In organic chemistry, kinetic resolution is a means of differentiating two enantiomers in a racemic mixture. In kinetic resolution, two enantiomers react with different reaction rates in a chemical reaction with a chiral catalyst or reagent, resulting in an enantioenriched sample of the less reactive enantiomer. As opposed to chiral resolution, kinetic resolution does not rely on different physical properties of diastereomeric products, but rather on the different chemical properties of the racemic starting materials. The enantiomeric excess (ee) of the unreacted starting material continually rises as more product is formed, reaching 100% just before full completion of the reaction. Kinetic resolution relies upon differences in reactivity between enantiomers or enantiomeric complexes.
Kinetic resolution can be used for the preparation of chiral molecules in organic synthesis. Kinetic resolution reactions utilizing purely synthetic reagents and catalysts are much less common than the use of enzymatic kinetic resolution in application towards organic synthesis, although a number of useful synthetic techniques have been developed in the past 30 years.
The first reported kinetic resolution was achieved by Louis Pasteur. After reacting aqueous racemic ammonium tartrate with a mold from Penicillium glaucum, he reisolated the remaining tartrate and found it was levorotatory. The chiral microorganisms present in the mold catalyzed the metabolization of (R,R)-tartrate selectively, leaving an excess of (S,S)-tartrate.
Kinetic resolution by synthetic means was first reported by Marckwald and McKenzie in 1899 in the esterification of racemic mandelic acid with optically active (−)-menthol. With an excess of the racemic acid present, they observed the formation of the ester derived from (+)-mandelic acid to be quicker than the formation of the ester from (−)-mandelic acid. The unreacted acid was observed to have a slight excess of (−)-mandelic acid, and the ester was later shown to yield (+)-mandelic acid upon saponification.
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Chiral resolution, or enantiomeric resolution, is a process in stereochemistry for the separation of racemic compounds into their enantiomers. It is an important tool in the production of optically active compounds, including drugs. Another term with the same meaning is optical resolution. The use of chiral resolution to obtain enantiomerically pure compounds has the disadvantage of necessarily discarding at least half of the starting racemic mixture. Asymmetric synthesis of one of the enantiomers is one means of avoiding this waste.
Organic synthesis is a special branch of chemical synthesis and is concerned with the intentional construction of organic compounds. Organic molecules are often more complex than inorganic compounds, and their synthesis has developed into one of the most important branches of organic chemistry. There are several main areas of research within the general area of organic synthesis: total synthesis, semisynthesis, and methodology.
Enantioselective synthesis, also called asymmetric synthesis, is a form of chemical synthesis. It is defined by IUPAC as "a chemical reaction (or reaction sequence) in which one or more new elements of chirality are formed in a substrate molecule and which produces the stereoisomeric (enantiomeric or diastereomeric) products in unequal amounts." Put more simply: it is the synthesis of a compound by a method that favors the formation of a specific enantiomer or diastereomer.
The asymmetric synthesis of fine chemicals is a research topic of growing importance for the synthesis of modern materials, drugs and agrochemicals. In this lecture, the concepts of asymmetric catalys
La première partie du cours décrit les méthodes classiques de synthèse asymétrique. La seconde partie du cours traite des stratégies de rétrosynthèse basées sur l'approche par disconnection.
This course on homogeneous catalysis provide a detailed understanding of how these catalysts work at a mechanistic level and give examples of catalyst design for important reactions (hydrogenation, ol
Covers catalytic asymmetric reactions, including activation of electrophiles, use of iodine reagents, and various catalytic reactions in organic chemistry.
Kinetically fast racemization of chiral substrates through an achiral intermediate and enantioselective functionalization of one of the enantiomeric substrates forms the basis of the dynamic kinetic resolution (DKR) of centrally chiral molecules. We report ...
A hitherto unknown class of C4-symmetric Caryl Cβ (C3, C8, C13, C18) axially chiral porphyrins has been synthesized and the application of their iridium (Ir) complexes in catalytic asymmetric C(sp3) H functionalization is documented. Cyclotetramerization o ...
2024
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Cyclic sulfones have demonstrated important applications in drug discovery. However, the catalytic and enantioselective synthesis of chiral cyclic sulfones remains challenging. Herein, we develop nickel-catalyzed regiodivergent and enantioselective hydroal ...