0000000000186631
AUTHOR
Hugo Laureano
Crystal structure of (R)-6-fluoro-2-[(S)-oxiran-2-yl]chroman
The title compound, C11H11FO2, is a building block in the synthesis of the active pharmaceutical ingredient DL-nebivolol. The synthesis starting from the enantiomerically pure (R)-6-fluoro-4-oxo-3,4-dihydro-2H-chromene-2-carboxylic acid resulted in a mixture of two stereoisomers, namely (R)-6-fluoro-2-[(S)-oxiran-2-yl]chroman and (R)-6-fluoro-2-[(R)-oxiran-2-yl]chroman. The mixture was separated by column chromatography but only one stereoisomer crystallized. The X-ray structure analysis revealed that the solid consisted of theR,Sisomer. A similar procedure was repeated for (S)-6-fluoro-4-oxo-3,4-dihydro-2H-chromene-2-carboxylic acid and, in this case, theS,Risomer was produced as a crystal…
First Dibenzophospholyl(diphenylphosphino)methane−Borane Hybrid P−(η2-BH3) Ligand: Synthesis and Rhodium(I) Complex
The first dibenzophospholyl(diphenylphosphino)methane−borane hybrid ligand has been prepared from a Pd-catalyzed reaction of (chloromethyl)diphenylphosphine−borane with the dibenzophospholyl anion. This borane precursor is readily synthesized using a promising new reaction of diphenylphosphine−borane with dichloromethane, under phase transfer catalysis (PTC) conditions. The dibenzophospholyl(diphenylphosphino)methane−borane acts as a chelating P−(η2-BH3) ligand to afford an air-stable Rh(I) complex. The X-ray crystal structure of this complex shows complexation of both benzophospholyl and borane moieties.
A triclinic polymorph of (−)-(S)-N-benzyl-2-[(R)-6-fluorochroman-2-yl]-2-hydroxyethanaminium bromide
The title salt, C18H21FNO2+·Br−, determined at 115 K, crystallizes in the triclinic space groupP1. The previously reported polymorph occurs in the monoclinic space groupP21and has two independent molecules in the asymmetric unit [Peeterset al.(1993).Acta Cryst.C49, 2157–2160]. In the title molecule, the pyran rings adopt half-chair conformations. The absolute configuration isSfor the hydroxy-bearing C atom andRfor the asymmetric C atom in the dihydropyran unit. In the crystal, the components are linked by N—H...Br and O—H...Br hydrogen bonds, forming chains along thec-axis direction. The crystal studied was refined as an inversion twin.
Enantiodivergent synthesis of P-chirogenic phosphines
International audience; Several approaches for the enantiodivergent synthesis of P-chirogenic mono- and diphosphines are described, using ephedrine methodology and phosphine borane chemistry. Firstly, both enantiomers of a tertiary phosphine can be obtained starting from the same oxazaphospholidine borane complex, prepared from (+)-ephedrine, when changing the order of addition of the organolithium reagents during the synthetic pathway. The second approach is based on the chlorophosphine boranes, which react with an organolithium reagent, to afford the corresponding phosphines with inversion of configuration. In the case where the chlorophosphine borane reacts with the t-butyl lithium reage…
Stereoselective synthesis of o-bromo (or iodo)aryl P-chirogenic phosphines based on aryne chemistry.
The efficient synthesis of chiral or achiral tertiary phosphines bearing an o-bromo (or iodo)aryl substituent is described. The key step of this synthesis is based on the reaction of a secondary phosphine borane with the 1,2-dibromo (or diiodo)arene, owing to the formation in situ of an aryne species in the presence of n-butyllithium. When P-chirogenic secondary phosphine boranes were used, the corresponding o-halogeno-arylphosphine boranes were obtained without racemization in moderate to good yields and with ee up to 99%. The stereochemistry of the reaction, with complete retention of the configuration at the P atom, has been established by X-ray structures of P-chirogenic o-halogenopheny…
Phospholylmethano P-chirogenic-phosphine-borane as P-(η2-BH3)-chelating ligands of rhodium (I): Synthesis, characterization and asymmetric hydrogenation
International audience; The stereoselective synthesis of new phospholylmethano P-chirogenic-phosphine-borane was achieved by P-C bond formation of the bridge, using electrophilic or nucleophilic P*-building blocks. These P1CH2P2*.BH3 ligands behaved as chelating (κ1-P1)-(η2-BH3) entities towards the cationic rhodium(I) centre. The resulting chiral rhodium complexes were tested in asymmetric rhodium catalyzed hydrogenation of methyl 2-(acetamido)acrylate.
Development of New Cationic Exchangers for the Recovery of Uranium (VI) from Concentrated Phosphoric Acid
The extraction of uranium (VI) from 5.3 mol.L−1 phosphoric acid with a series of phosphoric, phosphinic, dithiophosphoric, or dithiophosphinic acid derivatives (0.5 mol.L−1) in mixture with 0.125 mol.L−1 TOPO in Isane IP 185 has been investigated. In the frame of the present work, eight acidic phosphorus and thiophosphorus compounds have been synthesized: bis(1,3-diisobutoxypropan-2-yl) phosphoric acid, bis(1,3-bis-(butylthio)propan-2-yl) phosphoric acid, bis(5,8,12,15-tetraoxanonadecan-10-yl) phosphoric acid, bis(1-butoxyheptan-2-yl) phosphoric acid, bis(undecan-6-yl) phosphoric acid, bis(2-(1,3-dibutoxypropan-2-yloxy)ethyl) phosphoric acid, bis(3-butoxy-2-(butoxymethyl)-2-methylpropyl) ph…
Solvent extraction studies of uranium(VI) from phosphoric acid: Role of synergistic reagents in mixture with bis(2-ethylhexyl) phosphoric acid
Abstract The extraction of uranium(VI) from 5.3 mol·L − 1 H 3 PO 4 (a typical concentration of wet phosphoric acid) with a series of neutral organosphosphorus synergistic reagents (0.125–0.250 mol·L − 1 ) used in mixture with 0.5 mol·L − 1 bis(2-ethylhexyl) phosphoric acid (D2EHPA) in Isane IP 185 (a 100% isoparaffinic aliphatic diluent) has been investigated. The series of synergistic reagents includes tri- n -butyl phosphate (TBP), di- n -butyl n -butyl phosphonate (DBBP), n -butyl di- n -butyl phosphinate (BDBP), tri- n -butyl phosphine oxide (TBPO), tri- n -hexyl phosphine oxide (THPO), tri- n -octyl phosphine oxide (TOPO), tri- n -decyl phosphine oxide (TDPO), di- n -hexyl n -decyl pho…