Novel synthesis of O-allylated oxime ethers based on allylic substitution with oximes
The palladium or iridium-catalyzed O-allylic substitution of oximes provides a new method for direct preparation of the O-allylated oxime ethers from oximes.
Selective synthesis of allylated oxime ethers and nitrones based on palladium-catalyzed allylic substitution of oximes
The viability of oximes as nucleophiles in transition-metal-catalyzed allylic substitution was examined. The oxygen atom of oxime acted as a reactive nucleophile in the reaction of a π-allyl palladium complex. In the presence of Pd(PPh3)4, the allylic substitution of oximes with allylic carbonate afforded the linear O-allylated oxime ethers selectively without a base. In contrast, the palladium-catalyzed reaction with allylic acetate proceeded smoothly in the presence of K2CO3 or Et2Zn as a base. Selective formation of nitrones was achieved by using palladium(II) catalyst. In the presence of Pd(cod)Cl2, the allylic substitution of oximes with allylic acetate afforded the N-allylated nitrones under solvent-free conditions, as a result of the reaction with the nitrogen atom of oximes.
Utility of the iridium complex of the pybox ligand in regio- and enantioselective allylic substitution
(Chemical equation presented) The viability of the iridium complex of pybox as chiral catalyst in allylic substitutions and the enantioselective synthesis of branched products was studied. Among several chiral ligands evaluated, the iridium complex of pybox having a phenyl group catalyzed the reaction with high activity to form the branched amines with good enantioselectivities when hydroxylamine, amine, and aniline were employed as a nucleophile. The allylic substitution with oximes proceeded smoothly to give the branched oxime ethers with good enantioselectivities.