Formation of δ-Lactones with <i>anti</i>
-Baeyer-Villiger Regiochemistry: Investigations into the Mechanism of the Cerium-Catalyzed Aerobic Coupling of β-Oxoesters with Enol Acetates
作者:Irina Geibel、Anna Dierks、Thomas Müller、Jens Christoffers
DOI:10.1002/chem.201605468
日期:2017.5.29
The cerium-catalyzed, aerobic coupling of β-oxoesters with enol acetates and dioxygen yields δ-lactones with a 1,4-diketone moiety. In contrast to the Baeyer-Villiger oxidation (BVO), where the higher substituted residue migrates, in this case of an oxidative C-C coupling reaction the less substituted alkyl residue undergoes a 1,2-shift. An endoperoxidic oxycarbenium ion comparable to the Criegee intermediate
铈催化的β-氧代酸酯与烯醇乙酸酯和双氧的需氧偶联产生具有1,4-二酮部分的δ-内酯。与其中较高取代的残基迁移的Baeyer-Villiger氧化(BVO)相反,在氧化CC偶联反应的情况下,较少取代的烷基残基发生1,2-移位。与BVO中的Criegee中间体相当的内过氧化氧碳鎓离子被提议作为反应中间体,并通过计算方法进行构象分析。结果,逆立体化学可以通过主要的立体电子效应来解释。使用不同的供体和受体取代的烯醇酯进行的Hammett分析为转化率决定步骤中的关键中间体氧碳鎓离子提供了支持。