Polydentate pyridyl ligands and the catalytic activity of their iron(II) complexes in oxidation reactions utilizing peroxides as the oxidants
作者:Matthew Lenze、Sergey L. Sedinkin、Eike B. Bauer
DOI:10.1016/j.molcata.2013.03.006
日期:2013.7
activity in that solvent. For the complexes [Fe(10)2](OTf)2 (two tridentate ligands), [Fe(12)(OTf)2] (one tetradentate ligand) and [Fe(16)(OTf)](OTf) (one pentadentate ligand), the product formation for a test reaction was followed over time at significantly reduced catalyst loading to determine activities. Under these conditions, the complex [Fe(10)2](OTf)2 exhibited a somewhat lower catalytic activity
An increase in enantioselectivity was observed in the asymmetric protonation of prochiral enolates with a chiral imide using lithium salt as an additive. For example, (R)-enriched 2-n-pentylcyclopentanone 6 was obtained in high yield with 90% ee when the silyl enol ether 4 was treated with n-BuLi in the presence of 5 equiv of LiBr in Et2O and the resulting lithium enolate 5 was then protonated by a solution of (S,S)-imide 1 in THF. In contrast, the product 6 obtained without LiBr exhibited a lower enantiomeric excess (74% ee)