Lewis acid-mediated [3+2] cycloaddition between hydrazones and olefins

摘要

[3+2] Cycloaddition between hydrazones and olefins was accelerated in the presence of a stoichiometric amount of BF_3·OEt_2 or a catalytic amount of Zr(OTf)_4, Hf(OTf)_4, or Sc(OTf)_3 under mild conditions. The corresponding pyrazolidine derivatives were obtained in moderate to high yields using this novel [3+2] Lewis acid catalysis.