Anwendungen der Phasentransfer-Katalyse, 55. Neue Versuche zur enantioselektiven Phasentransfer-Katalyse mit optisch aktiven Kronenethern
✍ Scribed by Dehmlow, Eckehard V. ;Knufinke, Volker
- Publisher
- John Wiley and Sons
- Year
- 1992
- Tongue
- English
- Weight
- 315 KB
- Volume
- 1992
- Category
- Article
- ISSN
- 0947-3440
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✦ Synopsis
Applications of Phase‐Transfer Catalysis, 55. — New Experiments towards Enantioselective Phase‐Transfer Catalysis with Optically Active Crown Ethers
Optically active crown ethers 1a–1o,2, 3a, b, 4a, b, 5a–5d, 6a, b and the acyclic analogue 7 were used for three Michael‐type additions, benzoin condensation, a C‐alkylation, a base‐catalyzed autoxidation and a hypochlorite epoxidation. Important observations include a possible reversal of product stereochemistry when changing potassium for sodium ions and when increasing the number of side groups at the crown. Crowns with nonequivalent upper and lower faces are not useful. Additional stereogenic centers in the side chains and OH groups are not advantageous — at least in the studied cases.