C-H bond activated arylation of carbon-heteroatom multiple-bonds

• Applicant: Dr. Michael Tauchert
• Subject Area: Organic Molecular Chemistry - Synthesis and Characterisation
• Term: from 2009 to 2012
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 158373529

While in the area of C-H bond functionalization the arylation of alkenes and alkynes has been well explored, analogous additions across C-X multiple bonds are still very rare. In preliminary investigations a proof-of-concept for the arylation of imines using a Rh(III) catalyst has been developed. This transformation yielded alpha-branched amines with complete atom economy, avoiding the necessity to generate a stoichiometric nucleophile like a Grignard-reagent. While the reaction showed a wide tolerance towards other functional groups it is currently limited to 2-phenylpyridine as a substrate. Future investigations will aim to introduce other synthetically more useful directing groups than this 2-pyridine moiety such as benzaldimines. These are well-known, as is 2-phenylpyridine, for their ability to cyclometallate via C-H bond activation and offer an easy way for electronic fine-tuning at the imine moiety. An imine group would also provide a convenient possibility introduce chirality into the system. These studies will be based on mechanistic investigations of this new reaction, which will provide detailed information upon the specific requirements for such a directing group. Preliminary experiments suggest that the reaction proceeds via the formation of a cationic rhodacycle. Isolation of this catalytically active intermediate offers the prospect to study reactivity of this intermediate towards C-X multiple bonds on a stoichiometric level allowing to identify potentially interesting substrates. Lastly other known metallocycle will be investigated upon their ability to insert imines across their M-C bond. In particular ruthenacycles will be in the focus of interest which are known catalysts in a series for C-C bond formation reactions by C-H bond activation.

• DFG Programme: Research Fellowships
• International Connection: USA
• Hosts: Professor Robert G. Bergman; Professor Jonathan A. Ellman