1
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Hernandez J, Lawrie AP, Frontier AJ. Alkynyl Halo-Aza-Prins Annulative Couplings. J Org Chem 2023; 88:16065-16075. [PMID: 37971946 PMCID: PMC10696554 DOI: 10.1021/acs.joc.3c01305] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2023] [Revised: 09/22/2023] [Accepted: 10/05/2023] [Indexed: 11/19/2023]
Abstract
This article is a comprehensive report describing our studies in the field of aza-alkynyl Prins chemistry, comparing and contrasting the different reaction partners and reactivities observed during method development. The synthetic strategies combine an alkynyl aza-Prins coupling with an annulation, enabling the preparation of different nitrogen-containing heterocycles. Different iminium ions are explored as viable electrophiles for an alkynyl Prins cyclization, terminated by capture with a halogen nucleophile to form a vinyl halide. The synthetic utility of this functional handle is exploited through a number of Suzuki cross-couplings, allowing for the preparation of a modest library of compounds. In most cases, the Prins couplings are highly selective for the vinyl halides with E geometry, resulting from anti-addition across the alkyne.
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Affiliation(s)
- Jackson
J. Hernandez
- Department of Chemistry, University
of Rochester, 120 Trustee Road, Rochester, New York 14611, United States
| | - Alexandra P. Lawrie
- Department of Chemistry, University
of Rochester, 120 Trustee Road, Rochester, New York 14611, United States
| | - Alison J. Frontier
- Department of Chemistry, University
of Rochester, 120 Trustee Road, Rochester, New York 14611, United States
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2
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Biswas S, Shit S, Behera BK, Sahu AK, Saikia AK. Leveraging cascade alkynyl Prins cyclization towards the stereoselective synthesis of spiro-furan quinazolinone scaffolds. Chem Commun (Camb) 2023; 59:14301-14304. [PMID: 37965888 DOI: 10.1039/d3cc04464e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2023]
Abstract
A TfOH-promoted, metal-free protocol has been unveiled for the synthesis of spiro-furan quinazolinones employing alkynol urea derivatives utilizing alkynyl Prins cyclization reaction. This methodology produces highly functionalized spiro-heterocycles in excellent yields with exclusive E-selectivity under ambient conditions. Furthermore, late-stage modifications incorporate bromide and acetyl functionalities into the synthesized spiro-heterocycles.
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Affiliation(s)
- Subhamoy Biswas
- Department of Chemistry, Indian Institute of Technology Guwahati, Guwahati-781039, Assam, India.
| | - Sudip Shit
- Department of Chemistry, Indian Institute of Technology Guwahati, Guwahati-781039, Assam, India.
| | - Bipin Kumar Behera
- Department of Chemistry, Indian Institute of Technology Guwahati, Guwahati-781039, Assam, India.
| | - Archana Kumari Sahu
- Department of Chemistry, Indian Institute of Technology Guwahati, Guwahati-781039, Assam, India.
| | - Anil K Saikia
- Department of Chemistry, Indian Institute of Technology Guwahati, Guwahati-781039, Assam, India.
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3
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Feng L, Teng Y, Yu X, Wang Z, Rao W. Brønsted Acid-Catalyzed Dehydrative Nazarov-Type Cyclization/C2-N1 Cleavage Cascade of Perfluoroalkylated 3-Indolyl(2-benzothienyl)methanols. Org Lett 2023. [PMID: 37384549 DOI: 10.1021/acs.orglett.3c01503] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/01/2023]
Abstract
A novel and unprecedented p-toluenesulfonic acid-catalyzed dehydrative Nazarov-type cyclization/C2-N1 bond cleavage cascade reaction of perfluoroalkylated 3-indolyl(2-benzothienyl)methanols has been developed. This reaction provides an efficient and practical protocol for the construction of highly functionalized benzothiophene-fused cyclopentenones with exclusive stereoselectivity. In addition, this cascade transformation also delineates a rare example of the involvement of the selective C2-N1 bond cleavage of indoles.
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Affiliation(s)
- Li Feng
- Jiangsu Co-Innovation Center for Efficient Processing and Utilization of Forest Resources, College of Chemical Engineering, Nanjing Forestry University, Nanjing 210037, China
| | - Yuling Teng
- Jiangsu Co-Innovation Center for Efficient Processing and Utilization of Forest Resources, College of Chemical Engineering, Nanjing Forestry University, Nanjing 210037, China
| | - Xiangdong Yu
- Jiangsu Co-Innovation Center for Efficient Processing and Utilization of Forest Resources, College of Chemical Engineering, Nanjing Forestry University, Nanjing 210037, China
| | - Zeliang Wang
- Jiangsu Co-Innovation Center for Efficient Processing and Utilization of Forest Resources, College of Chemical Engineering, Nanjing Forestry University, Nanjing 210037, China
| | - Weidong Rao
- Jiangsu Co-Innovation Center for Efficient Processing and Utilization of Forest Resources, College of Chemical Engineering, Nanjing Forestry University, Nanjing 210037, China
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4
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Milosavljevic A, Holt C, Frontier AJ. Nitrogen-interrupted halo-Prins/ halo-Nazarov fragment coupling cascade for the synthesis of indolines. Chem Sci 2023; 14:5431-5437. [PMID: 37234889 PMCID: PMC10208031 DOI: 10.1039/d3sc00986f] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2023] [Accepted: 04/20/2023] [Indexed: 05/28/2023] Open
Abstract
The nitrogen-interrupted Nazarov cyclization can be a powerful method for the stereocontrolled synthesis of sp3-rich N-heterocycles. However, due to the incompatibility between the basicity of nitrogen and the acidic reaction conditions, examples of this type of Nazarov cyclization are scarce. Herein, we report a one-pot nitrogen-interrupted halo-Prins/halo-Nazarov coupling cascade that joins two simple building blocks, an enyne and a carbonyl partner, to furnish functionalized cyclopenta[b]indolines with up to four contiguous stereocenters. For the first time, we provide a general method for the alkynyl halo-Prins reaction of ketones, thus enabling the formation of quaternary stereocenters. Additionally, we describe the outcomes of secondary alcohol enyne couplings, which exhibit helical chirality transfer. Furthermore, we investigate the impact of aniline enyne substituents on the reaction and evaluate the tolerance of different functional groups. Finally, we discuss the reaction mechanism and demonstrate various transformations of the prepared indoline scaffolds, highlighting their applicability in drug discovery campaigns.
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Affiliation(s)
| | - Connor Holt
- Department of Chemistry, University of Rochester Rochester NY USA 14627-0216
- Worldwide Research and Development, Pfizer, Inc. Eastern Point Road, Groton Connecticut 06340 USA
| | - Alison J Frontier
- Department of Chemistry, University of Rochester Rochester NY USA 14627-0216
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5
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Hernandez JJ, Frontier AJ. Alkynyl Prins carbocyclization cascades for the synthesis of linear-fused heterocyclic ring systems. Chem Sci 2022; 13:13836-13842. [PMID: 36544720 PMCID: PMC9710218 DOI: 10.1039/d2sc04750k] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2022] [Accepted: 11/04/2022] [Indexed: 11/12/2022] Open
Abstract
We report a Brønsted acid-catalyzed carbocyclization cascade, featuring condensation of an alcohol/sulfonamide with an aldehyde followed by an intramolecular three-component coupling involving an alkyne, an oxocarbenium/iminium ion, and an arene. A formal cycloaddition is embedded in the cationic cascade, which enables the synthesis of a wide range of fused heterotricycles. The diastereoselectivity of the cascade is studied using secondary alcohols/sulfonamides with different carbonyl partners. The described method results in the preparation of synthetically versatile scaffolds with ample opportunity for further derivatization at the resulting tetrasubstituted olefin, or by inclusion of other functionalizable motifs from the starting materials. It is worth noting that this chemistry also facilitates the synthesis of piperidines and 1,4-oxazepanes, as well as the inclusion of indoles and benzofurans, which are privileged motifs for medicinal chemistry. Herein we present the generality of this approach and some chemical transformations that can be achieved with our substrates.
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Affiliation(s)
- Jackson J. Hernandez
- Department of Chemistry, University of Rochester120 Trustee RoadRochesterNew York 14611USA
| | - Alison J. Frontier
- Department of Chemistry, University of Rochester120 Trustee RoadRochesterNew York 14611USA
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6
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Zhang Y, Chen Y, Song M, Tan B, Jiang Y, Yan C, Jiang Y, Hu X, Zhang C, Chen W, Xu J. Total Syntheses of Calyciphylline A-Type Alkaloids (-)-10-Deoxydaphnipaxianine A, (+)-Daphlongamine E and (+)-Calyciphylline R via Late-Stage Divinyl Carbinol Rearrangements. J Am Chem Soc 2022; 144:16042-16051. [PMID: 36007885 DOI: 10.1021/jacs.2c05957] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
Among the famous Daphniphyllum alkaloids family, the calyciphylline A-type subfamily has triggered particular interest from the organic synthesis community in recent years. Here, we report divergent total syntheses of three calyciphylline A-type alkaloids, namely, (-)-10-deoxydaphnipaxianine A, (+)-daphlongamine E, and (+)-calyciphylline R. Our work highlights an efficient, divergent strategy via late-stage divinyl carbinol rearrangements, including an unprecedented oxidative Nazarov electrocyclization using an unfunctionalized tertiary divinyl carbinol and an unusual allylic alcohol rearrangement. A highly efficient "donor-acceptor" platinum catalyst was used for a critical nitrile hydration step. Moreover, the power of selective amide reductions has also been showcased by novel and classic tactics.
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Affiliation(s)
- Yan Zhang
- Department of Chemistry and Shenzhen Grubbs Institute and Guangdong Provincial Key Laboratory of Catalysis and Shenzhen Key Laboratory of Small Molecule Drug Discovery and Synthesis, Southern University of Science and Technology, Shenzhen 518055, China
| | - Yuye Chen
- Department of Chemistry and Shenzhen Grubbs Institute and Guangdong Provincial Key Laboratory of Catalysis and Shenzhen Key Laboratory of Small Molecule Drug Discovery and Synthesis, Southern University of Science and Technology, Shenzhen 518055, China
| | - Manrong Song
- Department of Chemistry and Shenzhen Grubbs Institute and Guangdong Provincial Key Laboratory of Catalysis and Shenzhen Key Laboratory of Small Molecule Drug Discovery and Synthesis, Southern University of Science and Technology, Shenzhen 518055, China
| | - Bin Tan
- Department of Chemistry and Shenzhen Grubbs Institute and Guangdong Provincial Key Laboratory of Catalysis and Shenzhen Key Laboratory of Small Molecule Drug Discovery and Synthesis, Southern University of Science and Technology, Shenzhen 518055, China
| | - Yujia Jiang
- Department of Chemistry and Shenzhen Grubbs Institute and Guangdong Provincial Key Laboratory of Catalysis and Shenzhen Key Laboratory of Small Molecule Drug Discovery and Synthesis, Southern University of Science and Technology, Shenzhen 518055, China
| | - Chongyuan Yan
- Department of Chemistry and Shenzhen Grubbs Institute and Guangdong Provincial Key Laboratory of Catalysis and Shenzhen Key Laboratory of Small Molecule Drug Discovery and Synthesis, Southern University of Science and Technology, Shenzhen 518055, China
| | - Yuyang Jiang
- Department of Chemistry and Shenzhen Grubbs Institute and Guangdong Provincial Key Laboratory of Catalysis and Shenzhen Key Laboratory of Small Molecule Drug Discovery and Synthesis, Southern University of Science and Technology, Shenzhen 518055, China
| | - Xinyue Hu
- Department of Chemistry and Shenzhen Grubbs Institute and Guangdong Provincial Key Laboratory of Catalysis and Shenzhen Key Laboratory of Small Molecule Drug Discovery and Synthesis, Southern University of Science and Technology, Shenzhen 518055, China
| | - Chengqian Zhang
- Department of Chemistry and Shenzhen Grubbs Institute and Guangdong Provincial Key Laboratory of Catalysis and Shenzhen Key Laboratory of Small Molecule Drug Discovery and Synthesis, Southern University of Science and Technology, Shenzhen 518055, China
| | - Wenqing Chen
- Department of Chemistry and Shenzhen Grubbs Institute and Guangdong Provincial Key Laboratory of Catalysis and Shenzhen Key Laboratory of Small Molecule Drug Discovery and Synthesis, Southern University of Science and Technology, Shenzhen 518055, China
| | - Jing Xu
- Department of Chemistry and Shenzhen Grubbs Institute and Guangdong Provincial Key Laboratory of Catalysis and Shenzhen Key Laboratory of Small Molecule Drug Discovery and Synthesis, Southern University of Science and Technology, Shenzhen 518055, China
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7
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Motiwala HF, Armaly AM, Cacioppo JG, Coombs TC, Koehn KRK, Norwood VM, Aubé J. HFIP in Organic Synthesis. Chem Rev 2022; 122:12544-12747. [PMID: 35848353 DOI: 10.1021/acs.chemrev.1c00749] [Citation(s) in RCA: 108] [Impact Index Per Article: 54.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
1,1,1,3,3,3-Hexafluoroisopropanol (HFIP) is a polar, strongly hydrogen bond-donating solvent that has found numerous uses in organic synthesis due to its ability to stabilize ionic species, transfer protons, and engage in a range of other intermolecular interactions. The use of this solvent has exponentially increased in the past decade and has become a solvent of choice in some areas, such as C-H functionalization chemistry. In this review, following a brief history of HFIP in organic synthesis and an overview of its physical properties, literature examples of organic reactions using HFIP as a solvent or an additive are presented, emphasizing the effect of solvent of each reaction.
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Affiliation(s)
- Hashim F Motiwala
- Divison of Chemical Biology and Medicinal Chemistry, UNC Eshelman School of Pharmacy, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599 United States
| | - Ahlam M Armaly
- Divison of Chemical Biology and Medicinal Chemistry, UNC Eshelman School of Pharmacy, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599 United States
| | - Jackson G Cacioppo
- Divison of Chemical Biology and Medicinal Chemistry, UNC Eshelman School of Pharmacy, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599 United States
| | - Thomas C Coombs
- Department of Chemistry, University of North Carolina Wilmington, Wilmington, North Carolina 28403 United States
| | - Kimberly R K Koehn
- Divison of Chemical Biology and Medicinal Chemistry, UNC Eshelman School of Pharmacy, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599 United States
| | - Verrill M Norwood
- Divison of Chemical Biology and Medicinal Chemistry, UNC Eshelman School of Pharmacy, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599 United States
| | - Jeffrey Aubé
- Divison of Chemical Biology and Medicinal Chemistry, UNC Eshelman School of Pharmacy, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599 United States
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8
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Wang Z, Yamazaki S, Mikata Y, Oba M, Takashima H, Morimoto T, Ogawa A. Intramolecular Diels-Alder Reactions of α-Bromostyrene-Functionalized Unsaturated Carboxamides. J Org Chem 2022; 87:11148-11164. [PMID: 35944162 DOI: 10.1021/acs.joc.2c01417] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Intramolecular cycloaddition reactions of α-bromostyrene-functionalized amides of monomethyl fumarate were investigated. The reaction of the amides with Et3N in toluene at 110 °C gave 1,4-dihydronaphthalenes. The 1,4-dihydronaphthalenes may be produced via the intramolecular Diels-Alder reaction, proton transfer, and dehydrobromination by a base, along with C═C bond isomerization by proton transfer. The reaction of amide derivatives with halogen on a benzene ring and alkali metal carbonates in toluene at 110 °C gave naphthalene derivatives directly. Dehydrogenation of various 1,4-dihydronaphthalenes with cesium or rubidium carbonate in toluene at 110 °C gave naphthalene derivatives. The retardation by TEMPO, acceleration by air for some substrates, and density functional theory calculations suggest a radical mechanism caused by intervention of molecular oxygen.
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Affiliation(s)
- Zhichao Wang
- Department of Applied Chemistry, Graduate School of Engineering, Osaka Prefecture University, Gakuen-cho 1-1, Nakaku, Sakai, Osaka 599-8531, Japan
| | - Shoko Yamazaki
- Department of Chemistry, Nara University of Education, Takabatake-cho, Nara 630-8528, Japan
| | - Yuji Mikata
- Laboratory for Molecular and Functional Design, Department of Engineering, Nara Women's University Nara 630-8506, Japan
| | - Miho Oba
- Department of Chemistry, Faculty of Science, Nara Women's University, Nara 630-8506, Japan
| | - Hiroshi Takashima
- Department of Chemistry, Faculty of Science, Nara Women's University, Nara 630-8506, Japan
| | - Tsumoru Morimoto
- Graduate School of Materials Science, Nara Institute of Science and Technology (NAIST), Takayama, Ikoma, Nara 630-0192, Japan
| | - Akiya Ogawa
- Department of Applied Chemistry, Graduate School of Engineering, Osaka Prefecture University, Gakuen-cho 1-1, Nakaku, Sakai, Osaka 599-8531, Japan
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9
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Shurupova OV, Sterligov GK, Rasskazova MA, Drokin EA, Lysenko AN, Rzhevskiy SA, Minaeva LI, Topchiy MA, Asachenko AF. One-pot two step synthesis of unsymmetrically substituted indenes from 3,4-diarylbutadiene sulfones. MENDELEEV COMMUNICATIONS 2022. [DOI: 10.1016/j.mencom.2022.07.006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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10
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Yu B, Huang R, Li R, Zhang H, Huang H. Silver-catalyzed chemodivergent assembly of aminomethylated isochromenes and naphthols. Chem Commun (Camb) 2022; 58:3969-3972. [PMID: 35253823 DOI: 10.1039/d2cc00303a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A silver-catalyzed chemodivergent cyclization of alkyne-tethered aldehydes with aminals to aminomethylated 1H-isochromenes and naphthols is described by tuning the reaction conditions. The reaction exhibits broad substrate generality and functional group compatibility. Mechanistic studies have disclosed that the aminomethylated naphthols are generated from the resulting N,O-aminal containing isochromenes via a silver-catalyzed unusual rearrangement process.
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Affiliation(s)
- Bangkui Yu
- Department of Chemistry, School of Chemistry and Material Science, Center for Excellence in Molecular Synthesis of CAS, University of Science and Technology of China, Hefei, 230026, P. R. China.
| | - Renbin Huang
- Department of Chemistry, School of Chemistry and Material Science, Center for Excellence in Molecular Synthesis of CAS, University of Science and Technology of China, Hefei, 230026, P. R. China.
| | - Renren Li
- Department of Chemistry, School of Chemistry and Material Science, Center for Excellence in Molecular Synthesis of CAS, University of Science and Technology of China, Hefei, 230026, P. R. China.
| | - Haocheng Zhang
- Department of Chemistry, School of Chemistry and Material Science, Center for Excellence in Molecular Synthesis of CAS, University of Science and Technology of China, Hefei, 230026, P. R. China.
| | - Hanmin Huang
- Department of Chemistry, School of Chemistry and Material Science, Center for Excellence in Molecular Synthesis of CAS, University of Science and Technology of China, Hefei, 230026, P. R. China. .,State Key Laboratory of Oxo Synthesis and Selective Oxidation, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou, 730000, P. R. China
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11
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Qi Z, Wang S. Chemodivergent Synthesis of Oxazoles and Oxime Ethers Initiated by Selective C-N/C-O Formation of Oximes and Diazo Esters. Org Lett 2021; 23:8549-8553. [PMID: 34618474 DOI: 10.1021/acs.orglett.1c03252] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Chemodivergent reactions of oximes and diazo esters involving Rh-catalyzed [3+2] annulation and photodriven O-H insertion have been developed to generate oxazoles and oxime ethers. A range of aldehyde and ketone oximes reacted with α-diazocarbonyl compounds in a controllable manner in which functional groups, including ketone, ester, amide, ether, thiol ether, silane, alkene, allene, and alkyne groups, were well tolerated.
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Affiliation(s)
- Zhenjie Qi
- State Key Laboratory of Coordination Chemistry, Jiangsu Key Laboratory of Advanced Organic Materials, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210023, China
| | - Shaozhong Wang
- State Key Laboratory of Coordination Chemistry, Jiangsu Key Laboratory of Advanced Organic Materials, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210023, China
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12
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Alachouzos G, Frontier AJ. Cyclization Strategies for the Concurrent Installation of Multiple Quaternary Stereogenic Centers. Isr J Chem 2021. [DOI: 10.1002/ijch.202100014] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Affiliation(s)
- Georgios Alachouzos
- Stratingh Institute of Chemistry Rijksuniversiteit Groningen Nijenborgh 4 9747AG Groningen, The Netherlands
| | - Alison J. Frontier
- Department of Chemistry University of Rochester 414 Hutchison Hall, 100 Trustee Road Rochester New York 14627-0216 United States
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13
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Affiliation(s)
- Suven Das
- Department of Chemistry Rishi Bankim Chandra College for Women Naihati 24-Parganas (N) Pin-743165 India
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14
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Frontier AJ, Sinclair PP. Merging Strategy, Improvisation, and Conversation to Solve Problems in Target Synthesis. Acc Chem Res 2021; 54:1817-1829. [PMID: 33705115 DOI: 10.1021/acs.accounts.0c00804] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Total synthesis has long been depicted as the quest to conquer the structures created by nature, requiring an unflinching, single-minded devotion to the task. The goal is achieved by chemists with grit, strength of will, and a competitive spirit. While there is some truth to this viewpoint, it does not fully capture the rich experiences gained in this research realm. In our lab, strategic planning, improvisation, and conversation have worked in concert to enable progress. This Account summarizes our efforts to synthesize four different bioactive targets: merrilactone A, rocaglamide, phomactin A, and tetrapetalone A. Certain missteps were integral to success in these synthetic projects. As such, we include the hiccups, and their roles in the evolution of the strategies, along with the results that aligned with our expectations.Two of these projects (merrilactone A and rocaglamide) culminated in the total synthesis of the targets. The challenges presented by merrilactone A spawned a new design strategy for pentannulation using Nazarov cyclization chemistry. This work demonstrated that Lewis acid catalysis is often a viable electrocyclization strategy in activated, polarized pentadienyl cation intermediates. We sought to apply the same logic to the rocaglamide target, but precursors we prepared did not behave according to plan. This situation pushed us to adapt our approach to match the innate reactivity of the substrate, resulting in an on-the-spot improvisation that was not only integral to the success of the project but also expanded our understanding of pentadienyl cation chemistry. In the other two projects (phomactin A and tetrapetalone A), we did not complete a total synthesis but did build the polycyclic core of the target. Even though the hetero [4 + 2] cycloaddition plan for assembling the macrocyclic oxadecalin ring system of phomactin A failed, the original experimental design still enabled us to solve the problem. Through a wholly unanticipated series of events, our focus on the oxadecalin ring system primed us for the discovery of a sequential iodoaldol/oxa-Michael sequence, using the original [4 + 2] building blocks. Then, the bridging ring present in phomactin A demanded we implement this sequence in a transannular fashion. Finally, our successful synthesis of the tetrapetalone core was enabled by consultations with others in the community. Each bond formation seemed to require different expertise, and in three separate instances (C-N cross-coupling, diastereoselective ring-closing metathesis, and oxidative dearomatization) synthetic challenges were overcome through conversation and collaboration.In our experience, the amount of creative power we summon during a target synthesis project correlates directly with the magnitude of the structural challenges we face. When reactivity surprises us, we analyze the problem anew, consult with colleagues, and improvise with the tools at hand. The inevitable misbehavior of a complex system is a strong motivating force, and one that has helped to shape our research program for nearly two decades.
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Affiliation(s)
- Alison J. Frontier
- Department of Chemistry, University of Rochester, 120 Trustee Road, Rochester New York 14611, United States
| | - Paul P. Sinclair
- Department of Chemistry, University of Rochester, 120 Trustee Road, Rochester New York 14611, United States
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15
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Amemiya S, Okemoto S, Tsubouchi A, Saito A. Synthesis of α-(aminoethyl)-α,β-enones via alkyne aza-Prins cyclization and their synthetic application to pyrrolidines. Org Biomol Chem 2021; 19:2959-2967. [PMID: 33729258 DOI: 10.1039/d1ob00072a] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
We developed a synthetic method for α-(aminoethyl)-α,β-enones from aryl-substituted homopropargyl sulfonamides and aldehydes, representing the first synthesis of conjugated enones via alkyne aza-Prins cyclization. These products could be converted into pyrrolidines by a formal 5-endo-trig cyclization.
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Affiliation(s)
- Sho Amemiya
- Division of Applied Chemistry, Institute of Engineering, Tokyo University of Agriculture and Technology, 2-24-16 Naka-cho, Koganei, Tokyo 184-8588, Japan.
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16
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Hernandez JJ, Frontier AJ. Synthesis of Spirocyclic Isoindolones Using an Alkynyl aza-Prins/Oxidative halo-Nazarov Cyclization Sequence. Org Lett 2021; 23:1782-1786. [PMID: 33591209 DOI: 10.1021/acs.orglett.1c00191] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
In this report, we describe an alkynyl halo-aza-Prins cyclization of 3-hydroxyisoindolones to prepare aza-Prins products. These Prins adducts undergo oxidation at the 3-isoindolone position after activation of the amide by triflic anhydride and 2-chloropyridine to form a pentadienyl cation capable of undergoing a halo-Nazarov cyclization. Using this methodology, angular-fused N-heterocyclic small molecules with two new rings, two new carbon-carbon bonds, a vinyl halide, and an aza-tertiary stereocenter can be obtained in good yields.
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Affiliation(s)
- Jackson J Hernandez
- Department of Chemistry, University of Rochester, 120 Trustee Road, Rochester, New York 14611, United States
| | - Alison J Frontier
- Department of Chemistry, University of Rochester, 120 Trustee Road, Rochester, New York 14611, United States
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17
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Howlader AH, Diaz K, Mebel AM, Kaiser RI, Wnuk SF. Iodoindenes: Synthesis and application to cross-coupling. Tetrahedron Lett 2020. [DOI: 10.1016/j.tetlet.2020.152427] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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18
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Abstract
The defining feature of the Nazarov cyclization is a 4π-conrotatory electrocyclization, resulting in the stereospecific formation of functionalized cyclopentanones. The reaction provides access to structural motifs that are found in many natural products and drug targets. Harnessing the full potential of the Nazarov cyclization broadens its utility by enabling the development of new methodologies and synthetic strategies. To achieve these goals through efficient cyclization design, it is helpful to think of the reaction as a two-stage process. The first stage involves a 4π-electrocyclization leading to the formation of an allylic cation, and the second stage corresponds to the fate of this cationic intermediate. With a complete understanding of the discrete events that characterize the overall process, one can optimize reactivity and control the selectivity of the different Stage 2 pathways.In this Account, we describe the development of methods that render the Nazarov cyclization catalytic and chemoselective, focusing specifically on advances made in our lab between 2002 and 2015. The initial discovery made in our lab involved reactions of electronically asymmetric ("polarized") substrates, which cyclize efficiently in the catalytic regime using mild Lewis acidic reagents. These cyclizations also exhibit selective eliminative behavior, increasing their synthetic utility. Research directed toward catalytic asymmetric Nazarov cyclization led to the serendipitous discovery of a 4π-cyclization coupled to a well-behaved Wagner-Meerwein rearrangement, representing an underexplored Stage 2 process. With careful choice of promoter and loading, it is possible to access either the rearrangement or the elimination pathway. Additional experimental and computational studies provided an effective model for anticipating the migratory behavior of substiutents in the rearrangements. Problem-solving efforts prompted investigation of alternative methods for generating pentadienyl cation intermediates, including oxidation of allenol ethers and addition of nucleophiles to dienyl diketones. These Nazarov cyclization variants afford cyclopentenone products with vicinal stereogenic centers and a different arrangement of substituents around the ring. A nucleophilic addition/cyclization/elimination sequence can be executed enantioselectively using catalytic amounts of a nonracemic chiral tertiary amine.In summary, the discovery and development of several new variations on the Nazarov electrocyclization are described, along with synthetic applications. This work illustrates how strongly substitution patterns can impact the efficiency of the 4π-electrocyclization (Stage 1), allowing for mild Lewis acid catalysis. Over the course of these studies, we have also identified new ways to access the critical pentadienyl cation intermediates and demonstrated strategies that exploit and control the different cationic pathways available post-electrocyclization (Stage 2 processes). These advances in Nazarov chemistry were subsequently employed in the synthesis of natural product targets such as (±)-merrilactone A, (±)-rocaglamide, and (±)-enokipodin B.
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Affiliation(s)
- Alison J. Frontier
- Department of Chemistry, University of Rochester, Rochester, New York 14627, United States
| | - Jackson J. Hernandez
- Department of Chemistry, University of Rochester, Rochester, New York 14627, United States
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19
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Abstract
An important strategy for the efficient generation of diversity in molecular structures is the utilization of common starting materials in chemodivergent transformations. The most studied solutions for switching the chemoselectivity rely on the catalyst, ligand, additive, solvent, temperature, time, pressure, pH and even small modifications in the substrate. In this review article several processes have been selected such as inter- and intramolecular cyclizations, including carba-, oxa-, thia- and oxazacyclizations promoted mainly by Brønsted or Lewis acids, transition metals and organocatalysts, as well as radical reactions. Catalyst-controlled intra- and intermolecular cyclizations are mainly described to give five- and six-membered rings. Cycloaddition reactions involving (2+2), (3+2), (3+3), (4+1), (4+2), (5+2), (6+2) and (7+2) processes are useful reactions for the synthesis of cyclic systems using organocatalysts, metal catalysts and Lewis acid-controlled processes. Addition reactions mainly of carba- and heteronucleophiles to unsaturated conjugated substrates can give different adducts via metal catalyst-, Lewis acid- and solvent-dependent processes. Carbonylation reactions of amines and phenols are carried out via ligand-controlled transition metal-catalyzed multicomponent processes. Ring-opening reactions starting mainly from cyclopropanols, cyclopropenols and epoxides or aziridines are applied to the synthesis of acyclic versus cyclic products under catalyst-control mainly by Lewis acids. Chemodivergent reduction reactions are performed using dissolving metals, sodium borohydride or hydrogen transfer conditions under solvent control. Oxidation reactions include molecular oxygen under solvent control or using different dioxiranes, as well as chemodivergent palladium catalyzed cross-coupling reactions using boronic acids are applied to aromatic and allenic compounds. Other chemodivergent reactions such as alkylations and allylations under transition metal catalysis, dimerization of acetylenes, bromination of benzylic substrates, and A3-couplings are performed via catalyst- or reaction condition-dependent processes.
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Affiliation(s)
- Irina P Beletskaya
- Chemistry Department, M. V. Lomonosov Moscow University, Leminskie Gory 1, 119992 Moscow, Russia
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20
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Alachouzos G, Holt C, Frontier AJ. Stereochemical Relay through a Cationic Intermediate: Helical Preorganization Dictates Direction of Conrotation in the halo-Nazarov Cyclization. Org Lett 2020; 22:4010-4015. [PMID: 32352794 DOI: 10.1021/acs.orglett.0c01330] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
A stereocontrolled halo-Prins/halo-Nazarov cyclization protocol is reported, where chiral information from a secondary alcohol is relayed through several intermediates yielding halocyclopentene products diastereoselectively. An enantiopure product is obtained when a nonracemic secondary alcohol is used. Experimental and computational studies are described, enabling the design and synthesis of systems that ionize and cyclize with >95% chirality transfer through a mechanism involving the creation and preservation of transient helical chirality in a pentadienyl cation intermediate. First, a diastereoselective alkynyl Prins cyclization is executed to synthesize a conformationally distorted dihydropyran intermediate with a curved backbone and high reactivity. This chiral precursor adopts a specific helical alignment early in the subsequent cationic ionization/halo-Nazarov cyclization process, dictating the direction of conrotation in the electrocyclization. Notably, despite the ablation of an sp3 stereogenic center during ionization, the low halo-Nazarov barrier enables efficient capture of a cationic intermediate with dynamic conformational chirality. The ionization and electrocyclization thus occur with "memory of chirality".
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Affiliation(s)
- Georgios Alachouzos
- Department of Chemistry, University of Rochester, 414 Hutchison Hall, 100 Trustee Road, Rochester, New York 14627-0216, United States
| | - Connor Holt
- Department of Chemistry, University of Rochester, 414 Hutchison Hall, 100 Trustee Road, Rochester, New York 14627-0216, United States
| | - Alison J Frontier
- Department of Chemistry, University of Rochester, 414 Hutchison Hall, 100 Trustee Road, Rochester, New York 14627-0216, United States
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21
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Sultana S, Lee YR. Construction of Halofunctionalized Indenes via a Cascade Prins‐Nazarov Cyclization Promoted by Dual Roles of BX
3. Adv Synth Catal 2020. [DOI: 10.1002/adsc.201901266] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Affiliation(s)
- Sabera Sultana
- School of Chemical EngineeringYeungnam University Gyeongsan 38541 Republic of Korea
| | - Yong Rok Lee
- School of Chemical EngineeringYeungnam University Gyeongsan 38541 Republic of Korea
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22
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Králová P, Maloň M, Pospíšil J, Soural M. Rearrangement of Threonine- and Serine-Based N-(3-Phenylprop-2-yn-1-yl) Sulfonamides Yields Chiral Pyrrolidin-3-ones. J Org Chem 2019; 85:985-993. [DOI: 10.1021/acs.joc.9b02932] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Affiliation(s)
- Petra Králová
- Department of Organic Chemistry, Faculty of Science, Palacký University, Tr. 17 Listopadu 12, 771 46 Olomouc, Czech Republic
| | - Michal Maloň
- JEOL (United Kingdom) Limited, JEOL House, Silver Court, Watchmead, Welwyn Garden City, AL7 1LT Hertfordshire, United Kingdom
| | - Jiří Pospíšil
- Department of Organic Chemistry, Faculty of Science, Palacký University, Tr. 17 Listopadu 12, 771 46 Olomouc, Czech Republic
- Laboratory of Growth Regulators, The Czech Academy of Sciences, Institute of Experimental Botany & Palacký University, Šlechtitelů 27, 78371 Olomouc, Czech Republic
| | - Miroslav Soural
- Department of Organic Chemistry, Faculty of Science, Palacký University, Tr. 17 Listopadu 12, 771 46 Olomouc, Czech Republic
- Institute of Molecular and Translational Medicine, Faculty of Medicine and Dentistry, Palacký University, Hněvotínská 5, 779 00 Olomouc, Czech Republic
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23
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Affiliation(s)
- Antonia Rinaldi
- Dipartimento di Chimica "U. Schiff"; Università degli Studi di Firenze; Via della Lastruccia 13 50019 Sesto F.no Italy
| | - Dina Scarpi
- Dipartimento di Chimica "U. Schiff"; Università degli Studi di Firenze; Via della Lastruccia 13 50019 Sesto F.no Italy
| | - Ernesto G. Occhiato
- Dipartimento di Chimica "U. Schiff"; Università degli Studi di Firenze; Via della Lastruccia 13 50019 Sesto F.no Italy
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24
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Zaky M, Li Z, Morgan TDR, LeFort FM, Boyd RJ, Burnell DJ. Lewis Acid-Mediated Cyclization of Allenyl Aryl Ketones. J Org Chem 2019; 84:13665-13675. [PMID: 31553185 DOI: 10.1021/acs.joc.9b01900] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The cyclization of a series of nonheterocyclic allenyl aryl ketones was examined using boron trifluoride etherate and indium triflate to mediate the reaction. Yields with BF3 were low in most instances due mainly to competitive destruction of the substrates. With In(OTf)3, there was less decomposition, and the yields of the cyclized product were much higher, but only for substrates with electron-donating substituents. Cyclization did not occur without those substituents. A computational study using the ωB97X-D/6-311+G(2d,p)//ωB97X-D/6-31+G(d,p) method confirmed better stability of the σ-complexed substrate by indium(III) and that meta-substituents on the phenyl ring of the substrate significantly influenced the activation barrier of the cyclization, whereas the effect of para-substituents was almost negligible. The computational results supported the idea that the cyclization is a 4π-electrocyclization and not a 5-endo-dig ring closure as had been proposed in the literature.
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Affiliation(s)
- Mariam Zaky
- Department of Chemistry , Dalhousie University , P.O. Box 15000 Halifax , Nova Scotia B3H 4R2 , Canada
| | - Zhe Li
- Department of Chemistry , Dalhousie University , P.O. Box 15000 Halifax , Nova Scotia B3H 4R2 , Canada
| | - Timothy D R Morgan
- Department of Chemistry , Dalhousie University , P.O. Box 15000 Halifax , Nova Scotia B3H 4R2 , Canada
| | - François M LeFort
- Department of Chemistry , Dalhousie University , P.O. Box 15000 Halifax , Nova Scotia B3H 4R2 , Canada
| | - Russell J Boyd
- Department of Chemistry , Dalhousie University , P.O. Box 15000 Halifax , Nova Scotia B3H 4R2 , Canada
| | - D Jean Burnell
- Department of Chemistry , Dalhousie University , P.O. Box 15000 Halifax , Nova Scotia B3H 4R2 , Canada
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25
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Miao M, Jin M, Chen P, Wang L, Zhang S, Ren H. Iron(III)-Mediated Bicyclization of 1,2-Allenyl Aryl Ketones: Assembly of Indanone-Fused Polycyclic Scaffolds and Dibenzo[ a, e]pentalene Derivatives. Org Lett 2019; 21:5957-5961. [PMID: 31298027 DOI: 10.1021/acs.orglett.9b02079] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The rapid construction of three-dimensional fused carbocycles is a key challenge in synthetic chemistry. Herein, an unprecedented and practical tandem Nazarov/oxidative umpolung 4π-ring closure of readily available 1,2-allenyl aryl ketones mediated by iron(III) chloride has been developed, furnishing a new family of indanone-fused molecular architectures in moderate to excellent yields. The indanone-containing blocks can be efficiently converted to unsymmetrical dibenzo[a,e]pentalenes. Significantly, divergent synthetic applications have been achieved to provide densely functionalized polycyclic arrays.
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Affiliation(s)
- Maozhong Miao
- Department of Chemistry , Zhejiang Sci-Tech University , Hangzhou , Zhejiang 310018 , P. R. China
| | - Mengchao Jin
- Department of Chemistry , Zhejiang Sci-Tech University , Hangzhou , Zhejiang 310018 , P. R. China
| | - Panpan Chen
- Department of Chemistry , Zhejiang Sci-Tech University , Hangzhou , Zhejiang 310018 , P. R. China
| | - Lei Wang
- Department of Chemistry , Zhejiang Sci-Tech University , Hangzhou , Zhejiang 310018 , P. R. China
| | - Shouzhi Zhang
- Department of Chemistry , Zhejiang Sci-Tech University , Hangzhou , Zhejiang 310018 , P. R. China
| | - Hongjun Ren
- Department of Chemistry , Zhejiang Sci-Tech University , Hangzhou , Zhejiang 310018 , P. R. China
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