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

Abstract

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.