Process Development for ABT-472, a Benzimidazole PARP Inhibitor

A nine-step convergent process was developed for the synthesis of ABT-472, a benzimidazole PARP inhibitor. The identity and origin of several impurities were determined, and the process was modified to reduce or eliminate these impurities. A number of safety and control issues were investigated. The original synthesis was shortened to 9 steps and streamlined while maintaining a convergent strategy. A stable salt was selected, and control of the API solid form was established. The process was successfully scaled up to provide 8.5 kg of final product of >99% purity in 33% yield over 9 steps.