Syntheses with Polyfunctional Organomagnesium Compounds

The main synthetic applications of the "heterofunctional" or "polyfunctional" organomagnesium reagents obtained by substituting MgX or Mg for a labile hydrogen atom (metallation reaction, I) are reviewed. The various functional groups present in the molecules of these reagents make them interesting from the point of view of organic synthesis. The present survey does not include the reagents formed directly (reaction II) or through exchange (reaction III). The metallation of terminal triple bonds in acetylenic compounds has been long known. The considerable acidity of the hydrogen atom in the H-C = C- group makes these compounds markedly different from the remaining CH-acidic ones; therefore, they shall not be considered in the present discussion.