Design and Synthesis of Novel Chiral Dirhodium(II) Carboxylate Complexes for Asymmetric Cyclopropanation Reactions

Frady G Adly; Michael G Gardiner; Ashraf Ghanem

doi:10.1002/chem.201504817

Design and Synthesis of Novel Chiral Dirhodium(II) Carboxylate Complexes for Asymmetric Cyclopropanation Reactions

Chemistry. 2016 Mar 1;22(10):3447-3461. doi: 10.1002/chem.201504817. Epub 2016 Feb 2.

Authors

Frady G Adly¹, Michael G Gardiner², Ashraf Ghanem³

Affiliations

¹ University of Canberra, ACT, 2601, Australia.
² School of Physical Sciences, Chemistry, University of Tasmania, Hobart, TAS, 7001, Australia.
³ Biomedical science department, University of Canberra, ACT, 2601, Australia. ashraf.ghanem@canberra.edu.au.

PMID: 26833989
DOI: 10.1002/chem.201504817

Abstract

A novel approach to the design of dirhodium(II) tetracarboxylates derived from (S)-amino acid ligands is reported. The approach is founded on tailoring the steric influences of the overall catalyst structure by reducing the local symmetry of the ligand's N-heterocyclic tether. The application of the new approach has led to the uncovering of [Rh₂ (S-^tert PTTL)₄ ] as a new member of the dirhodium(II) family with extraordinary selectivity in cyclopropanation reactions. The stereoselectivity of [Rh₂ (S-^tert PTTL)₄ ] was found to be comparable to that of [Rh₂ (S-PTAD)₄ ] (up to >99 % ee), with the extra benefit of being more synthetically accessible. Correlations based on X-ray structures to justify the observed enantioinduction are also discussed.

Keywords: asymmetric synthesis; carbenoids; chiral catalysis; cyclopropanation; rhodium.