Development and Validation of a Kilogram-Scale Synthesis of Tirapazamine

[Image: see text] The process selection and subsequent development of a reliable, scalable synthesis of the anticancer prodrug tirapazamine (SR259075) is described in this paper. Reaction of benzofuroxan with cyanamide in acetonitrile in the presence of 1,8-diazabicyclo[5.4.0]undec-7-ene at 20–25 °C afforded, after an acidic workup, the targeted molecule in good yield at a kilogram scale. Notable critical parameters and safety enhancements are defined and successfully implemented to produce three consecutive validation batches in a reproducible manner.