Phosphine-catalyzed regio- and stereo-selective hydroboration of ynamides to ( Z )-β-borylenamides.

We report a tri- n -butyl phosphine catalyzed regio- and stereo-selective hydroboration of ynamides to yield ( Z )-β-borylenamides in good yields. Surprisingly, a formal cis addition to the triple bond was observed as confirmed by NMR and X-ray crystallography. 31 P NMR studies suggest that a zwitterionic vinylphosphonium intermediate is key in the mechanism. The resulting products were further transformed to β-CF 3 enamides via stereoretentive trifluoromethylation.