Turning unreactive copper acetylides into remarkably powerful and mild alkyne transfer reagents by oxidative umpolung.

This is not breaking news: copper acetylides, readily available polymeric rock-stable solids, have been known for more than a century to be unreactive species and piteous nucleophiles. This lack of reactivity actually makes them ideal alkyne transfer reagents that can be easily activated under mild oxidizing conditions. When treated with molecular oxygen in the presence of simple chelating nitrogen ligands such as TMEDA, phenanthroline or imidazole derivatives, they are smoothly oxidized to highly electrophilic species that formally behave like acetylenic carbocations and can therefore be used for the mild and practical alkynylation of a wide range of nitrogen, phosphorus and carbon nucleophiles.

Synthesis of alpha-substituted allylic amines via a modified bruylants reaction

Silver tetrafluoroborate, used as an iminium ion promoter from alpha-amino nitriles, is an efficient additive in the Bruylants reaction involving vinylic Grignards. Improved yields of allylic amines were obtained when the starting alpha-amino nitrile was treated with this silver salt prior to its reaction with the vinylic Grignard. This improvement was not observed in the case of acetylenic Grignards. The reactivity of other vinyl organometallics (M = Zn, Li, Al, Cu, Si) was briefly examined.