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

Intramolecular palladation of the (sp3)CH bond of a tert-butyl group of N-methyl-α-tert-butylbenzylamine can be achieved in competition with (sp2)CH bond activation where both possible reactions are equally suitable for five-membered palladacycle formation. Activation of the (sp3)CH bond occurs with PdCl42− assisted by a secondary amino group as a heterodonor center in a benzylamine ligand; regioselective activation of the (sp2)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 1H-NMR and X-ray data.