Énantiomérie

Résumé

vignette|Les deux énantiomères du bromochlorofluorométhane. L’énantiomérie est une propriété de certaines molécules stéréoisomères, dont deux des isomères sont l'image l'un de l'autre dans un miroir plan, mais ne sont pas superposables. Une molécule ayant deux énantiomères est dite chirale. En revanche si une molécule est identique à sa propre image dans un miroir, elle est dite achirale. La chiralité peut être due :

à un centre stéréogène, comme un atome substitué asymétriquement (avec quatre substituants différents), qui est souvent un atome de carbone ;
ou à un axe de chiralité ;
ou à un plan de chiralité. Dans le cas d'un centre stéréogène, la configuration autour de ce centre est indiquée par les lettres R ou S, selon les règles de la nomenclature Cahn-Ingold-Prelog. Dans le cas d'une chiralité de type hélicoïdale, la est souvent utilisée.

Domaines d'application En chimie Chimiquement, deux énantiomères ont des réactivités identiques avec d'autres mo

Source officielle

https://fr.wikipedia.org/wiki/%C3%89nantiom%C3%A9rie

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Cp*Ir(III) catalyzed C-H functionalization is a growing field, since it provides novel complementary reactivities, but enantioselective C-H functionalization reactions with this metal remain a niche. This thesis investigates CpXIr(III) catalyzed asymmetric, ortho-directed C-H functionalization reactions. While exploring an efficient enantioselective C-H amidation process, several chiral carboxylic acids were evaluated. A pronounced matched/ mismatched phenomenon between a chiral CpXIr(III) catalyst and (S)- and (R)-phthaloyl-tert leucine was found. This phenomenon was exploited to access highly enantioenriched P-chiral compounds. The corresponding phosphines are highly promising candidates as ligands for asymmetric catalysis. The enantioselective C(sp2)-H amidation of prochiral biaryl-phosphorus(V) compounds with various sulfonyl azides furnished the corresponding P-chiral products with up to 95% yield and up to 99:1 er. The cooperative system of CpXIr(III) and (S)-phthaloyl-tert leucine catalyzes a highly enantioselective C-H arylation reaction of phosphine oxides with ortho-quinone diazides. The catalytic reaction furnished the corresponding P-chiral phosphine oxides in up to 98% yield with 98.5:1.5 er. By using 1,2 diazonaphthol derivatives for the asymmetric C-H arylation reaction of phosphine oxides, a stable chiral axis was successfully implemented, giving access to P-chiral and axially chiral diastereomeric phosphorus(V) compounds with high selectivities and yields. Purely axially chiral phosphine oxides were also provided via an atropo-enantioselective C-H functionalization with up to 96:4 er and up to 95% yield. Additionally, chiral phosphorus(V) compounds were alkylated and reduced to their corresponding chiral phosphorus(III) compounds, without erosion of optical purity.

EPFL2019

Chargement

Cooperative Effects between Chiral Cp-x-Iridium(III) Catalysts and Chiral Carboxylic Acids in Enantioselective C-H Amidations of Phosphine Oxides

Nicolai Cramer, Michael Christian Dieckmann, Yun-Suk Jang

An enantioselective C-H amidation of phosphine oxides by using an iridium(III) catalyst bearing an atropchiral cyclopentadienyl (Cp-x) ligand is reported. A very strong cooperative effect between the chiral Cp-x ligand and a phthaloyl tert-leucine enabled the transformation. Matched-mismatched cases of the different acid enantiomers are shown. The amidated P-chiral arylphosphine oxides are formed in yields of up to 95% and with excellent enantioselectivities of up to 99:1 er. Enantiospecific reduction provides access to valuable P-chiral phosphorus(III) compounds.

Wiley-Blackwell2017

Chargement

Ruthenium(II) arene PTA (RAPTA) complexes: impact of enantiomerically pure arene ligands

Shona Cammack, Catherine Marie Amélie Clavel, Paul Joseph Dyson, Kelly Joan Kilpin

Organometallic ruthenium(II) arene complexes containing the PTA ligand ([Ru(eta(6)-arene)Cl-2(PTA)], PTA = 1,3,5-triaza-7-phosphatricyclo-[3.3.1.1] decane, termed RAPTA) show pharmacologically relevant antitumour properties in vitro. Two new enantiomeric pairs of RAPTA compounds, containing the chiral arene (R)- or (S)-2-phenyl-N-(1-phenylethylene) acetamide and either dichlorido or oxalato ligands were synthesised and fully characterised. The stability of the complexes towards hydrolysis was assessed and the dichlorido complexes were found to be more stable towards hydrolysis than the prototype complex RAPTA-C, ([Ru(eta(6)-p-cymene) Cl-2(PTA)]). The cytotoxicity of the compounds towards human ovarian cancer cells is moderate to good with a degree of selectivity towards the cancer cells over healthy cells. More significantly, for the first time we were able to establish the influence of a bulky, chiral group attached to the arene on the cytotoxicity of this class of compound, with the S-enantiomer being more cytotoxic than the R-enantiomer.

Royal Society of Chemistry2013

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