Palladium-complex-catalyzed cyanation of allylic carbonates and acetates using trimethylsilyl cyanide

Allylic carbonates are cyanated in high yields to beta,gamma-unsaturated carbonitriles using trimethylsilyl cyanide in the presence of a catalytic amount (5 mol %) of Pd(PPh3)(4) in THF under reflux. In the reaction, cinnnamyl methyl carbonate affords cinnamyl cyanide in 98% yield.; Allylic acetates also provide the corresponding carbonitriles, but often in lower yields. The cyanations of several cis- and trans-alicyclic substrates proceed cleanly (stereoselectivity > 99%) with overall retention. Characterization and reaction of palladium complexes relevant to the present catalysis indicate that transmetalation-of an eta(3)-allyl palladium complex with trimethylsilyl cyanide is facile, while the resulting cyano(eta(3)-allyl)palladium complexes afford the corresponding allylic cyanides only when excess trimethylsilyl cyanide is present. Stereochemistry of the product indicates that the CN attacks the eta(3)-allyl moieties from the palladium side.