How is N,N-Bis(4-aminophenyl)-1,4-benzenediamine (CAS: 25321-14-6) typically synthesized?

N,N-Bis(4-aminophenyl)-1,4-benzenediamine is synthesized by a multi-step process involving the coupling of 4-aminophenol with 1,4-benzenediamine. The reaction is typically carried out in an aqueous medium with a catalyst such as sodium carbonate or potassium carbonate, leading to high yield and selectivity. This process requires careful temperature and pH control to ensure efficient coupling and product purity.