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  • Title: Straightforward asymmetric entry to highly functionalized 3-substituted 3-hydroxy-beta-lactams via Baylis-Hillman or bromoallylation reactions.
    Author: Alcaide B, Almendros P, Aragoncillo C, Rodríguez-Acebes R.
    Journal: J Org Chem; 2004 Feb 06; 69(3):826-31. PubMed ID: 14750811.
    Abstract:
    The reaction of various activated vinyl systems, including 2-cyclopenten-1-one, with enantiopure azetidine-2,3-diones 1 was promoted by DABCO to afford the corresponding optically pure Baylis-Hillman adducts 2 without detectable epimerization. However, the reaction of alpha-keto lactams 1 with but-3-yn-2-one was not as successful, giving the corresponding beta-halo Baylis-Hillman adduct in low yield. Metal-mediated bromoallylation reaction between 2,3-dibromopropene and azetidine-2,3-diones 1 was investigated in aqueous media. Surprisingly, indium was unable to promote the bromoallylation reaction of alpha-keto lactams 1, but the Sn-Hf(4)Cl-promoted bromoallylation of ketones 1 proceeded efficiently to achieve bromohomoallyl alcohols 5 as single diastereomers. On this basis, simple and fast protocols for the asymmetric synthesis of the potentially bioactive 3-substituted 3-hydroxy-beta-lactam moiety were developed.
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