Hervé Bricout

Supramolecular shuttle and protective agent: a multiple role of methylated cyclodextrins in the chemoselective hydrogenation of benzene derivatives with ruthenium nanoparticles

Efficient chemoselectivities have been obtained in the hydrogenation of benzene derivatives under biphasic liquid-liquid conditions using Ru(0) nanoparticles stabilized and controlled by the relevant choice of cavity and methylation degree of cyclodextrins.

Nickel vs. palladium catalysts for coupling reactions of allyl alcohol with soft nucleophiles: activities and deactivation processes

Abstract The performance of nickel–phosphine and palladium–phosphine catalytic systems for model coupling reactions of allyl alcohol (1) with soft nucleophiles such as diethylamine (2), some active methylene compounds (4) or 1 itself in the formation of diallylether (7) are reported. It is shown that for a number of reactions, particularly the amination of 1, nickel catalysts are much more active than comparable palladium systems. However, Ni-catalytic species are more sensitive than the corresponding Pd ones, so that catalyst poisoning prevents some reactions to go to completion. The detection of allylbenzene (8) as a by-product in the etherification and amination reactions of 1 together with a 31 P NMR study has allowed to highlight a degradation pathway involving the cleavage of a phosphorus–carbon bond in a Ni-dppb intermediate.

Recent breakthroughs in aqueous cyclodextrin-assisted supramolecular catalysis

During the past twenty years, cyclodextrins (CDs) have proven to be very effective in aqueous biphasic catalysis. They could act as molecular receptors for numerous organic substrates and favour their conversion at the aqueous/organic interface. Recently, new applications have been found for CDs in aqueous catalysis. CDs can now be defined as polyfunctional entities between the substrate-containing phase and the catalyst-containing phase. In this paper, we highlight the latest breakthroughs in the use of CDs in catalysis through several examples from the literature.

Cyclodextrins as inverse phase transfer catalysts for the biphasic catalytic hydrogenation of aldehydes: a green and easy alternative to conventional mass transfer promoters

The ruthenium-catalyzed hydrogenation of water-insoluble aldehydes in an aqueous/organic two phase system has been investigated in the presence of cosolvents or cyclodextrins. At low content, i.e. a content that enables to recover quantitatively the catalytic system without loss of metal with a cosolvent, β-cyclodextrin and its dimethylated form appear to be more efficient than cosolvents for performing the reaction. The formation of inclusion complexes between cyclodextrin and various components of the reaction medium (aldehyde, alcohol, hydrocarbon of the organic phase) is discussed on the basis of mass spectrometry, NMR and catalytic experiments.

Cyclodextrins as Mass Transfer Additives in Aqueous Organometallic Catalysis

During the past fifteen years, the use of chemically modified cyclodextrins (CDs) in aqueous organometallic catalysis has sig- nificantly contributed to enlarge the application field of biphasic processes in chemistry. In this paper, we describe how these su- pramolecular receptors became one of the most efficient solutions to solve mass transfer problems in aqueous organometallic catalysis. The scientific gaps that have been cleared to explain the exact role of the CDs in these biphasic systems are especially emphasized. In particular, the impact of supramolecular interactions between chemically modified CDs and substrates, water soluble ligands or or- ganometallic catalysts is addressed for a better understanding of the recognition processes involved in the catalytic reactions.

Bis(aminophosphine)-nickel complexes as efficient catalysts for alkylation of allylic acetates with stabilized nucleophiles

Abstract The alkylation of a variety of allylic acetates with dimethyl malonate catalysed by nickel-diphosphine complexes is reported. It is shown that in most cases bis(aminophosphine) type ligands lead to much more efficient catalysts than dppb and other usual diphosphines. The use of chiral ligands during the alkylation of 3-acetoxycyclohexene affords dimethyl cyclohex-2-enylmalonate in up to 40% ee.

Synthetic and kinetic aspects of nickel-catalysed amination of allylic alcohol derivatives

Abstract The design of efficient nickel-based catalytic systems for coupling of diethylamine ( 1 ) with esters and ether derivatives of allyl alcohol ( 2a-c ) and related allyl-substituted compounds ( 4a-e ) is reported. Special attention is paid to solvent and salt effects on catalytic activities and kinetic profiles for the formation of allylamines. The results are discussed in terms of the influence of some reaction parameters (polarity, ion exchange processes, substrate) on the rate determining step of the catalytic cycle.

Low melting mixtures based on β-cyclodextrin derivatives and N,N′-dimethylurea as solvents for sustainable catalytic processes

β-Cyclodextrin series and N,N′-dimethylurea formed low melting mixtures able to immobilize organometallic species based on sulfonated phosphanes. Hydroformylation and Tsuji–Trost reactions were efficiently performed in these new solvents which led to new recyclable catalytic systems.

Highly selective synthesis of 4-vinylcyclohexene by cyclodimerization of Butadiene catalysed by aminophosphinephosphinite and bis(aminophosphine) chiral ligands nickel complexes

Abstract The highest chemoselective synthesis of 4-vinylcyclohexene ever observed by butadiene cyclodimerization on nickel complexes has been obtained with aminophosphinephosphinite and bis(aminophosphine) chiral ligands (selectivity up to 99%).

Substrate-selective catalysis in an aqueous biphasic system with per(2,6-di-O-methyl)-β-cyclodextrin

Abstract The biphasic palladium-catalysed cleavage of water-insoluble allylic substrates in the presence of methylated cyclodextrins has been investigated with the aim of performing substrate-selective catalytic reactions. While no substrate selectivity was observed in control experiments in which acetonitrile was used as mass transfer promoter, the use of DMCyD led in some cases to high substrate selectivities. For instance, a 97:3 product ratio was observed during the cleavage of a 50:50 mixture of N-dodecyl-O-allyl urethane and N,N-dihexyl-O-allyl urethane. The whole results demonstrate that the size-fit concept which postulates the highest reactivity for the best size-matched host–guest pair is limited to predict the substrate selectivity.