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

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

Isothiocyanates (ITCs) are typically prepared using amines and highly toxic reagents such as thiophosgene, its derivatives, or CS 2 . In this work, an investigation of a multicomponent reaction (MCR) using isocyanides, elemental sulfur and amines revealed that isocyanides can be converted to isothio...

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Bibliographic Details
Published in:RSC advances Vol. 11; no. 5; pp. 3134 - 3142
Main Authors: Nickisch, R, Conen, P, Gabrielsen, S. M, Meier, M. A. R
Format: Journal Article
Language:English
Published: England Royal Society of Chemistry 14-01-2021
The Royal Society of Chemistry
Subjects:
Amines
Butyrolactone
Catalytic converters
Chemical synthesis
Chemistry
Column chromatography
Reagents
Sulfur
Sulfurization
Sustainability
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Summary:Isothiocyanates (ITCs) are typically prepared using amines and highly toxic reagents such as thiophosgene, its derivatives, or CS 2 . 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%). Isothiocyanates were snythesized in a more sustainable manner by sulfurization of isocyanides with elemental sulfur using catalytic amounts of DBU (down to 2 mol%).
Bibliography:10.1039/d0ra10436a
Electronic supplementary information (ESI) available. See DOI
ISSN:2046-2069
2046-2069
DOI:10.1039/d0ra10436a