Palladium extraction following metal-catalyzed reactions: recent advances and applications in the pharmaceutical industry

Palladium-catalyzed cross-coupling reactions are used extensively in the pharmaceutical industry. Therefore, the potential contamination of products with elemental impurities is an issue that any process chemist must consider in the design of a plant process. This is not only to meet regulatory limits, which is unequivocally the primary reason for metal scavenging, but also due to the high cost and limited supply of palladium, driving the need for recovery to recycle. This Review addresses the current approaches for palladium removal from organic solutions, with selected examples of their successful application in industrial-scale processes for pharmaceutical production. Palladium scavengers have been categorized based on their mode of action, i.e., adsorption, extraction/precipitation, and crystallization, to provide a summary of the current state-of-the-art in metal removal. Practical considerations when choosing metal removal methods are briefly discussed, illustrating their intrinsic advantages and drawbacks.