Francine Agbossou

Chiral β-aminophosphine oxides as ligands for ruthenium assisted enantioselective transfer hydrogenation of ketones

Abstract Enantiopure β-aminophosphine oxide ligands have been synthesized and used in asymmetric transfer hydrogenation of ketones. Optically active alcohols are obtained in high yields and with up to 84% enantiomeric excess.

P-chiral β-aminophosphine oxides vs. β-aminophosphines as auxiliaries for ruthenium catalysed enantioselective transfer hydrogenation of arylketones

Abstract Enantiopure P-chiral β-aminophosphine oxides and the corresponding β-aminophosphines have been synthesised and used as chiral auxiliaries in ruthenium catalysed asymmetric transfer hydrogenation of arylketones producing optically active alcohols up to 80% ee. Both types of auxiliaries provide comparable induction levels but the β-aminophosphine oxide ligands induce higher catalytic activities generally. In some experiments, when changing the achiral arene ligand in the catalyst precursor, a peculiar reversal of the product configuration was observed.

New alkylarylamidophosphinephosphinites as chiral diphosphines for asymmetric hydrogenation of activated keto compounds

Abstract Syntheses of new easily accessible chiral alkylarylamidophosphinephosphinite chelating ligands are described. Their rhodium complexes [Rh(L 2 *)Cl] 2 are highly effective precursors for the catalytic asymmetric hydrogenation of functionalized ketones. Ketopantoyllactone and N-benzylphenyl glyoxamide are converted to the corresponding alcohols up to 96 and 79.6 % ee respectively.

RHODIUM(I) BIS(AMINOPHOSPHANE) COMPLEXES AS CATALYSTS FOR ASYMMETRIC HYDROGENATION OF ACTIVATED KETONES

Abstract The synthesis of new homochiral bis(aminophosphanes) (BAMP) 1–5 and their application in rhodium based asymmetric hydrogenation of dihydro-4,4-dimethyl-2,3-furandione 12 and N -benzylbenzoylformamide 14 are presented. Under mild conditions, the hydrogenations led to high enantiomeric excesses (up to 87% and 75% ee respectively for both substrates).

Enantioselective synthesis of (R)- and (S)-1-ferrocenylalkylamines. Reduction of enantiopure ferrocenylimines obtained from valinol and phenylglycinol

Abstract Reduction of ferrocenylaldimines from ferrocene-carboxaldehyde and valinol or phenylglycinol with RLi, and reduction of ferrocenylketimine from ferrocenylketone and valinol or phenylglycinol with NaBH 4 , give selectively the inverse configurations of the created stereogenic center. Cleavage of ferrocenylaminoalcohols gives the corresponding optically active ( R )- or ( S )-ferrocenylalkylamines.

Synthesis of new chiral arene ruthenium(II) aminophosphinephosphinite complexes and use in asymmetric hydrogenation of an activated keto compound

Abstract The easy access to new arene-ruthenium(II)bisphosphine complexes bearing aminophosphine phosphinite ligands is presented. The complexes were prepared in two steps from [RuX 2 (arene)] 2 under mild conditions and were found to be effective precursors for the asymmetric hydrogenation of dihydro-4,4-dimethyl-2,3-furandione giving the corresponding pantolactone with up to 42% enantiomeric excess.

New chiral aminophosphine carboxyphosphinite ligands (AMPCP). Synthesis and application in asymmetric hydrogenation and hydroformylation

Abstract The synthesis of the first three aminophosphine-carboxyphosphinite diphosphanes derived directly from α-amino acids is presented. These ligands were applied in the asymmetric hydrogenation of dihydro-2,4-dimethyl-2,3-furandione giving the corresponding pantolactone with up to 42% ee . They were also involved, in association with platinum, in the asymmetric hydroformylation of styrene giving the branched aldehyde with low ee (

Asymmetric catalytic hydrogenation of α-ketoesters using new chiral Ru(II)(AMPP) complexes

Chiral bidentate amino(amido)phosphinephosphinite ligands (AMPP) have been used to synthesise new ruthenium bismethylallyl Ru(AMPP)(CH2C(CH3)CH2) 2 and biscarboxylate Ru(AMPP)(OCOR)2 (R = CH 3 or CF3) complexes. These complexes act as efficient catalyst precursors for the homogeneous asymmetric hydrogenation of c¢-ketoesters with enantiomefic excesses up to 79%. Optically active t~-hydroxy esters represent an important class of building blocks for natural product synthesis 1. Among the many methods available for the preparation of these compounds, the asymmetric hydrogenation of t~-ketoesters catalysed by soluble chiral rhodium(I) complexes has been extensively studied in the last two decades 2. However, less is known regarding the asymmetric catalytic hydrogenation of ct- ketoesters with chiral ruthenium(II) catalysts 3. We have undertaken a study of the synthesis of ruthenium(II) complexes chelated by chiral amino(amido) phosphinephosphinite bisphosphines (AMPP) and their use in asymmetric hydrogenation of activated ketones. Thus, we previously reported that cationic (RuX(arene)(AMPP))X complexes were efficient precursors for the asymmetric catalytic hydrogenation of ketopantolactone 4. These new chiral ruthenium precursors presented very good activities with moderate enantiomeric excesses (up to 42%).

Rhodium dihydride complexes as models for the theoretical analysis of enantioselective hydrogenation reactions

Abstract A combination of molecular mechanics methods and extended Huckel calculations has been applied in order to have access to the more stable complexes expected to be involved as catalytic intermediates in the enantioselective hydrogenation of ketopantolactone (KPL) using chiral aminophosphine-phosphinite (AMPP) chlororhodium complexes. The product selectivity has been deduced from correlations between the prevailing configuration of the hydrogenated derivatives and the energetics of competing diastereomeric dihydride complexes of formula [RhCl(H) 2 (AMPP)(KPL)] with the assumption that the enantioselectivity is controlled by the relative energies of such intermediates. The calculations have been obtained from the application of sequential and exhaustive search methodologies. The procedure has been applied to complexes bearing the aminophosphine-phosphinites ( S )-Cp,Cp-ProNOP ( IV ) and ( S )-Ph,Cp-ProNOP ( V ) and bis(aminophosphanes) derived from 2-(anilinomethyl)pyrrolidine ( VI – IX ). The latter induce a reversal of configuration of the major enantiomer of the hydrogenation product when varying specific substituents at the phosphorus atoms. Computations were carried out also for complexes bearing the two enantiomers ( S )- and ( R )-Ph,Cp-isoAlaNOP. The lowest energy complexes present enantiomeric structures. A novel insight into the local reactivity of the intermediates has been gained from determining the first migrating hydride according to the superdelocalizability parameter calculated for all isomers. Thus, the configurations of pantolactone arising from the alkoxyrhodium species obtained when assuming a nucleophilic attack of one of the hydrides to the carbonyl group of the ketone has been defined and are in total agreement with the experimental data.