Study of synthesis of 2‐(2‐alkoxyphenyl)‐1H‐imidazoles. Comparison of oxidative aromatization reactions of imidazolines

The reaction of methyl salicylate with ethane‐1,2‐diamine has been used to prepare 2‐(2‐hydroxyphenyl)‐1H‐imidazoline. This compound was alkylated with alkyl halides to give five new 2‐(2‐alkoxyphenyl)‐1H‐imidazolines (alkyl = propyl, isopropyl, isobutyl, sec‐butyl, benzyl). Seven types of transformation reactions of imidazolines into the respective imidazoles were tested. Out of them successful were the dehydrogenation on palladium in toluene (several‐day refluxing), oxidation with activated manganese dioxide in toluene (several‐hour heating at 60 °C), and the oxidation with potassium nitrosodisulfonate (Fremy's salt) at room temperature. Seven new 2‐(2‐alkoxyphenyl)‐1H‐imidazoles were synthesized (alkyl = ethyl, propyl, isopropyl, butyl, isobutyl, sec‐butyl, benzyl) via mentioned methods. Comparison of individual oxidative aromatization reactions is discussed from the point of view of experimental arrangement, reaction time and conditions, purity of the products obtained, and yields.