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Shan Y, Yang Z, Yu JT, Pan C. Metal-free polychloromethyl radical-initiated cyclization of unactivated N-allylindoles towards pyrrolo[1,2- a]indoles. Org Biomol Chem 2022; 20:5259-5263. [PMID: 35735246 DOI: 10.1039/d2ob00471b] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
A metal-free polychloromethyl radical-initiated cyclization of unactivated alkenes was developed using CH2Cl2 and CHCl3 as the di- and trichloromethyl radical sources. Variously substituted N-allyl-indoles were successfully transformed into the corresponding C2-(di- and trichloromethyl) pyrrolo[1,2-a]indoles in moderate to good yields. This reaction has a broad substrate scope and good functional group tolerance. Dibromomethylated products can also be obtained using CH2Br2 under standard conditions.
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Affiliation(s)
- Yujia Shan
- School of Petrochemical Engineering, Jiangsu Key Laboratory of Advanced Catalytic Materials & Technology, Changzhou University, Changzhou 213164, P. R. China.
| | - Zixian Yang
- School of Petrochemical Engineering, Jiangsu Key Laboratory of Advanced Catalytic Materials & Technology, Changzhou University, Changzhou 213164, P. R. China.
| | - Jin-Tao Yu
- School of Petrochemical Engineering, Jiangsu Key Laboratory of Advanced Catalytic Materials & Technology, Changzhou University, Changzhou 213164, P. R. China.
| | - Changduo Pan
- School of Chemical and Environmental Engineering, Jiangsu University of Technology, Changzhou 213001, P. R. China.
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2
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Dong X, Sun X, Yang Y, Liu W, Zheng B, Li X, Zhang D, Wang F, Liu H. Pd/Et 3N·HI-Catalyzed Intramolecular C-H Alkylation to Access [ a]-Annulated Indoles via Highly Regioselective Ring-Opening of Epoxides. J Org Chem 2022; 87:7995-8004. [PMID: 35671111 DOI: 10.1021/acs.joc.2c00630] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
A Pd/Et3N·HI-catalyzed intramolecular C-H alkylation of indoles with epoxides was achieved to furnish N-fused indole frameworks (5-, 6-, and 7-membered rings) bearing an alcohol group. The conversion proceeded smoothly in the presence of a catalytic amount of Et3N·HI together with a palladium catalyst and exhibited great functional group tolerance. The employment of Et3N·HI not only avoids the prior preparation of alkyl halide substrates but also is the key to the high chemoselective ring-opening of epoxides. Preliminary mechanism explorations strongly support a radical pathway, and the catalytic cycle was established tentatively according to the mechanism investigation experiments.
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Affiliation(s)
- Xu Dong
- School of Chemistry and Chemical Engineering, Shandong University of Technology, 266 West Xincun Road, Zibo 255049, People's Republic of China
| | - Xi Sun
- School of Chemistry and Chemical Engineering, Shandong University of Technology, 266 West Xincun Road, Zibo 255049, People's Republic of China
| | - Yi Yang
- School of Chemistry and Chemical Engineering, Shandong University of Technology, 266 West Xincun Road, Zibo 255049, People's Republic of China
| | - Weiwei Liu
- School of Chemistry and Chemical Engineering, Shandong University of Technology, 266 West Xincun Road, Zibo 255049, People's Republic of China
| | - Bowen Zheng
- School of Chemistry and Chemical Engineering, Shandong University of Technology, 266 West Xincun Road, Zibo 255049, People's Republic of China
| | - Xinjin Li
- School of Chemistry and Chemical Engineering, Shandong University of Technology, 266 West Xincun Road, Zibo 255049, People's Republic of China
| | - Daopeng Zhang
- School of Chemistry and Chemical Engineering, Shandong University of Technology, 266 West Xincun Road, Zibo 255049, People's Republic of China
| | - Fagang Wang
- School of Chemistry and Chemical Engineering, Shandong University of Technology, 266 West Xincun Road, Zibo 255049, People's Republic of China
| | - Hui Liu
- School of Chemistry and Chemical Engineering, Shandong University of Technology, 266 West Xincun Road, Zibo 255049, People's Republic of China
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3
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Yang R, Yi D, Shen K, Fu Q, Wei J, Lu J, Yang L, Wang L, Wei S, Zhang Z. Indole and Pyrrole Derivatives as Pre-photocatalysts and Substrates in the Sulfonyl Radical-Triggered Relay Cyclization Leading to Sulfonylated Heterocycles. Org Lett 2022; 24:2014-2019. [DOI: 10.1021/acs.orglett.2c00472] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Affiliation(s)
- Ran Yang
- Department of Medicinal Chemistry, School of Pharmacy, Southwest Medical University, Luzhou 646000, China
| | - Dong Yi
- Department of Medicinal Chemistry, School of Pharmacy, Southwest Medical University, Luzhou 646000, China
- State Key Laboratory of Applied Organic Chemistry, Lanzhou University, Lanzhou 730000, China
| | - Kunrong Shen
- Department of Medicinal Chemistry, School of Pharmacy, Southwest Medical University, Luzhou 646000, China
| | - Qiang Fu
- Department of Medicinal Chemistry, School of Pharmacy, Southwest Medical University, Luzhou 646000, China
| | - Jun Wei
- Department of Medicinal Chemistry, School of Pharmacy, Southwest Medical University, Luzhou 646000, China
| | - Ji Lu
- Department of Medicinal Chemistry, School of Pharmacy, Southwest Medical University, Luzhou 646000, China
| | - Lin Yang
- Department of Medicinal Chemistry, School of Pharmacy, Southwest Medical University, Luzhou 646000, China
| | - Li Wang
- Department of Nuclear Medicine, Affiliated Hospital, Southwest Medical University, Luzhou 646000, China
| | - Siping Wei
- Department of Medicinal Chemistry, School of Pharmacy, Southwest Medical University, Luzhou 646000, China
- State Key Laboratory of Natural and Biomimetic Drugs, Peking University, Beijing 100191, China
| | - Zhijie Zhang
- Department of Medicinal Chemistry, School of Pharmacy, Southwest Medical University, Luzhou 646000, China
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Shelke YG, Hande PE, Gharpure SJ. Recent advances in the synthesis of pyrrolo[1,2- a]indoles and their derivatives. Org Biomol Chem 2021; 19:7544-7574. [PMID: 34524330 DOI: 10.1039/d1ob01103k] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
The pyrrolo[1,2-a]indole unit is a privileged heterocycle found in numerous natural products and has been shown to exhibit diverse pharmacological properties. Thus, recent years have witnessed immense interest from the synthesis community on the synthesis of this scaffold. In light of the ever-increasing demand for pyrrolo[1,2-a]indoles in drug discovery, this review provides an overview of recent synthesis methods for the preparation of pyrrolo[1,2-a]indoles and their derivatives. The mechanistic pathway and stereo-electronic factors affecting the yield and selectivity of the product are briefly explained. Furthermore, we have attempted to demonstrate the utility of the developed methods in the synthesis of bioactive molecules and natural products, wherever offered.
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Affiliation(s)
- Yogesh G Shelke
- Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai-400076, India.
| | - Pankaj E Hande
- Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai-400076, India.
| | - Santosh J Gharpure
- Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai-400076, India.
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Das AJ, Chouhan R, Das SK. Hexafluoroisopropanol-Mediated Intramolecular Ring-Opening Cyclization of Indolyl- N-Tethered Epoxides: Tether-Length-Controlled Synthesis of 1,7- and 1,2-Fused Indoles. J Org Chem 2021; 86:8274-8285. [PMID: 34061532 DOI: 10.1021/acs.joc.1c00721] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Despite having the capability to construct benzo-fused heterocycles in complete atom economy and high chemo-, regio-, enantio-, and diastereoselectivities, intramolecular Friedel-Crafts epoxide arene cyclization (IFCEAC) remains underutilized in organic synthesis. The wide adaptation of this powerful Csp2-Csp3 bond-forming reaction, therefore, requires a broad understanding of the substrate scope to better impact heterocycle synthesis. Along this line, we investigated the applicability of IFCEAC for the synthesis of 1,7- and 1,2-fused indoles. In this article, we report the results of our systematic investigation into the scope and limitations of the first examples of the hexafluoro-2-propanol (HFIP)-mediated IFCEAC of readily accessible indolyl-N-tethered epoxides. We observed that the nature and position of the indole and epoxide substituents and the tether length separating these two reacting moieties have strong effects on the cyclization. This mild and transition-metal-free protocol delivered pyrrolo[3,2,1-ij]quinolin-5-ols in moderate to good yields from substrates bearing both a methylene linker that connects the indole and epoxide moieties and an electron-rich indole carbocyclic ring. Notably, the reactions required the presence of a π-activating aryl substituent on the reacting epoxide carbon atom. Interestingly, replacing the methylene tether with an ethylene unit resulted in regioswitching, which delivered the corresponding tetrahydropyrido[1,2-a]indol-8-ols in good to high yields. We could also successfully extend this methodology to pyrrolyl-N-tethered epoxides for a very high-yielding synthesis of tetrahydroindolizin-7-ols.
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Affiliation(s)
- Arup Jyoti Das
- Department of Chemical Sciences, Tezpur University, Napaam, Sonitpur, Tezpur, Assam 784028, India
| | - Raju Chouhan
- Department of Chemical Sciences, Tezpur University, Napaam, Sonitpur, Tezpur, Assam 784028, India
| | - Sajal Kumar Das
- Department of Chemical Sciences, Tezpur University, Napaam, Sonitpur, Tezpur, Assam 784028, India
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Ortega A, Uria U, Tejero T, Prieto L, Reyes E, Merino P, Vicario JL. Brønsted Acid Catalyzed (4 + 2) Cyclocondensation of 3-Substituted Indoles with Donor–Acceptor Cyclopropanes. Org Lett 2021; 23:2326-2331. [PMID: 33689377 PMCID: PMC9490874 DOI: 10.1021/acs.orglett.1c00470] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
![]()
Acylcyclopropanes
are employed as useful donor–acceptor
cyclopropanes that undergo formal (4 + 2) cyclocondensation with N-unprotected 3-substituted indoles in the presence of a
Brønsted acid catalyst. The reaction involves the simultaneous
alkylation of both the N and C-2 positions of the indole and provides
access to the 8,9-dihydropyrido[1,2-a]indole scaffold that is the central core of several biologically
relevant indole alkaloids in excellent yields and good selectivities.
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Affiliation(s)
- Alesandere Ortega
- Department of Organic and Inorganic Chemistry, University of the Basque Country (UPV/EHU). P.O.
Box 644, 48080 Bilbao, Spain
| | - Uxue Uria
- Department of Organic and Inorganic Chemistry, University of the Basque Country (UPV/EHU). P.O.
Box 644, 48080 Bilbao, Spain
| | - Tomás Tejero
- Instituto de Síntesis Química y Catálisis Homogénea (ISQCH), Universidad de Zaragoza, CSIC, 50009 Zaragoza, Spain
| | - Liher Prieto
- Department of Organic and Inorganic Chemistry, University of the Basque Country (UPV/EHU). P.O.
Box 644, 48080 Bilbao, Spain
| | - Efraim Reyes
- Department of Organic and Inorganic Chemistry, University of the Basque Country (UPV/EHU). P.O.
Box 644, 48080 Bilbao, Spain
| | - Pedro Merino
- Instituto de Biocomputación y Física de Sistemas Complejos (BIFI), Universidad de Zaragoza, 50009 Zaragoza, Spain
| | - Jose L. Vicario
- Department of Organic and Inorganic Chemistry, University of the Basque Country (UPV/EHU). P.O.
Box 644, 48080 Bilbao, Spain
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