Metal-Mediated Carbonyl-1,3-butadien-2-ylation by 1,4-Bis(methanesulfonyl)-2-butyne or 1,4-Dibromo-2-butyne in Aqueous Media: Asymmetric Synthesis of 3-Substituted 3-Hydroxy-β-lactams
摘要:
Metal-mediated 1,3-butadien-2-ylation reactions between 1,4-dibromo-2-butyne or 1,4-bis(methanesulfonyl)-2-butyne and optically pure azetidine-2,3-diones were investigated in aqueous media, offering a convenient asymmetric entry to the potentially bioactive 3-substituted 3-hydroxy-beta-lactam moiety. The diastereoselectivity of the addition reaction was controlled by the bulky chiral auxiliary at C4. However, while the regioselectivity of the process was full, the chemical yield of the addition was a function of the nature of both the metal reagent and the system solvent as well. In addition, 2-azetidinone-tethered 1,3-butadienes can easily be transformed into other functionalities via Diels-Alder reaction.
A Novel Use of Grubbs' Carbene. Application to the Catalytic Deprotection of Tertiary Allylamines
作者:Benito Alcaide、Pedro Almendros、Jose M. Alonso、Moustafa F. Aly
DOI:10.1021/ol0167412
日期:2001.11.1
[reaction--see text] The first examples accounting for the catalytic deprotection of allylicamines by using reagents different from palladium catalysts have been achieved via Grubbs' carbene-mediated reaction. The current mechanistic hypothesis invokes a nitrogen-assisted ruthenium-catalyzed isomerization, followed by hydrolysis of the enamine intermediate. We believe that an unprecedented mode of ring