Related Experiment Video
Updated: Jun 27, 2026

Efficient Construction of Drug-like Bispirocyclic Scaffolds Via Organocatalytic Cycloadditions of α-Imino γ-Lactones and Alkylidene Pyrazolones
Published on: February 7, 2019
On the racemization of chiral imidazolines
Carl A Busacca1, Teresa Bartholomeyzik, Sreedhar Cheekoori
1Department of Chemical Development, Boehringer-Ingelheim Pharmaceuticals, Inc., 900 Ridgebury Road, Ridgefield, Connecticut 06877, USA. carl.busacca@boehringer-ingelheim.com
Abstract:
Racemization of chiral imidazolines with base has been studied for the first time following an unexpected finding in the synthesis of chiral imidazoline ligands. Amine bases do not cause racemization. Strong inorganic bases can induce racemization, yet this occurs only when the nitrogen is unsubstituted, in agreement with a symmetry-allowed thermal disrotatory ring opening and closure from a diazapentadienyl anion. Surprisingly, even with electron-withdrawing N-substituents, no racemization is observed. Conditions which allow for the racemization-free manipulations of this important compound class have been defined and developed.
Related Concept Videos
Stereochemical Effects of Enolization
Racemic Mixtures and the Resolution of Enantiomers
Radical Halogenation: Stereochemistry
Halogenation to form a new chiral center:
Prochirality
SN1 Reaction: Stereochemistry
In the first step of an SN1 reaction, the bond between the electrophilic carbon and the leaving group ionizes to generate the carbocation intermediate. The second step of the mechanism is the nucleophilic attack.
In the formed carbocation, the positively charged carbon is sp2 hybridized with a trigonal planar geometry. As all the three substituents lie on the same plane, a plane of symmetry for the...
Chirality at Nitrogen, Phosphorus, and Sulfur
A consequence of chirality is the need for enantiomeric resolution. While this is theoretically possible for all...

![Solid-phase Synthesis of [4.4] Spirocyclic Oximes](/_next/image?url=https%3A%2F%2Fcloudfront.jove.com%2FCDNSource%2Fteasers%2F58508.jpg&w=3840&q=50)