Iridium-Catalyzed Direct C-H Sulfamidation of Aryl Nitrones with Sulfonyl Azides at Room Temperature

Article abstract of DOI:10.1021/acs.joc.5b01377

Ir(III)-catalyzed direct C-H sulfamidation of aryl nitrones has been developed to synthesize various sulfamidated nitrones in moderate to excellent yields with excellent regioselectivity and broad functional group tolerance. This transformation could proceed smoothly at room temperature with low catalyst loading in the absence of external oxidants, acids, or bases. Molecular nitrogen was released as the sole byproduct, thus providing an environmentally benign sulfamidation process. And this protocol could efficiently apply to synthesize the substituted benzisoxazoline via one-step transformation from the product.

Full text of DOI:10.1021/acs.joc.5b01377

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Iridium-Catalyzed Direct C−H Sulfamidation of Aryl Nitrones with
Sulfonyl Azides at Room Temperature
Chao Pi,† Xiuling Cui,*,†,‡ and Yangjie Wu*,†
†College of Chemistry and Molecular Engineering, Henan Key Laboratory of Chemical Biology and Organic Chemistry, Key
Laboratory of Applied Chemistry of Henan Universities, Zhengzhou University, Zhengzhou 450052, P. R. China
‡School of Biomedical Sciences, Engineering Research Centre of Molecular Medicine of Chinese Education Ministry, Xiamen Key
Laboratory of Ocean and Gene Drugs, Institute of Molecular Medicine of Huaqiao University, Xiamen 361021, Fujian, P. R. China
S
* Supporting Information
ABSTRACT: Ir(III)-catalyzed direct C−H sulfamidation of aryl
nitrones has been developed to synthesize various sulfamidated
nitrones in moderate to excellent yields with excellent regioselec-
tivity and broad functional group tolerance. This transformation
could proceed smoothly at room temperature with low catalyst
loading in the absence of external oxidants, acids, or bases.
Molecular nitrogen was released as the sole byproduct, thus
providing an environmentally benign sulfamidation process. And
this protocol could efficiently apply to synthesize the substituted
benzisoxazoline via one-step transformation from the product.
alkynes.3 In particular, 2-aminoaryl nitrones containing dual
functional groups of amino and nitrone groups are especially
valuable because they are readily modifiable. Anthranilic acid
INTRODUCTION
■
Arylnitrone scaffold is of great importance in organic synthesis
and can be easily converted into various heterocycles via diverse
sulfonamides (E, Scheme 1c), accessed from compound D,
transformation.1 For instance, substituted β-lactams (A) and
have been evaluated as human MetAP2 inhibitors with potent
benzisoxazolines (B, Scheme 1a) directly obtained from
activities against the enzyme and against HMVEC prolifer-
nitrones are important synthetic building blocks and have
ation.4,5 Therefore, the development of a practical approach to
been found in a number of biological molecules.2 Indenone (C,
Scheme 1b), a useful skeleton in synthetic chemistry,
pharmaceuticals, and material science, could be accessed by
rhodium-catalyzed C−H annulation of nitrones with internal
introduce amine groups into the nitrone motif is highly
important and desirable.
Employing copper mediators for the activation of aryl
(pseudo)halides to react with amine as initiated by Ullmann
and Goldberg has been developed.6 Later, Buchwald and
Scheme 1. Examples Illustrating the Importance of Nitrones
Hartwig independently developed the Pd- and Cu-catalyzed
amination starting from (hetero)aryl halides or their pseudos.7
Recently, a direct C−N bond formation based on transition-
metal-catalyzed C−H bond activation has been developed.8
However, stoichiometric or excessive external oxidants are
required in most cases. To avoid the external oxidants,
preactivated amino precursors have been employed as the
starting materials.9 However, an additional step is needed to
prepare the amine reagent, and stoichiometric byproducts are
still generated. To overcome the current limitations, an
environmentally benign direct C−H amidation has led chemists
to search for alternative approaches. As a consequence, organic
azides have been developed as an amino source and internal
oxidant by N−N2 bond cleavage, providing environmentally
benign methods for the direct C−H amination10−12 (Scheme
2a). Transition-metal-catalyzed directed C−H amination by
chelating groups has been successfully developed.10−12 In
Received: June 17, 2015
© XXXX American Chemical Society
A
DOI: 10.1021/acs.joc.5b01377
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The Journal of Organic Chemistry
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a
Scheme 2. Transition-Metal-Catalyzed C−H Amination
from Organic Azides
Table 1. Optimization of the Reaction Conditions
T
time
(h)
yield
(%)
entry
1
catalyst
solvent
(°C)
[IrCp*Cl2]2/AgNTf2
[IrCp*Cl2]2/AgNTf2
[IrCp*Cl2]2/AgNTf2
[IrCp*Cl2]2/AgNTf2
[IrCp*Cl2]2/AgNTf2
[IrCp*Cl2]2/AgSbF6
[IrCp*Cl2]2/AgBF4
[IrCp*Cl2]2/AgNTf2
[IrCp*Cl2]2/AgNTf2
[IrCp*Cl2]2/AgNTf2
[IrCp*Cl2]2/AgNTf2
[IrCp*Cl2]2/AgNTf2
[IrCp*Cl2]2/AgNTf2
[IrCp*Cl2]2/AgNTf2
[IrCp*Cl2]2/AgNTf2
[IrCp*Cl2]2/AgNTf2
Pd(OAc)2
1,2-DCE
1,2-DCE
1,2-DCE
1,2-DCE
1,2-DCE
1,2-DCE
1,2-DCE
toluene
THF
50
50
50
50
25
25
25
25
25
25
25
25
25
25
25
25
80
25
12
12
12
6
75
60
n.r.
86
96
79
67
26
40
n.r.
n.r.
n.r.
80
95
55
85
n.r.
n.r.
b
2
c
3
4
5
6
6
6
7
6
particular, Chang and co-workers have extensively studied the
Ir-catalyzed amidation reactions under mild reaction con-
ditions.12 However, the directing groups reported in the
literature were not easily removed or modified. This short-
coming can be attenuated if the chelation groups are converted
into other desired functional groups of the synthetic target after
the C−H functionalization step. We have developed quinoline
N-oxides as internal oxidants and utilized a redox process with
ferrocene,13 avoiding external oxidants. As part of our
continuing work, we herein embarked on the development of
a highly efficient and selective iridium-catalyzed direct C−H
sulfamidation of aryl nitrones using sulfonyl azides as the
starting materials and avoiding external oxidants (Scheme 2b).
Importantly, this transformation could proceed smoothly at
room temperature with low catalyst loading, which would make
it a potential application in industry.
8
6
9
6
10
11
12
13
CH3CN
CH3OH
DMF
6
6
6
DME
6
d
14
e
1,2-DCE
1,2-DCE
1,2-DCE
1,2-DCE
1,2-DCE
6
15
6
16
3
f
17
g
12
6
18
[Ru(p-cymene)Cl2]2/
AgSbF6
19
20
[RhCp*Cl2]2/AgSbF6
[RhCp*Cl2]2/AgSbF6
[Ru(p-cymene)Cl2]2/
AgSbF6
1,2-DCE
1,2-DCE
1,2-DCE
25
80
80
6
12
12
n.r.
82
70
g
21
22
[Ru(p-cymene)Cl2]2/
AgSbF6
1,2-DCE
80
12
n.r.
RESULTS AND DISCUSSION
a
■
1a (0.2 mmol), 2a (0.22 mmol), [IrCp*Cl2]2 (2 mol %), AgNTf2 (8
mol %), additive (0.3 equiv), solvent (1.0 mL), under air. PivOH as
additive. NaOAc as additive. [IrCp*Cl2]2 (1 mol %), AgNTf2 (4 mol
%). [IrCp*Cl2]2 (0.5 mol %), AgNTf2 (2 mol %). 2 equiv of K2S2O8
b
The condensation of N-tert-butyl-α-phenylnitrone (1a) with p-
toluenesulfonyl azide (2a) was initially chosen as a model
reaction to screen various reaction parameters (Table 1). To
our great delight, the desired product 3aa was isolated in 75%
yield in the presence of [IrCp*Cl2]2 (2 mol %) in 1,2-DCE
(1,2-dichloroethane) using AgNTf2 as an additive after 12 h at
50 °C (entry 1), the molecular structure of the product 3aa was
further confirmed by single-crystal X-ray diffraction analysis,14
and the configuration is shown in Figure 1 in the Supporting
Information. The yield decreased slightly in the presence of
PivOH (entry 2). The procedure was shut down using NaOAc
as an additive (entry 3). When the reaction time was decreased
to 6 h, the yield was improved to 86% (entry 4). In view of the
fact that high temperature might lead to decomposition of the
product, the reaction temperature was decreased from 50 to 25
°C, affording a higher yield of 96% (entry 5). Among various
silver salts tested, AgNTf2 gave the best yield (entries 5−7). We
then examined the nonpolar or polar solvents and found that
this reaction did not work in DMF (N,N-dimethylformamide),
acetonitrile, or methanol, but 1,2-DCE gave the highest yield
(entries 8−13). A similar yield (95%) could be obtained with as
low as 1 mol % catalyst loading (entry 14). Further reducing
the loading of catalyst or shortening the reaction time led to
lower efficiencies (entries 15 and 16). Pd(OAc)2 showed
almost no catalytic activity in this reaction (entry 17). No
desired product was detected in the presence of [RhCp*Cl2]2
or [Ru(p-cymene)Cl2]2 with copper at 25 °C (entries 18 and
19, Table 1). Elevating the reaction temperature to 80 °C and
prolonging the reaction time to 12 h resulted in 82% and 70%
c
d
e
f
g
was used. Cu(OAc)2 as additive (0.3 equiv).
yields, respectively (entries 20 and 21, Table 1). [Ru(p-
cymene)Cl2]2 did not work without copper, even under higher
temperature and longer reaction time (entry 22). Finally, the
optimized reaction conditions were identified as follows: 1 mol
% of [IrCp*Cl2]2, 4 mol % of AgNTf2, and 1.1 equiv of p-
toluenesulfonyl azide 2a in 1,2-DCE under air at 25 °C for 6 h.
With the optimized reaction conditions, the scope of sulfonyl
azides was then examined in the sulfamidation of N-tert-butyl-
α-phenylnitrone (Scheme 3). It was found that the electron
density of arensulfonyl azides did not have significantly
influence on this transformation, and the bisamidated products
were not detected. Aromatic rings substituted with electron-
donating and electron-withdrawing groups were readily
sulfamidated at the ortho-position and provided the desired
products in excellent yields for all most cases (3aa−ai).
Moderate product yield was obtained for 4-nitrobenzenesul-
fonyl azide (3aj). In addition, broad functional groups were also
tolerated. For instance, arensulfonyl azides bearing fluoro
(3ae), chloro (3af), bromo (3ag), or ketone (3ai) groups were
smoothly sulfamidated in excellent yields. Aliphatic sulfonyl
azides also worked well. Ethylsulfonyl azide and benzylsulfonyl
azide afforded the corresponding products 3ak and 3al in 94%
yields, respectively. Naphthalene-2-sulfonyl azide was a suitable
substrate and gave the corresponding sulfamidated product
B
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a
65% yield. For aryl nitrone with a smaller F group at the meta-
position, C−H sulfamidation occurred at two sites, giving the
major product (3ka) and the minor product (3ka′) in 95%
total yield with a ratio of 8:1. No reaction was observed for
pyridyl nitrone, furyl nitrone, and thienyl nitrone under the
standard reaction conditions.
Scheme 3. Scope of Substrates
To demonstrate the synthetic potential application of the
present method, the sulfamidation of 1a on a gram scale was
attempted. The sulfamidated nitrone 3aa was obtained with
90% yield (eq 1, Scheme 4). Substituted benzisoxazoline 5
Scheme 4. Gram-Scale Sulfamidation of 1a and
Transformation of Amidated Product
could be synthesized by the [3 + 2] cycloaddition of arynes 4
and sulfamidated nitrones 3aa obtained from our methodology,
providing 62% yield (eq 2, Scheme 4). In comparison with
traditional methods, the current reaction provided an easier,
more direct, and step-economic method to various benzisox-
azoline derivatives with important biological and pharmaco-
logical activities.15
To gain insight into the mechanism of this transformation,
the controlled experiments were carried out. The desired
product was not obtained when the condensation of N-
benzylidene-2-methylpropan-2-amine (1a′) with p-toluenesul-
fonyl azide (2a) was processed under the standard conditions,
which indicated that iridacycle intermedium was formed by the
coordination of the iridium atom with the O atom rather than
N atom, and the N-oxide moiety was necessary for this
transformation (Scheme 5).
a
Reaction conditions: 1 (0.2 mmol), 2 (0.22 mmol), [IrCp*Cl2]2 (1
mol %), AgNTf2 (4 mol %) in DCE (1.0 mL) at 25 °C for 6 h under
air. At 50 °C. At 50 °C for 10 h.
b
c
3am in 98% yield. Arensulfonyl azide bearing a nitro group at
meta-position could readily participate in the sulfamidation
reaction, providing product 3an in 92% yield. Arensulfonyl
azide with o-methyl group slightly decreased the reactivity,
presumably due to steric hindrance. When the reaction
temperature was raised to 50 °C, the desired products 3ao
and 3ap were obtained in 95% and 82% yields, respectively.
2,4,6-Trimethylbenzenesulfonyl azide delivered the desired
product 3aq in only 27% yield, even performed at 50 °C. In
addition, thiophene-2-sulfonyl azide afforded the corresponding
product 3ar in 94% yield. Trace amounts of desired product
were detected when benzoyl azide was employed as a substrate
under the standard reaction conditions.
Scheme 5. Control Experiment
We next investigated a range of aryl nitrones to react with p-
toluenesulfonyl azide (2a) under the optimized conditions
(Scheme 3). Ortho-sulfamidated products with electron-
donating substituents, such as methyl (3ba) or methoxy
(3ca), were obtained in 91% and 81% yields, respectively. N-
tert-Butyl-α-phenyl nitrone substituted with 4-phenyl could also
be employed for this conversion and smoothly provided the
target product (3da) in 84% yield. In addition, substrates
bearing electron-withdrawing groups, such as fluoro (3ea),
chloro (3fa), or trifluoromethyl (3ga) groups were all
sulfamidated in good yields. Excitingly, C−H sulfamidation of
aryl nitrones substituted with methyl group at the ortho (3ha)
or meta position (3ia) occurred selectively at the position with
lower steric hindance in excellent yield. N-tert-Butyl-α-
piperonyl nitrone gave the corresponding product (3ja) in
On the basis of the above experimental results and literature
results,12,16 the reaction mechanism was proposed as shown in
Scheme 6. First, the dimeric precursor [IrCp*Cl2]2 was
converted into a cationic species with the aid of silver salt.
The six-membered iridacycle I3,17 with one vacant accessible
site was formed by the coordination of the iridium atom with
the O atom and subsequently electrophilically attacked at the
ortho-position C atom. Then, intermediate II was prepared by
azide interacting with the cationic metal center. It was proposed
that an iridium nitrenoid species III from complex II occurs in
an oxidative manner to release N2 molecule.18 A new C−N
bond of IV was formed by insertion of the nitrenoid species
C
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mL) equipped with a magnetic stirrer bar was charged with aldehyde
(5 mmol), N-methylhydroxylamine hydrochloride (5 mmol), anhy-
drous MgSO4 (1.0 g), NaHCO3 (0.55 g), and 1,2-dichlorothane (30
mL). The reaction mixture was stirred under reflux for 24 h. After
filtration and removal of solvents, the crude product was purified by
flash chromatography on silica gel.
Scheme 6. Proposed Reaction Mechanism
General Procedure for Iridium-Catalyzed C−H Sufamidation
of Arylnitrones with Sulfonyl Azides. Under air atmosphere, a
reaction tube (25 mL) equipped with a magnetic stirrer bar was
charged with aryl nitrone (1, 0.2 mmol), sulfonyl azide (2, 0.22
mmol), [IrCp*Cl2]2 (1.6 mg, 0.02 mmol, 1 mol %), AgNTf2 (3.1 mg,
0.08 mmol, 4 mol %), and 1,2-dichloroethane (1.0 mL). The reaction
mixture was stirred at room temperature for 6 h, filtered through a pad
of Celite, and then washed with CH2Cl2 (10 mL × 3). The solvents
were removed under reduced pressure, and the residue was purified by
chromatography on silica gel (elute: EtOAc/petroleum ether/NEt3) to
give the desired product 3.
(Z)-2-Methyl-N-(2-(4-methylphenylsulfonamido)benzylidene)-
propan-2-amine oxide (3aa): 65.7 mg, 95%; white solid; mp 151−
1
153 °C; H NMR (400 MHz, CDCl3) δ 10.54 (br, 1H), 7.59 (d, J =
3.5 Hz, 2H), 7.55 (s, 1H), 7.47 (d, J = 8.2 Hz, 1H), 7.42−7.38 (m,
1H), 7.19 (d, J = 8.1 Hz, 2H), 7.15 (d, J = 4.2 Hz, 2H), 2.38 (s, 3H),
1.55 (s, 9H); 13C {1H} NMR (100 MHz, CDCl3) δ 142.9, 138.0,
137.9, 134.2, 131.6, 131.2, 129.3, 126.8, 124.9, 124.5, 123.6, 71.2, 28.2,
21.5; IR (KBr, cm−1): 3430, 3127, 2978, 1600, 1492, 1400, 1326, 1161,
1129, 1092, 925, 890, 845, 802, 775, 723, 665, 548, 434; HRMS (ESI)
calcd for C18H23N2O3S+ [M + H]+ m/z 347.1424, found 347.1427.
(Z)-N-(2-(4-tert-Butylphenylsulfonamido)benzylidene)-2-methyl-
propan-2-amine oxide (3ab): 76.1 mg, 98%; white solid; mp 192−
into iridacycle. Finally, compound IV was protodemetalated to
deliver the sulfamidated product 3.
CONCLUSIONS
■
1
In summary, we have developed an iridium-catalyzed direct
sulfamidation of aryl nitrones, employing sulfonyl azides as an
amino source and internal oxidant. A series of sulfamidated
nitrones were prepared in excellent yields with good functional
group tolerance at room temperature. In this approach, external
oxidants, acids or bases were avoided and N2 was released as
the sole byproduct, thus providing an environmentally benign
sulfamidation process. The present protocol is anticipated to be
an important approach to nitrones, which would be useful to
build multitudinous biologically active molecules.
195 °C; H NMR (400 MHz, CDCl3) δ 10.49 (br, 1H), 7.61 (d, J =
8.5 Hz, 2H), 7.55 (s, 1H), 7.49 (d, J = 8.2 Hz, 1H), 7.45−7.43 (m,
1H), 7.40 (d, J = 8.5 Hz, 2H), 7.17−7.15 (m, 2H), 1.52 (s, 9H), 1.3 (s,
9H); 13C {1H} NMR (100 MHz, CDCl3) δ 155.8, 137.9, 134.1, 131. 6,
131.0, 130.8, 126.5, 125.6, 125.0, 124. 5, 123.5, 71.0, 35.0, 31.0, 28.1;
IR (KBr, cm−1) 3421, 3075, 2978, 1571, 1494, 1334, 1167, 1112, 1084,
916, 846, 799, 776, 632, 572, 552, 529; HRMS (ESI) calcd for
C21H29N2O3S+ [M + H]+ m/z 389.1893, found 389.1895.
(Z)-N-(2-(4-Methoxyphenylsulfonamido)benzylidene)-2-methyl-
propan-2-amine oxide (3ac): 71.2 mg, 99%; white solid; mp 155 °C;
1H NMR (400 MHz, CDCl3) δ 10.50 (s, 1H), 7.63 (d, J = 8.7 Hz,
2H), 7.60 (s, 1H), 7.46−7.40 (m, 2H), 7.16−7.14 (m, 2H), 6.86 (d, J
= 8.7 Hz, 2H), 3.82 (s, 3H), 1.57 (s, 9H); 13C {1H} NMR (100 MHz,
CDCl3) δ 162.4, 137.9, 134.2, 132.6, 131.5, 131.1, 128.8, 124.6, 124.4,
123.4, 113.8, 71.1, 55.5, 28.1; IR (KBr, cm−1) 3423, 3090, 2980, 1596,
1493, 1327, 1259, 1159, 1095, 1027, 924, 890, 835, 805, 774, 667, 568,
550; HRMS (ESI) calcd for C18H22N2NaO4S+ [M + Na]+ m/z
385.1192, found 385.1196.
EXPERIMENTAL SECTION
■
General Information. All catalytic reactions were carried out
under air atmosphere. Unless otherwise stated, all reagents were
purchased without further purification. Analytical thin-layer chroma-
tography (TLC) was performed on precoated silica gel GF254 plates.
Visualization on TLC was achieved by the use of UV light (254 nm).
1H NMR spectra were recorded on a 400 MHz spectrometer with
deuteraterated chloroform as solutions. The chemical shifts δ are
reported in ppm relative to tetramethylsilane. The multiplicity of
signals is designated by the following abbreviations: s (singlet), d
(doublet), t (triplet), q (quartet), m (multiplet). Coupling constants, J,
are reported in hertz (Hz). 13C {1H} NMR spectra were recorded at
100 MHz spectrometer with deuteraterated chloroform as solutions.
The chemical shifts δ are reported relative to residual CHCl3 (δc =
77.00 ppm). High-resolution mass spectra (HRMS) were obtained on
a Q-ToF spectrometer with micromass MS software using electrospray
ionization (ESI). X-ray analysis was obtained with an X-ray single-
crystal diffractometer. Melting points were measured on a microscopic
apparatus and are uncorrected.
General Procedure for the Preparation of Azide Substrates
(2).19 To a solution of sodium azide (0.95 g, 15 mmol) in water (5
mL) was added dropwise a solution of sulfonyl chloride (10 mmol) in
acetone (5 mL) at 0 °C. The reaction mixture was warmed to room
temperature and stirred overnight. Acetone was removed under
reduced pressure, and the reaction mixture was extracted with EtOAc
(10 mL × 3). The combined organic layer was dried over Na2SO4, and
solvents were removed in vacuo.
(Z)-2-Methyl-N-(2-(phenylsulfonamido)benzylidene)propan-2-
1
amine oxide (3ad): 65.8 mg, 99%; white solid; mp 144−145 °C; H
NMR (400 MHz, CDCl3) δ 10.61 (br, 1H), 7.67 (d, J = 7.7 Hz, 2H),
7.54 (s, 1H), 7.50−7.47 (m, 2H), 7.45−7.38 (m, 3H), 7.19−7.13 (m,
2H), 1.54 (s, 9H); 13C {1H} NMR (100 MHz, CDCl3) δ 140.7, 137.7,
134.1, 132.1, 131.6, 131.1, 128.7, 126.7, 125.0, 124.6, 123.6, 71.1, 28.1;
IR (KBr, cm−1) 3429, 3129, 2980, 1570, 1497, 1400, 1321, 1239, 1165,
1095, 956, 904, 837, 759, 692, 575, 543; HRMS (ESI) calcd for
C17H21N2O3S+ [M + H]+ m/z 333.1267, found 333.1271.
(Z)-N-(2-(4-Fluorophenylsulfonamido)benzylidene)-2-methylpro-
pan-2-amine oxide (3ae): 67.3 mg, 96%; white solid; mp 150−151
°C; 1H NMR (400 MHz, CDCl3) δ 10.78 (br, 1H), 7.73 (dd, J1 = 8.7
Hz, J2 = 5.2 Hz, 2H), 7.62 (s, 1H), 7.44−7.42 (m, 2H), 7.18−7.16 (m,
2H), 7.11−7.06 (m, 2H), 1.57 (s, 9H); 13C {1H} NMR (100 MHz,
CDCl3) δ 164.7 (d, JC−F = 249.1 Hz), 137.6, 136.9 (d, JC−F = 3.8 Hz),
134.2, 131.5 (d, JC−F = 44.4 Hz), 129.4, 129.3, 124.6, 124.4, 123.4,
115.8 (d, JC−F = 22.4 Hz), 71.2, 28.2; IR (KBr, cm−1) 3423, 3066,
2985, 2922, 1590, 1492, 1353, 1326, 1233, 1168, 1093, 842, 778, 665,
565, 544; HRMS (ESI) calcd for C17H19FN2NaO3S+ [M + Na]+ m/z
373.0993, found 373.0996.
(Z)-N-(2-(4-Chlorophenylsulfonamido)benzylidene)-2-methylpro-
pan-2-amine oxide (3af): 69.7 mg, 95%; white solid; mp 145−146
°C; 1H NMR (400 MHz, CDCl3) δ 10.90 (br, 1H), 7.62 (s, 1H), 7.61
General Procedure for the Preparation of Aryl Nitrones
Substrates (1).20 Under N2 atmosphere, a round-bottom flask (100
D
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(d, J = 7.7 Hz, 2H), 7.46−7.40 (m, 2H), 7.37 (d, J = 8.6 Hz, 2H),
7.20−7.15 (m, 2H), 1.55 (s, 9H); 13C {1H} NMR (100 MHz, CDCl3)
δ 139.3, 138.6, 137.4, 134.3, 131.7, 131.4, 128.9, 128.1, 124.7, 124.5,
123.4, 71.2, 28.1. IR (KBr, cm−1) 3430, 3092, 1570, 1398, 1332, 1278,
1164, 1129, 1089, 925, 890, 832, 800, 774, 612, 550, 480; HRMS
(ESI) calcd for C17H20ClN2O3S+ [M + H]+ m/z 367.0878, found
367.0881.
122.8, 71.6, 28.5; IR (KBr, cm−1) 2977, 1567, 1493, 1452, 1403, 1347,
1159, 1128, 1074, 959, 907, 861, 821, 751, 658, 616, 541, 504, 480;
HRMS (ESI) calcd for C21H23N2O3S+ [M + H]+ m/z 383.1424, found
383.1429.
(Z)-2-Methyl-N-(2-(3-nitrophenylsulfonamido)benzylidene)-
propan-2-amine oxide (3an): 69.4 mg, 92%; yellow solid; mp 181−
183 °C; 1H NMR (400 MHz, CDCl3) δ 11.38 (s, 1H), 8.55−8.53 (m,
1H), 8.36−8.33 (m, 1H), 8.06 (d, J = 7.8 Hz, 2H), 7.67 (s, 1H), 7.63
(t, J = 8.0 Hz, 1H), 7.49−7.45 (m, 2H), 7.19−7.18 (m, 2H), 1.59 (s,
9H); 13C {1H} NMR (100 MHz, CDCl3) δ 148.0, 143.1, 137.2, 134.4,
132.4, 132.0, 131.6, 130.1, 126.6, 124.9, 124.1, 123.2, 121.8, 71.5, 28.1;
IR (KBr, cm−1) 3090, 2981, 1603, 1535, 1492, 1403, 1358, 1275, 1174,
1127, 1069, 944, 878, 849, 810, 782, 753, 670, 584, 408; HRMS (ESI)
calcd for C17H19N3Na O5S+ [M + Na]+ m/z 400.0938, found
400.0946.
(Z)-N-(2-(4-Bromophenylsulfonamido)benzylidene)-2-methylpro-
pan-2-amine oxide (3ag): 81.4 mg, 99%; white solid; mp 140 °C; 1H
NMR (400 MHz, CDCl3) δ 10.86 (s, 1H), 7.62 (s, 1H), 7.58 (d, J =
8.6 Hz, 2H), 7.54 (d, J = 8.7 Hz, 2H), 7.44−7.43 (m, 2H), 7.18−7.17
(m, 2H), 1.57 (s, 9H); 13C {1H} NMR (100 MHz, CDCl3) δ 138.8,
137.4, 134.3, 131.9, 131.7, 131.4, 128.2, 127.0, 124.7, 124.5, 123.4,
71.2, 28.1; IR (KBr, cm−1) 3426, 3144, 2985, 1571, 1400, 1359, 1274,
1164, 1129, 1069, 925, 804, 780, 736, 599, 543; HRMS (ESI) calcd for
C17H19BrN2NaO3S+ [M + Na]+ m/z 433.0192, found 433.0197.
(Z)-2-Methyl-N-(2-(4-(trifluoromethyl)phenylsulfonamido)-
benzylidene)propan-2-amine oxide (3ah): 78.5 mg, 98%; white
(Z)-N-(2-(2,4-Dimethylphenylsulfonamido)benzylidene)-2-meth-
ylpropan-2-amine oxide (3ao): 68.5 mg, 95%; white solid; mp 116−
1
118 °C; H NMR (400 MHz, CDCl3) δδ 10.78 (s, 1H), 7.86 (d, J =
1
solid; mp 142−143 °C; H NMR (400 MHz, CDCl3) δ 11.07 (br,
8.8 Hz, 1H), 7.82 (s, 1H), 7.32−7.28 (m, 1H), 7.19 (m, 2H), 7.10−
7.06 (m, 3H), 2.59 (s, 3H), 2.34 (s, 3H), 1.62 (s, 9H). 13C {1H} NMR
(100 MHz, CDCl3) δ 142.9, 138.3, 137.2, 136.5, 134.8, 133.1, 131.4,
131.3, 129.1, 126.6, 123.6, 122.6, 122.4, 71.1, 28.2, 21.1, 20.0; IR (KBr,
cm−1) 2982, 2922, 1599, 1571, 1492, 1445, 1401, 1324, 1234, 1172,
1143, 1060, 939, 906, 828, 56, 655, 624, 573, 544, 524, 412; HRMS
(ESI) calcd for C19H24N2NaO3S+ [M + Na]+ m/z 383.1400, found
383.1402.
1H), 7.84 (d, J = 8.2 Hz, 2H), 7.68 (d, J = 8.3 Hz, 2H), 7.60 (s, 1H),
7.45−7.44 (m, 2H), 7.20−7.18 (m, 2H), 1.55 (s, 9H); 13C {1H} NMR
(100 MHz, CDCl3) δ 144.5, 137.4, 134.3, 133.9 (q, JC−F = 32.8 Hz),
131.8, 131.4, 127.2, 125.8 (q, JC−F = 271.5 Hz), 125.8 (q, JC−F = 3.7
Hz), 124.8, 124.5, 123.4, 71.3, 28.1; IR (KBr, cm−1) 3429, 3129, 1609,
1402, 1325, 1167, 1128, 603, 542; HRMS (ESI) calcd for
C18H20F3N2O3S+ [M + H]+ m/z 401.1141, found 401.1149.
(Z)-N-(2-(4-Acetylphenylsulfonamido)benzylidene)-2-methylpro-
(Z)-N-(2-(3-Chloro-2-methylphenylsulfonamido)benzylidene)-2-
pan-2-amine oxide (3ai). 72.7 mg, 97%; white solid; mp 137−138
methylpropan-2-amine oxide (3ap): 62.5 mg, 82%; white solid; mp
1
1
°C; H NMR (400 MHz, CDCl3) δ 11.04 (br, 1H), 7.97 (d, J = 8.3
175 °C; H NMR (400 MHz, CDCl3) δ 11.24 (br, 1H), 7.96 (d, J =
Hz, 2H), 7.83−7.80 (m, 2H), 7.61 (s, 1H), 7.44−7.43 (m, 2H), 7.17−
7.16 (m, 2H), 2.62 (s, 9H), 1.59 (s, 9H); 13C {1H} NMR (100 MHz,
CDCl3) δ 196.7, 144.8, 139.6, 137.5, 134.3, 131.8, 131.4, 128.5, 127.0,
124.6, 124.2, 123.3, 71.3, 28.1, 26.7; IR (KBr, cm−1) 3426, 2978, 2926,
1690, 1357, 1262, 1163, 807, 637, 589, 542; HRMS (ESI) calcd for
C19H23N2O4S+ [M + H]+ m/z 375.1373, found 375.1376.
7.9 Hz, 1H), 7.87 (s, 1H), 7.54 (d, J = 8.0 Hz, 1H), 7.35−7.30 (m,
1H), 7.24−7.21 (m, 2H), 7.17 (d, J = 8.2 Hz, 1H), 7.11 (t, J = 7.6 Hz,
1H), 2.71 (s, 3H), 1.63 (s, 9H); 13C {1H} NMR (100 MHz, CDCl3) δ
141.6, 138.1, 136.8, 135.4, 135.0, 133.3, 131.6, 131.5, 127.5, 126.5,
123.8, 122.5, 122.3, 71.2, 28.2, 16.7; IR (KBr, cm−1) 2979, 2931, 1570,
1495, 1434, 1329, 1151, 1089, 756, 702, 614, 561; HRMS (ESI) calcd
for C18H21ClN2NaO3S+ [M + Na]+ m/z 403.0854, found 403.0867.
(Z)-2-Methyl-N-(2-(thiophene-2-sulfonamido)benzylidene)-
propan-2-amine oxide (3ar): 63.6 mg, 94%; white solid; mp 155−157
(Z)-2-Methyl-N-(2-(4-nitrophenylsulfonamido)benzylidene)-
propan-2-amine oxide (3aj): 47.6 mg, 63%; yellow solid; mp 191−
1
192 °C; H NMR (400 MHz, CDCl3) δ 11.43 (br, 1H), 8.27 (d, J =
1
8.7 Hz, 2H), 7.94 (d, J = 8.7 Hz, 2H), 7.68 (s, 1H), 7.46−7.41 (m,
2H), 7.21−7.19 (m, 2H), 1.59 (s, 9H); 13C {1H} NMR (100 MHz,
CDCl3) δ 149.7, 146.8, 137.3, 134.6, 132.0, 131.6, 128.0, 124.8, 124.0,
123.8, 123.0, 71.4, 28.2; IR (KBr, cm−1) 3422, 2981, 2921, 1530, 1351,
1164, 850, 806, 780, 735, 681, 617, 599, 542, 465; HRMS (ESI) calcd
for C17H19N3NaO5S+ [M + Na]+ m/z 400.0938, found 400.0952.
(Z)-2-Methyl-N-(2-(phenylmethylsulfonamido)benzylidene)-
propan-2-amine oxide (3ak): 65.1 mg, 94%; white solid; mp 143−
144 °C; 1H NMR (400 MHz, CDCl3) δ 10.53 (br, 1H), 7.76 (s, 1H),
7.40−7.36 (m, 1H), 7.33−7.26 (m, 6H), 7.22 (d, J = 7.6 Hz, 1H),
7.16−7.12 (m, 1H), 4.33 (s, 2H), 1.52 (s, 9H); 13C {1H} NMR (100
MHz, CDCl3) δ 138.4, 134.7, 131.7, 131.4, 130.8, 130.5, 129.3, 128.5,
128.4, 123.9, 122.5, 71.1, 58.9, 28.0; IR (KBr, cm−1) 3428, 3130, 1602,
1491, 1452, 1401, 1328, 1160, 1129, 1075, 515; HRMS (ESI) calcd for
C18H23N2O3S+ [M + H]+ m/z 347.1424, found 347.1422.
°C; H NMR (400 MHz, CDCl3) δ 11.21 (s, 1H), 7.96 (dd, J1 = 8.5
Hz, J2 = 1.0 Hz, 1H), 7.86 (s, 1H), 7.54 (dd, J1 = 8.0 Hz, J2 = 0.9 Hz,
1H), 7.35−7.31 (m, 1H), 7.23 (t, J = 8.1 Hz, 2H), 7.16 (d, J = 8.0 Hz,
1H), 7.11 (m, 1H), 2.71 (s, 3H), 1.63 (s, 9H); 13C {1H} NMR (100
MHz, CDCl3) δ 142.0, 137.8, 134.7, 132.2, 131.9, 131.7, 131.7, 127.4,
126.2, 125.7, 124.6, 71.7, 28.6; IR (KBr, cm−1) 3102, 1598, 1495,
1452, 1401, 1333, 1284, 1227, 1075, 1017, 844, 759, 731, 666, 630,
+
585, 540; HRMS (ESI) calcd for C15H19N2O3S2 [M + H]+ m/z
339.0832, found 339.0835.
(Z)-2-Methyl-N-(4-methyl-2-(4-methylphenylsulfonamido)-
benzylidene)propan-2-amine oxide (3ba): 65.6 mg, 91%; white
solid; mp 161−162 °C; 1H NMR (400 MHz, CDCl3) δ 10.73 (s, 1H),
7.57 (d, J = 8.1 Hz, 2H), 7.49 (s, 1H), 7.30 (s, 1H), 7.18 (d, J = 8.0
Hz, 2H), 7.02 (d, J = 8.0 Hz, 1H), 6.96 (d, J = 7.9 Hz, 2H), 2.38 (s,
3H), 2.34 (s, 3H), 1.53 (s, 9H); 13C {1H} NMR (100 MHz, CDCl3) δ
142.7, 142.4, 138.0, 137.8, 134.1, 131.0, 129.1, 126.7, 125.5, 125.4,
120.8, 70.7, 28.1, 21.4, 21.3; IR (KBr, cm−1) 3423, 2988, 2923, 1613,
1323, 1161, 1091, 843, 814, 662, 561, 544; HRMS (ESI) calcd for
C19H24N2NaO3S+ [M + Na]+ m/z 383.1400, found 383.1403.
(Z)-N-(4-Methoxy-2-(4-methylphenylsulfonamido)benzylidene)-
2-methylpropan-2-amine oxide (3ca): 61.0 mg, 81%; white solid; mp
149 °C; 1H NMR (400 MHz, CDCl3) δ 11.46 (s, 1H), 7.62 (d, J = 7.9
Hz, 2H), 7.48 (s, 1H), 7.19 (d, J = 7.9 Hz, 2H), 7.03 (d, J = 8.7 Hz,
1H), 7.00−6.98 (m, 1H), 6.68−6.65 (m, 1H), 3.77 (s, 3H), 2.37 (s,
3H), 1.54 (s, 9H); 13C {1H} NMR (100 MHz, CDCl3) δ 162.5, 142.9,
140.0, 138.0, 134.4, 132. 8, 129.3, 126.8, 115.4, 111.5, 108.2, 70.5, 55.5,
28.2, 21.4; IR (KBr, cm−1) 3419, 3092, 2965, 2923, 1611, 1568, 1508,
1325, 1301, 1159, 1144, 1089, 868, 808, 739, 714, 663, 557, 547;
HRMS (ESI) calcd for C19H25N2O4S+ [M + H]+ m/z 377.1530, found
377.1531.
(Z)-N-(2-(Ethylsulfonamido)benzylidene)-2-methylpropan-2-
1
amine oxide (3al): 53.5 mg, 94%; white solid; mp 83−86 °C; H
NMR (400 MHz, CDCl3) δ 10.53 (br, 1H), 7.92 (s, 1H), 7.55 (d, J =
8.2 Hz, 2H), 7.48−7.43 (m, 1H), 7.29−7.27 (m, 1H), 7.19−7.15 (m,
1H), 3.12 (q, J = 7.4 Hz, 2H), 1.64 (s, 9H), 1.38 (d, J = 7.4 Hz, 3H);
13C {1H} NMR (100 MHz, CDCl3) δ 138.9, 135.2, 132.2, 132.2,
124.4, 123.2, 120.7, 71.2, 47.7, 28.7, 8.8; IR (KBr, cm−1) 3099, 2984,
1635, 1599, 1568, 1491, 1405, 1326, 1268, 1189, 1075, 919, 886, 843,
804, 777, 729, 704, 527, 476, 404; HRMS (ESI) calcd for
C13H20N2NaO3S+ [M + Na]+ m/z 307.1087, found 307.1090.
(Z)-2-Methyl-N-(2-(naphthalene-2-sulfonamido)benzylidene)-
propan-2-amine oxide (3am): 75.0 mg, 98%; white solid; mp 121−
1
124 °C; H NMR (400 MHz, CDCl3) δ 10.54 (br, 0.4H), 8.25 (s,
1H), 7.86−7.80 (m, 3H), 7.62−7.55 (m, 3H), 7.52 (d, J = 8.4 Hz,
1H), 7.44−7.38 (m, 2H), 7.17−7.11 (m, 2H), 1.45 (s, 9H); 13C {1H}
NMR (100 MHz, CDCl3) δ 138.2, 135.0, 134.7, 132.4, 132.1, 131.7,
129.5, 129.3, 129.0, 128.2, 128.1, 127.9, 125.6, 125.2, 124.3, 124.0,
(Z)-2-Methyl-N-((3-(4-methylphenylsulfonamido)-[1,1′-biphenyl]-
4-yl)methylene)propan-2-amine oxide (3da): 71.0 mg, 84%; white
E
DOI: 10.1021/acs.joc.5b01377
J. Org. Chem. XXXX, XXX, XXX−XXX

The Journal of Organic Chemistry
Featured Article
1
solid; mp 147−149 °C; H NMR (400 MHz, CDCl3) δ 10.74 (br,
1306, 1272, 1162, 1099, 1074, 966, 857, 810, 762, 692, 544, 521;
HRMS (ESI) calcd for C19H23N2O5S+ [M + H]+ m/z 391.1322, found
391.1324.
1H), 7.73 (s, 1H), 7.62 (d, J = 7.8 Hz, 2H), 7.59−7.54 (m, 3H), 7.46−
7.38 (m, 4H), 7.23−7.19 (m, 3H), 2.38 (s, 3H), 1.56 (s, 9H); 13C
{1H} NMR (100 MHz, CDCl3) δ 144.3, 143.0, 139.3, 138.3, 138.0,
134.0, 131.7, 129.3, 128.9, 128.2, 127.1, 126.9, 123.3, 123.1, 122.3,
71.1, 28.2, 21.4; IR (KBr, cm−1) 3428, 3128, 1610, 1401, 1329, 1157,
764, 658, 569, 546; HRMS (ESI) calcd for C24H27N2O3S+ [M + H]+
m/z 423.1737, found 423.1739.
(Z)-N-(4-Fluoro-2-(4-methylphenylsulfonamido)benzylidene)-2-
methylpropan-2-amine oxide (3ea): 32.8 mg, 45%; white solid; mp
165 °C; 1H NMR (400 MHz, CDCl3) δ 11.16 (s, 1H), 7.67 (d, J = 8.2
Hz, 2H), 7.61 (s, 1H), 7.23 (d, J = 8.2 Hz, 2H), 7.17 (dd, JH−F = 10.5
Hz, J2 = 2.5 Hz, 1H), 7.13 (dd, J = 8.8 Hz, JH−F = 6.0 Hz, 1H), 6.85−
6.80 (m, 1H), 2.39 (s, 3H), 1.58 (s, 9H); 13C {1H} NMR (100 MHz,
CDCl3) δ 164.7 (d, JC−F = 250.8 Hz), 143.3, 140.4 (d, JC−F = 11.6 Hz),
(Z)-N-(5-Fluoro-2-(4-methylphenylsulfonamido)benzylidene)-2-
methylpropan-2-amine oxide (3ka): 62.0 mg, 85%; white solid; mp
1
121−123 °C; H NMR (400 MHz, CDCl3) δ 9.11 (br, 1H), 7.85 (s,
1H), 7.68 (d, J = 8.2 Hz, 2H), 7.31 (d, J = 7.8 Hz, 1H), 7.26−7.22 (m,
3H), 7.16 (m, 1H), 2.42 (s, 3H), 1.59 (s, 9H); 13C {1H} NMR (100
MHz, CDCl3) δ 158.8 (d, JC−F = 243.3 Hz), 143.2, 137.9, 132.3, 129.2,
127.4, 127.3, 125.7 (d, JC−F = 4.2 Hz), 118.1 (d, JC−F = 20.9 Hz), 71.7,
28.2, 21.5; HRMS (ESI) calcd for C19H23N2O5S+ [M + H]+ m/z
365.1330, found 365.1333.
General Procedure for the Transformation of Sufamidated
Product. Under air atmosphere, a reaction tube (25 mL) equipped
with a magnetic stirrer bar was charged with 3aa (87 mg, 0.25 mmol),
o-(trimethylsilyl)phenyl triflate 4 (91 μL, 0.4 mmol), and CsF (152
mg, 1.0 mmol), followed by 2 mL of dry THF. The vial was sealed and
placed in an oil bath at 65 °C for about 30 h. The resulting mixture
was cooled and concentrated under vacuum to yield the crude product,
which was purified by chromatography on silica gel (elute: EtOAc/
petroleum ether/NEt3) to give the desired product 5: 52.4 mg, 62%;
white solid; 1H NMR (400 MHz, CDCl3) δ 10.68 (br, 1H), 7.67 (d, J
= 8.2 Hz, 2H), 7.20 (m, 4H), 7.10 (t, J = 6.4 Hz, 1H), 7.01 (t, J = 7.5
Hz, 1H), 6.89 (d, J = 8.1 Hz, 2H), 6.80 (d, J = 8.0 Hz, 1H), 6.68 (t, J =
7.5 Hz, 1H), 6.50 (d, J = 7.6 Hz, 1H), 5.65 (s, 1H), 2.25 (s, 3H), 2.17
(s, 1H), 1.21 (s, 9H); 13C {1H} NMR (100 MHz, CDCl3) δ 1155.2,
142.6, 137.1, 136.6, 129.2, 129.0, 128.8, 128.5, 128.2, 127.6, 126.9,
123.4, 121.2, 120.0, 106.9, 68.8, 60.9, 25.2, 21.4.
137.7, 134.0, 133.1 (d, JC−F = 10.3 Hz), 129.5, 126.8, 118.7 (d, JC−F
=
2.9 Hz), 111.4 (d, JC−F = 22.5 Hz), 110.4 (d, JC−F = 25.1 Hz), 71.2,
28.2, 21.5; IR (KBr, cm−1) 3406, 3094, 2975, 2924, 1605, 1579, 1504,
1407, 1327, 1160, 1118, 1090, 995, 869, 814, 742, 712, 664, 560, 544;
HRMS (ESI) calcd for C18H22FN2O3S+ [M + H]+ m/z 365.1330,
found 365.1332.
(Z)-N-(4-Chloro-2-(4-methylphenylsulfonamido)benzylidene)-2-
methylpropan-2-amine oxide (3fa): 62.5 mg, 82%; white solid; mp
180 °C; H NMR (400 MHz, CDCl3) δ 11.19 (br, 1H), 7.65 (d, J =
8.1 Hz, 2H), 7.58 (s, 1H), 7.48−7.47 (m, 1H), 7.23 (d, J = 8.0 Hz,
2H), 7.12−7.06 (m, 2H), 2.40 (s, 3H), 1.57 (s, 9H); 13C {1H} NMR
(100 MHz, CDCl3) δ 143.3, 139.1, 137.7, 137.6, 133.6, 132.2, 129.5,
126.8, 124.5, 124.0, 121.5, 71.4, 28.2, 21.5; IR (KBr, cm−1) 3423, 2978,
2924, 1592, 1328, 1162, 949, 813, 657, 563, 544; HRMS (ESI)
calculated for C18H22ClN2O3S+ [M + H]+ m/z 381.1034,
found381.1036.
(Z)-2-Methyl-N-(2-(4-methylphenylsulfonamido)-4-
(trifluoromethyl)benzylidene)propan-2-amine oxide (3ga): 78.7 mg,
95%; white solid; mp 145−148 °C; H NMR (400 MHz, CDCl3) δ
10.46 (br, 1H), 7.73 (s, 1H), 7.66 (s, 1H), 7.56 (d, J = 8.2 Hz, 2H),
7.34 (d, J = 8.3 Hz, 2H), 7.30 (d, J = 8.2 Hz, 2H), 7.19 (d, J = 8.0 Hz,
2H), 2.36 (s, 3H), 1.54 (s, 9H); 13C {1H} NMR (100 MHz, CDCl3) δ
142.5, 137.4, 136.5, 132.2, 132.1 (q, JC−F = 32.9 Hz), 130.7, 128.5,
125.9, 122.3 (q, JC−F = 271.1 Hz), 120.2 (q, JC−F = 3.7 Hz), 119.8 (q,
JC−F = 3.5 Hz), 71.0, 27.2, 20.5; IR (KBr, cm−1) 3126, 1402, 1331,
1263, 1162, 1132, 1090, 959, 892, 819, 667, 564; HRMS (ESI) calcd
for C19H22F3N2O3S+ [M + H]+ m/z 415.1298, found 415.1299.
(Z)-2-Methyl-N-(5-methyl-2-(4-methylphenylsulfonamido)-
benzylidene)propan-2-amine oxide (3ha): 69.2 mg, 96%; white
solid; mp 190−191 °C; 1H NMR (400 MHz, CDCl3) δ 10.27 (s, 1H),
7.54 (d, J = 8.2 Hz, 2H), 7.49 (s, 1H), 7.35 (d, J = 8.3 Hz, 1H), 7.23−
7.21 (m, 1H), 7.18 (d, J = 8.0 Hz, 2H), 6.96 (s, 1H), 2.38 (s, 3H), 2.30
(s, 3H), 1.52 (s, 9H); 13C {1H} NMR (100 MHz, CDCl3) δ 142.7,
135.2, 134.5, 133.9, 132.4, 132.1, 131.1, 129.1, 126.8, 125.4, 123.9,
70.9, 28.1, 21.3, 20.5; IR (KBr, cm−1) 3425, 2980, 2925, 1501, 1325,
1160, 1093, 902, 821, 667, 581, 537. HRMS (ESI) calcd for
C19H25N2O3S+ [M + H]+ m/z 361.1580, found 361.1583.
1
ASSOCIATED CONTENT
■
S
* Supporting Information
1H and 13C {1H} NMR spectra of compounds 3 and crystal
structure and data of 3aa. The Supporting Information is
available free of charge on the ACS Publications website at
DOI: 10.1021/acs.joc.5b01377.
1
AUTHOR INFORMATION
■
Corresponding Authors
*E-mail: cuixl@zzu.edu.cn.
*E-mail: wyj@zzu.edu.cn.
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
This work was supported by the National Natural Science
Foundation of China (No 21172200) and Zhengzhou
University.
(Z)-2-Methyl-N-(2-methyl-6-(4-methylphenylsulfonamido)-
REFERENCES
■
benzylidene)propan-2-amine oxide (3ia): 70.7 mg, 98%; white solid;
1
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Tetrahedron 2011, 67, 8544.
mp 125−126 °C; H NMR (400 MHz, CDCl3) δ 10.03 (s, 1H), 7.66
(s, 1H), 7.59 (d, J = 8.2 Hz, 2H), 7.30−7.38 (m, 2H), 7.20 (d, J = 8.2
Hz, 2H), 6.99 (d, J = 7.2 Hz, 2H), 2.38 (s, 3H), 2.25 (s, 3H), 1.56 (s,
9H); 13C {1H} NMR (100 MHz, CDCl3) δ 142.9, 138.4, 138.2, 133.1,
131.1, 129.3, 126.7, 126.7, 122.6, 122.3, 71.3, 28.1, 21.4, 20.0; IR (KBr,
cm−1) 3094, 2974, 1599, 1564, 1470, 1399, 1348, 1162, 1095, 1032,
977, 816, 715, 668, 571, 551; HRMS (ESI) calcd for C19H25N2O3S+
[M + H]+ m/z 361.1580, found 361.1583.
(Z)-2-Methyl-N-((6-(4-methylphenylsulfonamido)benzo[d][1,3]-
dioxol-5-yl)methylene)propan-2-amine oxide (3ja): 50.8 mg, 65%;
1
yellow solid; mp 166 °C; H NMR (400 MHz, CDCl3) δ 9.81 (br,
1H), 7.63 (d, J = 8.2 Hz, 2H), 7.55 (s, 1H), 7.22 (d, J = 8.1 Hz, 2H),
6.90 (d, J = 8.2 Hz, 1H), 6.76 (d, J = 8.2 Hz, 1H), 5.95 (s, 2H), 2.41
(s, 3H), 1.50 (s, 9H); 13C {1H} NMR (100 MHz, CDCl3) δ 143.3,
139.1, 137.7, 137.6, 133.6, 132.2, 129.5, 126.8, 124.5, 124.0, 121.5,
71.4, 28.2, 21.5; IR (KBr, cm−1) 3422, 2975, 2923, 1624, 1470, 1356,
F
DOI: 10.1021/acs.joc.5b01377
J. Org. Chem. XXXX, XXX, XXX−XXX

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DOI: 10.1021/acs.joc.5b01377
J. Org. Chem. XXXX, XXX, XXX−XXX