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Synthese optisch aktiver 2‐Siloxycyclopropancarbonsäureester durch asymmetrische Katalyse, II [1] . Einfluß der Silylenolether‐Struktur auf die enantioselektive Cyclopropanierung mit Diazoessigsäure‐methylester
Author(s) -
Dammast Franziska,
Reißig HansUlrich
Publication year - 1993
Publication title -
chemische berichte
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 0009-2940
DOI - 10.1002/cber.19931261223
Subject(s) - chemistry , cyclopropanation , enol , silylation , enantioselective synthesis , silyl enol ether , medicinal chemistry , enol ether , alkylation , ether , ketone , catalysis , alkyl , stereochemistry , organic chemistry
Synthesis of Optically Active Siloxycyclopropanes by Asymmetric Catalysis, II [1] . – Influence of the Silyl Enol Ether Structure on the Enantioselective Cyclopropanation with Methyl Diazoacetate On the basis of reactions of (Z)‐1‐phenyl‐1‐(trimethylsiloxy)‐1‐propene ( 1a ) with methyl diazoacetate ( 2 ) in the presence of different chiral (Schiff base) copper catalysts 4 ‐Cu we extended our study to the silyl enol ethers 1b–1j . The highest enantiomeric excesses were obtained in most cases with catalyst 4b ‐Cu. Whereas cyclopropanations of 1‐aryl‐ and 1‐alkenyl‐substituted silyl enol ethers 1b–1h gave moderate to good enantioselectivities (up to 80%ee), alkyl‐substituted olefins 1i and 1j provided less satisfactory results. By deprotonation and alkylation of 3c, 3h , and 3i it could be established that for these cyclopropanes the predominating absolute configuration of cis ‐ and trans ‐cyclopropanes is equal at C‐1, but consequently opposite at C‐2. The influence of the silyl enol ether structure on the enantioselectivities achieved is briefly discussed.