Solvent-dependent stereoselectivity in a Still-Wittig rearrangement: an experimental and ab initio study.
[see reaction]. The Still-Wittig rearrangement gave opposite selectivities for (Z:E)-alkenes in THF (3:1) vs toluene (1:3) in the synthesis of serine-proline dipeptide amide isosteres. Four transition states leading to (Z)-and (E)-alkenes with THF and without (representing toluene) were identified by ab initio calculations at the 3-21G* level. The calculated (Z:E)-ratios with THF (4.7:1) and without THF (1:3.2) suggested that the transition state geometries and energies were well-represented by the calculations.
Hart
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Department of Chemistry, University of Virginia, Charlottesville, Virginia 22904, USA.
Trindle
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Etzkorn
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D004151:Dipeptides / Q000138:chemical synthesis*; D012997:Solvents / Q000737:chemistry*; D013237:Stereoisomerism
D004151:Dipeptides; D012997:Solvents