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Wakabayashi R, Wang S, Kurogi T, Yorimitsu H. Arylation of benzazoles at the 4 positions by activation of their 2-methylsulfinyl groups. Chem Commun (Camb) 2024; 60:6166-6169. [PMID: 38804671 DOI: 10.1039/d4cc01918k] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/29/2024]
Abstract
Treatment of 2-methylsulfinylbenzazoles with triflic anhydride in the presence of phenols yields the corresponding 4-(p-hydroxyphenyl)-2-methylsulfanylbenzazoles. This regioselective dehydrative C-H/C-H coupling arylation represents a rare example of functionalizations on the benzene rings of benzo-fused azoles.
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Affiliation(s)
- Ryota Wakabayashi
- Department of Chemistry Graduate School of Science, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan.
| | - Shuo Wang
- Department of Chemistry Graduate School of Science, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan.
| | - Takashi Kurogi
- Department of Chemistry Graduate School of Science, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan.
| | - Hideki Yorimitsu
- Department of Chemistry Graduate School of Science, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan.
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2
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Ye S, Wang H, Liang G, Hu Z, Wan K, Zhang L, Peng B. ortho-Cyanomethylation of aryl fluoroalkyl sulfoxides via a sulfonium-Claisen rearrangement. Org Biomol Chem 2024; 22:1495-1499. [PMID: 38293848 DOI: 10.1039/d3ob02102e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2024]
Abstract
We hereby report the ortho-cyanomethylation of aryl fluoroalkyl sulfoxides with acetonitrile through a sulfonium-Claisen-type rearrangement. This reaction enables the incorporation of two valuable functional groups, such as the cyanomethyl group and the fluoroalkylthio group, into arenes. Remarkably, fluoroalkylthio groups, such as SCFH2 and SCF2H, bearing active hydrogen, are well tolerated by the reaction. The success of the reaction relies on the use of an excess amount of acetonitrile and the electronegative effect of fluoroalkyl substituents, both of which promote the electrophilic assembly of sulfoxides with acetonitrile. Consequently, the sulfonium-Claisen rearrangement reaction tolerates a wide variety of fluoroalkyl sulfoxides bearing functional groups including halides, nitriles, ketones, sulfones, and amides, which are appealing for subsequent elaboration and exploration.
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Affiliation(s)
- Sheng Ye
- Key Laboratory of the Ministry of Education for Advanced Catalysis Materials, Zhejiang Normal University, Jinhua 321004, China.
| | - Huanhuan Wang
- Key Laboratory of the Ministry of Education for Advanced Catalysis Materials, Zhejiang Normal University, Jinhua 321004, China.
| | - Guoqing Liang
- Key Laboratory of the Ministry of Education for Advanced Catalysis Materials, Zhejiang Normal University, Jinhua 321004, China.
| | - Zhengkai Hu
- Key Laboratory of the Ministry of Education for Advanced Catalysis Materials, Zhejiang Normal University, Jinhua 321004, China.
| | - Kun Wan
- Key Laboratory of the Ministry of Education for Advanced Catalysis Materials, Zhejiang Normal University, Jinhua 321004, China.
| | - Lei Zhang
- Key Laboratory of the Ministry of Education for Advanced Catalysis Materials, Zhejiang Normal University, Jinhua 321004, China.
| | - Bo Peng
- Key Laboratory of the Ministry of Education for Advanced Catalysis Materials, Zhejiang Normal University, Jinhua 321004, China.
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3
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Hu M, Liang Y, Ru L, Ye S, Zhang L, Huang X, Bao M, Kong L, Peng B. Defluorinative Multi-Functionalization of Fluoroaryl Sulfoxides Enabled by Fluorine-Assisted Temporary Dearomatization. Angew Chem Int Ed Engl 2023; 62:e202306914. [PMID: 37455262 DOI: 10.1002/anie.202306914] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2023] [Revised: 07/12/2023] [Accepted: 07/13/2023] [Indexed: 07/18/2023]
Abstract
Owing to its unique physical properties, fluorine is often used to open up new reaction channels. In this report, we establish a cooperation of [5,5]-rearrangement and fluorine-assisted temporary dearomatization for arene multi-functionalization. Specifically, the [5,5]-rearrangement of fluoroaryl sulfoxides with β,γ-unsaturated nitriles generates an intriguing dearomatized sulfonium species which is short-lived but exhibits unusually high electrophilicity and thus can be instantly trapped by nucleophiles and dienes at a remarkably low temperature (-95 °C) to produce four types of valuable multi-functionalized benzenes, respectively, involving appealing processes of defluorination, desulfurization, and sulfur shift. Mechanistic studies indicate that the use of fluorine on arenes not only circumvents the generally inevitable [3,3]-rearrangement but also impedes the undesired rearomatization process, thus provides a precious space for constructing and elaborating the temporarily dearomatized fluorinated sulfonium species.
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Affiliation(s)
- Mengjie Hu
- Key Laboratory of the Ministry of Education for Advanced Catalysis Materials, Zhejiang Normal University, Jinhua, 321004, China
- State Key Laboratory of Fine Chemicals, Dalian University of Technology, Dalian, 116023, China
| | - Yuchen Liang
- Key Laboratory of the Ministry of Education for Advanced Catalysis Materials, Zhejiang Normal University, Jinhua, 321004, China
| | - Liying Ru
- Key Laboratory of the Ministry of Education for Advanced Catalysis Materials, Zhejiang Normal University, Jinhua, 321004, China
| | - Sheng Ye
- Key Laboratory of the Ministry of Education for Advanced Catalysis Materials, Zhejiang Normal University, Jinhua, 321004, China
| | - Lei Zhang
- Key Laboratory of the Ministry of Education for Advanced Catalysis Materials, Zhejiang Normal University, Jinhua, 321004, China
| | - Xin Huang
- Key Laboratory of the Ministry of Education for Advanced Catalysis Materials, Zhejiang Normal University, Jinhua, 321004, China
| | - Ming Bao
- State Key Laboratory of Fine Chemicals, Dalian University of Technology, Dalian, 116023, China
| | - Lichun Kong
- Key Laboratory of the Ministry of Education for Advanced Catalysis Materials, Zhejiang Normal University, Jinhua, 321004, China
| | - Bo Peng
- Key Laboratory of the Ministry of Education for Advanced Catalysis Materials, Zhejiang Normal University, Jinhua, 321004, China
- Key Laboratory of Chemical Biology & Traditional Chinese Medicine Research (Ministry of Education), Hunan Normal University, Changsha, 410081, China
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4
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Bisht R, Popescu MV, He Z, Ibrahim AM, Crisenza GEM, Paton RS, Procter DJ. Metal-Free Arylation of Benzothiophenes at C4 by Activation as their Benzothiophene S-Oxides. Angew Chem Int Ed Engl 2023; 62:e202302418. [PMID: 37000422 PMCID: PMC10953450 DOI: 10.1002/anie.202302418] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2023] [Revised: 03/29/2023] [Accepted: 03/31/2023] [Indexed: 04/01/2023]
Abstract
Benzothiophenes, activated by oxidation to the corresponding S-oxides, undergo C-H/C-H-type coupling with phenols to give C4 arylation products. While an electron-withdrawing group at C3 of the benzothiophene is important, the process operates without a directing group and a metal catalyst, thus rendering it compatible with sensitive functionalities-e.g. halides and formyl groups. Quantum chemical calculations suggest a formal stepwise mechanism involving heterolytic cleavage of an aryloxysulfur species to give a π-complex of the corresponding benzothiophene and a phenoxonium cation. Subsequent addition of the phenoxonium cation to the C4 position of the benzothiophene is favored over the addition to C3; Fukui functions predict that the major regioisomer is formed at the more electron-rich position between C3 and C4. Varied selective manipulation of the benzothiophene products showcase the synthetic utility of the metal-free arylation process.
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Affiliation(s)
- Ranjana Bisht
- Department of ChemistryUniversity of ManchesterOxford RoadManchesterM13 9PLUK
| | - Mihai V. Popescu
- Department of ChemistryColorado State UniversityCenter AveFort CollinsCO80523USA
| | - Zhen He
- Department of ChemistryUniversity of ManchesterOxford RoadManchesterM13 9PLUK
| | - Ameer M. Ibrahim
- Department of ChemistryUniversity of ManchesterOxford RoadManchesterM13 9PLUK
| | | | - Robert S. Paton
- Department of ChemistryColorado State UniversityCenter AveFort CollinsCO80523USA
| | - David J. Procter
- Department of ChemistryUniversity of ManchesterOxford RoadManchesterM13 9PLUK
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Li X, Li Y, Yang J, Shi H, Ai Z, Han C, He J, Du Y. Synthesis of 3-SCF 2H-/3-SCF 3-chromones via Interrupted Pummerer Reaction/Intramolecular Cyclization Mediated by Difluoromethyl or Trifluoromethyl Sulfoxide and Tf 2O. Org Lett 2022; 24:7216-7221. [PMID: 36148991 DOI: 10.1021/acs.orglett.2c03017] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The reaction of alkynyl aryl ketones bearing an o-methoxy group with difluoromethyl sulfoxide in the presence of Tf2O was found to conveniently afford the corresponding 3-SCF2H-substituted chromones. The combining use of difluoromethyl sulfoxide/Tf2O could represent the first reagents system that can introduce the biologically important SCF2H moiety under base-free conditions via an interrupted Pummerer reaction. The same protocol could also be applied to the synthesis of 3-SCF3-substituted chromones by replacing difluoromethyl sulfoxide with trifluoromethyl sulfoxide and CH3CN with toluene.
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Affiliation(s)
- Xuemin Li
- Tianjin Key Laboratory for Modern Drug Delivery & High-Efficiency, School of Pharmaceutical Science and Technology, Tianjin University, Tianjin 300072, China
| | - Yue Li
- State Key Laboratory of Metastable Materials Science and Technology, Hebei Key Laboratory of Nano-biotechnology, Yanshan University, Qinhuangdao 066004, P.R. China
| | - Jingyue Yang
- State Key Laboratory of Metastable Materials Science and Technology, Hebei Key Laboratory of Nano-biotechnology, Yanshan University, Qinhuangdao 066004, P.R. China
| | - Haofeng Shi
- Tianjin Key Laboratory for Modern Drug Delivery & High-Efficiency, School of Pharmaceutical Science and Technology, Tianjin University, Tianjin 300072, China
| | - Zhenkang Ai
- Tianjin Key Laboratory for Modern Drug Delivery & High-Efficiency, School of Pharmaceutical Science and Technology, Tianjin University, Tianjin 300072, China
| | - Chi Han
- Tianjin Key Laboratory for Modern Drug Delivery & High-Efficiency, School of Pharmaceutical Science and Technology, Tianjin University, Tianjin 300072, China
| | - Jiaxin He
- Tianjin Key Laboratory for Modern Drug Delivery & High-Efficiency, School of Pharmaceutical Science and Technology, Tianjin University, Tianjin 300072, China
| | - Yunfei Du
- Tianjin Key Laboratory for Modern Drug Delivery & High-Efficiency, School of Pharmaceutical Science and Technology, Tianjin University, Tianjin 300072, China
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Liang Y, Peng B. Revisiting Aromatic Claisen Rearrangement Using Unstable Aryl Sulfonium/Iodonium Species: The Strategy of Breaking Up the Whole into Parts. Acc Chem Res 2022; 55:2103-2122. [PMID: 35861672 DOI: 10.1021/acs.accounts.2c00263] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
ConspectusSince Ludwig Claisen's discovery of the sigmatropic rearrangement of allyl aryl ethers in 1912, aromatic Claisen rearrangement has continuously attracted the attention of both experimental and theoretical chemists. Over more than a century of growth, this protocol has proven to be a practical and powerful synthetic tool in many aspects. However, the reaction scope has long been limited to aryl ethers and their S or N analogs until the serendipitous discovery of aromatic iodonium-Claisen rearrangement by Oh et al. in 1988 and the development of aromatic sulfonium-Claisen rearrangement by Kita et al. in 2004. Unlike traditional Claisen rearrangements, these hypervalent-bonding-based Claisen-type rearrangements can be performed by simply mixing electrophilically activated aryl sulfoxides/iodanes with certain nucleophiles to directly deliver rearrangement products. In addition to the simple operation, remarkable features, such as readily available substrates, valuable products and intriguing rearrangement patterns, have led to a dramatic resurgence of this rearrangement chemistry.In this Account, we summarize our recent works on developing new aromatic rearrangement modes using sulfonium/iodonium reagents. Interestingly, the program started with an accidental discovery that aryl sulfoxides could be coupled with alkyl nitriles in the presence of Tf2O and base. Mechanistic studies reveal that the reaction proceeds in three major steps, including the Tf2O-triggered assembly of both coupling partners, base-promoted deprotonation of in situ-generated aryl sulfonium-imine species leading to a key rearrangement precursor called aryl sulfonium-ketenimine species, and subsequent facile and rapid [3,3]-rearrangement. On the basis of the mechanistic underpinning, we divided the one-step operation into two steps called the "assembly/deprotonation" protocol for constructing unstable rearrangement precursors. Most notably, the switch from the commonly used one-step to mechanism-based multiple-step manipulation, which can be termed "breaking up the whole into parts", not only enables the independent control of each step of the reaction, thus significantly expanding the accessible synthetic scope, but also raises opportunities for developing new rearrangement patterns. For example, the "assembly/deprotonation" protocol has also been applied to the development of [5,5]-rearrangement of aryl sulfoxides and the asymmetric rearrangement of aryl iodanes, thus enabling the unprecedented regio- and stereocontrol of the rearrangement process. Furthermore, the "breaking up the whole into parts" thinking triggered us to merge the Morita-Baylis-Hillman (MBH) reaction into the rearrangement process to accomplish Z-selective MBH-type [3,3]-rearrangement of α,β-unsaturated nitriles and E-selective MBH-type [3,3]-rearrangement of α,β-unsaturated 2-oxazolines, which expands the scope of rearrangement partners to include α,β-unsaturated carbonyls. In addition, the impressive rapidity of the rearrangement process found in our initial discovery has also been recognized as a congestion-acceleration effect, which was further utilized to forge the rapid ortho-cyanoalkylative rearrangement of aryl iodanes, and thus leading to the first dearomatization of aryl iodanes. We anticipate that our protocols and ideas behind the methods will be complementary to the traditional thinking of the aromatic Claisen rearrangement.
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Affiliation(s)
- Yuchen Liang
- Key Laboratory of the Ministry of Education for Advanced Catalysis Materials, Zhejiang Normal University, 688 Yingbin Road, Jinhua321004, China
| | - Bo Peng
- Key Laboratory of the Ministry of Education for Advanced Catalysis Materials, Zhejiang Normal University, 688 Yingbin Road, Jinhua321004, China
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