Stereoselective Synthesis of ( Z )-β-Enamido Fluorides from N -Fluoroalkyl- and N -Sulfonyl-1,2,3-triazoles.

A reaction of N -sulfonyl-1,2,3-triazole with boron trifluoride etherate afforded a ( Z )-β-ensulfonylamido fluoride instead of the previously erroneously assigned E isomer. The correction of the stereochemistry was based on a ge-1D ROESY NMR experiment and X-ray crystal structure analyses. Application of the reaction to N -fluoroalkyl-1,2,3-triazoles afforded new ( Z )-β-enamido fluorides in a stereoselective manner. A mechanism involving coordination of BF ₃ with the triazole ring and vinyl diazonium and vinyl cation intermediates was proposed.