Versatile stereocontrol in kinetic resolution of a diphenylphosphinyl-protected α-amino aldehyde by reaction with chiral phosphonates
✍ Scribed by Reinhard Kreuder; Tobias Rein; Oliver Reiser
- Book ID
- 104258415
- Publisher
- Elsevier Science
- Year
- 1997
- Tongue
- French
- Weight
- 294 KB
- Volume
- 38
- Category
- Article
- ISSN
- 0040-4039
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✦ Synopsis
In kinetic resolutions of the racemic aldehyde 1 by reaction with chiral phosphonates of type 2, all of which contain the same chiral auxiliary in the same enantiomeric form, any of the four diastereomers 3a, 3b, 4a or 4b can be obtained as the main product by an appropriate choice of reaction parameters (geometric selectivities from 66:34 to 98:2, diastereomer ratios between 93:7 and _>99:1). The switch in stereoselectivity observed when KHMDS or NaHMDS is used as base instead of KHMDS/18-crown-6 is rationalized as resulting from a change in influence of the aldehyde txstereocenter from Felkin-Anh-Eisenstein to chelation control.