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Konwar M, Hazarika N, Sarmah BK, Das A. Ruthenium(II)-Catalyzed Oxidative Annulation of Imidazo[1,5-a]quinolin-2-iums Salts and Internal Alkynes via C-H Bond Activation. Chemistry 2024; 30:e202401133. [PMID: 38593238 DOI: 10.1002/chem.202401133] [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: 03/20/2024] [Revised: 04/06/2024] [Accepted: 04/09/2024] [Indexed: 04/11/2024]
Abstract
Ruthenium(II)-catalyzed synthesis of π-conjugated fused imidazo[1,5-a]quinolin-2-ium derivatives have been achieved via C-H activation of quinoline-functionalized NHC (NHC=N-heterocyclic carbene) and oxidative coupling with internal alkynes. The reaction occurred with high efficiency, broad substrate scope, tolerates a wide range of functional groups and utilized into a gram-scale. Synthetic applications of the coupled product have been exemplified in the late-stage derivatization of various highly functionalized scaffolds. Moreover, most of the annulated products exhibit intense fluorescence and have potential applications in optoelectronic devices. Mechanistic studies have provided insights into the spectroscopic characterization of key five-membered ruthenacycle intermediate and Ru(0) sandwich species. Based on several control experiments, deuterium-kinetic isotope effect, and thermodynamic activation parameters the mechanistic finding demonstrated that fused imidazo-[1,5-a]quinolin-2-ium C(2)-H bond cleavage is the rate-determining step and ruling out the possibility of reductive elimination for controlling the rate of reaction.
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Affiliation(s)
- Monuranjan Konwar
- Department of Chemistry, Indian Institute of Technology Guwahati, Guwahati, 781039, Assam, India
| | - Nitumoni Hazarika
- Department of Chemistry, Indian Institute of Technology Guwahati, Guwahati, 781039, Assam, India
| | - Bikash Kumar Sarmah
- Department of Chemistry, Indian Institute of Technology Guwahati, Guwahati, 781039, Assam, India
- Department of Chemistry, Sonari College, Charaideo, 785690, Assam, India
| | - Animesh Das
- Department of Chemistry, Indian Institute of Technology Guwahati, Guwahati, 781039, Assam, India
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Konwar M, Hazarika N, Das A. Ru/O 2-Catalyzed Oxidative C-H Activation/Alkyne Annulation Using Quinoline-Functionalized NHC as a Directing and Functionalizable Group. Org Lett 2024; 26:2965-2970. [PMID: 38593400 DOI: 10.1021/acs.orglett.4c00542] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/11/2024]
Abstract
The ruthenium/O2-catalyzed oxidative annulation reaction of imidazo[1,5-a]quinolin-2-ium salts with alkynes via N-heterocyclic carbene-directed C-H activation to obtain π-conjugated fused imidazo[1,5-a]quinolin-2-ium derivatives is reported. Molecular oxygen has been explored as an economic and clean oxidant and an alternative to metal oxidants. The current protocol exhibits a wide range of substrate scope including bioactive (±)-α-tocopherol derivatives. Moreover, most of the annulated products show strong fluorescence properties, indicating their potential for making new light-emitting materials.
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Affiliation(s)
- Monuranjan Konwar
- Department of Chemistry, Indian Institute of Technology Guwahati, Guwahati-781039, Assam India
| | - Nitumoni Hazarika
- Department of Chemistry, Indian Institute of Technology Guwahati, Guwahati-781039, Assam India
| | - Animesh Das
- Department of Chemistry, Indian Institute of Technology Guwahati, Guwahati-781039, Assam India
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Ma Q, Shi Y, Wang D. Phosphonium Salt-Promoted C2-H Functionalization of Heterocyclic N-Oxides. Org Lett 2023; 25:9181-9185. [PMID: 38117207 DOI: 10.1021/acs.orglett.3c03742] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2023]
Abstract
We report the development of a phosphonium salt as a remarkable activating agent that enables the direct conversion of C2-H bonds of a variety of heterocyclic N-oxides into C2-N, C2-O, or C2-S bonds with high efficiency. The phosphonium salt was prepared on a >150 g scale in a single step and is tolerant of multiple functionalities.
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Affiliation(s)
- Qian Ma
- State Key Laboratory of Chemistry and Utilization of Carbon Based Energy Resources, College of Chemistry, Xinjiang University, Urumqi 830017, Xinjiang, China
| | - Yuze Shi
- Institute of Materia Medica, Xinjiang University, Urumqi 830017, Xinjiang, China
| | - Dong Wang
- State Key Laboratory of Chemistry and Utilization of Carbon Based Energy Resources, College of Chemistry, Xinjiang University, Urumqi 830017, Xinjiang, China
- Institute of Materia Medica, Xinjiang University, Urumqi 830017, Xinjiang, China
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Roy S, Panja S, Sahoo SR, Chatterjee S, Maiti D. Enroute sustainability: metal free C-H bond functionalisation. Chem Soc Rev 2023; 52:2391-2479. [PMID: 36924227 DOI: 10.1039/d0cs01466d] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/18/2023]
Abstract
The term "C-H functionalisation" incorporates C-H activation followed by its transformation. In a single line, this can be defined as the conversion of carbon-hydrogen bonds into carbon-carbon or carbon-heteroatom bonds. The catalytic functionalisation of C-H bonds using transition metals has emerged as an atom-economical technique to engender new bonds without activated precursors which can be considered as a major drawback while attempting large-scale synthesis. Replacing the transition-metal-catalysed approach with a metal-free strategy significantly offers an alternative route that is not only inexpensive but also environmentally benign to functionalize C-H bonds. Recently metal free synthetic approaches have been flourishing to functionalize C-H bonds, motivated by the search for greener, cost-effective, and non-toxic catalysts. In this review, we will highlight the comprehensive and up-to-date discussion on recent examples of ground-breaking research on green and sustainable metal-free C-H bond functionalisation.
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Affiliation(s)
- Sayan Roy
- Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai-400076, India.
| | - Subir Panja
- Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai-400076, India.
| | - Sumeet Ranjan Sahoo
- Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai-400076, India.
| | - Sagnik Chatterjee
- Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai-400076, India.
| | - Debabrata Maiti
- Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai-400076, India. .,Department of Interdisciplinary Program in Climate Studies, Indian Institute of Technology Bombay, Powai, Mumbai, 400076, India
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Polimera SR, Ilangovan A, Meanwell NA, Subbaiah MAM. Synthetic Access to α-Oxoketene Aminals by the Nucleophilic Addition of Enol Silane-Derived Palladium(II) Enolates to Carbodiimides. J Org Chem 2022; 87:14778-14792. [PMID: 36285601 DOI: 10.1021/acs.joc.2c02107] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Synthetically important α-oxoketene aminal intermediates can now be accessed from readily available and inexpensive carbodiimides as starting materials via the nucleophilic addition of palladium enolates derived from enol silane precursors. This operationally simple method features mild reaction conditions, including open air atmosphere, ligand-free metal catalysis, broad substrate scope, and multi-gram scalability. Select synthetic applications that take advantage of the enamine character of α-oxoketene aminals and involve C-nucleophilic additions to electrophilic systems, including an α,β-unsaturated ester, an azo dicarboxylate, an aralkyl halide, and an aldehyde, are demonstrated.
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Affiliation(s)
- Subba Rao Polimera
- Department of Medicinal Chemistry, Biocon Bristol Myers Squibb R&D Centre, Biocon Park, Bommasandra IV Phase, Jigani Link Road, Bangalore, Karnataka 560099, India.,Department of Chemistry, Bharathidasan University, Palkalaiperur, Thiruchirapalli, Tamil Nadu 620024, India
| | - Andivelu Ilangovan
- Department of Chemistry, Bharathidasan University, Palkalaiperur, Thiruchirapalli, Tamil Nadu 620024, India
| | - Nicholas A Meanwell
- Department of Small Molecule Drug Discovery, Bristol Myers Squibb Research and Early Development, P.O. Box 4000, Princeton, New Jersey 08543-4000, United States
| | - Murugaiah A M Subbaiah
- Department of Medicinal Chemistry, Biocon Bristol Myers Squibb R&D Centre, Biocon Park, Bommasandra IV Phase, Jigani Link Road, Bangalore, Karnataka 560099, India
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Sarmah BK, Konwar M, Das A. Copper-Catalyzed Oxidative Dehydrogenative Reaction of Quinoline- N-Oxides with Donor-Acceptor Cyclopropanes: Installation of a Tertiary Alkyl Motif at C2 Position. Org Lett 2021; 23:8390-8395. [PMID: 34633204 DOI: 10.1021/acs.orglett.1c03115] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
A copper-catalyzed oxidative dehydrogenative reaction of quinoline N-oxides with donor-acceptor cyclopropanes has been demonstrated to construct C2-alkylated quinolines containing a γ-keto diester motif. The use of molecular oxygen as an oxidant, excellent site-selectivity, and good functional group tolerance are the important features in this process. The preliminary mechanistic studies demonstrate that the catalyst plays a dual role as a Lewis acid and a redox catalyst.
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Affiliation(s)
- Bikash Kumar Sarmah
- Department of Chemistry, Indian Institute of Technology Guwahati, Guwahati, Assam 781039, India
| | - Monuranjan Konwar
- Department of Chemistry, Indian Institute of Technology Guwahati, Guwahati, Assam 781039, India
| | - Animesh Das
- Department of Chemistry, Indian Institute of Technology Guwahati, Guwahati, Assam 781039, India
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