Two-step synthesized sulfonic acid functionalized imidazolium thiocyanate solid acid catalyst for thiocyanation of various electron rich arenes by metal-free method in water

Abstract

An eco-friendly, highly efficient, and novel sulfonic acid functionalized imidazolium thiocyanate (Imidazole-SO3H)/SCN and sulfonic acid functionalized imidazolium chloride (Imidazole-SO3H)/Cl solid acid catalyst were successfully synthesized. The structure of catalyst was characterized by various analyses such as FT-IR, 1H NMR and 13C NMR spectroscopy. The thiocyanation reaction of various electron rich arenes such as anilines, indoles, phenols, and other aromatic compounds were selected to show the catalytic performance and efficiency of the as-prepared solid acid catalyst, and excellent yields of the corresponding aryl and heteroaryl thiocyanates derivatives were obtained under metal-free and green conditions in water. In addition, one of the important features of current method is when the thiocyanation reaction is carried out with (Imidazole-SO3H)/SCN, this reagent has a dual role in the reaction, both as thiocyanation agent and as acidic group. On the other hand, (Imidazole-SO3H)/Cl as a catalyst plays just as acidic group in reaction. The current procedure offers advantages such as metal-free and green conditions, simple procedure, the use of a commercially available reagent, simple reaction work-up, ease of separation using simple filtration, and suitable performance in the reusability of the catalyst.