evaporated in rotavapour. The crude compound
was purified by column chromatography (hexaneseethyl acetate
(3:1)) to afford the corresponding FriedeleCrafts products.

P. Thirupathi et al. / Tetrahedron 67 (2011) 7301e7310
7307
The products were characterized by IR, Mass, 1H and 13C NMR
data that are consistent with literature values. Melting point, IR,
Mass, 1H, and 13C NMR values for new products are given below.7aee
4.2.8. Compound 6l. White solid, mp 180 ꢀC; IR (KBr): nmax 2930,
1485,1310,1136,1080 cmꢁ1; 1H NMR (400 MHz, CDCl3)
: 7.50e7.47
d
(m, 4H), 7.31e7.30 (m, 3H), 7.16 (d, J¼8.0 Hz, 2H), 6.95 (d, J¼3.6 Hz,
1H), 6.22 (dd, J¼3.6, 1.4 Hz, 1H), 5.42 (s, 1H), 2.44 (s, 3H), 2. 73 (s,
4.2.1. Compound 6a. Pale yellow solid, mp 171 ꢀC; IR (KBr): nmax
3H); 13C NMR (50 MHz, CDCl3)
d: 144.5, 141.9, 134.6, 132.9, 131.2,
2941, 1518, 1316, 1138, 1023 cmꢁ1; 1H NMR (400 MHz, CDCl3)
d
: 7.58
129.9, 129.7, 129.2, 129.1, 128.8, 128.5, 125.0, 72.6, 21.6, 15.3; EI (m/
z): [M]þ calcd for C19H18O2S2: 342.0748, found: 342. 1, 187
[Mꢁ155]þ.
(s, 1H), 7.57 (d, J¼8.4 Hz, 2H), 7.50 (d, J¼8.0 Hz, 2H), 7.31e7.29 (m,
3H), 7.14 (d, J¼8.4 Hz, 2H), 6.23 (s, 1H), 5.98 (s, 1H), 3.91 (s, 3H), 3.82
(s, 3H), 3.51 (s, 3H), 2.35 (s, 3H); 13C NMR (50 MHz, CDCl3)
d: 151.6,
149.8, 144.0, 143.0, 135.9, 133.5, 129.9, 128.9, 128.8, 128.5, 128.2,
113.1, 112.9, 96.8, 66.3, 56.5, 56.3, 55.9, 21.5; HRMS-EI (m/z): [M]þ
calcd for C23H24O5S: 412.1344, found: 412.1343.7cee
4.2.9. Compound 7a. White solid, mp 141e142 ꢀC; IR (KBr): nmax
2949, 1518, 1316, 1208, 1146, 1031 cmꢁ1; 1H NMR (400 MHz, CDCl3)
d: 8.03 (s, 1H), 7.81e7.78 (m, 3H), 7.70e7.64 (m, 2H), 7.54 (d,
J¼8.5 Hz, 2H), 7.47e7.45 (m, 2H), 7.14 (d, J¼8.5 Hz, 2H), 6.34 (s, 1H),
4.2.2. Compound 6b. White solid, mp 88e90 ꢀC; IR (KBr): nmax
6.16 (s, 1H), 3.93 (s, 3H), 3.83 (s, 3H), 3.53 (s, 3H), 2.35 (s, 3H); 13C
2949, 1339, 1140, 1069 cmꢁ1; 1H NMR (400 MHz, CDCl3)
d
: 7.82 (d,
NMR (50 MHz, CDCl3) d: 151.7, .149.9,144.0,143.1,136.0, 133.1,132.8,
J¼8.2 Hz, 1H), 7.53e7.49 (m, 4H), 7.29e7.27 (m, 3H), 7.14 (d,
131.0,129.5,129.0,128.8,128.2, 128.1,127.5,127.2,126.3,126.1,113.4,
113.0, 96.9, 66.5, 56.6, 55.9, 21.5; HRMS-EI (m/z): [M]þ calcd for
C27H26O5S: 462.1501, found: 462.1505.7cee
J¼8.5 Hz, 2H), 6.74 (d, J¼8.2 Hz,1H), 5.88 (s,1H), 3.84 (s, 3H), 3.71 (s,
3H), 3.58 (s, 3H), 2.33 (s, 3H); 13C NMR (50 MHz, CDCl3)
d: 153.9,
152.0, 144.2, 135.8, 133.6, 130.1, 129.2, 129.0, 128.6, 128.4, 124.4,
119.5, 107.3, 67.2, 61.0, 60.6, 55.9, 21.6; HRMS-EI (m/z): [M]þ calcd
for C23H24O5S: 412.1344, found: 412.1342.7cee
4.2.10. Compound 7b. White solid, mp 137 ꢀC; IR (KBr): nmax 2941,
1510, 1332, 1216, 1138, 1031 cmꢁ1 1H NMR (400 MHz, CDCl3)
; d:
7.50e7.47 (m, 5H), 7.25 (d, J¼8.5 Hz, 2H), 7.17 (d, J¼8.5 Hz, 2H), 6.29
4.2.3. Compound 6c. White solid, mp 127e128 ꢀC; IR (KBr): nmax
(s, 1H), 5.93 (s, 1H), 3.88 (s, 3H), 3.79 (s, 3H), 3.46 (s, 3H), 2.32 (s,
2937, 1513, 1310, 1143, 1023 cmꢁ1; 1H NMR (400 MHz, CDCl3)
d
: 7.64
3H); 13C NMR (50 MHz, CDCl3)
d: 151.5, 149.9, 144.1, 143.0, 135.5,
(d, J¼8.4 Hz, 2H), 7.50 (d, J¼8.5 Hz, 2H), 7.25e7.39 (m, 3H), 7.17 (d,
134.1, 132.0, 131.2, 128.9, 128.6, 128.5, 112.9, 112.3, 96.7, 65.5, 56.5,
56.1, 55.8, 21.3; HRMS-EI (m/z): [M]þ calcd for C23H23ClO5S:
446.0955, found: 446.0955.7cee
J¼8.4 Hz, 2H), 6.15 (s, 1H), 6.06 (s, 2H), 3.77 (s, 3H), 3.64 (s, 6H), 2.37
(s, 3H); 13C NMR (50 MHz, CDCl3)
d: 161.6, 143.3, 138.2, 134.4, 130.2,
128.8, 128.7, 127.8, 127.5, 104.3, 91.0, 67.7, 55.6, 55.2, 21.5; HRMS-EI
(m/z): [M]þ calcd for C23H24O5S: 412.1344, found: 412.1316.7cee
4.2.11. Compound 7c. White solid, mp 157e158 ꢀC; nmax 2937, 1520,
1307, 12.13, 1143, 1031 cmꢁ1
; d:
1H NMR (400 MHz, CDCl3)
4.2.4. Compound 6d. White solid, mp 110e111 ꢀC; IR (KBr): nmax
7.57e7.54 (m, 5H), 7.32 (s, 2H), 7.22 (d, J¼8.5 Hz, 2H), 6.37 (s, 1H),
2946, 1502, 1293, 1208, 1138, 1031 cmꢁ1; 1H NMR (400 MHz, CDCl3)
5.99 (s, 1H), 3.97 (s, 3H), 3.88 (s, 3H), 3.56 (s, 3H), 2.42 (s, 3H); 13C
d
: 8.00 (d, J¼8.0 Hz, 1H), 7.64 (d, J¼8.5 Hz, 2H), 7.56 (d, J¼8.5 Hz,
NMR (50 MHz, CDCl3) d: 151.6, 150.1, 144.3, 143.1, 135.6, 135.5, 134.3,
2H), 7.36e7.33 (m, 3H), 7.19 (d, J¼8.0 Hz, 2H), 6.62 (d, J¼8.5 Hz, 1H),
130.1, 129.7, 129.1, 128.8, 128.4, 128.0, 112.9, 112.2, 96.7, 65.7, 56.6,
56.3, 55.9, 21.5; HRMS-EI (m/z): [M]þ calcd for C23H23ClO5S:
446.0955, found: 446.0949.7cee
6.32 (s, 1H), 6.03 (s, 1H), 3.82 (s, 3H), 3.54 (s, 3H), 2.40 (s, 3H); 13C
NMR (50 MHz, CDCl3) d: 160.9, 157.9, 144.1, 136.0, 133.7, 130.8,
130.2, 129.0, 128.5, 128.2, 114.3, 104.7, 98.3, 66.4, 55.4, 55.3, 21.6;
HRMS-EI (m/z): [M]þ calcd for C22H22O4S: 382.1239, found:
382.1263.7cee
4.2.12. Compound 7d. White solid, mp 146e147 ꢀC; IR (KBr): nmax
2941, 1510, 1332, 1216, 1138, 1023 cmꢁ1; 1H NMR (400 MHz, CDCl3)
d
: 8.36 (d, J¼8.6 Hz, 1H), 7.64 (d, J¼8.2 Hz, 2H), 7.62 (s, 1H), 7.46 (t,
4.2.5. Compound 6i. Brown solid, mp 52e53 ꢀC; IR (KBr): nmax
J¼8.6 Hz, 1H), 7.41 (d, J¼7.6 Hz, 1H), 7.33 (t, J¼8.6 Hz, 1H), 7.29 (d,
J¼8.2 Hz, 2H), 6.73 (s, 1H), 6.47 (s, 1H), 4.02 (s, 3H), 3.95 (s, 3H), 3.62
3397, 3049, 1456, 1316, 1146, 1085 cmꢁ1; 1H NMR (400 MHz, CDCl3)
d
: 8.63 (d, J¼6.5 Hz, 1H), 7.56 (s, 1H), 7.50e7.40 (m, 5H), 7.23e7.19
(m, 4H), 7.06e6.99 (m, 4H), 5.68 (s, 1H), 2.25 (s, 3H); 13C NMR
(50 MHz, CDCl3) : 144.3, 135.4, 135.1, 133.4, 130.0, 129.2, 129.1,
(s, 3H), 2.49 (s, 3H); 13C NMR (50 MHz, CDCl3)
d: 152.1, 150.0, 144.2,
142.8, 135.7, 135.1, 131.9, 130.4, 129.5, 129.2, 128.9, 128.8, 126.7,
113.4, 111.9, 96.6, 61.9, 56.4, 56.1, 55.7, 21.3; HRMS-EI (m/z): [M]þ
calcd for C23H23ClO5S: 446.0955, found: 446.0955.7cee
d
128.8, 128.3, 126.9, 124.9, 122.2, 119.8, 118.1, 111.5, 106.8, 69.0,
21.4.7a,c,d
4.2.13. Compound 7e. White solid, mp 122e123 ꢀC; IR (KBr): nmax
4.2.6. Compound 6j. Brown solid, mp 137e138 ꢀC; (KBr): nmax
2937, 1520, 1307, 12.13, 1143, 1031 cmꢁ1; 1H NMR (400 MHz, CDCl3)
2958, 1401, 1345, 1073 cmꢁ1
;
1H NMR (400 MHz, CDCl3)
d: 7.61 (s,
d
: 7.57 (s, 1H), 7.51 (d, J¼8.4 Hz, 2H), 7.45 (d, J¼8.0 Hz, 2H), 7.14 (d,
1H), 7.50 (d, J¼7.6 Hz, 2H), 7.48e7.39 (m, 2H), 7.38 (d, J¼7.2 Hz, 1H),
7.26e7.22 (m, 4H), 7.17 (t, J¼7.2 Hz, 1H), 7.08 (d, J¼7.6 Hz, 2H), 7.02
(t, J¼7.2 Hz, 1H), 5.65 (s, 1H), 3.77 (s, 3H), 2.31 (s, 3H); 13C NMR
J¼8.0 Hz, 2H), 7.12 (d, J¼8.4 Hz, 2H), 6.31 (s, 1H), 5.95 (s, 1H), 3.91 (s,
3H), 3.82 (s, 3H), 3.50 (s, 3H), 2.36 (s, 3H), 2.31 (s, 3H); 13C NMR
(50 MHz, CDCl3) d: 151.6, 149.8, 143.9, 143.1, 138.2, 136.1, 129.9,
(50 MHz, CDCl3)
d
: 144.2, 136.4, 135.4, 133.9, 130.1, 129.2, 129.0,
129.3, 129.0, 128.9, 113.3, 113.2, 96.9, 66.1, 56.6, 56.4, 56.0, 21.6, 21.1;
HRMS-EI (m/z): [M]þ calcd for C24H26O5S: 426.1501, found:
426.1511.7cee
128.4, 127.7, 122.0, 119.6, 118.5, 109.4, 105.8, 69.0, 33.1, 21.5; HRMS-
EI (m/z): [M]þ calcd for C23H21NO2S: 375.1293, found: 375.1297.7a,c,d
4.2.7. Compound 6k. White solid, mp 148e149 ꢀC; IR (KBr): nmax
4.2.14. Compound 7f. White solid, mp 143 ꢀC; IR (KBr): nmax 2949,
2944, 1499, 1310, 1143, 1085 cmꢁ1
;
1H NMR (400 MHz, CDCl3)
d:
1510, 1316,1254, 1146, 1031 cmꢁ1; 1H NMR (400 MHz, CDCl3)
d: 7.58
7.48e7.45 (m, 4H), 7.34e7.32 (m, 3H), 7.18 (d, J¼8.4 Hz, 2H), 6.42 (d,
(s, 1H), 7.52e7.48 (m, 4H), 7.14 (d, J¼8.0 Hz, 2H), 6.84 (d, J¼8.6 Hz,
J¼3.0 Hz, 1H), 5.95 (dd, J¼3.0, 1.0 Hz, 1H), 5.33 (s, 1H), 2.39 (s, 3H),
2H), 6.32 (s, 1H), 5.93 (s, 1H), 3.92 (s, 3H), 3.82 (s, 3H), 3.76 (s, 3H),
2.23 (s, 3H); 13C NMR (50 MHz, CDCl3)
d
: 153.2, 144.5, 143.8, 134.8,
3.51 (s, 3H), 2.35 (s, 3H); 13C NMR (50 MHz, CDCl3)
d: 159.6, 151.6,
131.0, 130.4, 129.2, 129.1, 128.9, 128.4, 112.7, 107.0, 71.0, 21.6, 13.5;
HRMS-FAB (m/z): [MꢁH]þ calcd for C19H17O3S: 325.0896, found:
325.0898.
149.8, 144.0, 143.1, 136.0, 131.3, 129.0, 128.8, 125.3, 114.0, 113.3, 113.1,
97.0, 65.8, 56.6, 56.5, 56.0, 55.2, 21.5; HRMS-EI (m/z): [M]þ calcd for
C24H26O6S: 442.1450, found: 442.1460.7bee

7308
P. Thirupathi et al. / Tetrahedron 67 (2011) 7301e7310
4.2.15. Compound 7g. White solid, mp 146e147 ꢀC; IR (KBr): nmax
2930, 1513, 1325, 1143, 1219, 1150, 1023 cmꢁ1 1H NMR (400 MHz,
CDCl3)
4.2.22. Compound 7n. White solid, mp 147 ꢀC; IR (KBr): nmax 2933,
1510, 1324, 1200, 1031 cmꢁ1; 1H NMR (400 MHz, CDCl3)
: 7.47 (d,
J¼8.0 Hz, 2H), 7.44 (s, 1H), 7.26 (d, J¼5.1 Hz, 1H), 7.20 (d, J¼4.4 Hz,
1H), 7.11 (d, J¼8.0 Hz, 2H), 6.95 (dd, J¼5.1, 4.4 Hz, 1H), 6.28 (s, 1H),
6.23 (s, 1H), 3.86 (s, 3H), 3.81 (s, 3H), 3.49 (s, 3H), 2.33 (s, 3H); 13C
;
d
d
: 7.55 (s, 1H), 7.47 (d, J¼8.2 Hz, 2H), 7.37 (d, J¼8.0 Hz, 1H),
7.22 (s,1H), 7.08 (d, J¼8.2 Hz, 2H), 6.71 (d, J¼8.0 Hz,1H), 6.26 (s,1H),
5.86 (s, 1H), 3.87 (s, 3H), 3.76 (s, 3H), 3.73 (s, 3H), 3.44 (s, 3H), 2.29
(s, 3H), 2.12 (s, 3H); 13C NMR (50 MHz, CDCl3)
d
: 157.6, 151.4, 149.6,
NMR (50 MHz, CDCl3) d: 151.6, 150.1, 144.1, 142.9, 134.9, 134.4, 129.4,
143.7, 142.9, 135.9, 132.3, 128. 8, 128.7, 128.3, 126.5, 124.5, 113.2,
113.1, 109.7, 96.8, 65.6, 56.5, 56.2, 55.8, 55.1, 21.3, 16.1; HRMS-EI (m/
z): [M]þ calcd for C25H28O6S: 456.1607, found: 456.1597.7cee
128.9, 128.8, 126.6, 124.5, 113.1, 112.1, 96.6, 62.2, 56.8, 56.3, 55.8,
21.3; HRMS-EI (m/z): [M]þ calcd for C21H22O5S2: 418.0909, found:
418.0915.7c-e
4.2.16. Compound 7h. White solid, mp 131e132 ꢀC; IR (KBr): nmax
4.2.23. Compound 7o. White solid, mp 123e124 ꢀC; IR (KBr): nmax
2944, 1520, 1310, 1213, 1136, 1010 cmꢁ1; 1H NMR (400 MHz, CDCl3)
2933, 1518, 1316, 1209, 1138, 1023 cmꢁ1; 1H NMR (400 MHz, CDCl3)
d
: 7.51 (s, 1H), 7.50 (d, J¼8.0 Hz, 2H), 7.31e7.25 (m, 2H), 7.15 (d,
d
: 7.43 (d, J¼8.5 Hz, 2H), 7.36 (s, 1H), 7.28e7.23 (m, 2H), 7.20e7.13
J¼8.6 Hz, 2H), 6.89 (t, J¼8.4 Hz, 1H), 6.31 (s, 1H), 5.88 (s, 1H), 3.91 (s,
(m, 3H), 7.07 (d, J¼8.5 Hz, 2H), 6.99 (s, 1H), 6.30 (s, 1H), 4.79 (d,
J¼6.5 Hz, 1H), 3.87 (s, 6H), 3.37 (s, 3H), 2.80e2.77 (m, 1H),
2.68e2.43 (m, 1H), 2.42e2.38 (m, 1H), 2.37 (s, 3H); 13C NMR
3H), 3.85 (s, 3H), 3.82 (s, 3H), 3.50 (s, 3H), 2.35 (s, 3H); 13C NMR
(50 MHz, CDCl3) d: 153.1, 151.6, 150.7, 150.0, 147.7, 147.6, 144.2, 143.2,
135.7,129.0,128.8,117.8,117.7,113.1,112.7, 96.9, 65.3, 56.6, 56.4, 56.1,
55.9, 21.5; HRMS-EI (m/z): [M]þ calcd for C24H25FO6S: 460.1356,
found: 460.1344.7cee
(50 MHz, CDCl3) d: 151.9, 149.1, 143.0, 142.3, 139.6, 134.3, 128.0,
127.8, 127.5, 127.5, 127.4, 127.2, 127.1, 125.2, 110.5, 95.5, 65.7, 55.6,
55.0, 54.9, 31.7, 27.9, 20.6; HRMS-EI (m/z): [M]þ calcd for
C25H28O5S: 440.1657, found: 440.1656.7cee
4.2.17. Compound 7i. White solid, mp 186e187 ꢀC; IR (KBr): nmax
2925, 1518, 1308, 1216, 1138, 1023 cmꢁ1; 1H NMR (400 MHz, CDCl3)
4.2.24. Compound 7p. White solid, mp 127e129 ꢀC; IR (KBr): nmax
d
: 7.59 (s, 1H), 7.52 (d, J¼8.6 Hz, 2H), 7.16 (d, J¼8.2 Hz, 2H), 7.14 (d,
2933, 1518, 1308, 1138, 1031 cmꢁ1 1H NMR (400 MHz, CDCl3)
; d:
J¼8.6 Hz, 1H), 7.06 (s, 1H), 6.82 (d, J¼8.2 Hz,1H), 6.35 (s, 1H), 5.92 (s,
7.39e7.30 (m, 3H), 7.16 (s, 1H), 7.04 (d, J¼8.8 Hz, 2H), 6.12 (s, 1H),
4.69 (d, J¼6.5 Hz, 1H), 3.89 (s, 3H), 3.78 (s, 3H), 3.35 (s, 3H),
2.52e2.48 (m, 2H), 2.42e2.38 (m, 2H), 2.30 (s, 3H), 1.80e1.76 (m,
1H), 1.70e1.63 (m, 1H), 1.39e1.14 (m, 3H), 1.00e0.95 (m, 1H); 13C
1H), 3.92 (s, 3H), 3.85 (s, 3H), 3.83 (s, 3H), 3.82 (s, 3H), 3.53 (s, 3H),
2.36 (s, 3H); 13C NMR (50 MHz, CDCl3)
d: 151.7, 149.9, 149.1, 148.7,
144.0, 143.1, 136.0, 129.0, 128.9, 125.6, 122.6, 113.2, 113.1, 111.0, 97.1,
66.0, 56.6, 56.4, 56.0, 55.8 (x2) 21.5; EI (m/z): [M]þ calcd for
C25H28O7S: 472.1556, found: 472.1, 317 [Mꢁ155]þ.7cee
NMR (50 MHz, CDCl3) d: 152.3, 149.5, 143.2, 143.0, 136.9, 128.4,
128.3, 128.1,128.0, 112.6, 112.5, 96.3, 66.8, 66.1, 56.6, 56.0, 55.9, 38.2,
32.0, 30.6, 26.1, 25.9, 21.4; HRMS-EI (m/z): [M]þ calcd for
C23H30O5S: 418.1814, found: 418.1797.7cee
4.2.18. Compound 7j. White solid, mp 156 ꢀC; IR (KBr): nmax 2949,
1518, 1316, 1213, 1130, 1023 cmꢁ1; 1H NMR (400 MHz, CDCl3)
d: 7.55
(s,1H), 7.49 (d, J¼8.0 Hz, 2H), 7.13 (d, J¼8.4 Hz, 2H), 6.77 (s,1H), 6.29
4.2.25. Compound 7q. White solid, mp 78e79 ꢀC; IR (KBr): nmax
(s, 1H), 5.87 (s, 1H), 3.88 (s, 3H), 3.80 (s, 3H), 3.78 (s, 9H), 3.47 (s,
2951, 1448, 1347, 1213, 1136, 1023 cmꢁ1; 1H NMR (400 MHz, CDCl3)
3H), 2.33 (s, 3H); 13C NMR (50 MHz, CDCl3)
d
: 153.0, 151.7, 150.0,
d
: 7.37e7.29 (m, 3H), 7.11 (s, 1H), 7.00 (d, J¼7.4 Hz, 2H), 6.10 (s, 1H),
144.1, 143.1, 135.9, 129.0, 128.9, 128.8, 113.2, 112.7, 107.3, 96.9, 66.2,
60.8, 56.6, 56.3, 56.0, 56.0, 21.5; HRMS-EI (m/z): [M]þ calcd for
C26H30O8S: 502.1661, found: 502.1661.7cee
3.84 (s, 3H), 3.75 (s, 3H), 3.32 (s, 3H), 2.77e2.74 (m,1H), 2.27 (s, 3H),
1.26 (d, J¼6.5 Hz, 3H), 0.89 (d, J¼6.5 Hz, 3H); 13C NMR (50 MHz,
CDCl3) d: 152.2, 149.5, 143.2, 142.9, 136.7, 128.4, 128.3, 128.1, 112.5,
96.2, 66.7, 56.5, 55.9, 55.8, 28.7, 21.4, 21.3, 20.9; HRMS-EI (m/z):
4.2.19. Compound 7k. Yellow solid, mp 148 ꢀC; IR (KBr): nmax 2941,
[M]þ calcd for C20H26O5S: 378.1501, found: 378.1508.7cee
1525, 1347, 1223, 1138, 1031 cmꢁ1 1H NMR (400 MHz, CDCl3)
; d:
8.09 (d, J¼8.6 Hz, 2H), 7.73 (d, J¼8.2 Hz, 2H), 7.46 (d, J¼8.6 Hz, 2H),
7.43 (s, 1H), 7. 11 (d, J¼8.2 Hz, 2H), 6.28 (s, 1H), 6.04 (s, 1H), 3.84 (s,
3H), 3.76 (s, 3H), 3.44 (s, 3H), 2.30 (s, 3H); 13C NMR (50 MHz, CDCl3)
4.2.26. Compound 9a. White solid, IR (KBr): nmax 2949, 1518, 1316,
1208, 1146, 1031 cmꢁ1 1H NMR (400 MHz, CDCl3)
; d: 7.63 (d,
J¼8.6 Hz, 2H), 7.58e7.56 (m, 3H), 7.48 (t, J¼8.6 Hz, 2H), 7.37e6.29
d: 151.5, 150.2, 147.2, 144.5, 142.9, 140.8, 135.0, 130.7, 129.0, 128.5,
(m, 4H), 6.29 (s, 1H), 6.00 (s, 1H), 3.91 (s, 3H), 3.81 (s, 3H), 3.47 (s,
123.3, 112.6, 111.2, 96.5, 65.5, 56.4, 56.0, 55.7, 21.3; HRMS-EI (m/z):
3H); 13C NMR (50 MHz, CDCl3)
d: 151.6, 149.9, 143.1, 138.8, 133.3,
[M]þ calcd for C23H23NO7S: 457.1195, found: 457.1189.7cee
133.1, 129.9, 128.8, 128.5, 128.3, 113.2, 112.7, 96.7, 66.2, 56.6, 56.2,
55.9.7bee
4.2.20. Compound 7l. Yellow solid, mp 138e139 ꢀC; IR (KBr): nmax
2941, 2210, 1518, 1316, 1138, 1023 cmꢁ1; 1H NMR (400 MHz, CDCl3,
4.2.27. Compound 9b. White solid, IR (KBr): nmax 2933, 1518, 1308,
25 ꢀC)
d
: 7.65 (d, J¼8.4 Hz, 2H), 7.56 (d, J¼8.4 Hz, 2H), 7.46 (d,
1200, 1146, 1031 cmꢁ1 1H NMR (400 MHz, CDCl3)
; d: 7.61 (d,
J¼8.0 Hz, 2H), 7.44 (s,1H), 7.13 (d, J¼8.4 Hz, 2H), 6.27 (s,1H), 5.96 (s,
J¼8.3 Hz, 2H), 7.55 (s, 1H), 7.49e7.46 (m, 3H), 7.32 (m, 2H), 6.83 (d,
1H), 3.86 (s, 3H), 3.79 (s, 3H), 3.46 (s, 3H), 2.33 (s, 3H); 13C NMR
J¼8.3 Hz, 2H), 6.28 (s, 1H), 5.95 (s, 1H), 3.90 (s, 3H), 3.79 (s, 3H), 3.74
(50 MHz, CDCl3, 25 ꢀC)
d
: 151.6, 150.3, 144.5, 143.1, 138.9, 135.3,
(s, 3H), 3.46 (s, 3H); 13C NMR (50 MHz, CDCl3)
d: 159.6, 151.6, 149.9,
132.1, 130.6, 129.1, 128.7, 118.3, 112.8, 111.9, 111.5, 96.7, 66.9, 56.6,
143.1, 138.9, 133.2, 131.3, 128.8128.4, 125.1, 114.0.113.2, 113.0, 96.9,
56.1, 55.9, 21.5; EI (m/z): [M]þ 437, 283, 282, 266.7cee
65.8, 56.7, 56.4, 56.0, 55.2.7cee
4.2.21. Compound 7m. White solid, mp 172e173 ꢀC; IR (KBr): nmax
4.2.28. Compound 9c. Brown solid, 169 ꢀC; (KBr): nmax 3384, 3064,
2949, 1518, 1301, 1208, 1138, 1015 cmꢁ1; 1H NMR (400 MHz, CDCl3)
1450, 1297, 1143, 1080 cmꢁ1; 1H NMR (400 MHz, CDCl3)
d: 7.98 (br s,
d
: 7.48 (d, J¼8.0 Hz, 2H), 7.42 (s, 2H), 7.17 (d, J¼8.0 Hz, 2H), 6.53 (d,
1H), 7.81e7.73 (m, 3H), 7.55e7.52 (m, 3H), 7.43e7.41 (m, 1H),
J¼3.4 Hz, 1H), 6.37e6.36 (m, 1H), 6.34 (s, 1H), 6.12 (s, 1H), 3.87 (s,
7.32e7.23 (m, 5H), 7.22e7.02 (m, 2H), 5.66 (s, 1H), 2.12 (s, 3H); 13C
3H), 3.85 (s, 3H), 3.55 (s, 3H), 2.38 (s, 3H); 13C NMR (50 MHz, CDCl3)
NMR (50 MHz, CDCl3) d: 138.8, 135.5, 135.1, 133.2, 132.8, 129.9,
d
: 151.9, 150.4, 146.2, 144.2, 143.4, 143.3, 135.2, 129.1, 129.0, 114.0,
128.6, 128.5, 128.4, 128.2, 127.1, 121.5, 121.1, 120.1, 110.4, 103.9, 69.6,
11.8; HRMS-EI (m/z): [M]þ calcd for C22H19NO2S: 361.1136, found:
361.1136.7aec
111.8, 110.8, 110.4, 96.7, 61.3, 56.5, 56.4, 56.0, 21.6; HRMS-EI (m/z):
[M]þ calcd for C21H22O6S: 402.1137, found: 402.1141.7cee

P. Thirupathi et al. / Tetrahedron 67 (2011) 7301e7310
7309
4.3. Experimental procedure for the synthesis of
unsymmetrical triarylmethanes
6.73 (d, J¼8.4 Hz, 1H), 6.68 (dd, J¼8.4, 1.8 Hz, 1H), 6.59 (s, 1H), 6.55
(s, 1H), 6.54 (d, J¼1.5 Hz, 1H), 5.94 (s, 1H), 3.86 (s, 3H), 3.81 (s, 3H),
3.73 (s, 3H), 3.71 (s, 3H), 3.56 (s, 3H); 13C NMR (100 MHz, CDCl3,
The B(C6F5)3 (5 mol %) was added to a solution of (1-alkyl-1-
aryl)methyl p-tolylsulfone (1 mmol) and heteroaromatic indole
derivatives in dichloromethane (4 mL) under nitrogen atmosphere.
The resulting solution was refluxed with constant stirring for
4.0e6.0 h. The progress of the reaction was monitored by TLC. After
completion of the reaction, the reaction mixture was diluted with
water (5 mL), and extracted with dichloromethane (3ꢂ5 mL). The
combined organic layer was washed with water (5 mL), saturated
aqueous NaCl (5 mL), dried over anhydrous Na2SO4, and concen-
trated under vacuum. The crude product was subject to column
chromatography (silica gel, hexaneeEtOAc (3:1)) to obtain pure
product.
25 ꢀC)
d: 151.2, 148.5, 148.0, 147.1, 136.8, 136.7, 127.0, 124.4, 123.7,
121.8, 120.6, 119.9, 119.1, 114.3, 112.4, 111.0, 110.7, 98.1, 56.9, 56.6,
56.0, 55.7, 40.3; HRMS-EI (m/z): [M]þ calcd for C26H27NO5:
433.1889, found: 433.1902.7e
4.3.6. Compound 10f. White solid, mp 175e177 ꢀC; (KBr): nmax
3356, 2930, 1506, 1206, 1032 cmꢁ1 1H NMR (400 MHz, CDCl3)
; d:
7.96 (br s, 1H), 7.19 (d, J¼8.8 Hz, 1H), 6.81 (s, 1H), 6.70 (d, J¼2.0 Hz,
1H), 6.75 (d, J¼8.4 Hz, 1H), 6.74 (d, J¼1.8 Hz, 1H), 6.69 (d, J¼8.8 Hz,
1H), 6.68 (d, J¼2.0 Hz,1H), 6.62 (s, 1H), 6.56 (s, 1H), 5.91 (s, 1H), 3.86
(s, 3H), 3.84 (s, 3H), 3.75 (s, 3H), 3.73 (s, 3H), 3.69 (s, 3H), 3.59 (s,
3H); 13C NMR (50 MHz, CDCl3)
d: 153.5, 151.2, 148.5, 147.9, 147.1,
The products were characterized by IR, Mass, 1H, and 13C NMR
data that are consistent with literature values.7c,e
142.8, 136.7, 131.9, 127.5, 124.5, 120.6, 119.6, 114.3, 112.4, 111.7, 110.7,
102.0, 98.1, 57.0, 56.6, 56.0, 55.7, 40.3; HRMS-EI (m/z): [M]þ calcd
for C27H29NO6: 463.1995, found: 463.1995.7e
4.3.1. Compound 10a. White solid, mp 179e180 ꢀC; (KBr): nmax
3342, 2930, 1560, 1213, 1038 cmꢁ1 1H NMR (400 MHz, CDCl3,
;
Acknowledgements
25 ꢀC)
d
: 7.96 (br s, 1H), 7.31 (d, J¼8.2 Hz, 1H), 7.25 (d, J¼8.2 Hz, 1H),
7.13 (d, J¼8.6 Hz, 3H), 6.99 (t, J¼8.4 Hz, 1H), 6.80 (d, J¼8.2 Hz, 2H),
Authors thank the Department of Chemistry, Inha University.
This work was supported by grant of Inha University in Korea.
6.61 (s, 1H), 6.58 (d, J¼8.6 Hz, 2H), 5.98 (s, 1H), 3.89 (s, 3H), 3.78 (s,
13
3H), 3.74 (s, 3H), 3.59 (s, 3H); C NMR (100 MHz, CDCl3, 25 ꢀC)
d:
157.7, 151.2, 147.9, 142.9, 136.8, 136.4, 129.7, 127.1, 124.7, 123.8, 121.9,
120.2, 120.1, 119.2, 114.3, 113.4, 111.0, 98.2, 57.0, 56.6, 56.1, 55.2,
40.0; HRMS-EI (m/z): [M]þ calcd for C25H25NO4: 403.1784, found:
403.1786.7c,e
References and notes
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4.3.2. Compound 10b. White solid, mp 150e152 ꢀC; (KBr): nmax
3335, 2930, 1513, 1206, 1048 cmꢁ1 1H NMR (400 MHz, CDCl3,
;
25 ꢀC)
d
: 7.98 (br s, 1H), 7.22 (d, J¼8.5 Hz, 1H), 7.18 (d, J¼8.5 Hz, 2H),
6.86e6.84 (m, 3H), 6.71 (d, J¼1.5 Hz, 1H), 6.67 (s, 1H), 6.62 (s, 1H),
6.58 (d, J¼1.5 Hz, 1H), 5.96 (s, 1H), 3.92 (s, 3H), 3.81 (s, 3H), 3.76 (s,
13
3H), 3.72 (s, 3H), 3.64 (s, 3H); C NMR (100 MHz, CDCl3, 25 ꢀC)
d:
157.6, 153.5, 151.2, 147.9, 142.8, 136.2, 131.9, 129.6, 127.4, 124.5, 119.6,
114.3,113.3,111.7,111.5, 98.2, 56.9, 56.7, 56.0, 55.7, 55.1, 40.0; HRMS-
EI (m/z): [M]þ calcd for C26H27NO5: 433.1889, found: 433.1885.7e
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4.3.3. Compound 10c. White solid, mp 170 ꢀC; (KBr): nmax 3370,
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; d:
8.09 (br s, 1H), 7.32 (d, J¼7.6 Hz, 1H), 7.30 (d, J¼7.6 Hz, 1H), 7.17 (t,
J¼7.6 Hz, 1H), 7.11 (s, 1H), 7.06e7.00 (m, 2H), 6.75 (d, J¼8.0 Hz, 1H),
6.72 (s,1H), 6.64 (s,1H), 6.58 (s,1H), 6.03 (s,1H), 3.92 (s, 3H), 3.82 (s,
3H), 3.78 (s, 3H), 3.64 (s, 3H), 2.23 (s, 3H); 13C NMR (100 MHz,
CDCl3, 25 ꢀC)
d: 155.8, 151.1, 147.8, 142.7, 136.6, 135.7, 131.1, 126.9,
126.7, 125.8, 124.8, 123.7, 121.6, 119.9, 119.8, 118.5, 114.4, 111.0, 109.3,
98.1, 56.8, 56.5, 55.9, 55.1, 39.8, 16.2; HRMS-EI (m/z): [M]þ calcd for
C26H27NO4: 417.1940, found: 417.1942.7e
4.3.4. Compound 10d. White solid, mp 172.9 ꢀC; (KBr): nmax 3340,
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2935, 1508, 1213, 1048 cmꢁ1 1H NMR (400 MHz, CDCl3, 25 ꢀC)
; d:
7.97 (br s, 1H), 7.17 (d, J¼8.8 Hz, 1H), 7.05 (d, J¼2.0 Hz, 1H), 6.99 (dd,
J¼8.4, 2.0 Hz, 1H), 6.81 (dd, J¼8.4, 2.0 Hz, 1H), 7.72 (d, J¼8.8 Hz, 1H),
7.71 (s, 1H), 6.67 (s, 1H), 6.59 (s, 1H), 6.56 (d, J¼2.0 Hz, 1H), 5.92 (s,
1H), 3.89 (s, 3H), 3.80 (s, 3H), 3.75 (s, 3H), 3.70 (s, 3H), 3.62 (s, 3H),
2.18 (s, 3H); 13C NMR (100 MHz, CDCl3, 25 ꢀC)
d: 155.8, 151.1, 147.8,
142.7, 136.6, 135.7, 131.1, 126.9, 126.7, 125.8, 124.8, 123.7, 121.6, 119.9,
119.8, 118.5, 114.4, 111.0, 109.3, 98.1, 56.8, 56.5, 55.9, 55.1, 39.8, 16.2;
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447.2050.7e
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3356, 2930, 1506, 1206, 1032 cmꢁ1 1H NMR (400 MHz, CDCl3,
;
25 ꢀC)
7.11 (t, J¼8.5 Hz, 1H), 6.94 (t, J¼8.5 Hz, 1H), 6.79 (d, J¼2.0 Hz, 1H),
d
: 8.02 (br s, 1H), 7.27 (d, J¼8.0 Hz, 1H), 7.22 (d, J¼8.0 Hz, 1H),
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