C2-Symmetric 1,2-Diamine/Copper(II) Trifluoromethanesulfonate Complexes as Chiral Ctalysts. Asymmetric Cyclopropanations of Styrene with Diazo Esters
Styrene and diazo esters react in the presence of copper(II) trifluoromethanesulfonate (1 molpercent) and (1S,2S)-N,N'-di(mesitylmethyl)-1,2-diphenyl-1,2-ethanediamine (2-3 molpercent) to give 2-phenyl-1-cyclopropanecarboxylates in good to excellent optical yields.This reaction has been applied to the synthesis of crythanthemic acid.
Asymmetric Copper-Catalyzed Cyclopropanation of Trisubstituted and Unsymmetrical cis-1,2-Disubstituted Olefins: Modified Bis-Oxazoline Ligands
The Cu(I) complexes of new bis-oxazolines (3-7) prepared from the corresponding amino alcohols and malono-bis-imidate exhibit high enantioselectivity of up to 94 percent ee in the catalytic cyclopropanation of trisubstituted and unsymmetrical cis-1,2-disubstituted olefins.New diazoacetate reagents have also been developed giving high trans/cis ratios of up to 99:1 trans.
Lowenthal, Richard E.,Masamune, Satoru
p. 7373 - 7376
(2007/10/02)
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