The Quest for Palladium-Catalysed Alkyl-Nitrogen Bond Formation

Our interest in the development of transition-metal catalysis for the realisation of vicinal diamination reactions of alkenes started about a decade ago. A number of successful transformations in this area have been developed using palladium catalysis. As a challenging aspect of major importance, the palladium-catalysed coupling of alkyl-nitrogen bonds constitutes the second step in diaminations of alkenes. We here discuss the details that led us to consider high-oxidation-state palladium catalysis as a key feature in such C-N bond-forming reactions. This work discusses both our own contributions and the ones from colleagues and combines the discussion of catalytic reactions and stoichiometric control experiments. It demonstrates that reductive alkyl-nitrogen bond formation from palladium(IV) proceeds with a low activation barrier and through a linear transition state of nucleophilic displacement.