Design and Synthesis of Modular Oxazoline Ligands for the Enantioselective Chromium-Catalyzed Addition of Allyl Bromide to Ketones
摘要:
By systematically evaluating ligand diastereomers using a modular oxazoline template, a new ligand has been identified leading to the discovery of the first example of a chromium-catalyzed enantioselective allylation of ketones using allylic bromides.
Examination of the Role of Taft-Type Steric Parameters in Asymmetric Catalysis
作者:Matthew S. Sigman、Jeremie J. Miller
DOI:10.1021/jo901698t
日期:2009.10.16
We report the use of Taft steric parameters to correlate the substituent size of a ligand with the enantiomeric ratio of a reaction. Linear free energy relationships can be constructed by plotting the log of enantiomeric ratio (er) versus the steric parameters reported by Taft and modified by Charton. Successful correlations were found for aldehyde and ketone allylation under NHK conditions using modular