Insights into the mechanism of the ruthenium-porphyrin-catalysed allylic amination of olefins by aryl azides

This paper describes the synthesis of allylic amines by aryl azides (ArN 3) catalysed by [Ru(TPP)CO] (TPP = dianion of tetraphenylporphyrin). The employment of aryl azides renders the methodology sustainable as the formation of molecular nitrogen is the only stoichiometric byproduct. The isolation of catalytic intermediates and spectroscopic and kinetic studies revealed interesting information about the reaction mechanism, which could improve its catalytic efficiency in future research. An important result is the X-ray characterisation of [Ru(TPP)(ArN) 2] [Ar = 3,5-(CF 3) 2C 6H 3], which is active in both stoichiometric and catalytic nitrene transfer reactions. The proposed involvement of carbonyl-monoimido-ruthenium porphyrin complexes in the catalytic cycle is also derived from our kinetic and experimental results. All the data indicate the coexistence of two mechanisms, where the electronic nature of the engaged aryl azide and olefin concentration determine one mechanism or the other. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.