Alkali metal dihydropyridines in transfer hydrogenation catalysis of imines : amide basicity versus hydride surrogacy
MacDonald, Peter A. and Banerjee, Sumanta and Kennedy, Alan R. and van Teijlingen, Alexander and Robertson, Stuart D. and Tuttle, Tell and Mulvey, Robert E. (2023) Alkali metal dihydropyridines in transfer hydrogenation catalysis of imines : amide basicity versus hydride surrogacy. Angewandte Chemie International Edition, 62 (27). e202304966. ISSN 1521-3773 (https://doi.org/10.1002/anie.202304966)
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Abstract
Catalytic reduction of a representative set of imines, both aldimines and ketimines, to amines has been studied using transfer hydrogenation from 1,4-dicyclohexadiene. Unusually, this has been achieved using s-block pre-catalysts, namely 1-metallo-2-tert-butyl- 1,2-dihydropyridines, 2-tBuC5H5NM, M(tBuDHP), where M = Li-Cs. Reactions have been monitored in C6D6 and tetrahydrofuran-d8 (THFd8). A definite trend is observed in catalyst efficiency with the heavier alkali metal tBuDHPs outperforming the lighter congeners. In general, Cs(tBuDHP) is the optimal pre-catalyst with, in the best cases, reactions producing quantitative yields of amines in minutes at room temperature using 5 mol% catalyst. Supporting the experimental study, Density Functional Theory (DFT) calculations have also been carried out which reveal that Cs has a pathway with a significantly lower rate determining step than the Li congener. In the postulated initiation pathways DHP can act as either a base or as a surrogate hydride.
ORCID iDs
MacDonald, Peter A., Banerjee, Sumanta, Kennedy, Alan R. ORCID: https://orcid.org/0000-0003-3652-6015, van Teijlingen, Alexander ORCID: https://orcid.org/0000-0002-3739-8943, Robertson, Stuart D. ORCID: https://orcid.org/0000-0002-9330-8770, Tuttle, Tell and Mulvey, Robert E. ORCID: https://orcid.org/0000-0002-1015-2564;-
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Item type: Article ID code: 85379 Dates: DateEvent3 July 2023Published3 May 2023Published Online3 May 2023Accepted11 April 2023SubmittedSubjects: Science > Chemistry Department: Faculty of Science > Pure and Applied Chemistry
Technology and Innovation Centre > BionanotechnologyDepositing user: Pure Administrator Date deposited: 03 May 2023 14:57 Last modified: 11 Nov 2024 13:56 URI: https://strathprints.strath.ac.uk/id/eprint/85379