Endo-effect-driven regioselectivity in the cyclopalladation of (S)-2-tert-butyl-4-phenyl-2-oxazoline

Relindis Y. Mawo, Sheikh Mustakim, Victor G. Young, Mark R. Hoffmann, Irina P. Smoliakova

Research output: Contribution to journalArticlepeer-review

41 Scopus citations


Direct cyclopalladation of (5)-2-ferr-butyl-4-phenyl-2-oxazoline using palladium acetate in acetic acid or acetonitrile provided a mixture of two isomeric compounds, the endo μ-AcO dimeric complex with a C(sp 3)-Pd bond and the corresponding exo derivative with a C(sp 2)-Pd bond, with the former being the major product. The μ-AcO dimeric complexes were converted to the corresponding μ-Cl analogues 3 and 4 by treatment with LiCl in acetone; the latter compounds were transformed to the corresponding PPh3 adducts 5 and 6. The NMR data suggested the puckered structure of the endo palladacycle in complexes 3 and 5, the twisted λ(S) conformation of the oxazoline ring in 3, 4, and 6, and the δ(S) conformation of the heterocycle in complex 5. The X-ray crystal structure of 5 confirmed the δ(S) conformation of the oxazoline ring in the solid state and the twisted conformation of the palladacycle and revealed a P-propeller chiral configuration of the PPh3 ligand. A series of ab initio quantum chemical calculations were performed on two model compounds generated by replacing the PPh3 ligands with NH3 in complexes 5 and 6. The structures and energies of the two model exo and endo isomers were calculated at the RHF, BLYP, and MP2 levels of theory with a 6-31G* basis for the light atoms and LANL2DZ ECP for the palladium and were found to be comparable. Single point coupled cluster calculations, with single double excitations (CCSD), corroborated the results.

Original languageEnglish (US)
Pages (from-to)1801-1810
Number of pages10
Issue number7
StatePublished - Mar 26 2007

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