Metal-mediated or -catalyzed retro-allylation of homoallyl alcohol has emerged as a new useful method for preparing allylmetals. The metal alkoxides of well-designed homoallyl alcohols undergo retro-allylation via chairlike six-membered transition states. Thanks to the rigid transition states, the retro-allylation reactions proceed regio- and stereo specifically, yielding regio- and stereochemically well-defined allylmetals. The allylmetals thus generated are used in situ, which can afford allylated products with high selectivity. Retro-allylation reactions mediated by zirconium, gallium, palladium, and rhodium are described. Reversible additions of pentamethylcyclopentadienyl anion to carbonyl compounds are also described.