In 2019, almost 80 million tons of elemental sulfur were produced as waste product in the petroleum industry. Storing these enormous amounts poses several issues, also due to safety reasons. Thus, the use of elemental sulfur is highly desired from an economic as well as environmental point of view.<br/>Isothiocyanates (ITCs) are an essential functional group in many fields, for instance thiourea synthesis or application in medicinal and biochemistry. However, ITCs are commonly synthesized by converting amines using highly toxic reagents like thiophosgene or carbon disulfide. Another approach is the sulfurization of in general less toxic isocyanides with sulfur catalyzed by toxic catalysts.<br/>Since we recently introduced a more sustainable isocyanide synthesis, we herein investigated a greener synthesis route towards ITCs by modifying a reaction between isocyanides, sulfur and amines. Thus, we were able to considerably reduce the toxicological impact of the used synthesis reagents and solvent as well as to minimize the amount of waste (E-factor) while obtaining moderate to high yields. Nevertheless, the inherent toxicity of the ITC functional group remains and thus, these compounds have to be handled with caution.

More sustainable isothiocyanate synthesis by amine catalyzed sulfurization of isocyanides with elemental sulfur

ACS Spring Meeting 2021

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