Enantioselective 1,3-dipolar cycloaddition reactions between nitrones and α-substituted α,β-unsaturated aldehydes catalyzed by chiral cationic cobalt(III) complexes

The optically active β-ketoiminato cationic cobalt(III) complexes catalyzed the 1,3-dipolar cycloaddition reaction of nitrones with α,β-unsaturated aldehydes. In the reaction of nitrones derived from 2-halobenzaldehyde, excellent endo-selectivities and high enantioselectivities were observed. The α-substituted α,β-unsaturated aldehyde, such as 2-benzylpropenal, afforded the corresponding isoxazolidine in high stereoselectivity.