1
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Liao ZY, Gao F, Ye YH, Yu QH, Yang C, Luo QY, Du F, Pan B, Zhong WW, Liang W. Construction of cyclobutane-fused tetracyclic skeletons via substrate-dependent EnT-enabled dearomative [2+2] cycloaddition of benzofurans (benzothiophenes)/maleimides. Chem Commun (Camb) 2024; 60:4455-4458. [PMID: 38563643 DOI: 10.1039/d4cc00690a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/04/2024]
Abstract
Herein, a novel and facile organic photosensitizer (thioxanthone)-mediated energy-transfer-enabled (EnT-enabled) dearomative [2+2] cycloaddition of aromatic heterocycles/maleimides for green synthesis of cyclobutane-fused polycyclic skeletons is reported. Mechanistic investigations revealed that different EnT pathways by triplet thioxanthone were initiated when different aromatic heterocycles participated in the reaction, giving the corresponding excited intermediates, which underwent the subsequent intermolecular [2+2] cycloaddition to access the desired highly functionalized cyclobutane-fused polycyclic skeletons.
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Affiliation(s)
- Zhi-Yu Liao
- College of Pharmacy, Chongqing Medical University, Chongqing, 400016, China.
| | - Fan Gao
- College of Pharmacy, Chongqing Medical University, Chongqing, 400016, China.
| | - Yu-Hang Ye
- College of Pharmacy, Chongqing Medical University, Chongqing, 400016, China.
| | - Qian-Hui Yu
- College of Pharmacy, Chongqing Medical University, Chongqing, 400016, China.
| | - Cui Yang
- College of Pharmacy, Chongqing Medical University, Chongqing, 400016, China.
| | - Qing-Yu Luo
- College of Pharmacy, Chongqing Medical University, Chongqing, 400016, China.
| | - Fei Du
- College of Pharmacy, Chongqing Medical University, Chongqing, 400016, China.
| | - Bin Pan
- College of Pharmacy, Third Military Medical University, Shapingba, Chongqing 400038, China
| | - Wen-Wu Zhong
- Department of Pharmacy, Chongqing Medical and Pharmaceutical College, Shapingba, Chongqing 401334, China.
| | - Wu Liang
- College of Pharmacy, Chongqing Medical University, Chongqing, 400016, China.
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2
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Ahuja S, Baburaj S, Valloli LK, Rakhimov SA, Manal K, Kushwaha A, Jockusch S, Forbes MDE, Sivaguru J. Photochemical [2+4]-Dimerization Reaction from the Excited State. Angew Chem Int Ed Engl 2024; 63:e202316662. [PMID: 38059768 DOI: 10.1002/anie.202316662] [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: 11/02/2023] [Revised: 11/27/2023] [Accepted: 11/29/2023] [Indexed: 12/08/2023]
Abstract
Aryl-maleimides undergo a novel [2+4]-photodimerization instead of the expected [2+2]-photodimerization under both direct irradiation with visible light and under sensitized energy transfer conditions. This new excited state reactivity in aryl-maleimides is deciphered through photochemical, photophysical, and spectroscopic studies. The stereochemistry of the photodimer depends on the type of non-bonding interactions prevalent during photodimerization which is in turn dictated by the substituents on the maleimide ring. More importantly, the stereochemistry of the photodimer formed is complementary to the product observed under thermal conditions.
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Affiliation(s)
- Sapna Ahuja
- Center for Photochemical Sciences and Department of Chemistry, Bowling Green State University, Bowling Green, OH 43403, USA
- Current address, Research way, Clayton, Manufacturing, CSIRO, 3168, VIC, Australia
| | - Sruthy Baburaj
- Center for Photochemical Sciences and Department of Chemistry, Bowling Green State University, Bowling Green, OH 43403, USA
| | - Lakshmy Kannadi Valloli
- Center for Photochemical Sciences and Department of Chemistry, Bowling Green State University, Bowling Green, OH 43403, USA
| | - Sarvar Aminovich Rakhimov
- Center for Photochemical Sciences and Department of Chemistry, Bowling Green State University, Bowling Green, OH 43403, USA
| | - Kavyasree Manal
- Center for Photochemical Sciences and Department of Chemistry, Bowling Green State University, Bowling Green, OH 43403, USA
| | - Aakrati Kushwaha
- Center for Photochemical Sciences and Department of Chemistry, Bowling Green State University, Bowling Green, OH 43403, USA
| | - Steffen Jockusch
- Center for Photochemical Sciences and Department of Chemistry, Bowling Green State University, Bowling Green, OH 43403, USA
| | - Malcolm D E Forbes
- Center for Photochemical Sciences and Department of Chemistry, Bowling Green State University, Bowling Green, OH 43403, USA
| | - Jayaraman Sivaguru
- Center for Photochemical Sciences and Department of Chemistry, Bowling Green State University, Bowling Green, OH 43403, USA
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3
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Zähringer TJB, Wienhold M, Gilmour R, Kerzig C. Direct Observation of Triplet States in the Isomerization of Alkenylboronates by Energy Transfer Catalysis. J Am Chem Soc 2023; 145:21576-21586. [PMID: 37729087 DOI: 10.1021/jacs.3c07678] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/22/2023]
Abstract
Alkenylboronates are versatile building blocks for stereocontrolled synthesis owing to the traceless nature of the boron group that can be leveraged to achieve highly selective geometric isomerization. Using thioxanthone as an inexpensive photocatalyst, the photoisomerization of these species continues to provide an expansive platform for stereodivergent synthesis, particularly in the construction of bioactive polyenes. Although mechanistic investigations are consistent with light-driven energy transfer, direct experimental evidence remains conspicuously absent. Herein, we report a rigorous mechanistic investigation using two widely used alkenylboronates alongside relevant reference compounds. Through the combination of irradiation experiments, transient absorption spectroscopic studies, kinetic modeling, and DFT calculations with all isomers of the model compounds, it has been possible to unequivocally detect and characterize the perpendicular triplet generated by energy transfer. Our results serve not only as a blueprint for mechanistic studies that are challenging with organic sensitizers, but these guidelines delineated have also enabled the development of more sustainable reaction conditions: for the first time, efficient organocatalytic isomerization under sunlight irradiation has become feasible.
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Affiliation(s)
- Till J B Zähringer
- Department of Chemistry, Johannes Gutenberg University Mainz, Duesbergweg 10-14, 55128 Mainz, Germany
| | - Max Wienhold
- Organisch-Chemisches Institut,Westfälische Wilhelms-Universität Münster, Correnstraβe 36, 48149 Münster, Germany
| | - Ryan Gilmour
- Organisch-Chemisches Institut,Westfälische Wilhelms-Universität Münster, Correnstraβe 36, 48149 Münster, Germany
- Cells in Motion (CiM) Interfaculty Center, Röntgenstraβe 16, 48149 Münster, Germany
| | - Christoph Kerzig
- Department of Chemistry, Johannes Gutenberg University Mainz, Duesbergweg 10-14, 55128 Mainz, Germany
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4
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Liashuk OS, Grygorenko OO, Volovenko YM, Waser J. Photochemical [2+2] Cycloaddition of Alkynyl Boronates. Chemistry 2023; 29:e202301650. [PMID: 37394686 DOI: 10.1002/chem.202301650] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2023] [Revised: 06/30/2023] [Accepted: 06/30/2023] [Indexed: 07/04/2023]
Abstract
A photochemical [2+2] cycloaddition of alkynyl boronates and maleimides is reported. The developed protocol provided 35-70 % yield of maleimide-derived cyclobutenyl boronates and demonstrated wide compatibility with various functional groups. The synthetic utility of the prepared building blocks was demonstrated for a range of transformations, including Suzuki cross-coupling, catalytic or metal-hydride reduction, oxidation, and cycloaddition reactions. With aryl-substituted alkynyl boronates, the products of double [2+2] cycloaddition were obtained predominantly. Using the developed protocol, a cyclobutene-derived analogue of Thalidomide was prepared in one step. Mechanistic studies supported the participation of the triplet-excited state maleimides and ground state alkynyl boronates in the key step of the process.
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Affiliation(s)
- Oleksandr S Liashuk
- Chemical Faculty, Taras Shevchenko National University of Kyїv, Kyiv, Volodymyrska Street 60, 01601, Kyїv, Ukraine
- Laboratory of Catalysis and Organic Synthesis, Institut des Sciences et Ingénierie Chimique, Ecole Polytechnique Fédérale de Lausanne, 1015, Lausanne, Switzerland
- Enamine Ltd., Kyiv, Winston Churchill Street 78, 02094, Kyїv, Ukraine
| | - Oleksandr O Grygorenko
- Chemical Faculty, Taras Shevchenko National University of Kyїv, Kyiv, Volodymyrska Street 60, 01601, Kyїv, Ukraine
- Enamine Ltd., Kyiv, Winston Churchill Street 78, 02094, Kyїv, Ukraine
| | - Yulian M Volovenko
- Chemical Faculty, Taras Shevchenko National University of Kyїv, Kyiv, Volodymyrska Street 60, 01601, Kyїv, Ukraine
| | - Jérôme Waser
- Laboratory of Catalysis and Organic Synthesis, Institut des Sciences et Ingénierie Chimique, Ecole Polytechnique Fédérale de Lausanne, 1015, Lausanne, Switzerland
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5
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Skolia E, Kokotos CG. Photochemical [2 + 2] Cycloaddition of Alkenes with Maleimides: Highlighting the Differences between N-Alkyl vs N-Aryl Maleimides. ACS ORGANIC & INORGANIC AU 2022; 3:96-103. [PMID: 37035280 PMCID: PMC10080724 DOI: 10.1021/acsorginorgau.2c00053] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/07/2022] [Revised: 11/23/2022] [Accepted: 11/28/2022] [Indexed: 12/13/2022]
Abstract
Throughout the last 15 years, there has been increased research interest in the use of light promoting organic transformations. [2 + 2] Cycloadditions are usually performed photochemically; however, literature precedent on the reaction between olefins and maleimides is limited to a handful of literature examples, focusing mainly on N-aliphatic maleimides or using metal catalysts for visible-light driven reactions of N-aromatic maleimides. Herein, we identify the differences in reactivity between N-alkyl and N-aryl maleimides. For our optimized protocols, in the case of N-alkyl maleimides, the reaction with alkenes proceeds under 370 nm irradiation in the absence of an external photocatalyst, leading to products in high yields. In the case of N-aryl maleimides, the reaction with olefins requires thioxanthone as the photosensitizer under 440 nm irradiation.
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Affiliation(s)
- Elpida Skolia
- Laboratory of Organic Chemistry, Department of Chemistry, National and Kapodistrian University of Athens, Panepistimiopolis 15771, Athens, Greece
| | - Christoforos G. Kokotos
- Laboratory of Organic Chemistry, Department of Chemistry, National and Kapodistrian University of Athens, Panepistimiopolis 15771, Athens, Greece
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6
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Takagi R, Tanimoto T. Enantioselective [2 + 2] photocycloaddition of quinolone using a C1-symmetric chiral phosphoric acid as a visible-light photocatalyst. Org Biomol Chem 2022; 20:3940-3947. [PMID: 35506886 DOI: 10.1039/d2ob00607c] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
The enantioselective intra- and intermolecular [2 + 2] photocycloaddition of quinolone using a C1-symmetric chiral phosphoric acid as a visible-light photocatalyst is developed. The thioxanthone chromophore on phosphoric acid plays an important role in both phototransformation and enantioselectivity.
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Affiliation(s)
- Ryukichi Takagi
- Department of Chemistry, Graduate School of Science, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima 739-8526, Japan.
| | - Takaaki Tanimoto
- Department of Chemistry, Graduate School of Science, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima 739-8526, Japan.
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7
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Kandappa SK, Ahuja S, Singathi R, Valloli LK, Baburaj S, Parthiban J, Sivaguru J. Using Restricted Bond Rotations to Enforce Excited State Behavior of Organic Molecules. Synlett 2022. [DOI: 10.1055/a-1785-6910] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
This account highlights the role of restricted bond rotations to influence excited state reactivity of organic molecules. It highlights photochemical reactivity of various organic molecules and the design strategies that could be exploited by chemists to utilize restricted bond rotations to uncover new excited state reactivity and achieve selectivity.
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Affiliation(s)
- Sunil Kumar Kandappa
- Chemistry and Center for Photochemical Sciences, Bowling Green State University, Bowling Green, United States
| | - Sapna Ahuja
- Chemistry and Center for Photochemical Sciences, Bowling Green State University, Bowling Green, United States
| | - Ravichandranath Singathi
- Chemistry and Center for Photochemical Sciences, Bowling Green State University, Bowling Green, United States
| | - Lakshmy Kannadi Valloli
- Chemistry and Center for Photochemical Sciences, Bowling Green State University, Bowling Green, United States
| | - Sruthy Baburaj
- Chemistry and Center for Photochemical Sciences, Bowling Green State University, Bowling Green, United States
| | - Jayachandran Parthiban
- Chemistry and Center for Photochemical Sciences, Bowling Green State University, Bowling Green, United States
| | - Jayaraman Sivaguru
- Chemistry and Center for Photochemical Sciences, Bowling Green State University, Bowling Green, United States
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8
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Triandafillidi I, Nikitas NF, Gkizis PL, Spiliopoulou N, Kokotos CG. Hexafluoroisopropanol-Promoted or Brønsted Acid-Mediated Photochemical [2+2] Cycloadditions of Alkynes with Maleimides. CHEMSUSCHEM 2022; 15:e202102441. [PMID: 34978379 DOI: 10.1002/cssc.202102441] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/16/2021] [Revised: 12/23/2021] [Indexed: 06/14/2023]
Abstract
Although the use of light stimulating organic transformations has been known for more than a century, there is an increasing research interest on expanding the established knowledge. While [2+2] cycloadditions are promoted photochemically, literature precedent on the reaction between alkynes and maleimides is limited and only a handful of examples exist, focusing mainly on N-aliphatic maleimides. Herein, the differences in reactivity between N-alkyl and N-aryl maleimides were identified, and the use of hexafluoroisopropanol (HFIP) or trifluoroacetic acid (TFA) as viable solutions was proposed in order to achieve high yields. In the case of N-alkyl maleimides, both HFIP-mediated or TFA-promoted reactions were established using LED 370 nm irradiation, without the use of an external photocatalyst. In the case of N-aryl maleimides, thioxanthone (THX) was employed as the energy transfer photocatalyst along with LED 427 nm irradiation and HFIP. Mechanistic studies were performed, supporting the pivotal role of HFIP or TFA, in acquiring good to high yields in both classes of maleimides.
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Affiliation(s)
- Ierasia Triandafillidi
- Laboratory of Organic Chemistry, Department of Chemistry, National and Kapodistrian University of Athens, Panepistimiopolis, 15771, Athens, Greece
| | - Nikolaos F Nikitas
- Laboratory of Organic Chemistry, Department of Chemistry, National and Kapodistrian University of Athens, Panepistimiopolis, 15771, Athens, Greece
| | - Petros L Gkizis
- Laboratory of Organic Chemistry, Department of Chemistry, National and Kapodistrian University of Athens, Panepistimiopolis, 15771, Athens, Greece
| | - Nikoleta Spiliopoulou
- Laboratory of Organic Chemistry, Department of Chemistry, National and Kapodistrian University of Athens, Panepistimiopolis, 15771, Athens, Greece
| | - Christoforos G Kokotos
- Laboratory of Organic Chemistry, Department of Chemistry, National and Kapodistrian University of Athens, Panepistimiopolis, 15771, Athens, Greece
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9
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Bargum MA, Krell-Jørgensen MP, Nielsen M, Qvortrup K, Laraia L. A photochemical microfluidic reactor for photosensitized [2+2] cycloadditions. Synlett 2022. [DOI: 10.1055/a-1771-4883] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Abstract
Here we report a microfluidic system for photochemical cycloadditions fabricated using silicon micro processing technologies. The system was optimized to yield residence times of just a few minutes for a range of photochemical [2+2]-cycloaddition reactions facilitated using high power UV-LEDs at 375 nm and triplet photosensitizers, which removed the need for the low wavelengths typically required for these types of transformations. Adducts using different excitable olefins with different linear-, carbocyclic- and heterocyclic coupling partners were explored to demonstrate the feasibility of performing photochemistry in microflow in an academic research environment. Finally, a reaction leading to a novel dihydrooxepin-2(3H)-one scaffold, and a mechanistic proposal for its formation are reported.
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Affiliation(s)
| | | | - Martin Nielsen
- Department of Chemistry, Technical University of Denmark, Kgs. Lyngby, Denmark
| | - Katrine Qvortrup
- Department of Chemistry, Technical University of Denmark, Kgs. Lyngby, Denmark
| | - Luca Laraia
- Department of Chemistry, Technical University of Denmark, Kgs. Lyngby, Denmark
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10
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Nikitas NF, Gkizis PL, Kokotos CG. Thioxanthone: a powerful photocatalyst for organic reactions. Org Biomol Chem 2021; 19:5237-5253. [PMID: 34047729 DOI: 10.1039/d1ob00221j] [Citation(s) in RCA: 55] [Impact Index Per Article: 18.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Photoorganocatalysis has been recognised by the organic chemistry community as an important part of photochemistry and catalysis. In general, aromatic ketones constitute key players in this type of catalysis as they are involved in a plethora of examples in the literature. Among the various aromatic ketones, thioxanthone (TX) seems to play a unique role in photochemistry. In comparison with other aromatic ketones, TX has a high triplet energy and a relatively long triplet lifetime, while it has the ability to participate successfully in merger reactions with metal complexes. In this review, we will discuss the photophysical properties of this small organic molecule, as well as the numerous examples of photochemical reactions, where it is employed as a mediator and more specifically in polymerisation reactions, and organic transformations.
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Affiliation(s)
- Nikolaos F Nikitas
- Laboratory of Organic Chemistry, Department of Chemistry, National and Kapodistrian University of Athens, Panepistimiopolis, Athens 15771, Greece.
| | - Petros L Gkizis
- Laboratory of Organic Chemistry, Department of Chemistry, National and Kapodistrian University of Athens, Panepistimiopolis, Athens 15771, Greece.
| | - Christoforos G Kokotos
- Laboratory of Organic Chemistry, Department of Chemistry, National and Kapodistrian University of Athens, Panepistimiopolis, Athens 15771, Greece.
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11
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He J, Bai ZQ, Yuan PF, Wu LZ, Liu Q. Highly Efficient Iridium-Based Photosensitizers for Thia-Paternò–Büchi Reaction and Aza-Photocyclization. ACS Catal 2020. [DOI: 10.1021/acscatal.0c05005] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Jian He
- State Key Laboratory of Applied Organic Chemistry, College of Chemistry and Chemical Engineering, Lanzhou University, Lanzhou 730000, P. R. China
| | - Zhi-Qin Bai
- State Key Laboratory of Applied Organic Chemistry, College of Chemistry and Chemical Engineering, Lanzhou University, Lanzhou 730000, P. R. China
| | - Pan-Feng Yuan
- State Key Laboratory of Applied Organic Chemistry, College of Chemistry and Chemical Engineering, Lanzhou University, Lanzhou 730000, P. R. China
| | - Li-Zhu Wu
- State Key Laboratory of Applied Organic Chemistry, College of Chemistry and Chemical Engineering, Lanzhou University, Lanzhou 730000, P. R. China
- Key Laboratory of Photochemical Conversion and Optoelectronic Materials, Technical Institute of Physics and Chemistry, the Chinese Academy of Sciences, Beijing 100190, P. R. China
| | - Qiang Liu
- State Key Laboratory of Applied Organic Chemistry, College of Chemistry and Chemical Engineering, Lanzhou University, Lanzhou 730000, P. R. China
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12
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Aljuaid M, Liarou E, Town J, Baker JR, Haddleton DM, Wilson P. Synthesis and [2+2]-photodimerisation of monothiomaleimide functionalised linear and brush-like polymers. Chem Commun (Camb) 2020; 56:9545-9548. [PMID: 32691028 DOI: 10.1039/d0cc04067c] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
[2+2]-Photodimerisation of monothiomaleimides has been demonstrated on functionalised linear and brush-like polymers. In water/acetonitrile (95 : 5) mixtures the rate of reaction is accelerated significantly by irradiation of the thiomaleimide end group (λmax = 350 nm) with UV light, reaching full conversion within 10 minutes.
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Affiliation(s)
- Mohammed Aljuaid
- University of Warwick, Department of Chemistry, Library Road, Coventry, UK. and Taif University, Department of Chemistry, Faculty of Applied Medical Sciences, Turabah, Saudi Arabia
| | - Evelina Liarou
- University of Warwick, Department of Chemistry, Library Road, Coventry, UK.
| | - James Town
- University of Warwick, Department of Chemistry, Library Road, Coventry, UK.
| | - James R Baker
- University College London, Department of Chemistry, 20 Gordon St, London, UK
| | - David M Haddleton
- University of Warwick, Department of Chemistry, Library Road, Coventry, UK.
| | - Paul Wilson
- University of Warwick, Department of Chemistry, Library Road, Coventry, UK.
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