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Issue 5, 2021
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A more sustainable isothiocyanate synthesis by amine catalyzed sulfurization of isocyanides with elemental sulfur

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Abstract

Isothiocyanates (ITCs) are typically prepared using amines and highly toxic reagents such as thiophosgene, its derivatives, or CS2. In this work, an investigation of a multicomponent reaction (MCR) using isocyanides, elemental sulfur and amines revealed that isocyanides can be converted to isothiocyanates using sulfur and catalytic amounts of amine bases, especially DBU (down to 2 mol%). This new catalytic reaction was optimized in terms of sustainability, especially considering benign solvents such as Cyrene™ or γ-butyrolactone (GBL) under moderate heating (40 °C). Purification by column chromatography was further optimized to generate less waste by maintaining high purity of the product. Thus, E-factors as low as 0.989 were achieved and the versatility of this straightforward procedure was shown by converting 20 different isocyanides under catalytic conditions, while obtaining moderate to high yields (34–95%).

Graphical abstract: A more sustainable isothiocyanate synthesis by amine catalyzed sulfurization of isocyanides with elemental sulfur

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Supplementary files

Article information


Submitted
11 Dec 2020
Accepted
07 Jan 2021
First published
14 Jan 2021

This article is Open Access

RSC Adv., 2021,11, 3134-3142
Article type
Paper

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

R. Nickisch, P. Conen, S. M. Gabrielsen and M. A. R. Meier, RSC Adv., 2021, 11, 3134
DOI: 10.1039/D0RA10436A

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    [Original citation] - Published by The Royal Society of Chemistry.

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