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Reetz Ligands

By: William Sommer and Daniel Weibel, Aldrich ChemFiles 2008, 8.2, 54.

Aldrich ChemFiles 2008, 8.2, 54.

In 1998, Reetz et al. reported the synthesis of a new generation of ligand for enantioselective, catalyzed hydrogenation. Based on BINOL-derived diphosphonite molecules, these ligands showed good enantioselectivities for the asymmetric hydrogenation of terminal alkenes, ketones, and β-keto esters,1,2 and the asymmetric conjugate addition of arylboronic acid derivatives to α,β-unsaturated carbonyls.3

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Enantioselective Hydrogenation of Olefins

Reetz et al. reported the hydrogenation of two different olefins with Rh(cod)BF4 and R,R-Reetz F-Diphosphonite. Outstanding yields and selectivity were reported (Scheme 1).4 Used with a RuCl2(p-cymene)2 complex, the R,R-Reetz X-Diphosphonite converts a variety of ketones into secondary alcohols with yields and ee's up to 100% and 98%, respectively (Scheme 2).1

Scheme 1

Scheme 1

Scheme 2

Scheme 2

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Materials

     

References

  1. Reetz, M. T. et al. J. Am. Chem. Soc. 2006, 128, 1044.
  2. Reetz, M. T. et al. Adv. Synth. Catal. 2006, 348, 1157.
  3. Reetz, M. T. et al. Org. Lett. 2001, 3, 4083.
  4. Reetz, M. T. et al. Chem. Commun. 1998, 2077.

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