https://scholars.lib.ntu.edu.tw/handle/123456789/612097
Title: | A family of N-heterocyclic carbene-stabilized borenium ions for metal-free imine hydrogenation catalysis | Authors: | Farrell, Jeffrey M. Posaratnanathan, Roy T. Stephan, Douglas W. JEFFREY M. FARRELL |
Issue Date: | 2015 | Journal Volume: | 6 | Journal Issue: | 3 | Start page/Pages: | 2010-2015 | Source: | CHEMICAL SCIENCE | Abstract: | This manuscript probes the steric and electronic attributes that lead to "frustrated Lewis pair" (FLP)-type catalysis of imine hydrogenation by borenium ions. Hydride abstraction from (ItBu)HB(C6F5)2 2 prompts intramolecular C-H bond activation to give (CHN)2(tBu) (CMe2CH2)CB(C6F5)2 3, defining an upper limit of Lewis acidity for FLP hydrogenation catalysis. A series of seven N-heterocyclic carbene-borane (NHC-borane) adducts ((R′CNR)2C)(HBC8H14) (R′ = H, R = dipp 4a, Mes 5a, Me 8a; R = Me R′ = Me 9a, Cl, 10a) and ((HC)2(NMe)(NR)C)(HBC8H14) (R = tBu, 6a, Ph 7a) are prepared and converted to corresponding borenium salts. These species are evaluated as catalysts for metal-free imine hydrogenation at room temperature. Systematic tuning of the carbene donor for the hydrogenation of archetypal substrate N-benzylidene-tert-butylamine achieves the highest reported turn-over frequencies for FLP-catalyzed hydrogenation at amongst the lowest reported catalyst loadings. The most active NHC-borenium catalyst of this series, derived from 10a, is readily isolable, crystallographically characterized and shown to be effective in the hydrogenation catalysis of functional group-containing imines and N-heterocycles. ? The Royal Society of Chemistry 2015. |
URI: | https://www.scopus.com/inward/record.uri?eid=2-s2.0-84923163524&doi=10.1039%2fc4sc03675a&partnerID=40&md5=f76d21e69bf53dfd1b751b058f82aa9f https://scholars.lib.ntu.edu.tw/handle/123456789/612097 |
DOI: | 10.1039/c4sc03675a | SDG/Keyword: | Catalysis; Catalysts; Nitrogen compounds; Organic compounds; Catalyst loadings; CH-bond activation; Frustrated lewis pairs; Hydride abstraction; Hydrogenation catalysis; N-heterocyclic carbenes; Room temperature; Turnover frequency; Hydrogenation |
Appears in Collections: | 化學系 |
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