Ir-Catalysed Asymmetric Allylic Substitutions with Cyclometalated (Phosphoramidite)Ir Complexes-Resting States, Catalytically Active (π-Allyl)Ir Complexes and Computational Exploration

• Published in: Chemistry : a European journal Vol. 16; no. 22; pp. 6601 - 6615
• Main Authors: Raskatov, Jevgenij A., Spiess, Stephanie, Gnamm, Christian, Brödner, Kerstin, Rominger, Frank, Helmchen, Günter
• Format: Journal Article
• Language: English
• Published: Weinheim WILEY-VCH Verlag 11.06.2010; WILEY‐VCH Verlag; Wiley Subscription Services, Inc
• Subjects: allylic compounds; allylic substitution; asymmetric catalysis; Asymmetry; Catalysis; Catalysts; Chemistry; Crystal structure; iridium; Ligands; Mathematical analysis; Olefins; reaction mechanisms; Spectra
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/chem.200903465

Mechanistic aspects of allylic substitutions with iridium catalysts derived from phosphoramidites by cyclometalation were investigated. The determination of resting states by 31P NMR spectroscopy led to the conclusion that the cyclometalation process is reversible. A novel, one‐pot procedure for the preparation of (π‐ allyl)Ir complexes was developed, and these complexes were characterised by X‐ray crystal structure analyses and spectral data. They are fully active catalysts of the allylic substitution reaction. DFT calculations on the allyl complexes, transition states of the allylic substitution and product olefin complexes gave further mechanistic insight. A knotty problem: The mechanism of the Ir‐catalysed allylic substitution with phosphoramidites as ligands is complicated because of a reversible CH activation step. In this context, a novel, one‐pot procedure for the preparation of (π‐allyl)Ir complexes was developed (see graphic). DFT calculations on the allyl complexes, transition states of the allylic substitution and product olefin complexes were carried out.