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Highly enantioselective conjugate additions of potassium organotrifluoroborates to enones by use of monodentate phosphoramidite ligands.

Authors
Type
Published Article
Journal
The Journal of organic chemistry
Publication Date
Volume
69
Issue
23
Pages
8045–8052
Identifiers
PMID: 15527289
Source
Medline
License
Unknown

Abstract

The use of phosphoramidite ligands in the rhodium-catalyzed asymmetric conjugate addition of potassium organotrifluoroborates to various enones in the absence of water is described. A systematic search for effective catalysts has been performed by use of high-throughput screening methods. Initially, we have screened reaction conditions, catalyst precursors, and focused ligand libraries. In the next stage we have used the monodentate ligand combination approach, and finally we have made a library of 96 different phosphoramidites by parallel synthesis in the robot (instant ligand libraries) and have tested these in the vinylation of cyclohexenone (up to 88% enantiomeric excess, ee) and 4-phenyl-3-buten-2-one (up to 42% ee). Arylation of cyclohexenone by use of potassium phenyltrifluoroborate gave 3-phenylcyclohexanone with 99% ee.

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