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ChemInform Abstract: Aldol Addition of Lithium and Boron Enolates of 1,3-Dioxan-5-ones to Aldehydes. A New Entry into Monosaccharide Derivatives
- Source :
- ChemInform. 31
- Publication Year :
- 2000
- Publisher :
- Wiley, 2000.
-
Abstract
- Methods allowing control of stereoselectivity in aldol reactions of enolates derived from 1,3-dioxan-5-ones (4) are described. Boron enolates, generated in situ, react with benzaldehyde to give the corresponding anti aldol selectively (the anti:syn ratio of up to 96:4) and in high yield. Lithium enolates give high anti selectivity only with aldehydes branched at the α-position. Enantioselective deprotonation of CS symmetrical dioxanones (e.g., 4b) can be accomplished efficiently, with enantiomeric excess of up to 90%, with chiral lithium amide bases of general structure PhCH(Me)N(Li)R (9, 10) if the R group is sufficiently bulky (e.g, R = adamantyl) or is fluorinated (e.g., R = CH2CF3). Dioxanone boron and lithium enolates react readily with glyceraldehyde derivatives (19), yielding protected ketohexoses (20 and 21).
Details
- ISSN :
- 15222667 and 09317597
- Volume :
- 31
- Database :
- OpenAIRE
- Journal :
- ChemInform
- Accession number :
- edsair.doi...........46e9f178adb7ae09fb522dc053871090