Letter Cite This: Org. Lett. XXXX, XXX, XXX−XXX
pubs.acs.org/OrgLett
Synthesis of 3‑(Methylsulfonyl)benzo[b]thiophenes from Methyl(2alkynylphenyl)sulfanes and Sodium Metabisulfite via a Radical Relay Strategy Xinxing Gong,†,‡ Mengjiao Wang,‡ Shengqing Ye,*,† and Jie Wu*,†,‡ †
Institute for Advanced Studies, Taizhou University, 1139 Shifu Avenue, Taizhou 318000, China Department of Chemistry, Fudan University, 2005 Songhu Road, Shanghai 200438, China
‡
Org. Lett. Downloaded from pubs.acs.org by TULANE UNIV on 01/31/19. For personal use only.
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ABSTRACT: A radical relay strategy for the generation of 3(methylsulfonyl)benzo[b]thiophenes through a reaction of methyl(2-alkynylphenyl)sulfanes with sodium metabisulfite in the presence of a photocatalyst under visible light irradiation is developed. This photoinduced sulfonylation proceeds efficiently under mild conditions by using a catalytic amount of sodium methylsulfinate as an initiator. During the reaction process, the methyl radical generated in situ is the key intermediate, which undergoes a radical relay with the combination of sulfur dioxide to afford methylsulfonyl-containing compounds.
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continuously focused on the synthesis of sulfonyl compounds with the insertion of sulfur dioxide.13 We envisioned that the methyl radical generated in situ might combine with sulfur dioxide to provide the methylsulfonyl group. Thus, we proposed a radical relay strategy, as shown in Scheme 1. We
he methyl group is one of the most common fragments in organic compounds, which has broad applications in pharmaceutical and many biological processes due to the magic methyl effect.1 It is estimated that more than 67% of the top-selling drugs contain at least one methyl group.2 Thus, significant efforts have been focused toward introduction of the methyl group into small molecules and biomacromolecules in recent years.3 Traditionally, the methyl group could be introduced by transition-metal-catalyzed reactions of methyl halides,4 methylboronic reagents,5 or organometallic reagents.6 Subsequently, methylation via a radical process was developed and became an alternative to realize such a process.7 For instance, In 2018, Zuo and co-workers reported the formation of methyl radical from methane in an economical pathway, which provided an unprecedented strategy for the generation of methyl radical.8 In continuation of our interest in sulfonyl compounds, we specifically focus on the methylsulfonyl unit, which is found broadly in drugs.9 Therefore, method development by introducing the methylsulfonyl group into small molecules from the methyl radical will be highly desirable. Because of the unique significance of the methyl group and continuous efforts in constructing methyl fragments, our interest arose from our previous work on the cyclization reaction of N,N-dimethyl-2-alkynylanilines, which gave rise to 1-methyl-1,4-dihydroquinoline derivatives by releasing a methyl group.10c Such phenomena could also be witnessed in other cyclization reactions of N,N-dimethyl-2-alkynylanilines,10 2-alkynylanisoles,11 and methyl(2-alkynylphenyl)sulfanes.12 In these reactions, several heterocycles were formed with one methyl group as waste to be released. On the basis of these results, we hypothesized that the in situ generated methyl radical in the reactions would be a useful and economic methyl source instead of a waste. In the past few years, we have © XXXX American Chemical Society
Scheme 1. Proposed Radical Relay Strategy
conceived that the starting material with a methyl group would initially provide a methyl radical under suitable conditions. Then the methyl radical would be trapped by sulfur dioxide leading to a methylsulfonyl radical, which would subsequently react with the starting material giving rise to a methylsulfonylcontaining product with the release of a methyl radical. The methyl radical would re-enter the cycle to continuously provide the product. Herein, we report a radical relay strategy for the generation of 3-(methylsulfonyl)benzo[b]thiophenes through a reaction of methyl(2-alkynylphenyl)sulfanes with sodium metabisulfite in the presence of a photocatalyst under visible light irradiation. This photoinduced sulfonylation proceeds efficiently under mild conditions by using a catalytic amount of sodium methylsulfinate as an initiator. During the reaction process, the methyl radical generated in situ is the key intermediate, which undergoes a radical relay with the Received: January 9, 2019
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DOI: 10.1021/acs.orglett.9b00100 Org. Lett. XXXX, XXX, XXX−XXX
Letter
Organic Letters combination of sulfur dioxide to afford methylsulfonylcontaining compounds. As mentioned above, we have disclosed the transformations with the insertion of sulfur dioxide through a radical process.14 Among the surrogates of sulfur dioxide, metabisulfite15 seemed to be a superior option due to its easy availability, convenience, and great potential in organic synthesis in comparison with 1,4diazabicyclo[2.2.2]octane-sulfur dioxide (DABCO· (SO2)2).16,17 On the basis of our previous results and other reports,12,13 methyl(2-alkynylphenyl)sulfane was selected as the starting material for reaction development. We therefore started to explore the feasibility of this radical relay strategy for the generation of methylsulfonyl-containing heterocycles. At the beginning, a model reaction of methyl (2-(phenylethynyl)phenyl)sulfane 1a and sodium metabisulfite was carried out in 1,2-dichloroethane (DCE) at room temperature. Since the final product contained a methylsulfonyl group, we therefore considered using sodium methylsulfinate as an initiator. We postulated that, assisted by visible light irradiation, methylsulfinate would be converted to the methylsulfonyl radical via a single electron transfer (SET), thus initiating the reaction. At the outset, the reaction was performed in the dark. As expected, no desired product was obtained, which confirmed our hypothesis (Table 1, entry 1). Subsequently, the reaction occurred in the presence of a catalytic amount of Rodamin 6G and sodium methylsulfinate. We reasoned that the excited oxidative photocatalyst would promote the formation of the methylsulfonyl radical from sodium methylsulfinate. To our delight, the corresponding 3-
(methylsulfonyl)benzo[b]thiophene 2a was produced in 30% yield (Table 1, entry 2). The structure of compound 2a was confirmed by X-ray diffraction analysis (CCDC 1881727). We next screened other photocatalysts (Table 1, entries 3−5), which showed that Ru(ppy)3Cl2 was the best choice affording the desired product 2a in 98% yield (Table 1, entry 5). No reaction took place in the absence of sodium methylsulfinate (Table 1, entry 6). The amount of sodium methylsulfinate was then changed, and the results revealed that a good yield could be obtained as well in the presence of 30 mol % of sodium methylsulfinate (Table 1, entry 9). We also examined the reaction in different solvents (Table 1, entries 11−15). However, no better yield was observed. No reaction occurred without the addition of a photocatalyst (Table 1, entry 16). With the optimized conditions in hand, we then explored the generality of this radical relay reaction for the generation of 3-(methylsulfonyl)benzo[b]thiophenes through a reaction of methyl(2-alkynylphenyl)sulfanes with sodium metabisulfite in the presence of photocatalyst under visible light irradiation. The results are presented in Scheme 2. A range of methyl(2Scheme 2. Scope Investigation for the Reaction of Methyl(2-alkynylphenyl)sulfanes 1 and Sodium Metabisulfitea
Table 1. Initial Studies for the Photoinduced Reaction of Methyl (2-(Phenylethynyl)phenyl)sulfane 1a and Sodium Metabisulfitea
entry 1b 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17c
PC − Rhodamine 6G Eosin Y Ir[dF(CF3)ppy]2(dtbbpy) PF6 Ru(bpy)3Cl2 Ru(bpy)3Cl2 Ru(bpy)3Cl2 Ru(bpy)3Cl2 Ru(bpy)3Cl2 Ru(bpy)3Cl2 Ru(bpy)3Cl2 Ru(bpy)3Cl2 Ru(bpy)3Cl2 Ru(bpy)3Cl2 Ru(bpy)3Cl2 − Ru(bpy)3Cl2
x (mol %)
solvent
yield (%)
− 50 50 50
DCE DCE DCE DCE
n.d. 30 66 90
50 0 10 20 30 40 30 30 30 30 30 50 30
DCE DCE DCE DCE DCE DCE DMF DMSO 1,4-dioxane MeCN DCM DCE DCE
98 n.d. 42 66 81 82 35 trace trace 44 50 n.d. 72
a
Isolated yield based on methyl(2-alkynylphenyl)sulfane 1.
alkynylphenyl)sulfanes were examined under the conditions. It was found that reactions of methyl(2-alkynylphenyl)sulfanes with an aryl group at the R2 position proceeded smoothly to provide the corresponding products in moderate to good yields. Several sensitive functional groups including chloro, bromo, fluoro, cyano, ester, and aldehyde were all compatible. For example, the aldehyde-containing product 2m was produced in 67% yield. Additionally, the thiophenyl group
a Reaction conditions: methyl (2-(phenylethynyl)phenyl)sulfane 1a (0.2 mmol), Na2S2O5 (0.4 mmol), NaSO2CH3 (x mol %), photocatalyst (2 mol %), solvent (2.0 mL), rt, 12 h, 35 W CFL. Isolated yield based on methyl (2-(phenylethynyl)phenyl)sulfane 1a. b Without light. cNa2S2O5 was replaced by K2S2O5.
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DOI: 10.1021/acs.orglett.9b00100 Org. Lett. XXXX, XXX, XXX−XXX
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Organic Letters could be tolerated as well under the reaction conditions, and the corresponding product 2l was generated in 96% yield. However, no desired product was obtained when the aryl group at the R2 position of the substrate was changed to 2pyridinyl, tert-butyl, trimethylsilyl, or ester. We assumed that the aryl group at the R2 position would stabilize the benzyl radical, which was the key intermediate to facilitate further cyclization. We further extended the substrate to 1-methoxy-2-(phenylethynyl)benzene 3 and N,N-dimethyl-2-alkynylaniline 4 in the reaction of sodium metabisulfite under the standard conditions, with an expectation to obtain 3-(methylsulfonyl)benzo[b]furan and 3-(methylsulfonyl)indole. However, no reaction occurred when 1-methoxy-2-(phenylethynyl)benzene 3 was employed. Only a trace amount of product was detected when the substrate was replaced by N,N-dimethyl-2-alkynylaniline 4 (Scheme 3).
reaction with sodium metabisulfite under the standard conditions. Simultaneously, we observed the formation of 3(ethylsulfonyl)-2-phenylbenzo[b]thiophene 6 with a 30% isolated yield. This result showed that the ethyl radical would be released from ethyl (2-(phenylethynyl)phenyl)sulfane 5 to further capture sulfur dioxide leading to the ethylsulfonyl radical (Scheme 4, eq 3). Additionally, a threecomponent reaction of 4-methylphenyldiazonium tetrafluoroborate, methyl (2-(phenylethynyl)phenyl)sulfane 1a, and sodium metabisulfite was examined. It was found that the corresponding sulfonylated product 2a was furnished in 46% yield, along with the formation of 3-tosylbenzo[b]thiophene 7 in 40% yield (Scheme 4, eq 4). These results all demonstrated that the methyl radical was involved during the reaction process. On the basis of the above-mentioned results, a plausible mechanism is proposed, as outlined in Scheme 5. We
Scheme 3. Reactions of 1-Methoxy-2(phenylethynyl)benzene 3 or N,N-Dimethyl-2alkynylaniline 4 with Sodium Metabisulfite
Scheme 5. Plausible Mechanism
With a radical relay process hypothesized, several control experiments were carried out to gain more insight into the mechanism. The model reaction of methyl (2-(phenylethynyl)phenyl)sulfane 1a with sodium metabisulfite under the standard conditions was hampered when 4.0 equiv of TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl) were added (Scheme 4, eq 1). The desired product 2a could be also obtained in 21% yield when the methyl radical was generated in situ from di-tert-butyl peroxide in the presence of iron(II) chloride (Scheme 4, eq 2). Interestingly, compound 2a was afforded in 26% yield when ethyl (2-(phenylethynyl)phenyl)sulfane 5 was used as a replacement of substrate 1a in the
postulated that in the presence of the excited state of the photocatalyst, methylsulfinate would be oxidized via a single electron transfer (SET) to provide the methylsulfonyl radical as an initiator (for the fluorescence-quenching experiment, see SI). The methylsulfonyl radical would then attack the triple bond of methyl(2-alkynylphenyl)sulfane 1 leading to the cyclized product 2, with the release of a methyl radical. The released methyl radical would be subsequently trapped by sulfur dioxide, giving rise to the methylsulfonyl radical. Then the methylsulfonyl radical would react with methyl(2-alkynylphenyl)sulfane 1, providing the final product through vinyl radical intermediate A, with the regeneration of the methyl radical. In this process, the methyl radical relay combined with the insertion of sulfur dioxide would provide an efficient route to methylsulfonyl-containing compounds. In summary, we have disclosed a radical relay strategy for the generation of 3-(methylsulfonyl)benzo[b]thiophenes through a reaction of methyl(2-alkynylphenyl)sulfanes with sodium metabisulfite in the presence of a photocatalyst under visible light irradiation. This photoinduced sulfonylation proceeds efficiently under mild conditions by using a catalytic amount of sodium methylsulfinate as an initiator. A plausible mechanism is proposed with experimental evidence. During the reaction process, the methyl radical generated in situ is the key intermediate, which undergoes a radical relay with the combination of sulfur dioxide to afford methylsulfonylcontaining compounds.
Scheme 4. Control Experiments
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DOI: 10.1021/acs.orglett.9b00100 Org. Lett. XXXX, XXX, XXX−XXX
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Organic Letters
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J.; Zhang, W. Green Chem. 2017, 19, 919. (c) Yang, Y.; Bao, Y.; Guan, Q.; Sun, Q.; Zha, Z.; Wang, Z. Green Chem. 2017, 19, 112. (d) Tan, F.; Hu, M.; Song, R.; Li, J. Adv. Synth. Catal. 2017, 359, 3602. (e) Kubo, T.; Chatani, N. Org. Lett. 2016, 18, 1698. (f) Xu, Z.; Yan, C.; Liu, Z. Org. Lett. 2014, 16, 5670. (g) Zhang, Y.; Feng, J.; Li, C. J. Am. Chem. Soc. 2008, 130, 2900. (8) Hu, A.; Guo, J. J.; Pan, H.; Zuo, Z. Science 2018, 361, 668. (9) (a) Feng, M.; Tang, B.; Liang, S.; Jiang, X. Curr. Top. Med. Chem. 2016, 16, 1200. (b) Mori, T.; Nishimura, T.; Yamamoto, T.; Doi, I.; Miyazaki, E.; Osaka, I.; Takimiya, K. J. Am. Chem. Soc. 2013, 135, 13900. (c) Takimiya, K.; Shinamura, S.; Osaka, I.; Miyazaki, E. Adv. Mater. 2011, 23, 4347. (d) Minatti, A.; Muñiz, K. Chem. Soc. Rev. 2007, 36, 1142. (e) Chemler, S. R.; Fuller, P. H. Chem. Soc. Rev. 2007, 36, 1153. (10) For selected examples, see: (a) Yao, B.; Wang, Q.; Zhu, J. Chem. - Eur. J. 2014, 20, 12255. (b) Pan, X.; Luo, Y.; Kuang, Y.; Li, G. Org. Biomol. Chem. 2014, 12, 5861. (c) Gogoi, A.; Guin, S.; Rout, S. K.; Patel, B. K. Org. Lett. 2013, 15, 1802. (d) Xia, X.; Wang, N.; Zhang, L.; Song, X.; Liu, X.; Liang, Y. J. Org. Chem. 2012, 77, 9163. (e) Yao, B.; Wang, Q.; Zhu, J. Angew. Chem., Int. Ed. 2012, 51, 12311. (11) For selected examples, see: (a) Mantovani, A. C.; Hernandez, J. G.; Bolm, C. Eur. J. Org. Chem. 2018, 2018, 2458. (b) Warner, A. J.; Churn, A.; McGough, J. S.; Ingleson, M. J. Angew. Chem., Int. Ed. 2017, 56, 354. (c) Torigoe, T.; Ohmura, T.; Suginome, M. Chem. Eur. J. 2016, 22, 10415. (d) Perrin, F. G.; Kiefer, G.; Jeanbourquin, L.; Racine, S.; Perrotta, D.; Waser, J.; Scopelliti, R.; Severin, K. Angew. Chem., Int. Ed. 2015, 54, 13393. (e) Yue, D.; Yao, T.; Larock, R. C. J. Org. Chem. 2005, 70, 10292. (12) For selected examples, see: (a) Yan, J.; Xu, J.; Zhou, Y.; Chen, J.; Song, Q. Org. Chem. Front. 2018, 5, 1483. (b) Li, H.; An, C.; Wu, G.; Li, G.; Huang, X.; Gao, W.; Ding, J.; Zhou, Y.; Liu, M.; Wu, H. Org. Lett. 2018, 20, 5573. (c) Tambe, S. D.; Jadhav, M. S.; Rohokale, R. S.; Kshirsagar, U. A. Eur. J. Org. Chem. 2018, 2018, 4867. (d) Alcaide, B.; Almendros, P.; Busto, E.; Herrera, F.; Lázaro-Milla, C.; Luna, A. Adv. Synth. Catal. 2017, 359, 2640. (e) Xu, J.; Yu, X.; Yan, J.; Song, Q. Org. Lett. 2017, 19, 6292. (f) Danilkina, N. A.; Kulyashova, A. E.; Khlebnikov, A. F.; Brase, S.; Balova, I. A. J. Org. Chem. 2014, 79, 9018. (g) Cho, C. H.; Jung, D. I.; Neuenswander, B.; Larock, R. C. ACS Comb. Sci. 2011, 13, 501. (h) Mehta, S.; Larock, R. C. J. Org. Chem. 2010, 75, 1652. (i) Wimmer, A.; König, B. Beilstein J. Org. Chem. 2018, 14, 54. (13) For selected examples, see: (a) Zheng, D.; Yu, J.; Wu, J. Angew. Chem., Int. Ed. 2016, 55, 11925. (b) Zhou, K.; Xia, H.; Wu, J. Org. Chem. Front. 2017, 4, 1121. (c) Zheng, D.; Mao, R.; Li, Z.; Wu, J. Org. Chem. Front. 2016, 3, 359. (d) Li, Y.; Zheng, D.; Li, Z.; Wu, J. Org. Chem. Front. 2016, 3, 574. (e) Yu, J.; Mao, R.; Wang, Q.; Wu, J. Org. Chem. Front. 2017, 4, 617. (f) Liu, T.; Zheng, D.; Wu, J. Org. Chem. Front. 2017, 4, 1079. (g) Mao, R.; Zheng, D.; Xia, H.; Wu, J. Org. Chem. Front. 2016, 3, 693. (h) Zhou, K.; Xia, H.; Wu, J. Org. Chem. Front. 2016, 3, 865. (i) Zheng, D.; Chen, M.; Yao, L.; Wu, J. Org. Chem. Front. 2016, 3, 985. (j) Zheng, D.; An, Y.; Li, Z.; Wu, J. Angew. Chem., Int. Ed. 2014, 53, 2451. (k) Gong, X.; Chen, J.; Li, X.; Xie, W.; Wu, J. Chem. - Asian J. 2018, 13, 2543. (l) Wang, X.; Li, Y.; Qiu, G.; Wu, J. Org. Chem. Front. 2018, 5, 2555. (m) Zhou, K.; Chen, M.; Yao, L.; Wu, J. Org. Chem. Front. 2018, 5, 371. (n) Zhang, J.; Zhou, K.; Wu, J. Org. Chem. Front. 2018, 5, 813. (14) For reviews: (a) Bisseret, P.; Blanchard, N. Org. Biomol. Chem. 2013, 11, 5393. (b) Deeming, A. S.; Emmett, E. J.; Richards-Taylor, C. S.; Willis, M. C. Synthesis 2014, 46, 2701. (c) Liu, G.; Fan, C.; Wu, J. Org. Biomol. Chem. 2015, 13, 1592. (d) Emmett, E. J.; Willis, M. C. Asian J. Org. Chem. 2015, 4, 602. (e) Qiu, G.; Zhou, K.; Gao, L.; Wu, J. Org. Chem. Front. 2018, 5, 691. (f) Hofman, K.; Liu, N.; Manolikakes, G. Chem. - Eur. J. 2018, 24, 11852. (g) Zheng, D.; Wu, J. Sulfur Dioxide Insertion Reactions for Organic Synthesis; Nature Springer: Berlin, 2017. (h) Qiu, G.; Lai, L.; Cheng, J.; Wu, J. Chem. Commun. 2018, 54, 10405. (i) Qiu, G.; Zhou, K.; Wu, J. Chem. Commun. 2018, 54, 12561. (15) (a) Ye, S.; Wu, J. Chem. Commun. 2012, 48, 10037. (b) Wang, M.; Chen, S.; Jiang, X. Org. Lett. 2017, 19, 4916. (c) Johnson, M. W.;
ASSOCIATED CONTENT
S Supporting Information *
The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.orglett.9b00100. Experimental procedures, characterization data, copies of 1 H and 13C NMR spectra of products (PDF) Accession Codes
CCDC 1881727 contains the supplementary crystallographic data for this paper. These data can be obtained free of charge via www.ccdc.cam.ac.uk/data_request/cif, or by emailing
[email protected], or by contacting The Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: +44 1223 336033.
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AUTHOR INFORMATION
Corresponding Authors
*E-mail:
[email protected] (J.W.). *E-mail:
[email protected] (S.Y.). ORCID
Jie Wu: 0000-0002-0967-6360 Notes
The authors declare no competing financial interest.
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ACKNOWLEDGMENTS Financial support from National Natural Science Foundation of China (Nos. 21871053 and 21532001) is gratefully acknowledged.
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REFERENCES
(1) (a) Kou, Y.; Koag, M. C.; Lee, S. J. Am. Chem. Soc. 2015, 137, 14067. (b) Al-Mestarihi, A. H.; Villamizar, G.; Fernandez, J.; Zolova, O. E.; Lombo, F.; Garneau-Tsodikova, S. J. Am. Chem. Soc. 2014, 136, 17350. (c) Schonherr, H.; Cernak, T. Angew. Chem., Int. Ed. 2013, 52, 12256. (d) Islam, K.; Bothwell, I.; Chen, Y.; Sengelaub, C.; Wang, R.; Deng, H.; Luo, M. J. Am. Chem. Soc. 2012, 134, 5909. (e) Barreiro, E. J.; Kummerle, A. E.; Fraga, C. A. Chem. Rev. 2011, 111, 5215. (2) McGrath, N. A.; Brichacek, M.; Njardarson, J. T. J. Chem. Educ. 2010, 87, 1348. (3) For selected reviews, see: Dai, Q.; Jiang, Y.; Yu, J.; Cheng, J. Synthesis 2016, 48, 329. (b) Yan, G.; Borah, A. J.; Wang, L.; Yang, M. Adv. Synth. Catal. 2015, 357, 1333. (4) For selected recent examples on the methylation from methyl halides, see: (a) Wang, J.; Zhao, J.; Gong, H. Chem. Commun. 2017, 53, 10180. (b) Liu, W.; Cera, G.; Oliveira, J. C. A.; Shen, Z.; Ackermann, L. Chem. - Eur. J. 2017, 23, 11524. (c) Hu, L.; Liu, X.; Liao, X. Angew. Chem., Int. Ed. 2016, 55, 9743. (d) Liang, Z.; Xue, W.; Lin, K.; Gong, H. Org. Lett. 2014, 16, 5620. (5) For selected recent examples on the methylation from methylboronic reagents, see: (a) Chen, X.; Sorensen, E. J. J. Am. Chem. Soc. 2018, 140, 2789. (b) Thuy-Boun, P. S.; Villa, G.; Dang, D.; Richardson, P.; Su, S.; Yu, J. J. Am. Chem. Soc. 2013, 135, 17508. (c) Neufeldt, S. R.; Seigerman, C. K.; Sanford, M. S. Org. Lett. 2013, 15, 2302. (6) For selected recent examples on the methylation from organometallic reagents, see: (a) Sun, Q.; Yoshikai, N. Org. Chem. Front. 2018, 5, 2214. (b) Wang, H.; Zhang, S.; Wang, Z.; He, M.; Xu, K. Org. Lett. 2016, 18, 5628. (c) Shang, R.; Ilies, L.; Nakamura, E. J. Am. Chem. Soc. 2015, 137, 7660. (d) Graczyk, K.; Haven, T.; Ackermann, L. Chem. - Eur. J. 2015, 21, 8812. (7) For selected examples, see: (a) Zhu, N.; Zhao, J.; Bao, H. Chem. Sci. 2017, 8, 2081. (b) Zhang, P.; Li, J.; Zhang, L.; Shoberu, A.; Zou, D
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Organic Letters Bagley, S. W.; Mankad, N. P.; Bergman, R. G.; Mascitti, V.; Toste, F. D. Angew. Chem., Int. Ed. 2014, 53, 4404. (d) Wang, Y.; Du, B.; Sha, W.; Han, J.; Pan, Y. Org. Chem. Front. 2017, 4, 1313. (e) Zhang, J.; An, Y.; Wu, J. Chem. - Eur. J. 2017, 23, 9477. (f) Shavnya, A.; Hesp, K. D.; Mascitti, V.; Smith, A. C. Angew. Chem., Int. Ed. 2015, 54, 13571. (g) Konishi, H.; Tanaka, H.; Manabe, K. Org. Lett. 2017, 19, 1578. (h) Gong, X.; Chen, J.; Lai, L.; Cheng, J.; Sun, J.; Wu, J. Chem. Commun. 2018, 54, 11172. (i) Liu, N.; Liang, S.; Manolikakes, G. Adv. Synth. Catal. 2017, 359, 1308. (j) Zhou, K.; Zhang, J.; Qiu, G.; Wu, J. Org. Lett. 2019, 21, 275. (k) Zhang, J.; Zhou, K.; Qiu, G.; Wu, J. Org. Chem. Front. 2019, 6, 36. (l) Liao, H.; Chatupheeraphat, A.; Hsiao, C. C.; Atodiresei, I.; Rueping, M. Angew. Chem., Int. Ed. 2015, 54, 15540. (m) Wang, J. M.; Fan, Q.; Jiang, X. Green Chem. 2018, 20, 5469. (16) Santos, P. S.; Mello, M. T. S. J. Mol. Struct. 1988, 178, 121. (17) For selected examples, see: (a) Nguyen, B.; Emmett, E. J.; Willis, M. C. J. Am. Chem. Soc. 2010, 132, 16372. (b) Liu, F.; Wang, J.; Zhou, P.; Li, G.; Hao, W.; Tu, S.; Jiang, B. Angew. Chem., Int. Ed. 2017, 56, 15570. (c) Sheng, J.; Li, Y.; Qiu, G. Org. Chem. Front. 2017, 4, 95. (d) Sun, K.; Shi, Z.; Liu, Z.; Luan, B.; Zhu, J.; Xue, Y. Org. Lett. 2018, 20, 6687. (e) Wang, X.; Xue, L.; Wang, Z. Org. Lett. 2014, 16, 4056. (f) Wang, H.; Sun, S.; Cheng, J. Org. Lett. 2017, 19, 5844. (g) Gong, X.; Chen, J.; Li, X.; Xie, W.; Wu, J. Chem. - Asian J. 2018, 13, 2543. (h) Chen, C. C.; Waser, J. Org. Lett. 2015, 17, 736. (i) Tsai, A. S.; Curto, J. M.; Rocke, B. N.; Dechert-Schmitt, A. R.; Ingle, G. K.; Mascitti, V. Org. Lett. 2016, 18, 508. (j) Chen, Y.; Murray, P. R. D.; Davies, A. T.; Willis, M. C. J. Am. Chem. Soc. 2018, 140, 8781. (k) Wang, Y.; Deng, L.; Zhou, J.; Wang, X.; Mei, H.; Han, J.; Pan, Y. Adv. Synth. Catal. 2018, 360, 1060. (l) Wang, Y.; Deng, L.; Deng, Y.; Han, J. J. Org. Chem. 2018, 83, 4674. (m) Sun, D.; Yin, K.; Zhang, R. Chem. Commun. 2018, 54, 1335. (n) Vedovato, V.; Talbot, E. P. A.; Willis, M. C. Org. Lett. 2018, 20, 5493. (o) Yang, D.; Sun, P.; Wei, W.; Liu, F.; Zhang, H.; Wang, H. Chem. - Eur. J. 2018, 24, 4423. (p) Wang, H.; Wang, B.; Sun, S.; Cheng, J. Org. Chem. Front. 2018, 5, 2547.
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DOI: 10.1021/acs.orglett.9b00100 Org. Lett. XXXX, XXX, XXX−XXX
