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Technology Spotlights

JoSPOphos- A New Class of Ligands for Asymmetric Hydrogenation

Despite the abundance of ligands and catalysts currently available for asymmetric hydrogenation, predicting the outcome for a given substrate is still far from trivial. The development of new alternative ligands is pursued by many academic and industrial groups seeking to improve the performance of well established systems. Pugin (Solvias) and Pfaltz (University of Basel) recently reported that chiral ferrocenes containing secondary phosphine oxides in combination with phosphines (SPO-P) showed interesting coordination behavior, serving as excellent bidentate ligands for this transformation (Scheme 1).1


Possible coordination modes and rhodium catalyzed hydrogenation

Scheme 1: Possible coordination modes and rhodium catalyzed hydrogenation of various substrates with SPO-P ligands.

Rather unusual but yet very pleasing are the enantioselectivities obtained in the hydrogenation of α- and β-dehydro amino acid derivatives and methyl itaconate. Interestingly E- and Z-EAC generate products with the same absolute configuration allowing the use of E/Z mixtures. Activities are extremely high, MAA and DMI are hydrogenated in <5 minutes using substrate/catalyst ratios of 200–1,000 at a hydrogen pressure of 1 bar, and giving turnover frequencies in the range 2,000–20,000 per hour.


Possible coordination modes and rhodium catalyzed hydrogenation

778532 | 778648 | 778974 | 778745

For a complete list of Solvias ligands and complexes available from Aldrich Chemistry, click here

References

  1. Landert, H.; Spindler, F.; Wyss, A.; Blaser, H-U.; Pugin, B.;Ribourduoille, Y.; Gschwend, B.; Ramalingam, B.; Pfaltz, A. Angew. Chem. Int. Ed. 2010, 49, 6873.