Using amide conformation to ‘project’ the stereochemistry of an (−)-ephedrine-derived oxazolidine: a pair of pseudoenantiomeric chiral amido-phosphine ligands

Author:

Clayden Jonathan,Lai Lai Wah,Helliwell Madeleine

Publisher

Elsevier BV

Subject

Inorganic Chemistry,Organic Chemistry,Physical and Theoretical Chemistry,Catalysis

Reference12 articles.

1. Directed ortho metalation. Tertiary amide and O-carbamate directors in synthetic strategies for polysubstituted aromatics

2. Clayden, J.; Lai, L. W. Tetrahedron Lett., submitted.

3. Atropisomeric Amides as Chiral Ligands:  Using (−)-Sparteine-Directed Enantioselective Silylation to Control the Conformation of a Stereogenic Axis

4. Asymmetric Substitutions: High and Opposite Enantioselective Alkylations of a Racemic Organolithium Intermediate in the Presence of (-)-Sparteine

5. Removal of (−)-ephedrine from the amide as though it were an auxiliary (by the method of Ref. 1) was not successful: oxazolidines 5a, 5b, or 5e were hydrolysed (CF3CO2H) and reduced immediately at low temperature to alcohols, but the enantiomeric excesses obtained were only 8, 28 and 0%, respectively. Presumably, racemisation of a configurationally unstable intermediate aldehyde is responsible: atropisomeric amides with trigonal 2-substituents (2-formyl or 2-acyl, in particular) have very poor resistance to racemisation by bond rotation: see Ref. 16 and Clayden, J.; Westlund, N.; Beddoes, R. L.; Helliwell, M. J. Chem. Soc., Perkin Trans. 1 2000, 1351.

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