Ligand anatomy: probing remote substituent effects in asymmetric catalysis through NMR and kinetic analysis.
A series of structurally related beta-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.
Jimeno
Ciril
C
Institute of Chemical Research of Catalonia (ICIQ), Av. Països Catalans 16, 43007 Tarragona, Spain.
Vidal-Ferran
Anton
A
Pericàs
Miquel A
MA