Asymmetric Cyclopropanation of Olefins Catalyzed by Chiral Cobalt(II)-Binaphthyl Porphyrins

Abstract

Cobalt(II) complexes of chiral bis-binaphthyl porphyrins were prepared, and their catalytic activity in the asymmetric cyclopropanation of alkenes with ethyl diazoacetate was examined. Good yields and enantioselectivities (up to 90% ee) were observed with cis/trans ratios reaching 11:89. UV−vis and 1H NMR studies suggest that the axial nitrogen ligand N-methylimidazole could play a role in changing the enantioselectivity of the reaction.

Synthesis and characterization of copper(II), cobalt(II), nickel(II), and iron(III) complexes with two diamine Schiff bases and catalytic reactivity of a chiral diamine cobalt(II) complex

“…The maximum level of diastereoselectivity reached, however, is not very satisfactory (maximum ratio trans:cis = 74:26) if compared to the results reported some years ago by the group of Katsuki, using Co(II) Schiff bases complexes[54,55]. That is the reason why we did not try to investigate further the optimization of the catalyst loading; our[Co]/EDA ratio of 1:30 is still far from the one reported[Co]/EDA ratio of 1:200[56][57][58][59] by employing chiral Co(II)-porphyrin complexes. The catalyst showed a very low tendency to form the well-known coupling by-products (maleate and fumarate) normally obtained in cyclopropanation reactions…”

Cyclopropanation Reactions Mediated by Group 9 Metal Porphyrin Complexes

“…The observed experimental results were justified by theoretical calculations, which disclosed the existence of 19 as a pool of interconverting atropisomers. We did obtain better catalytic results by using the more rigid complexes 20, [86] 21 [87,88] and 22 [89] reported in Figure 9. Among the cobalt(II) complexes of chiral bis(binaphthyl) porphyrins reported in Figure 9, complex 21 showed the best catalytic activity.…”

“…The reaction between EDA and α-methylstyrene was studied in the presence of Co(TPP) [71] or complex 21 [89] and on the basis of spectroscopic reactions and kinetic data, we proposed the cycle shown in Scheme 12.…”

Thiosemicarbazone copper complexes as competent catalysts for olefin cyclopropanations

“…Yields were confirmed by 1 H NMR analysis of the crude and, in selected cases, products were isolated and purified by column chromatography. The collected analytical data for cis and trans ethyl-2-phenylcyclopropanecarboxylate [33], cis and trans ethyl-2-p-tolylcyclopropanecarboxylate [33], cis and trans ethyl-2-methyl-2-phenylcyclopropanecarboxylate [34], ethyl-2,2-dphenylcyclopropane carboxylate [33], cis and trans ethyl-2-(4-chlorophenyl)-2-methyl cyclopropanecarboxylate [35], cis and trans ethyl-2-naphthylcy clopropanecarboxylate [36], cis and trans ethyl-2-hexylcyclopropane carboxylate [37], cis and trans bicyclo[4.1.0]heptane-7-carboxylic acid ethyl ester [37], and cis and trans ethyl chrysantemate [37] are in agreement to those reported in the literature.…”