A potential role of substrate as a base for deprotonation pathway in Rh-catalysed C-H amination of heteroArenes: DFT insights

Handle URI:
http://hdl.handle.net/10754/604353
Title:
A potential role of substrate as a base for deprotonation pathway in Rh-catalysed C-H amination of heteroArenes: DFT insights
Authors:
Ajitha, Manjaly John; Huang, Kuo-Wei ( 0000-0003-1900-2658 ) ; Kwak, Jaesung; Kim, Hyun Jin; Chang, Sukbok; Jung, Yousung
Abstract:
The possibility of direct introduction of a new functionality through C–H bond activation is an attractive strategy in covalent synthesis. Here, we investigated the mechanism of Rh-catalysed C-H amination of the hetero-aryl substrate (2-phenylpyridine) using phenyl azide as nitrogen source by density functional theory (DFT). For the deprotocyclometallation and protodecyclometallation processes of the title reaction, we propose a stepwise base-assisted mechanism (pathway I) instead of previously reported concerted mechanism (pathway II). In the new mechanism proposed here, 2-phenylpyridine acts as a base in the initial deprotonation step (C-H bond cleavage) and transports the proton towards the final protonation step. In fact, the N-H bond of the strong conjugate acid (formed during initial C-H bond cleavage) considered in pathway I (via TS4) is more acidic than the C-H bond of the neutral substrate considered in pathway II (via TS5). The higher activation barrier of TS5 mainly originates from the ring strain of the four membered cyclic transition state. The vital role of base, as disclosed here, can potentially have broader mechanistic implications for the development of reaction conditions of transition metal catalysed reactions.
KAUST Department:
KAUST Catalysis Center (KCC); Physical Sciences and Engineering (PSE) Division
Citation:
A potential role of substrate as a base for deprotonation pathway in Rh-catalysed C-H amination of heteroArenes: DFT insights 2016 Dalton Trans.
Publisher:
Royal Society of Chemistry (RSC)
Journal:
Dalton Trans.
Issue Date:
29-Mar-2016
DOI:
10.1039/C6DT00686H
Type:
Article
ISSN:
1477-9226; 1477-9234
Sponsors:
This work was supported by the National Research Foundation of Korea Grant (NRF-2015R1A2A1A15055539) funded by Korean Government. The generous support from computation facilities at the KAUST IT and Supercomputing Lab as well as KISTI is also acknowledged.
Additional Links:
http://pubs.rsc.org/en/Content/ArticleLanding/2016/DT/C6DT00686H
Appears in Collections:
Articles; Physical Sciences and Engineering (PSE) Division; KAUST Catalysis Center (KCC)

Full metadata record

DC FieldValue Language
dc.contributor.authorAjitha, Manjaly Johnen
dc.contributor.authorHuang, Kuo-Weien
dc.contributor.authorKwak, Jaesungen
dc.contributor.authorKim, Hyun Jinen
dc.contributor.authorChang, Sukboken
dc.contributor.authorJung, Yousungen
dc.date.accessioned2016-04-04T13:11:56Zen
dc.date.available2016-04-04T13:11:56Zen
dc.date.issued2016-03-29en
dc.identifier.citationA potential role of substrate as a base for deprotonation pathway in Rh-catalysed C-H amination of heteroArenes: DFT insights 2016 Dalton Trans.en
dc.identifier.issn1477-9226en
dc.identifier.issn1477-9234en
dc.identifier.doi10.1039/C6DT00686Hen
dc.identifier.urihttp://hdl.handle.net/10754/604353en
dc.description.abstractThe possibility of direct introduction of a new functionality through C–H bond activation is an attractive strategy in covalent synthesis. Here, we investigated the mechanism of Rh-catalysed C-H amination of the hetero-aryl substrate (2-phenylpyridine) using phenyl azide as nitrogen source by density functional theory (DFT). For the deprotocyclometallation and protodecyclometallation processes of the title reaction, we propose a stepwise base-assisted mechanism (pathway I) instead of previously reported concerted mechanism (pathway II). In the new mechanism proposed here, 2-phenylpyridine acts as a base in the initial deprotonation step (C-H bond cleavage) and transports the proton towards the final protonation step. In fact, the N-H bond of the strong conjugate acid (formed during initial C-H bond cleavage) considered in pathway I (via TS4) is more acidic than the C-H bond of the neutral substrate considered in pathway II (via TS5). The higher activation barrier of TS5 mainly originates from the ring strain of the four membered cyclic transition state. The vital role of base, as disclosed here, can potentially have broader mechanistic implications for the development of reaction conditions of transition metal catalysed reactions.en
dc.description.sponsorshipThis work was supported by the National Research Foundation of Korea Grant (NRF-2015R1A2A1A15055539) funded by Korean Government. The generous support from computation facilities at the KAUST IT and Supercomputing Lab as well as KISTI is also acknowledged.en
dc.language.isoenen
dc.publisherRoyal Society of Chemistry (RSC)en
dc.relation.urlhttp://pubs.rsc.org/en/Content/ArticleLanding/2016/DT/C6DT00686Hen
dc.rightsArchived with thanks to Dalton Trans.en
dc.titleA potential role of substrate as a base for deprotonation pathway in Rh-catalysed C-H amination of heteroArenes: DFT insightsen
dc.typeArticleen
dc.contributor.departmentKAUST Catalysis Center (KCC)en
dc.contributor.departmentPhysical Sciences and Engineering (PSE) Divisionen
dc.identifier.journalDalton Trans.en
dc.eprint.versionPost-printen
dc.contributor.institutionGraduate School of EEWS, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 305-701, Koreaen
dc.contributor.institutionCenter for Catalytic Hydrocarbon Functionalizations, Institute for Basic Science (IBS), Daejeon 305-701, Koreaen
dc.contributor.institutionDepartment of Chemistry, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 305-701, Koreaen
dc.contributor.affiliationKing Abdullah University of Science and Technology (KAUST)en
kaust.authorAjitha, Manjaly Johnen
kaust.authorHuang, Kuo-Weien
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