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Article: Graphite-supported gold nanoparticles as efficient catalyst for aerobic oxidation of benzylic amines to imines and N-substituted 1,2,3,4- tetrahydroisoquinolines to amides: Synthetic applications and mechanistic study

TitleGraphite-supported gold nanoparticles as efficient catalyst for aerobic oxidation of benzylic amines to imines and N-substituted 1,2,3,4- tetrahydroisoquinolines to amides: Synthetic applications and mechanistic study
Authors
KeywordsAmines
Gold
Heterogeneous catalysis
Nanoparticles
Oxidation
Issue Date2009
PublisherWiley - V C H Verlag GmbH & Co. KGaA. The Journal's web site is located at http://www.wiley-vch.de/publish/en/journals/alphabeticIndex/2451
Citation
Chemistry - An Asian Journal, 2009, v. 4 n. 10, p. 1551-1561 How to Cite?
AbstractSelective oxidation of amines using oxygen as terminal oxidant is an important area in green chemistry. In this work, we describe the use of graphite-supported gold nanoparticles (AuNPs/C) to catalyze aerobic oxidation of cyclic and acyclic benzylic amines to the corresponding imines with moderate-to-excellent substrate conversions (43-100%) and product yields (66-99%) (19 examples). Oxidation of N-substituted 1,2,3,4- tetrahydroisoquinolines in the presence of aqueous NaHCO3 solution gave the corresponding amides in good yields (83-93%) with high selectivity (up to amide/enamide=93:4) (6 examples). The same protocol can be applied to the synthesis of benzimidazoles from the reaction of o-phenylenediamines with benzaldehydes under aerobic conditions (8 examples). By simple centrifugation, AuNPs/C can be recovered and reused for ten consecutive runs for the oxidation of dibenzylamine to N-benzylidene(phenyl) methanamine without significant loss of catalytic activity and selectivity. This protocol "AuNPs/C+O 2" can be scaled to the gram scale, and 8.9 g (84% isolated yield) of 3,4-dihydroisoquinoline can be obtained from the oxidation of 10 g 1,2,3,4-tetrahydroisoquinoline in a onepot reaction. Based on the results of kinetic studies, radical traps experiment, and Hammett plot, a mechanism involving the hydrogen-transfer reaction from amine to metal and oxidation of M-H is proposed. © 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.
Persistent Identifierhttp://hdl.handle.net/10722/70095
ISSN
2015 Impact Factor: 4.592
2015 SCImago Journal Rankings: 1.833
ISI Accession Number ID
Funding AgencyGrant Number
Hong Kong Research Grants CouncilHKU 7009/06
CityU 2/06C
Innovation and Technology CouncilITS/189/08
Hong Kong SAR of ChinaAOE/P-10/01
Funding Information:

This work was supported by the Hong Kong Research Grants Council (HKU 7009/06 and CityU 2/06C), Innovation and Technology Council (ITS/189/08) and the University Grants Committee of the Hong Kong SAR of China (Area of Excellence Scheme AOE/P-10/01). We thank Dr. Raymond Wai-Yin Sun and Dr. Vanessa Kar-Yan.Lo for the assistance in the synthesis of various gold complexes. We offer our heartfelt thanks to Mr. Frankie Yu-Fee Chan and Mr. Wing-Sang Lee of Electron Microscope Unit of The University of Hong Kong for their technical assistance.

References
Grants

 

DC FieldValueLanguage
dc.contributor.authorSo, MHen_HK
dc.contributor.authorLiu, Yen_HK
dc.contributor.authorHo, CMen_HK
dc.contributor.authorChe, CMen_HK
dc.date.accessioned2010-09-06T06:19:40Z-
dc.date.available2010-09-06T06:19:40Z-
dc.date.issued2009en_HK
dc.identifier.citationChemistry - An Asian Journal, 2009, v. 4 n. 10, p. 1551-1561en_HK
dc.identifier.issn1861-4728en_HK
dc.identifier.urihttp://hdl.handle.net/10722/70095-
dc.description.abstractSelective oxidation of amines using oxygen as terminal oxidant is an important area in green chemistry. In this work, we describe the use of graphite-supported gold nanoparticles (AuNPs/C) to catalyze aerobic oxidation of cyclic and acyclic benzylic amines to the corresponding imines with moderate-to-excellent substrate conversions (43-100%) and product yields (66-99%) (19 examples). Oxidation of N-substituted 1,2,3,4- tetrahydroisoquinolines in the presence of aqueous NaHCO3 solution gave the corresponding amides in good yields (83-93%) with high selectivity (up to amide/enamide=93:4) (6 examples). The same protocol can be applied to the synthesis of benzimidazoles from the reaction of o-phenylenediamines with benzaldehydes under aerobic conditions (8 examples). By simple centrifugation, AuNPs/C can be recovered and reused for ten consecutive runs for the oxidation of dibenzylamine to N-benzylidene(phenyl) methanamine without significant loss of catalytic activity and selectivity. This protocol "AuNPs/C+O 2" can be scaled to the gram scale, and 8.9 g (84% isolated yield) of 3,4-dihydroisoquinoline can be obtained from the oxidation of 10 g 1,2,3,4-tetrahydroisoquinoline in a onepot reaction. Based on the results of kinetic studies, radical traps experiment, and Hammett plot, a mechanism involving the hydrogen-transfer reaction from amine to metal and oxidation of M-H is proposed. © 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.en_HK
dc.languageengen_HK
dc.publisherWiley - V C H Verlag GmbH & Co. KGaA. The Journal's web site is located at http://www.wiley-vch.de/publish/en/journals/alphabeticIndex/2451en_HK
dc.relation.ispartofChemistry - An Asian Journalen_HK
dc.subjectAminesen_HK
dc.subjectGolden_HK
dc.subjectHeterogeneous catalysisen_HK
dc.subjectNanoparticlesen_HK
dc.subjectOxidationen_HK
dc.subject.meshAmides - chemical synthesis-
dc.subject.meshCatalysis-
dc.subject.meshGold-
dc.subject.meshImines - chemical synthesis-
dc.subject.meshSubstrate Specificity-
dc.titleGraphite-supported gold nanoparticles as efficient catalyst for aerobic oxidation of benzylic amines to imines and N-substituted 1,2,3,4- tetrahydroisoquinolines to amides: Synthetic applications and mechanistic studyen_HK
dc.typeArticleen_HK
dc.identifier.openurlhttp://library.hku.hk:4550/resserv?sid=HKU:IR&issn=1861-4728&volume=4&issue=10&spage=1551&epage=1561&date=2009&atitle=Graphite-supported+gold+nanoparticles+as+efficient+catalyst+for+aerobic+oxidation+of+benzylic+amines+to+imines+and+N-substituted+1,2,3,4-+tetrahydroisoquinolines+to+amides:+Synthetic+applications+and+mechanistic+studyen_HK
dc.identifier.emailLiu, Y: lyg100@hku.hken_HK
dc.identifier.emailHo, CM: rickyho@hkucc.hku.hken_HK
dc.identifier.emailChe, CM: cmche@hku.hken_HK
dc.identifier.authorityLiu, Y=rp00749en_HK
dc.identifier.authorityHo, CM=rp00705en_HK
dc.identifier.authorityChe, CM=rp00670en_HK
dc.description.naturelink_to_subscribed_fulltext-
dc.identifier.doi10.1002/asia.200900261en_HK
dc.identifier.pmid19777526-
dc.identifier.scopuseid_2-s2.0-70349671007en_HK
dc.identifier.hkuros168961-
dc.relation.referenceshttp://www.scopus.com/mlt/select.url?eid=2-s2.0-70349671007&selection=ref&src=s&origin=recordpageen_HK
dc.identifier.volume4en_HK
dc.identifier.issue10en_HK
dc.identifier.spage1551en_HK
dc.identifier.epage1561en_HK
dc.identifier.isiWOS:000270768000007-
dc.publisher.placeGermanyen_HK
dc.relation.projectGreen Chemistry. Application of Nanotechnology in the Development of Highly Efficient and Environmental Friendly Chemical Synthesis.-
dc.relation.projectInstitute of molecular technology for drug discovery and synthesis-
dc.relation.projectGreen Oxidation Chemistry and Technology-
dc.identifier.scopusauthoridSo, MH=9275915300en_HK
dc.identifier.scopusauthoridLiu, Y=8225912600en_HK
dc.identifier.scopusauthoridHo, CM=12807243800en_HK
dc.identifier.scopusauthoridChe, CM=7102442791en_HK

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