Organosilver Species as Intermediates in Catalyzed Enyne or Arylyne Synthesis

4 Organosilver Species as Intermediates in Catalyzed Enyne or Arylyne Synthesis 

Alkynylsilvers are often intermediates in various coupling reactions catalyzed by both silver and palladium salts, leading to enynes or arylynes. 

Further investigations including 109Ag NMR confirmed the in situ formation of alkynyl silver through jt complexation and proton abstraction.117 They also revealed that the best palladium catalyst, namely, palladium tetrakis(triphenylphosphine), played a key role, in that a phosphine liberated by decoordination ended up on the alkynyl silver, stabilizing it and rendering it more soluble.118 The resulting alkynyl silver then entered the palladium catalytic cycle at the transmetallation step (See section 10.6.2).105 

TABLE 10.7. Pd/Ag Coupling Reaction with Triisopropylsilylethynyl Phosphonate 

Such direct couplings of silylated alkynes have been applied to the synthesis of a variety of aryl- and heteroarylethynyl phosphonates, available only in poor yields with classical routes (Table 10.7).125 

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