1-(6-Nitro-3-pyridinyl)piperazine is a reagent used in the preparation of highly potent and orally bioavailable 4-Thiazol-N-(pyridin-2-yl)pyrimidin-2-amine cyclin-dependant kinases as anticancer agents. Also is an impurity of Palbociclib (P139900), an experimental drug for the treatment of breast cancer being developed by Pfizer. It is a selective inhibitor of the cyclin-dependent kinases CDK4 and CDK6.