In(OTf)3 catalyzed N-benzylation of amines utilizing benzyl alcohols in water

Article abstract of DOI:10.1016/j.tet.2013.07.010

An In(OTf)₃-catalyzed N-benzylation of amines utilizing benzyl alcohols through direct C-O bond activation has been reported. The reaction was performed in water without any base, additive, ligand or inert gas protection to afford the chem-selective mono- or bis-alkylated aromatic amines in good to excellent yields.

Full text of DOI:10.1016/j.tet.2013.07.010

Tetrahedron 69 (2013) 7988e7994
Contents lists available at SciVerse ScienceDirect
Tetrahedron
journal homepage: www.elsevier.com/locate/tet
In(OTf)3 catalyzed N-benzylation of amines utilizing benzyl alcohols
in water
,
Jin-Ming Yang a, Ran Jiang b, Lin Wu a, Xiao-Ping Xu b, Shun-Yi Wang b, Shun-Jun Ji b
*
a Key Laboratory of Coastal Wetland Bioresources and Environmental Protection of Jiangsu Province, College of Chemistry and Chemical Engineering,
Yancheng Teachers University, Yancheng 224002, China
b Key Laboratory of Organic Synthesis of Jiangsu Province, College of Chemistry, Chemical Engineering and Materials Science, Soochow University,
Suzhou 215123, China
a r t i c l e i n f o
a b s t r a c t
Article history:
An In(OTf)3-catalyzed N-benzylation of amines utilizing benzyl alcohols through direct CeO bond acti-
vation has been reported. The reaction was performed in water without any base, additive, ligand or inert
gas protection to afford the chem-selective mono- or bis-alkylated aromatic amines in good to excellent
yields.
Received 10 April 2013
Received in revised form 24 June 2013
Accepted 3 July 2013
Available online 8 July 2013
Ó 2013 Elsevier Ltd. All rights reserved.
Keywords:
In(OTf)3
N-benzylation
Amines
Water
1. Introduction
that water is the only by-product generated in the whole
procedure.
The direct alkylation especially the benzylation of amines is one
of the most practical and important approaches for the formation of
CeN bonds. N-Benzyl amine motif is featured in a wide variety of
pharmacologically and biologically active compounds. For example,
2-(4-(benzo[d][1,3]dioxol-5-ylmethyl)piperazin-1-yl) pyrimidine,
which is known as Piribedil,1 is a commonly used drug for the
treatment of Parkinson’s Disease. Another typical case in point is
Antergan2, which was among the first antihistamine drugs (Fig. 1).
Generally, the alkylation of amines is accessible by using conven-
tional alkylating agents, such as alkyl halides, in conjunction with
the use of stoichiometric amount of base.3 Recently, despite the
poor electrophilicity of most alcohols, alcohols were regarded as
green alkylation reagents in place of alkyl halides due to the fact
One popular concept to overcome the poor reactivity of alcohols
is to temporarily convert them into the corresponding carbonyl
compounds by the metal-catalyzed removal of hydrogen, which is
well-known as ‘hydrogen-borrowing methodology’ or ‘hydrogen
autotransfer processes’ (Scheme 1).4 Much efforts have been di-
rected towards the development of a transition metal-catalyzed
alkylation of amines by alcohols since the pioneer work reported
by Grigg5 and Watanable.6 Many organometallic species have been
explored as catalysts for this process, including Cu,7 Ru,8 Rh,5 Pd,9
Ir,10 Fe11 and so on.10d,e,12 However, most of these catalytic sys-
tems suffered from following limitations such as stoichiometric
amounts of base or additive, sensitive catalysts and the substrates
scope. On the other hand, benzyl alcohols were rarely used as N-
alkylation reagent through SN-type N-alkylation, because aromatic
amines were prone to undergoing FriedeleCrafts-type alkylation
with alcohols under these conditions.13 Therefore, how to develop
a single and air-tolerant Lewis acid catalyst for the mono- or bis-
benzylation of amines through direct CeO activation of benzyl al-
cohol with high selectivity was challenging and desirable.
Water is an ideal solvent for organic reactions due to its many
advantages such as nontoxic, nonflammable, abundantly available
and inexpensive. Many organic transformations have been suc-
cessfully developed in water in terms of ‘Green Chemistry’.14 Be-
sides, indium(III) salt possesses the appealing property of
Fig. 1. N-Benzyl amine motif in drugs.
* Corresponding author. Tel./fax: þ86 512 65880307; e-mail addresses: shunjun@
suda.edu.cn, chemjsj@suda.edu.cn (S.-J. Ji).
0040-4020/$ e see front matter Ó 2013 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.tet.2013.07.010

J.-M. Yang et al. / Tetrahedron 69 (2013) 7988e7994
7989
base totally inhibited the reaction in our catalytic system (Table 1,
entry 9). Moreover, the yield of 3aa decreased when other indium
species, such as InCl3, In(DS)3 and indium powder, were introduced
(Table 1, entries 10e12). Both decreasing the loading of catalyst and
lowering the temperature led to decrease of the reaction yields
(Table 1, entries 13e14). Furthermore, we observed that only 47%
yield of 3aa was isolated when 1 equiv of anisyl alcohol was
employed.
Scheme 1. Proposed mechanism for dehydrogenative activation of alcohols and sub-
sequent amination.
With the optimized reaction conditions in hand, we further
investigated the substrate scope of the reaction utilizing various
benzyl alcohols and amines. As shown in Table 2, the benzylations
of amines in water catalyzed by In(OTf)3 could be accomplished
with relatively good generality. The benzyl alcohols with electron-
donating groups (2aed) reacted smoothly with 1a, affording the
corresponding products in moderate to good yields (Table 2, entries
1e4). Unfortunately, benzyl alcohol (2e) was totally inert under the
identical conditions (Table 2, entry 5). Benzo[d][1,3]dioxol-5-
ylmethanol (2f) and ferrocenylmethanol (2g) also performed
well, giving the desired products in 65% and 78% yields, respectively
(Table 2, entries 6 and 7).
enhancing the formation of less stabilized carbocation and its ac-
tivity would not decrease even when it is dispersed in water.15
Herein, we reported an indium(III)-catalyzed16 formation of
mono- or bis-alkylated amine through direct CeO bond activation
of benzyl alcohol in water without any ligand, additive or inert gas
(Scheme 2).
In(III)
In(III)
R
O
H
R
OH
R
C-O activation
R'
N
R'
N
H2NR' or HNR'R''
or
R
H
R''
direct amination
no ligand, base, additive or inert gas
Table 2
The benzylations of 1a with 2 catalyzed by In(OTf)3 in watera
Scheme 2. In(OTf)3-catalyzed N-benzylation of amines utilizing benzyl alcohols.
2. Results and discussion
We initiated this study by the model reactions of 4-chloroaniline
(1a) with anisyl alcohol (2a) in water under different conditions. As
expected, the model reaction did not occur in the absence of cat-
alyst (Table 1, entry 1). Copper and iron species were examined
without base and ligand, only very low yields were obtained (Table
1, entries 2e4). To our surprise, In(OTf)3 showed good catalytic
activity without the participation of base or additive, affording 3aa
in 68% yield (Table 1, entry 5). Next, various solvents, such as tol-
uene, DMF, and MeOH were investigated. However, no better result
was obtained. Water gave the best result while the messy result
was observed when the model reaction was carried out in neat
conditions. We also examined the effect of base. It was found that
Entry
1
2
Products
Time (h) Yield (%)b
2a
3aa
6
68
2
3
2b
2c
3ab
3ac
7
5
65
63
Table 1
Optimization of reaction conditionsa
4
2d
2e
3ad
6
76
0
5
6
3ae 24
3af 12
Entry
Catalyst (mol %)
Solvent
Temp (ꢀC)
Yield (%)b
1
2
3
4
5
6
7
8
d
H2O
H2O
H2O
H2O
H2O
Toluene
DMF
d
100
100
100
100
100
100
100
100
100
100
100
100
100
80
d
Cu(OAc)2 (10)c
CuCl2$2H2O (10)
Nano-Fe3O4 (10)d
In(OTf)3 (10)
In(OTf)3 (10)
In(OTf)3(10)
In(OTf)3(10)
In(OTf)3 (10)/NaHCO3 (50)
InCl3 (10)
7
25
d
2f
65
78
68
58
9
Messy
d
7
2g
3ag
7
9
H2O
H2O
H2O
H2O
H2O
H2O
H2O
a
10
11
12
13
14
15
45
Reaction conditions: 1 (1.0 mmol), 2 (1.2 mmol), In(OTf)3 (0.1 mmol), H2O
(5.0 mL) at 100 ꢀC.
In(DS)3
In
In(OTf)3 (5)
In(OTf)3 (10)
In(OTf)3 (10)e
b
Isolated yield.
66
19
47
100
Next, we investigated the substrate scope of amines. The results
were summarized in Table 3. Amines with weak electron-
withdrawing groups, such as 4-bromoaniline (1b) and 4-
fluoroaniline (1c) were applied to the reactions, which could re-
act smoothly with (4-methoxyphenyl)methanol (2a) under the
optimal conditions to furnish nucleophilic-substituted products
a
Reaction conditions: 1a (1.0 mmol), 2a (1.2 mmol), In(OTf)3 (0.1 mmol), H2O
(5.0 mL).
b
c
Isolated yield.
Ref. 7.
Ref. 11b.
d
e
2a (1.0 mmol) was used.

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J.-M. Yang et al. / Tetrahedron 69 (2013) 7988e7994
Table 3
The benzylations of 1 with 2a catalyzed by In(OTf)3 in watera
Entry
1
1
Products
Time (h)
5
Yield (%)b
71
1b
3ba
2
3
1c
3ca
3da
6
42
42
1d
24
4
5
1e
1f
3ea
3fa
24
24
37
46
6
1g
3ga
6
87
7
8
1h
1i
3ha
3ia
4
5
99
70
9
1j
3ja
5
96
10
11
1k
1l
3ka
3la
8
5
5
80
97
75
12
1m
3ma
a
Reaction conditions: 1 (1.0 mmol), 2 (1.2 mmol), In(OTf)3 (0.1 mmol), H2O (5.0 mL) at 100 ꢀC.
Isolated yield.
b
(3ba and 3ca) in 71% and 42% yields (Table 3, entries 1 and 2). The
entries 6 and 7). When more bulkier substrate 2-nitro aniline was
subjected to the reaction, the yield was decreased to 70% (Table 3,
entry 8). Other anilines (1gel) bearing electron-donating groups
were also investigated, all of them worked well under the opti-
mized conditions (Table 3, entries 9e11). In the case of 4-
aminobenzoic acid possessing a free carboxylic acid functionality,
it also served as a good substrate under the conditions to give the
desired product in 75% yield (Table 3, entry 12).
amines bearing electron-donating groups (1def) could also react
with 2a as well, generating the desired products within 24 h in little
lower yields (Table 3, entries 3e5). On the other hand, the presence
of a strong electron-withdrawing group such as nitro at the meta or
ortho position of anilines (1geh), reacted smoothly with (4-
methoxyphenyl)methanol (2a) under the standard conditions to
afford the corresponding products in 87e99% yields (Table 3,

J.-M. Yang et al. / Tetrahedron 69 (2013) 7988e7994
7991
Then, we examined other aromatic amines analogue under the
optimized conditions. As shown in Fig. 2, both benzo[d]thiazol-2-
amine and 1H-benzo[d][1,2,3]triazole served as good candidates
as well, leading to the N-benzylation product 3na and 3oa in 65%
and 60% yields, respectively. It was notable that N-dialkylation
products (4aa, 4ab and 4ac) were obtained in moderate to good
yields when the amount of the benzyl alcohols was increased from
1.2 to 3.2 equiv.
Scheme 5. Proposed mechanism.
3. Conclusion
We have developed an In(OTf)3-catalyzed direct benzylation of
amines ultilizing benzyl alcohols in water. Various amines, benzo[d]
thiazol-2-amine and 1H-benzo[d][1,2,3]triazole could react well
with benzyl alcohols without any base or additive, affording the
corresponding products in moderate to good yields. Mono- or bis-
alkylation of amine could be achieved with high selectivity by using
various equivalent of benzyl alcohols.
Fig. 2. Benzylation of amines with benzyl alcohols. aReaction conditions: amine
(1.0 mmol), benzyl alcohol (1.2 mmol), In(OTf)3 (0.1 mmol), H2O (5.0 mL) at 100 ꢀC.
b3.2 equiv of alcohol was used.
4. Experimental section
4.1. General
When diphenylmethanol (5) was subjected to the reaction with
4-chloroaniline (1) under the identical conditions, it was found that
the direct nucleophilic substituted product 6 could also be obtained
in low yield (Scheme 3).
Melting points were recorded on an electrothermal digital
melting point apparatus and were uncorrected. IR spectra were
recorded on a Varian FT-1000 spectrophotometer using KBr optics.
1H NMR and 13C NMR spectra were recorded on a Varian INOVA 300
or 400 MHz (1H NMR) and 75 or 100 MHz (13C NMR) spectrometer
using CDCl3 as solvent and TMS as internal standard. High resolu-
tion mass spectra were obtained using GCT-TOF instrument with
ESI source.
4.2. General procedure for the alkylation of indoles, anilines
and thiols with enamide
Scheme 3.
Amine (1.0 mmol), In(OTf)3 (0.1 mmol) and anisyl alcohol
(1.2 mmol) were added into a flask. Then the mixture was vigor-
ously stirred at reflux, until amine was completely consumed as
indicated by TLC analysis or 24 h. After the completion of reaction,
CH2Cl2 (15 mLꢁ2) was used to extract the product, the organic layer
was dried with anhydrous Na2SO4. Then the solvent was evapo-
rated under the reduced pressure. The residue was purified by flash
column chromatography with ethyl acetate and petroleum ether as
eluents to afford pure product. This procedure was followed for the
synthesis of other N-benzylation amines.
In order to better understand the mechanism of this reaction,
the mixture of (E)-N-(4-methoxybenzylidene)-4-nitroaniline,
which was easily isolated as an intermediate in ‘hydrogen auto-
transfer processes’, and 1a was treated under our optimal condi-
tions. As expected, no N-(4-methoxybenzyl)-4-nitroaniline or 4-
methoxybenzaldehyde was observed (Scheme 4). This results in-
dicated that the ‘hydrogen-borrowing methodology’ or ‘hydrogen
autotransfer processes’ was not involved in catalytic system. As
shown in Scheme 5, we proposed a plausible mechanism for this
reaction. First, the CeO bond was activated by coordination with
In(III) and water. Subsequently, CeO bond was cleaved to form
a benzyl type carbonium, which was prone to be stabilized by the
electron-donating groups in aromatic ring. Finally, the amine
attacked the carbonium to give the final product.
4.2.1. N-(4-Methoxybenzyl)-4-chlorobenzenamine (3aa). Yield (168
mg, 68%). Rf¼0.62 (petroleum ether/ethyl acetate¼4:1). Mp:
84e85 ꢀC; IR (KBr):
NMR (400 MHz, CDCl3):
n
¼3407, 2918, 1595, 1490, 1235, 815 cmꢂ1
;
1H
d
¼7.27 (d, J¼7.8 Hz, 2H), 7.11 (d, J¼8.6 Hz,
2H), 6.88 (d, J¼8.5 Hz, 2H), 6.56 (d, J¼8.7 Hz, 2H), 4.22 (s, 2H),
3.80 ppm (s, 3H); 13C NMR (100 MHz, CDCl3):
d
¼159.2, 146.9, 131.1,
129.2, 128.9, 122.3, 114.3, 114.1, 55.5, 48.1 ppm. HRMS (m/z): [M]þ,
calcd for C14H14ClNO: 247.0764, found: 247.0763.
4.2.2. 4-Chloro-N-(3,4-dimethoxybenzyl)aniline (3ab). Yield (180
mg, 65%). Rf¼0.61 (petroleum ether/ethyl acetate¼4:1). Mp:
128e130 ꢀC; IR (KBr):
n
¼3370, 2937, 2844, 1594, 1504, 1243, 1022,
813 cmꢂ1
;
1H NMR (300 MHz, CDCl3):
d
¼3.87 (s, 6H), 4.22 (s, 2H),
Scheme 4.
6.56 (d, J¼4.9 Hz, 2H), 6.84e6.88 (m, 3H), 7.11 ppm (d, J¼5.1 Hz,

7992
J.-M. Yang et al. / Tetrahedron 69 (2013) 7988e7994
2H); 13C NMR (75 MHz, DMSO-d6):
d
¼148.8, 147.7, 147.6, 132.1,
148.4, 131.6, 129.5, 129.0, 117.7, 114.2, 113.1, 55.5, 48.0 ppm. HRMS
128.5, 119.3,119.0,113.8,111.7,111.2, 55.5, 55.4, 46.3 ppm; HRMS (m/
(m/z): [M]þ, calcd for C14H15NO: 213.1154, found: 213.1150.
z): [M]þ, calcd for C15H16ClNO2: 277.0870, found: 277.0868.
4.2.10. N-(4-Methoxybenzyl)-4-methoxybenzenamine (3ea). Yield
(90 mg, 37%). Rf¼0.62 (petroleum ether/ethyl acetate¼4:1). Mp:
4.2.3. N-(2,3,4-Trimethoxybenzyl)-4-chlorobenzenamine (3ac). Yield
(193 mg, 63%). Rf¼0.63 (petroleum ether/ethyl acetate¼4:1). Mp:
96e97 ꢀC; IR (KBr):
n
¼3379, 2942, 2834, 1603, 1511, 1245, 1028,
110e111 ꢀC; IR (KBr):
n
¼3366, 2936, 1593, 1489, 1090, 809 cmꢂ1; 1H
818 cmꢂ1; 1H NMR (300 MHz, CDCl3):
d
¼7.29 (d, J¼8.3 Hz, 2H), 6.87
NMR (300 MHz, CDCl3):
d
¼3.84 (s, 3H), 3.88 (s, 3H), 3.92 (s, 3H), 4.03
(d, J¼8.4 Hz, 2H), 6.78 (d, J¼8.7 Hz, 2H), 6.60 (d, J¼8.7 Hz, 2H), 4.20
(br s, H, NH), 4.22 (s, 2H), 6.56 (d, J¼8.5 Hz, 2H), 6.61 (d, J¼8.4 Hz,
(s, 2H), 3.80 (s, 3H), 3.74 ppm (s, 3H); 13C NMR (75 MHz, DMSO-d6):
1H), 6.69 (d, J¼8.3 Hz, 1H), 7.10 ppm (d, J¼7.2 Hz, 2H); 13C NMR
d
¼159.0, 152.4, 142.6, 131.8, 129.0, 115.1, 114.4, 114.2, 77.2, 56.0, 55.5,
(100 MHz, CDCl3):
d¼153.4, 52.0, 146.9, 142.4, 129.2, 124.6, 123.5,
49.0 ppm. HRMS (m/z): [M]þ, calcd for C15H17NO2: 243.1259, found:
122.1, 114.3, 107.2, 61.3, 61.0, 56.1, 43.6 ppm; HRMS (m/z): [M]þ,
243.1259.
calcd for C16H18ClNO3: 307.0975, found: 307.0977.
4.2.11. (4-Methoxy-benzyl)-p-tolyl-amine (3fa). Yield (104 mg,
46%). Rf¼0.63 (petroleum ether/ethyl acetate¼4:1). Mp: 82e83 ꢀC;
4.2.4. 4-Chloro-N-(4-morpholinobenzyl)aniline (3ad). Yield (230 mg,
76%). Rf¼0.64 (petroleum ether/ethyl acetate¼4:1). Mp: 186e187 ꢀC;
IR (KBr):
CDCl3):
n
¼3392, 2936, 1597, 1493, 820 cmꢂ1
;
1H NMR (400 MHz,
IR (KBr):
n
¼3357, 2838, 1598, 1504, 1225, 1107, 809 cmꢂ1
;
1H NMR
d
¼7.28 (d, J¼8.4 Hz, 2H), 6.98 (d, J¼8.1 Hz, 2H), 6.87 (d,
(300 MHz, CDCl3):
d
¼3.16 (t, J¼4.5 Hz, 4H), 3.87 (t, J¼4.5 Hz, 4H), 4.21
J¼8.4 Hz, 2H), 6.57 (d, J¼8.2 Hz, 2H), 4.23 (s, 2H), 3.81 (s, 3H),
(s, 2H), 6.55 (d, J¼8.7 Hz, 2H), 6.92 (d, J¼8.7 Hz, 2H), 7.11 (d, J¼8.7 Hz,
2.23 ppm (s, 3H); 13C NMR (75 MHz, CDCl3):
d¼159.0, 145.9, 131.6,
2H), 7.26 ppm (d, J¼8.7 Hz, 2H); 13C NMR (75 MHz, CDCl3):
d¼150.8,
129.9, 129.1, 127.2, 114.2, 113.5, 55.5, 48.5, 20.6 ppm; HRMS (m/z):
146.9, 130.4, 129.2, 128.7, 122.2, 116.1, 114.1, 67.1, 49.6, 48.0 ppm;
[M]þ, calcd for C15H17NO: 227.1310, found: 227.1311.
HRMS (m/z): [M]þ, calcd for C17H19ClN2O: 302.1186, found: 302.1184.
4.2.12. N-(4-Methoxybenzyl)-4-nitrobenzenamine (3ga). Yield (87%).
Rf¼0.58 (petroleum ether/ethyl acetate¼4:1). Mp: 146e147 ꢀC; IR
4.2.5. N-(Benzo[d][1,3]dioxol-5-ylmethyl)-4-chloroaniline (3af). Yield
(170 mg, 65%). Rf¼0.62 (petroleum ether/ethyl acetate¼4:1). Mp:
(KBr):
n
¼3352, 1598, 1512, 1299, 1070, 816 cmꢂ1; 1H NMR (300 MHz,
100e102 ꢀC; IR (KBr):
n
¼3368, 2874, 1597, 1490, 1243, 1103,
DMSO-d6):
d
¼7.97 (d, J¼9.1 Hz, 2H), 7.77 (t, J¼5.9 Hz, 1H), 7.27 (d,
808 cmꢂ1
;
1H NMR (300 MHz, CDCl3):
d
¼4.20 (s, 2H), 5.95 (s, 2H),
J¼7.5 Hz, 2H), 6.91 (d, J¼7.1 Hz, 2H), 6.67 (d, J¼9.0 Hz, 2H), 4.33 (s,
6.57 (d, J¼7.0 Hz, 2H), 6.79 (m, 3H), 7.11 ppm (d, J¼6.8 Hz, 2H); 13C
2H), 3.73 ppm (s, 3H); 13C NMR (75 MHz, DMSO-d6):
d¼158.4, 154.4,
NMR (75 MHz, CDCl3):
d¼148.1, 147.0, 146.6, 132.9, 129.2, 122.4, 120.7,
135.8, 130.3, 128.6, 126.2, 113.9, 111.2, 55.1, 45.3, 45.2 ppm. HRMS (m/
z): [M]þ, calcd for C14H14N2O3: 258.1004, found: 258.1008.
114.2, 108.5, 108.1, 101.2, 48.4 ppm; HRMS (m/z): [M]þ, calcd for
C14H12ClNO2: 261.0557, found: 261.0558.
4.2.13. N-(4-Methoxybenzyl)-3-nitrobenzenamine (3ha). Yield (255
mg, 99%). Rf¼0.65 (petroleum ether/ethyl acetate¼4:1). Mp:
4.2.6. N-(1-Ferrocenylmethyl)-4-chloroaniline (3ag). Yield (252 mg,
78%). Rf¼0.60 (petroleum ether/ethyl acetate¼4:1). Mp:
116e117 ꢀC; IR (KBr): 3421, 3086, 2901, 2856, 1595, 1499, 1463,
97e98 ꢀC; IR (KBr):
n
¼3404, 2915, 1620, 1517, 1342, 808 cmꢂ1
;
1H
NMR (300 MHz, DMSO-d6):
d
¼7.25e7.32 (m, 5H), 7.03e6.80 (m,
1400, 1320, 1247, 1102, 815 cmꢂ1
;
1H NMR (300 MHz, CDCl3):
4H), 4.24 (d, J¼4.1 Hz, 2H), 3.70 ppm (s, 3H); 13C NMR (75 MHz,
d
¼3.92 (br s, 3H, CH2, NH), 4.15e4.23 (m, 9H), 6.57 (d, J¼7.5 Hz, 2H),
DMSO-d6):
d¼158.3, 149.7, 148.8, 129.9, 128.5, 118.5, 113.8, 109.9,
7.13 ppm (d, J¼7.2 Hz, 2H); 13C NMR (75 MHz, CDCl3):
d
¼147.2,
105.6, 55.0, 45.6 ppm. HRMS (m/z): [M]þ, calcd for C14H14N2O3:
129.5, 129.2, 122.3, 114.3, 86.4, 69.1, 69.1, 68.9, 68.6, 68.4, 68.2,
43.9 ppm; HRMS (m/z): [M]þ, calcd for C17H16ClFeN: 325.0321,
found: 325.0322.
258.1004, found: 258.1003.
4.2.14. N-(4-Methoxybenzyl)-2-nitrobenzenamine (3ia). Yield (181
mg, 70%). Rf¼0.61 (petroleum ether/ethyl acetate¼4:1). Mp:
4.2.7. N-(4-Methoxybenzyl)-4-bromobenzenamine
(207 mg, 71%). Rf¼0.63 (petroleum ether/ethyl acetate¼4:1). Mp:
86e88 ꢀC; IR (KBr):
¼3400, 2905, 1530, 1495, 1302, 1022,
811 cmꢂ1; 1H NMR (300 MHz, DMSO-d6):
¼7.23 (d, J¼7.4 Hz, 2H),
7.14 (d, J¼8.7 Hz, 2H), 6.86 (d, J¼8.4 Hz, 2H), 6.50 (d, J¼8.6 Hz, 2H),
4.14 (s, 2H), 3.70 ppm (s, 3H); 13C NMR (75 MHz, CDCl3):
(3ba). Yield
97e98 ꢀC; IR (KBr):
n
¼3382, 2941, 1604,1498, 1350,1019, 827 cmꢂ1
;
1H NMR (300 MHz, DMSO-d6):
d
¼8.56 (t, J¼4.9 Hz, 1H, NH), 8.04 (d,
n
J¼8.6 Hz, 1H), 7.42 (t, J¼7.7 Hz, 1H), 7.28 (d, J¼8.1 Hz, 2H), 6.89 (t,
d
J¼9.7 Hz, 3H), 6.63 (t, J¼7.7 Hz, 1H), 4.51 (d, J¼5.5 Hz, 2H), 3.69 ppm
(s, 3H); 13C NMR (100 MHz, DMSO-d6):
d¼158.4, 144.9, 136.4, 130.2,
d
¼159.2,
126.2, 115.4, 115.0, 114.0, 113.6, 55.1, 55.0, 45.2 ppm. 1HRMS (m/z):
146.9, 132.1, 130.8, 129.0, 114.9, 114.3, 109.6, 55.5, 48.2 ppm; HRMS
[M]þ, calcd for C14H14N2O3: 258.1004, found: 258.1005.
(m/z): [M]þ, calcd for C14H14BrNO: 291.0259, found: 291.0258.
4.2.15. 4-(4-Methoxybenzylamino)benzonitrile (3ja). Yield (228 mg,
96%). Rf¼0.62 (petroleum ether/ethyl acetate¼4:1). Mp:
4.2.8. N-(4-Methoxybenzyl)-4-fluorobenzenamine (3ca). Yield (97
mg, 42%). Rf¼0.61 (petroleum ether/ethyl acetate¼4:1). Mp:
109e111 ꢀC; IR (KBr):
n
¼3376, 2851, 2202, 1602, 1513, 820 cmꢂ1; 1H
70e71 ꢀC; IR (KBr):
n
¼3407, 2921, 1598, 1508, 1237, 1107, 820 cmꢂ1
;
NMR (300 MHz, DMSO-d6):
d
¼7.42 (d, J¼7.0 Hz, 2H), 7.26e7.21 (m,
1H NMR (300 MHz, CDCl3):
d
¼7.28 (d, J¼8.4 Hz, 2H), 6.88 (dt, J¼8.5,
3H), 6.89 (d, J¼6.7 Hz, 2H), 6.64 (d, J¼7.0 Hz, 2H), 4.25 (d, J¼5.0 Hz,
4.2 Hz, 4H), 6.62e6.52 (m, 2H, ArH), 4.21 (s, 2H), 3.80 ppm (s, 3H);
2H), 3.72 ppm (s, 3H); 13C NMR (100 MHz, DMSO-d6):
d¼158.3,
13C NMR (75 MHz, CDCl3):
d¼159.1, 157.6, 154.5, 144.6, 131.3, 129.0,
152.1, 133.3, 130.7, 128.5, 120.6, 113.8, 112.1, 95.8, 55.1, 55.0, 45.2.
116.0, 115.7, 114.2, 113.9, 113.8, 77.7, 77.2, 76.8, 55.5, 48.6 ppm. HRMS
HRMS (m/z): [M]þ, calcd for C15H14N2O: 238.1106, found: 238.1106.
(m/z): [M]þ, calcd for C14H14FNO: 231.1059, found: 231.1052.
4.2.16. 1-(4-(4-Methoxybenzylamino)phenyl)ethanone (3ka). Yield
(204 mg, 80%). Rf¼0.65 (petroleum ether/ethyl acetate¼4:1). Mp:
4.2.9. (4-Methoxy-benzyl)-phenyl-amine (3da). Yield (89 mg, 42%).
Rf¼0.59 (petroleum ether/ethyl acetate¼4:1). Mp: 75e77 ꢀC; IR
116e117 ꢀC; IR (KBr):
n
¼3341, 2855, 1635, 1584, 1255, 817 cmꢂ1; 1H
(KBr):
n
¼3410, 2934, 1598, 1491, 1303, 1244, 818 cmꢂ1
;
1H NMR
NMR (300 MHz, DMSO-d6):
d
¼7.68 (d, J¼8.6 Hz, 2H), 7.26 (d,
(400 MHz, CDCl3):
6.86 (d, J¼8.6 Hz, 2H), 6.73 (t, J¼8.2 Hz, 1H), 6.66 (d, J¼8.0 Hz, 2H),
d
¼7.28 (d, J¼8.5 Hz, 2H), 7.17 (t, J¼7.9 Hz, 2H),
J¼8.0 Hz, 2H), 6.89 (d, J¼8.4 Hz, 2H), 6.60 (d, J¼8.6 Hz, 2H), 4.27 (s,
2H), 3.72 (s, 3H), 2.37 ppm (s, 3H); 13C NMR (75 MHz, DMSO-d6):
4.24 (s, 2H), 3.79 ppm (s, 3H); 13C NMR (100 MHz, CDCl3):
d
¼151.8,
d¼195.0, 158.2, 152.7, 131.1, 130.4, 128.4, 125.0, 113.8, 111.1, 55.0,

J.-M. Yang et al. / Tetrahedron 69 (2013) 7988e7994
7993
45.2, 25.9 ppm. HRMS (m/z): [M]þ, calcd for C16H17NO2: 255.1259,
3.88 (s, 6H), 3.84 ppm (s, 6H, OCH3); 13C NMR (75 MHz, CDCl3):
found: 255.1266.
d
¼153.9, 153.5, 151.6, 142.4, 137.5, 126.3, 121.6, 121.4, 111.1, 107.2, 61.0,
60.9, 56.2, 49.8 ppm. HRMS (m/z): [M]þ, calcd for C26H30N2O8:
4.2.17. Ethyl
(276 mg, 97%). Rf¼0.58 (petroleum ether/ethyl acetate¼4:1). Mp:
127e128 ꢀC; IR (KBr):
¼3357, 2948, 1679, 1596, 1255, 1014,
825 cmꢂ1; 1H NMR (300 MHz, DMSO-d6):
4-(4-methoxybenzylamino)benzoate
(3la). Yield
498.2002, found: 498.2010.
n
4.2.24. N-Benzhydryl-4-chlorobenzenamine (6aa). Yield (132 mg,
45%): Rf¼0.62 (petroleum ether/ethyl acetate¼4:1). Mp: 90e91 ꢀC;
d¼7.65 (d, J¼8.7 Hz, 2H),
7.26 (d, J¼8.5 Hz, 2H), 7.02 (t, J¼5.6 Hz, 1H), 6.89 (d, J¼8.6 Hz, 2H),
6.60 (d, J¼8.7 Hz, 2H), 4.25 (d, J¼5.8 Hz, 2H), 4.19 (q, J¼7.1 Hz, 2H),
3.72 (s, 3H), 1.25 ppm (t, J¼7.1 Hz, 3H); 13C NMR (100 MHz, DMSO):
IR (KBr):
n
¼3409, 3068, 2844, 1591, 1484, 1305, 1085, 812 cmꢂ1; 1H
NMR (300 MHz, CDCl3):
d
¼7.33e7.27 (m, 10H), 7.04 (d, J¼8.8 Hz,
2H), 6.45 (d, J¼8.7 Hz, 2H), 5.45 (s, 1H), 4.24 ppm (s, 1H); 13C NMR
d
¼165.8, 158.2, 152.6, 131.1, 130.9, 128.5, 116.2, 113.8, 111.2, 59.5,
(75 MHz, CDCl3):
d¼146.0, 142.6, 129.1, 129.0, 127.7, 127.6, 122.5,
55.0, 45.3, 14.4 ppm; HRMS (m/z): [M]þ, calcd for C17H19NO3:
114.8, 77.7, 77.2, 76.8, 63.3 ppm. HRMS (m/z): [M]þ, calcd for
285.1365, found: 285.1367.
C19H16ClN: 293.0971, found: 293.0969.
4.2.18. 4-(4-Methoxybenzylamino)benzoic acid (3ma). Yield (193 mg,
75%). Rf¼0.59 (petroleum ether/ethyl acetate¼4: 1). Mp:
4.2.25. N-(Bis(4-methoxyphenyl)methyl)aniline (6bd). Yield (118 mg,
37%): Rf¼0.65 (petroleum ether/ethyl acetate¼4:1). liquid, IR (KBr):
209e211 ꢀC; IR (KBr):
n
¼3364, 2846, 1667, 1598, 1511, 1293,
n
¼3409, 3068, 2844, 1591, 1484, 1305, 1085, 812 cmꢂ1
;
1H NMR
821 cmꢂ1
;
1H NMR (300 MHz, DMSO-d6):
d
¼11.97 (s, 1H), 7.61 (d,
(400 MHz, CDCl3):
d
¼7.24 (d, J¼8.6 Hz, 4H), 7.10 (t, J¼7.6 Hz, 2H),
J¼8.3 Hz, 2H), 7.24 (d, J¼8.2 Hz, 2H), 6.95 (t, J¼4.9 Hz, 1H), 6.87 (d,
6.84 (d, J¼8.5 Hz, 4H), 6.67 (t, J¼7.0 Hz, 1H), 6.53 (d, J¼8.2 Hz, 2H),
J¼8.1 Hz, 2H), 6.56 (d, J¼8.4, 2H), 4.22 (d, 2H), 3.70 ppm (s, 3H); 13C
5.40 (s, 1H), 3.76 (s, 6H). 13C NMR (75 MHz, CDCl3):
d¼158.4, 147.4,
NMR (100 MHz, DMSO-d6):
d¼167.5, 158.2, 152.4, 131.2, 131.1, 128.5,
128.9, 128.5, 117.4, 114.1, 113.4, 61.9, 55.2 ppm. HRMS (m/z): [M]þ,
117.0, 113.8, 111.2, 55.1, 45.4 ppm. HRMS (m/z): [M]þ, calcd for
calcd for C21H21NO2: 319.1572, found: 319.1575.
C15H15NO3: 257.1052, found: 257.1056.
Acknowledgements
4.2.19. N-(4-Methoxybenzyl)benzo[d]thiazol-2-amine (3na). Yield
(176 mg, 65%). Rf¼0.61 (petroleum ether/ethyl acetate¼4:1). Mp:
We gratefully acknowledge support from the National Natural
Science Foundation of China (No. 21172162, 21104064), the Young
National Natural Science Foundation of China (No. 21202111), the
Young Natural Science Foundation of Jiangsu Province (BK2012174),
Natural Science Basic Research of Jiangsu Province for Higher Ed-
ucation (No. 10KJB150016), the Jiangsu Provincial Key Laboratory of
Coastal Wetland Bioresources and Environmental Protection
(JLCBE06008), PAPD, and Soochow University for financial support.
172e173 ꢀC; IR (KBr):
n
¼3205, 2925, 2835, 1553, 1445, 1245,
830 cmꢂ1; 1H NMR (300 MHz, DMSO-d6):
d
¼8.40 (s,1H, NH), 7.63 (d,
J¼7.6 Hz, 1H), 7.35 (d, J¼7.9 Hz, 1H), 7.28 (d, J¼7.9 Hz, 1H), 7.18 (d,
J¼7.5 Hz, 2H), 6.98(t, J¼7.0Hz,1H), 6.88 (d, J¼8.2 Hz, 2H), 4.47(s, 2H),
3.70 ppm (s, 3H); 13C NMR (100 MHz, DMSO-d6):
d
¼166.0, 158.4,
152.4, 130.8, 130.4, 128.8, 125.5, 120.9, 118.1, 113.8, 55.1, 46.6 ppm.
HRMS (m/z): [M]þ, calcd for C15H14N2OS: 270.0827, found: 270.0828.
4.2.20. 1-(4-methoxybenzyl)-1H-benzo[d][1,2,3]triazole (3oa). Yield
(143 mg, 60%). Rf¼0.59 (petroleum ether/ethyl acetate¼4:1). Mp:
Supplementary data
85e86 ꢀC; IR (KBr):
n
¼2944, 1600, 1506, 1240, 1018, 830 cmꢂ1
;
1H
Supplementary data related to this article can be found at http://
dx.doi.org/10.1016/j.tet.2013.07.010.
NMR (300 MHz, CDCl3):
d
¼3.77 (s, 3H), 5.78 (s, 2H), 6.86 (d,
J¼8.5 Hz, 2H), 7.25 (d, J¼9.9 Hz, 2H), 7.31e7.37 (m, 3H), 8.06 ppm (d,
J¼7.9 Hz, 1H); 13C NMR (100 MHz, CDCl3):
¼159.7, 146.3, 132.7,
d
References and notes
129.1, 127.3, 126.8, 123.9, 119.9, 114.4, 109.9, 55.3, 51.8 ppm. HRMS
(m/z): [M]þ, calcd for C14H13N3O: 239.1059, found: 239.1054.
1. (a) Millan, M. J.; Cussac, D. R.; Milligan, G.; Carr, C.; Audinot, V.; Gobert, A.;
Lejeune, F.; Rivet, J. M.; Brocco, M.; Duqueyroix, D.; Nicolas, J. P.; Boutin, J. A.;
Newman-Tancredi, A. J. Pharmacol. Exp. Ther. 2001, 297, 876e887; (b) Gobert, A.;
Cara, B. D.; Cistarelli, L.; Millan, M. J. J. Pharmacol. Exp. Ther. 2003, 305, 338e346.
2. Bovet, D. Ann. N. Y. Acad. Sci. 1950, 50, 1089e1126.
3. Salvatore, R. N.; Yoon, C. H.; Jung, K. W. Tetrahedron 2001, 57, 7785e7811.
4. Selected reviews, see: (a) Hamid, M. H. S. A.; Slatford, P. A.; Williams, J. M. J. Adv.
Synth. Catal. 2007, 349, 1555e1575; (b) Nixon, T. D.; Whittlesey, M. K.; Williams,
4.2.21. N,N-Bis(4-methoxybenzyl)-4-nitrobenzenamine (4aa). Yield
(287 mg, 76%). Rf¼0.58 (petroleum ether/ethyl acetate¼4: 1). Mp:
94e95 ꢀC; IR (KBr):
n
¼2932, 2839, 1596, 1502, 1317, 1237, 818 cmꢂ1
;
1H NMR (300 MHz, DMSO-d6):
d
¼7.97 (d, J¼9.4 Hz, 2H), 7.15 (d,
J¼8.5 Hz, 4H), 6.89 (d, J¼8.6 Hz, 4H), 6.79 (d, J¼9.5 Hz, 2H), 4.74 (s,
ꢀ
J. M. J. Dalton Trans. 2009, 753e762; (c) Guillena, G.; Ramon, D. J.; Yus, M. Chem.
Rev. 2010, 110, 1611e1641; (d) Dobereiner, G. E.; Crabtree, R. H. Chem. Rev. 2010,
4H), 3.70 ppm (s, 6H).13C NMR (100 MHz, DMSO-d6):
d
¼158.4,153.4,
136.1, 128.9, 127.8, 125.8, 114.1, 111.5, 55.1, 55.0, 53.4 ppm. HRMS (m/
z): [M]þ, calcd for C22H22N2O4: 378.1580, found: 378.1577.
110, 681e703; (e) Fujita, K. I.; Yamaguchi, R. Synlett 2005, 560e571; (f) Guillena,
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G.; Ramon, D.; Yus, M. Angew. Chem., Int. Ed. 2007, 46, 2358e2364; (g) Nixon, T.
D.; Whittlesey, M. K.; Williams, J. M. J. Dalton Trans. 2009, 5, 753e762; (h)
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Commun. 1981, 611e612.
6. (a) Watanabe, Y.; Tsuji, Y.; Ohsugi, Y. Tetrahedron Lett. 1981, 22, 2667e2670; (b)
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8. Selected examples, see: (a) Hamid, M.; Williams, J. M. J. Tetrahedron Lett. 2007,
4.2.22. 4-[Bis-(4-methoxy-benzyl)-amino]-benzonitrile (4ab). Yield
(290 mg, 81%). Rf¼0.63 (petroleum ether/ethyl acetate¼4:1). Mp:
87e88 ꢀC; IR (KBr):
n
¼2933, 2209, 1601, 1512, 1237, 1029, 811 cmꢂ1
;
1H NMR (300 MHz, DMSO-d6):
d
¼7.45 (d, J¼8.9 Hz, 2H), 7.13 (d,
J¼8.5 Hz, 4H), 6.87 (d, J¼8.6 Hz, 4H), 6.73 (d, J¼9.0 Hz, 2H), 4.67 ppm
€
(s, 4H), 3.70 (s, 6H); 13C NMR (75 MHz, DMSO-d6):
d
¼158.3, 151.2,
€
133.2,129.4,127.8,120.3,114.1,112.4, 96.4, 55.1, 53.2 ppm. HRMS (m/
z): [M]þ, calcd for C23H22N2O2: 358.1681, found: 358.1682.
€
48, 8263e8265; (b) Tillack, A.; Hollmann, D.; Mevius, K.; Michalik, D.; Bahn, S.;
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Angew. Chem. Int. Ed. 2008, 47, 8661e8664; (d) Hamid, M. H. S. A.; Allen, C. L.;
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Am. Chem. Soc. 2009, 131, 1766e1774; (e) Gnanaprakasam, B.; Zhang, J.; Milstein,
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Yield (398 mg, 80%). Rf¼0.59 (petroleum ether/ethyl acetate¼4:1).
Mp: 79e80 ꢀC; IR (KBr):
n
¼2930, 2211, 1597, 1497, 1271, 1089,
€
808 cmꢂ1
;
1H NMR (300 MHz, CDCl3):
d¼8.06 (d, J¼9.4 Hz, 2H),
6.64e6.72 (m, 4H), 6.59 (d, J¼8.6 Hz, 2H), 4.65 (s, 4H), 3.91 (s, 6H),

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9888e9891; (h) Pingen, D.; Muller, C.; Vogt, D. Angew. Chem. Int. Ed. 2010, 49,
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D.; Butler, C.; Incarvito, C. D.; Crabtree, R. H. Organometallics 2009, 28, 321e325;
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Cui, X.; Zhang, Y.; Shi, F.; Deng, Y. Chem.dEur. J. 2011, 17, 1021e1028.
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