FeCl3: an efficient catalyst for reactions of electron-rich arenes with imines or aziridines

Article abstract of DOI:10.1016/j.tet.2008.03.081

Iron(III) chloride was discovered highly effective as catalyst in the Friedel-Crafts reactions of electron-rich arenes with imines or aziridines. It was found that reactions of imines were highly substrate-dependent, which generated mono- or double-additi

Full text of DOI:10.1016/j.tet.2008.03.081

Tetrahedron 64 (2008) 5013–5018
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FeCl3: an efficient catalyst for reactions of electron-rich arenes
with imines or aziridines
,b,
Zhiyong Wang a, Xiaoyu Sun a, Jie Wu a
*
a Department of Chemistry, Fudan University, 220 Handan Road, Shanghai 200433, China
b State Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, 354 Fenglin Road, Shanghai 200032, China
a r t i c l e i n f o
a b s t r a c t
Article history:
Iron(III) chloride was discovered highly effective as catalyst in the Friedel–Crafts reactions of electron-
rich arenes with imines or aziridines. It was found that reactions of imines were highly substrate-
dependent, which generated mono- or double-addition products, while arenes reacted with aziridines
regioselectively leading to the formation of desired ring-opening products in 2 min with moderate to
good yields.
Received 5 December 2007
Received in revised form 21 March 2008
Accepted 25 March 2008
Available online 28 March 2008
Ó 2008 Elsevier Ltd. All rights reserved.
Keywords:
Iron(III) chloride
Friedel–Crafts reaction
Arene
Imine
Aziridine
1. Introduction
arenes to a-imino esters by using a combination of gold and silver
catalysts. Since iron salts are inexpensive and environmentally
Recently, iron salts have attracted the attention of synthetic
organic chemists since iron is one of the most abundant metals on
earth, consequently one of the most inexpensive and environ-
mentally friendly ones, and many iron salts and complexes are
commercially available.1 These iron salts have been found to show
promising catalytic abilities in many organic transformations,
including Friedel–Crafts reactions.1f Friedel–Crafts reactions of
various arenes, especially electron-rich arenes, are a well-known
process for the formation of new C–C bonds from aromatic C–H
bonds.2 Herein, we would like to disclose our recent efforts for
FeCl3-catalyzed Friedel–Crafts reactions of electron-rich arenes
with imines or aziridines.
friendly ones as described above, the feasibility on FeCl3-catalyzed
Friedel–Crafts reactions of electron-rich arenes with imines was
then examined using 1,3,5-trimethoxybenzene 1a and imine 2a as
the model substrates (Scheme 1). Iron chloride (5 mol %) was ini-
tially applied for the reaction. To our delight, the desired product 3a
was generated with 72% isolated yield when the reaction was
performed in CH3NO2 (Scheme 1, Eq. 1). This result provided a good
example for the mono aza-Friedel–Crafts reactions of imine.8 In-
ferior results were displayed when other solvents were utilized in
the reaction. Imine 2b was also employed in the reaction of 1,3,5-
trimethoxybenzene 1a, which afforded the corresponding product
3b in 52% yield. However, to our surprise, when 1,2-dimethoxy-
benzene 1b was used in the reaction of imine 2a or 2b under the
iron(III)-catalyzed conditions, symmetrical triaryl methane 4a or
4b was generated via a double Friedel–Crafts reaction. This result
was similar to those of previous reports,9,10 since aromatic alde-
hydes9 and their imines,3c,10 generally evolve according to a double
Friedel–Crafts reaction to give symmetric triaryl methanes due
to the intrinsic instability of the intermediate benzylic alcohol
or amine derivative under the acidic reaction conditions. Other
electron-rich arenes were also employed in the FeCl3-catalyzed
reactions of imines 2, and low yields (<15%) of symmetrical triaryl
methanes were afforded (data not shown in Scheme 1). Due to the
similar activities between imines and aziridines, we then shifted
our focus to aziridines for this FeCl3-catalyzed Friedel–Crafts
reaction of electron-rich arenes.
2. Results and discussion
Usually, the mono Friedel–Crafts reaction of carbonyl com-
pounds and imines seems to be restricted to highly electrophilic
substrates such as glyoxylates,3 chloral,4 pyruvates,5 tri-
fluoromethyl imines,6 or a-imino esters.3c,7 Among these, expen-
sive or heavy metal catalysts have to be utilized. For example, Li7b
reported an imino Friedel–Crafts type addition of electron-rich
* Corresponding author. Tel.: þ86 21 5566 4619; fax: þ86 21 6510 2412.
E-mail address: jie_wu@fudan.edu.cn (J. Wu).
0040-4020/$ – see front matter Ó 2008 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2008.03.081

5014
Z. Wang et al. / Tetrahedron 64 (2008) 5013–5018
OMe
MeO
OMe
+
FeCl3 (5 mol%)
CH3NO2, r.t.
12 h
NTs
R3
(1)
MeO
R1
OMe
NHTs
OMe
2a: R3 = H
1a
2b: R3 = 4-F
3a: R3 = H, 72% yield;
3b: R3 = 4-F, 52% yield.
OMe
OMe
OMe
OMe
FeCl3 (5 mol%)
CH3NO2, r.t.
NTs
R3
+
(2)
OMe
OMe
R1
12 h
2a: R3 = H
1b
2b: R3 = 4-F
4a: R3 = H, 20% yield;
4b: R3 = 4-F, 21% yield.
Scheme 1.
Aziridine is a versatile building block for the synthesis of many
nitrogen-containing biologically active molecules.11 Among the
procedures of ring opening of aziridines, a nucleophilic ring-
opening reaction is one of the major routes to highly functionalized
compounds.11 Although ring-opening reactions of aziridines with
various nucleophiles (such as thiols, amines, alcohols, and silylated
nucleophiles) have been developed, there are only few examples of
utilizing arenes as substrates, which employed Lewis acids [AlCl3,12
BF3$OEt2,13 In(OTf)3,14 AuCl3,15 and AgPF616] as the promoter or
catalyst. For example, stoichiometric amount of AlCl3 or BF3$OEt2
had to be utilized as a promoter for reactions of aziridines with
arenes.12,13 Indium triflate was also employed for the reaction of
aziridines with arenes.14 The reaction was usually completed in
several hours in the presence of catalytic amount of In(OTf)3 (5–
10 mol %) and afforded the product as mixture of regioisomers in
most cases. Prompted by these results and our efforts for aziridine
transformation,15 we envisaged that aziridine might also be
employed as substrate in the iron(III)-catalyzed reaction of arenes,
due to the unique activity of iron catalyst for functionalization of
arenes.8
1,2-dimethoxybenzene 1b (1.1 equiv) in CH3NO2 at room temper-
ature (Table 1, entry 1). This reaction was found highly efficient,
which was finished in 2 min, and the desired product 6b was
afforded in 90% yield. Furthermore, under this catalytic condition,
regiospecificity was observed and the only isomer, which was from
attack on the benzylic position of N-tosyl-2-phenylaziridine 5a was
obtained. Even in the analysis of 1H NMR spectra of crude mixture,
we still could not find the peak of isomer. It may be due to electron
effect since the benzylic position of N-tosyl-2-arylaziridine is highly
positive. When CH3NO2 was replaced by other solvents, lower
yields were observed. For instance, 27% yield or 25% of product 6b
was obtained, respectively, when the reaction was performed in
CH2Cl2 or ClCH2CH2Cl (Table 1, entries 2 and 3). Only trace amount
of product was detected when THF was employed as the solvent
(Table 1, entry 4). The reaction was retarded when 1 mol % of FeCl3
was utilized in the reaction (12 h, 48% yield, Table 1, entry 5). It is
presumably due to the fact that the resulting amine product might
act as a Lewis base to deactivate or inhibit the iron(III) catalyst.
Moreover, it is noteworthy that the product, which could be easily
generated from attacking of aziridine 5a by chloride, was not ob-
served during the reaction process. Other iron salts with different
forms were also screened in the reaction of aziridine 5a with arene
Initial studies were performed by using FeCl3 (5 mol %) as
catalyst in the reaction of N-tosyl-2-phenylaziridine 5a with
Table 1
Reaction of aziridine 5a and arene 1b catalyzed by iron salt at room temperaturea
OMe
OMe
Ts
OMe
N
OMe
OMe
OMe
[Fe]
NHTs
+
+
NHTs
1b
5a
6b
6b'
Entry
Iron salt
Solvent
Time
Yielda (%)
1
2
3
4
5
6
7
8
FeCl3 (5 mol %)
FeCl3 (5 mol %)
FeCl3 (5 mol %)
FeCl3 (5 mol %)
FeCl3 (1 mol %)
Fe(acac)3 (5 mol %)
Fe(OAc)2 (5 mol %)
Fe2(SO4)3 (5 mol %)
CH3NO2
CH2Cl2
(CH2Cl)2
THF
CH3NO2
CH3NO2
CH3NO2
CH3NO2
CH3NO2
CH3NO2
CH3NO2
2 min
2 h
2 h
2 h
12 min
1 h
1 h
2 h
5 min
12 h
5 min
90 (6b)
27 (6b)
25 (6b)
Trace
48 (6b)
NR
NR
40 (6b)
58 (6b)
50 (6b/6b0: 3/1)b
57 (6b)
9
10
11
FeCl3$6H2O (5 mol %)
Fe(NO3)3$9H2O (5 mol %)
NH4Fe(SO4)2$12H2O (5 mol %)
a
Isolated yield based on aziridine 5a.
b
The ratio was determined by 1H NMR.

Z. Wang et al. / Tetrahedron 64 (2008) 5013–5018
5015
Table 2 (continued)
1b (Table 1, entries 6–11). Anhydrous FeCl3 was demonstrated to be
the most effective catalyst in the reaction. We observed the gen-
eration of regioisomer 6b0 when Fe(NO3)3$9H2O (5 mol %) was
employed in the reaction (Table 1, entry 10). Again, the major
product comes from the attack of arene on the benzylic position of
aziridine 5a.
Entry
Aziridine
Arene
Product
Yieldb
(%)
OMe
6
5a
6f
77
1f
To test the effectiveness of the iron(III) chloride catalytic system,
a range of N-tosyl-2-arylaziridines and arenes was examined using
the preliminary optimized reaction conditions (CH3NO2 as the
solvent, 5 mol % of FeCl3, room temperature) and the results are
summarized in Table 2. Although reactions of electron-rich arenes
proceeded well under the conditions, electron-deficient arenes
were not good substrates for this kind of transformation. When
chlorobenzene 1i or trifluoromethylbenzene 1j was employed as
substrate in the reaction of aziridine 5a catalyzed by FeCl3 (5 mol %)
(Table 2, entries 9 and 10), complicated reaction mixture was
afforded although aziridine 5a disappeared after 5 min. Again,
under the catalytic conditions only one isomer was generated for
this regiospecific ring-opening reaction of aziridines with all elec-
tron-rich arenes. The reactions were highly efficient, and we found
that these conditions allowed us to perform a broad range of re-
actions of electron-rich arenes with aziridines within 2 min. Thus,
aziridine 5a reacted with 1,3,5-trimethoxybenzene 1a or o-xylene
1c to give the desired product 6a or 6c in 61% or 82% yield, re-
spectively (Table 2, entries 1 and 3). Similarly, the reaction of
aziridine 5a with benzo[d][1,3]dioxole 1d furnished the expected
product 6d in 77% yield (Table 2, entry 4). Reaction of 1,4-dime-
thoxybenzene 1e or anisole 1f with aziridine 5a provided the cor-
responding product 6e or 6f in 60% or 77% yield (Table 2, entries 5
and 6). Heterocycle, such as furan 1h reacted smoothly with azir-
idine 5a leading to the desired product 6g in 56% yield (Table 2,
entry 8) under these conditions. However, no reaction occurred
when N,N-dimethylbenzenamine 1g was utilized in the reaction
(Table 2, entry 7). Other aziridines, such as 5b, 5c, and 5d, were all
good substrates for the FeCl3-catalyzed ring-opening reactions with
NMe2
7
5a
6g
NR
1g
O
8
9
5a
5a
6h
6i
56
1h
Cl
d
1i
CF3
10
11
12
13
5a
6j
d
1j
NTs
OMe
6k
6l
77
80
52
OMe 1b
Cl
5b
O
5b
1d
O
OMe
5b
6m
MeO
1e
NTs
OMe
OMe 1b
O
14
6n
75
5c
15
16
5c
5c
6o
6p
81
50
1d
O
OMe
Table 2
Reaction of aziridine 5 and arene 1 catalyzed by FeCl3 (5 mol %) in CH3NO2 at room
temperaturea
MeO
MeO
1e
R1
OMe
Ts
NTs
N
FeCl3 (5 mol%)
17
18
6q
64
R1
+
NHTs
R2
CH3NO2, r.t.
R2
F
5d
OMe
1a
< 2 min
1
5
6
OMe
5d
6r
6s
75
71
Entry
Aziridine
Arene
Product
Yieldb
OMe 1b
(%)
MeO
OMe
O
NTs
19
5d
1
2
6a
6b
61
1d
O
5a
a
OMe
1a
Reaction conditions: aziridine 1 (0.5 mmol), arene 2 (0.6 mmol, 1.2 equiv), FeCl3
(5 mol %), CH3NO2 (2.0 mL), rt, <2 min.
b
OMe
Isolated yield based on aziridine 1.
5a
90
OMe 1b
electron-rich arenes, which afforded the expected product in
moderate to good yields (Table 2, entries 11–19).
3
4
5a
5a
6c
82
77
Moreover, we tested other aziridines under the conditions
shown in Table 2. For instance, aziridine 5e reacted with 1,2-
dimethoxybenzene 1b leading to the formation of regioisomers 6t
and 6t0 in 70% yield (Scheme 2, Eq. 1). When N-tosyl group was
replaced by N-nosyl group, the reaction also proceeded smoothly to
afford the desired product in good yield (Scheme 2, Eq. 2). However,
no product was detected when aziridine 7a or 7b was utilized as
substrate in the reaction of 1,2-dimethoxybenzene 1b, and only
starting material was recovered after 12 h at room temperature
1c
O
6d
1d
O
OMe
5
5a
6e
60
MeO
1e
(continued)

5016
Z. Wang et al. / Tetrahedron 64 (2008) 5013–5018
OMe
to use in the reactions. Other commercial reagents were used
OMe
as-received.
4.1.1. General procedure for reaction of electron-rich arene 1
with imine 2 catalyzed by FeCl3 (5 mol %) in CH3NO2
at room temperature
Under nitrogen atmosphere, imine 2 (0.50 mmol) and arene 1
(0.60 mmol) were added subsequently to a solution of iron(III)
chloride (5 mol %) in anhydrous nitromethane (2.5 mL) at room
temperature. After completion of the reaction as indicated by TLC,
the reaction mixture was quenched with water (10 mL) and
extracted with EtOAc (2ꢀ10 mL). Evaporation of the solvent fol-
lowed by purification on silica gel afforded pure product 3 or 4.
NHTs
Ts
OMe
N
OMe
6t
FeCl3 (5 mol%)
(1)
(2)
+
+
CH3NO2, r.t.
< 2 min
OMe
OMe
1b
5e
NHTs
70% yield
6t/6t': 78/22
6t'
OMe
OMe
Ns
OMe
OMe
N
4.1.1.1. 4-Methyl-N-(phenyl(2,4,6-trimethoxyphenyl)methyl)-benz-
enesulfonamide (3a).7b 1H NMR (400 MHz, CDCl3) 2.30 (s, 3H), 3.61
(s, 6H), 3.74 (s, 3H), 5.88 (s, 2H), 6.10 (d, J¼11.0 Hz, 1H), 6.22 (d,
J¼11.0 Hz, 1H), 7.00 (d, J¼8.2 Hz, 2H), 7.12–7.24 (m, 5H), 7.50 (d,
J¼7.8 Hz, 2H). 13C NMR (100 MHz, CDCl3) 21.2, 51.4, 55.2, 55.5, 90.5,
108.6,126.3,126.4,126.7,127.8,128.5,137.4,141.2,142.3,157.7,160.8.
IR (KBr): 3308, 2929,1593,1444,1332,1152, 814 cmꢁ1. MS (ESI): m/z
428.0 (Mþþ1).
FeCl3 (5 mol%)
CH3NO2, r.t.
< 2 min
+
Ph
NHNs
1b
5f
Ph
78% yield
6u
Scheme 2.
7a
NTs
4.1.1.2. N-((4-Fluorophenyl)(2,4,6-trimethoxyphenyl)methyl)-4-meth-
ylbenzenesulfonamide (3b). 1H NMR (400 MHz, CDCl3) 2.30 (s, 3H),
3.62 (s, 6H), 3.74 (s, 3H), 5.88 (s, 2H), 6.05 (d, J¼11.0 Hz, 1H), 6.21 (d,
J¼11.0 Hz, 1H), 6.85–6.92 (m, 2H), 7.00 (d, J¼7.7 Hz, 2H), 7.18–7.21
(m, 2H), 7.49 (d, J¼7.8 Hz, 2H). 13C NMR (100 MHz, CDCl3) 21.3,
50.9, 55.2, 55.5, 90.5, 108.5, 114.4, 114.6, 126.7, 127.9, 128.0, 128.6,
137.4, 142.4, 157.7, 160.9. IR (KBr): 3308, 2919, 1588, 1449, 1337,
1157, 814 cmꢁ1. MS (ESI): m/z 446.0 (Mþþ1). Anal. Calcd for
Ts
OMe
OMe
FeCl3 (5 mol%)
N
+
No Reaction
7b
7c
C4H9
Ph
CH3NO2, r.t., 12 h
Bn
1b
N
Scheme 3.
C23H24FNO5S: C, 62.01; H, 5.43; N, 3.14. Found: C, 62.04; H, 5.45;
N, 3.01.
(Scheme 3). We also examined the reaction of 1,2-dimethoxy-
benzene 1b with aziridine without tosyl group attached on the
nitrogen. No reaction occurred when 1-benzyl-2-phenyl aziridine
7c was employed in the reaction. These results were similar to the
previous reports.12–16
4.1.1.3. 4-((3,4-Dimethoxyphenyl)(phenyl)methyl)-1,2-dimethoxy-
benzene (4a).17 1H NMR (400 MHz, CDCl3) 3.75 (s, 6H), 3.85 (s, 6H),
5.44 (s, 1H), 6.58–6.60 (m, 2H), 6.66 (s, 2H), 6.78 (d, J¼8.2 Hz, 2H),
7.11 (d, J¼8.2 Hz, 2H), 7.25–7.28 (m, 3H). 13C NMR (100 MHz, CDCl3)
55.7, 55.8, 110.7, 112.6, 121.3, 126.2, 128.2, 129.2, 136.6, 147.3, 148.6.
IR (KBr): 2919, 1516, 1460, 1260, 1132, 814 cmꢁ1. MS (ESI): m/z 365.0
(Mþþ1).
3. Conclusion
In summary, we have described iron(III) chloride as a highly
effective catalyst for Friedel–Crafts reactions of electron-rich arenes
with imines or aziridines. This catalyst shows high efficiency in
regiospecific ring-opening reaction of aziridines with electron-rich
arenes, which provides a facile and convenient route for the syn-
thesis of b-aryl amines. We also found that it could promote the
addition reactions of imines with arenes to afford the mono- or
double-addition products. The advantages of this method include:
(1) high efficiency and excellent regioselectivity (less than 2 min);
(2) experimentally operational ease; and (3) mild conditions.
Efforts to explore synthetic utilities of the reactions reported here
are in progress in our laboratory.
4.1.1.4. 4-((3,4-Dimethoxyphenyl)(4-fluorophenyl)methyl)-1,2-di-
methoxybenzene (4b). 1H NMR (400 MHz, CDCl3) 3.76 (s, 6H), 3.85
(s, 6H), 5.41 (s, 1H), 6.51–6.58 (m, 2H), 6.64 (d, J¼1.8 Hz, 2H), 6.78
(d, J¼8.7 Hz, 2H), 6.78–7.10 (m, 4H). 13C NMR (100 MHz, CDCl3) 55.7,
55.8, 110.8, 112.5, 114.9, 115.1, 121.2, 130.6, 130.7, 136.4, 147.5, 148.7.
IR (KBr): 2921, 1510, 1463, 1263, 1138, 817 cmꢁ1. MS (ESI): m/z 383.0
(Mþþ1). Anal. Calcd for C23H23FO4: C, 72.24; H, 6.06. Found: C,
72.04; H, 6.25.
4.1.2. General procedure for reaction of electron-rich arene 1
with aziridine 5 catalyzed by FeCl3 (5 mol %) in CH3NO2
at room temperature
Under nitrogen atmosphere, aziridine 5 (0.50 mmol) and arene
1 (0.60 mmol) were added subsequently to a solution of iron(III)
chloride (5 mol %) in anhydrous nitromethane (2.5 mL) at room
temperature. After completion of the reaction as indicated by
TLC (less than 2 min), the reaction mixture was quenched with
water (10 mL) and extracted with EtOAc (2ꢀ10 mL). Evaporation of
the solvent followed by purification on silica gel afforded pure
product 6.
4. Experimental section
4.1. General
All reactions were performed in test tubes under nitrogen
atmosphere. Flash column chromatography was performed using
silica gel (60-Å pore size, 32–63 mm, standard grade). Analytical
thin-layer chromatography was performed using glass plates
pre-coated with 0.25 mm 230–400 mesh silica gel impregnated
with a fluorescent indicator (254 nm). Aziridines were prepared
according to literature methods.11 Solvents were re-distilled prior
4.1.2.1. 4-Methyl-N-(2-phenyl-2-(2,4,6-trimethoxyphenyl)ethyl)benz-
enesulfonamide (6a). 1H NMR (400 MHz, CDCl3) 2.42 (s, 3H), 3.61 (s,
6H), 3.69–3.71 (m, 2H), 3.78 (s, 3H), 4.38 (m, 1H), 4.65 (m, 1H), 6.04

Z. Wang et al. / Tetrahedron 64 (2008) 5013–5018
5017
(s, 2H), 7.13–7.25 (m, 7H), 7.64 (d, J¼8.2 Hz, 2H). 13C NMR (100 MHz,
CDCl3) 21.4, 39.6, 45.2, 55.2, 55.4, 91.0, 108.8, 125.9, 127.0, 127.6,
127.9, 129.4, 137.0, 141.8, 142.8, 159.2, 160.3. IR (KBr): 3288, 2939,
2837, 1609, 1325, 1152, 809 cmꢁ1. MS (ESI): m/z 442.0 (Mþþ1). Anal.
Calcd for C24H27NO5S: C, 65.28; H, 6.16; N, 3.17. Found: C, 65.40; H,
6.05; N, 3.01.
21.5, 45.2, 46.6, 107.0, 110.2, 127.1, 127.5, 127.9, 128.9, 129.7, 136.9,
138.7, 142.0, 143.5, 154.0. IR (KBr): 3298, 2919, 1597, 1321, 1155,
1086, 816 cmꢁ1. MS (ESI): m/z 342.0 (Mþþ1).
4.1.2.9. N-(2-(4-Chlorophenyl)-2-(3,4-dimethoxyphenyl)ethyl)-4-meth-
ylbenzenesulfonamide (6k).14 1H NMR (400 MHz, CDCl3) 2.42 (s,
3H), 3.42–3.49 (m, 2H), 3.74 (s, 3H), 3.79 (s, 3H), 4.00 (t, J¼7.8 Hz,
1H), 4.96 (t, J¼6.4 Hz, 1H), 6.55 (d, J¼2.0 Hz, 1H), 6.62 (d, J¼
8.3 Hz, 1H), 6.74 (d, J¼8.3 Hz, 1H), 7.03 (d, J¼8.8 Hz, 2H), 7.17 (d,
J¼8.3 Hz, 2H), 7.23 (d, J¼8.3 Hz, 2H), 7.62 (d, J¼8.3 Hz, 2H). 13C NMR
(100 MHz, CDCl3) 21.4, 47.1, 49.4, 55.6, 55.7, 111.1, 111.2, 119.6, 126.8,
128.6, 129.0, 129.6, 132.5, 132.7, 136.5, 139.7, 143.4, 147.9, 149.0. IR
(KBr): 3291, 2932, 1516, 1318, 1151, 1090, 817 cmꢁ1. MS (ESI): m/z
446.0 (Mþþ1).
4.1.2.2. N-(2-(3,4-Dimethoxyphenyl)-2-phenylethyl)-4-methylbenz-
enesulfonamide (6b).14 1H NMR (400 MHz, CDCl3) 2.41 (s, 3H),
3.45–3.53 (m, 2H), 3.74 (s, 3H), 3.81 (s, 3H), 4.02 (t, J¼7.8 Hz, 1H),
4.65 (t, J¼5.9 Hz, 1H), 6.58 (s, 1H), 6.65 (d, J¼8.3 Hz, 1H), 6.74 (d,
J¼8.3 Hz, 1H), 7.09 (d, J¼7.3 Hz, 2H), 7.18–7.27 (m, 5H), 7.65 (d,
J¼8.3 Hz, 2H). 13C NMR (100 MHz, CDCl3) 21.3, 47.3, 50.0, 55.7, 55.8,
111.2, 111.3, 119.7, 126.9, 127.0, 127.7, 128.7, 129.6, 133.0, 136.7, 141.0,
143.4, 148.0, 149.1. IR (KBr): 3265, 2935, 1593, 1324, 1152, 804 cmꢁ1
.
MS (ESI): m/z 412.0 (Mþþ1).
4.1.2.10. N-(2-(Benzo[d][1,3]dioxol-5-yl)-2-(4-chlorophenyl)ethyl)-
4-methylbenzenesulfonamide (6l).14 1H NMR (400 MHz, CDCl3) 2.42
(s, 3H), 3.38–3.48 (m, 2H), 3.96 (t, J¼7.8 Hz, 1H), 4.82 (t, J¼6.4 Hz,
1H), 5.87 (s, 2H), 6.48 (d, J¼1.5 Hz, 1H), 6.54 (d, J¼8.3 Hz, 1H), 6.66
(d, J¼7.8 Hz, 1H), 7.0 (d, J¼8.3 Hz, 2H), 7.17 (d, J¼8.3 Hz, 2H), 7.25 (d,
J¼7.8 Hz, 2H), 7.63 (d, J¼8.3 Hz, 2H). 13C NMR (100 MHz, CDCl3)
21.5, 47.1, 49.6, 101.0, 108.1, 108.4, 120.9, 127.0, 128.8, 129.1, 129.7,
132.7, 134.1, 136.5, 139.5, 143.5, 146.6, 148.0. IR (KBr): 3279, 2878,
1593, 1489, 1320, 1153, 1096, 817 cmꢁ1. MS (ESI): m/z 430.0 (Mþþ1).
4.1.2.3. N-(2-(3,4-Dimethoxyphenyl)-1-phenylethyl)-4-methylbenz-
enesulfonamide (6b0).14 1H NMR (400 MHz, CDCl3) 2.40 (s, 3H),
2.93–3.28 (m, 2H), 3.87 (s, 3H), 3.90 (s, 3H), 4.72 (m, 1H), 4.96 (m,
1H), 6.84 (s, 1H), 6.95–7.03 (m, 2H), 7.19–7.34 (m, 5H), 7.60–7.63 (m,
2H), 7.72 (d, J¼8.2 Hz, 2H). IR (KBr): 3265, 2935, 1593, 1324, 1152,
804 cmꢁ1. MS (ESI): m/z 412.0 (Mþþ1).
4.1.2.4. N-(2-(3,4-Dimethylphenyl)-2-phenylethyl)-4-methylbenz-
enesulfonamide (6c).14 1H NMR (400 MHz, CDCl3) 2.16 (s, 3H), 2.18
(s, 3H), 2.41 (s, 3H), 3.45–3.54 (m, 2H), 3.98 (t, J¼7.8 Hz, 1H), 4.52 (t,
J¼5.8 Hz, 1H), 6.78–6.84 (m, 2H), 6.98–7.27 (m, 8H), 7.65 (d,
J¼8.0 Hz, 2H). 13C NMR (100 MHz, CDCl3) 19.4, 19.9, 21.7, 47.4, 50.2,
125.3, 127.1, 127.3, 127.9, 128.9, 129.4, 129.8, 130.2, 135.6, 136.9,
137.2, 138.1, 141.2, 143.6. IR (KBr): 3277, 2919, 1598, 1328, 1159, 1091,
817 cmꢁ1. MS (ESI): m/z 380.0 (Mþþ1).
4.1.2.11. N-(2-(4-Chlorophenyl)-2-(2,5-dimethoxyphenyl)ethyl)-4-
methylbenzenesulfonamide (6m).14 1H NMR (400 MHz, CDCl3) 2.43
(s, 3H), 3.44–3.52 (m, 2H), 3.67 (s, 3H), 3.68 (s, 3H), 4.42 (t, J¼7.8 Hz,
1H), 4.50 (t, J¼5.9 Hz, 1H), 6.48 (d, J¼2.9 Hz, 1H), 6.69–6.76 (m, 2H),
7.04 (d, J¼8.3 Hz, 2H), 7.18 (d, J¼8.3 Hz, 2H), 7.25 (d, J¼8.3 Hz, 2H),
7.63 (d, J¼8.3 Hz, 2H). 13C NMR (100 MHz, CDCl3) 21.4, 43.2, 46.1,
55.6, 55.9, 111.7, 111.8, 114.8, 127.1, 128.6, 129.4, 129.6, 129.8, 132.6,
136.7, 139.1, 143.4, 151.2, 153.6. IR (KBr): 3255, 2943, 1589, 1497,
1329, 1162, 1092, 817 cmꢁ1. MS (ESI): m/z 446.0 (Mþþ1).
4.1.2.5. N-(2-(Benzo[d][1,3]dioxol-5-yl)-2-phenylethyl)-4-methylbenz-
enesulfonamide (6d).14 1H NMR (400 MHz, CDCl3) 2.41 (s, 3H),
3.41–3.51 (m, 2H), 3.97 (t, J¼7.8 Hz, 1H), 4.70 (br, 1H), 5.84 (s,
2H), 6.51–6.57 (m, 2H), 6.65 (d, J¼7.8 Hz, 1H), 7.06 (d, J¼7.3 Hz, 2H),
7.15–7.26 (m, 5H), 7.65 (d, J¼8.3 Hz, 2H). 13C NMR (100 MHz, CDCl3)
21.5, 47.2, 50.1, 100.9, 108.2, 108.3, 120.9, 126.9, 127.0, 127.6, 128.7,
129.6, 134.5, 136.6, 140.8, 143.4, 146.4, 147.9. IR (KBr): 3277, 2914,
1599, 1325, 1147, 1091, 819 cmꢁ1. MS (ESI): m/z 396.0 (Mþþ1).
4.1.2.12. N-(2-(3,4-Dimethoxyphenyl)-2-p-tolylethyl)-4-methylbenz-
enesulfonamide (6n).14 1H NMR (400 MHz, CDCl3) 2.27 (s, 3H), 2.40
(s, 3H), 3.43–3.49 (m, 2H), 3.74 (s, 3H), 3.79 (s, 3H), 3.98 (t, J¼7.8 Hz,
1H), 4.68 (t, J¼5.8 Hz,1H), 6.59 (s,1H), 6.64 (d, J¼7.8 Hz,1H), 6.73 (d,
J¼8.3 Hz, 1H), 6.97 (d, J¼7.8 Hz, 2H), 7.04 (d, J¼7.8 Hz, 2H), 7.25 (d,
J¼8.3 Hz, 2H), 7.64 (d, J¼8.3 Hz, 2H).13C NMR (100 MHz, CDCl3) 20.9,
21.4, 47.3, 49.6, 55.6, 55.7, 111.1, 111.2, 119.6,127.0, 127.5,129.3,129.6,
133.3, 136.5, 136.6, 137.9, 143.3, 147.8, 149.0. IR (KBr): 3294, 2929,
1593, 1514, 1331, 1155, 1086, 810 cmꢁ1. MS (ESI): m/z 426.0 (Mþþ1).
4.1.2.6. N-(2-(2,4-Dimethoxyphenyl)-2-phenylethyl)-4-methylbenz-
enesulfonamide (6e).14 1H NMR (400 MHz, CDCl3) 2.41 (s, 3H), 3.44–
3.55 (m, 2H), 3.65 (s, 3H), 3.67 (s, 3H), 4.46 (t, J¼7.8 Hz, 1H), 4.56 (t,
J¼5.9 Hz, 1H), 6.51 (d, J¼3.0 Hz, 1H), 6.66–6.75 (m, 2H), 7.09 (d,
J¼6.9 Hz, 2H), 7.15–7.27 (m, 5H), 7.64 (d, J¼7.8 Hz, 2H). 13C NMR
(100 MHz, CDCl3) 21.5, 43.5, 46.2, 55.4, 55.9,111.5, 111.7,114.9,126.8,
127.0, 128.0, 128.5, 129.5, 130.3, 136.7, 140.3, 143.2, 151.2, 153.5. IR
(KBr): 3293, 2934, 1597, 1495, 1328, 1159, 1052, 813 cmꢁ1. MS (ESI):
m/z 412.0 (Mþþ1).
4.1.2.13. N-(2-(Benzo[d][1,3]dioxol-5-yl)-2-p-tolylethyl)-4-methyl-
benzenesulfonamide (6o). 1H NMR (400 MHz, CDCl3) 2.29 (s, 3H),
2.44 (s, 3H), 3.45–3.47 (m, 2H), 3.92 (t, J¼7.8 Hz, 1H), 4.28 (t,
J¼5.8 Hz, 1H), 5.90 (s, 2H), 6.51–6.53 (m, 2H), 6.69 (d, J¼7.8 Hz, 1H),
6.95 (d, J¼8.2 Hz, 2H), 7.04 (d, J¼8.2 Hz, 2H), 7.30 (d, J¼8.2 Hz, 2H),
7.68 (d, J¼8.2 Hz, 2H). 13C NMR (100 MHz, CDCl3) 20.9, 21.5, 47.2,
49.7, 101.0, 108.1, 108.3, 120.8, 127.0, 127.5, 129.4. 129.6, 134.7, 136.6,
136.7, 137.7, 143.4, 146.4, 147.9. IR (KBr): 3288, 2914, 1588, 1490,
1321, 1147, 1086, 815 cmꢁ1. MS (ESI): m/z 410.0 (Mþþ1). Anal. Calcd
for C23H23NO4S: C, 67.46; H, 5.66; N, 3.42. Found: C, 67.35; H, 5.81;
N, 3.53.
4.1.2.7. N-(2-(4-Methoxyphenyl)-2-phenylethyl)-4-methylbenzene-
sulfonamide (6f).14 1H NMR (400 MHz, CDCl3) 2.43 (s, 3H), 3.46–
3.52 (m, 2H), 3.75 (s, 3H), 4.0 (t, J¼7.8 Hz, 1H), 4.43 (t, J¼5.8 Hz, 1H),
6.78 (d, J¼8.3 Hz, 2H), 7.0 (d, J¼8.8 Hz, 2H), 7.07 (d, J¼6.8 Hz, 2H),
7.18–7.29 (m, 5H), 7.66 (d, J¼7.8 Hz, 2H). 13C NMR (100 MHz, CDCl3)
21.5, 47.3, 49.7, 55.2, 114.2, 126.9, 127.1, 127.8, 128.8, 128.9, 129.7,
132.6, 136.7, 141.1, 143.5, 158.5. IR (KBr): 3277, 2926, 1610, 1512,
1326, 1156, 818 cmꢁ1. MS (ESI): m/z 382.0 (Mþþ1).
4.1.2.14. N-(2-(2,5-Dimethoxyphenyl)-2-p-tolylethyl)-4-methylbenz-
enesulfonamide (6p).14 1H NMR (400 MHz, CDCl3) 2.28 (s, 3H), 2.43
(s, 3H), 3.43–3.53 (m, 2H), 3.66 (s, 3H), 3.68 (s, 3H), 4.12 (t, J¼7.8 Hz,
1H), 4.48 (s, 1H), 6.49 (d, J¼2.9 Hz, 1H), 6.66–6.74 (m, 2H), 6.98 (d,
J¼8.3 Hz, 2H), 7.04 (d, J¼7.8 Hz, 2H), 7.25 (d, J¼7.8 Hz, 2H), 7.64 (d,
J¼7.8 Hz, 2H). 13C NMR (100 MHz, CDCl3) 20.9, 21.5, 43.1, 46.3, 55.5,
55.9, 111.4, 111.7, 114.9, 127.1, 128.0, 129.3, 129.6, 130.5, 136.5, 136.8,
137.2, 143.2, 151.3, 153.6. IR (KBr): 3288, 2929, 1593, 1495, 1321,
1158, 1086, 819 cmꢁ1. MS (ESI): m/z 426.0 (Mþþ1).
4.1.2.8. N-(2-(Furan-2-yl)-2-phenylethyl)-4-methylbenzenesulfona-
mide (6h).18 1H NMR (400 MHz, CDCl3) 2.43 (s, 3H), 3.37–3.43 (m,
1H), 3.54–3.61 (m, 1H), 4.09 (t, J¼7.6 Hz, 1H), 4.51 (t, J¼6.4 Hz, 1H),
6.00 (d, J¼2.8 Hz, 1H), 6.27 (d, J¼3.2 Hz, 1H), 7.11 (d, J¼6.4 Hz, 2H),
7.24–7.31 (m, 6H), 7.68 (d, J¼8.4 Hz, 2H). 13C NMR (100 MHz, CDCl3)

5018
Z. Wang et al. / Tetrahedron 64 (2008) 5013–5018
4.1.2.15. N-(2-(4-Fluorophenyl)-2-(2,4,6-trimethoxyphenyl)ethyl)-
4-methylbenzenesulfonamide (6q). 1H NMR (400 MHz, CDCl3) 2.42
(s, 3H), 3.61 (s, 6H), 3.65–3.71 (m, 2H), 3.78 (s, 3H), 4.39–4.41 (m,
1H), 4.62 (d, J¼8.3 Hz, 1H), 6.04 (s, 2H), 6.85 (d, J¼8.7 Hz, 2H), 7.08–
7.11 (m, 2H), 7.25 (d, J¼7.8 Hz, 2H), 7.64 (d, J¼7.8 Hz, 2H). 13C NMR
(100 MHz, CDCl3) 21.4, 38.9, 45.2, 55.2, 55.4, 90.9, 108.6, 114.5, 114.7,
127.0, 129.1, 129.2, 129.4, 136.9, 137.4, 142.9, 159.0, 160.3. IR (KBr):
3334, 2939, 2841, 1604, 1329, 1157, 815 cmꢁ1. MS (ESI): m/z 460.0
(Mþþ1). Anal. Calcd for C24H26FNO5S: C, 62.73; H, 5.70; N, 3.05.
Found: C, 62.90; H, 5.96; N, 3.01.
443.0 (Mþþ1). Anal. Calcd for C22H22N2O6S: C, 59.72; H, 5.01; N,
6.33. Found: C, 60.07; H, 5.05; N, 6.41.
Acknowledgements
We thank Dr. Renhua Fan for his invaluable advice during the
course of this research. Financial support from National Natural
Science Foundation of China (20772018), Shanghai Pujiang Pro-
gram, and Program for New Century Excellent Talents in University
(NCET-07-0208) is gratefully acknowledged.
References and notes
4.1.2.16. N-(2-(3,4-Dimethoxyphenyl)-2-(4-fluorophenyl)ethyl)-4-
methylbenzenesulfonamide (6r). 1H NMR (400 MHz, CDCl3) 2.42 (s,
3H), 3.42–3.49 (m, 2H), 3.76 (s, 3H), 3.81 (s, 3H), 4.01 (t, J¼7.8 Hz,
1H), 4.46 (t, J¼5.5 Hz, 1H), 6.54 (d, J¼1.8 Hz, 1H), 6.62 (dd, J¼8.2 Hz,
2.3 Hz, 1H), 6.77 (d, J¼8.3 Hz, 1H), 6.92–7.07 (m, 4H), 7.29 (d,
J¼7.8 Hz, 2H), 7.66 (d, J¼8.2 Hz, 2H). 13C NMR (100 MHz, CDCl3)
21.5, 47.3, 49.2, 55.7, 55.8, 111.1, 111.2, 115.4, 115.6, 119.6, 127.0, 129.2,
129.3, 129.7, 132.7, 136.5, 136.7, 136.8, 143.5, 148.1, 149.1. IR (KBr):
3273, 2934, 1599, 1511, 1328, 1159, 1093, 813 cmꢁ1. MS (ESI): m/z
430.0 (Mþþ1). Anal. Calcd for C23H24FNO4S: C, 64.32; H, 5.63; N,
3.26. Found: C, 64.70; H, 5.75; N, 3.31.
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4.1.2.17. N-(2-(Benzo[d][1,3]dioxol-5-yl)-2-(4-fluorophenyl)ethyl)-4-
methylbenzenesulfonamide (6s). 1H NMR (400 MHz, CDCl3) 2.44 (s,
3H), 3.40–3.49 (m, 2H), 3.97 (t, J¼7.8 Hz, 1H), 4.38 (t, J¼5.9 Hz, 1H),
5.91 (s, 2H), 6.50 (s, 2H), 6.54 (d, J¼7.8 Hz,1H), 6.71 (d, J¼7.7 Hz,1H),
6.94 (d, J¼8.7 Hz, 2H), 7.02–7.09 (m, 2H), 7.30 (d, J¼8.2 Hz, 2H), 7.67
(d, J¼8.2 Hz, 2H). 13C NMR (100 MHz, CDCl3) 21.5, 47.3, 49.4, 101.1,
108.1, 108.4, 115.5, 115.7, 120.9, 127.0, 129.1, 129.2, 129.7, 134.2, 136.5,
143.6, 146.6,148.1. IR (KBr): 3284, 2923, 1601, 1507, 1327, 1159, 1094,
813 cmꢁ1. MS (ESI): m/z 414.0 (Mþþ1). Anal. Calcd for C22H20FNO4S:
C, 63.91; H, 4.88; N, 3.39. Found: C, 64.07; H, 5.05; N, 3.41.
6. (a) Gong, Y.; Kato, K.; Kimoto, H. Synlett 2000, 1058; (b) Gong, Y. Tetrahedron:
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S.; BayLn, P.; Aburel, P. S.; Jøgensen, K. A. J. Org. Chem. 2002, 67, 4352; (f) Saaby,
S.; Fang, X.; Gathergood, N.; Jøgensen, K. A. Angew. Chem., Int. Ed. 2000, 39, 4114;
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see: Shirakawa, S.; Berger, R.; Leighton, J. L. J. Am. Chem. Soc. 2005, 127, 2858.
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and references cited therein.
9. (a) Ramesh, C.; Banerjee, J.; Pal, R.; Das, B. Adv. Synth. Catal. 2003, 345, 557; (b)
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J. S.; Reddy, B. V. S.; Murthy, C. V. S. R.; Kumar, G. M.; Madan, C. Synlett 2001, 783;
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see: (a) Pawda, A.; Pearson, W. H.; Lian, B. W.; Bergmeier, S. C. Comprehensive
Heterocyclic Chemistry II. Katritzky, A. R., Rees, C. W., Scriven, E. F. V., Eds.;
Pergamon: New York, NY, 1996; Vol. 1a; (b) Pawda, A.; Woolhouse, A. D.
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4.1.2.18. N-(1-(3,4-Dimethoxyphenyl)-1,2,3,4-tetrahydronaphthalen-
2-yl)-4-methylbenzenesulfonamide (6t).14 1H NMR (400 MHz,
CDCl3) 1.79–1.82 (m, 1H), 2.33–2.38 (m, 1H), 2.40 (s, 3H), 2.90–2.97
(m, 2H), 3.38–3.40 (m, 1H), 3.56 (s, 3H), 3.87 (s, 3H), 4.57 (d,
J¼5.5 Hz, 1H), 6.10 (d, J¼1.8 Hz, 1H), 6.47 (dd, J¼7.8 Hz, 1.8 Hz, 1H),
6.66–6.69 (m, 2H), 7.11–7.15 (m, 5H), 7.43 (d, J¼8.2 Hz, 2H). IR (KBr):
3284, 2932, 1596, 1514, 1327, 1158, 1094, 812 cmꢁ1. MS (ESI): m/z
438.0 (Mþþ1).
4.1.2.19. N-(2-(3,4-Dimethoxyphenyl)-1,2,3,4-tetrahydronaphthalen-
1-yl)-4-methylbenzenesulfonamide (6t0).14 1H NMR (400 MHz,
CDCl3) 1.62–1.70 (m, 1H), 1.82–1.93 (m, 1H), 2.43 (s, 3H), 2.86–3.00
(m, 2H), 3.75–3.83 (m, 1H), 3.78 (s, 3H), 3.85 (s, 3H), 4.18–4.21 (m,
2H), 6.39 (dd, J¼8.2 Hz, 1.8 Hz, 1H), 6.55 (d, J¼1.8 Hz, 1H), 6.74 (d,
J¼8.2 Hz, 1H), 6.89 (d, J¼7.3 Hz, 1H), 6.98–7.02 (m, 4H), 7.26–7.28
(m, 1H), 7.68 (d, J¼8.2 Hz, 2H). IR (KBr): 3284, 2932, 1596, 1514,
1327, 1158, 1094, 812 cmꢁ1. MS (ESI): m/z 438.0 (Mþþ1).
12. (a) Stamm, H.; Sommer, A.; Woderer, A.; Wiesert, W.; Mall, T.; Assithianakis, P.
J. Org. Chem. 1985, 50, 4946; (b) Stamm, H.; Onistschenko, A.; Buchholz, B.; Mall,
T. J. Org. Chem. 1989, 54, 193.
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D. D. Tetrahedron Lett. 2004, 45, 5011; (b) Schneider, M. R.; Mann, A.; Taddei, M.
Tetrahedron Lett. 1996, 37, 8493.
14. Yadav, J. S.; Reddy, B. V. S.; Rao, R. S.; Veerendhar, R. G.; Nagaiah, K. Tetrahedron
Lett. 2001, 42, 8067.
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16. Bera, M.; Roy, S. Tetrahedron Lett. 2007, 48, 7144.
4.1.2.20. N-(2-(3,4-Dimethoxyphenyl)-2-phenylethyl)-4-nitrobenz-
enesulfonamide (6u). 1H NMR (400 MHz, CDCl3) 3.50–3.58 (m, 2H),
3.76 (s, 3H), 3.84 (s, 3H), 4.01 (t, J¼7.7 Hz, 1H), 4.38 (t, J¼6.4 Hz, 1H),
6.57 (d, J¼1.8 Hz, 1H), 6.64 (dd, J¼8.2 Hz, 2.3 Hz, 1H), 6.77 (d,
J¼8.2 Hz, 1H), 7.09 (d, J¼6.9 Hz, 2H), 7.19–7.29 (m, 2H), 7.51 (t,
J¼7.8 Hz, 2H), 7.58–7.62 (m, 1H), 7.80 (d, J¼7.3 Hz, 2H). 13C NMR
(100 MHz, CDCl3) 47.3, 50.0, 55.8, 55.9, 111.2, 119.7, 127.0, 127.1,
127.7, 128.8, 129.1, 132.7, 132.9, 139.7, 140.8, 148.1, 149.1. IR (KBr):
3274, 2935, 1592, 1516, 1329, 1265, 1162, 1027 cmꢁ1. MS (ESI): m/z
17. Raf, G.; Mario, S.; Wim, D. Tetrahedron Lett. 2002, 43, 6605.
18. Yadav, J. S.; Reddy, B. V. S.; Abraham, S.; Sabitha, G. Tetrahedron Lett. 2002,
43, 1565.