Hypervalent iodine-mediated aminobromination of olefins in water

Article abstract of DOI:10.1016/j.tet.2009.08.069

The PhI(OAc)₂-catalyzed aminobromination of electron-deficient olefins has been achieved in pure water with TsNH₂ and NBS as nitrogen and bromine sources, respectively. With a catalytic amount of PhI(OAc)₂, various olefins

Full text of DOI:10.1016/j.tet.2009.08.069

Tetrahedron 65 (2009) 8802–8807
Contents lists available at ScienceDirect
Tetrahedron
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Hypervalent iodine-mediated aminobromination of olefins in water
*
Xue-Liang Wu, Guan-Wu Wang
Hefei National Laboratory for Physical Sciences at Microscale, Joint Laboratory of Green Synthetic Chemistry, and Department of Chemistry,
University of Science and Technology of China, Hefei, Anhui 230026, PR China
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 28 July 2009
Received in revised form 22 August 2009
Accepted 28 August 2009
Available online 1 September 2009
The PhI(OAc)2-catalyzed aminobromination of electron-deficient olefins has been achieved in pure water
with TsNH2 and NBS as nitrogen and bromine sources, respectively. With a catalytic amount of PhI(OAc)2,
various olefins including a,b-unsaturated ketones, cinnamates, and cinnamides could be aminobrominated
efficiently, giving the vicinal bromoamines in good yields and high regio- and diastereoselectivities.
Utilizing water as solvent was crucial to realize this aminobromination reaction catalytically. The
regioselectivity for the aminobromination of styrenes under the present aqueous conditions was also
dramatically improved.
Keywords:
Aminobromination
Olefins
Ó 2009 Elsevier Ltd. All rights reserved.
(Diacetoxyiodo)benzene
Aqueous reaction
1. Introduction
Furthermore, the combination of sulfonamides and NBS has been
found to be very efficient in the aminobromination of various olefins
Vicinal haloamines have elicited attention from the chemical
sciences owing to their utilityas key intermediates in the synthesis of
biologically and pharmaceutically relevant molecules.1 These im-
portant functionalities could be installed by the aminohalogenation
of carbon–carbon double bond. Many reagent systems including
N,N-dihalo sulfonamides,2 N,N-dihalo carbamates,3 N-halo carba-
mates,4 N-bromoacetamide,5 N,N-dibromo phosphoramidate,6 S,S-
dimethyl-N-(p-toluenesulfonyl)-sulfilimine/NBS,7 and cyanamide/
NBS8 are employed in this subject and these methodologies repre-
sent useful routes to synthesize vicinal haloamine moieties during
the past few decades. However, considerable drawbacks such as
severe reaction conditions, tedious manipulation, and low reaction
efficiency plagued these reactions. As a result, the convenient and
selective aminohalogenation of olefins is highly desirable.
by Sudalai,14 Doyle,15 Fu,16 Wei,17 and their co-workers with CuI,
MnSO4, V2O5, Mn(III)–salen, Rh complex, FeCl2, or copper powder as
catalysts.
Among the myriad of works devoted to this chemistry, those on
developing new methods that make use of mild reaction condi-
tions, simple manipulation, atom-economy, and environmentally-
friendly catalysts have become very topical. The metal-free
aminochlorination of chalcones18 and -nitrostyrenes10 has been
b
realized by Li and co-workers. The reversed regioselectivity of these
reactions suggested a different pathway. We found that the amino-
halogenation reaction of electron-deficient olefins could be pro-
moted by hypervalent iodine compounds under solvent-free
conditions19 or in organic solvent,20 giving a similar regioselectivity
as metal-catalyzed reactions. Hypervalent iodine compounds such
as PhI(OAc)2 are usually used as clean and efficient oxidants in
various organic transformations.21 Surprisingly, only 50–75 mol %
of PhI(OAc)2 was required in our methods. However, further de-
creasing the loading of PhI(OAc)2 was unsuccessful and the ami-
nohalogenation reaction with catalytic amount of PhI(OAc)2 still
remains challenging. Recently, the first Brønsted acid-promoted
aminochlorination reaction utilizing pure water as the solvent was
realized by our group. Water was revealed to represent as a privi-
leged solvent to this reaction.22 We envisioned that water may hold
promise as an efficient reaction medium for the PhI(OAc)2-pro-
moted aminobromination reaction. In our continuous interest on
the aminohalogenation of olefins, herein we report the first
PhI(OAc)2-catalyzed aminobromination of olefins in pure water
with TsNH2 and NBS as nitrogen and bromine sources, respectively.
Li and co-workers developed the first catalytic aminochlorination
reaction of electron-deficient olefins with Cu(I) salts,9a,b,d–i,10 ZnCl2,9a
and Pd complex9c,j as efficient catalysts. By employment of several
different nitrogen/chlorine sources, such as 4-TsNCl2,9a,c,e–g,i,j,10
2-NsNNaCl,9d or the combination of 2-NsNCl2 and 2-NsNHNa,9b,h
various olefins including
a,b
-unsaturated esters,9a–e ketones,9g,h
amides,9f,j nitriles,9i and -nitrostyrenes10 could be aminochlorinated
b
to produce vicinal chloroamine derivatives with good yields and
excellent regio- and diastereoselectivities.11,12 Later, the double bonds
of methylenecyclopropanes were also aminobrominated efficiently.13
* Corresponding author. Tel./fax: þ86 551 360 7864.
E-mail address: gwang@ustc.edu.cn (G.-W. Wang).
0040-4020/$ – see front matter Ó 2009 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2009.08.069

X.-L. Wu, G.-W. Wang / Tetrahedron 65 (2009) 8802–8807
8803
2. Results and discussion
in Table 2. In the absence of PhI(OAc)2, bromohydrine was
obtained as a major product in good yield (entries 1–3). Once
5 mol % of PhI(OAc)2 was added, the bromohydroxylation was
suppressed, and bromoamine 2a was isolated in 41% yield together
with 34% yield of bromohydrine 3 (entry 4). This result demon-
strated the remarkable catalytic efficiency of PhI(OAc)2. Increasing
the loading of PhI(OAc)2 could further reduce the generation of 3
(entries 5–7). However, this side reaction could not be completely
inhibited, and the bromohydrine was observed as a minor product
throughout this research, but could be easily separated out from
the desired bromoamine by flash chromatography.
In the preliminary study, we chose chalcone 1a as a model sub-
strate to probe the feasibility of this reaction. The results are sum-
marized in Table 1. Much to our delight, when chalcone 1a, TsNH2,
and NBS were mixed with PhI(OAc)2 (75 mol %) in H2O at 20 ꢀC for
60 min, vicinal bromoamine 2a was obtained in moderate yield yet
with high regioselectivity and diastereoselectivity (Table 1, entry 1).
This result suggested that the hypervalent iodine-promoted amino-
bromination reaction could, indeed, be performed in pure water.
Elevating the temperature to 50 ꢀC accelerated the reaction signifi-
cantly; the aminobromination completed in 20 min, giving the final
product in good yield of 80% (entry 2). Intrigued by this nice result,
we next reduced the loading of PhI(OAc)2. To our satisfaction, this
aminobromination reaction could proceed efficiently with only
20 mol % of PhI(OAc)2, and haloamine 2a could still be isolated in 81%
yield within 30 min (entries 3–5). Compared with the reaction in the
solid state and organic solvent, this remarkable outcome indicated
that water was an optimal reaction medium and was crucial to
realize the aminobromination reaction catalytically. PhI(OAc)2, in the
true sense, played the role of catalyst in this aminobromination
process. Further reducing the loading of PhI(OAc)2 compromised the
yield obviously; however, with 5 mol % of PhI(OAc)2 the product was
still obtained in 41% yield (entries 6 and 7). Without the promotion of
PhI(OAc)2, no expected product was observed (entry 8). The reaction
yield would decrease to some extent no matter the reaction tem-
perature was elevated or reduced (entries 9–11). Reducing the
amount of TsNH2 was harmful; the yield dropped visibly when
1 equiv of TsNH2 was employed (entries 12 and 13). To further
demonstrate the unique property of water in this reaction, ethanol
was added as a cosolvent. The reaction carried out in H2O/EtOH 1:2
afforded only a trace amount of the bromoamine, and no product
was observed in pure ethanol (entries 14 and 15).
Table 2
The aminobromination and bromohydroxylation of chalcone 1a in watera
Br
O
OH O
PhI(OAc)2
(x mol%)
O
+ TsNH2 + NBS
Ph
Ph
Ph Ph
Ph
H2O
Ph
NHTs
Br
( )-3
1a
( )-2a
Entry
x
T (ꢀC)
t (min)
Yieldb of 2a
Yieldb of 3
1
2
3c
4
5
6
7
0
0
0
5
10
15
20
100
50
50
50
50
50
50
30
30
30
60
60
50
30
0
0
0
41
61
71
81
68
65
71
34
28
14
5
a
All reactions were performed with 0.2 mmol of chalcone 1a, 0.3 mmol of TsNH2,
and 0.3 mmol of NBS in 2 mL of water.
b
Isolated yield.
Reaction was performed without TsNH2.
c
Compelled by the significance of this reaction together with the
importance of the vicinal bromoamine products, we next
embarked on exploring the substrate scope of this PhI(OAc)2-cat-
alyzed aminobromination reaction. Various electron-deficient
olefins were investigated and the results are listed in Table 3. Our
method was successfully amenable to a variety of chalcones with
different substituents on the phenyl rings, giving the final prod-
ucts in good to high yields ranging from 61% to 81%. It is worth
mentioning that the reaction system was very efficient and the
reactions were completed within 30–90 min (entries 1–9). When
the enone with 3,4-Cl2 substituted on the phenyl ring attached
with the double bond and the enone with 4-Cl substituted on both
phenyl rings were employed as substrates, the reactions were
performed at elevated temperature to get higher conversion (en-
tries 4 and 9). 4-Nitro substituted chalcone was less reactive,
affording the bromoamine in reduced yield even by increasing the
catalyst loading and reaction temperature (entry 5). The scope of
this method could be successfully extended to the enone with
methyl attached to the carbonyl group, which furnished the
product in good yield as a single diastereoisomer within 25 min
(entry 10). The cinnamates and cinnamides were also tolerated,
Table 1
a
Aminobromination of chalcone 1a in pure water promoted by PhI(OAc)2
Br
O
PhI(OAc)2
(x mol%)
O
+ TsNH2 + NBS
Ph
Ph
Ph
NHTs
( )-2a
H2O
Ph
1a
Entry
x
T (ꢀC)
t (min)
Yieldb (%)
drc (anti/syn)
1
2
3
4
5
6
7
8
75
75
50
30
20
10
5
20
50
50
50
50
50
50
50
40
70
100
50
50
20
20
60
20
25
25
30
40
60
60
50
30
20
30
40
120
120
61
80
81
80
81
63
41
0
78
75
73
79
70
Trace
0
90:10
89:11
90:10
89:10
88:12
90:10
89:11
d
0
9
20
20
20
20
20
75
75
90:10
89:11
87:13
90:10
89:11
nd
10
11
12d
13e
14f
15g
giving the a-amino derivatives in moderate yields (entries 11–14).
The 4-Cl substituted reactants were less reactive; higher catalyst
loading was necessary to achieve reasonable yields (entries 12 and
14). Compared with the reaction in the solid state and dichloro-
methane, the efficiency of the present system improved obvious-
ly.19b,20 Most of these reactions could be completed within 1 h. The
diastereoselectivity of the present catalytic aqueous system is
generally comparable to that in the solid state19b and in dichloro-
methane.20a Nevertheless, a much better diastereoselectivity in
cases of 1e and 1j was observed by our present protocol, and only
one pure diastereoisomer was obtained (entries 5 and 10).
d
a
Unless otherwise specified, all reactions were performed with 0.2 mmol of
chalcone 1a, 0.3 mmol of TsNH2, and 0.3 mmol of NBS in 2 mL of water.
b
Isolated yield of (ꢁ)-2a.
c
Determined by the analysis of 1H NMR spectra.
d
0.24 mmol of TsNH2 and 0.3 mmol of NBS were employed.
0.2 mmol of TsNH2 and 0.3 mmol of NBS were employed.
Reaction was performed in H2O/EtOH 1:2.
Reaction was performed in EtOH.
e
f
g
The bromohydroxylation of electron-deficient olefins with NBS
in aqueous media is known.23 In our aminobromination system,
the bromohydroxylation was an obvious competition reaction.
Bromohydrine 3 could be observed as a minor product, as shown
The PhI(OAc)2-promoted aminobromination of styrenes was
observed under ball milling conditions. The corresponding pro-
ducts were obtained in moderate yields together with poor

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X.-L. Wu, G.-W. Wang / Tetrahedron 65 (2009) 8802–8807
Table 3
PhI(OAc)2-catalyzed aminobromination of electron-deficient olefins in watera
Br
O
O
PhI(OAc)2 (20 mol%)
H2O
R1
Br
R2
NHTs
( )-2
+ TsNH2 + NBS
R1
R2
1
Entry
1
1
T (ꢀC)
t (min)
2
Yieldb (%)
81
drc (anti/syn)
O
O
50
30
88:12
NHTs
2a
1a
O
Br
O
2
50
40
72
91:9
NHTs
2b
Cl
Cl
1b
Cl
O
Cl
Br
O
3
50
70
70
50
50
50
30
40
90
30
60
50
75
73
61
69
73
71
95:5
96:4
NHTs
2c
1c
O
Br
O
Cl
Cl
Cl
Cl
4
NHTs
2d
OMe
OMe
1d
O
Br
O
5d
>99:1
90:10
93:7
NHTs
2e
O2N
O2N
1e
O
Br
O
6
NHTs
2f
OMe
OMe
1f
O
Br
O
7
NHTs
2g
Cl
OMe
Cl
OMe
1g
O
Br
O
8
96:4
NHTs
2h
Cl
Cl
1h
O
Br
O
9
70
50
40
25
68
71
91:9
NHTs
2i
Cl
Cl
Cl
Cl
1i
O
Br
O
10
>99:1
NHTs
2j
1j
O
Br
O
OMe
OMe
NHTs
2k
11
50
50
60
60
67
52
90:10
1k
O
Br
O
OMe
OMe
NHTs
2l
12d
97:3
Cl
Cl
1l

X.-L. Wu, G.-W. Wang / Tetrahedron 65 (2009) 8802–8807
8805
Table 3 (continued)
Entry
1
T (ꢀC)
t (min)
2
Yieldb (%)
drc (anti/syn)
Br
O
O
NEt2
NHTs
2m
NEt2
O
13
50
90
67
>99:1
>99:1
1m
Br
O
14d
50
80
54
NEt2
NEt2
NHTs
2n
Cl
Cl
1n
a
Unless otherwise specified, all reactions were performed with 0.2 mmol of olefin, 0.3 mmol of TsNH2, 0.3 mmol of NBS, and 0.04 mmol of PhI(OAc)2 in 2 mL of water.
b
c
Isolated yield.
Determined by the analysis of 1H NMR spectra.
30 mol % of PhI(OAc)2 was employed.
d
regioselectivities (from 2.0:1 to 2.6:1).19b We next examined the
feasibility of aminobromination of styrenes in the current system.
The results are listed in Table 4. When styrene 4a was stirred with
TsNH2 and NBS in water at 50 ꢀC for 45 min, the vicinal bromo-
amine was isolated in 47% yield (Table 4, entry 1). On the basis of 1H
NMR spectra, we were pleased to find that only a small amount of
unwanted regioisomer 6a was observed and the regioisomeric ratio
of 5a/6a was 95:5. While performing the reaction at lower tem-
perature decreased the yield, elevating the reaction temperature
was also not helpful to this reaction (entries 2–4). Then we com-
menced to increase the catalyst loading. With 40 mol % of PhI(OAc)2
the bromoamine could be isolated in 60% yield (entries 5–7). Un-
fortunately, further increasing the loading of PhI(OAc)2 did not give
an obvious increase in yield (entry 8). The excellent regioselectivity
nicely demonstrated the efficiency of the current PhI(OAc)2-medi-
ated aminobromination system.
Table 5
PhI(OAc)2-catalyzed aminobromination of styrenes in watera
NHTs
Br
Br
PhI(OAc)2
(40 mol%)
+
+ TsNH2 + NBS
NHTs
H2O, 50 °C
R3
R3
6
R3
4
5
Entry
1
4
t (min)
Yieldb (%)
60
5/6c
45
70
95:5
4a
2
3
57
50
97:3
Cl
4b
Cl
Table 4
50
>99:1
Aminobromination of styrene in watera
Br
NHTs
Br
4c
PhI(OAc)2
(x mol%)
Br
+
+ TsNH2 + NBS
NHTs
H2O
4
5
6
30
90
80
90
51
>99:1
ndd
4a
5a
6a
4d
Entry
x
T (ꢀC)
t (min)
Yieldb (%)
ndd
31
1
2
3
4
5
6
7
8
20
20
20
20
25
30
40
50
50
25
70
100
50
50
45
120
40
47
31
45
41
50
55
60
61
O2N
4e
30
45
45
45
23:77
ndd
50
50
4f
45
a
All reactions were performed with 0.5 mmol of styrene, 0.75 mmol of TsNH2,
and 0.75 mmol of NBS in 2 mL of water.
7
ndd
MeO
b
Combined yields of 5a and 6a; the regioisomeric ratio of 5a/6a was 95:5 on the
4g
basis of 1H NMR spectra.
a
All reactions were performed with 0.5 mmol of styrene, 0.75 mmol of TsNH2,
and 0.75 mmol of NBS with 0.2 mmol of PhI(OAc)2 in 2 mL of water.
With the optimized conditions in hand, various styrenes were
examined in this aminobromination process (Table 5). 4-Cl-styrene
was less reactive, furnishing 57% yield with prolonged reaction
time. The regioselectivity was still excellent, and only a negligible
amount of regioisomer 6b was formed (entry 2). When 2-Cl-sty-
rene and 2-Br-styrene were employed as substrates, the corre-
sponding vicinal bromoamine was obtained as single isomers
(entries 3 and 4). Unfortunately, 4-nitrostyrene and 4-OMe-styrene
gave very complex reaction mixtures and the bromoamine pro-
ducts failed to be isolated (entries 5 and 7). The aminobromination
of 4-Me-styrene indeed occurred, yet the regioselectivity was
reversed (entry 6).
b
Combined yields of 5 and 6.
The regioisomeric ratio was determined by the analysis of 1H NMR spectra.
Not determined because of complex reaction mixture.
c
d
According to the previous work,9,19,20,22 the current PhI(OAc)2-
catalyzed reaction was believed to go through an aziridinium cation
intermediate. The detailedreaction mechanism isshowninScheme 1,
which is similar to our previously proposed one,19b,20a and can ex-
plain the high regio- and diastereoselectivity.
The unusual rate acceleration and better selectivity of organic
reactions inwater compared to the same reactions in organic solvents
have been known for many years.24 In comparison with our earlier

8806
X.-L. Wu, G.-W. Wang / Tetrahedron 65 (2009) 8802–8807
investigated aminobromination under solvent-free conditions19b or
in organic solvent,20a water exhibited as a superior reaction medium
to facilitate the reaction with high efficiency. The amount of
PhI(OAc)2 could be decreased up to 20 mol % from previous 75 mol %,
successfully realizing the aminobromination catalytically.
then evaporated to dryness in vacuo. The residual was separated on
a silica gel column with petroleum ether/ethyl acetate 5:1 as the
eluent to get the desired product 2a (2b–n).
4.3. General procedure for the aminobromination of styrene
in water
NBS
- succinnimide
TsNH2
R2
TsNHBr 7
To a 25 mL round-bottom flask were added styrene 4a (4b–g,
0.5 mmol), TsNH2 (128.3 mg, 0.75 mmol), NBS (133.5 mg,
0.75 mmol), and PhI(OAc)2 (64.5 mg, 0.2 mmol). Then 2 mL of water
was added and the resulting mixture was allowed to stir vigorously at
50 ꢀC for an appropriate time (monitored by TLC). Upon completion,
ethyl acetate (3 mLꢃ2) was added to extract the product. The organic
layer was dried with MgSO4 and then evaporated to dryness in vacuo.
The residual was separated on a silica gel column with petroleum
ether/ethyl acetate 6:1 as the eluent to get the desired product.
Products 2a–n,14,19b 3,23b 5a,14 and 5f7 have previously been syn-
thesized and characterized. The mixture of compound 5b and its
Br
-HOAc
PhI(OAc)2
-PhI
R1
R2
1 or 4
Br
N
R1
TsN
Ts
( ) 2 or 5
H
OAc
8
TsNHBr
7
Br
R2
R1
Br
R1
N
Ts
OAc
( ) 10
R2
N
Ts
9
OAc
regioisomer 6b has been characterized,19b and the IR,1H NMR, and 13
C
Scheme 1. Possible reaction mechanism.
NMR spectra data of pure 5b were given here. Physical and spectro-
scopic data of the newly synthesized compounds are given below.
3. Conclusion
4.3.1. 1-(4-Chlorophenyl)-1-bromo-2-(tosylamino)ethane (5b). White
solid; mp 129–131 ꢀC; 1H NMR (300 MHz, CDCl3)
d
7.71 (d, J¼8.4 Hz,
In summary, we have demonstrated a highly efficient amino-
bromination reaction of electron-deficient olefins catalyzed by
PhI(OAc)2 in pure water with TsNH2 and NBS as the nitrogen and
bromine sources, respectively. Besides guaranteeing a clean and
eco-friendly reaction condition, this aqueous reaction allows the
aminobromination of olefins to proceed smoothly and efficiently,
giving the useful vicinal bromoamines with high yields and selec-
tivities. Catalytic amount of PhI(OAc)2 was used to facilitate this
reaction for the first time. Employing water as solvent was crucial
to realize this aminobromination reaction catalytically. The dia-
stereoselectivity for the current catalytic aqueous reaction of ole-
fins was generally comparable to, even much better in cases of 1e
and 1j than, that in the solid state and in dichloromethane. Fur-
thermore, the regioselectivity for styrenes under the present
aqueous conditions was also dramatically improved.
2H), 7.33–7.21 (m, 6H), 4.90 (t, J¼7.2 Hz, 1H), 4.80 (t, J¼6.0 Hz, 1H),
3.57–3.51 (m, 2H), 2.45 (s, 3H); 13C NMR (75 MHz, CDCl3, all 1C
unless indicated) d 144.0, 137.0, 136.9, 135.0, 130.0 (2C), 129.25 (2C),
129.17 (2C),127.1 (2C), 51.5, 50.1, 21.7; IR (KBr) nmax 3277,1597,1494,
1429, 1323, 1154, 1092, 852, 817, 677, 552, 516 cmꢂ1; HRMS (EI–TOF,
m/z [MþH]þ) calcd for C15H16NO2S35Cl81Br 389.9753, found
389.9749.
4.3.2. 1-(2-Chlorophenyl)-1-bromo-2-(tosylamino)ethane (5c). White
solid; mp 67–69 ꢀC; 1H NMR (300 MHz, CDCl3)
d
7.74 (d, J¼8.4 Hz,
2H), 7.47–7.24 (m, 6H), 5.38 (dd, J¼7.8, 6.3 Hz, 1H), 4.90 (t, J¼6.3 Hz,
1H), 3.65–3.58 (m, 2H), 2.44 (s, 3H); 13C NMR (75 MHz, CDCl3, all 1C
unless indicated) d 143.9, 137.1, 135.7, 133.3, 130.2, 130.1, 130.0 (2C),
129.1, 127.7, 127.2 (2C), 49.0, 48.2, 21.6; IR (KBr) nmax 3292, 3262,
1477, 1437, 1324, 1158, 1088, 849, 812, 739, 673, 553 cmꢂ1; HRMS
(EI–TOF, m/z [MþH]þ) calcd for C15H16NO2S35Cl81Br 389.9753,
found 389.9751.
4. Experimental
4.1. General
4.3.3. 1-(2-Bromophenyl)-1-bromo-2-(tosylamino)ethane (5d). White
solid; mp 80–82 ꢀC; 1H NMR (300 MHz, CDCl3)
d
7.75 (d, J¼8.4 Hz,
All reagents were obtained from commercial sources and used
without further purification. Chromatographic purification of pro-
ducts was accomplished using flash column chromatography on silica
gel. 1H and 13C NMR spectra were recorded with a Bruker AV300
2H), 7.53 (dd, J¼8.1,1.3 Hz,1H), 7.46 (dd, J¼7.8,1.3 Hz,1H), 7.33–7.28
(m, 3H), 7.16 (td, J¼7.8, 1.5 Hz, 1H), 5.37 (dd, J¼8.1, 6.0 Hz, 1H), 4.88
(t, J¼6.0 Hz, 1H), 3.65–3.57 (m, 2H), 2.44 (s, 3H); 13C NMR (75 MHz,
CDCl3, all 1C unless indicated)
d 143.9, 137.3, 137.1, 133.4, 130.5,
spectrometer; chemical shifts are expressed in parts per million (d)
130.0 (2C), 129.2, 128.3, 127.2 (2C), 123.7, 51.0, 49.1, 21.7; IR (KBr)
nmax 3290,1427,1327,1156,1093,1039,1026, 851, 818, 762, 730, 668,
551 cmꢂ1; HRMS (EI–TOF, m/z [MþH]þ) calcd for C15H16NO2S79Br2
431.9268, found 431.9266.
and are referenced to the carbon and residual proton signals of the
NMR solvent (CHCl3:
d
¼7.26 ppm for 1H NMR,
d
¼77.0 ppm for 13C
NMR). Infrared spectra were obtained with a VECTOR-12 infrared
spectrometer; data are presented inwavenumbers (cmꢂ1). HRMS data
were recorded with a BRUKER VPEXII spectrometer with EI mode.
Acknowledgements
4.2. General procedure for the PhI(OAc)2-catalyzed
aminobromination of electron-deficient olefins in water
The authors are grateful for the financial support from National
Natural Science Foundation of China (No. 20772117) and Know-
ledge Innovation Project of the Chinese Academy of Sciences
(KJCX2.YW.H16).
To a 25 mL round-bottom flask were added electron-deficient
olefin 1a (1b–n, 0.2 mmol), TsNH2 (51.3 mg, 0.3 mmol), NBS
(53.4 mg, 0.3 mmol), and PhI(OAc)2 (12.9 mg, 0.04 mmol) (19.4 mg,
0.06 mmol for 1e, 1l, and 1n). Then 2 mL of water was added and
the resulting mixture was allowed to stir vigorously at 50 ꢀC (70 ꢀC
in cases of 1d, 1e, and 1i) for an appropriate time (monitored by
TLC). Upon completion, ethyl acetate (3 mLꢃ2) was added to
extract the product. The organic layer was dried with MgSO4 and
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