(Z)-Trifluoromethyl-Trisubstituted Alkenes or Isoxazolines: Divergent Pathways from the Same Allene.

Because of a charge-dipole interaction involving nonbonding electron pairs on fluorine, protonation of trifluoromethyl allenes leads to tri- or tetrasubstituted alkenes with high (Z)-selectivity. Treatment of the same allenes with catalytic Au(I) initiates a reaction cascade that produces isoxazolines in high yield.