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12 pages, 1113 KB

Open AccessArticle

[2+2]-Photocycloadditions of 2-Acetoxy-1,4-naphthoquinone and Structure Determination of the Main Photoadducts

by Madyan A. Yaseen, Zhifang Guo, Peter C. Junk and Michael Oelgemöller

Photochem 2025, 5(4), 31; https://doi.org/10.3390/photochem5040031 - 10 Oct 2025

Viewed by 331

The [2+2]-photocycloaddition of 2-acetoxy-1,4-naphthoquinone with 1,1-diphenylethylene, styrene and cyclopentene was conducted in a conventional batch reactor. Prolonged irradiation selectively produced the corresponding anti and head-to-head cyclobutanes in acceptable to good yields. The batch process was subsequently transferred to continuous-flow operation in a simple [...] Read more.

The [2+2]-photocycloaddition of 2-acetoxy-1,4-naphthoquinone with 1,1-diphenylethylene, styrene and cyclopentene was conducted in a conventional batch reactor. Prolonged irradiation selectively produced the corresponding anti and head-to-head cyclobutanes in acceptable to good yields. The batch process was subsequently transferred to continuous-flow operation in a simple capillary device. Likewise, the photocycloaddition with diphenylacetylene gave the corresponding cyclobutene and a benzoanthracenone derivative in acceptable yields. The crystal structures of all main photoproducts were successfully determined. Full article

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12 pages, 2556 KB

Open AccessArticle

[2+2]-Photocycloadditions of 1,4-Naphthoquinone Under Batch and Continuous-Flow Conditions

by Madyan A. Yaseen, Zhifang Guo, Peter C. Junk and Michael Oelgemöller

Molecules 2024, 29(24), 5920; https://doi.org/10.3390/molecules29245920 - 15 Dec 2024

Cited by 2 | Viewed by 1505

Abstract

A series of [2+2]-photocycloadditions of 1,4-naphthoquinone with various alkenes and diphenylacetylene were investigated under batch and continuous-flow conditions. Acetone-sensitization furnished the corresponding photoadducts in good to excellent yields and purities. Compared to batch operations that demanded exhaustive irradiation times of 10–13 h, the [...] Read more.

A series of [2+2]-photocycloadditions of 1,4-naphthoquinone with various alkenes and diphenylacetylene were investigated under batch and continuous-flow conditions. Acetone-sensitization furnished the corresponding photoadducts in good to excellent yields and purities. Compared to batch operations that demanded exhaustive irradiation times of 10–13 h, the flow process generally gave superior conversions and subsequently yields with a residence time of just 60 min. The structures of several photoaddition products were further determined by crystal structure analysis. Full article

(This article belongs to the Section Photochemistry)

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21 pages, 8936 KB

Open AccessReview

Continuous Flow Chemistry: A Novel Technology for the Synthesis of Marine Drugs

by Laura F. Peña, Paula González-Andrés, Lucía G. Parte, Raúl Escribano, Javier Guerra, Asunción Barbero and Enol López

Mar. Drugs 2023, 21(7), 402; https://doi.org/10.3390/md21070402 - 13 Jul 2023

Cited by 8 | Viewed by 8572

Abstract

In this perspective, we showcase the benefits of continuous flow chemistry and photochemistry and how these valuable tools have contributed to the synthesis of organic scaffolds from the marine environment. These technologies have not only facilitated previously described synthetic pathways, but also opened [...] Read more.

In this perspective, we showcase the benefits of continuous flow chemistry and photochemistry and how these valuable tools have contributed to the synthesis of organic scaffolds from the marine environment. These technologies have not only facilitated previously described synthetic pathways, but also opened new opportunities in the preparation of novel organic molecules with remarkable pharmacological properties which can be used in drug discovery programs. Full article

(This article belongs to the Special Issue Synthetic Chemistry in Marine Drug Discovery: Challenges and Opportunities)

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13 pages, 3407 KB

Open AccessFeature PaperEditor’s ChoiceArticle

Continuous Flow Photochemical Synthesis of 3-Methyl-4-arylmethylene Isoxazole-5(4H)-ones through Organic Photoredox Catalysis and Investigation of Their Larvicidal Activity

by Ana Beatriz S. Sampaio, Mônica Shigemi S. Mori, Lorena C. Albernaz, Laila S. Espindola, Carlos Eduardo M. Salvador and Carlos Kleber Z. Andrade

Catalysts 2023, 13(3), 518; https://doi.org/10.3390/catal13030518 - 3 Mar 2023

Cited by 6 | Viewed by 3253

Abstract

Isoxazole-5(4H)-ones are heteropentacycle compounds found in several bioactive molecules with pharmaceutical and agrochemical properties. A well-known multicomponent reaction between β-ketoester, hydroxylamine, and aromatic aldehydes leads to 3-methyl-4-arylmethylene isoxazole-5(4H)-ones, in mild conditions. The initial purpose of this work was to investigate whether the reaction [...] Read more.

Isoxazole-5(4H)-ones are heteropentacycle compounds found in several bioactive molecules with pharmaceutical and agrochemical properties. A well-known multicomponent reaction between β-ketoester, hydroxylamine, and aromatic aldehydes leads to 3-methyl-4-arylmethylene isoxazole-5(4H)-ones, in mild conditions. The initial purpose of this work was to investigate whether the reaction might be induced by light, as described in previous works. Remarkable results were obtained using a high-power lamp, reducing reaction times compared to methodologies that used heating or catalysis. Since there are many examples of successful continuous flow heterocycle synthesis, including photochemical reactions, the study evolved to run the reaction in flow conditions and scale up the synthesis of isoxazolones using a photochemical reactor set-up. Eight different compounds were obtained, and among them, three showed larvicidal activity on immature forms of Aedes aegypti in tests that investigated its growth inhibitory character. Mechanistic investigations indicate that the reactions occur through organic photoredox catalysis. Full article

(This article belongs to the Special Issue Multicomponent Catalytic Reactions under Green Conditions)

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29 pages, 10734 KB

Open AccessReview

Continuous-Flow Chemistry and Photochemistry for Manufacturing of Active Pharmaceutical Ingredients

by Pavlína Horáková and Kamila Kočí

Molecules 2022, 27(23), 8536; https://doi.org/10.3390/molecules27238536 - 4 Dec 2022

Cited by 9 | Viewed by 10679

Abstract

An active pharmaceutical ingredient (API) is any substance in a pharmaceutical product that is biologically active. That means the specific molecular entity is capable of achieving a defined biological effect on the target. These ingredients need to meet very strict limits; chemical and [...] Read more.

An active pharmaceutical ingredient (API) is any substance in a pharmaceutical product that is biologically active. That means the specific molecular entity is capable of achieving a defined biological effect on the target. These ingredients need to meet very strict limits; chemical and optical purity are considered to be the most important ones. A continuous-flow synthetic methodology which utilizes a continuously flowing stream of reactive fluids can be easily combined with photochemistry, which works with the chemical effects of light. These methods can be useful tools to meet these strict limits. Both of these methods are unique and powerful tools for the preparation of natural products or active pharmaceutical ingredients and their precursors with high structural complexity under mild conditions. This review shows some main directions in the field of active pharmaceutical ingredients’ preparation using continuous-flow chemistry and photochemistry with numerous examples of industry and laboratory-scale applications. Full article

(This article belongs to the Special Issue Synthesis of Bioactive Compounds)

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10 pages, 1536 KB

Open AccessArticle

Supported Eosin Y as a Photocatalyst for C-H Arylation of Furan in Batch and Flow

by Sergio Rossi, Fabian Herbrik, Simonetta Resta and Alessandra Puglisi

Molecules 2022, 27(16), 5096; https://doi.org/10.3390/molecules27165096 - 10 Aug 2022

Cited by 21 | Viewed by 3176

Abstract

Eosin Y is one of the most popular organic dyes used as a photoredox catalyst and is largely employed in photochemical reactions both as a homogeneous and heterogeneous photocatalyst after immobilization. Immobilization of Eosin Y onto a solid support has many advantages, such [...] Read more.

Eosin Y is one of the most popular organic dyes used as a photoredox catalyst and is largely employed in photochemical reactions both as a homogeneous and heterogeneous photocatalyst after immobilization. Immobilization of Eosin Y onto a solid support has many advantages, such as the possibility of recovery and reuse of the photocatalyst and the possibility of its use under flow conditions. In this paper, we report our findings on the immobilization of Eosin Y onto Merrifield resin and its application in the direct photochemical arylation of furan with aryldiazonium salts. The synthesized supported photocatalyst was used in batch reactions under heterogeneous conditions with different aryl diazonium salts, and its recovery and recycle were demonstrated for up to three times. The immobilized photocatalyst was then loaded in a packed-bed reactor and used under continuous flow conditions. The flow reaction allowed the arylated products to be obtained with higher productivity and space-time-yield than the batch in a very short reaction time. Full article

(This article belongs to the Special Issue The Latest Trends in Catalyst Immobilization)

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13 pages, 2624 KB

Open AccessReview

Continuous Flow Photochemistry for the Preparation of Bioactive Molecules

by Mara Di Filippo, Cormac Bracken and Marcus Baumann

Molecules 2020, 25(2), 356; https://doi.org/10.3390/molecules25020356 - 15 Jan 2020

Cited by 92 | Viewed by 9619

Abstract

The last decade has witnessed a remarkable development towards improved and new photochemical transformations in response to greener and more sustainable chemical synthesis needs. Additionally, the availability of modern continuous flow reactors has enabled widespread applications in view of more streamlined and custom [...] Read more.

The last decade has witnessed a remarkable development towards improved and new photochemical transformations in response to greener and more sustainable chemical synthesis needs. Additionally, the availability of modern continuous flow reactors has enabled widespread applications in view of more streamlined and custom designed flow processes. In this focused review article, we wish to evaluate the standing of the field of continuous flow photochemistry with a specific emphasis on the generation of bioactive entities, including natural products, drugs and their precursors. To this end we highlight key developments in this field that have contributed to the progress achieved to date. Dedicated sections present the variety of suitable reactor designs and set-ups available; a short discussion on the relevance of greener and more sustainable approaches; and selected key applications in the area of bioactive structures. A final section outlines remaining challenges and areas that will benefit from further developments in this fast-moving area. It is hoped that this report provides a valuable update on this important field of synthetic chemistry which may fuel developments in the future. Full article

(This article belongs to the Special Issue Enabling Chemical Technologies in Medicinal Chemistry)

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10 pages, 1285 KB

Open AccessArticle

Continuous Flow Photochemical and Thermal Multi-Step Synthesis of Bioactive 3-Arylmethylene-2,3-Dihydro-1H-Isoindolin-1-Ones

by Saira Mumtaz, Mark J. Robertson and Michael Oelgemöller

Molecules 2019, 24(24), 4527; https://doi.org/10.3390/molecules24244527 - 11 Dec 2019

Cited by 12 | Viewed by 3534

Abstract

An effective multi-step continuous flow approach towards N-diaminoalkylated 3-arylmethylene-2,3-dihydro-1H-isoindolin-1-ones, including the local anesthetic compound AL-12, has been realized. Compared to the traditional decoupled batch processes, the combined photochemical–thermal–thermal flow setup rapidly provides the desired target compounds in superior yields and [...] Read more.

An effective multi-step continuous flow approach towards N-diaminoalkylated 3-arylmethylene-2,3-dihydro-1H-isoindolin-1-ones, including the local anesthetic compound AL-12, has been realized. Compared to the traditional decoupled batch processes, the combined photochemical–thermal–thermal flow setup rapidly provides the desired target compounds in superior yields and significantly shorter reaction times. Full article

(This article belongs to the Special Issue New Insights in Photoredox Catalysis)

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4 pages, 735 KB

Open AccessProceeding Paper

Transparent Glass/SU8-Based Microfluidic Device with on-Channel Electrical Sensors

by Mohammadmahdi Talebi, Keith Cobry, Ananya Sengupta and Peter Woias

Proceedings 2017, 1(4), 336; https://doi.org/10.3390/proceedings1040336 - 17 Aug 2017

Cited by 9 | Viewed by 3503

Abstract

This paper presents a transparent microfluidic chip designed for continuous-flow photochemistry applications with integrated electrical sensing. The transparent chip design allows for microscale photochemistry, and permits direct, real-time visual/electrical observation. The microchip uses optically transparent indium tin oxide (ITO) electrodes for reagent and [...] Read more.

This paper presents a transparent microfluidic chip designed for continuous-flow photochemistry applications with integrated electrical sensing. The transparent chip design allows for microscale photochemistry, and permits direct, real-time visual/electrical observation. The microchip uses optically transparent indium tin oxide (ITO) electrodes for reagent and phase tracking. High-speed videography was performed to validate the electrical measurement data. Full article

(This article belongs to the Proceedings of Proceedings of Eurosensors 2017, Paris, France, 3–6 September 2017)

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