Denis Sinou

Ouverture régiosélective d'époxydes par Me3SiN3 catalysée par Ti(O.iPr)4

Abstract Ti[O-iPr] 4 catalyzes the ring opening reaction of functionnalized epoxides with Me 3 SiN 3 in a highly regioselective manner.

Chiral sulphonated phosphines: II. Influence of water on the enantioselectivity in the reduction of dehydro-aminoacids☆

For the reduction of dehydro aminoacids in various media with rhodium complexes containing chiral ligands, a linear correlation of log %S/%R with the solvophobicity parameter Sp has been observed. The decrease in enantioselectivity in water is due to the high interfacial energy of this solvent.

Hydrogenation asymetrique de precurseurs d'aminoacides a l'aide de mono- et diphosphines derivees de sucres

Abstract Mono- and di-phosphines derived from sugars are synthesized and used as ligands in asymmetric catalysis. In the presence of a base (triethylamine, KOH…) the cationic complex [Rh(COD)dioxop] + ClO 4 − , catalyzes reduction of α-amino acid precursors with high optical yields (78–86%). The influence of the base is discussed.

Asymmetric water-soluble diphosphines: synthesis and use in hydrogenation as their rhodium complexes of polyoxadiphosphines

Abstract Asymmetric polyoxa-1,2- and -1,4-diphosphines have been synthesized starting respectively from (R) -isopropylidene glycerol and (2 R , 3 R )- trans -1,4-di- O -tosyl threitol; their cationic rhodium(I) complexes have been shown to be effective in catalytic asymmetric hydrogenation of prochiral substrates in ethanol and in water. Optical yields up to 75% have been observed in ethanol and 41% in water; the influence of water on the enantioselectivity is discussed.

Hydrogenation asymetrique a l'aide du complexe DIOXOP-Rh(I) voie dihydro ou voie insaturee.

Resume Temperature, pressure of hydrogen and basicity of added amine have remarkable effects on the enantioselectivity of the reduction of amino-acids precursors catalyzed by DIOXOP-Rhodium complex.

Synthesis and cytotoxic profile of glycosyl–triazole linked to 1,2,4-oxadiazole moiety at C-5 through a straight-chain carbon and oxygen atoms

The convergent synthesis of an unusual (but simple) class of compounds 5a-g has been achieved by the copper-catalyzed [3+2] cycloaddition reaction of 2,3,4,6-tetra-O-acetyl-beta-D-glucopyranosyl azide 4 with propynyl 3-[3-(aryl)-1,2,4-oxadiazol-5-yl] propionates 3a-g. The formerly known azide 4 has been prepared according to the literature procedure; however, the synthesis of esters 3a-g is being reported for the first time. The infrared as well as (1)H NMR spectra of all new products are in agreement with their proposed structures. By carrying out the nOe experiment of one of the final compounds 5a, we have been able to establish that only the 1,4-regioisomers have been formed in the cycloaddition reaction. All final products presented weak cytotoxic activity, but 5e and 5g had somewhat better behaviour showing 22-25% cell growth inhibition against two cell strains: NCI-H(292) (lung carcinoma) and HEp-2 (larynx carcinoma).

Synthese de O-Glycosides d'Alcenyles Catalysée par les Complexes du Palladium(0)

Abstract Allylic carbonates reacted with carbohydrates having a free anomeric hydroxyl group in the presence of a catalytic amount of palladium(0) giving the unsaturated O-glycosides under neutral conditions with excellent yields. In the mannofuranose and ribofuranose series, the reaction was stereospecific leading only to the α and the β anomers respectively, although a mixture of α and β anomers was obtained in the glucopyranose series.

Synthesis and application of rhodium complexes of asymmetric water-soluble diphosphine derived from 2-[(diphenylphosphino)methyl]-4-(diphenylphosphino)-pyrrolidine

Abstract Optical yields of up to 60% are obtained in the hydrogenation in water of prochiral compounds in the presence of rhodium complexes of asymmetric water-soluble diphosphines derived from 2-[(diphenylphosphino)methyl]-4-(diphenylphosphino)pyrrolidine.

Chiral sulfonated phosphines Part VI. Reduction in a two-phase system: Is water only a solvent?☆

Product separation is a very important problem in homogeneous catalytic reactions. Recently, a great deal of work has appeared on the use of twophase systems, e.g., an aqueous phase containing the catalyst and an organic phase containing the substrate [l-7]. On the other hand, reactions can be carried out using water as a solvent. Recently, the aqueous phase containing the catalyst was adsorbed onto hydrophilic metal oxides, acting as a supported aqueous phase [8]. We and others have recently described the asymmetric two-phase hydrogenation of unsaturated prochiral substrates using chiral phosphines containing sulfonate groups [ 41 or methyl quaternized amines [ 71. It was found that these ligands gave lower enantioselectivily in water than in ethanol. Recently we investigated the role of solvent changes in these systems and found a good relation between the enantioselectivity and the solvent solvophobicity. However, water probably participates in the reaction; this was recently shown in hydrogenation reaction using colloidal rhodium stabilized by polysulfonated molecules [3j] but to our knowledge there is no example of such participation in a true homogeneous system. In this letter, we show that the reduction using ethyl acetate-deuterium oxide as the two-phase system leads to a high isotope incorporation into the unsaturated substrate. For this preliminary study, hydrogenation of the methyl ester of cyacetamidocinnamic la and cu-acetamidoacrylic acids lb was carried out with hydrogen in the presence of DzO, using the in situ catalyst prepared from [Rh(COD)C112 and various mono and disulfonated phosphines 3-6. The crude reaction mixture obtained shows appreciable amount of deuterium incorporation. Mass spectrometry (chemical ionisation) indicates incorporation of only oize &n&&urn atom into compound 2 at the position a~ to the acetamido and the ester groups (m/e-222 for 2a and m/e= 146 for 2b). The

Chiral sulphonated phosphines. Part VII. Catalytic transfer-hydrogenation of unsaturated substrates with formates in the presence of water soluble complexes of rhodium☆

The development of ~ition-rne~ reagents for use in aqueous solvent systems during the last decade is mainly due to the simplification of catalyst-product separation, but also to the economy and safety of using water as a solvent. Such systems can be used in the preparation of f?ne organic chemicals and in large-scale processes such as hydrogenation [ 2-9 1, hydroformylation [ 4, 10, 111, carbonylation [ 12 f I isoprenylation f 13, 14 ] and more recently palladium coupling reaction [ 151. We were able to show that asymmetric hydrogenation of pro&ml substrates occurred in a two-phase aqueous-organic medium using a rhodium complex associated with &iral sulphonated phosphmes. Another possibility for the reduction of these substrates was the use of an aqueous solution of fox-mate as hydrogen donor in the presence of a water-soluble rh~di~ complex. High enantiosefectivities have been recently obtained in catalytic transferhydrogenation of unsaturated substrates in the presence of for-mates using rhodium catalysts associated with optically active ligands [ 41. Recently Joo and Benyei [ 9 ] showed that unsaturated aldehydes were easily and selectively reduced to the corresponding unsaturated alcohols by use of an aqueous solution of HCOONa as hydrogen donor and the water soluble complex RuCla(m-SPPh& (m-SPPh, = ~-s~phophenyl~phenylphosp~e). We report in this communication some preliminary results concerning the reduction of unsaturated substrates by an aqueous solution of for-mate in the presence of a rhodium complex associated with tppts 1 (tri-m-sulphophenylphosphine) or the tetrasulphonated cl&al CBD 2 (CBD= cyclobutanediop). The results reported in Table 1 show that the complex ~~~eod)~l~~ + 1 or 2 (cod = cycloocta-1,5-diene) is an effective catalyst precursor for the