How is Sodium 4-[(E)-{4-[(E)-(2-hydroxy-1-naphthyl)diazenyl]phenyl}diazenyl]benzenesulfonate (CAS: 6406-56-0) typically synthesized?

Sodium 4-[(E)-{4-[(E)-(2-hydroxy-1-naphthyl)diazenyl]phenyl}diazenyl]benzenesulfonate (CAS: 6406-56-0) is synthesized through a multi-step process involving diazotization, coupling reactions, and sulfonation. Commonly, the diazotized precursor is reacted with the naphthol derivative to form the diazenium ion intermediate, which is then coupled with the phenyl derivative. The sulfonation step is performed under mild conditions to ensure the desired product with high yield and selectivity.