The first application of C2-symmetric ferrocenyl phosphinite ligands for rhodium-catalyzed asymmetric transfer hydrogenation of various ketones

• A series of chiral C2-symmetric ferrocenyl phosphinite ligands was prepared.
• They were applied in the rhodium(I)-catalyzed asymmetric transfer hydrogenation of ketones.
• Up to 99% conversion and 99% ee were achieved with these catalytic systems.

Homogeneous catalysis has been responsible for many major recent developments in synthetic organic chemistry. The combined use of organometallic and coordination chemistry has produced a number of new and powerful synthetic methods for important classes of compounds in general and for optically active substances in particular. For this aim, a new class of chiral modular C2-symmetric ferrocenyl phosphinite ligands has been prepared in good yields by using the inexpensive 1,1′-ferrocenedicarboxyaldehyde and various ferrocene based-amino alcohols as starting materials, and applied in the rhodium(I)-catalyzed asymmetric transfer hydrogenation (ATH) of aromatic ketones to give corresponding secondary alcohols with excellent enantioselectivities and reactivities using isoPrOH as the hydrogen source (up to 99% conversion and 99% ee). The substituents on the backbone of the ligands are found to exhibit a remarkable effect on both the activity and % ee. The structures of these ligands and their complexes have been elucidated by a combination of multinuclear NMR spectroscopy, IR spectroscopy and elemental analysis.

A new class of chiral C2-symmetric ferrocenyl phosphinite ligands has been prepared by using the inexpensive 1,1′-ferrocenedicarboxyaldehyde and various ferrocene based-amino alcohols as starting materials, and applied in the rhodium(I)-catalyzed asymmetric transfer hydrogenation of ketones to give corresponding secondary alcohols using isoPrOH as the hydrogen source. Rh complexes of these ligands showed excellent enantioselectivities and reactivities in the transfer hydrogenation of ketones (up to 99% conversion and 99% ee).Figure optionsDownload as PowerPoint slide