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Lecture

Asymmetric Synthesis: Allylation and Enolate Synthesis

In course

CH-335: Asymmetric synthesis and retrosynthesis

The first part of the course presents the classical methods of asymmetric synthesis. The second part of the course introduces retrosynthesis strategies based on the disconnection approach. ...

Description

This lecture covers the asymmetric synthesis of allylation and enolates, focusing on allylation reactions with boranes, such as Crotylation, Roush's allylation, and Brown's allylation. It also discusses the stéréosélective synthesis of enolates using chiral auxiliaries like Evans' auxiliary. The lecture emphasizes the importance of steric repulsions and selectivity in these reactions.

Instructors (2)

Sandrine Gerber

Sandrine Gerber studied chemistry at the "Ecole Nationale Supérieure de Chimie de Paris" in France, where she obtained a diploma of chemical engineer in 1993. The same year she obtained a DEA (Master degree) of organic chemistry at the University Pierre et Marie Curie (Paris VI, France). From 1993 to 1996 she did a PhD in organic chemistry under the supervision of Prof. Jean-Pierre Genêt at the Ecole Nationale Supérieure de Chimie de Paris. In 1996, she moved to University of Lausanne for a post-doctoral stay under the supervision of Prof. Pierre Vogel. In 1998, she was appointed Maître-Assistante at the Institute of Organic Chemistry in the University of Lausanne. In 2003, she obtained the habilitation to direct research from the University Pierre et Marie Curie (Paris VI, France). The same year, she was appointed scientific adjunct at the EPFL and senior scientist (Maître d'Enseignement et de Recherche) in 2006. In December 2014, she was promoted to titular professor. Since September 2007, Sandrine Gerber is deputy to the director of the Institute of Chemical Sciences and Engineering (ISIC). She is also member of the Board of Directors of the Swiss Chemical Society. Since 2007, Sandrine Gerber is part-time lecturer at the university of Fribourg. She was awarded the Prize Eugene Schueller in 1997, the Prize Dufour for prospective organic chemistry in 2005 and the Werner Prize 2010. She also received a special mention in recognition of exceptional quality of pedagogic competencies in the teaching of basic sciences, given by the Direction of the School of Biology and Medicine from the University of Lausanne, in 2013. In October 2018, she will receive the Prize for Excellence in Teaching from the section of Chemistry and Chemical Engineering.

Stefano Nicolai

Official source

Related concepts (27)

Chiral auxiliary

In stereochemistry, a chiral auxiliary is a stereogenic group or unit that is temporarily incorporated into an organic compound in order to control the stereochemical outcome of the synthesis. The chirality present in the auxiliary can bias the stereoselectivity of one or more subsequent reactions. The auxiliary can then be typically recovered for future use. Most biological molecules and pharmaceutical targets exist as one of two possible enantiomers; consequently, chemical syntheses of natural products and pharmaceutical agents are frequently designed to obtain the target in enantiomerically pure form.

Aldol reaction

The aldol reaction (aldol addition) is a reaction that combines two carbonyl compounds (aldehydes or ketones) to form a new β-hydroxy carbonyl compound. These products are known as aldols, from the aldehyde + alcohol, a structural motif seen in many of the products. The use of aldehyde in the name comes from its discovery history, where aldehydes were first used in the reaction and not ketones. Aldol structural units are found in many important molecules, whether naturally occurring or synthetic.

Asymmetric induction

Asymmetric induction (also enantioinduction) describes the preferential formation in a chemical reaction of one enantiomer or diastereoisomer over the other as a result of the influence of a chiral feature present in the substrate, reagent, catalyst or environment. Asymmetric induction is a key element in asymmetric synthesis. Asymmetric induction was introduced by Hermann Emil Fischer based on his work on carbohydrates. Several types of induction exist.

Enolate

In organic chemistry, enolates are organic anions derived from the deprotonation of carbonyl () compounds. Rarely isolated, they are widely used as reagents in the synthesis of organic compounds. Enolate anions are electronically related to allyl anions. The anionic charge is delocalized over the oxygen and the two carbon sites. Thus they have the character of both an alkoxide and a carbanion. Although they are often drawn as being simple salts, in fact they adopt complicated structures often featuring aggregates.

Enantioselective synthesis

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.

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