Palladium catalysed pronucleophile addition to unactivated carbon–carbon multiple bonds
The addition of nucleophiles to carbon–carbon multiple bonds coordinated by Pd(II) is one of the most popular processes for palladium promoted organic transformations. However, the palladium catalysed addition of pronucleophiles to carbon–carbon multiple bonds has not been investigated widely. The compounds (H–Nu) which are prone to form nucleophilic species (Nu–) on treatment with either base or transition metals are called pronucleophiles. The additions of carbon pronucleophiles (H–CR3, hydrocarbonation), nitrogen pronucleophiles (H–NR2, hydroamination), carboxyl pronucleophiles (H–OCOR, hydrocarboxylation) and sulfur pronucleophiles (H–S–, hydrosulfination) to C–C multiple bonds are catalysed by palladium complexes. The hydrocarbonation of allenes, enynes, alkynes and methylenecyclopropanes proceeds very smoothly in the presence of palladium catalysts to give the corresponding olefinic derivatives in good to high yields. The hydroamination of allenes, enynes and methylenecyclopropanes affords the corresponding allylic amines. The hydrocarboxylation of allenes gives the corresponding allylic carboxylates in high yields, and the hydrosulfination of allenes with tosylhydrazine produces the corresponding allylic tosylates.