1-Alkali-metal-2-alkyl-1,2-dihydropyridines : soluble hydride surrogates for catalytic dehydrogenative coupling and hydroboration applications

McLellan, Ross and Kennedy, Alan R. and Mulvey, Robert E. and Orr, Samantha A. and Robertson, Stuart D. (2017) 1-Alkali-metal-2-alkyl-1,2-dihydropyridines : soluble hydride surrogates for catalytic dehydrogenative coupling and hydroboration applications. Chemistry - A European Journal, 23 (66). pp. 16853-16861. ISSN 0947-6539 (https://doi.org/10.1002/chem.201703609)

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Abstract

Equipped with excellent hydrocarbon solubility, the lithium hydride surrogate 1-lithium-2-t-butyl-1,2-dihydropyridine (1tLi) functions as a precatalyst to convert Me2NH·BH3 to [NMe2BH2]2 (89% conversion) under competitive conditions (2.5 mol%, 60h, 80°C, toluene solvent) to that of previously reported LiN(SiMe3)2. Sodium and potassium dihydropyridine congeners produce similar high yields of [NMe2BH2]2 but require longer times. Switching the solvent to pyridine induces a remarkable change in the dehydrocoupling product ratio, with (NMe2)2BH favoured over [NMe2BH2]2 (e.g., 94%:2% for 1tLi). Demonstrating its versatility, precatalyst 1tLi was also successful in promoting hydroboration reactions between pinacolborane and a selection of aldehydes and ketones. Most reactions gave near quantitative conversion to the hydroborated products in 15 minutes, though sterically demanding carbonyl substrates require longer times. The mechanisms of these rare examples of group 1 metal catalysed processes are discussed.

ORCID iDs

McLellan, Ross ORCID logoORCID: https://orcid.org/0000-0001-9700-0258, Kennedy, Alan R. ORCID logoORCID: https://orcid.org/0000-0003-3652-6015, Mulvey, Robert E. ORCID logoORCID: https://orcid.org/0000-0002-1015-2564, Orr, Samantha A. ORCID logoORCID: https://orcid.org/0000-0001-9295-9312 and Robertson, Stuart D. ORCID logoORCID: https://orcid.org/0000-0002-9330-8770;
  • Item type:Article
    ID code:61912
    Dates:
    Date
    Event
    27 November 2017
    Published
    21 September 2017
    Published Online
    25 August 2017
    Accepted
    Notes:This is the peer reviewed version of the following article: McLellan, R., Kennedy, A. R., Mulvey, R. E., Orr, S. A. and Robertson, S. D. (), 1-Alkali-metal-2-alkyl-1,2-dihydropyridines: soluble hydride surrogates for catalytic dehydrogenative coupling and hydroboration applications. Chem. Eur. J., which has been published in final form at https://doi.org/10.1002/chem.201703609. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving.
    Keywords:soluble hydride surrogates, 1-lithium-2-t-butyl-1,2-dihydropyridine, 1tLi, Chemistry, Chemistry(all)
    Subjects:Science > Chemistry
    Department:Faculty of Science > Pure and Applied Chemistry
    Depositing user: Pure Administrator
    Date deposited:02 Oct 2017 14:14
    Last modified:28 Mar 2023 09:48
    Related URLs:
    URI:https://strathprints.strath.ac.uk/id/eprint/61912
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