β-内酯亲电体会与多种基于氮的亲核体发生区域选择性加成-消除(AE)或S N 2开环。伯胺和仲胺可促进AE开环,从而提供功能上与酰胺醇醛加合物相同的产品。叠氮化物和磺酰胺阴离子亲核试剂使S N 2内酯开环传递N保护的β-氨基酸衍生物。这些依赖亲核试剂的开环途径,再加上通过酰基卤-醛环缩合反应获得的富含大量庚酮的β-内酯的便捷途径,构成了不对称有机合成的通用方法。还描述了该反应技术在基于从AAC开环序列中出现的旋光性β-叠氮酸的β肽合成新方法中的应用。
Asymmetric [2 + 2] cycloaddition of ketene with the aldehydes 1aâg, catalysed by 10 mol% of C2-symmetric bissulfonamide 2aâcâR3Al complexes afforded optically active 4-substituted oxetan-2-ones 3aâg in up to 74% enantiomeric excess.
Enantioselective β-Lactone Formation from Ketene and Aldehydes Catalyzed by a Chiral Oxazaborolidine
作者:Vijay Gnanadesikan、E. J. Corey
DOI:10.1021/ol061979h
日期:2006.10.1
[reaction: see text] A novel catalytic system has been developed for the enantioselective synthesis of beta-lactones from ketene and aldehydes.
[反应:见正文]已开发出一种新型催化体系,用于从烯酮和醛类对映体选择性合成β-内酯。
Catalytic Asymmetric Synthesis of trans-Configured β-Lactones: Cooperation of Lewis Acid and Ion Pair Catalysis
作者:Thomas Kull、José Cabrera、René Peters
DOI:10.1002/chem.201000840
日期:——
development of the first trans‐selective catalytic asymmetric [2+2] cyclocondensation of acyl halides with aliphatic aldehydes furnishing 3,4‐disubstituted β‐lactones is described. This work made use of a new strategy within the context of asymmetric dual activation catalysis: it combines the concepts of Lewisacid and organic aprotic ionpaircatalysis in a single catalyst system. The methodology could
Practical Enantioselective Synthesis of β-Lactones Catalyzed by Aluminum Bissulfonamide Complexes
作者:Thomas Kull、René Peters
DOI:10.1002/adsc.200700084
日期:2007.7.2
practical aluminum-bissulfonamide complex catalyzed enantioselective formation of β-lactones by [2+2] cycloaddition of ketene (generated in situ from acetyl bromide by dehydrobromination) with various α-unbranched and -branched aliphatic aldehydes is presented. The methodology offers the advantage of operational simplicity not only as the ligand synthesis requires just a single sulfonylation step from commercially
Cinchona Alkaloid-Lewis Acid Catalyst Systems for Enantioselective Ketene−Aldehyde Cycloadditions
作者:Cheng Zhu、Xiaoqiang Shen、Scott G. Nelson
DOI:10.1021/ja0492900
日期:2004.5.1
Asymmetric cinchona alkaloid-catalyzed acid chloride-aldehyde cyclocondensation (AAC) reactions afford enantioenriched 4-substituted and 3,4-disubstituted beta-lactones with near perfect absolute and relative stereocontrol. These reactions are characterized by the operational simplicity derived from using commercially available or easily obtained (one-step) reaction catalysts and in situ ketene generation from acid chlorides. The range of aldehyde substrates that serve as effective AAC substrates include sterically hindered aldehydes such as cyclohexanecarboxaldehyde and pivaldehyde.