Selective Preparation and Reactions of Propargylic Grignard Reagents

Significance

Propargylic Grignard reagents are important intermediates in synthesis. The preparation of the unsubstituted reagent was previously possible only using a toxic mercury catalyst. A catalytic amount of ZnBr₂ offers an excellent alternative to mercury in this process, now allowing a simple preparation of various propargylmagnesium bromides in good yields. Several examples demonstrated excellent selectivity of these reagents in reactions with ketones and allylic electro­philes.