· (MW 500.90)
(chiral ligand for rhodium-catalyzed enantioselective hydrogenation of dehydroamino acids and for rhodium-catalyzed enantioselective isomerization of allylic alcohols to aldehydes)
Solubility: soluble in organic solvents.
Form Supplied in: yellow oil.
Handling, Storage, and Precautions: can be handled briefly in air; should be stored under an inert atmosphere.
Rhodium-Catalyzed Enantioselective Hydrogenation of Dehydroamino acids
Under mild conditions (1 atm H2, rt), a Rh/phosphaferrocene catalyst cleanly reduces dehydroaminoacids to a-amino acids (1).1,2 The enantiomeric excess and yields are good, regardless of whether the b-substituent is H, aryl or alkyl.
Rhodium-Catalyzed Enantioselective Isomerization of Allylic Alcohols to Aldehydes
This ligand, in conjunction with [Rh(cod)2]BF4, effects the catalytic enantioselective isomerization of allylic alcohols to aldehydes (eqs 2 and 3; up to 86% ee).3,4 Z allylic alcohols typically undergo isomerization with higher ee than do E allylic alcohols. These are the best yields and enantioselectivities that have been reported to date for this process. The p-acceptor ability of the phosphaferrocene may play an important role in the unusual effectiveness of this ligand.
- 1. Qiao, S.; Fu, G. C., J. Org. Chem. 1998, 63, 4168.
- 2. Brown, J. M., In Comprehensive Asymmetric Catalysis, Jacobsen, E. N.; Pfaltz, A.; Yamamoto, H., Eds.; Springer: New York, 1999, Vol. 1: Chapter 5.1.
- 3. Tanaka, K.; Qiao, S.; Tobisu, M.; Lo, M. M. C.; Fu, G. C., J. Am. Chem. Soc. 2000, 122, 9870.
- 4. Tani, K., Pure Appl. Chem. 1985, 57, 1845.
Gregory C. Fu
Massachusetts Institute of Technology, Cambridge, MA, USA
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