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Microwave synthesis of isothiocyanates from amines

Over the last 20 years, isothiocyanates (ITCs, the chemical group –N=C=S) and their precursors - the glucosinolates - have gained growing attention because of their health-promoting properties. Many vegetable foods from the order Brassicales contain glucosinolates which include cabbage, wasabi, horseradish, mustard, radish, Brussels sprouts, watercress, papaya seeds, nasturtiums, and capers. Although many synthetic methods for the preparation of ITCs have been reported to date, most of them suffer from the employment of highly toxic reagents such as thiophosgene and its analogs, the availability of non-commercialized reagents, or from a narrow substrate scope. Thus specific focus of this work was one-pot sythesis involving classical approach and microwave assisted synthesis of phenyl ITC and 4-nitrophenyl ITC. The pure ITCs were obtained by one-pot synthesis by reaction of aniline with CS2 in aqueous K2CO3 solution affording the dithiocarbamate intermediate, which was further desulfurized with cyanuric acid at 0 °C to provide the corresponding ITCs [2]. The phenyl ITC was obtained after 30 min applying different microwave conditions in comparison to classical approach which took 4 h. The reaction time for the synthesis of 4-nitrophenyl ITC was also shorthened from 72 h to 2 h using microwave conditions. The obtained compounds were confirmed by GC-MS and spectroscopic techniques (FTIR, NMR).

isothiocyanates, microwave-assisted synthesis, NMR

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