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Elavarasan S, Preety J, Kesavan M, Patel RB, Baskar B. Activation of enamine by photoexcited organocatalyst assisted singlet oxygen: synthesis of oxazoles and quinoxalines. Org Biomol Chem 2024; 22:4912-4921. [PMID: 38808593 DOI: 10.1039/d4ob00609g] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/30/2024]
Abstract
Herein, a novel transition-metal-free thiol-based donor-acceptor organophotocatalyst-assisted, singlet-oxygen-mediated tandem oxidative cyclization for the synthesis of substituted oxazoles in moderate-to-good yields is described. The developed method demonstrates applicability for the synthesis of various substituted quinoxalines in good-to-excellent yields. The metal-free methodology shows a practical route for the synthesis of oxazole and quinoxaline derivatives, which are privileged moieties prevalent in various biologically active compounds and natural products. To the best of our knowledge, both the thiol photocatalyst and synthesis of oxazoles by visible-light irradiation are reported for the first time.
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Affiliation(s)
- Selvaraj Elavarasan
- Laboratory of Sustainable Synthesis, Department of Chemistry, SRM Institute of Science and Technology, Kattankulatur, 603 203, Chengalpet (Dt), Tamilnadu, India.
| | - Jeyaraj Preety
- Laboratory of Sustainable Synthesis, Department of Chemistry, SRM Institute of Science and Technology, Kattankulatur, 603 203, Chengalpet (Dt), Tamilnadu, India.
| | - M Kesavan
- Interdisciplinary Institute of Indian System of Medicine (IIISM), SRM Institute of Science and Technology, Kattankulatur, 603 203, Chengalpet (Dt), Tamilnadu, India
| | - Ravi B Patel
- Graduate School of Pharmacy, Gujarat Technological University, Ghandhinagar Campus, Ghandhinagar - 382028, Gujarat, India
| | - Baburaj Baskar
- Laboratory of Sustainable Synthesis, Department of Chemistry, SRM Institute of Science and Technology, Kattankulatur, 603 203, Chengalpet (Dt), Tamilnadu, India.
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Liu SH, Dong ZC, Zang ZL, Zhou CH, Cai GX. Selective α-oxidation of amides via visible-light-driven iron catalysis. Org Biomol Chem 2024; 22:1205-1212. [PMID: 38224270 DOI: 10.1039/d3ob01984e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2024]
Abstract
Hydroxyl radicals (˙OH) as one of the highly reactive species can react unselectively with a wide range of chemicals. The ˙OH radicals are typically generated under harsh conditions. Herein, we report hydroxyl radical-induced selective N-α C(sp3)-H bond oxidation of amides under greener and mild conditions via an Fe(NO3)3·9H2O catalyst inner sphere pathway upon irradiation with a 30 W blue LED light strip (λ = 455 nm) using NaBrO3 as the oxidant. This protocol exhibited high chemoselectivity and excellent functional group tolerance. A preliminary mechanism investigation demonstrated that the iron catalyst afforded hydroxyl radicals via the visible-light-induced homolysis (VLIH) of iron complexes followed by a hydrogen atom transfer (HAT) process to realize this transformation.
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Affiliation(s)
- Shu-Hong Liu
- Institute of Bioorganic & Medicinal Chemistry, School of Chemistry and Chemical Engineering, Southwest University, Chongqing 400715, P. R. China.
| | - Zhi-Chao Dong
- Institute of Bioorganic & Medicinal Chemistry, School of Chemistry and Chemical Engineering, Southwest University, Chongqing 400715, P. R. China.
| | - Zhong-Lin Zang
- Institute of Bioorganic & Medicinal Chemistry, School of Chemistry and Chemical Engineering, Southwest University, Chongqing 400715, P. R. China.
| | - Cheng-He Zhou
- Institute of Bioorganic & Medicinal Chemistry, School of Chemistry and Chemical Engineering, Southwest University, Chongqing 400715, P. R. China.
| | - Gui-Xin Cai
- Institute of Bioorganic & Medicinal Chemistry, School of Chemistry and Chemical Engineering, Southwest University, Chongqing 400715, P. R. China.
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Bjerg EE, Marchán-García J, Buxaderas E, Moglie Y, Radivoy G. Oxidative α-Functionalization of 1,2,3,4-Tetrahydroisoquinolines Catalyzed by a Magnetically Recoverable Copper Nanocatalyst. Application in the Aza-Henry Reaction and the Synthesis of 3,4-Dihydroisoquinolones. J Org Chem 2022; 87:13480-13493. [PMID: 36154121 DOI: 10.1021/acs.joc.2c01782] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The oxidative α-functionalization of 2-aryl-1,2,3,4-tetrahydroisoquinolines (THIQs) promoted by a versatile heterogeneous nanocatalyst consisting of copper nanoparticles immobilized on silica-coated maghemite (CuNPs/MagSilica) has been accomplished. The methodology was successfully applied in the cross-dehydrogenative coupling (CDC) reaction of N-aryl THIQs and other tertiary amines with nitromethane as a pro-nucleophile (aza-Henry reaction) and the α-oxidation of THIQs with O2 as a green oxidant. Phosphite, alkyne, or indole derivatives were also shown to be suitable candidates for their use as pro-nucleophiles in the CDC reaction with THIQs. The catalyst, with very low copper loading (0.4-1.0 mol % Cu), could be easily recovered by means of an external magnet and reused in four cycles without significant loss of activity.
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Affiliation(s)
- Esteban E Bjerg
- Instituto de Química del Sur, INQUISUR (CONICET-UNS), Departamento de Química, Universidad Nacional del Sur, Avenida Alem 1253, 8000 Bahía Blanca, Argentina
| | - Joaquín Marchán-García
- Instituto de Química del Sur, INQUISUR (CONICET-UNS), Departamento de Química, Universidad Nacional del Sur, Avenida Alem 1253, 8000 Bahía Blanca, Argentina
| | - Eduardo Buxaderas
- Instituto de Química del Sur, INQUISUR (CONICET-UNS), Departamento de Química, Universidad Nacional del Sur, Avenida Alem 1253, 8000 Bahía Blanca, Argentina
| | - Yanina Moglie
- Instituto de Química del Sur, INQUISUR (CONICET-UNS), Departamento de Química, Universidad Nacional del Sur, Avenida Alem 1253, 8000 Bahía Blanca, Argentina
| | - Gabriel Radivoy
- Instituto de Química del Sur, INQUISUR (CONICET-UNS), Departamento de Química, Universidad Nacional del Sur, Avenida Alem 1253, 8000 Bahía Blanca, Argentina
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Elavarasan S, Preety J, Abinaya R, Saravanan T, Balasunramaniam KK, Venkatramaiah N, Baskar B. Visible Light Driven Metal-Free Photoredox Catalyzed α-benzylation and α-oxygenation of N-substituted tetrahydroisoquinolines: Applications to Synthesis of Natural Products. Chem Asian J 2022; 17:e202200878. [PMID: 36073541 DOI: 10.1002/asia.202200878] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2022] [Revised: 09/06/2022] [Indexed: 11/07/2022]
Abstract
Herein, visible light mediated organophoto redox catalysed simple and convenient method for the a-benzylation and a-oxygenation of tertiary amines is demonstrated. Synthesis of novel thiophenol based donor acceptor organophotoredox catalysts 4a - 4d were investigated along with commercial catalyst 4-CzIPN ( 4e ). A diverse biologically active a-benzylated tetrahydroisoquinolines and natural products such as (±)-Norlaudanosine, (±)-laudanosine and (±)-xylopinine have been synthesized under the optimized conditions in yields ranging from from 62-91%. Exploitation of synthesized a-benzylated compound using present phtoredox catalyzed conditions gave rise to dehydyrogenative benzylic oxidation product under oxygen atmosphere which is known to display biologically and structurally important properties. Also, various N-protected tertiary amines were found to be suitable for the a-oxygenation reactions using catalyst 4e and resulted in good yields (61-85%).
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Affiliation(s)
- S Elavarasan
- SRM Institute of Science and Technology, Chemistry, INDIA
| | - J Preety
- SRM Institute of Science and Technology, Chemistry, INDIA
| | - R Abinaya
- SRM Institute of Science and Technology, Chemistry, INDIA
| | - T Saravanan
- University of Hyderabad, School of Chemistry, INDIA
| | | | | | - Baburaj Baskar
- SRM University, Chemistry, Kattankulathur, 603203, India, 603203, Chennai, INDIA
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