Letter Cite This: Org. Lett. XXXX, XXX, XXX−XXX
pubs.acs.org/OrgLett
K2S2O8‑Mediated Selective Trifluoromethylacylation and Trifluoromethylarylation of Alkenes under Transition-Metal-Free Conditions: Synthetic Scope and Mechanistic Studies Lin Tang,*,†,‡ Zhen Yang,† Xueping Chang,*,† Jingchao Jiao,† Xiantao Ma,† Weihao Rao,† Qiuju Zhou,† and Lingyun Zheng† †
College of Chemistry and Chemical Engineering, Xinyang Normal University, Xinyang, Henan 464000, China Henan Province Key Laboratory of Utilization of Non-metallic Mineral in the Sourth of Henan, Xinyang, Henan 464000, China
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‡
S Supporting Information *
ABSTRACT: A practical and efficient method for selective intramolecular radical trifluoromethylacylation and -arylation of alkenes with inexpensive CF3SO2Na and K2S2O8 in aqueous media has been developed, respectively, affording the highly chemoselective synthesis of CF3-functionalized chroman-4ones and chromanes in satisfactory yields. Control experiments and DFT calculations indicate that the CF3SO2Na/K2S2O8 system is capable of trifluoromethylating the substrate of alkenes without a transition metal catalyst and the oxidation of CF3SO2Na to ·CF3 by K2S2O8 is involved in the ratedetermining step.
F
difunctionalization of alkenes mediated by trifluoromethyl sources is regarded as one of the most attractive synthetic strategies, because it not only introduces the desired C(sp3)− CF3 bond but also generates a second vicinal functionality in a step-economical manner. Hence, it is unsurprising that this promising difunctionalization approach, including trifluoromethylarylation,6 trifluoromethylacylation,7 aminotrifluoromethylation,8 oxytrifluoromethylation,2e,9 halotrifluoromethylation,10 and other alternative trifluoromethylations,11 has been widely reported for the synthesis of CF3-containing target molecules (Scheme 1b). Despite the many remarkable advantages achieved in these trifluoromethyl radical-mediated difunctionalization reactions, different kinds of transition metals and expensive trifluoromethyl sources are usually involved. In 2014, Lei’s group reported the transition-metal-free oxytrifluoromethylation of activated alkenes with Langlois reagent under the catalysis of K2S2O8.12 Very recently, several examples of trifluoromethylarylation,13 trifluoromethylalkenylation,14 trifluoromethylalkynylation,15 halotrifluoromethylation,16 thiotrifluoromethylation,17 and oxytrifluoromethylation18 of alkenes have been successfully developed under transition-metal-free conditions. Unfortunately, transition-metal-free trifluoromethylacylation of alkenes with inexpensive CF3 reagents, such as CF3SO2Na, has not been exhibited up to now. Chroman-4-one scaffolds, which are considered to be an important class of oxygen-containing structural motifs, are
luorine- and particularly CF3-containing organic compounds are versatile chemicals due to their widespread emergence in the fields of pharmaceuticals, agrochemicals, and materials science.1 In this context, the pursuit of practical protocols to construct a C−CF3 bond attracts considerable attention. To this end, significant progress in (visible-lightinduced) transition-metal-catalyzed direct trifluoromethyl functionalization of alkenes has been made for C(sp2)−CF3 formation by use of various trifluoromethyl sources such as Togni’s reagent,2 Umemoto’s reagent,3 Langlois reagent,4 and trifluoroalkyl halide5 in the past decade (Scheme 1a). In particular, (visible-light-induced) transition-metal-catalyzed Scheme 1. Examples of Alkene Trifluoromethylation
Received: September 6, 2018
© XXXX American Chemical Society
A
DOI: 10.1021/acs.orglett.8b02846 Org. Lett. XXXX, XXX, XXX−XXX
Letter
Organic Letters
Table 1. Optimization of the the Reaction Conditionsa
widely present in naturally occurring compounds and active molecules and represent unique biological and pharmaceutical activities.19 Therefore, existing approaches for their synthesis, usually involving Michael-type addition of chalcones or alkynones,20 intramolecular dehydrated condensation from 1,3-dicarbonyl compounds,21 transition-metal catalyzed tandem cyclization,22 and other alternative transformations,23 have been extensively developed. For the purpose of combining the properties of chroman-4-ones and trifluoromethylated molecules, CF3-containing chroman-4-ones and chromanes are extremely valuable. Encouraged by our work in green synthesis,24 we herein wish to demonstrate a novel and convenient access to CF3-containing chroman-4-ones in the absence of a transition metal by taking advantage of K2S2O8-mediated intramolecular trifluoromethylacylation of alkenes with CF 3 SO 2 Na. After determining the trifluoromethylacylation mechanism, selective trifluoromethylarylation can be also achieved to afford the desired chromanes by altering the substrates (Scheme 1c). Cu(OAc)2/K2S2O8 could serve as an efficient catalytic system for P(O)H compound oxidation via a single electrontransfer process in our recent study.25 Therefore, we deduced that the Cu(OAc)2/K2S2O8 system should be applied in both the aldehyde group and CF3SO2Na oxidation to afford the desired acyl and trifluoromethyl. On account of our hypothesis, we designed 2-(allyloxy)benzaldehyde (1a) as the model starting material to research the reaction conditions (Table 1). As expected, intramolecular trifluoromethylacylation of alkenyl in 1a could be readily achieved, yielding the desired product 3(2,2,2-trifluoroethyl)chroman-4-one (2a) in 38% yield as shown in entry 1. However, only a trace amount of 3a was detected through trifluoromethylarylation. The following experiments were carried out to initially investigate the effect of different transition metal catalysts (entries 2−6). CuBr2, CuCl2, CuBr, AgNO3, and FeCl2 represented similar catalytic activity during the reaction. The above experimental fact implied that maybe transition metal catalysts were not necessary for the trifluoromethylacylation. Pleasingly, the trifluoromethylacylation still took place smoothly to give the product in 30% yield without any transition metal catalysts (entry 7). Subsequently, various solvents, such as N,Ndimethylformamide (DMF), acetonitrile, dimethyl sulfoxide (DMSO), toluene, tetrahydrofuran (THF), and water, were screened (entries 7−12). A relatively high yield was afforded in the solvent of water, which could be ascribed to good solubility of CF3SO2Na in water (entry 12). On the other hand, water was unfavorable to the reaction since the substrate 1a was insoluble in water. Therefore, mixed solvents were tested (entries 13−17). To our delight, moderate yields of 48% and 47% were respectively obtained in mixed solvents CH3CN− H2O and DMSO−H2O (entries 14 and 15). When the oxidant of K2S2O8 was increased to 3.0 equiv, higher yields could be achieved as shown in entries 18 and 19. Further experiments indicate that increasing the reaction temperature to 100 °C was advantageous in the solvent of DMSO−H2O, and a good yield was afforded in CH3CN−H2O with the assistance of K2CO3 (entries 20 and 21). Among the various oxidants, K2S2O8 still displayed the most excellent oxidative activity (entries 22−25). 2a was still achieved in 65% yield when the reaction was performed under a N2 atmosphere, which indicates that the oxygen was not involved in this reaction (entry 26). After ascertaining the optimal conditions, the generality of this trifluoromethylacylation reaction was explored as shown in
yieldb (%) entry
catalyst
oxidant
1 2 3 4 5 6 7 8 9 10 11 12 13
Cu(OAc)2·H2O CuBr2 CuCl2 CuBr AgNO3 FeCl2 − − − − − − −
K2S2O8 K2S2O8 K2S2O8 K2S2O8 K2S2O8 K2S2O8 K2S2O8 K2S2O8 K2S2O8 K2S2O8 K2S2O8 K2S2O8 K2S2O8
14
−
K2S2O8
15
−
K2S2O8
16
−
K2S2O8
17
−
K2S2O8
18c
−
K2S2O8
c
19
−
K2S2O8
20c,d
−
K2S2O8
21c,e
−
K2S2O8
22c,e
−
TBHP
c,e
23
−
DTBP
24c,e
−
H2O2
25c,e
−
PhI(OAc)2
26c,e
−
K2S2O8
solvent
2a
3a
DMF DMF DMF DMF DMF DMF DMF CH3CN DMSO toluene THF H2O DMF−H2O (3:7) CH3CN− H2O (3:7) DMSO− H2O (3:7) toluene− H2O (3:7) THF−H2O (3:7) CH3CN− H2O (3:7) DMSO− H2O (3:7) DMSO− H2O (3:7) CH3CN− H2O (3:7) CH3CN− H2O (3:7) CH3CN− H2O (3:7) CH3CN− H2O (3:7) CH3CN− H2O (3:7) CH3CN− H2O (3:7)
38 37 37 40 35 35 30 10 24 n.d. trace 38 41
trace trace trace n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d.
48
n.d.
47
n.d.
15
n.d.
17
n.d.
58
n.d.
60
n.d.
68
n.d.
65
n.d.
n.d.
n.d.
trace
n.d.
trace
n.d.
20:1) when R1 was methyl. However, no desired product 2q was observed when R1 was B
DOI: 10.1021/acs.orglett.8b02846 Org. Lett. XXXX, XXX, XXX−XXX
Letter
Organic Letters Scheme 2. Substrate Scope of Trifluoromethylacylationa,b
Scheme 3. Initially Hypothetical Reaction Pathways
oxidation to give the final product 2a. It is noted that pathway a is triggered by ·CF3. Also, 1a can be oxidized to the radical C26 by K2S2O8 through a single-electron transfer process, and subsequent cyclization affords radical D that captures ·CF3 to give the product 2a, which is pathway b. Please note that this pathway is triggered by radical C. Subsequently, corresponding control experiments were conducted to investigate the reaction pathway of this trifluoromethylacylation (Scheme 4). The free-radical adduct Scheme 4. Control Experiments
a Reaction conditions: 1 (0.25 mmol), CF3SO2Na (0.40 mmol), K2S2O8 (0.75 mmol), DMSO-H2O (3:7, 1.0 mL), 100 °C, 24 h, under air atmosphere; isolated yield. bReaction conditions: 1 (0.25 mmol), CF3SO2Na (0.40 mmol), K2S2O8 (0.75 mmol), K2CO3 (0.25 mmol), CH3CN-H2O (3:7, 1.0 mL), 70 °C, 24 h, under air atmosphere; isolated yield.
replaced by electron-withdrawing ethoxycarbonyl, which could be attributed to inversion of the reaction site. Additionally, 2s was obtained only in 30% yield because of the increased steric hindrance. 2-(Allyl(methyl)amino)benzaldehyde 1t could not afford the corresponding product 2t due to the construction of many unidentified byproducts, but 2u could be readily obtained when p-toluene sulfonyl (Ts) appeared on the nitrogen atom. Moreover, 1-indanones of 2v, 2w, and 2x were efficiently formed through this method. In terms of previous studies, we proposed two alternative reaction pathways for this trifluoromethylacylation as described in Scheme 3. Pathway a includes oxidation of CF3SO2Na by K2S2O8 generating ·CF3 that attacks 1a to give the radical A, and A is transformed to B through cyclization, followed by
TEMPO−CF3 (X) rather than Y was detected when 2,2,6,6tetramethyl-1-piperidinyloxy (TEMPO) was introduced to the model reaction, which indicated that this trifluoromethylacylation reaction involved a trifluoromethyl radical (Scheme 4a). Furthermore, free-radical adducts Y and Z were not detected upon adding TEMPO and removing CF3SO2Na under the standard conditions (Scheme 4b). The aforementioned results imply that the trifluoromethylacylation should proceed through pathway a. Additionally, trifluoromethylation products 5a and 6a were not detected in the reaction of 4a with C
DOI: 10.1021/acs.orglett.8b02846 Org. Lett. XXXX, XXX, XXX−XXX
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Organic Letters
(Scheme 6), whereas trifluoromethylacylation (9a was not detected) was completely suppressed. Substrates bearing both
CF3SO2Na, demonstrating that a hydrogen atom in the formyl group was necessary (Scheme 4c). Moreover, kinetic isotope experiments indicated that cleavage of the C−H bond in the formyl group was not involved during the rate-determining step (Scheme 4d). The rate-determining step of the trifluoromethylacylation reaction and the detailed process of the oxidation of B to 2a are not very clear at present. Therefore, density functional theory (DFT) calculations have been conducted to gain more insight into them.27 Initially, trifluoromethylacylation is triggered by ·CF3 that is derived from oxidation of CF3SO2Na in the presence of K2S2O8. DFT calculations show that this process is endothermal (ΔG = 40.8 kcal/mol), indicating that increasing the temperature is favorable to this reaction (Scheme 5). Then the free energy profile for pathway a was
Scheme 6. Substrate Scope of Trifluoromethylarylationa
Scheme 5. Overall Energy for the Oxidation of CF3SO2Na to ·CF3 by K2S2O8
depicted as shown in Figure 1. The addition of ·CF3 to 1a gives Int1 (−33.4 kcal/mol) through an identified transition state TS1 (activation energy is only 0.8 kcal/mol). A six-membered transition state TS2 can be recognized from Int1 with a C−C bond length of 2.100 Å. Transformation of Int2 to Int3 identifies TS3 via hydrogen atom transfer, in which the activation energy is up to 24.7 kcal/mol. It is noteworthy that the bond length of C−H (1.271 Å) is longer than that of O−H (1.242 Å) in TS3, which suggests that the C−H bond is activated by an oxygen atom and is more easily cleaved. In the presence of K2S2O8, Int3 is converted to a key transition state TS4 that can give the final product via a synergistic effect of the O−H−O−O bond cleavage and formation. Pathway a is strongly exothermic, and low activation energy is represented in its steps. Transformation of Int2 to Int3 should not be the rate-determining step for the reaction according to the result obtained in Scheme 4d, even though its activation energy is up to 24.7 kcal/mol. Therefore, oxidation of CF3SO2Na to ·CF3 by K2S2O8 is involved in the rate-determining step. The above results showed that the radical Int1 could be readily formed through the addition of ·CF3 to a substrate. In this context, we deduced that the trifluoromethylarylation could also selectively take place by altering substrates. Interestingly, when 7a was employed as the starting material, trifluoromethylarylation product 8a was obtained in 60% yield
a Reaction conditions: 7 (0.25 mmol), CF3SO2Na (0.40 mmol), K2S2O8 (0.75 mmol), DMSO−H2O (3:7, 1.0 mL), or DMSO (1.0 mL), 50 °C, 24 h, under air atmosphere; isolated yield.
electron-donating (8b−8d) and electron-withdrawing (8e−8i) groups on the benzene ring could afford the corresponding trifluoromethylarylation products in good yields. Note that steric hindrance had a negative effect on this difunctionalization reaction. Therefore, relatively low yields of the products 8c (vs 8d) and 8f (vs 8g) with steric bulk, especially 8j (vs 8i), were obtained. Without a formyl group, the trifluoromethylarylation could also be smoothly carried out to afford the desired products 8k−8n, indicating a broad substrate generality of this method. When the oxygen atom was replaced by a Tssubstituted nitrogen atom, 8o was successfully achieved even though a low yield of 31% was obtained. Five-membered 2,3-
Figure 1. Energy profile for pathway a. D
DOI: 10.1021/acs.orglett.8b02846 Org. Lett. XXXX, XXX, XXX−XXX
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Organic Letters
Fustero, S.; Soloshonok, V. A.; Liu, H. Chem. Rev. 2014, 114, 2432. (m) Alonso, C.; Marigorta, E. M. D.; Rubiales, G.; Palacios, F. Chem. Rev. 2015, 115, 1847. (2) (a) Egami, H.; Shimizu, R.; Sodeoka, M. Tetrahedron Lett. 2012, 53, 5503. (b) Egami, H.; Shimizu, R.; Usui, Y.; Sodeoka, M. J. Fluorine Chem. 2014, 167, 172. (c) Wang, X.-P.; Lin, J.-H.; Zhang, C.-P.; Xiao, J.-C.; Zheng, X. Beilstein J. Org. Chem. 2013, 9, 2635. (d) Egami, H.; Usui, Y.; Kawamura, S.; Nagashima, S.; Sodeoka, M. Chem. - Asian J. 2015, 10, 2190. (e) Feng, C.; Loh, T.-P. Chem. Sci. 2012, 3, 3458. (f) Feng, C.; Loh, T.-P. Angew. Chem., Int. Ed. 2013, 52, 12414. (3) (a) Lin, Q.-Y.; Xu, X.-H.; Qing, F.-L. J. Org. Chem. 2014, 79, 10434. (b) Tomita, R.; Yasu, Y.; Koike, T.; Akita, M. Beilstein J. Org. Chem. 2014, 10, 1099. (4) (a) Zhang, X.; Huang, P.; Li, Y.; Duan, C. Org. Biomol. Chem. 2015, 13, 10917. (b) Wu, L.-H.; Zhao, K.; Loh, T.-P. Org. Chem. Front. 2017, 4, 1872. (5) (a) Iqbal, N.; Choi, S.; Kim, E.; Cho, E. J. Org. Chem. 2012, 77, 11383. (b) Feng, Z.; Min, Q.-Q.; Zhao, H.-Y.; Gu, J.-W.; Zhang, X. Angew. Chem., Int. Ed. 2015, 54, 1270. (c) Straathof, N. J. W.; Cramer, S. E.; Hessel, V.; Noël, T. Angew. Chem., Int. Ed. 2016, 55, 15549. (6) For selected examples, see: Chen, Z.-M.; Bai, W.; Wang, S.-H.; Yang, B.-M.; Tu, Y.-Q.; Zhang, F.-M. Angew. Chem., Int. Ed. 2013, 52, 9781. (b) Zheng, J.; Deng, Z.; Zhang, Y.; Cui, S. Adv. Synth. Catal. 2016, 358, 746. (c) Kong, W.; Casimiro, M.; Merino, E.; Nevado, C. J. Am. Chem. Soc. 2013, 135, 14480. (d) Wang, F.; Wang, D.; Mu, X.; Chen, P.; Liu, G. J. Am. Chem. Soc. 2014, 136, 10202. (e) Mu, X.; Wu, T.; Wang, H.-Y.; Guo, Y.-L.; Liu, G. J. Am. Chem. Soc. 2012, 134, 878. (f) Egami, H.; Shimizu, R.; Kawamura, S.; Sodeoka, M. Angew. Chem., Int. Ed. 2013, 52, 4000. (g) Wang, Q.; Han, G.; Liu, Y.; Wang, Q. Adv. Synth. Catal. 2015, 357, 2464. (h) Zheng, L.; Yang, C.; Xu, Z.; Gao, F.; Xia, W. J. Org. Chem. 2015, 80, 5730. (i) Carboni, A.; Dagousset, G.; Magnier, E.; Masson, G. Chem. Commun. 2014, 50, 14197. (j) Xu, P.; Xie, J.; Xue, Q.; Pan, C.; Cheng, Y.; Zhu, C. Chem. - Eur. J. 2013, 19, 14039. (k) Egami, H.; Shimizu, R.; Sodeoka, M. J. Fluorine Chem. 2013, 152, 51. (7) (a) Li, Z.-L.; Li, X.-H.; Wang, N.; Yang, N.-Y.; Liu, X.-Y. Angew. Chem., Int. Ed. 2016, 55, 15100. (b) Liu, Z.; Bai, Y.; Zhang, J.; Yu, Y.; Tan, Z.; Zhu, G. Chem. Commun. 2017, 53, 6440. (8) (a) Egami, H.; Kawamura, S.; Miyazaki, A.; Sodeoka, M. Angew. Chem., Int. Ed. 2013, 52, 7841. (b) Lin, J.-S.; Xiong, Y.-P.; Ma, C.-L.; Zhao, L.-J.; Tan, B.; Liu, X.-Y. Chem. - Eur. J. 2014, 20, 1332. (c) Dagousset, G.; Carboni, A.; Magnier, E.; Masson, G. Org. Lett. 2014, 16, 4340. (d) Yasu, Y.; Koike, T.; Akita, M. Org. Lett. 2013, 15, 2136. (e) Chang, B.; Su, Y.; Huang, D.; Wang, K.-H.; Zhang, W.; Shi, Y.; Zhang, X.; Hu, Y. J. Org. Chem. 2018, 83, 4365. (9) (a) Carboni, A.; Dagousset, G.; Magnier, E.; Masson, G. Org. Lett. 2014, 16, 1240. (b) Yasu, Y.; Koike, T.; Akita, M. Angew. Chem., Int. Ed. 2012, 51, 9567. (c) Jiang, X.-Y.; Qing, F.-L. Angew. Chem., Int. Ed. 2013, 52, 14177. (d) Egami, H.; Shimizu, R.; Sodeoka, M. Tetrahedron Lett. 2012, 53, 5503. (e) Zhu, R.; Buchwald, S. L. J. Am. Chem. Soc. 2012, 134, 12462. (f) Deng, Q.-H.; Chen, J.-R.; Wei, Q.; Zhao, Q.-Q.; Lu, L.-Q.; Xiao, W.-J. Chem. Commun. 2015, 51, 3537. (g) Janson, P. G.; Ghoneim, I.; Ilchenko, N. O.; Szabó, K. J. Org. Lett. 2012, 14, 2882. (h) Ye, J.-H.; Song, L.; Zhou, W.-J.; Ju, T.; Yin, Z.-B.; Yan, S.-S.; Zhang, Z.; Li, J.; Yu, D.-G. Angew. Chem., Int. Ed. 2016, 55, 10022. (10) (a) Xu, T.; Cheung, C. W.; Hu, X. Angew. Chem., Int. Ed. 2014, 53, 4910. (b) Wallentin, C.-J.; Nguyen, J. D.; Finkbeiner, P.; Stephenson, C. R. J. J. Am. Chem. Soc. 2012, 134, 8875. (c) Oh, S. H.; Malpani, Y. R.; Ha, N.; Jung, Y.-S.; Han, S. B. Org. Lett. 2014, 16, 1310. (d) Yu, W.; Xu, X.-H.; Qing, F.-L. Adv. Synth. Catal. 2015, 357, 2039. (e) Guo, J.-Y.; Wu, R.-X.; Jin, J.-K.; Tian, S.-K. Org. Lett. 2016, 18, 3850. (11) (a) Wang, F.; Qi, X.; Liang, Z.; Chen, P.; Liu, G. Angew. Chem., Int. Ed. 2014, 53, 1881. (b) Liang, Z.; Wang, F.; Chen, P.; Liu, G. Org. Lett. 2015, 17, 2438. (c) Han, G.; Wang, Q.; Chen, L.; Liu, Y.; Wang, Q. Adv. Synth. Catal. 2016, 358, 561. (d) Jin, W.; Wu, M.; Xiong, Z.; Zhu, G. Chem. Commun. 2018, 54, 7924. (e) Yu, L.-Z.; Xu, Q.; Tang, X.-Y.; Shi, M. ACS Catal. 2016, 6, 526. (f) Liu, S.; Jie, J.; Yu, J.; Yang,
dihydrobenzofuran 8p was not detected, which was similar to the result of 3a obtained in Table 1. In summary, we have demonstrated a convenient and versatile intramolecular trifluoromethylacylation and -arylation of alkenes by use of stable and inexpensive CF3SO2Na as the trifluoromethylation reagent and K2S2O8 as the oxidant via a free-radical process. This method affords facile and accurate access to a range of chroman-4-ones and chromanes in moderate to good yields with excellent chemoselectivity. Control experiments and DFT calculations suggest that the triggered transformation for the construction of ·CF3 is embodied in the rate-determining step and subsequent freeradical addition, cyclization, and oxidation can efficiently take place in the presence of K2S2O8. Prominent advantages indicate that this difunctionalization reaction can be readily performed in aqueous media under mild conditions without a transition metal catalyst. Further exploration of a green synthetic method, especially in aqueous media, is ongoing in our laboratory.
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ASSOCIATED CONTENT
* Supporting Information S
The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.orglett.8b02846. General experimental procedures, computational details, characterization data and copies of 1H, 13C, and 19F NMR spectra of products (PDF)
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AUTHOR INFORMATION
Corresponding Authors
*E-mail:
[email protected]. *E-mail:
[email protected]. ORCID
Lin Tang: 0000-0003-0477-2481 Weihao Rao: 0000-0001-6197-0148 Notes
The authors declare no competing financial interest.
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ACKNOWLEDGMENTS This work was supported by the National Natural Science Foundation of China (21602190, 21803050), the Foundation of Department of Science and Technology of Henan Province (172102210456), the Foundation of Department of Education of Henan Province (17A150049), and the Nanhu Scholars Program for Young Scholars of XYNU.
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REFERENCES
(1) (1) For selected reviews and examples, see: (a) Müller, K.; Faeh, C.; Diederich, F. Science 2007, 317, 1881. (b) Purser, S.; Moore, P. R.; Swallow, S.; Gouverneur, V. Chem. Soc. Rev. 2008, 37, 320. (c) Pacheco, M. C.; Purser, S.; Gouverneur, V. Chem. Rev. 2008, 108, 1943. (d) Special issue on “Fluorine in the life sciences”, ChemBioChem. 2004, 5, 557. (e) Schlosser, M. Angew. Chem., Int. Ed. 2006, 45, 5432. (f) Kirk, K. L. Org. Process Res. Dev. 2008, 12, 305. (g) Zhang, C. Adv. Synth. Catal. 2014, 356, 2895. (h) Studer, A. Angew. Chem., Int. Ed. 2012, 51, 8950. (i) Su, Y.-M.; Feng, G.-S.; Wang, Z.-Y.; Lan, Q.; Wang, X.-S. Angew. Chem., Int. Ed. 2015, 54, 6003. (j) Furuya, T.; Kamlet, A. S.; Ritter, T. Nature 2011, 473, 470. (k) Li, Z.; Cui, Z.; Liu, Z.-Q. Org. Lett. 2013, 15, 406. (l) Wang, J.; Sánchez-Roselló, M.; Aceña, J. L.; del Pozo, C.; Sorochinsky, A. E.; E
DOI: 10.1021/acs.orglett.8b02846 Org. Lett. XXXX, XXX, XXX−XXX
Letter
Organic Letters X. Adv. Synth. Catal. 2018, 360, 267. (g) Zhang, Y.; Han, X.; Zhao, J.; Qian, Z.; Li, T.; Tang, Y.; Zhang, H.-Y. Adv. Synth. Catal. 2018, 360, 2659. (h) Sahoo, B.; Li, J.-L.; Glorius, F. Angew. Chem., Int. Ed. 2015, 54, 11577. (12) Lu, Q.; Liu, C.; Huang, Z.; Ma, Y.; Zhang, J.; Lei, A. Chem. Commun. 2014, 50, 14101. (13) (a) Li, L.; Deng, M.; Zheng, S.-C.; Xiong, Y.-P.; Tan, B.; Liu, X.-Y. Org. Lett. 2014, 16, 504. (b) Wei, W.; Wen, J.; Yang, D.; Liu, X.; Guo, M.; Dong, R.; Wang, H. J. Org. Chem. 2014, 79, 4225. (c) Wu, Z.; Wang, D.; Liu, Y.; Huan, L.; Zhu, C. J. Am. Chem. Soc. 2017, 139, 1388. (d) Wang, H.; Xu, Q.; Yu, S. Org. Chem. Front. 2018, 5, 2224. (e) Yang, N.-Y.; Li, Z.-L.; Tan, B.; Liu, X.-Y. Chem. Commun. 2016, 52, 9052. (f) Zhang, L.; Li, Z.; Liu, Z.-Q. Org. Lett. 2014, 16, 3688. (g) Jiang, Y.-Y.; Dou, G.-Y.; Xu, K.; Zeng, C.-C. Org. Chem. Front. 2018, 5, 2573. (14) Shang, X.-J.; Liu, D.; Liu, Z.-Q. Org. Chem. Front. 2018, 5, 2856. (15) (a) Tang, X.; Studer, A. Chem. Sci. 2017, 8, 6888. (b) Zhou, S.; Song, T.; Chen, H.; Liu, Z.; Shen, H.; Li, C. Org. Lett. 2017, 19, 698. (c) Jiang, H.; He, Y.; Cheng, Y.; Yu, S. Org. Lett. 2017, 19, 1240. (16) (a) Hang, Z.; Li, Z.; Liu, Z.-Q. Org. Lett. 2014, 16, 3648. (b) Liu, Z.-Q.; Liu, D. J. Org. Chem. 2017, 82, 1649. (17) Ricci, P.; Khotavivattana, T.; Pfeifer, L.; Médebielle, M.; Morphy, J. R.; Gouverneur, V. Chem. Sci. 2017, 8, 1195. (18) (a) Li, Y.; Studer, A. Angew. Chem., Int. Ed. 2012, 51, 8221. (b) Ryzhakov, D.; Jarret, M.; Guillot, R.; Kouklovsky, C.; Vincent, G. Org. Lett. 2017, 19, 6336. (19) For selected examples, see: (a) Lin, Y.-P.; Hsu, F.-L.; Chen, C.S.; Chern, J.-W.; Lee, M.-H. Phytochemistry 2007, 68, 1189. (b) Folmer, F.; Harrison, W. T. A.; Tabudravu, J. N.; Jaspars, M.; Aalbersberg, W.; Feussner, K.; Wright, A. D.; Dicato, M.; Diederich, M. J. Nat. Prod. 2008, 71, 106. (c) Gaspar, A.; Matos, M. J.; Garrido, J.; Uriarte, E.; Borges, F. Chem. Rev. 2014, 114, 4960. (d) FridénSaxin, M.; Seifert, T.; Landergren, M. R.; Suuronen, T.; LahtelaKakkonen, M.; Jarho, E. M.; Luthman, K. J. Med. Chem. 2012, 55, 7104. (e) Fan, J.; Sun, W.; Wang, Z.; Peng, X.; Li, Y.; Cao, J. Chem. Commun. 2014, 50, 9573. (20) For selected examples, see: (a) Mahal, H. S.; Rai, H. S.; Venkataraman, K. J. Chem. Soc. 1935, 866. (b) Du, Z.; Ng, H.; Zhang, K.; Zeng, H.; Wang, J. Org. Biomol. Chem. 2011, 9, 6930. (c) Yoshida, M.; Fujino, Y.; Doi, T. Org. Lett. 2011, 13, 4526. (d) Yoshida, M.; Saito, K.; Fujino, Y.; Doi, T. Chem. Commun. 2012, 48, 11796. (e) Yatabe, T.; Jin, X.; Yamaguchi, K.; Mizuno, N. Angew. Chem., Int. Ed. 2015, 54, 13302. (f) Zhong, S.; Liu, Y.; Cao, X.; Wan, J.-P. ChemCatChem 2017, 9, 465. (21) For selected examples, see: (a) Devitt, P. F.; Timoney, A.; Vickars, M. A. J. Org. Chem. 1961, 26, 4941. (b) Santos, C. M. M.; Silva, A. M. S.; Cavaleiro, J. A. S. Eur. J. Org. Chem. 2003, 2003, 4575. (c) Zhao, J.; Zhao, Y.; Fu, H. Org. Lett. 2012, 14, 2710. (d) Menezes, J. C. L.; Vaz, L. B. A.; Vieira, P. M.; Fonseca, K.; Carneiro, C. M.; Taylor, J. G. Molecules 2015, 20, 43. (e) Stanek, F.; Stodulski, M. Tetrahedron Lett. 2016, 57, 3841. (22) For selected examples, see: (a) Miao, H.; Yang, Z. Org. Lett. 2000, 2, 1765. (b) Liu, J.; Song, W.; Yue, Y.; Liu, R.; Yi, H.; Zhuo, K.; Lei, A. Chem. Commun. 2015, 51, 17576. (c) Jiang, C.; Xiong, Z.; Jin, S.; Gao, P.; Tang, Y.; Wang, Y.; Du, C.; Wang, X.; Liu, Y.; Lin, B.; Liu, Y.; Cheng, M. Chem. Commun. 2016, 52, 11516. (d) Wu, X.; Neumann, H.; Beller, M. Chem. - Eur. J. 2012, 18, 12595. (e) Zhao, X.; Zhou, J.; Lin, S.; Jin, X.; Liu, R. Org. Lett. 2017, 19, 976. (f) Yang, D.; Wang, Z.; Wang, X.; Sun, H.; Xie, Z.; Fan, J.; Zhang, G.; Zhang, W.; Gao, Z. J. Mol. Catal. A: Chem. 2017, 426, 24. (g) Yue, Y.; Peng, J.; Wang, D.; Bian, Y.; Sun, P.; Chen, C. J. Org. Chem. 2017, 82, 5481. (h) Zhai, D.; Chen, L.; Jia, M.; Ma, S. Adv. Synth. Catal. 2018, 360, 153. (23) (a) Banerjee, D.; Kayal, U.; Maiti, G. Tetrahedron Lett. 2016, 57, 1667. (b) Dubrovskiy, A. V.; Larock, R. C. Org. Lett. 2010, 12, 3117. (c) Narayan, R.; Antonchick, A. P. Chem. - Eur. J. 2014, 20, 4568. (d) Kim, H. Y.; Song, E.; Oh, K. Org. Lett. 2017, 19, 312. (e) Khoobi, M.; Alipour, M.; Zarei, S.; Jafarpour, F.; Shafiee, A. Chem.
Commun. 2012, 48, 2985. (f) Zhang, S.; Wan, C.; Wang, Q.; Zhang, B.; Gao, L.; Zha, Z.; Wang, Z. Eur. J. Org. Chem. 2013, 2013, 2080. (g) Lee, J.; Yu, J.; Son, S. H.; Heo, J.; Kim, T.; An, J.-Y.; Inn, K.-S.; Kim, N.-J. Org. Biomol. Chem. 2016, 14, 777. (h) Hirano, K.; Biju, A. T.; Piel, I.; Glorius, F. J. Am. Chem. Soc. 2009, 131, 14190. (i) Zhao, J.; Li, P.; Li, X.; Xia, C.; Li, F. Chem. Commun. 2016, 52, 3661. (j) Jhuang, H.-S.; Reddy, D. M.; Chen, T.-H.; Lee, C.-F. Asian J. Org. Chem. 2016, 5, 1452. (k) Yang, W.-C.; Dai, P.; Luo, K.; Ji, Y.-G.; Wu, L. Adv. Synth. Catal. 2017, 359, 2390. (l) Jung, S.; Kim, J.; Hong, S. Adv. Synth. Catal. 2017, 359, 3945. (24) (a) Tang, L.; Sun, H.; Li, Y.; Zha, Z.; Wang, Z. Green Chem. 2012, 14, 3423. (b) Tang, L.; Guo, X.; Li, Y.; Zhang, S.; Zha, Z.; Wang, Z. Chem. Commun. 2013, 49, 5213. (c) Tang, L.; Yang, Y.; Wen, L.; Zhang, S.; Zha, Z.; Wang, Z. Org. Chem. Front. 2015, 2, 114. (d) Tang, L.; Wang, P.; Fan, Y.; Yang, X.; Wan, C.; Zha, Z. ChemCatChem 2016, 8, 3565. (e) Tang, L.; Yang, Y.; Wen, L.; Yang, X.; Wang, Z. Green Chem. 2016, 18, 1224. (f) Tang, L.; Yang, Z.; Sun, T.; Zhang, D.; Ma, X.; Rao, W.; Zhou, Y. Adv. Synth. Catal. 2018, 360, 3055. (25) Tang, L.; Wen, L.; Sun, T.; Zhang, D.; Yang, Z.; Feng, C.; Wang, Z. Asian J. Org. Chem. 2017, 6, 1683. (26) Shi, Z.; Glorius, F. Chem. Sci. 2013, 4, 829. (27) See the Supporting Information for computational details.
F
DOI: 10.1021/acs.orglett.8b02846 Org. Lett. XXXX, XXX, XXX−XXX
