Competition between sp3 and sp2 C-H bonds in cyclopalladation of N-methyl-α-tert-butylbenzylamine

Intramolecular palladation of the (sp(3))C-H bond of a tert-butyl group of N-methyl-alpha-tert-butylbenzylamine can be achieved in competition with (sp(2))C-H bond activation where both possible reactions are equally suitable for five-membered palladacycle formation. Activation of the (sp(3))C-H bond occurs with PdCl42- assisted by a secondary amino group as a heterodonor center in a benzylamine ligand; regioselective activation of the (sp(2))C-H bond was achieved with PdI42-. To compare, cyclopalladation of the related tertiary amine occurs regioselectively to give ortho-palladated complex as the sole product. The structure of both regioisomeric complexes was confirmed by an X-ray study of their triphenylphosphine adducts. The conformational features of the two five-membered palladacycles is discussed on the base of the H-1-NMR and X-ray data. (C) 2000 Elsevier Science S.A. All rights reserved.