Homogeneous gold catalysis
We have developed a method to create instant cationic, catalytically active, gold nuclei induced by pyridine tethered in NHC ligand carrying gold specie (AuCl3).
We have extablished a direct Au(III) catalysed route from enynamines to cyclopentadienes (Cp). Initially, we thought that isolated zwitterionic Au(III)cyclopentadiene would play a key role in the mechanistic pathway (CEJ 2010).
Recently, we have discovered that the chirality is transferred from the amine moiety to the bridgehead of Cp (JOC 2014). Theoretical and experimental studies suggest in concert that a unique dual gold push-pull transition state is involved in the alkene cis-trans isomerization step, while chirality is transferred via a helical shape transtion state with allenic character.
T. Wirtanen, M. Muuronen, M. Melchionna, M. Patzschke, J. Helaja: Gold(III)-Catalyzed Enynamine–Cyclopentadiene Cycloisomerization with Chirality Transfer: An Experimental and Theoretical Study Indicating Involvement of Dual Au(III) Push–Pull Assisted cis–trans Isomerism J. Org. Chem. 2014, 79, 10269–10283.
J .E. Perea-Buceta, T. Wirtanen, O.-V. Laukkanen, M. K. Mäkelä, M. Nieger, M. Melchionna, N. Huittinen, J. A. Lopez-Sanchez, J. Helaja: Cycloisomerization of 2-Alkynylanilines to Indoles Catalyzed by Carbon-Supported Gold Nanoparticles and Subsequent Homocoupling to 3,3’-Biindoles Angew. Chem. Int. Ed. 2013, 52, 11835-11839.
M. Muuronen, J. Perea-Buceta, M. Nieger, M. Patzschke, J. Helaja: Cationic Gold Catalysis with Pyridine-Tethered Au(III) NHC-Carbenes: An Experimental and DFT Computational Study Organometallics 2012, 31, 4320-4330.
M. Melchionna, M. Nieger, J. Helaja: Isolation of a Zwitterionic Dienegold(III) Complex Intermediate in Direct Enyne-amine to Cyclopentadiene Conversion Chemistry A European Journal 2010, 16, 8262-8267.