N, N ′-Dioxide/nickel(II)-catalyzed asymmetric Diels-Alder reaction of cyclopentadiene with 2,3-dioxopyrrolidines and 2-alkenoyl pyridines

Article abstract of DOI:10.1039/c6cc03346f

A chiral N,N′-dioxide/Ni(OTf)₂ complex-catalyzed asymmetric Diels-Alder reaction of cyclopentadiene with 2,3-dioxopyrrolidines and 2-alkenoyl pyridines has been achieved. The corresponding chiral bridged compounds were obtained in high yields with excellent dr and ee values (up to 97% yield, 95: 5 dr and 97% ee).

Full text of DOI:10.1039/c6cc03346f

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N,N -Dioxide/nickel(II)-catalyzed asymmetric
Diels–Alder reaction of cyclopentadiene with
Cite this:DOI: 10.1039/c6cc03346f
2
,3-dioxopyrrolidines and 2-alkenoyl pyridines†
Received 21st April 2016,
Accepted 31st May 2016
Yan Lu, Yuhang Zhou, Lili Lin,* Haifeng Zheng, Kai Fu, Xiaohua Liu and
Xiaoming Feng*
DOI: 10.1039/c6cc03346f
www.rsc.org/chemcomm
0
A
chiral N,N -dioxide/Ni(OTf)
2
complex-catalyzed asymmetric
Diels–Alder reaction of cyclopentadiene with 2,3-dioxopyrrolidines
and 2-alkenoyl pyridines has been achieved. The corresponding chiral
bridged compounds were obtained in high yields with excellent dr
and ee values (up to 97% yield, 95: 5 dr and 97% ee).
The asymmetric Diels–Alder (DA) reactions play an important
role in organic synthesis since they provide powerful C–C bond-
forming transformations to obtain enantiomerically enriched
1
cyclohexene substructures. Among them, the DA reaction of
cyclopentadiene is an effective method for the synthesis of
2
bridged compounds. For example, spiroindole melatonin
3
4
5
analogues, tetracyclic imine and gelsemine, are interesting
biologically active compounds. Chiral Lewis acid-promoted-
asymmetric DA reactions by activating bidentate dienophiles,
6
7
such as unsaturated a-ketoesters, acrylimides, and N-hydroxy-
8
acrylamides, have been well explored. Besides, dioxopyrrolidine
derivatives and 2-alkenoyl pyridine derivatives are interesting
synthons. The dioxopyrrolidines can participate in a reaction as
not only a monoene but also a 4p component (Scheme 1). In
9
2
014, Lin’s group developed a highly efficient aza-ene reaction
of heterocyclic ketene aminals (HKAs) with 2,3-dioxopyrrolidines
under catalyst-free conditions to synthesize imidazo[1,2-a]-pyrrolo-
1
0
Scheme 1 Reactions of 2,3-dioxopyrrolidines and 2-alkenoyl pyridines.
[
3,4-e]pyridine derivatives. Recently, Xu’s group reported an
asymmetric inverse electron demand [4+2] annulation between allene
ketones and 2,3-dioxopyrrolidines catalyzed by a cinchona alkaloid- catalysts were developed and good results were obtained for
1
1
11b
derived amine, where 2,3-dioxopyrrolidines acted as oxa-dienes. the limited substrate. In 1998, Engberts’s group
reported
However, the asymmetric DA reaction of cyclopentadiene with chiral amino acid–Cu(II) complex catalyzed DA reaction of 3-phenyl-
dioxopyrrolidines as dienophiles, to obtain chiral bridged spiro 1-(2-pyridyl)-2-propen-1-one with cyclopentadiene in water,
1
1f
compounds with four adjacent stereocenters, has not been reported. which only gave 74% ee. In 2007, Pedro’s group reported a
For the asymmetric DA reactions between 2-alkenoyl pyridines bis(oxazoline)–Cu(II) catalytic system, which was efficient for the
and cyclopentadiene, artificial metalloenzymes and DNA-based enantioselective DA reaction of cyclopentadiene with 2-alkenoyl
pyridine N-oxides but not for non-oxidizing 2-alkenoyl pyridines
(
only 19% ee, Scheme 1).
Key Laboratory of Green Chemistry & Technology, Ministry of Education,
College of Chemistry, Sichuan University, Chengdu 610064, People’s Republic of China.
E-mail: lililin@scu.edu.cn, xmfeng@scu.edu.cn; Fax: +86 28 85418249
0
C
2
-symmetric N,N -dioxides developed by our group possess
the properties of flexibility, and have been proved to be useful
ligands or organocatalysts. We assume that the flexible
crystallographic data in CIF or other electronic format see DOI: 10.1039/c6cc03346f N,N -dioxides/metal catalysts might realize the asymmetric
1
2
†
Electronic supplementary information (ESI) available. CCDC 1438596. For ESI and
0
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a
a
Table 1 Optimization of the reaction conditions
Table 2 Substrate scope of the asymmetric DA reaction of 1 and 2
1
b
c
d
Entry
R
Yield (%)
dr
ee (%)
1
2
3
4
5
6
7
8
9
Ph
3-FC
4-FC
3-ClC
4-ClC
3-BrC
4-BrC
4-F
3,4-Cl C H
2-MeC
4-MeC
4-MeOC
90 (3a)
91 (3b)
87 (3c)
91 (3d)
86 (3e)
92 (3f)
97 (3g)
89 (3h)
90 (3i)
80 (3j)
83 (3k)
85 (3l)
94 (3m)
85 (3n)
93 : 7
93 : 7
92 : 8
93 : 7
93 : 7
94 : 6
93 : 7
94 : 6
93 : 7
90 : 10
92 : 8
92 : 8
88 : 12
93 : 7
97 (1R,2R,3S,4S)
96 (1R,2R,3S,4S)
95 (1R,2R,3S,4S)
97 (1R,2R,3S,4S)
95 (1R,2R,3S,4S)
97 (1R,2R,3S,4S)
96 (1R,2R,3S,4S)
96 (1R,2R,3S,4S)
97 (1R,2R,3S,4S)
75 (1R,2R,3S,4S)
93 (1R,2R,3S,4S)
96 (1R,2R,3S,4S)
95 (1R,2R,3S,4S)
94 (1R,2R,3S,4S)
6
H
H
4
4
6
6
H
H
4
6
4
6
H
H
4
6
4
3
CC
6
H
4
b
c
c
Entry
Ligand
Metal
Yield (%)
dr
ee (%)
2
6
3
10
11
12
13
14
6
H
H
4
1
2
3
4
5
6
7
L-PrPr
L-PrPr
L-PrPr
L-PrPr
2
2
2
2
Cu(OTf)
Zn(OTf)
Mg(OTf)
Ni(OTf)
Ni(OTf)
Ni(OTf)
Ni(OTf)
Ni(OTf)
2
96
85
88
90
90
89
91
90
97 : 3
97 : 3
97 : 3
97 : 3
96 : 4
94 : 6
98 : 2
96 : 4 (93 : 7)
29
75
81
86
74
92
39
97
6
4
2
6
H
4
2
1-Naphthyl
2-Naphthyl
2
2
2
2
2
L-PiPr
L-RaPr
L-RaMe
L-RaPr
2
2
1
5
78 (3o)
82 : 18
92 (1R,2R,3R,4S)
2
d
e
8
2
a
Unless otherwise noted, the reactions were performed with
/Ni(OTf) (1 : 1, 10 mol%) in Cl CHCH
(1.0 mL) (1.0 mL) at 30 1C for 0.5–5 h. Isolated yield of 3. Determined by H NMR
1
a
Unless otherwise noted, the reactions were performed with 1a (0.1 mmol), 2 (100 mL) and L-RaPr
2
2
2
2
Cl
b
c
1
(
0.1 mmol), 2 (100 mL) and L/metal (1: 1, 10 mol%) in CH
at 30 1C for 2 h. Isolated yield of 3a. Determined by chiral HPLC
analysis. Cl CHCH Cl was used. Determined by H NMR analysis.
2 2
2
Cl
2
b
c
d
analysis. Determined by chiral HPLC analysis.
d
e
1
2,3-dioxopyrrolidine derivatives bearing different aromatic groups
DA reaction of cyclopentadiene with dioxopyrrolidines, and also reacted smoothly with cyclopentadiene 2, providing the corres-
with 2-alkenoyl pyridines. Herein, we report our efforts in develop- ponding bridged spiro products with four adjacent stereo-
0
ing an N,N -dioxide/Ni(OTf)
2
complex system that is efficient for centers in good to excellent yields with excellent diastereo- and
the asymmetric Diels–Alder reaction of cyclopentadiene with enantioselectivities. Generally, 2,3-dioxopyrrolidines with electron-
2,3-dioxopyrrolidines and 2-alkenoyl pyridines.
withdrawing groups on the phenyl ring achieved higher yields than
In the initial study, (E)-1-benzyl-4-benzylidenepyrrolidine- those with electron-donating substituents (Table 2, entries 1–9 vs.
,3-dione 1a and cyclopentadiene 2 were chosen as model sub- entries 10–12). The ortho-substituted substrate 1j yielded product
2
strates to optimize the reaction conditions. Several metal salts 3j in a much lower ee value (75% ee; Table 2, entry 10), which
0
coordinating to the L-proline derived chiral N,N -dioxide L-PrPr
might be caused by the steric hindrance of the ortho-substituents
2
were tested in DCM at 30 1C (Table 1, entries 1–4). After 2 h, with the catalyst. Furthermore, naphthyl-substituted substrates
Cu(OTf) showed good reactivity, but the enantioselectivity was were tolerated, and the corresponding products 3m–n were
poor (29% ee, Table 1, entry 1). Zn(OTf) and Mg(OTf) gave afforded in excellent results (94 and 85% yield, 88:12 and
much higher ee albeit with slightly lower yields (85 and 88% yield, 93:7 dr, 95 and 94% ee, respectively, Table 2, entries 13 and 14).
7:3 dr, 75 and 81% ee, respectively; Table 1, entries 2 and 3). To Remarkably, heteroaromatic substrate 1o derived from thiophene-
our delight, Ni(OTf) was more effective in promoting the reaction, 3-carbaldehyde could also be converted to the desired product in
2
2
2
9
2
and the desired product 3a was obtained in 90% yield, 97:3 dr, and 78% yield, 82:18 dr value and 92% ee value (Table 2, entry 15). The
0
8
6% ee (Table 1, entry 4). Exploring different chiral N,N -dioxides absolute configuration of 3d was determined to be (1R,2R,3S,4S) by
13
revealed that L-RaPr
ee to 92% (Table 1, entry 6) while L-PiPr
acid decreased the ee to 74% (Table 1, entry 5). Decreasing the
2
derived from L-ramipril could increase the using single-crystal X-ray diffraction analysis, the others were
derived from L-piperidine confirmed in comparison with the Cotton effect in the CD spectra.
Encouraged by these results obtained from 2,3-dioxopyrrolidine
2
steric hindrance of the amide substituents resulted in a very poor derivatives, we attempted to broaden the reaction scope to
ee though the yield and dr were still high (91% yield, 98:2 dr, 2-alkenoyl pyridines. To our delight, in the presence of the
39% ee; Table 1, entry 7). Further exploration of solvents revealed optimal L-RaPr
2 2
/Ni(OTf) complex, 2,3-dioxopyrrolidines 4a–4h
that Cl CHCH Cl could substantially increase the enantioselectivity, bearing either an electron-withdrawing or an electron-donating
2
2
and the desired product 3a was isolated in 90% yield, 96:4 dr and substituent on the phenyl ring converted to the corresponding
7% ee (Table 1, entry 8). chiral bridged products in high yields and stereoselectivities
9
With the optimized reaction conditions established, we next (74–90% yields, 90:10–95:5 dr, 88–96% ee; Table 3, entries 1–8).
investigated the substrate scope of the reaction by varying the Remarkably, heteroaromatic substrates were also suitable.
2,3-dioxopyrrolidine derivatives 1. As summarized in Table 2, Furyl substituted 4i and 4j afforded the desired products 5i–j
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a
Table 3 Substrate scope of the asymmetric DA reaction of 2 and 4
2
b
c
d
Entry
R
Yield (%)
dr
ee (%)
1
2
3
4
5
6
7
8
9
1
1
1
1
Ph
4-FC H
6 4
4-ClC H
6 4
2-BrC
3-BrC
4-BrC
89 (5a)
86 (5b)
90 (5c)
82 (5d)
74 (5e)
82 (5f)
84 (5g)
77 (5h)
77 (5i)
66 (5j)
83 (5k)
75 (5l)
79 (5m)
93 : 7
93 : 7
92 : 8
92 : 8
90 : 10
91 : 9
94 : 6
95 : 5
94 : 6
94 : 6
94 : 6
95 : 5
77 : 23
96 (1S,2R,3R,4R)
95 (1S,2R,3R,4R)
88 (1S,2R,3R,4R)
90 (1S,2R,3R,4R)
88 (1S,2R,3R,4R)
93 (1S,2R,3R,4R)
94 (1S,2R,3R,4R)
96 (1S,2R,3R,4R)
94 (1S,2R,3R,4R)
96 (1S,2R,3R,4R)
94 (1S,2R,3R,4R)
94 (1S,2R,3R,4R)
96 (1S,2R,3R,4R)
6
6
6
H
H
H
4
4
4
Scheme 2 (a) Gram-scale version of the reaction; (b) conversion of 3d to 6.
4-MeC
6
H
4
H
4-MeOC
2-Furyl
3-Furyl
2-Thienyl
3-Thienyl
c-Hexyl
6
4
0
1
2
3
a
Unless otherwise noted, the reactions were performed with
4
(
0.1 mmol), 2 (100 mL) and L-RaPr
2
/Ni(OTf) (1 : 1, 10 mol%) in Cl CHCH Cl
2
2
2
b
c
1
(
1.0 mL) at 30 1C for 11–24 h. Isolated yield of 5. Determined by H NMR
analysis. Determined by chiral HPLC analysis.
d
in 66–77% yields, 94:6 dr, 94–96% ee (Table 3, entries 9 and 10).
While, thienyl substituted 4k–l generated the products in
75–83% yields, 94:6–95:5 dr and 94% ee (Table 3, entries 11
and 12). Additionally, cyclohexyl substituted 4m also proceed
smoothly, giving the corresponding product in 79% yield,
77:23 dr, and 96% ee. The absolute configuration of 5a was
assigned to be (1S,2R,3R,4R) by comparing the characterization
14
data with the literature. The configuration of the other products
was determined also to be (1S,2R,3R,4R) by a comparison of their
CD spectra with that of 5a.
To show the synthetic potential of the catalytic system, a gram-
scale synthesis of 3d was carried out. As shown in Scheme 2, in
Scheme 3 Control experiments.
2 2
the presence of 10 mol% L-RaPr /Ni(OTf) complex, 1d (3.5 mmol)
and 2 (3.5 mL) transformed smoothly to 3d in 99% yield (1.313 g) product 5p was also obtained in very good stereoselectivity
with 495:5 dr and 95% ee (Scheme 2a). Meanwhile, product 3d (88:12 dr and 89% ee).
could be easily transformed to 6 in good yield (68%) without loss
To further explore the mechanism of the catalytic reaction,
of stereoselectivity by simple reduction of the carbon–carbon the catalytic composition and coordination between the sub-
1
4
double bond with 10% Pd/C in ethyl acetate (Scheme 2b).
strate and the catalyst were investigated by using ESI-HRMS.
It is well-known that dioxopyrrolidine 1 was readily coordi- The spectrum of a mixture of ligand L-RaPr , Ni(OTf) and 1a
2
2
nated to the catalysts by their carbonyl groups in a bidentate in a 1:1:1 ratio in Cl CHCH Cl at 30 1C displayed an ion at
2
2
6
,12
2+
ꢀ +
manner.
2
Then, what about the 2-alkenoyl pyridines 4? To m/z 907.3792 (m/z calcd for [L-RaPr + Ni + OTf ] : 907.3796),
gain insight into the role of the pyridine group, control experi- this result suggested that the ligand coordinated with the metal in a
2+
ꢀ
+
ments were performed. As shown in Scheme 3, chalcone 4n and 1:1 ratio. A characteristic signal of [L-RaPr
-alkenoyl pyridine 4o, whose aromatic rings have no chance to m/z 1184.4904 (m/z calcd 1184.4899) was also observed, which
coordinate with the central metal, enabled the reaction to suggested that the L-RaPr /Ni(OTf) complex coordinated with 1a
2
+ Ni + OTf + 1a] at
4
2
2
proceed sluggishly and only a trace amount of products was in a 1:1 ratio. Meanwhile, the spectrum of a mixture of ligand
detected after 12 h, suggesting that the coordination of the L-RaPr , Ni(OTf) and 4a displayed ions at m/z 907.3788 (m/z calcd for
2
2
2+
ꢀ +
nitrogen atom of pyridine to the metal center is crucial for the [L-RaPr + Ni + OTf ] : 907.3796) and m/z 1116.4698 (m/z calcd
2
2+
ꢀ
+
reaction. Furthermore, 2-alkenoyl pyridine N-oxide 4p, which for [L-RaPr
could also coordinate to the central metal ion in a bidentate L-RaPr /Ni(OTf)
fashion, was also synthesized and applied in the reaction under the Besides, operand IR experiments were also provided, which sug-
2
+ Ni + OTf + 4a] : 1116.4636), suggesting that the
2
2
complex also coordinated with 4a in a 1 : 1 ratio.
14
optimized reaction conditions. To our delight, the corresponding gested that the reactions proceeded through a concerted pathway.
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Scheme 4 Proposed stereochemical model.
6
7
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2
015, 80, 10992.
8
9
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2
oxygens of L-RaPr coordinated to Ni(II) to form a six membered
chelating ring. Then, 2,3-dioxopyrrolidine 1d coordinates to the
chiral catalyst L-RaPr /Ni(OTf) with it’s two carbonyl groups
1
1
2
2
through a bidentate fashion, while 4a coordinates with the
carbonyl group and the nitrogen atom of pyridine, forming a
rigid octahedral complex. The cyclopentadiene prefers to attack
the dienophiles from the Re-face since the Si-face is shielded by
the amide moiety, leading to the formation of product 3d with the
(1R,2R,3S,4S)-configuration (Scheme 4, TS1), and product 5a with
the (1S,2R,3R,4R)-configuration (Scheme 4, TS2).
4
9, 5151; (h) A. Livieri, M. Boiocchi, G. Desimoni and G. Faita,
0
In summary, we have developed an efficient chiral N,N -dioxide/
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2
of cyclopentadiene with 2,3-dioxopyrrolidines and 2-alkenoyl
pyridines. Both reactions proceeded in high activities and high
levels of stereocontrol. The corresponding chiral bridged com-
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1
97% yield, 95 : 5 dr and 97% ee. Furthermore, possible transition
(
7
c) K. Zheng, L. L. Lin and X. M. Feng, Acta Chim. Sin., 2012,
0, 1785; (d) M. S. Xie, X. X. Wu, G. Wang, L. L. Lin and
models were proposed to explain the stereochemistry. Further
applications of the catalysts are underway in our laboratory.
We appreciate the National Natural Science Foundation of China
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Y. B. Liu, Y. L. Zhang, X. H. Liu, L. L. Lin and X. M. Feng,
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(No. 21290182, 21321061, and 21572136) for financial support.
Notes and references
1
For selected reviews on Diels–Alder reaction, see: (a) D. A. Evans and
J. S. Johnson, in Comprehensive Asymmetric Catalysis, ed. E. N.
Jacobsen, A. Pfaltz and H. Yamamoto, Springer, New York, 1999,
vol. 3, pp. 1177; (b) K. C. Nicolaou, S. A. Snyder, T. Montagnon and
G. Vassilikogiannakis, Angew. Chem., Int. Ed., 2002, 41, 1668; 13 CCDC 1438596 (3d).
c) A. G. Doyle and E. N. Jacobsen, Chem. Rev., 2007, 107, 5713; 14 See the ESI† for details.
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Chem. Commun.
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