(641c) Combined Experimental and Modeling Study of a Kinetic Resolution

Kinetic resolution is currently used to isolate the desired S-isomer salt of a pharmaceutical intermediate from a racemic mixture of free bases. While this process is an elegant solution to the enantiomer separation problem, it suffers from several distinct limitations. Notably, the process runs for 3 days at 50?aC in a finely-tuned mixture of solvents to optimize the solubilities of the desired S-salt vs. the undesired R-salt. While higher temperatures would improve the reaction rate and reagent solubilities, these conditions promote attack of the solvents on the starting material and product to form a series of byproducts. A detailed kinetic network for this reactive crystallization, including racemization, salt-formation, and solid formation, has been developed using a combination of experimental and modeling tools. After model validation over a range of temperatures and reagent charges, simulations have been used to perform "virtual experiments" to guide process improvements.