Asymmetric Michael addition of α-fluoro-α-phenylsulfonyl ketones to nitroolefins catalyzed by phenylalanine-based bifunctional thioureas

Article abstract of DOI:10.1016/j.jfluchem.2011.05.029

Phenylalanine-based bifunctional thiourea derivatives promoted the asymmetric Michael addition of α-fluoro-α-phenylsulfonyl ketones to nitroolefins, affording enantiomerically enriched fluorine-containing multifunctional molecules containing adjoining chiral fluorine-substituted quaternary and tertiary centers in good yields and enantioselectivities.

Full text of DOI:10.1016/j.jfluchem.2011.05.029

Journal of Fluorine Chemistry 133 (2012) 120–126
Contents lists available at ScienceDirect
Journal of Fluorine Chemistry
journal homepage: www.elsevier.com/locate/fluor
Asymmetric Michael addition of
a-fluoro-a-phenylsulfonyl ketones to
nitroolefins catalyzed by phenylalanine-based bifunctional thioureas§
*
Hai-Feng Cui, Peng Li, Xiao-Wei Wang, Shi-Zheng Zhu, Gang Zhao
Key Laboratory of Synthetic Chemistry of Natural Substances and Key Laboratory of Organofluorine Chemistry, Shanghai Institute of Organic Chemistry, 345 Lingling Road,
Shanghai 200032, China
A R T I C L E I N F O
A B S T R A C T
Article history:
Phenylalanine-based bifunctional thiourea derivatives promoted the asymmetric Michael addition of a-
Received 26 April 2011
Received in revised form 19 May 2011
Accepted 30 May 2011
Available online 18 July 2011
fluoro-a-phenylsulfonyl ketones to nitroolefins, affording enantiomerically enriched fluorine-contain-
ing multifunctional molecules containing adjoining chiral fluorine-substituted quaternary and tertiary
centers in good yields and enantioselectivities.
ß 2011 Elsevier B.V. All rights reserved.
Keywords:
Thiourea
Fluorine-containing
Enantioselectivities
Chiral fluorinated compounds
1. Introduction
with a fluorinated quaternary chiral center in excellent enantios-
electivities [5].
Nowadays, the great importance of fluorine-containing com-
pounds has been well recognized in kinds of fields such as material,
medicinal, pharmaceutical and agrochemical science [1]. The
introduction of the fluorine atom has almost become one of the
routine practices in the studies of these sciences. Therefore, there
has been a great demand for the development of more selective,
safe and mild fluorination methods [2]. With the rapid develop-
ment of organocatalysis over the past decade, the organocatalytic
asymmetric synthesis of fluorinated molecules has received
considerable attentions among organic chemists and impressive
advancement has been achieved [3]. Particularly, the asymmetric
addition reaction of fluorine-substituted monofluorinated nucleo-
philes to various electrophiles, with the concomitant formation of
a new C–C bond and the construction of a chiral fluorinated center,
Besides a-fluoro-b-keto esters, the use of a-nitro, cyano, ester,
or acetyl-substituted fluoro(phenylsulfonyl)methanes as the
nucleophile has been particularly intriguing due to their convert-
ibility into a variety of functionalized monofluoromethylated
compounds, which are crucial synthons for many valuable
compounds in the pharmaceutical arena [4i–j,6]. Prakash et al.
have achieved enantioselective and diastereoselective Michael
additions of these fluorine containing (phenylsulfonyl)methane
derivatives to chalcones using cinchona alkaloids-based bifunc-
tional catalysts [4j,k]. In addition, their organocatalytic asymmet-
ric Michael additions to a, b-unsaturated aldehydes have also been
´
reported by Palomo [4h] and Cordova [4i]. Surprisingly, to the best
of our knowledge, there has been no report on the organocatalyzed
Michael addition of
a-fluoro-a-phenylsulfonyl ketones to nitroo-
has been one of the research focuses. For examples,
a
-fluoro-
b
-
lefins. Together with the rich chemistry of the nitro group [7], the
multiply functionalized product of such an addition could have
great potential in organic synthesis and related areas. Herein, we
report our results on this kind of reaction using amino acid and
cinchona alkaloid-derived bifunctional thiourea catalysts (Fig. 1).
keto esters have been used as nucleophiles in asymmetric Michael
additions with nitroolefins, N-alkyl maleimides and Mannich
reactions [4]. Our group has also reported the asymmetric
Robinson annulation between
a-fluoro-b-keto esters and a,b-
unsaturated ketones catalyzed by primary-secondary diamines to
synthesize multiply substituted fluorinated chiral cyclohexenones
2. Results and discussion
Initially, cinchona alkaloid based bifunctional catalyst 1, the
optimum catalyst in Prakash’s study [4j], was examined in the
model reaction of 2-fluoro-1-phenyl-2-(phenylsulfonyl)ethanone
3a to (E)-(2-nitrovinyl)benzene 4a in xylene at room temperature.
§
Dedicated to Professor Wei-Yuan Huang on the occasion of his 90th birthday.
* Corresponding author. Tel.: +86 21 54925182; fax: +86 21 64166128.
E-mail address: zhaog@mail.sioc.ac.cn (G. Zhao).
0022-1139/$ – see front matter ß 2011 Elsevier B.V. All rights reserved.
doi:10.1016/j.jfluchem.2011.05.029

H.-F. Cui et al. / Journal of Fluorine Chemistry 133 (2012) 120–126
121
Fig. 1. Structures of the catalysts studied.
Although a good yield and excellent diastereoselectivity were
gained, the enantioselectivity was not satisfactory (Table 1, entry
1). Based on our recent efforts on the development of organoca-
talysts from easily available chiral amino acids, several other
thiourea catalysts 2a–2k were synthesized and examined [7].
Variation in the chiral amino acid skeletons revealed that
phenylalanine-derived catalyst 2a is slightly better than phenyl-
glycine-derived 2b and isoleucine-derived 2c, in terms of
enantioselectivity (Table 1, entries 2–4). While changing the
substituents on the benzene ring of the group (thiourea moiety) to
electron-donating and bulky ones could lead to much improved
enantioselectivities, the yields decreased dramatically (Table 1,
entries 4–8). Pleasingly, further structural optimization by
increasing the steric hindrance of tertiary amine moiety gave rise
to the best catalyst 2k, providing the desired product 5a in high
enantioselectivity and with good yield and excellent diastereos-
electivity (Table 1, entry 12). Notably, all the catalysts with
different structures gave the same excellent d.r. value of 20:1.
Next, different solvents were tested with the optimal catalyst
2k (Table 2). In spite that the reaction performed in carbon
tetrachloride proceeded faster and gave higher yields, a slight drop
in the enantioselectivity was observed (Table 2, entries 3). In
contrast, more polar chlorine-containing solvents dichloro-
methane, chloroform or MTBE gave extremely low yields being
the lower conversion of reactants (Table 2, entries 4–6). While the
use of toluene or a co-solvent of carbon tetrachloride and xylenes
failed to provide better results, the use of pure m-xylene led to
somewhat improved overall results (Table 2, entries 7–8).
Table 1
O
F
Ph
O
Cat. (20 mol%)
NO2
NO2
SO2Ph
+
Screening of catalystsa.
.
Ph
Ph
Ph
Xylenes, rt.
SO2Ph
5a
F
3a
4a
Entry
Cat.
Yield of 5a/%b
dr. of 5ac
ee. of 5a/%d
1
2
1
85
80
75
90
70
30
33
66
95
90
95
75
20:1
20:1
20:1
20:1
20:1
20:1
20:1
20:1
20:1
20:1
20:1
20:1
70
55
60
64
68
82
89
60
73
68
75
93
2a
2b
2c
2d
2e
2f
3
4
5
6
7
8
2g
2h
2i
9
10
11
12
2j
2k
a
Unless otherwise noted, the reaction was carried out with 3a (0.1 mmol), 4a (0.15 mmol), catalyst (20 mol%) and solvent (0.5 mL) at room temperature for 3 days.
b
c
Isolated yield.
Determined by 19F NMR.
Determined by HPLC.
d

122
H.-F. Cui et al. / Journal of Fluorine Chemistry 133 (2012) 120–126
Table 2
O
F
Ph
O
2k (20 mol%)
NO2
SO2Ph
5a
NO2
SO2Ph
+
Screening of solventsa.
Ph
Ph
Ph
Solvent, rt.
F
3a
4a
Entry
Solvent
Time/h
Yield/%b
dr.c
ee./%d
1
2
Xylenes
Toluene
CCl4
72
72
48
72
72
72
72
72
72
72
75
50
95
14
10
10
90
80
85
85
20:1
20:1
20:1
20:1
20:1
20:1
20:1
20:1
20:1
20:1
93
90
90
ND
ND
ND
90
94
92
93
3
4
CHCl3
CH2Cl2
MTBE
5
6
7
Xylenes/CCl4(2:1)
m-Xylene
8
9
o-Xylene
10
p-Xylene
a
Unless otherwise noted, the reaction was carried out with 3a (0.1 mmol), 4a (0.15 mmol), catalyst (20 mol%) and solvent (0.5 mL) at room temperature.
b
c
Isolated yield.
Determined by 19F NMR.
Determined by HPLC.
d
Table 3
O
F
R2
O
2k (20 mol%)
m-Xylene, rt.
NO2
NO2
SO2Ph
R1
R2
Study on the reaction scope with different 3 and 4a.
.
1
+
R
SO2Ph
F
3
5
4
Entry
R1
R2
Time/h
Yield/%b
dr.c
ee./%d
1
2
C6H5, (3a)
CH3, (3b)
C6H5, (3a)
C6H5, (3a)
C6H5, (3a)
C6H5, (3a)
C6H5, (3a)
C6H5, (3a)
C6H5, (3a)
C6H5, (3a)
C6H5, (3a)
C6H5, (3a)
C6H5, (3a)
C6H5, (3a)
C6H5, (3a)
C6H5, (4a)
C6H5, (4a)
72
72
72
48
72
72
72
72
72
72
72
72
72
72
72
80(5a)
90(5b)
88(5c)
90(5d)
85(5e)
82(5f)
89(5g)
70(5h)
90(5i)
85(5j)
85(5k)
93(5l)
82(5m)
90(5n)
70(5o)
20:1
6:1
94
96
89
90
90
93
90
91
87
86
92
91
91
90
91
3
p-FC6H4, (4b)
p-BrC6H4, (4c)
p-CH3C6H4, (4d)
p-CH3OC6H4, (4e)
p-PhC6H4, (4f)
p-NO2C6H4, (4g)
o-BrC6H4, (4h)
m-BrC6H4, (4i)
1-Naphthyl, (4j)
2-Furyl, (4k)
14:1
17:1
20:1
10:1
20:1
14:1
15:1
15:1
20:1
20:1
16:1
5:1
4
5
6
7
8
9
10
11
12
13
14
15
2-Thienyl, (4l)
n-Bu, (4m)
i-Pr, (4n)
20:1
a
Unless otherwise noted, the reaction was carried out with 3 (0.3 mmol), 4 (0.45 mmol), catalyst (20 mol%) and solvent (3.0 mL) at room temperature.
b
c
Isolated yield.
Determined by 19F NMR.
Determined by HPLC.
d
Interestingly, the dr. value in all these cases examined also
addition of a-fluoro-b-keto esters to nitroolefins, where only
remained excellent without negligible changes.
modest dr. values (no more than 6:1) were obtained in most cases.
The absolute configuration of the major isomer of 5d was
determined by X-ray crystallographic analysis (Fig. 2), and the
others were assigned by analogy assuming a similar mechanism
was followed [8]. A possible transition state model was proposed
to explain the stereochemical results of the Michael addition. Thus,
With the optimized reaction conditions in hand, a selected
spectrum of different substrates was examined to test the scope of
this reaction (Table 3). Alkyl ketone derivative 3b (R1 = CH3) also
participated in the reaction well to give the adduct 5b in excellent
yield and enantioselectivity, albeit with a diminished diastereos-
electivity of 6:1 (Table 3, entry 2). With regard to different olefins 4,
when R2 was an aryl group, substrates with electron-donating/
withdrawing substituents on the benzene ring were generally well
tolerated, though slight drops in dr. and ee. values were observed
(Table 3, entries 3–11). Heterocyclic substrates 4k and 4l also gave
comparably good results (Table 3, entries 12–13). Notably, alkyl
substituted nitroolefins also proved to be highly applicable to the
reaction system: the bulkier 4n (R2 = i-Pr) was much more favored
over 4m (R2 = n-Bu) in terms of dr. value while both gave excellent
ee. values (Table 3, entries 14–15). It is also worth mentioning that
the excellent diastereoselectivities obtained in most cases in our
system poses a sharp contrast to Lu’s work [4c] dealing with the
Fig. 2. ORTEP structure of compound 5d.

H.-F. Cui et al. / Journal of Fluorine Chemistry 133 (2012) 120–126
123
S
R1
O
R
N
H
NH
O
O
R2
NO2
N
H
NO2
H
O
R1
SO2Ph
F
F
SO2Ph
O N
R1
F
R2
SO2Ph
R2
Si.Si
Scheme 1. Proposed transition-state structure.
F
4.1. General procedure for the Michael addition catalyzed by 2k
SO2Ph
Ph
O
Ph
Ph
Pd/C, H2 (1 atm)
NO2
Ph
The solution of 2k (6 mg, 0.01 mmol), 3a (14 mg, 0.05 mmol)
and 4a (10 mg, 0.07 mmol) in m-xylene (0.5 mL) was stirred at
room temperature and monitored by TLC. After completion (72 h),
the mixture was purified by flash chromatography (dichloro-
mathane/petro ether: 1/1) to provide white solid product 5a
17 mg, in 80% yield.
MeOH/CH2Cl2 (1:1)
N
O
SO2Ph
F
20:1dr., 94% ee.
6, 76% yield, >20:1dr., 94% ee.
5a
Scheme 2. Conversion of 5a to 6.
4.1.1. 2-Fluoro-4-nitro-1,3-diphenyl-2-(phenylsulfonyl)butan-1-one
the bifunctional chiral thiourea catalyst activated the nitroolefin
through H-bonding. The -fluoro- -phenylsulfonyl ketone
attacked the nitroolefin from the Si face leading the Michael
product of the 2S, 3S configuration (Scheme 1).
Nitrones have attracted growing interests among synthetic
chemists due to their successful applications as building blocks in
the synthesis of various natural and biologically active compounds
[9,10]. As an illustration of the utility of the present reaction, the
Michael adduct 5a was transformed to pyrrolidine-type nitrone
product 6 via a single simple hydrogenation step. The densely
functionalized cyclic nitrone 6 was obtained in good yield, and
with no decrease in dr. and ee. values (Scheme 2).
5a
a
a
White solid; Mp: 90–92 8C; [
NMR (300 MHz, CDCl3) 7.83–7.77 (m, 2H), 7.66–7.56 (m, 1H),
7.51–7.37 (m, 3H), 7.34–7.10 (m, 9H), 5.69–5.56 (m, 1H), 5.30–5.17
(m, 1H), 4.74–4.64 (m, 1H); 19F NMR (282 MHz, CDCl3)
À145.72
(d, J = 17.3 Hz, 1F); 13C NMR (100 MHz, CDCl3)
193.7 (d,
J = 25.2 Hz), 135.3, 135. 2, 134.3, 134.0, 131.6, 130.7, 129.7,
129.5, 129.5, 129.3, 129.1, 110.5 (d, J = 240.9 Hz), 75.3 (d,
J = 5.2 Hz), 47.4 (d, J = 22.2 Hz); IR (KBr)
1453, 1331, 1158 cmÀ1; ESI-MS (m/z): 450.0 (M + 23)+; HRMS (EI):
m/z: calcd. for C22H18NO5FS: 427.0890; found: 427.0892 [M]+;
HPLC separation conditions: Chiralcel ADH, 20 8C, 254 nm, 4:1
hexane:i-PrOH, 0.8 mL/min; tR = 32.0 min (minor enantiomer),
37.8 min (major enantiomer).
a]
25 = 45.1 (c = 1.34 in CHCl3); 1H
D
d
d
d
n 2933, 1675, 1560,
3. Conclusion
4.1.2. 3-Fluoro-5-nitro-4-phenyl-3-(phenylsulfonyl)pentan-2-one 5b
In summary, we have reported the organocatalyzed asymmetric
White solid; Mp: 115–116 8C; [
1H NMR (300 MHz, CDCl3)
7.89–7.72 (m, 3H), 7.63–7.54 (m, 2H),
a]
27 = 93.4 (c = 1.03 in CHCl3);
D
Michael addition of
a-fluoro-a-phenylsulfonyl ketones to nitroo-
d
lefins to afford enantiomerically enriched fluorine-containing
multifunctional molecules containing adjoining fluorine-substi-
tuted quaternary and tertiary centers. Using readily available
phenylalanine-based bifunctional thiourea derivatives as the
catalysts, the desired products were obtained with good to
excellent yield and stereoselectivity.
7.34–7.19 (m, 3H), 7.16–7.04 (m, 2H), 5.50–5.42 (m, 1H), 5.23–5.06
(m, 1H), 4.57–4.37 (m, 1H), 1.87 (d, J = 5.9 Hz, 3H); 19F NMR
(282 MHz, CDCl3)
CDCl3)
d
À148.42 (d, J = 8.0 Hz, 1F); 13C NMR (100 MHz,
d
201.5 (d, J = 27.7 Hz), 135.5, 134.2, 131.4, 130.5, 129.6,
129.4, 129.2, 129.1, 107.6 (d, J = 236.4 Hz), 74.9 (d, J = 5.9 Hz), 46.2
(d, J = 22.5 Hz), 28.7; IR (KBr) 3066, 1728, 1560, 1497, 1449, 1332,
n
1160 cmÀ1; ESI-MS (m/z): 388.1 (M + 23)+; HRMS (EI): m/z: calcd.
for C17H16NO5FS: 365.0733; found: 365.0738 [M]+; HPLC separa-
tion conditions: Chiralcel ODH, 20 8C, 254 nm, 4:1 hexane:i-PrOH,
0.7 mL/min; tR = 17.9 min (minor enantiomer), 19.1 min (major
enantiomer).
4. Experimental
Unless otherwise indicated, chemicals and solvents were
purchased from commercial suppliers and purified by standard
techniques. The 1H NMR and 13C NMR spectra were recorded on a
DPX-300 or Varian EM-360 (300 MHz) and DPX-400 (100 MHz)
with TMS as the internal standard. 19F NMR spectra were recorded
at 282 MHz with CFCl3 as the external standard. Analytical high-
performance liquid chromatography (HPLC) was carried out on
WATERS equipment using a chiral column. Melting points were
determined on a SGW X-4 apparatus, and are uncorrected. Optical
rotations were measured on a JASCO P-1030 Polarimeter at
4.1.3. 2-Fluoro-3-(4-fluorophenyl)-4-nitro-1-phenyl-2-
(phenylsulfonyl)butan-1-one 5c
Colorless oil;
[a]
25 = 36.6 (c = 1.28 in CHCl3); 1H NMR
D
(300 MHz, CDCl3)
d 7.76 (d, J = 7.2 Hz, 2H), 7.62 (t, J = 7.0 Hz,
1H), 7.53–7.34 (m, 5H), 7.30–7.11 (m, 4H), 6.91 (t, J = 8.8 Hz, 2H),
5.60–5.46 (m, 1H), 5.27–5.07 (m, 1H), 4.80–4.65 (m, 1H); 19F NMR
(282 MHz, CDCl3)
NMR (100 MHz, CDCl3) d 193.3 (d, J = 24.2 Hz), 163.1 (d,
d
À111.67 (s, 1F), À147.57 (d, J = 20.5 Hz, 1F); 13
C
l
= 589 nm. IR spectra were recorded on
a
NicoletbAV-360
instrument. Elementary analysis was taken on a Vario EL III
elementary analysis instrument. LRMS and HRMS analyses were
performed on API 200 LC/MS system (Applied Biosystems Co. Ltd.)
or APEXIII(7.0 T) FTMS mass spectrometer, respectively.
J = 249.4 Hz), 135.3, 135.1 (d, J = 4.4 Hz), 134.3, 131.6 (d,
J = 8.8 Hz), 130.6, 129.6, 129.5, 129.3, 128.3, 127.4 (d, J = 2.8 Hz),
116.1 (d, J = 21.4 Hz), 110.3 (d, J = 241.2 Hz), 75.4 (d, J = 5.3 Hz),
46.7 (d, J = 22.6 Hz); IR (film) n 3065, 1677, 1597, 1561, 1511, 1448,

124
H.-F. Cui et al. / Journal of Fluorine Chemistry 133 (2012) 120–126
1336, 1161 cmÀ1; ESI-MS (m/z): 468.0 (M + 23)+; HRMS (EI): m/z:
calcd. for C22H17NO5F2S: 445.0796; found: 445.0788 [M]+; HPLC
separation conditions: Chiralcel ADH, 20 8C, 254 nm, 4:1 hexane:i-
PrOH, 0.7 mL/min; tR = 32.5 min (minor enantiomer), 45.3 min
(major enantiomer).
J = 22.8 Hz); IR (KBr) n 2923, 1677, 1595, 1556, 1448, 1334,
1158 cmÀ1; ESI-MS (m/z): 526.2 (M + 23)+; HRMS (EI): m/z: calcd.
for C28H22NO5FS: 503.1203; found: 503.1099 [M]+; HPLC separa-
tion conditions: Chiralcel ADH, 20 8C, 254 nm, 4:1 hexane:i-PrOH,
0.9 mL/min; tR = 57.3 min (minor enantiomer), 86.9 min (major
enantiomer).
4.1.4. 2-Fluoro-3-(4-bromophenyl)-4-nitro-1-phenyl-2-
(phenylsulfonyl)butan-1-one 5d
4.1.8. 2-Fluoro-4-nitro-3-(4-nitrophenyl)-1-phenyl-2-
White solid; Mp: 130–132 8C; [
a
]
23 = 27.5 (c = 1.20 in CHCl3);
(phenylsulfonyl)butan-1-one 5h
D
1H NMR (300 MHz, CDCl3)
d
7.74 (d, J = 7.6 Hz, 2H), 7.62 (t,
Red oil; [
CDCl3) 8.09 (AB, J = 8.7 Hz, 2H), 7.76 (AB, J = 8.7 Hz, 2H), 7.62 (t,
a]
28 = 30.4 (c = 1.10 in CHCl3); 1H NMR (300 MHz,
D
J = 7.3 Hz, 1H), 7.54–7.18 (m, 9H), 7.07 (d, J = 8.4 Hz, 2H), 5.56–5.39
(m, 1H), 5.22–5.07 (m, 1H), 4.82–4.61 (m, 1H); 19F NMR (282 MHz,
d
J = 7.4 Hz, 1H), 7.50–7.37 (m, 7H), 7.23 (t, J = 8.4 Hz, 1H), 5.57–5.48
(m, 1H), 5.29–5.17 (m, 1H), 4.99–4.87 (m, 1H); 19F NMR (282 MHz,
CDCl3)
d
À147.57 (d, J = 20.5 Hz, 1F); 13C NMR (100 MHz, CDCl3)
d
193.0 (d, J = 24.0 Hz), 135.3, 135.0 (d, J = 4.2 Hz), 134.4, 134.3,
132.2, 131.4, 130.8, 130.6, 129.6 (d, J = 8.8 Hz), 129.3, 128.4, 123.7,
110.4 (d, J = 241.6 Hz), 75.2 (d, J = 4.8 Hz), 47.0 (d, J = 22.1 Hz); IR
CDCl3)
d
À1447.68 (d, J = 16.1 Hz, 1F); 13C NMR (100 MHz, CDCl3)
d
192.5 (d, J = 23.8 Hz), 148.3, 139.1, 135.6, 134.7, 134.0, 130.7,
129.6, 129.5, 129.4, 128.5, 123.9, 110.3 (d, J = 243.4 Hz), 74.9 (d,
(KBr)
n
2924, 1677, 1595, 1561, 1448, 1338, 1161 cmÀ1; ESI-MS
J = 21.4 Hz), 47.0 (d, J = 21.5 Hz); IR (film) n 3071, 1676, 1596, 1561,
(m/z): 528.1 (M + 23)+; HRMS (EI): m/z: calcd. for C22H17NO5FSBr:
504.9995; found: 504.9996 [M]+; HPLC separation conditions:
Chiralcel ADH, 20 8C, 254 nm, 4:1 hexane:i-PrOH, 0.9 mL/min;
tR = 48.9 min (minor enantiomer), 84.8 min (major enantiomer).
1448, 1349, 1160 cmÀ1; ESI-MS (m/z): 495.1 (M + 23)+; HRMS
(ESI): m/z: calcd. for C22H17N2O7FSNa: 495.0633; found: 495.0639
[M + 23]+; HPLC separation conditions: Chiralcel ASH, 20 8C,
254 nm, 4:1 hexane:i-PrOH, 0.8 mL/min; tR = 96.8 min (major
enantiomer), 129.0 min (minor enantiomer).
4.1.5. 2-Fluoro-4-nitro-1-phenyl-2-(phenylsulfonyl)-3-p-tolylbutan-
1-one 5e
Colorless oil;
(300 MHz, CDCl3)
1H), 7.52–7.30 (m, 5H), 7.29–7.15 (m, 2H), 7.11–6.91 (m, 4H),
5.67–5.49 (m, 1H), 5.28–5.10 (m, 1H), 4.74–4.55 (m, 1H); 19F NMR
(282 MHz, CDCl3)
(100 MHz, CDCl3)
J = 24.4 Hz), 135.2, 134.4, 134.0, 130.7, 129.8, 129.7, 129.6,
129.5, 129.2, 128.5, 128.2, 110.2 (d, J = 240.6 Hz), 75.5 (d,
J = 5.1 Hz), 47.1 (d, J = 22.5 Hz), 21.1; IR (film)
4.1.9. 3-(2-Bromophenyl)-2-fluoro-4-nitro-1-phenyl-2-
[
d
a
]
27 = 43.9 (c = 1.38 in CHCl3); 1H NMR
(phenylsulfonyl)butan-1-one 5i
D
7.78 (d, J = 7.7 Hz, 2H), 7.61 (t, J = 6.9 Hz,
Colorless oil; [
(300 MHz, CDCl3)
7.67–7.42 (m, 6H), 7.34–7.25 (m, 2H), 7.14–7.01 (m, 3H), 6.06–
a]
26 = -51.9 (c = 1.14 in CHCl3); 1H NMR
D
d 8.04 (d, J = 7.5 Hz, 2H), 7.74 (t, J = 7.6 Hz, 1H),
d
d
À146.23 (d, J = 11.5 Hz, 1F); 13C NMR
5.85 (m, 1H), 5.35–5.20 (m, 2H); 19F NMR (282 MHz, CDCl3)
d
193.6 (d, J = 24.4 Hz), 139.2, 135.3 (d,
À146.56 (s, 1F); 13C NMR (100 MHz, CDCl3)
d 193.8 (d,
J = 24.9 Hz), 135.7, 135.6 (d, J = 4.4 Hz), 134.2, 134.1, 133.4,
132.1, 131.2, 130.5, 129.8 (d, J = 8.1 Hz), 129.6, 128.3, 128.2,
128.1, 127.6, 109.4 (d, J = 240.7 Hz), 75.8 (d, J = 5.9 Hz), 45.3 (d,
n 2924, 1677,
1596, 1558, 1448, 1159 cmÀ1; ESI-MS (m/z): 464.1 (M + 23)+;
HRMS (EI): m/z: calcd. for C23H20NO5FS: 441.1046; found:
441.1042 [M]+; HPLC separation conditions: Chiralcel ADH,
20 8C, 254 nm, 4:1 hexane:i-PrOH, 0.6 mL/min; tR = 26.2 min
(minor enantiomer), 44.1 min (major enantiomer).
J = 23.5 Hz); IR (film) n 3020, 1711, 1561, 1445, 1376, 1216,
756 cmÀ1; ESI-MS (m/z): 528.0 (M + 23)+; HRMS (EI): m/z: calcd.
for C22H17NO5FSBr: 504.9995; found: 504.9991 [M]+; HPLC
separation conditions: Chiralcel ADH, 20 8C, 254 nm, 4:1
hexane:i-PrOH, 0.8 mL/min; tR = 29.9 min (minor enantiomer),
44.4 min (major enantiomer).
4.1.6. 2-Fluoro-3-(4-methoxyphenyl)-4-nitro-1-phenyl-2-
(phenylsulfonyl)butan-1-one 5f
4.1.10. 3-(3-Bromophenyl)-2-fluoro-4-nitro-1-phenyl-2-
White solid; Mp: 84–85 8C; [
a
]
D
25 = 42.5 (c = 1.20 in CHCl3); 1H
(phenylsulfonyl)butan-1-one 5j
NMR (300 MHz, CDCl3) 7.78 (d, J = 8.1 Hz, 2H), 7.62 (t, J = 7.2 Hz,
d
Colorless oil; [
a
]
26 = À34.1 (c = 1.03 in CHCl3); 1H NMR
D
1H), 7.48–7.33 (m, 5H), 7.23–7.21 (m, 2H), 7.08 (d, J = 7.7 Hz, 2H),
6.73 (d, J = 8.7 Hz, 2H), 5.59–5.50 (m, 1H), 5.25–5.10 (m, 1H), 4.74–
4.53 (m, 1H); 19F NMR (282 MHz, CDCl3)
1F); 13C NMR (100 MHz, CDCl3)
(300 MHz, CDCl3) d 7.76 (d, J = 7.7 Hz, 2H), 7.64 (t, J = 7.1 Hz,
1H), 7.51–7.24 (m, 9H), 7.18–7.02 (m, 2H), 5.59–5.43 (m, 1H),
d
À146.39 (d, J = 17.3 Hz,
5.25–5.04 (m, 1H), 4.79–4.57 (m, 1H); 19F NMR (282 MHz, CDCl3)
d
d
193.6 (d, J = 24.2 Hz), 160.2,
À147.68 (s, 1F); 13C NMR (100 MHz, CDCl3)
d 193.1 (d, J = 24.0 Hz),
135.5, 135.1 (d, J = 4.2 Hz), 134.3, 134.2, 133.9, 132.9, 132.5, 130.6,
130.5, 129.6 (d, J = 14.0 Hz), 129.3, 128.4, 128.3, 123.0, 110.2 (d,
135.2, 134.5, 134.0, 130.9, 130.6, 129.6, 129.5, 129.2, 128.2, 123.2,
114.4, 110.3 (d, J = 240.0 Hz), 75.5 (d, J = 4.4 Hz), 55.24, 46.7 (d,
J = 22.5 Hz); IR (KBr)
ESI-MS (m/z): 480.1 (M + 23)+; HRMS (EI): m/z: calcd. for
23H20NO6FS: 457.0995; found: 457.0993 [M]+; HPLC separation
n
2926, 1677, 1611, 1557, 1448, 1255 cmÀ1
;
J = 242.8 Hz), 75.2 (d, J = 4.5 Hz), 47.0 (d, J = 22.0 Hz); IR (film) n
3020, 1720, 1562, 1446, 1216, 758 cmÀ1; ESI-MS (m/z): 528.1
(M + 23)+; HRMS (EI): m/z: calcd. for C22H17NO5FSBr: 504.9995;
found: 505.0000 [M]+; HPLC separation conditions: Chiralcel ODH,
20 8C, 254 nm, 4:1 hexane:i-PrOH, 0.8 mL/min; tR = 23.2 min
(major enantiomer), 41.0 min (minor enantiomer).
C
conditions: Chiralcel OD-H, 20 8C, 254 nm, 4:1 hexane:i-PrOH,
0.8 mL/min; tR = 31.8 min (major enantiomer), 50.4 min (minor
enantiomer).
4.1.7. 3-(Biphenyl-4-yl)-2-fluoro-4-nitro-1-phenyl-2-
4.1.11. 2-Fluoro-3-(naphthalen-2-yl)-4-nitro-1-phenyl-2-
(phenylsulfonyl)butan-1-one 5g
(phenylsulfonyl)butan-1-one 5k
White solid; Mp: 125–126 8C; [
a
]
25 = 29.4 (c = 0.78 in CHCl3);
Colorless oil; [
a
]
D
25 = À52.2 (c = 2.00 in CHCl3); 1H NMR
D
1H NMR (300 MHz, CDCl3)
d
7.78 (d, J = 7.9 Hz, 2H), 7.60 (t,
(300 MHz, CDCl3) d 7.87–7.78 (m, 4H), 7.73–7.62 (m, 2H), 7.55–
J = 7.6 Hz, 1H), 7.48–7.39 (m, 11H), 7.35–7.30 (m, 1H), 7.24 (d,
J = 8.6 Hz, 4H), 5.59–5.51 (m, 1H), 5.26–5.20 (m, 1H), 4.83–4.73 (m,
7.45 (m, 4H), 7.39–7.30 (m, 1H), 7.27–7.08 (m, 6H), 5.98 (d,
J = 14.3 Hz, 1H), 5.78–5.70 (m, 1H), 5.43 (dd, J = 2.7, 14.1 Hz, 1H);
1H); 19F NMR (282 MHz, CDCl3)
NMR (100 MHz, CDCl3)
d
À146.51 (d, J = 16.2 Hz, 1F); 13
C
19F NMR (282 MHz, CDCl3)
(100 MHz, CDCl3) d 194.2 (d, J = 25.0 Hz), 135.5, 135.4, 134.0, 133.2,
d
À145.30 (d, J = 8.3 Hz, 1F); 13C NMR
d
193.5 (d, J = 24.1 Hz), 142.1, 139.9, 135.2,
134.4, 134.1, 130.7, 130.5, 130.2, 129.6, 129.5, 129.2, 128.9, 127.8,
130.9, 130.0, 129.6, 129.5, 129.4, 128.9, 128.7, 128.2, 127.2, 126.4,
127.6, 127.0, 110.4 (d, J = 241.4 Hz), 75.4 (d, J = 4.3 Hz), 47.2 (d,
125.4, 124.9, 123.0, 110.1 (d, J = 243.4 Hz), 76.2 (d, J = 5.3 Hz), 40.2

H.-F. Cui et al. / Journal of Fluorine Chemistry 133 (2012) 120–126
125
(d, J = 22.9 Hz); IR (film)
n
3064, 1677, 1596, 1556, 1448, 1336,
111.4 (d, J = 241.4 Hz), 72.5 (d, J = 6.7 Hz), 46.3 (d, J = 21.0 Hz), 28.1
(d, J = 3.4 Hz), 20.5, 18.9 (d, J = 2.3 Hz); IR (film) 2970, 1677, 1596,
1159 cmÀ1; ESI-MS (m/z): 500.1 (M + 23)+; HRMS (EI): m/z: calcd.
for C26H20NO5FS: 477.1046; found: 477.1043 [M]+; HPLC separa-
tion conditions: Chiralcel ADH, 20 8C, 254 nm, 4:1 hexane:i-PrOH,
0.7 mL/min; tR = 34.4 min (minor enantiomer), 62.4 min (major
enantiomer).
n
1557, 1469, 1448, 1335, 1160 cmÀ1; ESI-MS (m/z): 416.1 (M + 23)+;
HRMS (ESI): m/z: calcd. for C19H20NO5FSNa: 416.0938; found:
416.0937 [M]+; HPLC separation conditions: Chiralcel ODH, 20 8C,
254 nm, 9:1 hexane:i-PrOH, 0.7 mL/min; tR = 12.5 min (major
enantiomer), 17.6 min (minor enantiomer).
4.1.12. 2-Fluoro-3-(furan-2-yl)-4-nitro-1-phenyl-2-
(phenylsulfonyl)butan-1-one 5l
4.1.16. 4-Fluoro-3,5-diphenyl-4-(phenylsulfonyl)-3,4-dihydro-2H-
pyrrole 1-oxide 6
Red oil; [
CDCl3) 7.87 (d, J = 7.9 Hz, 2H), 7.66 (t, J = 7.3 Hz, 1H), 7.57–7.44
(m, 3H), 7.44–7.31 (m, 2H), 7.27–7.18 (m, 3H), 6.33–6.19 (m, 2H),
a]
26 = 54.2 (c = 1.40 in CHCl3); 1H NMR (300 MHz,
D
d
To the solution of 5a (40 mg, 0.1 mmol) in the mixture of
methanol (1 mL) and dichloromethane (1 mL) at room tempera-
ture was added palladium on carbon (4 mg, 10% by weight). And
the reaction mixture was stirred for 48 h under a balloon H2
atmosphere and then filtered through celite, which was subse-
quently washed with dichloromethane three times. The filtrate
was concentrated in vacuo and then separated by flash chroma-
tography (ethyl acetate/dichloromathane/petro ether:1/1/3) to
provide white solid product 6 28 mg, in 71% yield.
5.67 (d, J = 14.1 Hz, 1H), 5.28–5.08 (m, 1H), 4.89–4.68 (m, 1H); 19
F
NMR (282 MHz, CDCl3)
(100 MHz, CDCl3)
d
À144.81 (d, J = 7.1 Hz, 1F); 13C NMR
d
192.8 (d, J = 24.1 Hz), 145.2, 143.7, 135.6, 134.9
(d, J = 4.5 Hz), 134.0, 133.9, 130,8, 129.5, 129.4, 129.3, 128.2, 112.0,
111.0, 108.1 (d, J = 241.4 Hz), 73.8 (d, J = 4.5 Hz), 41.7 (d,
J = 23.5 Hz); IR (film)
n
1724, 1679, 1561 cmÀ1; ESI-MS (m/z):
440.1 (M + 23)+; HRMS (EI): m/z: calcd. for C20H16NO6FS:
417.0682; found: 417.0680 [M]+; HPLC separation conditions:
Chiralcel ODH, 20 8C, 254 nm, 4:1 hexane:i-PrOH, 0.6 mL/min;
tR = 17.7 min (major enantiomer), 37.1 min (minor enantiomer).
White solid; Mp: 120 8C. [
a
]
27 = À62.5 (c = 0.90 in CHCl3); 1H
D
NMR (300 MHz, CDCl3)
d
7.77 (d, J = 8.0 Hz, 2H), 7.60 (d, J = 8.3 Hz,
2H), 7.48 (t, J = 7.5 Hz, 1H), 7.39–7.30 (m, 3H), 7.17–7.17 (m, 5H),
7.10 (t, J = 7.6 Hz, 1H), 4.93–4.86 (m, 1H), 4.66 (d, J = 8.0 Hz, 1H),
4.1.13. 2-Fluoro-4-nitro-1-phenyl-2-(phenylsulfonyl)-3-(thiophen-
4.41 (d, J = 4.3 Hz, 1H); 19F NMR (282 MHz, CDCl3)
d
À145.45 (d,
2-yl)butan-1-one 5m
J = 5.2 Hz, 1F); 13C NMR (100 MHz, CDCl3)
d 134.8, 134.5 (d,
Red oil; [
a
]
D
25 = 35.6 (c = 1.50 in CHCl3); 1H NMR (300 MHz,
J = 6.5 Hz), 134.1, 130.5, 130.4, 129.2, 128.8, 128.7, 128.4, 128.0,
127.8, 127.7, 126.4, 114.1 (d, J = 238.4 Hz), 69.0, 42.0 (d,
CDCl3) 7.79 (d, J = 8.1 Hz, 2H), 7.63 (t, J = 7.2 Hz, 1H), 7.53–7.43
d
(m, 5H), 7.30–7.14 (m, 3H), 6.96 (d, J = 3.2, 1H), 6.89–6.79 (m, 1H),
J = 19.8 Hz); IR (film) n 3064, 1575, 1548, 1495, 1446, 1379,
5.69–5.55 (m, 1H), 5.27–5.15 (m, 1H), 5.10–4.97 (m, 1H); 19F NMR
1326, 1155, 1083 cmÀ1; ESI-MS (m/z): 396.2 (M + 1)+, 418.1
(M + 23)+; HRMS (EI): m/z: calcd. for C22H18NO3FS: 395.0991;
found: 395.0999 [M]+; HPLC separation conditions: Chiralcel OD,
20 8C, 254 nm, 4:1 hexane:i-PrOH, 0.7 mL/min; tR = 21.6 min
(major enantiomer), 25.7 min (minor enantiomer).
(282 MHz, CDCl3)
(100 MHz, CDCl3)
d
d
À144.83 (d, J = 18.4 Hz, 1F); 13C NMR
193.1 (d, J = 25.5 Hz), 135.5, 135.1 (d,
J = 4.3 Hz), 134.2, 133.4, 130.6, 129.6, 129.5, 129.5, 129.4, 128.3,
127.3, 127.2, 109.6 (d, J = 242.4 Hz), 76.5 (d, J = 4.3 Hz), 43.4 (d,
J = 22.7 Hz); IR (film)
n 3066, 1677, 1596, 1561, 1448, 1342,
1160 cmÀ1; ESI-MS (m/z): 456.1 (M + 23)+; HRMS (EI): m/z: calcd.
for C20H16NO5FS2: 433.0454; found: 433.0449 [M]+; HPLC
separation conditions: Chiralcel ODH, 20 8C, 254 nm, 4:1 hex-
ane:i-PrOH, 0.6 mL/min; tR = 21.2 min (major enantiomer),
42.3 min (minor enantiomer).
Acknowledgements
We are grateful to National Basic Research Program of China
(973 Program, 2010CB833300), National Natural Science Founda-
tion of China for financial support (Nos. 21032006, 20172064,
20532040), Shanghai Natural Science Council, and Excellent Young
Scholars Foundation of National Natural Science Foundation of
China (20525208).
4.1.14. 2-Fluoro-3-(nitromethyl)-1-phenyl-2-
(phenylsulfonyl)heptan-1-one 5n
Colorless oil;
[a]
25 = 65.1 (c = 1.30 in CHCl3); 1H NMR
D
(300 MHz, CDCl3)
d 7.91 (AB, J = 7.3 Hz, 2H), 7.78–7.65 (m, 3H),
Appendix A. Supplementary data
7.65–7.45 (m, 3H), 7.41–7.26 (m, 2H), 5.64–5.92 (m, 1H), 4.69–4.62
(m, 1H), 3.51–3.22 (m, 1H), 1.94–1.58 (m, 1H), 1.56–1.36 (m, 6H),
Supplementary data associated with this article can be found, in
the online version, at doi:10.1016/j.jfluchem.2011.05.029.
0.97–0.68 (m, 3H); 19F NMR (282 MHz, CDCl3)
d
À148.27 (d,
J = 7.1 Hz, 1F); 13C NMR (100 MHz, CDCl3)
d 193.1 (d, J = 24.2 Hz),
135.4, 135.3, 134.2, 130.1, 129.8, 129.7, 129.3, 128.5, 111.4 (d,
J = 241.1 Hz), 75.4 (d, J = 5.9 Hz), 41.7 (d, J = 17.7 Hz), 28.8 (d,
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d

126
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