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DOI: 10.1055/s-0029-1216602
Asymmetric [3+2] Cycloaddition Route to Tetrahydrofurans
A. T. Parsons, J. S. Johnson*
University of North Carolina at Chapel Hill, USA
Publication History
Publication Date:
22 April 2009 (online)
![](https://www.thieme-connect.de/media/synfacts/200905/lookinside/thumbnails/10.1055-s-0029-1216602-1.jpg)
Significance
Johnson and co-workers report a simple and efficient enantioselective synthesis of tetrahydrofurans 3 through the asymmetric [3+2] cycloaddition of racemic cyclopropanes 1 with aldehydes 2. Optimization of the reaction conditions identified MgI2/(t-Bu-pybox) as the best system for the stereospecific cycloaddition of one enantiomer of the cyclopropane whilst simultaneously promoting interconversion of both enantiomers through dynamic kinetic resolution. Cyclopropanes bearing donating groups are required for efficient ring opening and cycloaddition. The reaction is tolerant of electron-rich aryl, cinnamyl, linear and branched aliphatic aldehydes, although electron-poor aldehydes gave lower yields presumably due to their poor nucleophilicity. Excellent enantio- and diastereoselectivity was observed in all cases.