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Synthesis of Optically Active 2-Siloxycyclopropanecarboxylates by Asymmetric Catalysis, IV. – Influence of Nucleophilicity of Silyl Enol Ethers on Stereoselectivities in Asymmetric Cyclopropanation Reactions

✍ Scribed by Schumacher, Ralf ;Reißig, Hans-Ulrich

Publisher
John Wiley and Sons
Year
1997
Tongue
English
Weight
604 KB
Volume
1997
Category
Article
ISSN
0947-3440

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✦ Synopsis

Abstract

By variation of the aryl substituents of silyl enol ethers 1a–e and 1f–k, the influence of their nucleophilicity on the stereochemical outcome of cyclopropanation reactions was studied. Using the neutral Schiff‐base catalyst 2 · Cu(OAc)~2~, there was only a weak effect. On the other hand, with the cationic bisoxazoline complex 3· CuOTf a remarkable increase in the enantioselectivity was observed with more strongly electron‐attracting substituents such as a trifluoromethyl or nitro group.

📜 SIMILAR VOLUMES

Synthesis of Optically Active 2-siloxycy
Synthesis of Optically Active 2-siloxycyclopropanecarboxylates by Asymmetric Catalysis, V. Baeyer–Villiger Oxidations of γ-Oxo Esters – Determination of the Absolute Configurations of Methyl 2-Siloxycyclopropanecarboxylates – Interpretation of the Enantioselective Cyclopropanations of Silyl Enol Ethers
✍ Reißig, Hans-Ulrich ;Schumacher, Ralf ;Ferse, Dirk 📂 Article 📅 1997 🏛 John Wiley and Sons 🌐 English ⚖ 563 KB

## Abstract Racemic and enantiomerically enriched methyl 2‐siloxycyclopropanecarboxylates 1 have been ring‐opened to furnish γ‐oxo esters 2. Depending on the electronic properties of substituents, these could be transformed into either succinate derivatives 3 or 3‐oxybutanoates 4 by Baeyer‐Villiger