Subscriber access provided by Queen Mary, University of London
Letter
Highly Efficient Asymmetric Synthesis of Chiral #-Alkenyl Butenolides Catalyzed by Chiral N,N#-Dioxide–Scandium(III) Complexes Jie Ji, Lili Lin, Qiong Tang, Tengfei Kang, Xiaohua Liu, and Xiaoming Feng ACS Catal., Just Accepted Manuscript • DOI: 10.1021/acscatal.7b00590 • Publication Date (Web): 17 Apr 2017 Downloaded from http://pubs.acs.org on April 17, 2017
Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a free service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are accessible to all readers and citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.
ACS Catalysis is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.
Page 1 of 6
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
ACS Catalysis
Highly Efficient Asymmetric Synthesis of Chiral γ-Alkenyl Butenolides Catalyzed by Chiral N,N′-Dioxide–Scandium(III) Complexes Jie Ji, Lili Lin, Qiong Tang, Tengfei Kang, Xiaohua Liu and Xiaoming Feng*. Key Laboratory of Green Chemistry & Technology, Ministry of Education, College of Chemistry, Sichuan University, Chengdu 610064, P. R. China. ABSTRACT: The asymmetric synthesis of γ-alkenyl butenolides was accomplished by conjugated addition of butenolides to alkynones. Both terminal alkynones and non-terminal alkynones were applicable to the N,N′-dioxide–scandium(III) catalytic system. The corresponding products were obtained in good to excellent yields (up to 99%) with high E/Z ratios and high enantioselectivities (up to 98% ee). The novel methods of building both γ-alkenyl butenolides and continuing epoxidation products facilitated constructing core structure of biologically active natural products and synthetic intermediates. Additionally, one-pot Michael addition/epoxidation performed well with our catalytic system.
KEYWORDS. alkynones, α-angelica lactone, γ-alkenyl butenolides, N,N′-dioxides, scandium.
Chiral γ-alkenyl butenolides and their derivatives are widespread in bioactive natural products and are also valuable synthetic intermediates (Scheme 1a).1 When synthesizing such moieties, stoichiometric quantities of chiral reagents were usually applied.2 To our best knowledge, catalytic asymmetric direct synthesis of γ-alkenyl butenolides have not been well studied to date. Moreover, the reports of γ-alkenyl substituted butyrolactones are also scarce. The only example of such lactone was described by Toste et al using a π-acid gold(I) complex.3 Other approaches to chiral spirolactones4 and γ-alkenylγ-lactone products5 were executed by chiral iodine(III) species and asymmetric allylic C–H activation respectively. The limited examples inspired us to construct the privileged butenolide framework. The catalytic asymmetric reactions of furanone intermediates6-12 are efficient methods to synthesize chiral products with butenolide motifs. Among the furanone intermediates, 2silyoxyfurans6 and β,γ-butenolides7-12 are most commonly used. The latter were brought to attention due to its facile and atom-economic properties. The β,γ-butenolides have been widely applied in asymmetric reactions such as MBH reactions,8 Mannich reactions,9 Michael reactions2b,10 and annulation reactions.11 However, the catalytic asymmetric conjugated addition of β,γ-butenolides to alkynes13,14, which is a straightforward and atom-economic way to acquire γ-alkenyl butenolides, has not yet been reported (Scheme 1b). The reasons of such lack of reports might be due to the following challenges: 1) A suitable substrate activation is needed because the sphybridized alkynes have lower activity compared to the corresponding sp2-hybridized alkenes. 2) The intermediate furanone species have multiple reactive sites.15,16 3) A subsequent addition to the newly formed C–C double bond might occur.
Scheme 1. a) Selected examples of butenolides in natural products or in natural product synthesis and b) designed constructing pathway to γ-alkenyl butenolide. Considering the potential challenges above, we first mixed (E)-1-phenylbut-2-en-1-one with α-angelica lactone to probe whether a subsequent addition to designed product would occur. In the presence of N,N′-dioxide/Sc(III) complex,17 we pleasantly found only trace amount of the Michael product was obtained after 24 h (see Supporting Information for de-
ACS Paragon Plus Environment
ACS Catalysis
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
tails). This indicated the feasibility of our catalyst from the perspective of stability of the product, a potential Michael acceptor (Scheme 1b). Then, 1-phenylprop-2-yn-1-one 1a with commercial available α-angelica lactone 2a were selected as the model substrates to optimize the reaction conditions (Table 1). Various metal salts were examined by complexing with L-ramipril-derived LRaPr2 in EtOAc at 30 oC for 24 h. The Sc(OTf)3 complex gave high 95/5 E/Z ratio and 94% ee yet the yield was moderate (Table1, entry 1). Meanwhile, the complexes with other metal salts such as Y(OTf)3 and Fe(OTf)3 were also investigated with no further improvement (entries 2 and 3). When the reaction was performed in acetonitrile, the yield increased dramatically to 95% and the E/Z ratio increased to >99/1 (entry 4). Subsequent exploration of ligands suggested that both the backbones and the amine units have significant impacts on the reaction. L-Ramipril-derived ligand L-RaPr2 was superior to L-pipecolic acid-derived L-PiPr2 and L-proline-derived LPrPr2 (entry 4 vs. entries 5 and 6). As for amine units, the steric hindrance in ortho- and para-position of aryl group was found crucial for the reaction. With a smaller ethyl group on ortho-positions, L-RaEt2 decreased the enantioselectivity to 81% ee (entry 7), while L-RaPh gave only trace amount of the product (entry 8). Notably, when the L-RaPr3 was utilized, the reaction proceeded sluggishly. It was speculated that the steric group on para-position failed to facilitate the coordination with substrates (entry 9). All results above suggested that Table 1. Reaction optimizationa
Page 2 of 6
the L-RaPr2/Sc(III) complex provided a better chiral environment (see SI for plausible mechanism). Thus, the optimal conditions for the Michael reaction was established as 5 mol % L-RaPr2/Sc(OTf)3 complex in acetonitrile at 30 oC (entry 4). Under the optimized reaction conditions, a wide range of alkynones 1 and γ-substituted butenolides 2 were evaluated (Table 2). When R1 on alkynones 1 varied, substrates with either electron-donating or electron-withdrawing groups transformed into the corresponding products smoothly (entries 2– 10). Generally, the substrates with an electron-withdrawing group exhibited higher reactivity and enantioselectivity than those with electron-donating groups (entries 2–6 vs. 7–10). The reaction also successfully took place with fused-ring, Table 2. Scope of terminal alkynonesa
entry
R1
2
yield (%)b
E/Z ratioc
ee (%)d
1
Ph (1a)
2a
95 (3a)
>19/1
93
2
2-MeC6H4 (1b)
2a
53 (3b)
13.4/1
98
3
3-MeC6H4 (1c)
2a
76 (3c)
>19/1
80
4
4-MeC6H4 (1d)
2a
74 (3d)
>19/1
93
5
4-MeOC6H4 (1e)
2a
79 (3e)
>19/1
95
2a
70 (3f)
6.5/1
91 (S)e
6 (1f) 7
4-FC6H4 (1g)
2a
98 (3g)
13.3/1
97
8
4-ClC6H4 (1h)
2a
92 (3h)
14.9/1
96
9
4-BrC6H4 (1i)
2a
92 (3i)
13.5/1
97
10
3,4-Cl2C6H3 (1j)
2a
75 (3j)
5.8/1
92
11
2-naphthyl (1k)
2a
97 (3k)
>19/1
90
12
3-furyl (1l)
2a
90 (3l)
>19/1
96
13 f
Me (1m)
2a
72 (3m)
>19/1
95
14
PhCH2CH2 (1n)
2a
54 (3n)
>19/1
97
entry
metal salt
Ligand
solvent
yield (%)b
E/Z ratioc
ee (%)d
15
EtO
2a
N. R.
--
--
1
Sc(OTf)3
L-RaPr2
EtOAc
55
95/5
94
16
2a
N. R.
--
--
2
Y(OTf)3
L-RaPr2
EtOAc
24
76/24
55
3
Fe(OTf)3
L-RaPr2
EtOAc
Trace
--
--
17
Ph (1a)
2b
83 (3p)
>19/1
93
4
Sc(OTf)3
L-RaPr2
CH3CN
95
>99/1
93
18
Ph (1a)
2c
78 (3q)
>19/1
93
5
Sc(OTf)3
L-PiPr2
CH3CN
90
99/1
91
19
Ph (1a)
2d
87 (3r)
11.7/1
94
6
Sc(OTf)3
L-PrPr2
CH3CN
76
98/2
89
20
Ph (1a)
2e
93 (3s)
4.5/1
92/86
7
Sc(OTf)3
L-RaEt2
CH3CN
93
>99/1
81
21
Ph (1a)
2f
90 (3t)
5.0/1
94/89
8
Sc(OTf)3
L-RaPh
CH3CN
Trace
--
--
9
Sc(OTf)3
L-RaPr3
CH3CN
68
99/1
87
a Unless otherwise noted, the reactions were performed with 1a (0.10 mmol), 2a (0.15 mmol), metal (5 mol %), ligand (5 mol %) in solvent (0.5 mL) at 30 oC for 24 h. b Yield of isolated product. c Determined by HPLC analysis. d Determined by chiral HPLC for the major diastereoisomer.
a Unless otherwise noted, the reactions were performed with 1 (0.10 mmol) and 2 (1.5 equiv.) at 30 oC for 24 h. b Yield of isolated product. c Determined by NMR analysis. d Determined by chiral HPLC for the major diastereoisomer. e The absolute configuration was established by X-ray crystal diffraction analysis. f The reaction was performed with 1m (0.15 mmol) and 2a (0.10 mmol).
ACS Paragon Plus Environment
Page 3 of 6
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
ACS Catalysis
Scheme 2. Non-terminal alkynones investigation. heteroaryl, or even alkyl substituted alkynones (entries 11–14). When the acyl group on terminal alkynone was replaced by ester group or amide group, however, the catalyst system was inefficient and no reaction occurred (entries 15 and 16). Besides α-angelica lactone, various butenolides 2 were proved to be acceptable substrates (entries 17–21). For alkyl substrates 2b-2d, the results maintained, whereas aryl substrates 2e and 2f afforded lower E/Z ratios. Additionally, the absolute structure of the product 3f was determined to be S by X-ray crystal diffraction analysis.18 After the success in terminal alkynones, non-terminal alkynones were examined next (Scheme 2).19 There are only limited reports on this type of reaction. Two main challenges Table 3. Scope of β-ester substituted alkynonesa
entry
R1
2
yield (%)b
E/Z ratioc
ee (%)d
1
Ph (4b)
2a
93 (5b)
1/12.5
90
2
4-MeC6H4 (4d)
2a
98 (5d)
1/15.0
92
3
4-MeOC6H4 (4e)
2a
92 (5e)
1/14.0
92
2a
92 (5f)
1/10.7
89
4
hindering the process are: 1) a larger steric effect; 2) the difficulty on controlling the olefin geometry of allenic enolate intermediate.14e The preliminary attempt showed that the substrates with electron donating methyl or trimethylsilyl group were not feasible. By introducing electron withdrawing group, target products were obtained under previously optimized reaction conditions albeit with lower reactivity. By varying the ligands, the addition presented much higher reactivity with LPiPr2 with minor erosion of the Z-selectivity. Under newly optimized conditions, ester substituted 5a, 5b and 5c presented better results. In the meantime, the ee value increased as the ester group on β-ester substituted alkynones 4 enlarged, although with reduced reactivity. Additionally, diethyl acetylenedicarboxylate showed no reactivity in our catalytic system. The scope of β-ester substituted alkynones were assessed and showed an excellent scalability in this reaction (Table 3).
Scheme 3. New methodology for core structure of bioactive OH-3984. To further extend the utility of this methodology, 1o was applied as substrate in the Michael addition to construct chiral C4 position of the bioactive OH-3984 (Scheme 3). Under the optimized catalytic system, the targeted (+)-3o was obtained in 75% yield, >19/1 E/Z ratio and 98% ee. Aimed at achieving the other enantiomers of 3o, ent-L-PiPr2 was applied, and (-)3o was observed with corresponding results. For the purpose of constructing the core structure of the key synthetic intermediate of Milbemycin α1, epoxidation of the Table 4. Epoxidation of the Michael productsa
(4f) 5
4-FC6H4 (4g)
2a
94 (5g)
1/11.3
93
6
4-ClC6H4 (4h)
2a
69 (5h)
1/12.9
92
7
4-BrC6H4 (4i)
2a
88 (5i)
1/10.3
92
8
2-naphthyl (4j)
2a
94 (5j)
1/4.4
49/85
9
3-thienyl (4k)
2a
92 (5k)
1/6.8
92
10
c-pentyl (4l)
2a
75 (5l)
99 (4R, 5S, 6S)f
3
3a (93)
ent-LPiPr2/Sc(OTf)3
97 (6a′)
1/9.9
97
4
3l (96)
ent-LPiPr2/Sc(OTf)3
92 (6b′)
1/11.1
>99
a Unless otherwise noted, the reactions were performed with 3 (0.10 mmol) and 30% H2O2 (3.0 equiv.) at 35 oC for 12 h. b Yield of isolated product. c Determined by NMR analysis. d Determined by chiral HPLC for the major diastereoisomer. e The reaction was performed in Na2CO3 (20% aq., 0.5 mL) and acetone (1.5 mL). f The absolute configuration was established by X-ray crystal diffraction analysis.
ACS Paragon Plus Environment
ACS Catalysis
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
product 3 by using H2O2 was investigated (Table 4). When Na2CO3 was applied to promote the epoxidation of 3a (93% ee), only moderate yield and 1:2.8 dr were given with the ee value maintained (entry 1), indicating the original stereo center in 3 affected the selectivity of the epoxidation reaction. In order to increase both yield and diastereoselectivity of the product, chiral catalyst was employed. Remarkably, the LPiPr2/Sc(OTf)3 complex, which is the optimized catalyst in the conjugated addition, served as a powerful catalyst for the epoxidation,20 achieving the product 6a with 93% yield, 13.7/1 dr and >99% ee (entry 2). It was also found that the newly formed chirality was not influenced by C4 stereo center in our catalytic system as ent-L-PiPr2/Sc(OTf)3 also gave out 6a with high selectivity (entry 2 vs. 3). Kinetic resolution of (±)3a illustrated that the formation rate of 6a′ was slightly higher than that of 6a (see SI). This mild oxidation conditions were suitable for heteroaryl substituted product 3l (entry 4). Since the same catalyst was efficient for both conjugated addition and epoxidation process, one-pot synthesis streamlined the reaction for the final product 6 (Scheme 4). After the Michael addition in acetonitrile, removal of solvent followed by addition of THF and H2O2 for further 12 h stirring gave out 6a with desired results. Furthermore, good results were obtained when the solvent in the epoxidation step remained same as the former step. Such one-pot strategy building three chiral centers in an easy access, expanded synthetic utility. In addition, X-ray crystal diffraction analysis characterized the absolute configurations of 6a and 6b were (4R, 5S, 6S).18
Scheme 4. One-pot examination. In conclusion, we have developed an efficient asymmetric Michael addition of β,γ-butenolides to alkynones using a N,N′dioxide–scandium(III) catalytic system. The corresponding γalkenyl butenolides were obtained in good to excellent results. This methodology offers a unique way to synthesize core structures of natural products and synthetic intermediates under mild conditions. Besides, a concise and efficient one-pot Michael addition/epoxidation synthesis is established and reveals bright development prospects.
ASSOCIATED CONTENT Supporting Information. The Supporting Information is available free of charge on the ACS Publications website. Experimental procedures, full spectroscopic data for all new compounds, and copies of 1H, 13C NMR, and HPLC spectra (PDF) X-ray crystallographic data for 3f (CIF) X-ray crystallographic data for 6a(CIF) X-ray crystallographic data for 6b(CIF)
Page 4 of 6
AUTHOR INFORMATION Corresponding Author *E-mail:
[email protected].
ORCID Jie Ji: (0000-0002-6697-5770) Lili Lin: (0000-0001-8723-6793) Qiong Tang: (0000-0002-1545-0827) Tengfei Kang: (0000-0002-4616-5578) Xiaohua Liu: (0000-0001-9555-0555) Xiaoming Feng: (0000-0003-4507-0478)
Notes The authors declare no competing financial interest.
ACKNOWLEDGMENT We appreciate the National Natural Science Foundation of China (No. 21290182) for financial support.
REFERENCES (1) For selected examples, see: (a) Komiyama, K.; Takamatsu, S.; Takahashi, Y.; Shinose, M.; Hayashi, M.; Tanaka, H.; Iwai, Y.; Omura, S. J. Antibiot. 1993, 46, 1520−1525. (b) Komiyama, K.; Takamatsu, S.; Takahashi, Y.; Shinose, M.; Hayashi, M.; Tanaka, H.; Iwai, Y.; Omura, S. J. Antibiot. 1993, 46, 1526−1529. (c) Zhang, J.; Tang, X.; Li, J.; Li, P.; de Voogd, N. J.; Ni, X.; Jin, X.; Yao, X.; Li, P.; Li, G. J. Nat. Prod. 2013, 76, 600−606. (d) Molander, G. A.; Kenny, C. J. Org. Chem. 1988, 53, 2134−2136. (2) For examples building γ-alkenyl substituted butenolides, see: (a) Takahashi, T.; Watanabe, H.; Kitahara, T. Tetrahedron Lett. 2003, 44, 9219−9222. (b) Manna, M. S.; Mukherjee, S. Chem. Sci. 2014, 5, 1627−1633. (c) Datta, R.; Dixon, R. J.; Ghosh, S. Tetrahedron Lett. 2016, 57, 29−31. (3) For the example building γ-alkenyl substituted lactones via πacid gold(I) complex, see: Hamilton, G. L.; Kang, E. J.; Mba, M.; Toste, F. D. Science 2007, 317, 496–499. (4) For selected examples building spirolactones via chiral iodine(III) species, see: (a) Dohi, T.; Maruyama, A.; Takenaga, N.; Senami, K.; Minamitsuji, Y.; Fujioka, H.; Caemmerer, S. B.; Kita, Y. Angew. Chem., Int. Ed. 2008, 47, 3787–3790. (b) Uyanik, M.; Yasui, T.; Ishihara, K. Angew. Chem., Int. Ed. 2010, 49, 2175–2177. (c) Dohi, T.; Takenaga, N.; Nakae, T.; Toyoda, Y.; Yamasaki, M.; Shiro, M.; Fujioka, H.; Maruyama, A.; Kita, Y. J. Am. Chem. Soc. 2013, 135, 4558–4566. (d) Murray, S. J.; Ibrahim, H. Chem. Commun. 2015, 51, 2376–2379. (5) For examples building γ-alkenyl substituted lactones via asymmetric allylic C–H activation, see: (a) Takenaka, K.; Akita, M.; Tanigaki, Y.; Takizawa, S.; Sasai, H. Org. Lett. 2011, 13, 3506–3509. (b) Lumbroso, A.; Abermil, N.; Breit, B. Chem. Sci. 2012, 3, 789–793. (c) Suzuki, Y.; Seki T.; Tanaka, S.; Kitamura, M. J. Am. Chem. Soc. 2015, 137, 9539−9542. (6) For selected reviews describing 2-silyoxyfurans, see: (a) Chabaud, L.; Jousseaume, T.; Retailleau, P.; Guillou, C. Eur. J. Org. Chem. 2010, 5471–5481. (b) Zhang, Q., Liu, X. H., Feng, X. M. Curr. Org. Chem. 2013, 17, 764–785 (7) For selected reviews forming γ-butenolides, see: (a) Yan, L.; Wu, X.; Liu, H.; Xie, L.; Jiang, Z. Mini-Rev. Med. Chem. 2013, 13, 845−853. (b) Uraguchi, D.; Ooi, T. Top. Curr. Chem. 2016, 372, 55– 84. (c) Roselló, M. S.; del Pozo, C.; Fustero S. Synthesis 2016, 48, 2553−2571. (d) Neumeyer, M.; Brückner, R. Eur. J. Org. Chem. 2016, 2016, 5060–5087. (8) The first report of MBH reaction with α-angelica lactone, see: Cui, H.-L.; Huang, J.-R.; Lei, J.; Wang, Z.-F.; Chen, S.; Wu, L.; Chen, Y.-C Org. Lett. 2010, 12, 720−723. (9) The first report of Mannich reaction with with α-angelica lactone, see: Zhou, L.; Lin, L. L.; Ji, J.; Xie, M. S.; Liu, X. H.; Feng, X. M. Org. Lett. 2011, 13, 3056−3059.
ACS Paragon Plus Environment
Page 5 of 6
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
ACS Catalysis
(10) For selected reports of Michael reaction with α-angelica lactone, see: (a) Quintard, A.; Lefranc, A.; Alexakis, A. Org. Lett. 2011, 13, 1540–1543. (b) Manna, M. S.; Mukherjee, S. Chem. - Eur. J. 2012, 18, 15277–15282. (c) Zhang, W.; Tan, D.; Lee, R.; Tong, G.; Chen, W.; Qi, B.; Huang, K.-W.; Tan, C.-H.; Jiang, Z. Angew. Chem., Int. Ed. 2012, 51, 10069−10073. (d) Manna, M. S.; Kumar, V.; Mukherjee, S. Chem. Commun. 2012, 48, 5193−5195. (e) Das, U.; Chen, Y.-R.; Tsai, Y.-L.; Lin, W. Chem. - Eur. J. 2013, 19, 7713–7717. (f) Ji, J.; Lin, L. L.; Zhou, L.; Zhang, Y. H.; Liu, Y. B.; Liu, X. H.; Feng, X. M. Adv. Synth. Catal. 2013, 355, 2764−2768. (g) Li, X.; Lu, M.; Dong, Y.; Wu, W.; Qian, Q.; Ye, J.; Dixon, D. J. Nat. Commun. 2014, 5, 4479. (h) Yin, L.; Takada, H.; Lin, S.; Kumagai, N.; Shibasaki, M. Angew. Chem., Int. Ed. 2014, 53, 5327−5331. (i) Sekikawa, T.; Kitaguchi, T.; Kitaura, H.; Minami, T.; Hatanaka, Y. Org. Lett. 2015, 17, 3026–3029. (j) Wang, Z.-H.; Wu, Z.-J.; Huang, X.-Q.; Yue, D.-F.; You, Y.; Xu, X.-Y.; Zhang, X.-M.; Yuan, W.-C. Chem. Commun. 2015, 51, 15835–15838. (k) Lagoutte, R.; Besnard, C.; Alexakis, A. Eur. J. Org. Chem. 2016, 4372−4381. (11) For the first report of annulation reaction with α-angelica lactone, see: Li, C.; Jiang, K.; Chen, Y.-C. Molecules 2015, 20, 13642−13658. (12) For the other reports with α-angelica lactone, see: (a) Wu, Y.; Singh, R. P.; Deng, L. J. Am. Chem. Soc. 2011, 133, 12458−12461. (b) Kumar, V.; Mukherjee, S. Chem. Commun. 2013, 49, 11203−11205. (13) For selected reviews of conjugate addition reactions, see: (a) Alonso, F.; Beletskaya, I. P.; Yus, M. Chem. Rev. 2004, 104, 3079– 3160. (b) Salvio, R.; Moliterno, M.; Bella, M. Asian J. Org. Chem. 2014, 3, 340–351. (c) Fraile, A.; Parra, A.; Tortosa, M.; Alemán J. Tetrahedron 2014, 70, 9145–9173. (14) For selected examples of asymmetric reactions with alkynes, see: (a) Filloux, C. M.; Lathrop, S. P.; Rovis, T. Proc. Natl. Acad. Sci. 2010, 107, 20666–20671. (b) Wang, Z.; Chen, Z. L.; Bai, S.; Li, W.; Liu, X. H.; Lin, L. L.; Feng, X. M. Angew. Chem., Int. Ed. 2012, 51, 2776–2779. (c) Wang, Z.; Zhang, Z. L.; Yao, Q.; Liu, X. H.; Cai, Y. F.; Lin, L. L.; Feng, X. M. Chem. - Eur. J. 2013, 19, 8591–8596. (d) Zhao, L.; Guo, B.; Huang, G.; Chen, J.; Cao, W.; Wu, X. ACS Catal. 2014, 4, 4420–4424. (e) Uraguchi, D.; Yamada, K.; Ooi, T. Angew. Chem., Int. Ed. 2015, 54, 9954 –9957. (f) Yang, D.; Wang, L.; Kai, M.; Li, D.; Yao, X.; Wang, R. Angew. Chem., Int. Ed. 2015, 54, 9523–9527. (g) Wang, L.; Yang, D.; Li, D.; Wang, P.; Wang, K.; Wang, J.; Jiang, X.; Wang, R. Chem. - Eur. J. 2016, 22, 8483–8487. (15) For a recent example showing the activity on α-position of αangelica lactone, see: Wu, B.; Yu, Z.; Gao, X.; Lan, Y.; Zhou, Y.-G. Angew. Chem., Int. Ed. 2017, 56, 4006–4010. (16) For examples about the α-position addition on trimethylsilyoxyfuran, see: (a) Mao, B.; Ji, Y.; Fañanás-Mastral, M.; Caroli, G.; Meetsma, A.; Feringa, B. L. Angew. Chem., Int. Ed. 2012, 51, 3168−3173. (b) Chen, W.; Hartwig, J. F. J. Am. Chem. Soc. 2012, 134, 15249−15252. (c) Woyciechowska, M.; Forcher, G.; Buda, S.; Mlynarski, J. Chem. Commun. 2012, 48, 11029–11031. (17) (a) Liu, X. H.; Lin, L. L.; Feng, X. M. Acc. Chem. Res. 2011, 44, 574–587. (b) Liu, X. H.; Lin, L. L.; Feng, X. M. Org. Chem. Front. 2014, 1, 298–302. (18) The X-ray crystal structures of 3f (CCDC 1047005, accessed Feb 3, 2015), 6a (CCDC 1510983, accessed Oct 21, 2016) and 6b (CCDC 1529290, accessed Jan 24, 2017) contain the supplementary crystallographic data for this paper. These data can be obtained free of charge from The Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_request/cif. (19) The reaction was performed with substituted alkynones (0.10 mmol), L-PiPr2/Sc(OTf)3 (1:1, 5 mol %) in CH3CN (0.2 M) and 2 (1.5 equiv.) at 30 oC. For more details see SI. (20) (a) Chu, Y. Y.; Liu, X. H.; Li, W.; Hu, X. L.; Lin, L. L.; Feng, X. M. Chem. Sci. 2012, 3, 1996. (b) Chu, Y. Y.; Hao, X. Y.; Lin, L. L.; Chen, W. L.; Li, W.; Tan, F.; Liu, X. H.; Feng, X. M. Adv. Synth. Catal. 2014, 356, 2214–2218.
ACS Paragon Plus Environment
ACS Catalysis
Page 6 of 6
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 ACS Paragon Plus Environment
6
