Organoboranes for synthesis. 18. C2-symmetric α,α′-disubstituted-2,6-pyridinedimethanols as catalytic chiral ligands for the enantioselective nucleophilic addition of diethylzinc to aldehydes
✍ Scribed by Herbert C. Brown; Guang-Ming Chen; P. Veeraraghavan Ramachandran
- Publisher
- John Wiley and Sons
- Year
- 1997
- Tongue
- English
- Weight
- 125 KB
- Volume
- 9
- Category
- Article
- ISSN
- 0899-0042
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✦ Synopsis
Several new chiral auxiliaries with differing steric and electronic environments, such as ␣,␣Ј-dimethyl-2,6-pyridinedimethanol, ␣,␣Ј-ditrifluoromethyl-2,6pyridinedimethanol, ␣,␣Ј-dipentafluoroethyl-2,6-pyridinedimethanol, and ␣,␣Ј-diallyl-2,6pyridinedimethanol, have been examined and compared with ␣,␣Ј-di-t-butyl-2,6pyridinedimethanol for their ability to control the enantioselective addition of diethylzinc to benzaldehyde. The best chiral ligand has been tested for other representative aldehydes with varying steric and electronic requirements. The product alcohols are obtained in 21-78% ee.