Studies of C-C and C-N bond forming reactions via rhodium-catalyzed C-H bond activation

Abstract

Aryl amines are a key synthetic unit widely utilized in organic synthesis, coordination chemistry, materials science and in the pharmaceutical industry. Current synthetic routes to those compounds require either pre-functionalized starting materials or external oxidants, thus inevitably generating stoichiometric amounts of harmful side products. The efforts on overcoming these disadvantages in various methods. In other words, studies of C-C bond and C-N bond forming reactions via C-H activation were developed to broaden the usage of reaction in industry. Especially, C-H funtionalization using pentamethylcyclopentadienyl ligand and rhodium catalyst developed recently. Various functionalized arene derivatives could be made using this catalytic system via C-H bond activation. First, A new catalytic procedure of ortho-olefination of benzoates and benzaldehydes has been developed. Ester and carboxyaldehyde units were revealed to be effective chelating groups in focusing the activation of aryl C-H bonds ortho to the directing moieties under Rh-catalyzed oxidative conditions. The rhodium-catalyzed selective olefination is highly regioselective with a range of benzoates and benzaldehydes enabling efficient olefination with acrylates, acrylic acid, and styrenes. Second, we report herein a direct amidation reaction of arene carbon-hydrogen (C-H) bonds using sulfonyl azides as a source of the nitrogen group to release molecular nitrogen as the innocuous by-product. The reaction is catalyzed by a cationic rhodium complex without external oxidant and under atmospheric environment. A broad range of chelate group-containing arenes can be selectively amidated with excellent functional group tolerance, thereby opening up a new avenue to environmentally benign carbon-nitrogen (C-N) bond formation which can be immediately applied to various important schemes. Third, our recently reported Rh(III)-catalyzed C-N bond formation reactions where chelating group containing arene and a...