Effects of secondary interactions on the stereochemical outcome of rhodium (II) carboxylate-catalysed cyclopropanation of olefins
作者:A. Demonceau、A.F. Noels、A.J. Hubert
DOI:10.1016/s0040-4020(01)90524-1
日期:1990.1
In cyclopropanation reactions of olefins catalysed by various dirhodium(II) tetracarboxylates, it is shown that besides the well-recognized electronic and steric effets, secondary interactions between the carbenoid complex and the substrate largely determine the stereoselectivity of the cyclopropanes.
The system hexafluoroisopropanol/ethyl diazoacetate/Cu(OTf)2 is efficient for the cyclopropanation reaction. The process is experimentally simple, and efficient with various olefins in particular terminal, disubstituted double bonds.
Carboxylates as Nucleophiles in the Enantioselective Ring-Opening of Formylcyclopropanes under Iminium Ion Catalysis
作者:Estibaliz Díaz、Efraim Reyes、Uxue Uria、Luisa Carrillo、Tomas Tejero、Pedro Merino、Jose L. Vicario
DOI:10.1002/chem.201801434
日期:2018.6.21
In this work, carboxylic acids, which are typically regarded as poor nucleophiles, are demonstrated to be competent reagents to promote the ring‐opening of formylcyclopropanes after activation of the latter through iminium ion formation. Under optimized reaction conditions, a variety of γ‐acyloxy‐substituted aldehydes can be obtained in high yields and enantioselectivities through the desymmetrization