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Lecture

Asymmetric Synthesis: Concepts and Models

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 reactions not following the Felkin-Anh model, such as chelation and directed reductions using boranes. Factors favoring chelation include a strong Lewis acid with at least two free coordination sites. Directed reductions with boranes involve specific substrates and reduction by beta elimination.

Instructors (2)

Stefano Nicolai

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.

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Related concepts (20)

Lewis acids and bases

A Lewis acid (named for the American physical chemist Gilbert N. Lewis) is a chemical species that contains an empty orbital which is capable of accepting an electron pair from a Lewis base to form a Lewis adduct. A Lewis base, then, is any species that has a filled orbital containing an electron pair which is not involved in bonding but may form a dative bond with a Lewis acid to form a Lewis adduct. For example, NH3 is a Lewis base, because it can donate its lone pair of electrons.

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.

Acid

An acid is a molecule or ion capable of either donating a proton (i.e. hydrogen ion, H+), known as a Brønsted–Lowry acid, or forming a covalent bond with an electron pair, known as a Lewis acid. The first category of acids are the proton donors, or Brønsted–Lowry acids. In the special case of aqueous solutions, proton donors form the hydronium ion H3O+ and are known as Arrhenius acids. Brønsted and Lowry generalized the Arrhenius theory to include non-aqueous solvents.

Acid–base reaction

An acid–base reaction is a chemical reaction that occurs between an acid and a base. It can be used to determine pH via titration. Several theoretical frameworks provide alternative conceptions of the reaction mechanisms and their application in solving related problems; these are called the acid–base theories, for example, Brønsted–Lowry acid–base theory. Their importance becomes apparent in analyzing acid–base reactions for gaseous or liquid species, or when acid or base character may be somewhat less apparent.

Acid strength

Acid strength is the tendency of an acid, symbolised by the chemical formula HA, to dissociate into a proton, H+, and an anion, A-. The dissociation of a strong acid in solution is effectively complete, except in its most concentrated solutions. HA -> H+ + A- Examples of strong acids are hydrochloric acid (HCl), perchloric acid (HClO4), nitric acid (HNO3) and sulfuric acid (H2SO4). A weak acid is only partially dissociated, with both the undissociated acid and its dissociation products being present, in solution, in equilibrium with each other.

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