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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
Author(s) -
Schumacher Ralf,
Reißig HansUlrich
Publication year - 1997
Publication title -
liebigs annalen
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 0947-3440
DOI - 10.1002/jlac.199719970312
Subject(s) - cyclopropanation , chemistry , nucleophile , enol , silylation , nitro , medicinal chemistry , cationic polymerization , electrophile , catalysis , aryl , trifluoromethyl , organic chemistry , stereochemistry , alkyl
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.