Oxidative

Letter Cite This: Org. Lett. XXXX, XXX, XXX−XXX

pubs.acs.org/OrgLett

Visible-Light-Induced Oxidation/[3 + 2] Cycloaddition/Oxidative Aromatization to Construct Benzo[a]carbazoles from 1,2,3,4Tetrahydronaphthalene and Arylhydrazine Hydrochlorides Jiaxuan Shen,* Nannan Li, Yanjiang Yu, and Chunhua Ma*

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Collaborative Innovation Center of Henan Province for Green Manufacturing of Fine Chemicals, Key Laboratory of Green Chemical Media and Reactions, Ministry of Education, School of Chemistry and Chemical Engineering, Henan Normal University, Xinxiang, Henan 453007, China S Supporting Information *

ABSTRACT: An efficient synthesis of benzo[a]carbazoles via visible-light-induced tandem oxidation/[3 + 2] cycloaddition/ oxidative aromatization reactions was reported. The benzylic C(sp3)−H of tetrahydronaphthalene was activated through visiblelight photoredox catalyst with oxygen as the clean oxidant under mild reaction conditions. This protocol proceeds efficiently with broad substrate scope, and the mechanism study was performed.

B

more, the C−H amination strategy for B[a]Cs synthesis using 2-nitrobiaryls, 2-aminebiaryls, and α-azidobiaryls as the substrates was also developed.8 However, most of these reactions needed harsh reactions or complex substrates, so it is still highly desirable to explore new green and mild conditions to fit with the diverse structural features of B[a]Cs with commercially available substrates. Since 2008, visible-light photoredox catalysis has been widely used in organic synthesis under very mild and clean conditions.9 The photoinduced intramolecular cyclizations for the synthesis of B[a]Cs have also been developed.10 The Protti and Palmieri groups developed the photochemical synthesis of B[a]Cs from 2-aryl-3-(1-tosylalky)indoles with irradiated phosphor-coated lamps (366 nm) (Scheme 2, a).10a Yu and coworkers reported two efficient approaches for constructing 5-hydroxy-benzo[a]carbazoles by employing the photoinduced intramolecular C−H insertion of 2-aryl-3-(α-diazocarbonyl)indoles and ethyl 3-(1-methy-1H-indol-3-yl)-3-oxopropanoates (Scheme 2, b and c).10b,c Among the various strategies reported for the synthesis of B[a]Cs, a direct convergent synthesis from easily available reagents is especially attractive.5b,7a,b,m More recently, visible-light photoredox catalytic activation of benzylic C(sp3)−H bonds represents a green and sustainable process.11−13 Herein, we report a photocatalytic tandem oxidation/[3 + 2] cycloaddition/oxidative aromatiza-

enzo[a]carbazole (B[a]Cs) structural motifs are frequently present in a variety of biologically active molecules and functional organic materials.1−3 For example, compound I and compound II exhibit antitumor activity against various tumor cell lines (Scheme 1).1d,f Compound III was applied in the field of materials chemistry because of its optical character.2 Compound IV was utilized in organic lightemitting diodes (OLEDs).3 Due to their importance, a large number of methods for the synthesis of B[a]Cs have been developed.4 Initially, the classic B[a]Cs synthesis mainly relies on the Fischer−Borsche indolization.5 Recently, B[a]Cs synthesis based on metalcatalyzed reactions employing prefunctionalized benzynes or indole derivatives has recently been demonstrated.6,7 FutherScheme 1. Some Important Benzo[a]carbazole Derivatives

Received: August 18, 2019

© XXXX American Chemical Society

A

DOI: 10.1021/acs.orglett.9b02939 Org. Lett. XXXX, XXX, XXX−XXX

Letter

Organic Letters Table 1. Optimization of the Reaction Conditionsa

Scheme 2. Photoinduced Synthesis of Benzo[a]carbazoles

entry 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16c 17 18d 19 20e

tion sequence to construct B[a]Cs from 1,2,3,4-tetrahydronaphthalene and arylhydrazine hydrochlorides using molecular oxygen as a green oxidant under mild conditions (Scheme 2, d). Initially, tetrahydronaphthalene (1a) and phenylhydrazine hydrochloride (2a) were chosen as model substrates to optimize the reaction conditions (Table 1). We were pleased to find that using 9-mesityl-10-methylacridinium perchlorate (PC-1) as a photoredox catalyst, which had already been used in several oxidative benzylic C(sp3)−H activations12 and dehydrogenations of tetrahydronaphthalenes,14 HCl as the acid, and O2 as the terminal oxidant in CH3CN under 3 W blue LED irradiation for 24 h, 11H-benzo[a]carbazole (3a) was obtained in 18% yield (entry 1). Evaluation of different acids showed that HCl is the best acid for this process (entries 2−4). The reaction proceeded less efficiently in other solvents, including H2O, EtOH, THF, DMSO, and DCM (entries 5−9). To our delight, CH3CN/H2O (V:V = 2:1) gave better results than CH3CN (entry 10), probably because phenylhydrazine hydrochloride can dissolve well in this cosolvent mixture. Other photocatalysts such as 10-(3,5-dimethoxyphenyl)-9mesityl-1,3,6,8-tetramethoxyacridin-10-ium tetrafluoroborate (PC-2), 2,4,6-triphenylpyrylium tetrafluoroborate (PC-3), and Ru(bpy)3Cl2·6H2O (PC-4) did not increase the yield of the desired product (entries 11−13). When 10-phenyl-9(2,4,6-trimethylphenyl) acridinium tetrafluoroborate (PC-5) was used as the catalyst, the yield increased by a small amount (entry 14). Increasing the catalyst loading to 8 mol %, the yield of 3a could be improved to 46% (entry 15). Finally, increasing the reaction time from 24 to 48 h afforded 3a in a yield of 75% (entry 16). Control experiments showed that in the absence of photocatalyst (entry 17), O2 (entry 18), HCl (entry 19), or light (entry 20) gave no desired product (for a complete list of conditions, see the Supporting Information). With the optimized reaction conditions in hand, the scope and the generality of this reaction were explored. First, with tetrahydronaphthalene (1a) as a model substrate, several substituted phenylhydrazine hydrochlorides (2) were explored, and the results were presented in Scheme 3. In general, the reaction with phenylhydrazines bearing electron-donating

catalyst (x mol %) PC-1 PC-1 PC-1 PC-1 PC-1 PC-1 PC-1 PC-1 PC-1 PC-1 PC-2 PC-3 PC-4 PC-5 PC-5 PC-5 PC-5 PC-5 PC-5

(3) (3) (3) (3) (3) (3) (3) (3) (3) (3) (3) (3) (3) (3) (8) (8) (8) (8) (8)

acid HCl TFA TsOH AcOH HCl HCl HCl HCl HCl HCl HCl HCl HCl HCl HCl HCl HCl HCl HCl

yield (%)b

solvent CH3CN CH3CN CH3CN CH3CN H2O EtOH THF DMSO DCM CH3CN/H2O CH3CN/H2O CH3CN/H2O CH3CN/H2O CH3CN/H2O CH3CN/H2O CH3CN/H2O CH3CN/H2O CH3CN/H2O CH3CN/H2O CH3CN/H2O

(2:1) (2:1) (2:1) (2:1) (2:1) (2:1) (2:1) (2:1) (2:1) (2:1) (2:1)

18 10 trace trace trace 12 trace trace trace 30 trace 14 trace 32 46 75 -

a

Reaction conditions: 1a (0.2 mmol), 2a (0.3 mmol), photocatalyst (x mol %), HCl (37% aq.), O2 (balloon), solvent (1.0 mL), 3W blue LEDs for 24 h. bIsolated yield. c48 h. dN2. eIn the dark.

Scheme 3. Scope of Phenylhydrazine Hydrochlorides

a

Reaction conditions: 1a (0.2 mmol), 2 (0.3 mmol), PC-5 (8 mol %), HCl (37% aq., 5 equiv), O2 (balloon), CH3CN/H2O (2/1, 1.0 mL), 3 W blue LEDs for 48 h. B

DOI: 10.1021/acs.orglett.9b02939 Org. Lett. XXXX, XXX, XXX−XXX

Letter

Organic Letters groups such as methyl, ethyl, isopropyl, and t-butyl were well tolerated under the optimal reaction conditions (3b−3g, 52− 78% yield). Notably, the substrates containing halogen, such as fluorine, chloride, or bromide on the aromatic ring, also provided desired products in moderate to good yields (3h−3l, 48−62% yield), providing the potential chance for further chemical transformation. The meta-Br-substituted phenylhydrazine resulted in a low yield (3m, 35% yield). In addition, when 4-OCF3-phenylhydrazine was employed in the reaction, the desired product 3n was also obtained in 48% yield. It was noted that the disubstituted phenylhydrazines containing two methyl or fluorine groups also could undergo this process well and furnish the target products 3o−3r. A mixture of isomers was obtained in 80% combination yield when 3-methylphenylhydrazine was used (3s and 3s′, C1:C2 = 1:1.4). However, no desired product was obtained when electron-withdrawing groups, such as NO2 or CF3, were present on the para-position of the aromatic ring. A possible reason is that the presence of strongly deactivating groups precludes efficient Fischer [3 + 2] cyclization.15 Next, the reactions of different substituted tetrahydronaphthalenes were studied. The substrates containing halogen on the aromatic ring were well tolerated, and the desired products 4 were obtained in moderate yields (Scheme 4, 4a−4f, 45−

morpholine, could afford the desired product 4 (Scheme 4, 4i−4t, 30−56% yield). To demonstrate the utility of our methodology, the gramscale synthesis and synthetic application were performed (Scheme 5). Benzo[a]carbazole 3a was obtained in moderate Scheme 5. Gram-Scale Synthesis and Synthetic Application

yield at the 5 mmol scale (55% yield) (Scheme 5, a). This result provides a possibility for the usage of preparative synthesis. Furthermore, the desired anticancer activity compounds 4u and 4v were successfully obtained in 50% and 59% yields (Scheme 5, b). Notably, the previously reported synthesis of 4u from 2-(4-bromophenyl)acetic acid required 12 steps.1d In contrast, using our strategy, 4u was elegantly constructed in only three steps from 1,2,3,4tetrahydronaphthalene-1-carboxylic acid (48% overall yield) (Scheme 5, c). To gain some insight into the mechanism, we then performed a series of control experiments (Scheme 6). Upon addition of 2.0 equiv of radical trapping agent TEMPO or BHT, the reaction was completely inhibited, which indicates the reaction may proceed through a radical pathway. We used cyclohexane (5) instead of 1a to perform the reactions, and there was no reaction occurring (Scheme 6, 2). When tetrahydronaphthalene (1a) was added independently under the standard conditions, 3,4-dihydronaphthalen-1(2H)-one (7) was obtained in 60% yield (Scheme 6, 3). We used 3,4dihydronaphthalen-1(2H)-one (7) instead of 1a to perform the reactions. The desired product 3a was obtained with 52% yield, and 28% of 6,11-dihydro-5H-benzo[a]carbazole (8) was detected (Scheme 6, 4). However, when cyclohexanone (9) was used in the optimized conditions, only 2,3,4,9-tetrahydro1H-carbazole (10) was obtained, and 9H-carbazole (6) was not detected (Scheme 6, 5). Meanwhile, when 8 was used to replace 1a and 2a to perform the photoredox-catalyzed reaction, we obtained 3a with 69% yield (Scheme 6, 6). Based on our studies and the literature report,12 a plausible mechanism is proposed in Scheme 7. The photocatalyst is excited by visible-light irradiation to generate [acridinium catalyst]*, which then undergoes a single electron transfer (SET) process with the benzylic C(sp3)−H compound to generate radical cation A and the [acridinium catalyst] radical anion. The [acridinium catalyst] radical anion can be oxidized by O2 to finish the photocatalytic cycle. The generated radical cation A loses one proton to generate the radical B, followed by the reaction with O2 or the O2 radical anion to generate the

Scheme 4. Scope of Tetrahydronaphthalenesa

a

Reaction conditions: 1 (0.2 mmol), 2a (0.3 mmol), PC-5 (8 mol %), HCl (37% aq., 5 equiv), O2 (balloon), CH3CN/H2O (2/1, 1.0 mL), 3 W blue LEDs for 48 h.

56% yield). It is worth noting that the structure of 4c was unambiguously determined by X-ray diffraction analysis (see the Supporting Information). In addition, 6-CF3-tetrahydronaphthalene and 6-phenyl-tetrahydronaphthalene were also suitable for this reaction to give 4g and 4h in 48% and 28% yields. Moreover, 1-substituted tetrahydronaphthalene, including methyl, ethyl, aryl, amide, pyrrolidine, piperidine, and C

DOI: 10.1021/acs.orglett.9b02939 Org. Lett. XXXX, XXX, XXX−XXX

Organic Letters

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Scheme 6. Control Experiments

Letter

ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.orglett.9b02939. Experimental details, compound characterization data, and NMR spectra (PDF) Accession Codes

CCDC 1920539 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]. *E-mail: [email protected]. ORCID

Jiaxuan Shen: 0000-0002-3113-973X Notes

The authors declare no competing financial interest.

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Scheme 7. Proposed Mechanism

ACKNOWLEDGMENTS We would like to thank Dr. Dachang Bai (HTU) for his assistance with this article. This work was supported by the High-end Foreign Expert Project (GDW20186300346), He’nan Province Natural Science Foundation (162300410182), the Foundation of He’nan Educational Committee (17A350008), and the Doctoral Scientific Research Foundation of He’nan Normal University.

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REFERENCES

(1) (a) Conchon, E.; Anizon, F.; Aboab, B.; Golsteyn, R. M.; Leonce, S.; Pfeiffer, B.; Prudhomme, M. Bioorg. Med. Chem. 2008, 16, 4419. (b) Routier, S.; Merour, J. Y.; Dias, N.; Lansiaux, A.; Bailly, C.; Lozach, O.; Meijer, L. J. Med. Chem. 2006, 49, 789. (c) Conchon, E.; Anizon, F.; Aboab, B.; Prudhomme, M. J. Med. Chem. 2007, 50, 4669. (d) Wang, Y.-Q.; Li, X.-H.; He, Q.; Chen, Y.; Xie, Y.-Y.; Ding, J.; Miao, Z.-H.; Yang, C.-H. Eur. J. Med. Chem. 2011, 46, 5878. (e) Segall, A.; Pappa, H.; Casaubon, R.; Martin, G.; Bergoc, R.; Pizzorno, M. T. Eur. J. Med. Chem. 1995, 30, 165. (f) Von Angerer, E.; Prekajac, J. J. Med. Chem. 1986, 29, 380. (2) (a) Paramasivam, M.; Chitumalla, R. K.; Singh, S. P.; Islam, A.; Han, L.; Rao, V. J.; Bhanuprakash, K. J. Phys. Chem. C 2015, 119, 17053. (b) Qian, X.; Zhu, Y.-Z.; Chang, W.-Y.; Song, J.; Pan, B.; Lu, L.; Gao, H.-H.; Zheng, J.-Y. ACS Appl. Mater. Interfaces 2015, 7, 9015. (c) Oliveira, M. M.; Salvador, M. A.; Coelho, P. J.; Carvalho, L. M. Tetrahedron 2005, 61, 1681. (d) Li, J.; Grimsdale, A. C. Chem. Soc. Rev. 2010, 39, 2399. (e) Moon, I. K.; Oh, J.-W.; Kim, N. J. J. Photochem. Photobiol., A 2008, 194, 351. (3) (a) Chen, J. P.; Tanabe, H.; Li, X.-C.; Thoms, T.; Okamura, Y.; Ueno, K. Synth. Met. 2003, 132, 173. (b) Schmidbauer, S.; Hohenleutner, A.; Koenig, B. Adv. Mater. 2013, 25, 2114. (4) (a) Schmidt, A. W.; Reddy, K. R.; Knölker, H.-J. Chem. Rev. 2012, 112, 3193. (b) Knölker, H.-J.; Reddy, K. R. Chem. Rev. 2002, 102, 4303. (5) (a) Dufour, F.; Kirsch, G. Synlett 2006, 7, 1021. (b) Xiao, F.; Liao, Y.; Wu, M.; Deng, G.-J. Green Chem. 2012, 14, 3277. (6) (a) Chen, C.-C.; Chin, L.-Y.; Yang, S.-C.; Wu, M.-J. Org. Lett. 2010, 12, 5652. (b) Hirano, K.; Inaba, Y.; Watanabe, T.; Oishi, S.;

hydroperoxidate intermediate C, which can lose one water and be transformed into the ketone 7. The ketone 7 then undergoes [3 + 2] cycloaddition reactions with phenylhydrazine hydrochloride (2a) to produce 6,11-dihydro-5Hbenzo[a]carbazole (8). The final oxidative aromatization in the presence of O2 will accomplish the synthesis of benzo[a]carbazole 3a under photo-oxidative conditions. In conclusion, we have developed an efficient method for the synthesis of benzo[a]carbazoles via visible-light-induced direct benzylic C(sp3)−H activation from tetrahydronaphthalene and arylhydrazine hydrochlorides. This method is simple and efficient under mild and metal-free conditions via the tandem oxidation/[3 + 2] cycloaddition/oxidative aromatization sequence using O2 as the oxidant. In addition, this protocol proceeds well to afford biologically active compounds and can be performed on a gram scale. Future studies for the synthesis of other nitrogen-containing heterocycles via visible-lightinduced reactions are currently underway in our laboratory. D

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Organic Letters Fujii, N.; Ohno, H. Adv. Synth. Catal. 2010, 352, 368. (c) Nanjo, T.; Tsukano, C.; Takemoto, Y. Org. Lett. 2012, 14, 4270. (d) Guo, S.; Yuan, K.; Gu, M.; Lin, A.; Yao, H. Org. Lett. 2016, 18, 5236. (e) Jash, M.; Das, B.; Chowdhury, C. J. Org. Chem. 2016, 81, 10987. (f) Li, N.; Lian, X.-L.; Li, Y.-H.; Wang, T.-Y.; Han, Z.-Y.; Zhang, L.; Gong, L.-Z. Org. Lett. 2016, 18, 4178. (g) Peng, X.; Zhu, L.; Hou, Y.; Pang, Y.; Li, Y.; Fu, J.; Yang, L.; Lin, B.; Liu, Y.; Cheng, M. Org. Lett. 2017, 19, 3402. (7) (a) Tsuchimoto, T.; Matsubayashi, H.; Kaneko, M.; Nagase, Y.; Miyamura, T.; Shirakawa, E. J. Am. Chem. Soc. 2008, 130, 15823. (b) Shi, Z.; Ding, S.; Cui, Y.; Jiao, N. Angew. Chem., Int. Ed. 2009, 48, 7895. (c) Kianmehr, E.; Ghanbari, M. Eur. J. Org. Chem. 2012, 2012, 256. (d) Tao, Y.; Zhang, F.; Tang, C.-Y.; Wu, X.-Y.; Sha, F. Asian J. Org. Chem. 2014, 3, 1292. (e) Huang, J.-R.; Qin, L.; Zhu, Y.-Q.; Song, Q.; Dong, L. Chem. Commun. 2015, 51, 2844. (f) Wu, L.; Huang, H.; Dang, P.; Liang, Y.; Pi, S. RSC Adv. 2015, 5, 64354. (g) Kuo, C.-W.; Konala, A.; Lin, L.; Chiang, T.-T.; Huang, C.-Y.; Yang, T.-H.; Kavala, V.; Yao, C.-F. Chem. Commun. 2016, 52, 7870. (h) Ngo, T. N.; Dang, T. T.; Villinger, A.; Langer, P. Adv. Synth. Catal. 2016, 358, 1328. (i) Truax, N. J.; Mejia, F. B.; Kwansare, D. O.; Lafferty, M. M.; Kean, M. H.; Pelkey, E. T. J. Org. Chem. 2016, 81, 6808. (j) Li, B.; Zhang, B.; Zhang, X.; Fan, X. Chem. Commun. 2017, 53, 1297. (k) Zhang, Z.; Liu, K.; Chen, X.; Su, S.-J.; Deng, Y.; Zeng, W. RSC Adv. 2017, 7, 30554. (l) Chen, G.; Zhang, X.; Jia, R.; Li, B.; Fan, X. Adv. Synth. Catal. 2018, 360, 3781. (m) Kripalaya Ratheesh, A.; Sparkes, H. A.; Prasad, K. J. R. Org. Biomol. Chem. 2018, 16, 2527. (n) Ni, P.; Tan, J.; Zhao, W.; Huang, H.; Xiao, F.; Deng, G.-J. Org. Lett. 2019, 21, 3687. (8) (a) Gao, H. Y.; Xu, Q. L.; Yousufuddin, M.; Ess, D. H.; Kürti, L. Angew. Chem., Int. Ed. 2014, 53, 2701. (b) Alt, I. T.; Plietker, B. Angew. Chem., Int. Ed. 2016, 55, 1519. (9) For selected reviews, see: (a) Narayanam, J. M. R.; Stephenson, C. R. J. Chem. Soc. Rev. 2011, 40, 102. (b) Lang, X.; Zhao, J.; Chen, X. Chem. Soc. Rev. 2016, 45, 3026. (c) Skubi, K. L.; Blum, T. R.; Yoon, T. P. Chem. Rev. 2016, 116, 10035. (d) Lee, K. N.; Ngai, M.-Y. Chem. Commun. 2017, 53, 13093. (e) Xie, J.; Jin, H.; Hashmi, A. S. K. Chem. Soc. Rev. 2017, 46, 5193. (f) Chen, Y.; Lu, L.-Q.; Yu, D.-G.; Zhu, C.J.; Xiao, W.-J. Sci. China: Chem. 2019, 62, 24. (g) Milligan, J. A.; Phelan, J. P.; Badir, S. O.; Molander, G. A. Angew. Chem., Int. Ed. 2019, 58, 6152. (h) Raviola, C.; Protti, S.; Ravelli, D.; Fagnoni, M. Green Chem. 2019, 21, 748. (10) (a) Protti, S.; Palmieri, A.; Petrini, M.; Fagnoni, M.; Ballini, R.; Albinia, A. Adv. Synth. Catal. 2013, 355, 643. (b) Yang, J.; Zhang, Q.; Zhang, W.; Yu, W. RSC Adv. 2014, 4, 13704. (c) Li, Y.; Pang, Z.; Zhang, T.; Yang, J.; Yu, W. Tetrahedron 2015, 71, 3351. (d) ParisienCollette, S.; Cruché, C.; Abel-Snape, X.; Collins, S. K. Green Chem. 2017, 19, 4798. (11) (a) Tsuchimoto, T.; Matsubayashi, H.; Kaneko, M.; Nagase, Y.; Miyamura, T.; Shirakawa, E. J. Am. Chem. Soc. 2008, 130, 15823. (b) Zou, Y.-Q.; Lu, L.-Q.; Fu, L.; Chang, N.-J.; Rong, J.; Chen, J.-R.; Xiao, W.-J. Angew. Chem., Int. Ed. 2011, 50, 7171. (c) To, W.-P.; Tong, G. S.-M.; Lu, W.; Ma, C.; Liu, J.; Chow, A. L.-F.; Che, C.-M. Angew. Chem., Int. Ed. 2012, 51, 2654. (d) Zhao, G.; Yang, C.; Guo, L.; Sun, H.; Chen, C.; Xia, W. Chem. Commun. 2012, 48, 2337. (e) Meng, Q.-Y.; Zhong, J.-J.; Liu, Q.; Gao, X.-W.; Zhang, H.-H.; Lei, T.; Li, Z.-J.; Feng, K.; Chen, B.; Tung, C.-H.; Wu, L.-Z. J. Am. Chem. Soc. 2013, 135, 19052. (f) Xie, J.; Xue, Q.; Jin, H.; Li, H.; Cheng, Y.; Zhu, C. Chem. Sci. 2013, 4, 1281. (g) Liu, X.; Ye, X.; Bureš, F.; Liu, H.; Jiang, Z. Angew. Chem., Int. Ed. 2015, 54, 11443. (h) Dutta, B.; Sharma, V.; Sassu, N.; Dang, Y.; Weerakkody, C.; Macharia, J.; Miao, R.; Howella, A. R.; Suib, S. L. Green Chem. 2017, 19, 5350. (i) Yang, Q.; Zhang, L.; Ye, C.; Luo, S.; Wu, L.-Z.; Tung, C.-H. Angew. Chem., Int. Ed. 2017, 56, 3694. (j) Zhou, W.-J.; Cao, G.-M.; Shen, G.; Zhu, X.-Y.; Gui, Y.-Y.; Ye, J.-H.; Sun, L.; Liao, L.-L.; Li, J.; Yu, D.-G. Angew. Chem., Int. Ed. 2017, 56, 15683. (k) Ide, T.; Barham, J. P.; Fujita, M.; Kawato, Y.; Egami, H.; Hamashima, Y. Chem, Sci. 2018, 9, 8453. (l) Zhao, Y.; Jin, J.; Chan, P. W. H. Adv. Synth. Catal. 2019, 361, 1313. (12) (a) Ohkubo, K.; Mizushima, K.; Iwata, R.; Souma, K.; Suzukib, N.; Fukuzumi, S. Chem. Commun. 2010, 46, 601. (b) Yamada, Y.;

Maeda, K.; Ohkubo, K.; Karlin, K. D.; Fukuzumi, S. Phys. Chem. Chem. Phys. 2012, 14, 9654. (c) Yi, H.; Bian, C.; Hu, X.; Niu, L.; Lei, A. Chem. Commun. 2015, 51, 14046. (d) Zhang, L.; Yi, H.; Wang, J.; Lei, A. Green Chem. 2016, 18, 5122. (13) (a) Pandey, G.; Pal, S.; Laha, R. Angew. Chem., Int. Ed. 2013, 52, 5146. (b) Xia, J.-B.; Zhu, C.; Chen, C. J. Am. Chem. Soc. 2013, 135, 17494. (c) Qvortrup, K.; Rankic, D. A.; MacMillan, D. W. C. J. Am. Chem. Soc. 2014, 136, 626. (d) Pandey, G.; Laha, R. Angew. Chem., Int. Ed. 2015, 54, 14875. (e) Pandey, G.; Laha, R.; Singh, D. J. Org. Chem. 2016, 81, 7161. (f) Li, G.-X.; Morales-Rivera, C. A.; Gao, F.; Wang, Y.; He, G.; Liu, P.; Chen, G. Chem. Sci. 2017, 8, 7180. (g) Liu, H.; Ma, L.; Zhou, R.; Chen, X.; Fang, W.; Wu, J. ACS Catal. 2018, 8, 6224. (h) Dewanji, A.; Krach, P. E.; Rueping, M. Angew. Chem., Int. Ed. 2019, 58, 3566. (14) Kato, S.; Saga, Y.; Kojima, M.; Fuse, H.; Matsunaga, S.; Fukatsu, A.; Kondo, M.; Masaoka, S.; Kanai, M. J. Am. Chem. Soc. 2017, 139, 2204. (15) (a) Wagaw, S.; Yang, B. H.; Buchwald, S. L. J. Am. Chem. Soc. 1998, 120, 6621. (b) Wagaw, S.; Yang, B. H.; Buchwald, S. L. J. Am. Chem. Soc. 1999, 121, 10251.

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