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Palladium was used in organic synthesis lyzed reactions can be classified into sevfor long time only as a heterogeneous eral groups based on their substrates: catalyst for hydrogenating unsaturated organic halides, allylic compounds, concompounds. But in recent years palladi-jugated dienes, alkenes, and alkynes. um compounds have found broad appli-Propargylic compounds undergo a varication as homogeneous catalysts. In the ety of palladium-catalyzed transformalast decade, homogeneous catalysis rely-tions and make up one important class ing on transition metal complexes has of these reactions. It is well known that led to innovations in organic synthesis. copper and silver salts promote or cataComplexes of various transition metals lyze several reactions of propargylic are now used for organic synthesis, and compounds. However, palladium comeach metal has its own characteristic fea-pounds, particularly Pdo complexes, tures. Palladium complexes are the most show catalytic activities entirely differversatile and used extensively in organic ent from those of silver and copper salts. synthesis, particularly for carbon-carAdvances in the research on the palladibon bond formation. Palladium-cata-um-catalyzed reactions of propargylic compounds in the last decade have made the scope of the reactions clear. The ready availability of numerous propargylic alcohols and their esters by the reaction of terminal alkynes with carbonyl compounds clearly enhances the synthetic utility of their reactions. Palladium complexes, in particular palladium phosphane complexes, are soluble in organic solvents and behave as active catalysts under homogeneous conditions.

Allylation of /3-keto esters or malonates was carried out in good yields under neutral conditions by using allylic carbonates in the presence of palladium-phosphine catalyst. Although simple ketones, esters, nitriles, and sulfones hardly react with allylic carbonates, -alkenyl or -aryl ketones, esters, nitriles, and sulfones were also allylated by using palladium-bis(diphenylphosphino)ethane catalyst under neutral conditions.We have reported the reaction of (v-allyljpalladium chloride (1) with carbonucleophiles such as malonates, acetoacetates, and enamines as a new method for carbon-carbon bond formation1 (Scheme I, eq 1). Later, in situ formation of (T-allyl)palladium complexes 2 as in-