Metal-Promoted Allylation, Propargylation, or Allenylation of Azetidine-2,3-diones in Aqueous and Anhydrous Media. Application to the Asymmetric Synthesis of Densely Functionalized 3-Substituted 3-Hydroxy-β-lactams
摘要:
Metal-mediated carbonyl allylation, allenylation, and propargylation of optically pure azetidine-2,3-diones were investigated in both anhydrous and aqueous environments. Different metals promoters showed varied regioselectivities on product formation during allenylation/propargylation reactions of the keto-beta -lactams. The stereochemistry of the new C3-substituted C3-hydroxy quaternary center was controlled by placing a chiral auxiliary at C4. In this way, the coupling of azetidine-2,3-diones with a variety of propenyl-, propynyl-, and allenylmetal reagents offers a convenient asymmetric entry to potentially bioactive 3-substituted 3-hydroxy-beta -lactams.
Regio- and Stereocontrolled Metal-Mediated Carbonyl Propargylation or Allenylation of Enantiomerically Pure Azetidine-2,3-diones: Synthesis of Highly Functionalized 3-Substituted 3-Hydroxy-β-lactams
Regio and stereocontrolled metal-mediated Barbier-type reactions of azetidine-2,3-diones with differently substituted propargyl bromides offer an efficient asymmetric entry to densely functionalized 3-propargyl- (or allenyl-) substituted 3-hydroxy-beta-lactams.