Preparation and Reactions of Mono- and Bis-Pivaloyloxyzinc Acetylides

Mono-pivaloyloxyzinc acetylide and bis-pivaloyloxyzinc acetylide were selectively prepared from ethynylmagnesium bromide in quantitative yields. These zinc reagents readily underwent Negishi cross-couplings with (hetero)aryl iodides or bromides as well as subsequent Sonogashira cross-couplings. 1,3-Dipolar cycloadditions of these zinc acetylides with benzylic azides produced zincated and bis-zincated triazoles which were trapped with several electrophiles. An opposite regioselectivity compared to the Cu-catalyzed click-reactions was observed.