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Keywords:

  • [4+2] annulations;
  • allenoates;
  • asymmetric catalysis;
  • cinchona catalysts;
  • organocatalysis
Thumbnail image of graphical abstract

Biologically significant polysubstituted dihydropyrans have been prepared in high to excellent yields and enantioselectivities (see scheme). The interaction between functional groups in the zwitterionic intermediate, which is generated by addition of the amine catalyst to the allenoate substrate, is thought to play a crucial role in the stereochemical outcome. Bn=benzyl, DMAP=4-dimethylaminopyridine.