41 research outputs found
Enantioselective Insertion of Carbenoids into N-H Bonds Catalyzed by Chiral Bicyclo Bisoxazoline Copper(I) Complexes
International audienceChiral copper(I)-bicyclobisoxazoline complexes were found to catalyse the insertion of α-diazocarbonyl compounds into N-H bonds of aniline derivatives. The insertion reactions proceeded with high yields (78-99%) and enantioselectivities of up to 81% for the different α-diazopropionates. A predominant effect of the nature and the position of the substituents on the enantiocontrol of the reaction was observe
Asymmetric copper-catalyzed Diels-Alder reaction revisited: control of the structure of bis(oxazoline) ligands
International audienceSynthesis of 1,4-bis(oxazoline) ligands bearing a bicyclo[2,2,2]backbone derived from 9,10-dihydro-9,10-ethanoanthacene trans-dicarboxylic acid was revisited. Starting from L- or D-amino alcohols and either (S,S) or (R,R)-dihydroethano trans-dicarboxylic acid, a complete series of ligands was evaluated in the copper-catalyzed Diels-Alder reaction. The most efficient ligands with a phenyl substituent on the oxazoline ring afforded enantiomeric excess up to 98%. This is different from previous results indicating that the best enantioselectivity involved a diastereomeric ligand with the meso-backbone
Metal-catalyzed asymmetric sulfoxidation, epoxidation and hydroxylation by hydrogen peroxide
International audienceThe development of environmentally benign reactions is an important goal in synthetic organic chemistry and chemical engineering. However, catalytic enantioselective oxidations using transition-metal complexes are limited when the oxidant is hydrogen peroxide. The two main difficulties of using hydrogen peroxide in the presence of transition metal complexes are the homolytic cleavage generating OH radicals and the catalase reaction with formation of dioxygen. The current applications of asymmetric sulfoxidation, epoxidation, dihydroxylation of alkenes and hydroxylation will be herein reported. Use of non-heme systems will be presented. The possibility of asymmetric oxidation catalyzed by metalloporphyrins will also be discussed
Nitration of Halterman porphyrin: a new route for fine tuning chiral iron and manganese porphyrins with application in epoxidation and hydroxylation reactions using hydrogen peroxide as oxidant
International audienceA methodology is reported for the regioselective nitration of the phenyl groups of Halterman porphyrin, using NaNO2. These nitro-porphyrins can be reduced to aminoporphyrins and then N-dimethylated to give new optically active porphyrins. Applications to the asymmetric epoxidation of styrene derivatives by H2O2 to give optically active epoxides (ee up to 60%) and hydroxylation of alkanes to give optically active secondary alcohols (ee up to 69%) were carried out in organic solvents (dichloromethane/methanol) using chiral iron and manganese porphyrins as catalysts
Diazo ester insertion in N-H bonds of amino acid derivatives and insulin catalyzed by water-soluble iron and ruthenium porphyrin complexes (FeTSPPCl) as application of carbenoid transfer in aqueous media
International audienceThe metal complex FeTSPPCl (5,10,15,20-tetrakis)-(4-sulfonato-phenyl)-porphyrin-iron(III) chloride is an active catalyst for carbenoid insertion in N–H bonds of aminoacid derivatives in aqueous media. A variety of diazoacetates and methyl diazophosphonate were used as carbenoid precursors. The commercially available iron porphyrin complex can also selectively catalyze alkylation of the N-terminus of insulin (chain B
Stable N-heterocyclic carbene (NHC)-palladium(0) complexes as active catalysts for olefin cyclopropanation reactions with ethyl diazoacetate
The Pd(0) complexes
NHCPdLn (NHC = N-heterocyclic
carbene ligand; L = styrene for n = 2 or
PR3 for n = 1) efficiently catalyze the
olefin cyclopropanation using ethyl
diazoacetate (EDA) as the carbene
source with activities that improve any
other previous described catalytic
system based on this metal.
Mechanistic studies have shown that all
those catalyst precursors deliver in
solution the same catalytic species
(IPr)Pd(sty), a 14e, unsaturated
intermediate that further reacts with
EDA to afford (IPr)Pd(=CHCO2Et)(sty),
from which cyclopropane is formed.We thank Prof. P. J. PĂ©rez (Univ. Huelva) for helpful and constructive comments on these studies. We thank the Ministerio de Ciencia e InnovaciĂłn (grants CTQ2008–00042BQU and CTQ2011–24502) and the Junta de AndalucĂa (Proyecto P07-FQM-02794) for financial support. CM thanks the MEC for a research fellowshipWe thank Prof. P.J. Perez (Univ. Huelva) for helpful and constructive comments on these studies. We thank the Ministerio de Ciencia e Innovacion (grants CTQ2008-00042BQU and CTQ2011-24502) and the Junta de Andalucia (Proyecto P07-FQM-02794) for financial support. CM thanks the MEC for a research fellowship
First enantioselective iron-porphyrin-catalyzed sulfide oxidation with aqueous hydrogen peroxide.
International audienceThe asymmetric oxidation of sulfides by H(2)O(2) to give optically active sulfoxides (ee up to 90%) was carried out in methanol and water using chiral water-soluble iron porphyrins as catalysts
Intermolecular asymmetric cyclopropanation with diazoketones catalyzed by chiral ruthenium porphyrins.
International audienc
Synthesis of chiral water-soluble metalloporphyrins (Fe, Ru): new catalysts for asymmetric carbene transfer in water
International audienc
Porphyrin symmetry and chiral catalysis in water
International audienceChiral metalloporphyrins (ruthenium, iron and manganese) have been developed in solution. Both effective chiral recognition and asymmetric catalysis using optically active macrocycles were observed. Asymmetric oxidation and carbene transfer showed potential pharmaceutical applications