Allene:: As small in size as versatile in synthesis.: A general scope of its usefulness as a C3-synthon for carbocyclic annulations

Allenes react with silylcuprates leading to allyl- or vinyl-silanes depending on the structure of the allene and the nature of the silylcuprate. The silyl group used and temperature conditions can also influence the final outcome. Reversibility is a common trend found in these processes. In general, low order cyanosilylcuprates react with allenes, at low temperature, giving allylsilanes selectively. The intermediate allysilane-vinylcuprate can be captured with a wide variety of electrophiles affording functionalized allysilanes of great potential in organic synthesis. In particular, reaction with carbon electrophiles provides new opportunities for the carbocyclic synthesis of 5-, 6- and 7-membered rings, wherein the allenic system behaves, formally, as a nucleophilic C-3-synthon of high synthetic versatility.