Crystallographic characterisation of organolithium and organomagnesium intermediates in reactions of aldehydes and ketones

Lynch, Jennifer R. and Kennedy, Alan R. and Barker, Jim and Reid, Jacqueline and Mulvey, Robert E. (2022) Crystallographic characterisation of organolithium and organomagnesium intermediates in reactions of aldehydes and ketones. Helvetica Chimica Acta, 105 (9). e202200082. ISSN 0018-019X (https://doi.org/10.1002/hlca.202200082)

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Abstract

We report reactions of LiNacNac and NacNacMg(TMP) with common organic substrates (TMP=2,2,6,6-tetramethylpiperidide). Using bulky β-diketiminate compound NacNac (Me, Dipp), we have trapped metalated intermediates amenable to X-ray crystallographic study. LiNacNac and acetone produced the NacNac-free hexameric diacetone alkoxide [{LiO(MeC(=O)CH 2C(Me) 2} 6]; whereas pinacolone gave the simple monomeric donor–acceptor complex [Li{(MeCN-2,6- iPr 2C 6H 3) 2CH}{O=C(Me) tBu}]. Benzaldehyde produced dimeric [Li{(MeCN-2,6- iPr 2C 6H 3) 2CC(=O)Ph}{O=C(Ph)OCH 2Ph}] 2, where one benzaldehyde molecule has inserted in to the γ-carbon position of the NacNac ligand, with a molecule of benzyl benzoate derived from a Tishchenko reaction of the aldehyde acting as a terminal donor to lithium. Tetranuclear, mixed dimer [{LiO(MeCN-2,6- iPr 2C 6H 3) 2CH-CH(Ph)} 2{LiO(PhC(=O)} 2] containing the same modified NacNac ligand was the fortuitous product from repeating the reaction of LiNacNac and benzaldehyde in a solution presumably contaminated with benzoic acid. Combining NacNacMg(TMP) with pinacolone affords monomeric heteroleptic [Mg{(MeCN-2,6- iPr 2C 6H 3) 2CH}{OC( tBu)(Me)CH 2C(=O) tBu}] with an aldolate constituting the second anion. Completing the set is dimeric [Mg{(MeCN-2,6- iPr 2C 6H 3) 2CH}{O(C=CH 2)Ph} 2], where the enolate derived from acetophenone bridges the magnesium centres.

  • Item type:Article
    ID code:81923
    Dates:
    Date
    Event
    September 2022
    Published
    16 August 2022
    Published Online
    16 August 2022
    Accepted
    Subjects:Science > Chemistry
    Department:Faculty of Science > Pure and Applied Chemistry
    Depositing user: Pure Administrator
    Date deposited:18 Aug 2022 13:47
    Last modified:30 Apr 2024 01:10
    URI:https://strathprints.strath.ac.uk/id/eprint/81923
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