Addition reactions tris dipalladium

Buchwald has shown that, in combination with palladium(II) acetate or Pd2(dba)3 [tris(dibenzylideneacetone)dipalladium], the Merrifield resin-bound electron-rich dialkylphosphinobiphenyl ligand (45) (Scheme 4.29) forms the active polymer-supported catalysts for amination and Suzuki reactions [121]. Inactivated aryl iodides, bromides, or even chlorides can be employed as substrates in these reactions. The catalyst derived from ligand (45) and a palladium source can be recycled for both amination and Suzuki reactions without addition of palladium. 

Similarly, reaction of tris(dibenzylideneacetone)dipalladium with two equivalents of f-butylisocyanide per Pd atom, followed by addition of OFCOT, leads to an analogous ring-closed product 99a. Reaction of [Pd(PPh3)4] with OFCOT afforded the phosphine analogue 99b (174). No attempts have been made to probe any further chemistry of these molecules. 

Tris(dibenzylideneacetone)dipalladium. 14, 339 15, 353-355 16, 372 17, 394 Addition to unsaturated systems. Allylsilanes are produced in a Pd(0)-cata-lyzed reaction of conjugated dienes, organodisilanes, and acid chlorides. The acid chloride component is incorporated into the product after decarbonylation. 

Chiral spirooxindoles. An asymmetric Heck reaction of the acryloyl 2 -iodoaniline (2) effected with tris(dibenzylideneacetone)dipalladium and (R)-l as the chiral ligand can provide either enantiomer of the spiroindole 3 depending upon an added promotor. Thus the presence of a silver salt provides (S)-(+)-3, whereas addition of a basic tertiary amine can favor formation of (R)-(-)-3. The most effective amine is 1,2,2,6,6-pentamethylpiperidine (PMP). 

For additional discussion about palladium-catalyzed coupling reactions, see also those entries dealing with organopalladium catalysis (e.g. tetrakis(triphenylphosphine)palladium(0), tris-(dibenzylideneacetone)dipalladium-chloroform, and ( )-l-tri-methylsilyl-2-trimethylstannylethylene. 

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