Related Experiment Video
Updated: Sep 11, 2026

Isolating Free Carbenes, their Mixed Dimers and Organic Radicals
Published on: April 19, 2019
Photochemical deracemization of α-chiral carboxamides mediated by inter- and intramolecular hydrogen bonding
Maximilian Iglhaut1, Biki Ghosh1, Thorsten Bach1
1Technische Universität München, School of Natural Sciences, Department of Chemistry and Catalysis Research Center Lichtenbergstrasse 4 85747 Garching Germany thorsten.bach@ch.tum.de https://www.ch.nat.tum.de/en/oc1/home/.
Abstract:
Photochemical deracemization allows for the direct generation of enantiomerically pure or enriched compounds from their racemates employing a single chiral catalyst. In the present study, carboxylic acid amides (carboxamides) with a substituent in the α-position were investigated in a photochemical deracemization mediated by a chiral aromatic ketone. The catalyst displays a hydrogen bonding site which allows for a differentiation between the two enantiomers and operates by a reversible hydrogen atom transfer. It was found that α-alkoxy or α-amino substituents enable an efficient deracemization (up to 99.5 : 0.5 e.r.) due to a second intramolecular hydrogen bonding interaction locking a distinct substrate conformation.
Related Concept Videos
Regioselectivity and Stereochemistry of Acid-Catalyzed Hydration
Stereochemical Effects of Enolization
α-Halogenation of Carboxylic Acid Derivatives: Overview
Reduction of Alkenes: Asymmetric Catalytic Hydrogenation
The metal catalyst used can be either heterogeneous or homogeneous. When hydrogenation of an alkene generates a chiral center, a pair of enantiomeric products is expected to form. However, an enantiomeric excess of one of the products can be facilitated using an enantioselective reaction or an...
Acid Halides to Carboxylic Acids: Hydrolysis
As shown below, the mechanism involves a nucleophilic attack by water at the carbonyl carbon to form a tetrahedral intermediate. This is followed by the reformation of the carbon–oxygen π bond along with the departure of a halide ion. A final proton transfer step yields carboxylic acid...
Acid-Catalyzed α-Halogenation of Aldehydes and Ketones
In the first step of the mechanism, the acid protonates the carbonyl oxygen resulting in a resonance-stabilized cation, which subsequently loses an α-hydrogen to form an enol tautomer. The C=C bond in an enol is highly nucleophilic because of the electron-donating nature of the –OH group. Consequently, the double bond attacks an electrophilic halogen to form a...

