Synthesis of allenylidene lithium and silver complexes, and subsequent transmetalation reactions.

Alpha, beta, gamma! Amino substituents in alpha and beta positions allow the isolation of free carbenes, but even in the gamma position, their strong pi-electron-donating properties permit the synthesis of allenylidene lithium adducts and silver complexes (see picture), which are ideal precursors for the preparation of various transition-metal-allenylidene complexes.