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Open AccessArticle

Acid-Catalyzed, Metal- and Oxidant-Free C=C Bond Cleavage of Enaminones: One-Pot Synthesis of 3,4-Dihydroquinazolines

by Ting Chen, Ting Huang, Moudan Ye and Jinhai Shen

Molecules 2025, 30(2), 350; https://doi.org/10.3390/molecules30020350 - 16 Jan 2025

Cited by 2 | Viewed by 1475

In this study, we present the HOAc-catalyzed selective cleavage of the C=C double bond of enaminones, enabling the formation of a new C–N bond and a new C=N bond for the one-pot synthesis of 2-substituted 3,4-dihydroquinazolines directly from ynones and 2-(aminomethyl)anilines. This method [...] Read more.

In this study, we present the HOAc-catalyzed selective cleavage of the C=C double bond of enaminones, enabling the formation of a new C–N bond and a new C=N bond for the one-pot synthesis of 2-substituted 3,4-dihydroquinazolines directly from ynones and 2-(aminomethyl)anilines. This method operates in ethanol under transition-metal-free and oxidant-free conditions, offering a sustainable and efficient approach for the synthesis of 3,4-dihydroquinazolines with broad functional group tolerance. Full article

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8 pages, 1262 KB

Open AccessCommunication

From Dienophiles to Dienes: Catalysis by Polystyrene-Supported Triphenylphosphine with Pentane-2,4-dione as Co-Catalyst

by Ludvik O. Espeland and Leiv K. Sydnes

Molbank 2025, 2025(1), M1944; https://doi.org/10.3390/M1944 - 24 Dec 2024

Viewed by 1594

Abstract

Three 1,1-diethoxyalk-3-yn-2-ones underwent isomerization and gave only the corresponding (3E,5E)-alkadienones in 72–87% yield when subjected to polystyrene-supported triphenylphosphine at 60 °C using acetylacetone as a co-catalyst. As a first step to make the dienes electron richer, the diethoxyacetyl moiety [...] Read more.

Three 1,1-diethoxyalk-3-yn-2-ones underwent isomerization and gave only the corresponding (3E,5E)-alkadienones in 72–87% yield when subjected to polystyrene-supported triphenylphosphine at 60 °C using acetylacetone as a co-catalyst. As a first step to make the dienes electron richer, the diethoxyacetyl moiety was reduced with sodium borohydride under Luche conditions and afforded the corresponding alcohols, with a 92% yield in the best case. Full article

(This article belongs to the Section Organic Synthesis and Biosynthesis)

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5 pages, 805 KB

Open AccessShort Note

5-Diethoxymethyl-1,1-diethoxy-5-hydroxyundeca-3,6-diyn-2-one

by Ludvik O. Espeland and Leiv K. Sydnes

Molbank 2024, 2024(4), M1896; https://doi.org/10.3390/M1896 - 8 Oct 2024

Cited by 1 | Viewed by 1047

Abstract

As an extension of our study of the reactivity of derivatives of 3,3,4,4-tetraethoxybut-1-yne, attempts have been made to achieve acid-catalyzed deacetalization of the diethoxymethyl moieties in 5-diethoxymethyl-1,1,2,2-tetraethoxyundeca-3,6-diyn-5-ol. That was not achieved; instead, only deketalization occurred and afforded the title compound, indicating that the [...] Read more.

As an extension of our study of the reactivity of derivatives of 3,3,4,4-tetraethoxybut-1-yne, attempts have been made to achieve acid-catalyzed deacetalization of the diethoxymethyl moieties in 5-diethoxymethyl-1,1,2,2-tetraethoxyundeca-3,6-diyn-5-ol. That was not achieved; instead, only deketalization occurred and afforded the title compound, indicating that the triple bond activates the propargylic diethoxy moiety relative to the other acetal groups. Full article

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12 pages, 1403 KB

Open AccessArticle

Synthesis of Indenones via Persulfate Promoted Radical Alkylation/Cyclization of Biaryl Ynones with 1,4-Dihydropyridines

by Wanwan Wang and Lei Yu

Molecules 2024, 29(2), 458; https://doi.org/10.3390/molecules29020458 - 17 Jan 2024

Cited by 1 | Viewed by 1717

Abstract

The oxidative radical cascade cyclization of alkynes has emerged as a versatile strategy for the efficient construction of diverse structural units and complex molecules in organic chemistry. This work reports an alkyl radical initiated 5-exo-trig cyclization of biaryl ynones with 1,4-dihydropyridines [...] Read more.

The oxidative radical cascade cyclization of alkynes has emerged as a versatile strategy for the efficient construction of diverse structural units and complex molecules in organic chemistry. This work reports an alkyl radical initiated 5-exo-trig cyclization of biaryl ynones with 1,4-dihydropyridines to selectively synthesize indenones. Full article

(This article belongs to the Section Organic Chemistry)

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7 pages, 1082 KB

Open AccessProceeding Paper

Innovative Approaches in Acyl Sonogashira Coupling: Impact of Supported CuNPs and Cu-PdNPs Nanocatalysts

by Santiago Stabile and Gabriel Radivoy

Chem. Proc. 2023, 14(1), 76; https://doi.org/10.3390/ecsoc-27-16090 - 15 Nov 2023

Cited by 1 | Viewed by 1299

Abstract

In this work, we present our findings on the acyl Sonogashira coupling catalyzed by copper nanoparticles (CuNPs) or bimetallic copper–palladium (4:1 molar ratio) nanoparticles (Cu-PdNPs) immobilized in various inorganic materials. Both catalysts allowed the synthesis of ynones in good to excellent yields. Cu-PdNPs [...] Read more.

In this work, we present our findings on the acyl Sonogashira coupling catalyzed by copper nanoparticles (CuNPs) or bimetallic copper–palladium (4:1 molar ratio) nanoparticles (Cu-PdNPs) immobilized in various inorganic materials. Both catalysts allowed the synthesis of ynones in good to excellent yields. Cu-PdNPs supported on Celite exhibit high activity, allowing reactions to proceed at room temperature, whereas the monometallic CuNPs catalysts required reactions to be carried out at 80 °C. In addition, Cu-PdNPs/Celite can be also used in Sonogashira coupling reactions with iodoarenes. Both types of catalysts can be reused without any pre-treatment after separation from the reaction medium and subsequent washing. Full article

(This article belongs to the Proceedings of 27th International Electronic Conference on Synthetic Organic Chemistry)

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29 pages, 9236 KB

Open AccessArticle

Synthesis, Cytotoxic Activity and In Silico Study of Novel Dihydropyridine Carboxylic Acids Derivatives

by Ricardo Ballinas-Indilí, María Inés Nicolás-Vázquez, Joel Martínez, María Teresa Ramírez-Apan, Cecilio Álvarez-Toledano, Alfredo Toscano, Maricarmen Hernández-Rodríguez, Elvia Mera Jiménez and René Miranda Ruvalcaba

Int. J. Mol. Sci. 2023, 24(20), 15414; https://doi.org/10.3390/ijms242015414 - 21 Oct 2023

Cited by 5 | Viewed by 2748

Abstract

To aid the possible prevention of multidrug resistance in tumors and cause lower toxicity, a set of sixteen novel dihydropyridine carboxylic acids derivatives 3a–p were produced; thus, the activation of various ynones with triflic anhydride was performed, involving a nucleophilic addition of several [...] Read more.

To aid the possible prevention of multidrug resistance in tumors and cause lower toxicity, a set of sixteen novel dihydropyridine carboxylic acids derivatives 3a–p were produced; thus, the activation of various ynones with triflic anhydride was performed, involving a nucleophilic addition of several bis(trimethylsilyl) ketene acetals, achieving good yields requiring easy workup. The target molecules were unequivocally characterized by common spectroscopic methods. In addition, two of the tested compounds (3a, and 3b) were selected to perform in silico studies due to the highest cytotoxic activity towards the HCT-15 cell line (7.94 ± 1.6 μM and 9.24 ± 0.9 μM, respectively). Employing theoretical calculations with density functional theory (DFT) using the B3LYP/6-311++G(d,p) showed that the molecular parameters correlate adequately with the experimental results. In contrast, predictions employing Osiris Property Explorer showed that compounds 3a and 3b present physicochemical characteristics that would likely make it an orally active drug. Moreover, the performance of Docking studies with proteins related to the apoptosis pathway allowed a proposal of which compounds could interact with PARP-1 protein. Pondering the obtained results (synthesis, in silico, and cytotoxic activity) of the target compounds, they can be judged as suitable antineoplastic agent candidates. Full article

(This article belongs to the Section Physical Chemistry and Chemical Physics)

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15 pages, 3443 KB

Open AccessArticle

Synthesis of Pyridin-1(2H)-ylacrylates and the Effects of Different Functional Groups on Their Fluorescence

by Weiguang Yang, Danyang Luo, Guanrong Li, Qiaoli Luo, Martin G. Banwell and Lanmei Chen

Molecules 2023, 28(18), 6511; https://doi.org/10.3390/molecules28186511 - 8 Sep 2023

Cited by 1 | Viewed by 2211

Abstract

While fluorescent organic materials have many potential as well as proven applications and so have attracted significant attention, pyridine–olefin conjugates remain a less studied subset of such systems. Herein, therefore, we report on the development of the straightforward syntheses of pyridin-1(2H)-ylacrylates [...] Read more.

While fluorescent organic materials have many potential as well as proven applications and so have attracted significant attention, pyridine–olefin conjugates remain a less studied subset of such systems. Herein, therefore, we report on the development of the straightforward syntheses of pyridin-1(2H)-ylacrylates and the outcomes of a study of the effects of substituents on their fluorescent properties. Such compounds were prepared using a simple, metal-free and three-component coupling reaction involving 2-aminopyridines, sulfonyl azides and propiolates. The fluorescent properties of the ensuing products are significantly affected by the positions of substituents on the cyclic framework, with those located in central positions having the greatest impact. Electron-withdrawing groups tend to induce blue shifts while electron-donating ones cause red shifts. This work highlights the capacity that the micro-modification of fluorescent materials provides for fine-tuning their properties such that they may be usefully applied to, for example, the study of luminescent materials. Full article

(This article belongs to the Special Issue Novelties in N-Heterocycles Chemistry: From Synthesis to Application)

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18 pages, 2906 KB

Open AccessArticle

Acid-Switchable Synthesis of Trifluoromethylated Triazoles and Isoxazoles via Reaction of CF₃-Ynones with NaN₃: DFT Study of the Reaction Mechanism

by Vasiliy M. Muzalevskiy, Zoia A. Sizova, Mikhail S. Nechaev and Valentine G. Nenajdenko

Int. J. Mol. Sci. 2022, 23(23), 14522; https://doi.org/10.3390/ijms232314522 - 22 Nov 2022

Cited by 9 | Viewed by 2967

Abstract

A detailed study of the reaction of CF₃-ynones with NaN₃ was performed. It was found that the reaction permits the selective synthesis of either 4-trifluoroacetyltriazoles or 5-CF₃-isoxazoles. The chemoselectivity of the reaction was switchable via acid catalysis. The [...] Read more.

A detailed study of the reaction of CF₃-ynones with NaN₃ was performed. It was found that the reaction permits the selective synthesis of either 4-trifluoroacetyltriazoles or 5-CF₃-isoxazoles. The chemoselectivity of the reaction was switchable via acid catalysis. The reaction of CF₃-ynones with NaN₃ in EtOH produced high yields of 4-trifluoroacetyltriazoles. In contrast, the formation of 5-CF₃-isoxazoles was observed under catalysis by acids. This acid-switchable procedure can be performed at sub-gram scale. The possible reaction mechanism was supported by DFT calculations. The synthetic utility of the prepared 4-trifluoroacetyltriazoles was demonstrated. Full article

(This article belongs to the Special Issue Polynitrogen and Nitrogen-Oxygen Molecular Systems: Synthesis, Reactivity and Application)

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11 pages, 1941 KB

Open AccessArticle

Copper Catalyzed Inverse Electron Demand [4+2] Cycloaddition for the Synthesis of Oxazines

by Weiguang Yang, Zitong Zhou, Yu Zhao, Danyang Luo, Xiai Luo, Hui Luo, Liao Cui and Li Li

Catalysts 2022, 12(5), 526; https://doi.org/10.3390/catal12050526 - 7 May 2022

Cited by 3 | Viewed by 3105

Abstract

A copper catalyzed tandem CuAAC/ring cleavage/[4+2] annulation reaction of terminal ynones, sulfonyl azides, and imines has been developed to synthesize the functionalized oxazines under mild conditions. Particularly, the intermediate N-sulfonyl acylketenimines undergo cycloaddition of an inverse electron demand Diels–Alder reaction with imines [...] Read more.

A copper catalyzed tandem CuAAC/ring cleavage/[4+2] annulation reaction of terminal ynones, sulfonyl azides, and imines has been developed to synthesize the functionalized oxazines under mild conditions. Particularly, the intermediate N-sulfonyl acylketenimines undergo cycloaddition of an inverse electron demand Diels–Alder reaction with imines and a series of 1,3-oxazine derivatives were obtained successfully in good yields. Full article

(This article belongs to the Special Issue Catalysis in Green Chemistry and Organic Synthesis)

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14 pages, 3320 KB

Open AccessArticle

Ruthenafuran Complexes Supported by the Bipyridine-Bis(diphenylphosphino)methane Ligand Set: Synthesis and Cytotoxicity Studies

by Chi-Fung Yeung, Sik-Him Tang, Zhe Yang, Tsun-Yin Li, Ka-Kit Li, Yuen-Man Chan, Hau-Lam Shek, Kai-Wa Io, King-Ting Tam, Shek-Man Yiu, Man-Kit Tse and Chun-Yuen Wong

Molecules 2022, 27(5), 1709; https://doi.org/10.3390/molecules27051709 - 5 Mar 2022

Cited by 4 | Viewed by 3207

Abstract

Mononuclear and dinuclear Ru(II) complexes cis-[Ru(κ²-dppm)(bpy)Cl₂] (1), cis-[Ru(κ²-dppe)(bpy)Cl₂] (2) and [Ru₂(bpy)₂(μ-dpam)₂(μ-Cl)₂](Cl)₂ ([3](Cl)₂) were prepared from the [...] Read more.

Mononuclear and dinuclear Ru(II) complexes cis-[Ru(κ²-dppm)(bpy)Cl₂] (1), cis-[Ru(κ²-dppe)(bpy)Cl₂] (2) and [Ru₂(bpy)₂(μ-dpam)₂(μ-Cl)₂](Cl)₂ ([3](Cl)₂) were prepared from the reactions between cis(Cl), cis(S)-[Ru(bpy)(dmso-S)₂Cl₂] and diphosphine/diarsine ligands (bpy = 2,2′-bipyridine; dppm = 1,1-bis(diphenylphosphino)methane; dppe = 1,2-bis(diphenylphosphino)ethane; dpam = 1,1-bis(diphenylarsino)methane). While methoxy-substituted ruthenafuran [Ru(bpy)(κ²-dppe)(C^O)]⁺ ([7]⁺; C^O = anionic bidentate [C(OMe)CHC(Ph)O]⁻ chelate) was obtained as the only product in the reaction between 2 and phenyl ynone HC≡C(C=O)Ph in MeOH, replacing 2 with 1 led to the formation of both methoxy-substituted ruthenafuran [Ru(bpy)(κ²-dppm)(C^O)]⁺ ([4]⁺) and phosphonium-ring-fused bicyclic ruthenafuran [Ru(bpy)(P^C^O)Cl]⁺ ([5]⁺; P^C^O = neutral tridentate [(Ph)₂PCH₂P(Ph)₂CCHC(Ph)O] chelate). All of these aforementioned metallafuran complexes were derived from Ru(II)–vinylidene intermediates. The potential applications of these metallafuran complexes as anticancer agents were evaluated by in vitro cytotoxicity studies against cervical carcinoma (HeLa) cancer cell line. All the ruthenafuran complexes were found to be one order of magnitude more cytotoxic than cisplatin, which is one of the metal-based anticancer agents being widely used currently. Full article

(This article belongs to the Special Issue Organometallic Complexes: Fundamentals and Applications)

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29 pages, 21117 KB

Open AccessFeature PaperReview

Heterocycles by Consecutive Multicomponent Syntheses via Catalytically Generated Alkynoyl Intermediates

by Jonas Niedballa and Thomas J. J. Müller

Catalysts 2022, 12(1), 90; https://doi.org/10.3390/catal12010090 - 13 Jan 2022

Cited by 23 | Viewed by 4142

Abstract

Multicomponent processes are beneficial tools for the synthesis of heterocycles. As densely substituted bifunctional electrophiles, ynones are essential intermediates by applying cyclocondensations or cycloadditions in numerous heterocycle syntheses. The respective alkynoyl intermediates are generally accessible by palladium-, copper- and palladium/copper-catalyzed alkynylation. In turn, [...] Read more.

Multicomponent processes are beneficial tools for the synthesis of heterocycles. As densely substituted bifunctional electrophiles, ynones are essential intermediates by applying cyclocondensations or cycloadditions in numerous heterocycle syntheses. The respective alkynoyl intermediates are generally accessible by palladium-, copper- and palladium/copper-catalyzed alkynylation. In turn, the mild reaction conditions allow for a fast and versatile entry to functional heterocycles in the sense of consecutive multicomponent processes. This review collates and presents recent advances in accessing thirteen heterocycle classes and their applications by virtue of catalytic alkynoyl generation in diversity-oriented multicomponent syntheses in a one-pot fashion. Full article

(This article belongs to the Special Issue Metal-Catalyzed Processes in One-Pot Syntheses of Heterocycles)

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18 pages, 7699 KB

Open AccessFeature PaperArticle

Synthesis of 6,7-Dihydro-1H,5H-pyrazolo[1,2-a]pyrazoles by Azomethine Imine-Alkyne Cycloadditions Using Immobilized Cu(II)-Catalysts

by Urša Štanfel, Dejan Slapšak, Uroš Grošelj, Franc Požgan, Bogdan Štefane and Jurij Svete

Molecules 2021, 26(2), 400; https://doi.org/10.3390/molecules26020400 - 13 Jan 2021

Cited by 8 | Viewed by 4356

Abstract

A series of 12 silica gel-bound enaminones and their Cu(II) complexes were prepared and tested for their suitability as heterogeneous catalysts in azomethine imine-alkyne cycloadditions (CuAIAC). Immobilized Cu(II)–enaminone complexes showed promising catalytic activity in the CuAIAC reaction, but these new catalysts suffered from [...] Read more.

A series of 12 silica gel-bound enaminones and their Cu(II) complexes were prepared and tested for their suitability as heterogeneous catalysts in azomethine imine-alkyne cycloadditions (CuAIAC). Immobilized Cu(II)–enaminone complexes showed promising catalytic activity in the CuAIAC reaction, but these new catalysts suffered from poor reusability. This was not due to the decoordination of copper ions, as the use of enaminone ligands with additional complexation sites resulted in negligible improvement. On the other hand, reusability was improved by the use of 4-aminobenzoic acid linker, attached to 3-aminopropyl silica gel via an amide bond to the enaminone over the more hydrolytically stable N-arylenamine C-N bond. The study showed that silica gel-bound Cu(II)–enaminone complexes are readily available and suitable heterogeneous catalysts for the synthesis of 6,7-dihydro-1H,5H-pyrazolo[1,2-a]pyrazoles. Full article

(This article belongs to the Special Issue Recent Advances in the Synthesis, Functionalization and Applications of Pyrazole-Type Compounds I)

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10 pages, 1569 KB

Open AccessArticle

Eosin Y-Catalyzed Visible-Light-Mediated Aerobic Transformation of Pyrazolidine-3-One Derivatives

by Nejc Petek, Uroš Grošelj, Jurij Svete, Franc Požgan, Drago Kočar and Bogdan Štefane

Catalysts 2020, 10(9), 981; https://doi.org/10.3390/catal10090981 - 1 Sep 2020

Cited by 7 | Viewed by 5065

Abstract

By utilizing an underexplored reactivity of N1-substituted pyrazolidine-3-ones, we developed a visible-light-induced aerobic oxidation of N1-substituted pyrazolidine-3-one derivatives yielding the corresponding azomethine imines. The resulting azomethine imines can be further reacted with ynones in situ under copper catalyzed [3 + 2] cycloaddition reaction [...] Read more.

By utilizing an underexplored reactivity of N1-substituted pyrazolidine-3-ones, we developed a visible-light-induced aerobic oxidation of N1-substituted pyrazolidine-3-one derivatives yielding the corresponding azomethine imines. The resulting azomethine imines can be further reacted with ynones in situ under copper catalyzed [3 + 2] cycloaddition reaction conditions yielding the corresponding pyrazolo[1,2-a]pyrazoles in good yields. The methodology can be extended to other 1-aryl-substituted pyrazolidinones which undergo endocyclic oxidation deriving the corresponding pyrazolones as single products. Full article

(This article belongs to the Special Issue Transition-Metal Catalysts for C–H Bond Functionalization of Heteroarenes)

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11 pages, 2261 KB

Open AccessCommunication

Synthesis of Porous Organic Polymers with Tunable Amine Loadings for CO₂ Capture: Balanced Physisorption and Chemisorption

by Xueying Kong, Shangsiying Li, Maria Strømme and Chao Xu

Nanomaterials 2019, 9(7), 1020; https://doi.org/10.3390/nano9071020 - 17 Jul 2019

Cited by 47 | Viewed by 6761

Abstract

The cross-coupling reaction of 1,3,5-triethynylbenzene with terephthaloyl chloride gives a novel ynone-linked porous organic polymer. Tethering alkyl amine species on the polymer induces chemisorption of CO₂ as revealed by the studies of ex situ infrared spectroscopy. By tuning the amine loading content [...] Read more.

The cross-coupling reaction of 1,3,5-triethynylbenzene with terephthaloyl chloride gives a novel ynone-linked porous organic polymer. Tethering alkyl amine species on the polymer induces chemisorption of CO₂ as revealed by the studies of ex situ infrared spectroscopy. By tuning the amine loading content on the polymer, relatively high CO₂ adsorption capacities, high CO₂-over-N₂ selectivity, and moderate isosteric heat (Q_st) of adsorption of CO₂ can be achieved. Such amine-modified polymers with balanced physisorption and chemisorption of CO₂ are ideal sorbents for post-combustion capture of CO₂ offering both high separation and high energy efficiencies. Full article

(This article belongs to the Special Issue Functional Nanoporous Materials)

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11 pages, 302 KB

Open AccessArticle

Photochemical Synthesis and Properties of 1,6- and 1,8-Naphthalenophanes

by Pablo Wessig and Annika Matthes

Molecules 2013, 18(1), 1314-1324; https://doi.org/10.3390/molecules18011314 - 21 Jan 2013

Cited by 10 | Viewed by 5113

Abstract

Various 1,6- and 1,8-naphthalenophanes were synthesized by using the Photo-Dehydro-Diels-Alder (PDDA) reaction of bis-ynones. These compounds are easily accessible from w-(3-iodophenyl)carboxylic acids in three steps. The obtained naphthalenophanes are axially chiral and the activation barrier for the atropisomerization could be determined in some [...] Read more.

Various 1,6- and 1,8-naphthalenophanes were synthesized by using the Photo-Dehydro-Diels-Alder (PDDA) reaction of bis-ynones. These compounds are easily accessible from w-(3-iodophenyl)carboxylic acids in three steps. The obtained naphthalenophanes are axially chiral and the activation barrier for the atropisomerization could be determined in some cases by means of dynamic NMR (DNMR) and/or dynamic HPLC (DHPLC) experiments. Full article

(This article belongs to the Special Issue New Trends in Photochemistry)

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