Aqueous microwave assisted novel synthesis of isothiocyanates by amine catalyzed thionation of isocyanides with Lawesson's reagent

A green and sustainable chemistry approach for organic synthesis is described here, which involves microwave exposure of reactants in the presence of water. A general, practical, and highly efficient protocol for the preparation of a broad range of functionalized isothiocyanates has been developed from their corresponding isocyanides using Lawesson's reagent and catalytic amount of amine bases, particularly triethylamine under microwave irradiation conditions. As opposed to established approaches that employ toxic or volatile electrophilic liquids (thiophosgene, its derivatives, or CS₂). In addition, these compounds were synthesized also by conventional heating procedures for comparison. Comparison between conventional and microwave-assisted synthesis was carried out by comparing total reaction time and percentage yield. The results suggest that microwave-assisted syntheses lead to higher yields within very short reaction times.

From isocyanides to isothiocyanates using Lawesson’s reagent in the presence of triethylamine under conventional and microwave heating conditions.