Synfacts 2009(5): 0489-0489  
DOI: 10.1055/s-0029-1216602
Synthesis of Heterocycles
© Georg Thieme Verlag Stuttgart ˙ New York

Asymmetric [3+2] Cycloaddition Route to Tetrahydrofurans

Contributor(s): Victor Snieckus, Timothy Hurst
A. T. Parsons, J. S. Johnson*
University of North Carolina at Chapel Hill, USA
Further Information

Publication History

Publication Date:
22 April 2009 (online)

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.