2.2.1. Synthesis of 1-Arylazonaphthalen-2-ols (1–4)—General Procedure

The mixture of 1 mmol substituted aniline in 37% HCl (5 mL) was stirred in an ice-bath and then the solution of 1.1 mmol sodium nitrite in water (5 mL) was added slowly (the temperature was not allowed to rise above 5 °C) for the formation of diazonium salt, which was allowed to react with 1 mmol naphthalen-2-ol in 10% NaOH (15 mL) solution. The reaction mixture was stirred at 0–5 °C for 10 min and then under an ambient temperature for 30 min. The reaction progress was monitored by thin-layer chromatography (TLC) using a mixture of EtOAc and n-hexane (1:1; V/V) as a solvent. Following the disappearance of the starting materials, the reaction mixture was filtrated and washed with water. The crude solid was recrystallized from ethanol.