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Zubčić G, You J, Zott FL, Ashirbaev SS, Kolympadi Marković M, Bešić E, Vrček V, Zipse H, Šakić D. Regioselective Rearrangement of Nitrogen- and Carbon-Centered Radical Intermediates in the Hofmann-Löffler-Freytag Reaction. J Phys Chem A 2024; 128:2574-2583. [PMID: 38516723 PMCID: PMC11000220 DOI: 10.1021/acs.jpca.3c07892] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2023] [Revised: 03/06/2024] [Accepted: 03/06/2024] [Indexed: 03/23/2024]
Abstract
The Hofmann-Löffler-Freytag (HLF) reaction serves as a late-stage functionalization technique for generating pyrrolidine heterocyclic ring systems. Contemporary HLF protocols utilize in situ halogenated sulfonamides as precursors in the radical-mediated rearrangement cycle. Despite its well-established reaction mechanism, experiments toward the detection of radical intermediates using EPR techniques have only recently been attempted. However, the obtained spectra lack the distinct features of the N-centered radicals expected for the employed reactants. This paper presents phenylbutylnitrone spin-trapped C-centered and N-centered radicals, generated via light irradiation from N-halogen-tosyl-sulfonamide derivatives and detected using EPR spectroscopy. NMR spectroscopy and DFT calculations are used to explain the observed regioselectivity of the HLF reaction.
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Affiliation(s)
- Gabrijel Zubčić
- Faculty
of Pharmacy and Biochemistry, University
of Zagreb, Ante Kovačića 1, 10000 Zagreb, Croatia
| | - Jiangyang You
- Division
of Physical Chemistry, Rud̵er Bošković
Institute, Bijenička Cesta 54, 10000 Zagreb, Croatia
| | - Fabian L. Zott
- Department
of Chemistry, Ludwig-Maximilians-Universität
München, Butenandtstrasse 5-13, D-81377 München, Germany
| | - Salavat S. Ashirbaev
- Department
of Chemistry, Ludwig-Maximilians-Universität
München, Butenandtstrasse 5-13, D-81377 München, Germany
| | - Maria Kolympadi Marković
- Faculty
of Physics, and Centre for Micro- and Nanosciences and Technologies, University of Rijeka, Radmile Matejčić 2, 51000 Rijeka, Croatia
| | - Erim Bešić
- Faculty
of Pharmacy and Biochemistry, University
of Zagreb, Ante Kovačića 1, 10000 Zagreb, Croatia
| | - Valerije Vrček
- Faculty
of Pharmacy and Biochemistry, University
of Zagreb, Ante Kovačića 1, 10000 Zagreb, Croatia
| | - Hendrik Zipse
- Department
of Chemistry, Ludwig-Maximilians-Universität
München, Butenandtstrasse 5-13, D-81377 München, Germany
| | - Davor Šakić
- Faculty
of Pharmacy and Biochemistry, University
of Zagreb, Ante Kovačića 1, 10000 Zagreb, Croatia
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Constantinou CT, Gkizis PL, Lagopanagiotopoulou OTG, Skolia E, Nikitas NF, Triandafillidi I, Kokotos CG. Photochemical Aminochlorination of Alkenes without the Use of an External Catalyst. Chemistry 2023; 29:e202301268. [PMID: 37254681 DOI: 10.1002/chem.202301268] [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: 04/21/2023] [Revised: 05/25/2023] [Accepted: 05/30/2023] [Indexed: 06/01/2023]
Abstract
The niche field of photochemistry offers opportunities that are not found in "traditional" ground state chemical pathways. Aminochlorinated derivatives are an interesting family of 1,2-difunctionalised compounds that provide access to a variety of natural products and pharmaceutical active substances. A practical, catalyst-free chloroamination protocol is described herein, providing access to intermediates of great importance, utilising mild and photochemical reaction conditions (370 nm), where N-chlorosulfonamides are used as both nitrogen and chlorine sources. A wide variety of olefins, decorated with a plethora of functional groups, was tested providing excellent results (28 examples, 18-88 % yield). Mechanistic studies (UV-Vis, control experiments and quantum yield measurement) were also performed.
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Affiliation(s)
- Constantinos T Constantinou
- Laboratory of Organic Chemistry, Department of Chemistry, National and Kapodistrian University of Athens, 15771, Panepistimiopolis, Athens, Greece
| | - Petros L Gkizis
- Laboratory of Organic Chemistry, Department of Chemistry, National and Kapodistrian University of Athens, 15771, Panepistimiopolis, Athens, Greece
| | - Olga Thomais G Lagopanagiotopoulou
- Laboratory of Organic Chemistry, Department of Chemistry, National and Kapodistrian University of Athens, 15771, Panepistimiopolis, Athens, Greece
| | - Elpida Skolia
- Laboratory of Organic Chemistry, Department of Chemistry, National and Kapodistrian University of Athens, 15771, Panepistimiopolis, Athens, Greece
| | - Nikolaos F Nikitas
- Laboratory of Organic Chemistry, Department of Chemistry, National and Kapodistrian University of Athens, 15771, Panepistimiopolis, Athens, Greece
| | - Ierasia Triandafillidi
- Laboratory of Organic Chemistry, Department of Chemistry, National and Kapodistrian University of Athens, 15771, Panepistimiopolis, Athens, Greece
| | - Christoforos G Kokotos
- Laboratory of Organic Chemistry, Department of Chemistry, National and Kapodistrian University of Athens, 15771, Panepistimiopolis, Athens, Greece
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Williams PJH, Boustead GA, Heard DE, Seakins PW, Rickard AR, Chechik V. New Approach to the Detection of Short-Lived Radical Intermediates. J Am Chem Soc 2022; 144:15969-15976. [PMID: 36001076 PMCID: PMC9460783 DOI: 10.1021/jacs.2c03618] [Citation(s) in RCA: 16] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
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We report a new general method for trapping short-lived
radicals,
based on a homolytic substitution reaction SH2′.
This departure from conventional radical trapping by addition or radical–radical
cross-coupling results in high sensitivity, detailed structural information,
and general applicability of the new approach. The radical traps in
this method are terminal alkenes possessing a nitroxide leaving group
(e.g., allyl-TEMPO derivatives). The trapping process
thus yields stable products which can be stored and subsequently analyzed
by mass spectrometry (MS) supported by well-established techniques
such as isotope exchange, tandem MS, and high-performance liquid chromatography-MS.
The new method was applied to a range of model radical reactions in
both liquid and gas phases including a photoredox-catalyzed thiol–ene
reaction and alkene ozonolysis. An unprecedented range of radical
intermediates was observed in complex reaction mixtures, offering
new mechanistic insights. Gas-phase radicals can be detected at concentrations
relevant to atmospheric chemistry.
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Affiliation(s)
- Peter J H Williams
- Department of Chemistry, University of York, Heslington, York YO10 5DD, U.K
| | | | - Dwayne E Heard
- School of Chemistry, University of Leeds, Leeds LS2 9JT, U.K
| | - Paul W Seakins
- School of Chemistry, University of Leeds, Leeds LS2 9JT, U.K
| | - Andrew R Rickard
- Department of Chemistry, University of York, Heslington, York YO10 5DD, U.K.,National Centre for Atmospheric Science, University of York, Heslington, York YO10 5DD, U.K
| | - Victor Chechik
- Department of Chemistry, University of York, Heslington, York YO10 5DD, U.K
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