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Asymmetric Synthesis

Oxazolidinone Chiral Auxiliaries

  • High Diastereoselectivity
  • Crystalline Products
  • High Organic Solubility
  • Mild Hydrolysis
  • Higher Temperature Acylation
  • Easier to Recycle

Products                  Reaction Schemes

Oxazolidinone chiral auxiliaries are often used for diastereoselective Michael additions, alkylations, aldol condensations, cyclopropanations, Diels-Alder, and other reactions. These new offerings combine the expected selectivity of this class of auxiliary with increased ease of handling and scalability.

The two ring phenyl groups impart a number of advantages to these Evans type reagents.1 The crystalline auxiliaries2,5 have high organic solubility3 and, the carbonyl group is more resistant to attack, allowing for example, the N- atom to be acylated at more convenient temperatures (0 0C vs -78 0C).4 Hydrolysis (i.e. removal of the auxiliary) can be carried out under mild conditions (NaOH, 20 0C, 2.5hr),5 and recycling is achieved by simple filtration and washing.5


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References

  1. Evans, D.A.et al., J. Amer. Chem. Soc., 1981, 103, 2127. (For a review of the preparation, applications and recycling of oxazolidinones, See Ager, D.J. et al. Chem Rev. 1996, 96, 835.
  2. For example 55,112-0 has mp. ca. 250 0C.
  3. Partition coefficients in H2O:EtOAc for 55,112-0 and the corresponding 5-unsubstituted-4-iPr oxazolidinone are zero and 0.8 respectively. That is, 55,112-0 is insoluble in H2O whereas the 5-unsubstituted analog is more soluble in H2O than in EtOAc (Onyx Results).
  4. Ho, G.-J.; Mathre, D.J., J.Org. Chem., 1995, 60, 2271.
  5. Hintermann, T.; Seebach, D. Helv. Chim. Acta., 1998, 81,2093.