Efficient enantioselective fluorination of β-keto esters/amides catalysed by diphenylamine-linked bis(thiazoline)-Cu(OTf)2 complexes

Article abstract of DOI:10.1039/c3ra45438j

An efficient highly enantioselective fluorination of β-keto esters/amides catalysed by diphenylamine-linked bis(thiazoline)-Cu(OTf) ₂ complexes has been developed. The corresponding products could be obtained with good to excellent enantioselec

Full text of DOI:10.1039/c3ra45438j

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Efficient enantioselective fluorination of b-keto
esters/amides catalysed by diphenylamine-linked
bis(thiazoline)–Cu(OTf)2 complexes†
Cite this: RSC Adv., 2014, 4, 2061
*
Jiahuan Peng and Da-Ming Du
Received 27th September 2013
Accepted 8th November 2013
An efficient highly enantioselective fluorination of b-keto esters/amides catalysed by diphenylamine-
linked bis(thiazoline)–Cu(OTf)2 complexes has been developed. The corresponding products could be
obtained with good to excellent enantioselectivities (up to > 99% ee) in excellent yields by utilizing N-
fluorobisbenzenesulphonimide (NFSI) as fluorination reagent.
DOI: 10.1039/c3ra45438j
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temperature. N-Fluorobenzenesulfonimide (NFSI) was used as
uorination reagent. To our delight we found that 2a was
Introduction
obtained in 99% ee (Scheme 1). However, uorination of tet-
ralone derivative 1b gave the corresponding products 2b in
lower stereoselectivity under the same conditions (Table 1,
entry 1). Then, our exploratory began with the optimization of
the model reaction of 1-tetralone-2-carboxylate 1b. Different
chiral bis(oxazoline) ligands (II–VI, Fig. 1) were screened in
order to improve the enantioselectivity, but the enantiose-
lectivities were even lower because of the steric effect (Table 1,
entries 2–5) and electronic effect (Table 1, entry 6). It was found
that ligand I still gave the best result among these bis(oxazoline)
ligands (Table 1, entries 1–6). Then, chiral bis(thiazoline) VII9a
and bis(imidazoline) ligands VIII and IX10 were investigated in
this reaction. Remarkably, a substantial improvement of the
enantioselectivity was realized when ligand VII was used (92%
ee) (Table 1, entry 7). Ligand VIII led to no signicant increase
in yield and enantioselectivity (Table 1, entry 8). It should be
noted that the enantioselectivity dramatically decreased when
ligand IX was used (Table 1, entry 9). This result elucidated the
crucial role of the NH group in ligands I–VIII. Triphenylamine-
tethered bis(thiazoline) ligand X has been synthesized to
further check our postulation. Low enantioselectivity was
observed as expected when ligand X was used (Table 1, entry 10).
To further investigate the reaction conditions, bis(thiazo-
line) ligand VII was chosen to explore the effect of Lewis acids
with 10 mol% catalyst loading. The results are summarized in
Table 2. A series of Lewis acid were screened. With CuOTf and
Cu(ClO4)2, both of the yield and enantioselectivity decreased
Replacement of hydrogen atoms or hydroxyl groups in the
parent compounds with uorine atoms oen leads to different
characters from the parent compounds due to the unique
properties of the carbon–uorine bond.1 The development of
effective methods to incorporate uorine into organic
compounds has been extensively exploited during the past
decade.2 Catalytic enantioselective uorination is one of the
most fascinating aspects of organouorine chemistry.3 Because
of the possibility of further derivatization, methods for the
catalytic enantioselective uorination of b-keto esters attracted
more and more attention.4 The rst example of catalytic asym-
metric uorination of b-keto esters was reported by Togni et al.5
Aer this pioneering work, chiral metal complexes4a,b,e,6 and
organocatalysts7 were developed for these reactions. Oxazoline
metal complexes have been successfully utilized in asymmetric
uorination of b-keto esters.8 However, to the best of our
knowledge, there has been no report on enantioselective uo-
rination of b-keto esters using bis(thiazoline) ligands. Herein,
we wish to detail our research on the enantioselective uori-
nation of b-keto esters/amides with NFSI as uorination
reagent, catalysed by bis(thiazoline)–Cu(OTf)2 complex.
Results and discussion
As a series of chiral bis(oxazoline) ligands were cheap and ready
available in our laboratory,9 we rst examined electrophilic
uorination of indanone carboxylate 1a in the presence of the
bis(oxazoline) I–Cu(OTf)2 complex (10 mol%) in toluene at room
School of Chemical Engineering and Environment, Beijing Institute of Technology,
Beijing 100081, People’s Republic of China. E-mail: dudm@bit.edu.cn; Tel: +86 10
68914985
† Electronic supplementary information (ESI) available: Copies of 1H and 13C
NMR spectra of new compounds, and HPLC chromatograms. See DOI:
10.1039/c3ra45438j
Scheme 1 Enantioselective fluorination of indanone carboxylate 1a.
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Table 1 Screening of ligands for the enantioselective fluorination of Table 2 Optimization of reaction conditions for the enantioselective
1-tetralone-2-carboxylate (1b)a fluorination of 1-tetralone-2-carboxylate (1b)a
Entry
Ligand
Yieldb (%)
eec (%) Entry Solvent
Lewis acid
Yieldb (%) eec (%)
1
2
3
4
5
6
7
8
9
I
II
100
58
76
51
95
67
98
93
79
62
79
12
19
6
38
18
92
77
4
1
2
3
4
5
6
7
8
Toluene
Toluene
Toluene
Toluene
Toluene
Toluene
Toluene
Toluene
Toluene
Toluene
Xylene
Cu(OTf)2
CuOTf
Cu(ClO4)2$6H2O
Cu(OAc)2$H2O
Ni(ClO4)2$6H2O
Zn(OTf)2
LiOTf
Mg(OTf)2
In(OTf)3
La(OTf)3
Cu(OTf)2
98
94
90
67
78
100
69
90
89
66
99
92
91
90
96
99
86
94
99
93
94
92
90
88
54
0
12
7
5
12
60
90
91
91
89
91
93
72
79
94
90
93
III
IV
V
VI
VII
VIII
IX
X
9
10
9
10
11
12
13
14
15
16
17
18
19d
20e
21f
a
Reactions were carried out with 1-tetralone-2-carboxylate (0.2 mmol),
Chlorobenzene
a,a,a-Triuorotoluene Cu(OTf)2
CH2Cl2
ClCH2CH2Cl
CHCl3
THF
Cycohexane
CHCl3
CHCl3
CHCl3
Cu(OTf)2
NFSI (0.24 mmol) and 10 mol% ligand–Cu(OTf)2 in toluene (3 mL).
b
Isolated yields aer column chromatography purication.
Determined by chiral HPLC analysis.
c
Cu(OTf)2
Cu(OTf)2
Cu(OTf)2
Cu(OTf)2
Cu(OTf)2
Cu(OTf)2
Cu(OTf)2
Cu(OTf)2
a
Reactions were carried out with 1-tetralone-2-carboxylate (0.2 mmol),
NFSI (0.24 mmol) and 10 mol% VII–Lewis acid in solvent (3 mL).
b
Isolated yields aer column chromatography purication.
c
d
Determined by chiral HPLC analysis. The reaction temperature was
e
f
0
ꢀC. 5 mol% VII–Cu(OTf)2 was used. 12 mol% of VII and 10 mol%
Cu(OTf)2 was used.
entries 14–16). Chloroform was the best choice of solvent with
99% yield and 93% ee (Table 2, entry 16). Solvent effect was
observed when THF and cyclohexane were utilized as solvent
(Table 2, entries 17 and 18). The enantioselectivity of the
product 2b was improved slightly by lowering the reaction
temperature (94% ee) (Table 2, entry 19). When the catalyst
Fig. 1 Chiral tridentate ligands.
slightly (Table 2, entries 2 and 3). While Cu(OAc)2 and La(OTf)3 loading was decreased to 5 mol%, the enantioselectivity
gave moderate yields and enantioselectivities (Table 2, entries 4 decreased slightly (90% ee) and 93% yield was obtained
and 10). The reaction gave no enantioselectivity when (Table 2, entry 20). No improvement of the enantioselectivity
Ni(ClO4)2$6H2O was used as Lewis acid (Table 2, entry 5). was observed when 12 mol% VII and 10 mol% Cu(OTf)2 was
Besides, Zn(OTf)2, LiOTf, Mg(OTf)2 and In(OTf)3 gave very low used (Table 2, entry 21).
enantioselectivities with moderate to high yields (Table 2,
With the optimum reaction conditions in hand, we explored
entries 6–9). The complex VII–Cu(OTf)2 was found to be the best the substrate scope for this reaction. The results are summa-
choice of catalyst affording excellent yield and high enantiose- rized in Table 3. All the substrates reacted smoothly to afford
lectivity (Table 2, entry 1).
products 2 with good to excellent yields. The alkoxy group in the
In order to improve the enantioselectivity of this asymmetric b-keto ester has no inuence on enantioselectivity of the
uorination reaction, we further screened different solvents, product. Fluorination of tetralone derivatives such as 1c and 1d
temperature and catalyst loading. Utilizing aromatic solvent gave the corresponding products in high enantioselectivities
gave the product 2b in high to excellent yields and high enan- (94% ee and 93% ee, respectively) (Table 3, entries 3 and 4). It
tioselectivities (Table 2, entries 1 and 11–13). When alkyl was found that excellent enantioselectivities could be obtained
halides were used as solvent, 1b reacted smoothly to afford the for all indanonecarboxylate derivatives (Table 3, entries 1 and
product with high yields and high enantioselectivities (Table 2, 5–11). The enantioselectivity of the reaction was above 99% ee
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Table 3 Scope of the enantioselective fluorination of b-keto esters/amides 1a
Entry
R1
R2
R3
n
Substrate
Product
Yieldb (%)
eec (%)
1
2
3
4
OEt
OEt
H
H
H
H
H
H
H
Me
OMe
H
H
H
H
H
H
H
H
H
H
H
OMe
Cl
Br
H
H
H
1
2
2
2
1
1
1
1
1
1
1
1
1
1
1a
1b
1c
1d
1e
1f
1g
1h
1i
1j
1k
1l
1m
1n
2a
2b
2c
2d
2e
2f
2g
2h
2i
2j
2k
2l
2m
2n
100
99
92
100
96
93
100
100
91
89
96
99
93
94
OBn
OMe
OiPr
OtBu
OBn
OEt
OEt
OEt
OEt
93
5
>99
99 (S)
99
6d
7
8
9
99
98
99
99
83
94
73
10
11
12
13
14
NHnBu
NHPh
NHBn
100
100
95
H
H
a
b
Reactions were carried out with 1 (0.2 mmol), NFSI (0.24 mmol) and 10 mol% VII–Cu(OTf)2 in CHCl3 (3 mL). Isolated yields aer column
c
d
chromatography purication. Determined by chiral HPLC analysis. The absolute conguration of 2f was assigned as S based on comparison
of the optical rotation with previous report.8c
when the ester alkoxy substituent was isopropoxy group
(Table 3, entry 5). Electron-rich substituent such as, methoxy
group on the aromatic ring of indanonecarboxylate derivative
caused slight decrease in enantioselectivity (Table 3, entry 9).
Indanone carboxamides were also evaluated in this reaction.
Excellent yields and lower enantioselectivities were obtained.
The alkylamino groups in the indanonecarboxamides have
important inuence on enantioselectivities. In the case of 1l
(Table 3, entry 12), the enantioselectivity of the product 2l has a
moderate decrease (83% ee). N-Phenyl-carboxamide 1m caused
Fig. 2 Acyclic, aliphatic b-keto ester and 1,3-dione substrates evalu-
ated in this reaction.
slight decrease in enantioselectivity (94% ee) (Table 3, entry 13).
When N-benzyl-carboxamide 1n was used as substrate, the
enantioselectivity decreased to 73% ee (Table 3, entry 14).
Acyclic substrates, such as 1o–1r (Fig. 2) were also evaluated in
this reaction. Unfortunately, no corresponding products were
obtained when 1p–1r were used as substrates. Substrate 1o
afforded racemic product in 42% yield. Besides, aliphatic
cyclopentanone-derived ester 1s and cyclohexanone-derived
ester 1t were also evaluated in this reaction. Racemic product
was obtained with 46% yield in the case of 1s. While 1t did not
afford the corresponding product in the same condition. 1,3-
Dione 1u afforded the corresponding product 2u with no
enantioselectivity and in 79% yield. The above experimental
results indicated that the substrate structures inuenced the
yields and enantioselectivities, tetralone and indanone carbox-
ylate derivatives with fused aromatic ring demonstrate excellent
reactivity and enantioselectivity, this may be ascribed to the
existence of aromatic p–p interaction between the substrate
and phenyl substituent in oxazoline ligand. This interaction has
also been demonstrated by the ligand screening results in Table
groups in oxazoline ring, afforded good catalytic performance
compared with other substituted ligands in same reaction.
On the basis of the conguration of the product 2f and the
activate model of the similar ligand we have published before,9
1 (entries 1, 7 and 8), ligands I, VII and VIII which have phenyl Fig. 3 Proposed transition state model.
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we proposed a transition state model for the uorination as became clear. The (S)-2-amino-2-phenylethanol (617 mg, 4.5
illustrated in Fig. 3. The bis(thiazoline)–Cu(OTf)2 catalyst acts in mmol) was added, and the solution was stirred at room
a bifunctional fashion, the Lewis acid activates the b-keto ester temperature for 48 h. The reaction was quenched by addition of
through coordination of the copper cation with the two oxygen 30 mL of saturated NH4Cl (aq.). The phase was separated, and
atoms in b-keto ester. The NH–O hydrogen bond interaction the organic phase was washed with saturated NaHCO3 (aq.) and
and p–p interaction directs the NFSI attack from the Si-face and brine. Aer drying over anhydrous Na2SO4, the solvent was
result in the (S)-congured product 2f.
removed in vacuo and the crude product was puried by silica
gel column chromatography using CH2Cl2/CH3OH (50 : 1) as
eluent. The product bis(hydroxyamide) was obtained (549.7 mg,
48% yield) as yellow oil. To a solution of bis(hydroxyamide)
(549.7 mg, 0.96 mmol) in dry pyridine (10 mL) was added P2S5
(852.5 mg, 3.84 mmol) and the mixture was reuxed for 22 h.
Then the reaction was cooled and 20% KOH solution (10 mL)
was added. The aqueous phase was extracted with DCM (10 mL
ꢁ 3). The organic phase was combined, washed by 2 N HCl,
dried over anhydrous Na2SO4 and concentrated under reduced
pressure to give the crude product. Puried by silica gel column
chromatography using petroleum ether/ethyl acetate (15 : 1) as
eluent. The product was obtained (53.8 mg, 10% yield) as a
yellow solid. M.p. 76–79 ꢀC; [a]D28 ꢂ95.4 (c 2.00, CH2Cl2); 1H NMR
(400 MHz, CDCl3): d 7.56 (d, J ¼ 7.6 Hz, 2H, ArH), 7.35–7.27 (m,
4H, ArH), 7.20–7.14 (m, 5H, ArH), 7.10 (t, J ¼ 7.4 Hz, 3H, ArH),
7.03 (t, J ¼ 7.2 Hz, 3H, ArH), 6.96 (d, J ¼ 7.6 Hz, 3H, ArH), 6.81 (t,
J ¼ 6.8 Hz, 1H, ArH), 6.74 (d, J ¼ 8.4 Hz, 2H, ArH), 5.03 (t, J ¼ 9.8
Hz, 2H, CH), 3.31 (t, J ¼ 9.4 Hz, 2H, CH2), 2.71 (t, J ¼ 11.0 Hz,
2H, CH2) ppm; 13C NMR (100 MHz, CDCl3): d 167.1, 147.9,
146.0, 141.5, 131.4, 131.0, 130.4, 129.4, 128.3, 128.2, 127.3,
126.8, 124.4, 121.9, 121.0, 79.9, 41.5 ppm; IR (KBr): n 3061, 3028,
2924, 1714, 1590, 1481, 1442, 1361, 1316, 1276, 1221, 1019, 947,
913, 757, 695 cmꢂ1. HRMS (ESI positive): m/z calcd for
Conclusions
In conclusion, we have developed an efficient enantioselective
uorination reaction of b-keto esters/amides 1 catalysed by a
tridentate bis(thiazoline) VII–Cu(OTf)2 complex. The corre-
sponding products were obtained in good to excellent yields
with good to excellent enantioselectivities (up to > 99% ee). This
reaction provides a valuable alternative route to uoro-bearing
b-keto esters or amides. The asymmetric uorination or related
reactions using bis(thiazoline), bi(oxazoline) or bis(imidazo-
line) ligand–metal complexes will be further investigated in our
laboratory.
Experimental
General information
Unless otherwise stated, commercially available compounds
were used without further purication. Column chromatog-
raphy was carried out with silica gel (200–300 mesh). Melting
points were measured with a MT-4 melting point apparatus
1
without correction. H NMR spectra were recorded with a Var-
ian Mercury-plus 400 MHz spectrometer. Chemical shis were
reported in ppm with the internal TMS signal at 0.0 ppm as a
standard. The data are reported as follows: chemical shi
(ppm), and multiplicity (s ¼ singlet, d ¼ doublet, t ¼ triplet, q ¼
quartet, m ¼ multiplet or unresolved, br s ¼ broad singlet),
coupling constant(s) in Hz, integration assignment. 13C NMR
spectra were recorded at 100 MHz. Infrared spectra were
obtained with a Perkin Elmer Spectrum One spectrometer. The
high resolution MS spectra were obtained with ESI positive
ionization using a Bruker APEX IV FT-MS spectrometer. Optical
C
36H30N3S2 [M + H]+ 568.18757, found: 568.18641.
General procedure for the asymmetric uorination of b-keto
esters/amides
To a dried Schlenk tube were added Cu(OTf)2 (7.1 mg,
0.02 mmol) and ligand VII (9.8 mg, 0.02 mmol) under argon
followed by addition of the CHCl3 (3 mL). The solution was
stirred at room temperature for 0.5 h and then b-keto esters/
amides 1 (0.2 mmol) was added. The mixture was stirred for
10 min, then NFSI (75.7 mg, 0.24 mmol) was added. Aer stir-
ring for 15 h at room temperature, the solvent was removed
under vacuum. Purication by column chromatography affor-
ded the desired product 2.
¨
rotations were measured with a Kruss P8000 or WZZ-3 polarim-
eter at the indicated concentration with unit g per 100 mL. The
enantiomeric excesses were determined by chiral HPLC using an
Agilent 1200 LC instrument with Daicel Chiralpak IA, IB and AD-
H columns, or Daicel Chiralcel OB-H and OD-H columns.
Ethyl
2-uoro-2,3-dihydro-1-oxo-1H-indene-2-carboxylate
(2a).7c The title compound 2a was obtained according to the
Materials
general procedure as colorless oil (44.4 mg, 100% yield). HPLC
Chiral bis(oxazoline) I–VI1,9 chiral bis(thiazoline) VII,9b chiral (Daicel Chiralpak IB, n-hexane–2-propanol 98 : 2, ow rate
bis (imidazoline) VIII,10a chiral bis (imidazoline) IX,10b b-keto 1.0 mL minꢂ1, detection at 254 nm): tmajor ¼ 11.3 min, tminor
¼
esters 1 (ref. 11) and b-keto amides 1 (ref. 12) were prepared 12.3 min, 99% ee. [a]2D8 ꢂ7.7 (c 1.63, CH2Cl2); 1H NMR (400 MHz,
according to the reported procedures.
CDCl3): d 7.84 (d, J ¼ 7.6 Hz, 1H, ArH), 7.71 (t, J ¼ 7.6 Hz, 1H,
2-((S)-4,5-Dihydro-4-phenylthiazol-2-yl)-N-(2-((S)-4,5-dihydro- ArH), 7.51 (d, J ¼ 8.0 Hz, 1H, ArH), 7.47 (t, J ¼ 7.6 Hz, 1H, ArH),
4-phenylthiazol-2-yl)phenyl)-N-phenylbenzenamine (X). To a 4.29 (q, J ¼ 7.2 Hz, 2H, CH2), 3.80 (dd, J1 ¼ 17.6 Hz, J2 ¼ 11.6 Hz,
100 mL ask were added 2,20-dicarboxyltriphenylamine 1H, CH2), 3.44 (dd, J1 ¼ 23.2 Hz, J2 ¼ 17.6 Hz, 1H, CH2), 1.26 (t,
(666 mg, 2 mmol), EDCI–HCl (900 mg, 4.5 mmol), DMAP J ¼ 7.0 Hz, 3H, CH3) ppm; 13C NMR (100 MHz, CDCl3): d 195.2
2
2
3
(25 mg, 0.2 mmol), and CH2Cl2 (35 mL). Then N-methyl- (d, JCF ¼ 18.1 Hz), 167.2 (d, JCF ¼ 27.2 Hz), 150.8 (d, JCF
¼
morpholine (0.72 mL, 6.5 mmol) was added, and the mixture 3.6 Hz), 136.6, 133.1, 128.5, 126.5, 125.5, 94.4 (d, 1JCF ¼ ꢂ200.3
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2
Hz), 62.5, 38.2 (d, JCF ¼ 23.7 Hz), 13.9 ppm. lit.7c [a]D20 ꢂ18.4 1H, ArH), 5.18–5.12 (m, 1H, CH), 3.77 (dd, J1 ¼ 17.6 Hz, J2 ¼
(c 0.14, CHCl3, 90% ee).
Ethyl
11.6 Hz, 1H, CH2), 3.43 (dd, J1 ¼ 23.4 Hz, J2 ¼ 17.8 Hz, 1H, CH2),
2-uoro-1,2,3,4-tetrahydro-1-oxonaphthalene-2- 1.26 (d, J ¼ 6.0 Hz, 3H, CH3), 1.23 (d, J ¼ 6.4 Hz, 3H, CH3) ppm;
carboxylate (2b).6d,7a The title compound 2b was obtained 13C NMR (100 MHz, CDCl3): d 195.4 (d, 2JCF ¼ 18.0 Hz), 166.8 (d,
according to the general procedure as colorless oil (46.5 mg, 2JCF ¼ 27.4 Hz), 150.9 (d, JCF ¼ 3.3 Hz), 136.6, 133.3, 128.5,
3
1
2
99% yield). HPLC (Daicel Chiralpak OB-H, n-hexane–2-propanol 126.5, 125.5, 94.4 (d, JCF ¼ ꢂ199.5 Hz), 70.7, 38.2 (d, JCF
¼
90 : 10, ow rate 1.0 mL minꢂ1, detection at 254 nm): tmajor
¼
23.9 Hz), 21.5, 21.4 ppm. lit.7c [a]D20 ꢂ12.51 (c 0.12, CHCl3,
17.0 min, tminor ¼ 21.4 min, 93% ee. [a]2D8 ꢂ2.2 (c 4.63, CH2Cl2); 81% ee).
1H NMR (400 MHz, CDCl3): d 8.08 (d, J ¼ 8.0 Hz, 1H, ArH), 7.56
(S)-tert-Butyl 2-uoro-2,3-dihydro-1-oxo-1H-indene-2-carbox-
(t, J ¼ 7.6 Hz, 1H, ArH), 7.37 (t, J ¼ 7.6 Hz, 1H, ArH), 7.29 (d, J ¼ ylate (2f).7b,8c The title compound 2f was obtained according to
7.6 Hz, 1H, ArH), 4.30 (q, J ¼ 7.2 Hz, 2H, CH2), 3.23–3.16 (m, 1H, the general procedure as colorless oil (46.6 mg, 93% yield).
CH2), 3.12–3.05 (m, 1H, CH2), 2.80–2.68 (m, 1H, CH2), 2.60–2.50 HPLC (Daicel Chiralpak AD-H, n-hexane–2-propanol 98 : 2, ow
(m, 1H, CH2), 1.28 (t, J ¼ 7.0 Hz, 3H, CH3) ppm; 13C NMR rate 1.0 mL minꢂ1, detection at 254 nm): tminor ¼ 9.4 min,
2
2
1
(100 MHz, CDCl3): d 188.6 (d, JCF ¼ 18.6 Hz), 167.3 (d, JCF
¼
¼
tmajor ¼ 10.6 min, 99% ee. [a]2D8 ꢂ5.9 (c 2.33, CH2Cl2); H NMR
25.5 Hz), 143.1, 134.5, 130.5, 128.7, 128.4, 127.2, 93.1 (d, 1JCF
(400 MHz, CDCl3): d 7.83 (d, J ¼ 8.0 Hz, 1H, ArH), 7.69 (t, J ¼
ꢂ192.8 Hz), 62.4, 31.8 (d, 2JCF ¼ 22.0 Hz), 24.8 (d, 3JCF ¼ 7.3 Hz), 7.4 Hz, 1H, ArH), 7.50 (d, J ¼ 7.6 Hz, 1H, ArH), 7.46 (t, J ¼ 7.4 Hz,
14.0 ppm. lit.6d [a]D20 +0.2 (c 1.25, MeOH, 20% ee); lit.7a [a]D25 +7.8 1H, ArH), 3.73 (dd, J1 ¼ 17.6 Hz, J2 ¼ 10.8 Hz, 1H, CH2), 3.40 (dd,
(c 1.0, CHCl3, 40% ee) for opposite enantiomer.
Benzyl
J1 ¼ 22.8 Hz, J2 ¼ 17.6 Hz, 1H, CH2), 1.43 (s, 9H, CH3) ppm; 13
C
2
2-uoro-1,2,3,4-tetrahydro-1-oxonaphthalene-2- NMR (100 MHz, CDCl3): 195.7 (d, JCF ¼ 18.2 Hz), 166.2 (d,
carboxylate (2c).8a The title compound 2c was obtained 2JCF ¼ 27.3 Hz), 150.9 (d, JCF ¼ 4.0 Hz), 136.4, 133.5, 128.4,
3
1
2
according to the general procedure as colorless oil (54.9 mg, 126.4, 125.3, 94.3 (d, JCF ¼ ꢂ200.2Hz), 84.0, 38.3 (d, JCF
¼
92% yield). HPLC (Daicel Chiralpak OD-H, n-hexane–2-propanol 24.0 Hz), 27.7 ppm. lit.8c [a]D24 ꢂ3.93 (c 0.41, CHCl3, 99% ee); lit.7b
70 : 30, ow rate 1.0 mL minꢂ1, detection at 254 nm): tmajor
¼
[a]2D9 ꢂ3.34 (c 0.35, CHCl3, 96% ee).
12.0 min, tminor ¼ 17.6 min, 94% ee. [a]2D8 +1.8 (c 2.74, CH2Cl2);
Benzyl 2-uoro-2,3-dihydro-1-oxo-1H-indene-2-carboxylate
1H NMR (400 MHz, CDCl3): d 8.07 (d, J ¼ 8.0 Hz, 1H, ArH), 7.54 (2g).7c,8a The title compound 2g was obtained according to the
(t, J ¼ 7.4 Hz, 1H, ArH), 7.33–7.23 (m, 7H, ArH), 5.29 (d, J ¼ general procedure as colorless oil (56.9 mg, 100% yield). HPLC
12.4 Hz, 1H, CH2), 5.21 (d, J ¼ 12.4 Hz, 1H, CH2), 3.18–3.11 (m, (Daicel Chiralpak IB, n-hexane–2-propanol ¼ 98 : 2, ow rate
1H, CH2), 3.03–2.96 (m, 1H, CH2), 2.78–2.65 (m, 1H, CH2), 2.58– 1.0 mL minꢂ1, detection at 254 nm): tmajor ¼ 18.3 min, tminor
¼
2.49 (m, 1H, CH2) ppm; 13C NMR (100 MHz, CDCl3): d 188.4 (d, 20.2 min, 99% ee. [a]2D8 ꢂ6.3 (c 2.86, CH2Cl2); 1H NMR (400 MHz,
2JCF ¼ 18.3 Hz), 167.1 (d, JCF ¼ 25.8 Hz), 143.0, 134.6, 134.5, CDCl3): d 7.83 (d, J ¼ 7.6 Hz, 1H, ArH), 7.69 (t, J ¼ 7.6 Hz, 1H,
2
1
130.5, 128.7, 128.5, 128.4, 128.3, 127.9, 127.2, 93.2 (d, JCF
¼
ArH), 7.49–7.44 (m, 2H, ArH), 7.35–7.23 (m, 5H, ArH), 5.27 (d,
ꢂ192.9 Hz), 67.6, 31.8 (d, 2JCF ¼ 21.9 Hz), 24.7 (d, 3JCF ¼ 7.3 Hz) J ¼ 12.4 Hz, 1H, CH2), 5.21 (d, J ¼ 12.4 Hz, 1H, CH2), 3.77 (dd,
ppm. lit.8a [a]2D0 +24.0 (c 1.2, MeOH, 38% ee).
J1 ¼ 17.8 Hz, J2 ¼ 11.4 Hz, 1H, CH2), 3.43 (dd, J1 ¼ 23.0 Hz, J2 ¼
Methyl
2-uoro-1,2,3,4-tetrahydro-1-oxonaphthalene-2- 17.8 Hz, 1H, CH2) ppm; 13C NMR (100 MHz, CDCl3): d 195.0 (d,
carboxylate (2d).4f,7a The title compound 2d was obtained 2JCF ¼ 18.6 Hz), 167.1 (d, 2JCF ¼ 27.9 Hz), 150.7 (d, 3JCF ¼ 3.5 Hz),
according to the general procedure as colorless oil (44.4 mg, 136.7, 134.6, 133.2, 128.6, 128.6, 128.5, 127.9, 126.5, 125.6, 94.6
1
2
100% yield). HPLC (Daicel Chiralpak OB-H, n-hexane–2-prop- (d, JCF ¼ ꢂ200.8 Hz), 67.8, 38.2 (d, JCF ¼ 23.7 Hz) ppm. lit.8a
anol 90 : 10, ow rate 1.0 mL minꢂ1, detection at 254 nm): [a]D20 ꢂ6.0 (c 1.99, MeOH, 35% ee); lit.7c [a]D20 ꢂ5.0 (c 0.10, CHCl3,
tmajor ¼ 23.2 min, tminor ¼ 29.4 min, 93% ee. [a]2D8 ꢂ2.3 (c 3.75, 95% ee).
CH2Cl2); 1H NMR (400 MHz, CDCl3): d 8.08 (d, J ¼ 7.6 Hz, 1H,
Ethyl
2-uoro-2,3-dihydro-6-methyl-1-oxo-1H-indene-2-
ArH), 7.56 (t, J ¼ 7.4 Hz, 1H, ArH), 7.38 (t, J ¼ 7.6 Hz, 1H, ArH), carboxylate (2h). The title compound 2h was obtained accord-
7.29 (d, J ¼ 7.6 Hz, 1H, ArH), 3.83 (s, 3H, CH3), 3.23–3.16 (m, ing to the general procedure as yellow oil (47.0 mg, 100% yield).
1H, CH2), 3.13–3.05 (m, 1H, CH2), 2.80–2.68 (m, 1H, CH2), HPLC (Daicel Chiralpak IB, n-hexane–2-propanol 98 : 2, ow
2.60–2.51 (m, 1H, CH2) ppm; 13C NMR (100 MHz, CDCl3): d rate 1.0 mL minꢂ1, detection at 254 nm): tmajor ¼ 10.8 min,
2
188.4 (d, JCF ¼ 18.4 Hz), 167.7, 143.1, 134.6, 130.4, 128.7, tminor ¼ 12.7 min, 99% ee. [a]2D8 ꢂ19.7 (c 2.35, CH2Cl2); 1H NMR
1
2
128.4, 127.2, 93.2 (d, JCF ¼ ꢂ192.8 Hz), 53.0, 31.8 (d, JCF
¼
(400 MHz, CDCl3): d 7.63 (s, 1H, ArH), 7.53 (dd, J1 ¼ 8.0 Hz, J2 ¼
3
22.0 Hz), 24.8 (d, JCF ¼ 7.1 Hz) ppm. lit.4f [a]D20 +6.12 (c 0.4, 1.6 Hz, 1H, ArH), 7.40 (d, J ¼ 8.0 Hz, 1H, ArH), 4.28 (q, J ¼
CHCl3, 41% ee); lit.7a [a]D25 +4.72 (c 1.0, CHCl3, 30% ee) for 7.2 Hz, 2H, CH2), 3.74 (dd, J1 ¼ 17.6 Hz, J2 ¼ 11.2 Hz, 1H, CH2),
opposite enantiomer.
3.38 (dd, J1 ¼ 23.2 Hz, J2 ¼ 17.6 Hz, 1H, CH2), 2.43 (s, 3H, CH3),
Propyl 2-uoro-2,3-dihydro-1-oxo-1H-indene-2-carboxylate 1.26 (t, J ¼ 7.2 Hz, 3H, CH3) ppm; 13C NMR (100 MHz, CDCl3): d
2
2
(2e).7c The title compound 2e was obtained according to the 195.3 (d, JCF ¼ 18.5 Hz), 167.3 (d, JCF ¼ 27.9 Hz), 148.3 (d,
general procedure as colorless oil (45.1 mg, 96% yield). HPLC 3JCF ¼ 3.5 Hz), 138.7, 138.0, 133.3, 126.2, 125.3, 94.8 (d, JCF
¼
1
2
(Daicel Chiralpak AD-H, n-hexane–2-propanol 98 : 2, ow rate ꢂ199.9 Hz), 62.5, 37.9 (d, JCF ¼ 23.8 Hz), 21.0, 13.9 ppm; IR
1.0 mL minꢂ1, detection at 254 nm): tminor ¼ 10.2 min, tmajor
¼
(KBr): n 2984, 2931, 1766, 1726, 1616, 1584, 1495, 1425, 1370,
10.8 min, 99.6% ee. [a]2D8 ꢂ23.3 (c 2.26, CH2Cl2); 1H NMR 1284, 1225, 1193, 1104, 1074, 1014, 958, 860, 826, 796, 761,
(400 MHz, CDCl3): d 7.84 (d, J ¼ 8.0 Hz, 1H, ArH), 7.71 (t, J ¼ 690 cmꢂ1. HRMS (ESI positive): m/z calcd for C13H14FO3 [M +
7.6 Hz, 1H, ArH), 7.51 (d, J ¼ 7.6 Hz, 1H, ArH), 7.47 (t, J ¼ 7.6 Hz, H]+ 237.09215, found: 237.09207.
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ow rate 1.0 mL minꢂ1, detection at 254 nm): tmajor ¼ 8.4 min,
tminor ¼ 9.2 min, 83% ee. [a]2D8 ꢂ37.1 (c 2.41, CH2Cl2); 1H NMR
(400 MHz, CDCl3): d 7.84–7.78 (m, 1H, ArH), 7.67 (t, J ¼ 7.4 Hz,
1H, ArH), 7.55–7.40 (m, 2H, ArH), 6.65 (s, 1H, CONH), 3.96 (dd,
J1 ¼ 17.6 Hz, J2 ¼ 11.6 Hz, 1H, CH2), 3.36–3.26 (m, 3H, CH2),
1.59–1.52 (m, 2H, CH2), 1.43–1.34 (m, 2H, CH2), 0.94 (t, J ¼
7.2 Hz, 3H, CH3) ppm; 13C NMR (100 MHz, CDCl3): d 196.7 (d,
Ethyl 2-uoro-2,3-dihydro-5,6-dimethoxy-1-oxo-1H-indene-2-
carboxylate (2i). The title compound 2i was obtained according
to the general procedure as yellow solid (51.3 mg, 91% yield).
M.p. 95–97 ꢀC. HPLC (Daicel Chiralpak OJ-H, n-hexane–2-
propanol 70 : 30, ow rate 1.0 mL minꢂ1, detection at 210 nm):
tmajor ¼ 31.4 min, tminor ¼ 50.0 min, 98% ee. [a]2D8 ꢂ99.3 (c 2.56,
CH2Cl2); 1H NMR (400 MHz, CDCl3): d 7.22 (s, 1H, ArH), 6.92 (s,
1H, ArH), 4.29 (q, J ¼ 7.2 Hz, 2H, CH2), 4.01 (s, 3H, OCH3), 3.93
(s, 3H, OCH3), 3.71 (dd, J1 ¼ 17.4 Hz, J2 ¼ 10.6 Hz, 1H, CH2), 3.34
2
2JCF ¼ 17.6 Hz), 166.7 (d, JCF ¼ 21.7 Hz), 151.9, 136.6, 133.3,
1
128.3, 126.4, 125.3, 96.8 (d, JCF ¼ ꢂ202.4 Hz), 39.2, 37.4 (d,
2JCF ¼ 22.6 Hz), 31.4, 19.9, 13.6 ppm. IR (KBr): n 3275, 3081,
2950, 2929, 2864, 1735, 1663, 1607, 1589, 1553, 1466, 1372,
1301, 1215, 1202, 1155, 1073, 912, 750, 720 cmꢂ1. HRMS (ESI
positive): m/z calcd for C14H17FNO2 [M + H]+ 250.12378, found:
250.12358.
(dd, J1 ¼ 22.4 Hz, J2 ¼ 17.2 Hz, 1H, CH2), 1.28 (t, J ¼ 7.2 Hz, 3H,
2
CH3) ppm; 13C NMR (100 MHz, CDCl3): d 193.5 (d, JCF
¼
¼
18.4 Hz), 167.5 (d, 2JCF ¼ 27.5 Hz), 157.0, 150.1, 146.9 (d, 3JCF
1
4.0 Hz), 125.9, 107.2, 105.3, 94.9 (d, JCF ¼ ꢂ199.8 Hz), 62.4,
2
56.4, 56.1, 37.9 (d, JCF ¼ 24.0 Hz), 14.0 ppm; IR (KBr): n 3081,
2-Fluoro-2,3-dihydro-1-oxo-N-phenyl-1H-indene-2-carbox-
amide (2m). The title compound 2m was obtained according to
the general procedure as colorless solid (53.9 mg, 100% yield).
M.p. 198–202 ꢀC. HPLC (Daicel Chiralpak IB, n-hexane–2-
propanol 90 : 10, ow rate 1.0 mL minꢂ1, detection at 254 nm):
tminor ¼ 12.4 min, tmajor ¼ 16.1 min, 94% ee. [a]2D8 ꢂ78.0 (c 2.74,
CH2Cl2); 1H NMR (400 MHz, (CD3)2SO): d 10.45 (s, 1H, CONH),
7.85–7.80 (m, 2H, ArH), 7.72 (dd, J1 ¼ 8.8 Hz, J2 ¼ 1.2 Hz, 2H,
ArH), 7.68 (d, J ¼ 7.6 Hz, 2H, ArH), 7.55 (t, J ¼ 7.6 Hz, 1H, ArH),
7.34 (t, J ¼ 8.0 Hz, 2H, ArH), 7.13 (t, J ¼ 7.4 Hz, 1H, ArH), 3.90
(dd, J1 ¼ 18.0 Hz, J2 ¼ 12.4 Hz, 1H, CH2), 3.53 (dd, J1 ¼ 24.8 Hz,
J2 ¼ 18.0 Hz, 1H, CH2) ppm; 13C NMR (100 MHz, (CD3)2SO): d
2981, 2941, 2840, 1763, 1713, 1605, 1590, 1505, 1466, 1443,
1427, 1370, 1325, 1275, 1225, 1192, 1103, 1074, 996, 920, 862,
776 cmꢂ1. HRMS (ESI positive): m/z calcd for C14H16FO5 [M +
H]+ 283.09763, found: 283.09793.
Ethyl
5-chloro-2-uoro-2,3-dihydro-1-oxo-1H-indene-2-
carboxylate (2j). The title compound 2j was obtained according
to the general procedure as yellow solid (45.5 mg, 89% yield).
M.p. 58–60 ꢀC. HPLC (Daicel Chiralpak IB, n-hexane–2-propanol
98 : 2, ow rate 1.0 mL minꢂ1, detection at 254 nm): tmajor
¼
12.1 min, tminor ¼ 13.5 min, 99% ee. [a]2D8 ꢂ62.7 (c 2.11, CH2Cl2);
1H NMR (400 MHz, CDCl3): d 7.78 (d, J ¼ 8.0 Hz, 1H, ArH), 7.52
(s, 1H, ArH), 7.46 (d, J ¼ 8.0 Hz, 1H, ArH), 4.29 (q, J ¼ 7.2 Hz, 2H,
CH2), 3.78 (dd, J1 ¼ 18.0 Hz, J2 ¼ 11.2 Hz, 1H, CH2), 3.42 (dd,
J1 ¼ 22.8 Hz, J2 ¼ 17.6 Hz, 1H, CH2), 1.27 (t, J ¼ 7.2 Hz, 3H, CH3)
2
2
196.9 (d, JCF ¼ 18.1 Hz), 165.7 (d, JCF ¼ 23.2 Hz), 152.1 (d,
3JCF ¼ 3.5 Hz), 137.3, 136.8, 132.7, 128.4, 126.8, 124.5, 124.4,
120.6, 95.9 (d, 1JCF ¼ ꢂ205.3 Hz), 37.8 (d, 2JCF ¼ 23.1 Hz) ppm.
IR (KBr): n 3353, 3060, 1723, 1667, 1599, 1587, 1537, 1445, 1303,
1212, 1152, 1093, 1070, 921, 752, 717, 687 cmꢂ1. HRMS (ESI
positive): m/z calcd for C16H13FNO2 [M + H]+ 270.09248, found:
270.09247.
2
ppm; 13C NMR (100 MHz, CDCl3): d 193.8 (d, JCF ¼ 18.4 Hz),
2
3
166.8 (d, JCF ¼ 27.2 Hz), 152.2 (d, JCF ¼ 3.8 Hz), 143.4, 131.6,
1
129.5, 126.8, 126.6, 94.3 (d, JCF ¼ ꢂ200.7 Hz), 62.7, 37.9 (d,
2JCF ¼ 24.2 Hz), 14.0 ppm. IR (KBr): n 2984, 1767, 1729, 1599,
1578, 1421, 1324, 1289, 1211, 1189, 1070, 924, 858, 838,
784 cmꢂ1. HRMS (ESI positive): m/z calcd for C12H11ClFO3 [M +
H]+ 257.03753, found: 257.03754.
N-Benzyl-2-uoro-2,3-dihydro-1-oxo-1H-indene-2-carbox-
amide (2n). The title compound 2n was obtained according to
the general procedure as white solid (53.9 mg, 95% yield). M.p.
107–110 ꢀC. HPLC (Daicel Chiralpak IB, n-hexane–2-propanol
Ethyl
5-bromo-2-uoro-2,3-dihydro-1-oxo-1H-indene-2-
carboxylate (2k). The title compound 2k was obtained according
to the general procedure as white solid (57.7 mg, 96% yield).
M.p. 80–83 ꢀC. HPLC (Daicel Chiralpak IB, n-hexane–2-propanol
90 : 10, ow rate 1.0 mL minꢂ1, detection at 254 nm): tmajor
¼
13.9 min, tminor ¼ 16.1 min, 73% ee. [a]2D8 +7.7 (c 2.62, CH2Cl2);
1H NMR (400 MHz, CDCl3): d 7.81 (d, J ¼ 7.6 Hz, 1H, ArH), 7.68
(t, J ¼ 7.4 Hz, 1H, ArH), 7.50 (d, J ¼ 7.6 Hz, 1H, ArH), 7.43 (t, J ¼
7.4 Hz, 1H, ArH), 7.38–7.28 (m, 5H, ArH), 6.92 (s, 1H, CONH),
4.53 (d, J ¼ 5.6 Hz, 2H, CH2), 3.99 (dd, J1 ¼ 17.4 Hz, J2 ¼ 12.2 Hz,
98 : 2, ow rate 1.0 mL minꢂ1, detection at 254 nm): tmajor
¼
12.6 min, tminor ¼ 14.2 min, 99% ee. [a]2D8 ꢂ75.6 (c 3.00, CH2Cl2);
1H NMR (400 MHz, CDCl3): d 7.71–7.69 (m, 2H, ArH), 7.62 (d, J ¼
8.4 Hz, 1H, ArH), 4.29 (q, J ¼ 7.2 Hz, 2H, CH2), 3.78 (dd, J1 ¼
18.0 Hz, J2 ¼ 11.2 Hz, 1H, CH2), 3.42 (dd, J1 ¼ 23.0 Hz, J2 ¼
17.8 Hz, 1H, CH2), 1.27 (t, J ¼ 7.2 Hz, 3H, CH3) ppm; 13C NMR
1H, CH2), 3.34 (dd, J1 ¼ 24.0 Hz, J2 ¼ 17.6 Hz, 1H, CH2) ppm; 13
C
2
NMR (100 MHz, CDCl3): d 196.5 (d, JCF ¼ 17.8 Hz), 166.8 (d,
3
2JCF ¼ 22.8 Hz), 151.8 (d, JCF ¼ 4.0 Hz), 137.1, 136.6, 133.2,
2
2
(100 MHz, CDCl3): d 194.0 (d, JCF ¼ 18.9 Hz), 166.8 (d, JCF
¼
1
3
129.7, 129.4, 128.7, 128.3, 127.6, 126.5, 125.4, 96.7 (d, JCF
¼
28.1 Hz), 152.2 (d, JCF ¼ 3.4 Hz), 132.3, 132.0, 129.9, 126.6,
109.7, 94.2 (d, 1JCF ¼ ꢂ200.9 Hz), 62.7, 37.8 (d, 2JCF ¼ 24.3 Hz),
14.0 ppm. IR (KBr): n 3456, 2925, 2854, 1766, 1731, 1595, 1465,
1417, 1370, 1262, 1210, 1058, 923, 857, 796 cmꢂ1. HRMS (ESI
positive): m/z calcd for C12H11BrFO3 [M + H]+ 300.98701, found:
300.98729.
ꢂ201.9 Hz), 43.4, 37.4 (d, 2JCF ¼ 22.6 Hz) ppm. IR (KBr): n 3333,
3065, 3032, 2932, 1730, 1667, 1607, 1588, 1534, 1467, 1454,
1427, 1301, 1216, 1197, 1082, 917, 749, 733, 698 cmꢂ1. HRMS
(ESI positive): m/z calcd for C17H15FNO2 [M + H]+ 284.10813,
found: 284.10830.
N-Butyl-2-uoro-2,3-dihydro-1-oxo-1H-indene-2-carboxamide
(2l). The title compound 2l was obtained according to the
general procedure as white solid (50.0 mg, 100% yield). M.p. 85–
88 ꢀC. HPLC (Daicel Chiralpak IB, n-hexane–2-propanol 90 : 10,
Acknowledgements
We are grateful for nancial support from the National Natural
Science Foundation of China (Grant no. 20772006, 21072020),
2066 | RSC Adv., 2014, 4, 2061–2067
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the Science and Technology Innovation Program of Beijing
Institute of Technology (Grant no. 2011CX01008).
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