Cyclopalladation of Schiff bases from phenylalanine and 2-phenylglicine

The action of palladium acetate on the Schiff bases 4-ClC6H4CHN-CH(R2)COOR1 (R1=Me, Et; R2=Ph, CH2Ph), in acetic acid for 3 h at 70 °C and subsequent treatment of the reaction residues with LiCl in acetone, affords the corresponding chloro-bridged five-membered endo-metallacycles [PdCl(CN)]2, 1a, 2a. The action of palladium acetate on the Schiff bases 2,6-Cl2C6H3CHNCH(R2)COOR1 (R1=Me, Et; R2=Ph, CH2Ph), in chloroform at room temperature and subsequent treatment of the reaction residues with LiCl in acetone, affords the corresponding chloro-bridged five- or six-membered exo-metallacycles, by metallation of the amino acid moiety [PdCl(CN)]2, 3a-exo, 4a-exo. A small amount of the endo-metallacycles was also obtained, probably by oxidative addition of the ortho CCl bond of these imines to Pd(0) formed in situ. Reaction of dimers 1a–4a with PPh3 affords the mononuclear complexes [PdCl(CN)(PPh3)] 1b–4b.