A new method has been demonstrated to solve the aggregation issue of metalcomplex catalysts; Steric protection of the metal center of catalysts was effective in the cases of DBFOX/Ph-transition metalcomplexes by structural modification of chiral ligand. The new ligands have been successfully applied to the nitrone cycloadditions to a variety of α,β-unsaturated aldehydes. Excellent enantioselectivities
Chiral DBFOX/Ph Complex Catalyzed Enantioselective Nitrone Cycloadditions to α,β-Unsaturated Aldehydes
作者:Moto Shirahase、Shuji Kanemasa、Yoji Oderaotoshi
DOI:10.1021/ol0361148
日期:2004.3.1
1,3-Dipolar cycloadditions of nitrones with alpha-alkyl- and alpha-arylacroleins are catalyzed with the DBFOX/Ph complexes of nickel(II) and magnesium(II) salts to produce the sterically controlled isoxazolidine-5-carbaldehydes, while the reactions with alpha-bromoacrolein are effectively catalyzed with the zinc(II) complexes to produce the electronically controlled isoxazolidine-4-carbaldehydes.