Investigations of Steric and Electronic Factors Influencing the Cyclopalladation of meta-Toluidine Analogues

Article abstract of DOI:10.1002/hlca.19920750807

The cyclopalladation of two different types of aniline derivatives is described: the acetylated anilines N-(3-methylphenyl)acetamide (2a), 3-(acetylamino)-4-chlorobenzoic acid (2c), and N-(2-chlorophenyl)acetamide (2d) are cyclometalated easily with palladium(II) acetate and trifluoroacetic acid to yield the corresponding complexes 4a, 4c, and 4d, respectively, whereas the acetylated meta-toluidine N-(2-chloro-5-methylphenyl)acetamide (2b) cannot be metalated at the only accessible site between the acetylamino and the methyl group.This aromatic C-H bond can be activated, however, with the second type of meta-toluidine derivatives: the 2-chloro-5,N-dimethyl-N-nitrosoaniline (3b) readily undergoes cyclopalladation to yield the corresponding Pd(II) complex di-μ-trifluoroacetato-bis<3-chloro-6-methyl-2-(N-methyl-N-nitrosamino)phenyl-C,N=O>dipalladium(II) (5b) containing a five-membered palladacylce with coordination of Pd(II) at the nitroso N-atom, which is established by 15N-NMR spectroscopy.