Hantzsch Ester-Mediated Benzannulation of Diazo Compounds under

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

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Hantzsch Ester-Mediated Benzannulation of Diazo Compounds under Visible Light Irradiation Savita B. Nagode,†,‡ Ruchir Kant,§ and Namrata Rastogi*,†,‡ †

Medicinal & Process Chemistry Division and §Molecular & Structural Biology Division, CSIR-Central Drug Research Institute, Sector 10, Jankipuram Extension, Sitapur Road, P.O. Box 173, Lucknow 226031, India ‡ Academy of Scientific and Innovative Research, New Delhi 110001, India

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S Supporting Information *

ABSTRACT: A metal-free benzannulation of diazo compounds under visible light irradiation was developed. The photocatalytic single electron transfer by Hantzsch ester to the diazo enolates results into enolate vinyl radicals, which were trapped by alkynes leading to functionalized naphthalene-1-ols. The enolate vinyl radicals were also trapped intramolecularly by o-aryl groups to access phenanthren-10-ols. The wide substrate scope and mild conditions employing inexpensive Hantzsch ester as photosensitizer are noteworthy attributes of the reaction.

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sensitizers. For instance, the Wolff rearrangement,8 several X−H insertion (X = C, O, N) reactions,9 cyclopropanation,9,10a and cyclopropenation reactions10b as well as cross coupling11 of free carbenes generated through blue light promoted photolysis of donor−acceptor diazoalkanes have been reported recently. However, generation of radical anion/cation species from diazo compounds photochemically would rationally require a suitable one electron reductant/oxidant following N2 extrusion. The single electron transfer process between an excited photocatalyst and diazo compounds is quite challenging due to other competitive reactions such as energy transfer, transient carbene generation, and chain reaction.12 To realize this goal, Zhou and co-workers generated enolated vinyl radical ions via single electron transfer (SET) from excited Ir-photocatalyst to diazoenolates.13 The enolate vinyl radical ions were trapped by terminal alkynes to afford carboxylated naphthols. The major drawback (other than long reaction time and limited substrate scope) of this otherwise elegant synthetic strategy is the use of metal photocatalyst, which defeats the very objective of developing “greener” reactions under visible light catalysis. Our continued interest in developing metal-free synthetic strategies for phosphonylated heterocycles prompted us to explore the visible light-mediated benzannulation of diazophosphonates with alkynes under visible light catalysis. The highly negative irreversible reduction potential of α-diazophosphonate 1a (Ered = −1.25 V vs SCE in MeCN) calculated

he diazo compounds are undoubtedly one of the most potent classes of organic compounds in terms of their versatile reactivity profile.1 The diazo compound’s reactions can be broadly categorized into (i) reactions retaining diazo group and (ii) reactions involving loss of N2. The former category of diazo reactions usually proceed through acid/base catalyzed formation of diazo anion intermediate, for example, dipolar cycloadditions, nucleophilic additions/substitutions, Mannichtype reactions, aldol reactions, etc.2 However, the chemistry of diazo compounds has been dominated by the reactions entailing loss of N2 under thermal, photochemical, or catalytic conditions. The intermediate species can be a free carbene or a more stable metal carbenoid attributed to the diazo group’s tendency to donate electrons to the transition metals.3 These carbene/ carbenoids can undergo insertion reactions, [2 + 1]-cycloadditions, Wolff rearrangement, ylide formation, cross-coupling reactions, etc.4 Although, photochemical reactions of diazo compounds under UV irradiation have been known for a while,5 the chemistry of diazo compound’s under visible light catalysis gained momentum only recently. The metal−polypyridyl complexes or organic dyes are required as photosensitizers in the visible light photoredox catalyzed reactions of diazo compounds serving usually as nucleophiles or carbene precursors.6 Suero and co-workers generated diazomethyl radical from diazo group bearing hypervalent iodine substrates and Ru(bpy)3Cl2 photocatalyst under visible light activation and used it as carbyne equivalent due to its dual radical and carbene character.7 Further, there are few recent reports of low-energy visible light application to develop diazo compounds chemistry without employing photo© XXXX American Chemical Society

Received: June 20, 2019

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DOI: 10.1021/acs.orglett.9b02135 Org. Lett. XXXX, XXX, XXX−XXX

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reaction was found to be 1 equiv since a slight increase in product yield was noticed with 0.5 equiv of HE (entry 5), whereas a significant increase occurred with 1 equiv of HE (entry 6). Further, 0.5 equiv of additive provided the desired product in highest yield so far, i.e., 84% (entries 7, 8). Therefore, 1:2 ratio of substrates 1a and 2a in the presence of 1 equiv of HE and 0.5 equiv of TBAB in DCE were established as the optimized conditions (entry 8). The reaction when carried out under the same conditions in other solvents such as dichloromethane (DCM) and chloroform proved to be much less productive in terms of yields (entries 9, 10), whereas it failed to afford any product in acetonitrile, dimethyl sulfoxide (DMSO) and MeOH (entries 11−13). After the meticulous optimization of reaction conditions, we explored the scope of α-diazophosphonates 1 in the reaction (Scheme 2).

by cyclic voltammetry experiments (please see the Supporting Information), suggested that usual organic dyes such as Rose Bengal (RB•+/RB* = −0.68 V vs SCE)14a and Eosin Y (EY•+/ EY* = −1.11 V vs SCE)14b,c may not be suitable photocatalysts for SET to 1a. At this point, we envisaged that Hantzsch ester (HE), which exhibits high excited state reduction potential (Ered = −2.28 V vs SCE)15 may serve as an appropriate photocatalytic reductant of α-diazophosphonates. The HE’s are known to be strong light harvesting molecules and good single electron as well as hydrogen atom donors upon visible light irradiation.16 Herein, we report results of our investigation on HE-mediated annulation of diazophosphonates, diazocarboxylates, and diazosulfones with alkynes under visible light irradiation (Scheme 1). Scheme 1. Synthesis of Functionalized Naphthalene-1-ols under Metal-Free and Visible Light-Mediated Conditions

Scheme 2. Scope of Reaction: Variation of αDiazophosphonates 1a

We first investigated the proposed HE-mediated reaction with diazophosphonate 1a and phenylacetylene 2a in dichloroethane (DCE) under blue light irradiation (Table 1). To our delight, this Table 1. Optimization of Reaction Conditionsa

a

entry

1a/2a

HE (equiv)

TBAB (equiv)

solvent

yield (%)b

1 2 3 4 5 6 7 8 9 10 11 12 13

1:2 1:2 1:1 1:3 1:2 1:2 1:2 1:2 1:2 1:2 1:2 1:2 1:2

2 2 2 2 0.5 1 1 1 1 1 1 1 1

1 1 1 1 1 1.5 0.5 0.5 0.5 0.5 0.5 0.5

DCE DCE DCE DCE DCE DCE DCE DCE DCM CHCl3 MeCN DMSO MeOH

69 76 68 76 79 82 72 84 58 62 NR NR NR

Reaction conditions: 1 (0.1 mmol), 2a (0.2 mmol), HE (0.1 mmol), and TBAB (0.05 mmol) were irradiated in DCE (1.0 mL) with a blue LED for 6−8 h. bIsolated yields in parentheses.

The aryl (1a−1g) as well as heteroaryl α-diazophosphonates (1h−1n) bearing substituents with varied electronic characters reacted efficiently with phenylacetylene 2a providing corresponding 2-phosphorylated naphthalene-1-ol products (3a−3n) in good to excellent yields. Notably, 3,4-disubstituted substrate 1g afforded a mixture of regioisomeric products 3g and 3g′ in 47% and 33% yields, respectively. However, the heteroaryl substrates bearing diazo-keto moiety at 3-position (1m and 1n) furnished 2-cyclization products (3m and 3n, respectively) exclusively, and the corresponding 4-cyclization products were not detected in both the cases. Next, we aimed to investigate the scope of alkynes 2 in the reaction (Scheme 3). The arylacetylenes with electron-releasing as well as electron-withdrawing groups reacted smoothly with dimethyl (1-diazo-2-oxo-2-phenylethyl)phosphonate 1a under the standard reaction conditions, affording corresponding products 3o−3u in excellent yields. The reaction also worked well when a heteroarylacetylene such as 3-ethynylthiophene was used as substrate with 1a providing 4-(3-thienyl)-substituted naphthalen-1-ol 3v in 72% yield. The aliphatic alkynes such as ethynylcyclohexane and ethynylcyclopropane also provided corresponding phosphorylated naphthalene-1-ols 3w and 3x, respectively, albeit in lower yields. Further, TMS-acetylene as well as ethyl propiolate could also be employed in the reaction with 1a to afford naphthalene-1-ols 3y and 3z bearing TMS and carboxylate ester functionality, respectively, along with phos-

a

Reaction Conditions: 1a (0.1 mmol) with specified amounts of 2a, HE, and additive was irradiated in solvent (1.0 mL) with a blue LED for 6 h. bIsolated yields.

reaction provided the annulated product in 69% yield, which increased to 76% upon addition of tetrabutylammonium bromide (TBAB) in the reaction (entries 1, 2). This is to be noted that 3a was isolated as the exclusive regioisomer, understandably due to the formation of more stable benzylic radical upon trapping of alkynes with enolate vinyl radical (see mechanism).13 Next it was realized that employing 1a and 2a in 1:2 ratio was better than their 1:1 or 1:3 ratio considering reaction yield and economy (entries 2−4). The amount of HE optimal for the B


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Scheme 4. Scope of Reaction: Reaction of α-Diazosulfone and α-Diazocarboxylates with Various Phenylacetylenes 2a

a

Reaction conditions: 1 (0.1 mmol), 2a (0.2 mmol), HE (0.1 mmol), and TBAB (0.05 mmol) were irradiated in DCE (1.0 mL) with a blue LED for 6−12 h. bIsolated yields in parentheses.

Scheme 5. Intramolecular Reactiona

a

Reaction conditions: 1a (0.1 mmol), 2 (0.2 mmol), HE (0.1 mmol), and TBAB (0.05 mmol) were irradiated in DCE (1.0 mL) with a blue LED for 6−12 h. bIsolated yields in parentheses.

phonate group. Moreover, symmetrical as well as unsymmetrical internal alkynes were engaged effectively in the reaction furnishing 1,2,3,4-tetrasubstituted naphthalenes. Whereas reaction of 1a with 1,2-diphenylethyne provided product 3za in 44% yield, two regioisomers 3zb/3zb′ and 3zc/3zc′ were isolated in almost equal amounts in case of reaction of 1a with trimethyl(4-(phenylethynyl)phenyl)silane and 1-isopropyl-4(phenylethynyl)benzene, respectively. The structures of 3zb and 3zb′ were established unambiguously by X-ray analysis of 3zb′ (please see the SI) and following analogy the structures of 3zc and 3zc′ were established.17 The general nature of the reaction was further confirmed by employing α-diazosulfones and α-diazocarboxylates successfully under optimized conditions (Scheme 4). The 2-diazo-1-phenyl-2-(phenylsulfonyl)ethan-1-one 1o, ethyl 2-diazo-3-oxo-3-phenylpropanoate 1p, and ethyl 2-diazo3-(3,4-dimethoxyphenyl)-3-oxopropanoate 1q reacted smoothly with various phenylacetylenes under standard reaction conditions to afford corresponding products in high yields. As expected, two regioisomers 3zk and 3zk′ were isolated in 36% and 23% yield, respectively, when ethyl 2-diazo-3-(3,4dimethoxyphenyl)-3-oxopropanoate 1q was reacted with phenylacetylene 2a. Encouraged by the results obtained so far, we developed the intramolecular benzannulation of o-aryl α-diazophosphonates 4 under the same reaction conditions (Scheme 5). Several o-aryl substituted α-diazophosphonates 4a−4i were subjected to the standard reaction conditions to access the corresponding phosphorylated hydroxy phenanthrenes 5a−5i in excellent yields.

a

Reaction conditions: 4 (0.1 mmol), HE (0.1 mmol), and TBAB (0.05 mmol) were irradiated in DCE (1.0 mL) with a blue LED for 6 h. bIsolated yields in parentheses.

After establishing the general nature and wide substrate scope of the reaction, we probed the reaction mechanism considering mainly three possible routes, viz. (i) formation of electron donor−acceptor (EDA) complex between HE and diazo substrate;18 (ii) energy transfer (EnT) from triplet excited state of HE to the diazo substrate; (iii) radical mechanism via photoinduced electron transfer (PET). We started the mechanistic investigation by comparing the UV−visible spectra of 1a, HE, and TBAB individually and their mixture in DCE (Figure 1). From the combined spectral studies, it was observed that only HE featured a strong absorption in the near-UV region. However, addition of either 1a or TBAB did not change the absorption spectra of the HE. Therefore, the possibility of an EDA complex formation between HE and 1a was ruled out.15 Further, certain control experiments were conducted to understand the reaction mechanism particularly to verify the EnT or ET pathway (Scheme 6). First of all, the importance of photoexcitation was established by performing a reaction in dark, C


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to the generation of enolate-vinyl radical B and HE-radical cation C. The trapping of vinyl radical B by alkyne 2 leads to the benzylic radical D, which affords radical species E through intramolecular homolytic aromatic substitution. The hydrogen atom abstraction from E following hydrogen atom transfer (HAT) from C and subsequent hydrogen elimination leads to the formation of enolated product F, which upon workup affords corresponding hydroxynaphthalenes 3. However, HE-radical cation C as a consequence of HAT forms the pyridinium species G, which upon deprotonation furnishes diethyl 2,6-dimethylpyridine-3,5dicarboxylate byproduct (Scheme 7). Scheme 7. Plausible Mechanism

Figure 1. UV−visible absorption spectra of HE, 1a, and a mixture of 1a with HE and/or TBAB (0.001 M in DCE).

Scheme 6. Control Experiments

In conclusion, we carried out metal-free benzannulation of αdiazo phosphonates, sulfones, and carboxylates with alkynes enabling direct access to the functionalized naphthalene-1-ol. The reaction employs Hantzsch ester as photoreductant under visible light photoredox-mediated conditions. The diazo compounds were stabilized as enolates, which were reduced via PET from excited HE to form enolate vinyl radicals. The same reaction conditions were applied to synthesize phosphorylated phenanthrene-1-ols via intramolecular benzannulation of o-aryl α-diazophosphonates. The highlights of the methodology are mild and metal-free reaction conditions and wide substrate scope.

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which failed to provide any identifiable product (Scheme 6a). Also, no product formation was noticed when the reaction was carried out in the presence of oxygen, a strong triplet quencher (Scheme 6b). This result favors radical mechanism over EnT from HE to the diazo compound. The conclusion drawn from the triplet quenching experiment was further supported by the effect of solvents on the reaction (Scheme 6c). The reaction yield greatly depends on the reaction solvent indicating the probability of the electron-transfer (ET) mechanism since the energy transfer (EnT) pathway should be independent of solvent polarity.19 Further, radical formation was established by trapping the enolate vinyl radical with allyltributyltin to furnish adduct 6 (Scheme 6d; confirmed by mass spectroscopy; please see the Supporting Information). Mechanistically, the control experiments and the high excited state redox potential of HE (Ered = −2.28 V vs SCE) suggested a possible photoinduced electron transfer (PET) from excited HE* to diazoenolate A. The PET followed by N2 extrusion leads

ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.orglett.9b02135. Experimental and characterization data for all new starting substrates and products; details of CV experiment and Xray analysis (PDF) Accession Codes

CCDC 1916456 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 data_ [email protected], or by contacting The Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: +44 1223 336033. D


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(4) (a) Zhu, S.-F.; Zhou, Q.-L. Acc. Chem. Res. 2012, 45, 1365−1377. (b) Gillingham, D.; Fei, N. Chem. Soc. Rev. 2013, 42, 4918−4931. (c) Guo, X.; Hu, W. Acc. Chem. Res. 2013, 46, 2427−2440. (d) Murphy, G. K.; Stewart, C.; West, F. G. Tetrahedron 2013, 69, 2667−2686. (e) Xiao, Q.; Zhang, Y.; Wang, J. Acc. Chem. Res. 2013, 46, 236−247. (f) Liu, Z.; Wang, J. J. Org. Chem. 2013, 78, 10024−10030. (g) Xing, D.; Hu, W. Tetrahedron Lett. 2014, 55, 777−783. (h) Burtoloso, A. C. B.; Santiago, J. V.; Bernardim, B.; Talero, A. G. Curr. Org. Synth. 2015, 12, 650−659. (i) Hu, F.; Xia, Y.; Ma, C.; Zhang, Y.; Wang, J. Chem. Commun. 2015, 51, 7986−7995. (j) Qian, D.; Zhang, J. Chem. Soc. Rev. 2015, 44, 677−698. (k) Wang, B.; Qiu, D.; Zhang, Y.; Wang, J. Beilstein J. Org. Chem. 2016, 12, 796−804. (l) Guttenberger, N.; Breinbauer, R. Tetrahedron 2017, 73, 6815−6829. (m) Keipour, H.; Carreras, V.; Ollevier, T. Org. Biomol. Chem. 2017, 15, 5441−5456. (5) (a) Candeias, N. R.; Afonso, C. A. M. Curr. Org. Chem. 2009, 13, 763−787. (b) Zhang, Y.; Burdziński, G.; Kubicki, J.; Platz, M. S. J. Am. Chem. Soc. 2009, 131, 9646−9647. (c) Yang, Z.; Xu, J. Tetrahedron Lett. 2012, 53, 786−789. (d) Navarro, R.; Perrino, M. P.; Prucker, O.; Rühe, J. Langmuir 2013, 29, 10932−10939. (e) Cui, G.; Thiel, W. Angew. Chem., Int. Ed. 2013, 52, 433−436. (f) Willumstad, T. P.; Haze, O.; Mak, X. O.; Lam, T. Y.; Wang, Y.-P.; Danheiser, R. L. J. Org. Chem. 2013, 78, 11450− 11469. (g) Galkina, O. S.; Rodina, L. L. Russ. Chem. Rev. 2016, 85, 537− 555. (h) Rodina, L. L.; Galkina, O. S.; Maas, G.; Platz, M. S.; Nikolaev, V. A. Asian J. Org. Chem. 2016, 5, 691−698. (i) Rybicka-Jasińska, K.; Shan, W.; Zawada, K.; Kadish, K. M.; Gryko, D. J. Am. Chem. Soc. 2016, 138, 15451−15458. (j) Rodina, L. L.; Baranovskii, V. I.; Galkina, O. S.; Nikolaev, V. A.; Tonogina, N. L.; Povolotskiy, A. V. J. Org. Chem. 2017, 82, 11399−11405. (k) Talero, A. G.; Burtoloso, A. C. B. Synlett 2017, 28, 1748−1752. (l) Forneris, C. C.; Wang, Y.-P.; Mamaliga, G.; Willumstad, T. P.; Danheiser, R. L. Org. Lett. 2018, 20, 6318−6322. (m) Ciszewski, L. W.; Rybicka-Jasińska, K.; Gryko, D. Org. Biomol. Chem. 2019, 17, 432− 448. (6) (a) Xiao, T.; Li, L.; Lin, G.; Mao, Z.-W.; Zhou, L. Org. Lett. 2014, 16, 4232−4235. (b) Xia, X.-D.; Ren, Y.-L.; Chen, J.-R.; Yu, X.-L.; Lu, L.Q.; Zou, Y.-Q.; Wan, J.; Xiao, W.-J. Chem. - Asian J. 2015, 10, 124−128. (c) Liu, Y.; Dong, X.; Deng, G.; Zhou, L. Sci. China: Chem. 2016, 59, 199−202. (d) Rybicka-Jasińska, K.; Ciszewski, Ł. W.; Gryko, D. Adv. Synth. Catal. 2016, 358, 1671−1678. (e) Pramanik, M. M. D.; Nagode, S. B.; Kant, R.; Rastogi, N. Org. Biomol. Chem. 2017, 15, 7369−7373. (f) Ma, M.; Hao, W.; Ma, L.; Zheng, Y.; Lian, P.; Wan, X. Org. Lett. 2018, 20, 5799−5802. (g) Rybicka- Jasińska, K.; Orłowska, K.; Karczewski, M.; Zawada, K.; Gryko, D. Eur. J. Org. Chem. 2018, 2018, 6634−6642. (7) Wang, Z.; Herraiz, A. G.; del Hoyo, A. M.; Suero, M. G. Nature 2018, 554, 86−91. (8) (a) Vaske, Y. S. M.; Mahoney, M. E.; Konopelski, J. P.; Rogow, D. L.; McDonald, W. J. J. Am. Chem. Soc. 2010, 132, 11379−11385. (b) Bernardim, B.; Hardman-Baldwin, A. M.; Burtoloso, A. C. B. RSC Adv. 2015, 5, 13311−13314. (9) Jurberg, I. D.; Davies, H. M. L. Chem. Sci. 2018, 9, 5112−5118. (10) (a) Zhang, X.; Du, C.; Zhang, H.; Li, X.-C.; Wang, Y. L.; Niu, J.-L.; Song, M.-P. Synthesis 2019, 51, 889−898. (b) Hommelsheim, R.; Guo, Y.; Yang, Z.; Empel, C.; Koenigs, R. M. Angew. Chem., Int. Ed. 2019, 58, 1203−1207. (11) Xiao, T.; Mei, M.; He, Y.; Zhou, L. Chem. Commun. 2018, 54, 8865−8868. (12) Bethell, D.; Parker, V. D. Acc. Chem. Res. 1988, 21, 400−407. (13) He, Y.; Chen, H.; Li, L.; Huang, J.; Xiao, T.; Anand, D.; Zhou, L. J. Photochem. Photobiol., A 2018, 355, 220−225. (14) (a) Ravelli, D.; Fagnoni, M. ChemCatChem 2012, 4, 169−171. (b) Hari, D. P.; Künig, B. Chem. Commun. 2014, 50, 6688−6699. (c) Majek, M.; Filace, F.; Wangelin, A. J. Beilstein J. Org. Chem. 2014, 10, 981−989. (15) Jung, J.; Kim, J.; Park, G.; You, Y.; Chob, E. J. Adv. Synth. Catal. 2016, 358, 74−80. (16) (a) Huang, W.; Cheng, X. Synlett 2017, 28, 148−158. (b) Gu, F.; Huang, W.; Liu, X.; Chen, W.; Cheng, X. Adv. Synth. Catal. 2018, 360, 925−931. (c) Song, Z.-Y.; Zhang, C.-L.; Ye, S. Org. Biomol. Chem. 2019, 17, 181−185. (d) Ji, P.; Zhang, Y.; Wei, Y.; Huang, H.; Hu, W.; Mariano, P. A.; Wang, W. Org. Lett. 2019, 21, 3086−3092.

AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected] or [email protected] ORCID

Namrata Rastogi: 0000-0002-7528-5288 Author Contributions

The manuscript was written through contributions of all authors. Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS S.B.N. thanks UGC, New Delhi for the Ph.D fellowship. We thank SAIF division of CSIR-CDRI for the analytical support. We gratefully acknowledge the X-ray diffraction facility of Indian Institute of Technology, Kanpur for X-ray data collection of 3zb′. We are thankful to Dr. Iti Gupta, Department of Chemistry, Indian Institute of Technology, Gandhi Nagar for recording CV data of 1a. We also acknowledge Department of Science & Technology (DST), New Delhi for the financial support (Project ref. No.: EMR/2016/006975). CDRI Communication No. 9867.

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REFERENCES

(1) (a) Nawrat, C. C.; Moody, C. J. Nat. Prod. Rep. 2011, 28, 1426− 1444. (b) Ford, A.; Miel, H.; Ring, A.; Slattery, C. N.; Maguire, A. R.; McKervey, M. A. Chem. Rev. 2015, 115, 9981−10080. (c) Mix, K. A.; Aronoff, M. R.; Raines, R. T. ACS Chem. Biol. 2016, 11, 3233−3244. (d) Marinozzi, M.; Pertusati, F.; Serpi, M. Chem. Rev. 2016, 116, 13991− 14055. (e) Mertens, L.; Koenigs, R. M. Org. Biomol. Chem. 2016, 14, 10547−10556. (f) Candeias, N. R.; Paterna, R.; Gois, P. M. P. Chem. Rev. 2016, 116, 2937−2981. (g) Cheng, Q.-Q.; Deng, Y.; Lankelma, M.; Doyle, M. P. Chem. Soc. Rev. 2017, 46, 5425−5443. (h) Li, Y.-P.; Li, Z.Q.; Zhu, S.-F. Tetrahedron Lett. 2018, 59, 2307−2316. (i) Wang, J. Pure Appl. Chem. 2018, 90, 617−623. (j) Dhameja, M.; Pandey, J. Asian J. Org. Chem. 2018, 7, 1502−1523. (k) Xiang, Y.; Wang, C.; Ding, Q.; Peng, Y. Adv. Synth. Catal. 2019, 361, 919−944. (2) (a) Zhao, Y.; Wang, J. Synlett 2005, 2005, 2886−2892. (b) Friedman, R.; Caflisch, A. ChemMedChem 2009, 4, 1317−1326. (c) Zhang, Y.; Wang, J. Chem. Commun. 2009, 45, 5350−5361. (d) Hashimoto, T.; Maruoka, K. Bull. Chem. Soc. Jpn. 2013, 86, 1217− 1230. (e) An, S. S.; Chi, K.-W.; Kim, I.; Song, Y. H.; Singh, N.; Jeong, Y. J.; Kwon, J. E.; Kim, H.; Cho, Y.; Kang, S. C. Int. J. Nanomed. 2015, 10, 143−153. (f) Guedouar, H.; Aloui, F.; Beltifa, A.; Mansour, H. B.; Hassine, B. B. C. R. C. R. Chim. 2017, 20, 841−849. (g) Baiju, T. V.; Namboothiri, I. N. N. Chem. Rec. 2017, 17, 939−955. (3) (a) Zhao, X.; Zhang, Y.; Wang, J. Chem. Commun. 2012, 48, 10162−10173. (b) Bera, K.; Sarkar, S.; Jalal, S.; Jana, U. J. Org. Chem. 2012, 77, 8780−8786. (c) Gillingham, D.; Fei, N. Chem. Soc. Rev. 2013, 42, 4918−4931. (d) Patel, D. G.; Walton, I. M.; Cox, J. M.; Gleason, C. J.; Butzer, D. R.; Benedict, J. B. Chem. Commun. 2014, 50, 2653−2656. (e) Li, M.; An, C.; Marszalek, T.; Guo, X.; Long, Y.-Z.; Yin, H.; Gu, C.; Baumgarten, M.; Pisula, W.; Müllen, K. Chem. Mater. 2015, 27, 2218− 2223. (f) Bera, K.; Sarkar, S.; Jana, U. Tetrahedron Lett. 2015, 56, 312− 315. (g) Caballero, A.; Díaz-Requejo, M. M.; Fructos, M. R.; Olmos, A.; Urbano, J.; Pérez, P. J. Dalton Trans. 2015, 44, 20295−20307. (h) Fructos, M. R.; Díaz- Requejo, M. M.; Pérez, P. J. Chem. Commun. 2016, 52, 7326−7335. (i) Torres, O.; Anna, P.-Q. Tetrahedron Lett. 2016, 57, 3881−3891. (j) Liu, L.; Zhang, J. Chem. Soc. Rev. 2016, 45, 506−516. (k) Kim, Y.-A.; Hwang, K-II.; Kang, M.; Kim, N.-K.; Jang, S.Y.; Kim, I.-B.; Kim, J.; Kim, D.-Y. Org. Electron. 2017, 44, 238−246. (l) Xia, Y.; Qiu, D.; Wang, J. Chem. Rev. 2017, 117, 13810−13889. (m) Cheng, Q.-Q.; Yu, Y.; Yedoyan, J.; Doyle, M. P. ChemCatChem 2018, 10, 488−496. E


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Organic Letters (17) Crystal structure of compound 3zb′ has been deposited at the Cambridge Crystallographic Data Center and allocated the reference no. CCDC 1916456. (18) (a) Arceo, E.; Jurberg, I. D.; Á lvarez- Fernández, A.; Melchiorre, P. Nat. Chem. 2013, 5, 750−756. (b) Lima, C. G. S.; de M. Lima, T.; Duarte, M.; Jurberg, I. D.; Paixao, M. W. ACS Catal. 2016, 6, 1389− 1407. (c) Postigo, A. Eur. J. Org. Chem. 2018, 2018, 6391−6404. (d) Guillemard, L.; Colobert, F.; Wencel-Delord, J. Adv. Synth. Catal. 2018, 360, 4184−4190. (e) Guo, Q.; Wang, M.; Liu, H.; Wang, R.; Xu, Z. Angew. Chem., Int. Ed. 2018, 57, 4747−4751. (f) Zhang, H.-H.; Shouyun, Y. Org. Lett. 2019, 21, 3711−3715. (g) Wang, R.; Wang, L.; Xu, Q.; Ren, B.-Y.; Liang, F. Org. Lett. 2019, 21, 3072−3076. (19) (a) Strieth-Kalthoff, F.; James, M. J.; Teders, M.; Pitzer, L.; Glorius, F. Chem. Soc. Rev. 2018, 47, 7190−7202. (b) Zhou, Q.-Q.; Zou, Y.-Q.; Lu, L.-Q.; Xiao, W.-J. Angew. Chem., Int. Ed. 2019, 58, 1586−1604.

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Hantzsch Ester-Mediated Benzannulation of Diazo Compounds under

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