A series of structurally related -amino alcohols only differing in the steric bulk of a remote alkoxy group exhibit striking differences in kinetic behavior when used as ligands in the asymmetric diethylzinc addition to benzaldehyde (R = Trityl, much more active). A combination of NMR titration studies and kinetic analysis allows the quantitative decomposition of the remote substituent effect into a lower dimerization constant of the active species and a much faster ethyl addition step.
![Ligand anatomy: Probing remote substituent effects in asymmetric catalysis through NMR and kinetic analysis](https://www.iciq.org/wp-content/uploads/2014/03/Ligand-anatomy-Probing_eng_noticies_articles_2006_25.gif)