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Crawford R, Baumann M. Telescoped Flow Synthesis of Azacyclic Scaffolds Exploiting the Chromoselective Photolysis of Vinyl Azides and Azirines. Chemistry 2024; 30:e202401491. [PMID: 38716703 DOI: 10.1002/chem.202401491] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2024] [Indexed: 07/07/2024]
Abstract
An efficient chromoselective photochemical process is presented for the synthesis of 2H-azirines and 1,3-diazabicylo[3.1.0]hex-3-enes from readily available vinyl azides. The method exploits continuous flow photochemistry to enable the safe consumption of the hazardous azide group and provides uniform irradiation using high-power LEDs at 365-450 nm. Additionally, a scaled telescoped process has been developed providing access to drug-like 1,6-dihydropyrimidines and pyrimidines via integrated ring-expansion and oxidation reactions. Given the prevalence of various azacyclic targets in pharmaceutical, agrochemical and materials applications it is anticipated that this methodology will enable further exploitations of these important scaffolds.
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Affiliation(s)
- Ruairi Crawford
- University College Dublin, School of Chemistry, Science Centre South, D04 N2E5, Dublin, Ireland
| | - Marcus Baumann
- University College Dublin, School of Chemistry, Science Centre South, D04 N2E5, Dublin, Ireland
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2
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Zhang L, You M, Ban X, Zhao X, Yin Y, Cao S, Jiang Z. Visible light-driven dearomative ring expansion of (aza)arenes to access dihydrofuran-based polycyclic compounds. Chem Sci 2024; 15:8828-8834. [PMID: 38873084 PMCID: PMC11168080 DOI: 10.1039/d4sc00748d] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2024] [Accepted: 05/04/2024] [Indexed: 06/15/2024] Open
Abstract
The dearomative expansion of aromatic rings has long been pursued by chemists due to its potential to provide tractable approaches for synthesizing valuable non-aromatic molecules. To circumvent the conventional use of hazardous and unstable diazo compounds, photochemical synthesis has recently emerged as a promising platform. However, protocols that can effectively handle both arenes and azaarenes remain scarce. Herein, we introduce a generic strategy that efficiently converts β-(aza)aryl-β-substituted enones into biologically significant cycloheptatriene derivatives, including their aza-variants. This method allows for the easy modulation of diverse functional groups on the product and demonstrates a wide substrate scope, evidenced by its excellent tolerance to various drug motifs and good compatibility with five-membered azaarenes undergoing ring expansion. Moreover, DFT calculations of plausible mechanisms have motivated the implementation of an important cascade diradical recombination strategy for 1,3-dienones, thus facilitating the synthesis of valuable 2-oxabicyclo[3.1.0]hex-3-ene derivatives.
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Affiliation(s)
- Linghong Zhang
- Key Laboratory of Natural Medicine and Immuno-Engineering of Henan Province, Henan University Kaifeng Henan P. R. China 475004
| | - Mengdi You
- School of Chemistry and Chemical Engineering, Pingyuan Laboratory, Henan Normal University Xinxiang Henan P. R. China 453007
| | - Xu Ban
- School of Chemistry and Chemical Engineering, Pingyuan Laboratory, Henan Normal University Xinxiang Henan P. R. China 453007
| | - Xiaowei Zhao
- Key Laboratory of Natural Medicine and Immuno-Engineering of Henan Province, Henan University Kaifeng Henan P. R. China 475004
| | - Yanli Yin
- School of Chemistry and Chemical Engineering, Pingyuan Laboratory, Henan Normal University Xinxiang Henan P. R. China 453007
| | - Shanshan Cao
- School of Chemistry and Chemical Engineering, Pingyuan Laboratory, Henan Normal University Xinxiang Henan P. R. China 453007
| | - Zhiyong Jiang
- Key Laboratory of Natural Medicine and Immuno-Engineering of Henan Province, Henan University Kaifeng Henan P. R. China 475004
- School of Chemistry and Chemical Engineering, Pingyuan Laboratory, Henan Normal University Xinxiang Henan P. R. China 453007
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Donnelly K, Baumann M. Advances in the Continuous Flow Synthesis of 3- and 4-Membered Ring Systems. Chemistry 2024:e202400758. [PMID: 38564288 DOI: 10.1002/chem.202400758] [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: 02/23/2024] [Revised: 03/30/2024] [Accepted: 04/02/2024] [Indexed: 04/04/2024]
Abstract
Small carbo- and heterocyclic ring systems have experienced a significant increase in importance in recent years due to their relevance in modern pharmaceuticals, as building blocks for designer materials or as synthetic intermediates. This necessitated the development of new synthetic methods for the preparation of these strained ring systems focusing on effectiveness and scalability. The high ring strain of these entities as well as the use of high-energy reagents and intermediates has often challenged their synthesis. Continuous flow approaches have thus emerged as highly effective means to safely and reliably access these strained scaffolds. In this short review, key developments in this field are summarised showcasing the power of continuous flow approaches for accessing 3- and 4-membered ring systems via thermal, photo- and electrochemical processes.
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Affiliation(s)
- Kian Donnelly
- School of Chemistry, University College Dublin, Science Centre South, Belfield, Dublin 4, Ireland
| | - Marcus Baumann
- School of Chemistry, University College Dublin, Science Centre South, Belfield, Dublin 4, Ireland
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Naveen J, Satyanarayana G. Palladium-Catalyzed [3 + 2] Annulation of ortho-Substituted Iodoarenes with Maleimides via a Consecutive Double Heck-type Strategy. J Org Chem 2023; 88:16229-16247. [PMID: 37965816 DOI: 10.1021/acs.joc.3c01703] [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
Herein, we report an efficient [3 + 2] annulation of ortho-substituted iodoarenes with maleimides via a palladium-catalyzed consecutive double Heck-type strategy, leading to fused tricyclic frameworks of pharmaceutical relevance. The protocol ensued through consecutive inter- and intramolecular Heck couplings effectively. This approach was compatible with a large variety of substrates and functional groups, and it was remarkably tolerated with unprotected maleimide.
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Affiliation(s)
- Jakkula Naveen
- Department of Chemistry, Indian Institute of Technology (IIT) Hyderabad ,Kandi,Sangareddy ,Telangana 502 284, India
| | - Gedu Satyanarayana
- Department of Chemistry, Indian Institute of Technology (IIT) Hyderabad ,Kandi,Sangareddy ,Telangana 502 284, India
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Di Filippo M, Baumann M. Carbene-controlled regioselectivity in photochemical cascades. Org Biomol Chem 2023; 21:2930-2934. [PMID: 36745509 DOI: 10.1039/d3ob00122a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
A highly regioselective route to complex carbocyclic scaffolds through a continuous photochemical process is reported. Crucially, we uncovered that ortho substitutents on the right-hand aryl ring are placed away from a transient carbene species which induces the exclusive regioselectivity observed. By varying the non-symmetrically substituted aryl moiety, we demonstrate how the product outcome favors cyclobutenes for electron-poor and neutral substituents and cycloheptatrienes for more electron-rich systems. Additionally, a photochemically induced rearrangement was uncovered for highly electron-rich substrates that ultimately generates complex hydroperoxides. Overall, this facile one-step process is fast and high yielding and demonstrates the power of photochemistry towards the exploration of new chemical space.
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Affiliation(s)
- Mara Di Filippo
- University College Dublin, School of Chemistry, Science Centre South, Belfield, Dublin 4, Ireland.
| | - Marcus Baumann
- University College Dublin, School of Chemistry, Science Centre South, Belfield, Dublin 4, Ireland.
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Wang H, Tian YM, König B. Energy- and atom-efficient chemical synthesis with endergonic photocatalysis. Nat Rev Chem 2022; 6:745-755. [PMID: 37117495 DOI: 10.1038/s41570-022-00421-6] [Citation(s) in RCA: 16] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/10/2022] [Indexed: 11/09/2022]
Abstract
Endergonic photocatalysis is the use of light to perform catalytic reactions that are thermodynamically unfavourable. While photocatalysis has become a powerful tool in facilitating chemical transformations, the light-energy efficiency of these processes has not gathered much attention. Exergonic photocatalysis does not take full advantage of the light energy input, producing low-energy products and heat, whereas endergonic photocatalysis incorporates a portion of the photon energy into the reaction, yielding products that are higher in free energy than the reactants. Such processes can enable catalytic, atom-economic syntheses of reactive compounds from bench-stable materials. With respect to environmental friendliness and carbon neutrality, endergonic photocatalysis is also of interest to large-scale industrial manufacturing, where better energy efficiency, less waste and value addition are highly sought. We therefore assess here the thermochemistry of several classes of reported photocatalytic transformations to showcase current advances in endergonic photocatalysis and point to their industrial potential.
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Khalifa A, Redmond R, Sánchez-Sanz G, Evans P. Reduction of Substituted Benzo-Fused Cyclic Sulfonamides with Mg-MeOH: An Experimental and Computational Study. J Org Chem 2022; 87:12087-12095. [PMID: 36049485 PMCID: PMC9486945 DOI: 10.1021/acs.joc.2c01169] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/04/2022]
Abstract
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A study involving the use of Mg-MeOH for the double reductive
cleavage
of both N–S and C–S bonds in a series of 11 benzo-fused
cyclic sulfonamides is reported. Examples where the sulfonamide nitrogen
atom is part of a pyrrolidine ring effectively undergo reduction,
as long as a methoxy substituent is not para-positioned
in the aromatic ring, relative to the sulfonyl group. In contrast,
if the nitrogen atom is contained within an aromatic ring (pyrrole
or indole), the presence of a para-methoxy substituent
does not prohibit reduction. If deuterated methanol is used, aromatic ortho-deuterium incorporation was observed. To better understand
how structure affects reactivity, density functional theory calculations
were performed using three functionals. Results using CAM-B3LYP were
found to best correlate with experimental observations, and these
demonstrate the impact that the different aromatic substitution patterns
and types of N-atom have on the lowest unoccupied molecular orbital
(LUMO) energies and adiabatic electron affinities.
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Affiliation(s)
- Aisha Khalifa
- Centre for Synthesis and Chemical Biology, School of Chemistry, University College Dublin, Dublin D04 N2E5, Ireland
| | - Robert Redmond
- Centre for Synthesis and Chemical Biology, School of Chemistry, University College Dublin, Dublin D04 N2E5, Ireland
| | - Goar Sánchez-Sanz
- Centre for Synthesis and Chemical Biology, School of Chemistry, University College Dublin, Dublin D04 N2E5, Ireland
| | - Paul Evans
- Centre for Synthesis and Chemical Biology, School of Chemistry, University College Dublin, Dublin D04 N2E5, Ireland
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Donnelly K, Baumann M. Continuous Flow Technology as an Enabler for Innovative Transformations Exploiting Carbenes, Nitrenes, and Benzynes. J Org Chem 2022; 87:8279-8288. [PMID: 35700424 PMCID: PMC9251729 DOI: 10.1021/acs.joc.2c00963] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
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Miniaturization offered
by microreactors provides for superb reaction
control as well as excellent heat and mass transfer. By performing
chemical reactions in microreactors or tubular systems under continuous
flow conditions, increased safety can be harnessed which allows exploitation
of these technologies for the generation and immediate consumption
of high-energy intermediates. This Synopsis demonstrates the use of
flow technology to effectively exploit benzynes, carbenes, and nitrenes
in synthetic chemistry programs.
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Affiliation(s)
- Kian Donnelly
- School of Chemistry, Science Centre South, University College Dublin, D04 N2E2 Dublin, Ireland
| | - Marcus Baumann
- School of Chemistry, Science Centre South, University College Dublin, D04 N2E2 Dublin, Ireland
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Konan KE, Abollé A, Barré E, Aka EC, Coeffard V, Felpin FX. Developing flow photo-thiol–ene functionalizations of cinchona alkaloids with an autonomous self-optimizing flow reactor. REACT CHEM ENG 2022. [DOI: 10.1039/d1re00509j] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
Continuous flow photo-thiol–ene reactions on cinchona alkaloids with a variety of organic thiols have been developed using enabling technologies such as a self-optimizing flow photochemical reactor.
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Affiliation(s)
- Kouakou Eric Konan
- CNRS, Université de Nantes, CEISAM UMR 6230, 2 rue de la Houssinière, 44322 Nantes, France
- Laboratoire de Thermodynamique et de Physico-Chimie du Milieu, Université Nangui Abrogoua, 02 BP 801 Abidjan 02, Côte d'Ivoire
| | - Abollé Abollé
- Laboratoire de Thermodynamique et de Physico-Chimie du Milieu, Université Nangui Abrogoua, 02 BP 801 Abidjan 02, Côte d'Ivoire
| | - Elvina Barré
- CNRS, Université de Nantes, CEISAM UMR 6230, 2 rue de la Houssinière, 44322 Nantes, France
| | - Ehu Camille Aka
- CNRS, Université de Nantes, CEISAM UMR 6230, 2 rue de la Houssinière, 44322 Nantes, France
- Laboratoire de Thermodynamique et de Physico-Chimie du Milieu, Université Nangui Abrogoua, 02 BP 801 Abidjan 02, Côte d'Ivoire
| | - Vincent Coeffard
- CNRS, Université de Nantes, CEISAM UMR 6230, 2 rue de la Houssinière, 44322 Nantes, France
| | - François-Xavier Felpin
- CNRS, Université de Nantes, CEISAM UMR 6230, 2 rue de la Houssinière, 44322 Nantes, France
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Duffy M, Di Filippo M, Baumann M. Synthesis of 2H-indazoles via the Cadogan reaction in batch and flow mode. Tetrahedron Lett 2021. [DOI: 10.1016/j.tetlet.2021.153522] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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