422415 Model Based Approach to Develop a Ring-Closure Reaction with High Product Selectivity

Thursday, November 12, 2015: 9:30 AM
Ballroom B (Salt Palace Convention Center)
Marimuthu Andiappan, Adam D. McFarland and Jared Fennell, Small Molecule Design and Development, Eli Lilly and Company, Indianapolis, IN

An intramolecular nucleophilic aromatic substitution reaction promoted by strong base is a commonly used reaction to form pharmaceutically-relevant heterocycles in the industry.  In this contribution, modeling of this ring-closure reaction was used to achieve extremely high product selectivity over impurity formation by a competitive side reaction between the desired product and the strong base, potassium tert-butoxide. The elementary steps of this competitive reaction were investigated using in situ NMR techniques for raw data collection to derive a mechanistic kinetic model. Demonstration of the model findings, specifically removal of the byproduct t-butanol (t-BuOH) from the solution, resulted in reduced impurity formation.

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