Publication: Benzimidazole-triazole ligands with pendent triazole functionality: Unexpected formation and effects on copper-catalyzed aerobic alcohol oxidation
Issued Date
2016-01-01
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ISSN
14779234
14779226
14779226
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2-s2.0-84993940255
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Mahidol University
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SCOPUS
Bibliographic Citation
Dalton Transactions. Vol.45, No.42 (2016), 16810-16819
Suggested Citation
Manisa Kongkaew, Kannika Sitthisuwannakul, Vasut Nakarajouyphon, Soraya Pornsuwan, Palangpon Kongsaeree, Preeyanuch Sangtrirutnugul Benzimidazole-triazole ligands with pendent triazole functionality: Unexpected formation and effects on copper-catalyzed aerobic alcohol oxidation. Dalton Transactions. Vol.45, No.42 (2016), 16810-16819. doi:10.1039/c6dt02770a Retrieved from: https://repository.li.mahidol.ac.th/handle/20.500.14594/43334
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Title
Benzimidazole-triazole ligands with pendent triazole functionality: Unexpected formation and effects on copper-catalyzed aerobic alcohol oxidation
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Abstract
© 2016 The Royal Society of Chemistry. A series of benzimidazole-triazole ligands (NN′) having a pendent triazole arm with different triazole substituents including CH2Ph (3a), cyclo-C6H11(3b), and CH2SiMe3(3c) were obtained in moderate yields from Cu-catalyzed oxidative C-N cyclization of the respective amine-triazole compounds N,N′-bis((1-R-1,2,3-triazol-4-yl)methyl)benzene-1,2-diamine (2a-2c). Treatment of CuCl2with one equiv. of the benzimidazole-triazole ligands afforded the corresponding CuIIcomplexes with the empirical formula of Cu(NN′)Cl2(4a-4c). Crystal structures of 4b and 4c reveal mononuclear and dinuclear CuIIcomplexes, respectively. Despite the differences in triazole substituents and their solid state structures, ESR spectra indicate the same molecular structures in CH3CN solution whereas CV data suggest similar redox potentials for 4a-4c. Catalytic activities for aerobic oxidation of benzyl alcohol to benzaldehyde follow this trend: 4c > 4a > 4b. In addition, the catalytic system 4c/TEMPO/Cu0/NMI (TEMPO = 2,2,6,6-tetramethyl-1-piperidinyloxyl, NMI = N-methylimidazole) exhibited high activities for oxidation of activated alcohols (i.e., benzyl alcohol derivatives and allylic alcohol) in CH3CN at room temperature.