Palladium-catalysed addition of tin-tin and tin-silicon bonds to allenes

Hexamethyl-, hexaethyl- and hexabutyl-ditin add to a variety of allenes in the presence of Pd(PPh 3 ) 4 ; the reaction is reversible. Trimethylsilyltrimethyl- and -tributyl-stannane also add under comparable conditions, the silyl moiety becoming attached to the central carbon atom of the allene skeleton; this reaction is, however, apparently not reversible