Removal of Palladium from Organic Reaction Mixtures by Trimercaptotriazine

In an effort to remove residual palladium from a drug candidate prepared by palladium-catalyzed indolization, many treatments were examined. The most effective treatment was to precipitate palladium from solution using 2,4,6-trimercapto-s-triazine (TMT), which reduced palladium levels from 600−650 ppm to 20−60 ppm in an isolated indole intermediate. Subsequent crystallizations routinely afforded active pharmaceutical ingredient with <1 ppm of palladium. TMT treatment should prove useful to reduce the concentration of residual palladium in other reactions.