Chiral Oxazaborolidine-Aluminum Bromide Complexes Are Unusually Powerful and Effective Catalysts for Enantioselective Diels-Alder Reactions

J. Am. Chem. Soc., 129 (6), 1498 -1499, 2007. 10.1021/ja068637r S0002-7863(06)08637-9
Web Release Date: January 19, 2007

Chiral Oxazaborolidine-Aluminum Bromide Complexes Are Unusually Powerful and Effective Catalysts for Enantioselective Diels-Alder Reactions

Duan Liu, Eda Canales, and E. J. Corey*

Department of Chemistry and Chemical Biology, Harvard University, Cambridge, Massachusetts 02138

corey@chemistry.harvard.edu

Received December 1, 2006

Abstract:

Treatment of the chiral oxazaborolidine 1 with AlBr₃ generates the 1:1 complex 3, which is an even more potent Lewis acid catalyst than protonated 1 (i.e., 2) for enantioselective Diels-Alder reactions. Only 4 mol % of catalyst 3 is required to achieve yields and enantiomeric purities of 90% over a broad range of achiral dienes and dienophiles. The ligand from which 3 is derived can be recovered easily and with high efficiency. The method is illustrated by 22 examples.

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