Synthesis of Functionalized Cyclopentenes through Catalytic Asymmetric [3+2] Cycloadditions of Allenes with Enones

✍ Scribed by Jonathan E. Wilson; Gregory C. Fu

• Publisher: John Wiley and Sons
• Year: 2006
• Tongue: English
• Weight: 112 KB
• Volume: 118
• Category: Article
• ISSN: 0044-8249
• DOI: 10.1002/ange.200503312

✦ Synopsis

Five-membered carbocycles are a common substructure in a wide array of natural and nonnatural products. [1] Among this family of compounds, cyclopentenes are particularly important targets, in part because derivatization of the olefin often occurs with good diastereoselectivity, thereby providing access to highly functionalized, stereochemically complex cyclopentanes. Although considerable progress has been described in developing methods for the asymmetric synthesis of cyclopentenes, the number of effective catalytic enantioselective processes is comparatively small. [2] Recently, nucleophilic catalysis by phosphines has emerged as a powerful tool in synthetic organic chemistry. [3] For example, tertiary phosphines catalyze a variety of annulation reactions, including Lus [3+2] cycloaddition of allenes with olefins to generate cyclopentenes. [4] In 1997, Zhang et al. reported a pioneering study in which he established that a chiral phosphine can furnish good enantioselectivity in this process; with respect to scope, only unsubstituted acrylate esters and diethyl maleate react with the allene to form the target cyclopentenes in high enantiomeric excess (ee) [Eq. ( 1) and ( 2)].