Enantiomer

Summary

In chemistry, an enantiomer (/ɪˈnænti.əmər, ɛ-, -oʊ-/ ih-NAN-tee-ə-mər; from Ancient Greek ἐνάντιος (enántios) 'opposite', and μέρος (méros) 'part') – also called optical isomer, antipode, or optical antipode – is one of two stereoisomers that are non-superposable onto their own . Enantiomers are much like one's right and left hands, when looking at the same face, they cannot be superposed onto each other. No amount of reorientation in three spatial dimensions will allow the four unique groups on the chiral carbon (see chirality) to line up exactly. The number of stereoisomers a molecule has can be determined by the number of chiral carbons it has. Stereoisomers include both enantiomers and diastereomers. Diastereomers, like enantiomers, share the same molecular formula and are non-superposable onto each other; however, they are not mirror images of each other. A molecule with chirality rotates plane-polarized light. A mixture of equal amounts of each enantiomer, a racemic mixture

Official source

https://en.wikipedia.org/wiki/Enantiomer

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Development of Catalytic Asymmetric C-H Functionalizations with Chiral Cyclopentadienyl Iridium(III) Complexes

Yun-Suk Jang

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

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

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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