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Keywords:

  • acetylenic aldehydes;
  • dipolar [3+2] cycloadditions;
  • enantioselectivity;
  • iminium activation;
  • nitrones

Abstract

The first organocatalytic enantioselective protocol has been developed for the dipolar [3+2] cycloaddition between acetylenic aldehydes and nitrones through an iminium activation pathway. This protocol uses L-α,α-bis(3,5-ditrifluoromethylphenyl)prolinol as catalyst and 3,5-dinitrobenzoic acid as additive and is friendly for one-pot operation for the nitrone formation and the subsequent cycloaddition. It also exhibits a broad substrate scope and allows for the highly efficient production of chiral 4-isoxazolines with various substituents under mild conditions in high yields (68–92%) with high enantioselectivities (up to 96% ee).