Heck reaction tetrakis palladium

Heteroaryl halides (or phenolic triflates) take part in palladium-catalysed couplings with a wide range of organometallic and anionic reagents in contrast to the Heck reaction, the catalyst is often provided as preformed Pd(0), in a complex such as tetrakis(triphenylphosphine)palladium(0), Pd(Ph3P)4. 

The Heck reaction (Mizoroki-Heck reaction) is the reaction of an unsaturated halide (or triflate) with an alkene and a strong base and palladium catalyst to form a substituted alkene [41, 42]. The reaction is performed in the presence of an organo-palladium catalyst. The halide or triflate is an aryl, benzyl, or vinyl compound, and the alkene contains at least one proton and is often electron deficient, such as acrylate ester or an acrylonitrile. The catalyst can be tetrakis(triphenylphosphine)palladium... 

Various stilbene derivatives 315 have been synthesized via a tandem double Knoevenagel condensation/decarboxyl-ation/Heck reaction by Sinha et al. (Schane 13.69) [122]. This rather complex reaction seqnence is promoted by a catalyst system consisting of tetrakis(triphenylphosphine) palladium(O), piperidine, potassinm carbonate, and Uthinm chloride. It is conducted under miCTowave irradialion at 150 °C and provides the desired prodncts 315 in moderate to good yields. 

Heck reactions are often carried out using palladium(O) complexes. Tetrakis(triphenylphosphine)palladium(0) is frequently used, but does not allow the chemist to vary either the identity of the ligand, or the lig-andipalladium ratio. A more convenient mixture is to use the air-stable palladium(O) dibenzylideneacetone complex with the added ligands of choice. It is, however, not necessary to use a palladium(O) pre-catalyst. Palladium(II) salts, especially the more soluble palladium(II) acetate, are often used, with added phosphines. The palladium(II) salts are reduced to palladium(O) in situ. 

More recently, substituted allenyl sulfones were also engaged in Pd/Ag-catalyzed Heck-type reactions. Treated with palladium tetrakis(triphenylphosphine) and a mixture of silver and potassium carbonate in DMF at 80°C, such allenyl sulfones... 

Wilkinson s catalyst is also capable of mediating the formation of C-C bonds in reactions which apparently proceed via oxidative addition of an unsaturated organohalide across the metal (eq 48)7 or via transmetalation from an organometallic (eq 49)7 These two transformation types are very similar to couplings developed by Heck so, predictably, some palladium complexes also mediate these reactions (see Tetrakis(triphenylphosphine)palladium(0) and Palladium(II) Acetate). 

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