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 BF3 with the triazole ring and vinyl diazonium and vinyl cation intermediates was proposed.