An efficient method for the synthesis of α-arylated nitroalkanes and α-arylated hydroximoyl chlorides mediated by AlCl3

Article abstract of DOI:10.1016/j.tet.2009.01.075

Friedel-Crafts alkylation of various arenes/heteroarenes to β-nitrostyrenes mediated by aluminum chloride is described. The interesting feature of this methodology pertain the formation of different products by tuning the reaction temperature. α-Arylated

Full text of DOI:10.1016/j.tet.2009.01.075

Tetrahedron 65 (2009) 2436–2442
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An efficient method for the synthesis of
a-arylated nitroalkanes and a-arylated
hydroximoyl chlorides mediated by AlCl3
Zhijay Tu, B. Rama Raju, Tzuo-Rung Liou, Veerababurao Kavala, Chun-Wei Kuo, Yaochung Jang,
*
Yu-Hsuan Shih, Chun-Chao Wang, Ching-Fa Yao
Department of Chemistry, National Taiwan Normal University, 88, Sec. 4, Tingchow Road, Taipei 116, Taiwan, ROC
a r t i c l e i n f o
a b s t r a c t
Article history:
Friedel–Crafts alkylation of various arenes/heteroarenes to
b-nitrostyrenes mediated by aluminum
Received 25 September 2008
Received in revised form 8 January 2009
Accepted 20 January 2009
Available online 23 January 2009
chloride is described. The interesting feature of this methodology pertain the formation of different
products by tuning the reaction temperature.
ꢀ78 ꢁC, whereas
a
-Arylated nitroalkanes were formed predominately at
a-arylated hydroximoyl chlorides were obtained at room temperature without any side
products in high yields.
Ó 2009 Elsevier Ltd. All rights reserved.
14
1. Introduction
compounds forming isoxazolines and isoxazoles.
Several
methods have been described in the literature for the in situ gen-
eration of nitrile oxides,15 amongst which base-induced dehydro
halogenation of hydroximoyl chlorides are the most frequently
used. Usually, hydroximoyl chlorides are prepared by chlorination
of aldoximes, for which a number of chlorinating reagents such as
chlorine,16 nitrosyl chloride,17 tert-butyl hypochlorite,18 N-chloro
succinimide19 in N,N-dimethyl formamide and HCl/N,N-dime-
thylformamide/oxone20 have been employed. A literature survey
revealed that very few hydroximoyl chlorides/nitrile oxides pos-
Metal-catalyzed addition of aromatic substrates to electron
deficient - and -systems, commonly known as Friedel–Crafts (F–
s
p
C) alkylation,1 have long been established as a powerful strategy for
C–C bond formation.2 Originally, the F–C reaction occurs between
alkyl halides and electron-rich arenes in the presence of different
Lewis acids.3 Other alkylating agents, which are widely used for
alkylation of arenes are alcohols,4 esters,5 and alkenes.6 Among
alkenes, nitroalkenes and their F–C adducts gained importance due
to their application as intermediates in pharmaceutical prepara-
tions.7 Several methods have been reported in the literature re-
garding the reaction between nitroolefins and aromatic/
heteroaromatic systems.8 Nevertheless, most reports9 in this area
are still focused on relatively more reactive indole and pyrrole
compounds; a few methods described the F–C reaction of benzene
derivatives bearing highly electron-donating groups with nitro-
alkenes.10 Hence, there is need to develop a versatile F–C reaction,
which is applicable to undeveloped electron-rich arenes (benzene
derivatives). AlCl3 have been demonstrated as a versatile reagent
sessing a
-functionalities have been reported.21 So far, such com-
pounds have always been obtained by multistep synthesis,
involving routine reactions. Hence, hydroximoyl chlorides, which
Table 1
Arylation of
b
-nitrostyrene with anisole under various reaction conditions
NO2
NO2
reagent
+
for F–C reaction.11 However, its application with
b-nitrostyrene for
CH2Cl2, -78 °C
OCH3
F–C reaction has been rarely explored. Lambert et al.12 and Hurd
OCH3
et al.13 investigated the reaction of nitroalkenes with benzene in the
presence of aluminum chloride to obtain a-arylated hydroximoyl
Entry
Reagent (equiv)
Time (h)
Yielda (%)
chloride. However, their study was restricted to a limited number of
nitroolefins with benzene.
Nitrile oxides serves as 1,3-dipoles to undergo a variety of 1,3-
dipolar cycloaddition reactions with olefinic and acetylenic
1
2
3
4
5
6
7
AlCl3 (1.0)
AlCl3 (1.5)
AlCl3 (2.0)
FeCl3 (2.0)
BF3.OEt2 (2.0)
SnCl4 (2.0)
ZrCl4 (2.0)
6
6
4
12
12
12
12
58
71
87
0
0
0
0
* Corresponding author.
E-mail address: cheyaocf@ntnu.edu.tw (C.-F. Yao).
a
Isolated yield.
0040-4020/$ – see front matter Ó 2009 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2009.01.075

Z. Tu et al. / Tetrahedron 65 (2009) 2436–2442
2437
are precursors of nitrile oxides, have generated considerable in-
terest in organic synthesis.
2,2-Diphenethylamine and their derivatives possess biological
importance due to their ability to suppress adrenal steroid
biosynthesis in humans.7a,b Bridges et al. reported the synthesis of
2,2-diphenethylamines by the multistep synthesis starting from an
aromatic aldehyde.7c Usually 2,2-diphenethylamines were pre-
pared by reduction of the nitro moiety in 1,1-diphenyl-2-nitro-
ethane.7d Hence, 1,1-diphenyl-2-nitroethane is the important
building blocks for the synthesis of biologically important amines.
Table 2
AlCl3-induced arylation of
b-nitrostyrene with various arenes and heteroarenes
Earlier, a-arylated nitroalkanes were prepared by the 1,4-addition
NO2
of various organometallic reagents to nitroolefins.22 Recently,
Umera et al. utilized a mixture of salts (PdCl2/LiCl and BiCl3) for the
NO2
Ar
AlCl3/CH2Cl2
-78 °C, 4 h
a-arylation of b-nitrostyrenes. However, they were not able to
+
ArH
control the formation of homocoupled biaryl product along with
the desired adduct.23 In continuation of our research work on
nitroolefins,24 we have developed a newer route for the synthesis of
1a
2
Entry
1
Arene
Product
NO2
Yielda (%)
a-arylated nitroalkanes and a-arylated hydroximoyl chlorides from
conjugated nitroalkenes mediated by AlCl3.
OCH3
2a
87
2. Results and discussion
OCH3
25
11
NO2
As FeCl3
and AlCl3 are well known reagents for F–C alkyl-
-nitro-
ation reactions. We investigated the reaction between
b
2
3
2b
2c
76
71
styrene and anisole with 1 equiv of FeCl3 in CH2Cl2. Unfortunately,
we were not able to isolate any of the corresponding alkylated
products. Secondly, we tested the efficacy of AlCl3–CH2Cl2 system in
our alkylation reaction. We were pleased to find
hydroximoyl chloride 4a in quantitative yield. Further, we in-
NO2
CH3
a-arylated
vestigated the fate of the reaction at low temperatures. Conducting
CH3
the reaction at 0 ꢁC,
a-arylated hydroximoyl chloride 4a (74%) along
NO2
NO2
NO2
CH3
with
a-arylated nitroalkane (1-methoxy-4-(2-nitro-1-phenyl-
4
2d
2e
2f
70
50
ethyl)benzene) 2a (21%) was isolated. Further, upon decreasing the
temperature to ꢀ78 ꢁC, we found exclusively
a
-arylated nitro-
CH3
CH3
H3C
CH3
CH3
alkane (1-methoxy-4-(2-nitro-1-phenylethyl)benzene) 2a without
any additional products.
5
With this encouraging result in hand, we carried out the
optimization studies at ꢀ78 ꢁC varying the amount of AlCl3. With
1 equiv of AlCl3 afforded the product 2a in 58% yield, after 6 h
(entry 1, Table 1). By means of 1.5 equiv of aluminum chloride,
though product yields were improved to 71%, the reaction time is
almost same as that of 1 equiv. On the other hand, using 2 equiv of
AlCl3 as a reagent afforded the product in 87% yield in 4 h (entry
3). Various other potential Lewis acids such as FeCl3, BF3$OEt2,
SnCl4, and ZrCl4 were tested, the starting material was recovered
without any desired product. According to Table 1, the best yield
H3C
H3C
H3C
CH3
CH3
6
45
H3C
CH3
CH3
NO2
NO2
7
2g
2h
2i
89
of the
a-arylated products was obtained with AlCl3 (2 equiv) in
dichloromethane at ꢀ78 ꢁC. Similarly, this AlCl3–CH2Cl2 system
also holds good for the synthesis of
chloride at room temperature.
a-arylated hydroximoyl
8
78b
86
When 1.0 equiv of b-nitrostyrene 1a was reacted with 1.25 equiv
of arene in the presence of 2 equiv of AlCl3 using dry
NO2
H
N
H
9
N
Table 3
NO2
AlCl3-mediated alkylation of anisole with nitroolefins
NO2
10
11
2j
67
N
OCH3
H
NO2
NH
NO2
AlCl3/CH2Cl2
-78 °C,CH2Cl2
R
OCH3
R
S
1b-e
3a-d
2k
2l
80
28
S
Entry
R
Time (h)
Yielda (%)
NO2
1
2
3
4
Cl
(1b)
(1c)
(1d)
(1e)
4
2
3a
3b
3c
3d
77
90
69
NR
NO2
Me
OMe
12
S
7
12b
S
a
a
Isolated yield.
Isolated yield.
The reaction was prolonged for 24 h.
b
b
a
and b isomers were obtained.

2438
Z. Tu et al. / Tetrahedron 65 (2009) 2436–2442
dichloromethane as solvent at ꢀ78 ꢁC afforded
a
-arylated nitro-
ring (entries 3–7). The selectivity of the arylation was
alkanes 2 exclusively in moderate to good yields in 4 h.
controlled by both electronic and steric factors of the reactant.
For example, with toluene as the substrate, alkylation on the
arene occurred exclusively at para position with high efficiency
(entry 3, Table 2).
To further explore the scope and limitations of this meth-
odology, we tested various arenes under optimized conditions
(Table 2). As can be seen from Table 2, the arylation of
b
-nitrostyrene proceeds well with various aryl and heteroaryl
With polysubstituted substrate, such as mesitylene, the aryla-
tion proceeded with lower yields, which may arise from the severe
steric hindrance of the methyl groups (entry 6). AlCl3-induced
reactants. Excellent yields were obtained with activated arenes
such as anisole (entry 1). Other than benzene, various methyl-
substituted benzenes showed high reactivities, including those
with two or more methyl groups equipped on the benzene
arylation of
b-nitrostyrenes were found to be successful with
heteroarenes, e.g., pyrrole, indole, 2-methylthiophene, and
benzothiophene (entries 9–12) in good yields. The reaction failed
with the acid sensitive heteroarene substrates furan and
2-methoxyfuran. Obviously, the results shown provide an efficient
route for the synthesis of functionalized arenes with further elab-
oration of the nitro moiety.
Table 4
Synthesis of
a
-arylated hydroximoyl chlorides mediated by AlCl3
Cl
NOH
Ar
So as to utilize this effective protocol, we examined the
arylation reaction of structurally different
anisole. The reaction time varied according to the nature of the
substituent on -nitrostyrene. For example, the substrate
containing an electron-withdrawing group (Cl) in 4-chloro-
-nitrostyrene) (1b), was arylated to give the product (3a) in 4 h.
Similarly, with 4-nitro-( -nitrostyrene) (1c) containing strong
b-nitrostyrenes with
NO2
AlCl3/CH2Cl2
ArH
rt, 3 h
b
1a
4
(
b
Entry
1
Arene
Product
NOH
Yielda (%)
b
electron-withdrawing group (NO2), the reaction furnished the
product (3b) relatively in short time 2 h and high yield. This may
be attributed to the presence of electron-withdrawing groups (Cl
and NO2), which decrease the electron density on the phenyl
ring, thereby generating an electron deficient center at the ben-
Cl
4a
93
OCH3
NOH
Cl
zylic sp3 carbon of the
electrophilic attack on the electron-rich arene to give the corre-
sponding -arylated product. However, -nitrostyrene bearing
electron-donating group (Me) such as 4-methyl-( -nitrostyrene)
b-nitrostyrene. This species undergoes an
OCH3
2
3
4
5
4b
4c
4d
4e
4f
90
99
95
95
88
97
62
43
a
b
b
Cl
NOH
(1d) took longer time (7 h), whereas starting material was
recovered in case of 1-methoxy-4-(2-nitrovinyl) benzene (1e).
The results are summarized in Table 3.
CH3
CH3
Taking cues from our optimization studies, further we extended
Cl
Cl
Cl
NOH
NOH
CH3
the scope of our methodology toward the synthesis of
hydroximoyl chloride.
a-arylated
One equivalent of
arenes/heteroarenes in the presence of 2 equiv of AlCl3 using
dichloromethane as solvent at room temperature afforded
b-nitrostyrene 1a reacted with 1.25 equiv of
CH3
CH3
H3C
CH3
CH3
a
-
arylated hydroximoyl chlorides 4 without any additional products.
Apart from unactivated arene benzene, the reaction also proceeds
smoothly with activated arenes such as anisole, toluene, m,
p-xylene, mesitylene, and cumene (entries1–7, Table 4). The
H3C
H3C
H3C
NOH
CH3
CH3
reaction of
para substituted product in excellent yield. The arylation reaction
adducts of -nitrostyrene and heteroarenes e.g., thiophene, indole,
b-nitrostyrene with toluene gave predominately the
6
7
8
9
b
CH3
H3C
Cl
CH3
NOH
and benzothiophene (entries 8–10, Table 4) were also obtained
successfully in good yields.
4g
4h
4i
The mechanism probably involves the complexation of AlCl3
with
benzylic carbon of the activated
attack of this reactive species on the arene generates the
-complex (B), which upon protonation affords the intermediate
b
-nitrostyrene 1a, to generate a carbocationic center at
b-nitrostyrene (A). Electrophilic
Cl
NOH
S
S
s
(C). Elimination of AlCl2 gives the aci-nitro compound (D), which
at low temperature (ꢀ78 ꢁC) rearranges to give the corresponding
nitroalkane 2a.
At room temperature the formation of hydroximoyl chloride can
be explained in two plausible pathways starting from the
intermediate (C). Path A describes the formation of aci-nitro
compound (D), which further undergoes intramolecular oxidation
and reduction leading to form (E). The reaction of aluminum
chloride with (E) gives the hydroximoyl chloride.13 Path B can be
Cl
Cl
NOH
N
H
NH
NOH
10
4j
59
S
explained by the formation of
a-arylated nitroso derivative (G),
S
which upon chloride transfer gives the intermediate (F), further
tautomerizes to form hydroximoyl chloride 4a.
a
Isolated yield.

Z. Tu et al. / Tetrahedron 65 (2009) 2436–2442
OCH3
2439
H
H
OAlCl2
-
Ph
Cl
Cl
Cl
Cl
N
-
Al
Al
OAlCl2
Ph
Ph
O
O
Cl
Cl
N
O
N
O
-
(A)
(1a)
OCH3
(B)
H
H
Ph
OAlCl2
OH
NO2
Ph
N
NO2H
-78 °C
PathA
Ph
(B)
-AlCl2
OCH3
(2a)
OCH3
(C)
OCH3
(D)
Ph
Ph
-
NO2H
PathB
r.t.
-HOAlCl2
OCH3
r.t.
OH
-
Cl
H
H
Cl
N
O
NOH
Ph
Ph
N
C
O
+Cl-
+Cl-
OCH3
(E)
OCH3
OCH3
(G)
(F)
Cl
Ph
OH
N
OCH3
(4a)
3. Conclusion
a microscope hot-stage apparatus and uncorrected. 1H and 13C NMR
were recorded with Varian Gemini-200 or Bruker Avance EX 400 FT
In summary, we have developed a new and efficient AlCl3-me-
diated arylation reaction of -nitrostyrenes with various arenes/
heteroarenes under mild conditions. This procedure provides
NMR. Chemical shifts were reported in parts per million (d) using
b
TMS as internal standard, and coupling constants were expressed in
hertz. MS or HRMS were measured using a JEOL JMS-D300 or JEOL
JMS-HX 110 spectrometer.
a simple route toward the synthesis of
ꢀ78 ꢁC and
a
-arylated nitroalkanes at
a-arylated hydroximoyl chlorides at room temperature
employing the same reagent in moderate to good yields. The use of
readily available or cheap starting materials, inexpensive reagents
and wide range of arenes make this protocol an alternative to the
present existing methods.
4.2. General procedure for the arylation of
b-nitrosytrenes
with arenes mediated by aluminum chloride
In a 25 mL round bottom flask were first added b-nitrosytrene
(1 mmol), dry dichloromethane (4 mL) and anhydrous aluminum
chloride (2 mmol). The mixture was thoroughly degassed using
vacuum and nitrogenwas purged in cycles. The reaction mixturewas
stirred at ꢀ78 ꢁC, to this suspension, arene (1.25 mmol) was added
viaa syringe. Aftercompletion of the reaction as indicated by TLC, the
reaction mixture was quenched with an ice cold saturated sodium
chloride solution and extracted with dichloromethane (3ꢂ25 mL).
The combined organic layer was dried over anhydrous magnesium
sulfate and evaporated under reduced pressure to obtain the crude
mixture. The crude mixture was purified by flash chromatography
(ethyl acetate–hexane 1:20) to afford the desired pure product.
4. Experimental
4.1. General
All the reactions were performed in oven (130 ꢁC) dried glass-
ware under an inert atmosphere of argon unless otherwise speci-
fied. Solvents for extraction and chromatography were distilled
before use. Anhydrous solvents were obtained by following the
standard procedure. All the chemicals used in this study were of
commercial grade and used after distillation. Analytical thin layer
chromatography was performed with E. Merck silica gel 60 F254
aluminum plates. All purifications were carried out by flash chro-
matography using 230–400 mesh silica gel. AlCl3 was purchased
from the Acros Organics Co. Melting points were determined with
4.2.1. 1-Methoxy-4-(2-nitro-1-phenylethyl)benzene (2a)
Colorless oil (87% yield) 1H NMR (CDCl3)
d
7.33–7.20 (m, 5H), 7.13
(d, J¼8.72 Hz, 2H), 6.84 (d, J¼8.72 Hz, 2H), 4.95–4.82 (m, 2H), 3.74

2440
Z. Tu et al. / Tetrahedron 65 (2009) 2436–2442
(s, 3H). 13C NMR (100 MHz, CDCl3)
127.5, 127.4, 114.3, 79.4, 55.2, 48.2. MS m/z (relative intensity) 257
(Mþ, 11), 210 (100), 197 (51), 166 (46), 135 (22), 61 (29). HRMS calcd
for C15H15NO3 (Mþ) 257.1052, found 257.1055.
d
158.9, 139.5, 131.2, 128.9, 128.7,
6.16 (m, 1H), 6.0 (s, 1H), 5.01–4.96 (m, 1H), 4.90 (t, J¼7.48 Hz, 1H),
4.83–4.78 (m,1H). 13C NMR (CDCl3)
d 137.9,129.1,128.8,128.0,127.8,
118.1, 108.5, 105.7, 79.10, 42.8. MS m/z (relative intensity) 216 (Mþ,
15), 169 (100), 154 (32), 92 (8). HRMS calcd for C12H12N2O2 (Mþ)
216.0893, found 216.0886.
4.2.2. 1,1-Diphenyl-2-nitroethane (2b)7c
Colorless oil (76% yield) 1H NMR (CDCl3)
d
7.34–7.30 (m, 5H),
4.2.10. 3-(2-Nitro-1-phenylehtyl)-1H-indole (2j)
7.26–7.22 (m, 5H), 4.98 (d, J¼8.72 Hz, 2H), 4.92–4.88 (m, 1H). 13C
Colorless oil (67% yield) 1H NMR (CDCl3)
d 7.93 (s, 1H), 7.40 (d,
NMR (CDCl3)
d
139.1, 128.9, 127.5, 127.4, 79.0, 48.8.
J¼8.00 Hz, 1H), 7.27–7.10 (m, 8H), 6.82 (d, J¼2.36 Hz, 1H), 5.12
(dd, J¼8.36, 7.68 Hz, 1H), 4.95 (dd, J¼12.52, 7.68 Hz, 1H), 4.84 (dd,
4.2.3. 1-Methyl-4-(2-nitro-1-phenylethyl)benzene (2c)
Colorless oil (71%) 1H NMR (400 MHz, CDCl3)
7.33–7.22 (m, 5H),
7.12 (s, 4H), 4.97–4.84(m, 3H), 2.30(s, 3H);13C NMR (100 MHz, CDCl3)
J¼12.52, 8.36 Hz, 1H). 13C NMR (CDCl3)
d 139.1, 136.3, 128.7, 127.6,
d
127.4, 125.9, 122.3, 121.5, 119.7, 118.7, 113.9, 111.4, 79.3, 41.3. MS m/
z (relative intensity) 266 (Mþ, 8), 219 (100), 204 (44), 178 (19),
115 (11), 108 (17). HRMS calcd for C16H14N2O2 (Mþ) 266.1055,
found 266.1051.
d
139.5, 137.3, 136.2, 129.7, 129.0, 127.6, 127.5, 79.4, 48.6, 21.0; MS m/z
(relative intensity) 241 (Mþ, 1), 194 (100), 179 (52), 165 (24), 103 (11),
91 (10); HRMS calcd for C15H15NO2 (Mþ) 241.1103, found 241.1109.
4.2.11. 2-Methyl-5-(2-nitro-1-phenylethyl)thiophene (2k)
4.2.4. 2,4-Dimethyl-1-(2-nitro-1-phenylethyl)benzene (2d)
Colorless oil (80% yield) 1H NMR (CDCl3)
d
7.38–7.34 (m, 2H),
7.31–7.26 (m, 3H), 6.69–6.68 (m, 1H), 6.59–6.58 (m, 1H), 5.04–5.02
(m, 1H), 4.98–4.87 (m, 2H), 2.41 (s, 3H). 13C NMR (CDCl3)
140.0,
Colorless oil (70% yield) 1H NMR (CDCl3)
d
7.33–7.01 (m, 8H),
5.08 (t, J¼8.04 Hz, 1H), 5.00–4.89 (m, 2H), 2.30 (s, 3H), 2.29 (s, 3H).
13C NMR (CDCl3)
139.0, 137.1, 136.3, 134.1, 132.1, 128.9, 127.9, 127.4,
d
d
139.9, 139.0, 129.1, 128.0, 127.6, 125.1, 125.0, 79.9, 44.9, 15.3. MS m/z
(relative intensity) 247 (Mþ, 7), 211 (34), 199 (100), 184 (75), 153
(15), 102 (10), 76 (8). HRMS calcd for C13H13NO2S (Mþ) 247.0662,
found 247.0673.
127.0, 125.8, 79.3, 44.7, 20.9, 19.5. MS m/z (relative intensity) 255
(Mþ, 11), 209 (82), 193 (100), 178 (37), 105 (33), 77 (32). HRMS calcd
for C16H17NO2 (Mþ) 255.1259, found 255.1261.
4.2.5. 1,4-Dimethyl-2-(2-nitro-1-phenylethyl)benzene (2e)
4.2.12. 3-(2-Nitro-1-phenylethyl)benzo[b]thiophene (2l)
Colorless oil (50% yield) 1H NMR (CDCl3)
d
7.32–6.98 (m, 8H),
Colorless oil (28% yield) 1H NMR (CDCl3)
d 7.86–7.84 (m, 1H),
5.08 (dd, J¼8.64, 7.40 Hz, 1H), 4.97 (dd, J¼12.80, 7.40 Hz, 1H), 4.91
7.66–7.64 (m, 1H), 7.35–7.25 (m, 8H), 5.28 (dd, J¼8.24, 7.60 Hz, 1H),
(dd, J¼12.80, 8.64 Hz,1H), 2.32 (s, 3H), 2.26 (s, 3H). 13C NMR (CDCl3)
5.10 (dd, J¼12.84, 7.60 Hz, 1H), 4.96 (dd, J¼12.84, 8.24 Hz, 1H). 13C
d
138.9, 136.9, 135.8, 133.3, 131.1, 128.9, 128.1, 127.9, 127.4, 126.6,
NMR (CDCl3) d 140.6, 137.8, 137.6, 133.5, 129.2, 128.0, 127.8, 124.8,
79.2, 44.9, 21.2, 19.1. MS m/z (relative intensity) 255 (Mþ, 17), 210
(95), 193 (100), 178 (31), 165 (24), 103 (14). HRMS calcd for
C16H17NO2 (Mþ) 255.1259, found 255.1260.
124.4, 122.9, 122.6, 121.8, 79.0, 43.5. MS m/z (relative intensity) 283
(Mþ, 40), 226 (100), 221 (37), 204 (29),115 (17), 61 (35). HRMS calcd
for C16H13NO2S (Mþ) 283.0667, found 283.0668.
4.2.6. 1,3,5-Trimethyl-2-(2-nitro-1-phenylethyl)benzene (2f)
4.2.13. 1-Chloro-4-(1-(4-methoxyphenyl)-2-nitroethyl)
Colorless oil (45% yield) 1H NMR (CDCl3)
d
7.30–7.20 (m, 3H),
benzene (3a)
7.05 (d, J¼7.28 Hz, 2H), 6.86 (s, 2H), 5.52 (dd, J¼8.00, 6.80 Hz, 1H),
Colorless oil (77% yield) 1H NMR (CDCl3)
d
7.32–7.29 (m, 2H),
7.17–7.11 (m, 4H), 6.87–6.85 (m, 2H), 4.93–4.90 (m, 2H), 4.86–4.81
(m, 1H), 3.78 (s, 3H). 13C NMR (CDCl3)
159.3, 138.3, 133.6, 130.9,
5.33 (dd, J¼12.84, 8.00 Hz, 1H), 4.89 (dd, J¼12.84, 6.80 Hz, 1H), 2.26
(s, 3H), 2.20 (s, 6H). 13C NMR (CDCl3)
d
139.6, 137.2, 137.0, 133.4,
d
130.4, 128.8, 126.7, 126.4, 77.8, 42.1, 21.0, 20.8. MS m/z (relative in-
tensity) 269 (Mþ, 18), 223 (37), 207 (100), 192 (33), 135 (47), 91 (21).
HRMS calcd for C17H19NO2 (Mþ) 269.1410, found 269.1416.
129.4, 129.1, 128.8, 114.7, 79.4, 55.5, 47.8. MS m/z (relative intensity)
291 (Mþ, 11), 244 (100), 230 (28), 178 (15), 166 (25), 152 (19), 139
(6), 76 (4). HRMS calcd for C15H14ClNO3 (Mþ) 291.0657, found
291.0665.
4.2.7. 1-Isopropyl-4-(2-nitro-1-phenylethyl)benzene (2g)
Colorless oil (89% yield) 1H NMR (CDCl3)
d
7.33–7.23 (m, 5H),
7.18–7.13 (m, 5H), 4.97 (d, J¼8.8 Hz, 2H), 4.89–4.85 (m, 1H), 2.88–
2.84 (m, 1H), 1.22 (s, 3H), 1.20 (s, 3H). 13C NMR (CDCl3)
148.1, 139.4,
4.2.14. 1-Methoxy-4-(2-nitro-1-(4-nitrophenyl)ethyl)benzene (3b)
Colorless oil (90% yield) 1H NMR (CDCl3)
d
8.20 (d, J¼8.76 Hz,
d
2H), 7.43 (d, J¼8.72 Hz, 2H), 7.13 (d, J¼8.68 Hz, 2H), 6.89 (d,
136.4, 128.9, 127.6, 127.5, 127.4, 127.2, 126.9, 79.2, 48.6, 33.6, 23.8.
MS m/z (relative intensity) 269 (Mþ, 5), 206 (100),177 (62),165 (57),
118 (32), 102 (27), 91 (32), 77 (13). HRMS calcd for C17H19NO2 (Mþ)
269.1410, found 269.1403.
J¼8.72 Hz), 5.02–5.01 (m, 2H), 4.99–4.95 (m, 1H), 3.78 (s, 3H). 13C
NMR (CDCl3)
d 159.6, 147.1, 147.0, 129.8, 128.9, 128.7, 124.4, 114.9,
78.86, 55.5, 48.1. MS m/z (relative intensity) 302 (Mþ, 17), 254 (100),
241 (38), 191 (12), 132 (20), 115 (16), 77 (6). HRMS calcd for
C15H14N2O5 (Mþ) 302.0903, found 302.0909.
4.2.8. 1-(2-Nitro-1-phenylehtyl)naphthalene (2h)
Colorless oil (78% yield) 1H NMR (400 MHz, CDCl3)
d
7.89–7.87
4.2.15. 1-Methoxy-4-(2-nitro-1-p-tolylethyl)benzene (3c)
(m, 1H), 7.84–7.72 (m, 4H), 7.54–7.45 (m, 6H), 7.37–7.26 (m, 13H),
Colorless oil (69% yield). 1H NMR (CDCl3)
d
7.15–7.09 (m, 5H),
6.85–6.81 (m, 3H), 4.93 (d, J¼8.4 Hz, 2H), 4.83 (t, J¼8.2 Hz, 1H), 3.76
(s, 3H), 2.33 (s, 3H). 13C NMR (CDCl3)
159.2, 137.5, 136.8, 131.8,
5.79 (t, J¼8 Hz, 1H), 5.16–5.04 (m, 5H). 13C NMR (100 MHz, CDCl3)
d
139.0, 138.9, 136.6, 134.6, 134.1, 133.3, 132.6, 131.1, 129.1, 129.0,
d
128.9, 128.4, 127.9, 127.8, 127.7, 127.6, 126.7, 126.4, 126.2, 126.0,
125.9, 125.8, 125.2, 124.2, 123.0, 79.1, 79.0, 48.9, 44.6. MS m/z (rel-
ative intensity) 277 (Mþ, 51), 229 (100), 216 (80), 214 (50), 203 (22),
190 (5), 152 (89), 114 (14), 101 (11). HRMS calcd for C18H15NO2 (Mþ)
277.1097, found 277.1099.
129.9, 128.9, 127.7, 114, 79.9, 55.5, 48.2, 21.3. MS m/z (relative in-
tensity) 271 (Mþ, 13), 223 (100), 210 (45), 208 (17), 166 (12), 115 (6),
105 (3). HRMS calcd for C16H17NO3 (Mþ) 271.1203, found 271.1218.
4.3. General procedure for the synthesis of
hydroximoyl chloride
a-arylated
4.2.9. 2-(2-Nitro-1-phenylethyl)-1H-pyrrole (2i)
Black solid (86% yield) Mp 73 ꢁC. 1H NMR (CDCl3)
d
7.84 (br s,
The 25 mL round bottom flask was cooled to 0 ꢁC containing
nitrostyrene (1 mmol) and anhydrous aluminum chloride (2 mmol)
b-
1H), 7.38–7.29 (m, 3H), 7.26–7.23 (m, 2H), 6.69–6.68 (m, 1H), 6.18–

Z. Tu et al. / Tetrahedron 65 (2009) 2436–2442
2441
in 4 mL of dry dichloromethane. To this stirred suspension
1.25 mmol of arene was added via a syringe, all the additions were
carried out at 0 ꢁC. After complete addition, the ice bath was re-
moved and stirring was continued at room temperature for 3 h.
After completion of the reaction as indicated by TLC, the reaction
mixture was quenched with an ice cold saturated sodium chloride
solution and extracted with dichloromethane (3ꢂ25 mL). The or-
ganic fraction was dried over anhydrous magnesium sulfate and
evaporated to give the crude product, which was purified by flash
chromatography using ethyl acetate and hexane to obtain the cor-
responding hydroximoyl chloride.
221 (100), 206 (24), 191 (13), 178 (9), 165 (6), 152 (2), 143 (11), 128
(5), 115 (11), 103 (1), 91 (4), 77 (2). HRMS calcd for C17H18ClNO (Mþ)
287.1077, found 287.1082.
4.3.7. N-Hydroxy-2-(4-isopropylphenyl)-2-phenyl acetimidoyl
chloride (4g)
Colorless solid (97% yield). Mp 116 ꢁC. 1H NMR (CDCl3)
d
7.73 (s,
1H), 7.34–7.15 (m, 10H), 5.22 (s, 1H), 2.90 (m, 1H), 1.24 (d, J¼6.92 Hz,
6H). 13C NMR (CDCl3)
148.04, 143.45, 138.69, 135.71, 129.00,
d
128.87, 128.53, 127.40, 126.63, 57.98, 33.68, 23.89. MS m/z (relative
intensity) 289 ((Mþ2)þ, 5), 287 (Mþ, 15), 268 (24), 251 (4), 228 (6),
222 (19), 221 (100), 191 (12), 178 (35), 165 (17), 152 (7), 128 (7), 115
(11), 97 (11), 91 (17), 71 (20), 57 (24). HRMS calcd for C17H18ClNO
(Mþ) 287.1077, found 287.1079.
4.3.1. N-hydroxy-2-(4-methoxyphenyl)-2-phenyl acetimidoyl
chloride (4a)
Colorless solid (93% yield). Mp 163 ꢁC. 1H NMR (CDCl3)
d
7.65 (s,
1H), 7.34–7.15 (m, 8H), 6.87 (d, J¼6.72 Hz, 2H), 5.21 (s, 1H), 3.81 (s,
3H). 13C NMR (CDCl3)
158.87, 143.58, 138.80, 130.51, 130.11, 128.88,
4.3.8. N-Hydroxy-2-phenyl-2-(thiophen-2-yl)acetimidoyl chloride
d
(4h)
128.55, 127.40, 113.97, 57.55, 55.24. MS m/z (relative intensity) 277
((Mþ2)þ, 4), 275 (11), 258 (4), 239 (5), 223 (11), 209 (100), 194 (26),
178 (14),165 (47),153 (17),139 (7),115 (5),102 (3), 91 (10), 77 (6), 51
(2). HRMS calcd for C15H14NClO2 (Mþ) 275.0713, found 275.0709.
Colorless solid (62% yield). Mp 123 ꢁC. 1H NMR (CDCl3)
d
8.26 (s,
1H), 7.29–7.39 (m, 5H), 7.28–7.25 (m, 1H), 6.99–6.96 (m, 1H), 6.93–
6.92 (m, 1H), 5.45 (s, 1H). 13C NMR (CDCl3)
142.72, 141.14, 138.25,
d
128.70, 128.53, 127.95, 127.04, 126.71, 125.60, 53.42. MS m/z (rela-
tive intensity) 253 ((Mþ2)þ, 10), 251 (Mþ, 27), 236 (4), 234 (10), 207
(6),199 (17),185 (100),184 (63),173 (34),171 (20),152 (14),141 (11),
115 (9), 89 (4), 77 (6), 63 (3), 51 (3). HRMS calcd for C12H10ClNOS
(Mþ) 251.0172, found 251.0169.
4.3.2. N-Hydroxy-2,2-diphenylacetimidoylchloride (4b)
Colorless solid (90% yield). Mp 110 ꢁC. 1H NMR (CDCl3)
d
7.70 (s,
1H), 7.36–7.30 (m, 5H), 7.29–7.24 (m, 5H), 5.25 (s, 1H). 13C NMR
(CDCl3)
d 143.4, 138.5, 129.0, 128.6, 127.6, 58.4. MS m/z (relative
intensity) 245 (Mþ, 100), 229 (39), 193 (37), 178 (89), 166 (70), 125
(35), 89 (12), 82 (16). HRMS calcd for C14H12ClNO (Mþ) 245.0602,
found 245.0595.
4.3.9. N-Hydroxy-2-(indolin-3-yl)-2-phenylacetimidoyl
chloride (4i)
Colorless solid (43% yield). Mp 150 ꢁC. 1H NMR (CDCl3)
d 8.08 (s,
1H), 7.71 (s, 1H), 7.44–7.20 (m, 8H), 7.09 (t, J¼7.92 Hz, 1H), 6.94 (d,
4.3.3. N-Hydroxy-2-phenyl-2-p-tolylacetimidoyl chloride (4c)
J¼2.40 Hz,1H), 5.48 (s,1H). 13C NMR (CDCl3)
d 143.23,138.41,136.27,
Colorless solid (99% yield). Mp 125 ꢁC. 1H NMR (CDCl3)
d
8.27 (s,
128.69, 128.56, 127.49, 126.47, 123.69, 122.49, 119.89, 119.27, 114.18,
111.30, 50.33. MS m/z (relative intensity) 286 ((Mþ2)þ, 4), 284 (Mþ,
13), 248 (11), 232 (11), 218 (100), 206 (11),191 (28),178 (10),165 (4),
155 (10), 151 (4), 141 (2), 128 (4), 108 (4), 89 (4), 77 (5), 57 (3). HRMS
calcd for C16H13Cl N2O (Mþ) 284.0716, found 284.0715.
1H), 7.33–7.09 (m, 9H), 5.18 (s, 1H), 2.31 (s, 3H). 13C NMR (CDCl3)
d
143.4, 138.6, 137.2, 135.4, 129.3, 128.9, 128.8, 128.6, 127.4, 58.0,
21.0. MS m/z (relative intensity) 261 ((Mþ2)þ,12), 259 (Mþ, 34), 242
(19), 224 (9), 207 (21), 193 (100), 178 (59), 165 (34),139 (11), 125 (8),
115 (24), 102 (4), 89 (9), 65 (3), 57 (3). HRMS calcd for C15H14ClNO
(Mþ) 259.0764, found 259.0768.
4.3.10. 2-(2,3-Dihydrobenzo[b]thiophen-3-yl)-N-hydroxy-2-
phenylacetimidoyl chloride (4j)
4.3.4. 2-(2,4-Dimethylphenyl)-N-hydroxy-2-phenyl acetimidoyl
Colorless solid (59% yield). Mp 130 ꢁC. 1H NMR (CDCl3)
d 7.87–
chloride (4d)
7.84 (m,1H), 7.73 (s,1H), 7.61–7.59 (m,1H), 7.39–7.31 (m, 7H), 7.12 (d,
Colorless solid (95% yield). Mp 152 ꢁC. 1H NMR (CDCl3)
d
7.35-
7.00 (m, 7H), 6.89 (s, 1H), 5.31 (s, 1H), 2.29 (s, 3H), 2.22 (s, 3H). 13C
NMR (CDCl3) 143.23, 137.96, 136.66, 135.57, 133.34, 130.61, 129.16,
129.12, 128.56, 128.29, 127.39, 55.55, 21.15, 19.14. MS m/z (relative
intensity) 273 (Mþ, 8), 256 (8), 238 (60), 220 (19), 208 (21), 207
(100),192 (41),165 (28),152 (7),129 (33),115 (36), 91 (10), 77 (8), 57
(6). HRMS calcd for C16H16ClNO (Mþ) 273.0920, found 273.0921.
J¼0.68 Hz,1H), 5.51 (s,1H). 13C NMR (CDCl3)
d 142.09,140.39,137.31,
137.90, 133.36, 128.84, 127.93, 125.47, 124.63, 124.34, 122.98, 121.95,
52.76. MS m/z (relative intensity) 303 ((Mþ2)þ, 4), 301 (Mþ, 77), 284
(31), 249 (46), 235 (100), 221 (62), 178 (17), 158 (6), 125 (12), 88 (9).
HRMS calcd for C16H12ClNOS (Mþ) 301.0328, found 301.0323.
d
Acknowledgements
4.3.5. 2-(2,5-Dimethylphenyl)-N-hydroxy-2-phenyl acetimidoyl
Financial support provided by the National Science Council of
the Republic of China and National Taiwan Normal University
(96TOP001) is gratefully acknowledged.
chloride (4e)
Colorless solid (95% yield). Mp 130 ꢁC. 1H NMR (CDCl3)
d
7.70 (s,
1H), 7.39–6.96 (m, 8H), 5.30 (s, 1H), 2.30 (s, 3H), 2.24 (s, 3H). 13C
NMR (CDCl3) 143.23, 137.96, 136.66, 135.57, 133.34, 130.61, 129.16,
d
129.12, 128.56, 128.29, 127.39, 55.55, 21.15, 19.14. MS m/z (relative
intensity) 273 (Mþ, 4), 268 (10), 256 (5), 238 (100), 220 (28), 207
(94), 192 (42), 178 (34), 165 (31), 160 (17), 132 (8), 129 (41), 115 (51),
105 (19), 91 (21), 88 (29), 73 (26), 70 (60), 61 (66). HRMS calcd for
C16H16ClNO (Mþ) 273.0920, found 273.0915.
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