Efficient Preparation of Isothiocyanates From Dithiocarbamates Using Bromineless Brominating Reagent

Abstract

For the first time, the crystal structure of a ditribromide reagent 1,1′-(ethane-1,2-diyl)dipyridinium bistribromide (EDPBT) has been determined. Utilizing this thiophilic bromineless brominating agent EDPBT, highly useful synthetic intermediates (alkyl and aryl isothiocyanates) have been achieved directly from dithiocarbamates. EDPBT can be easily prepared from readily available reagents. It has been used as a thiophilic reagent, and its thiophilicity dominates over its brominating ability for substrates amenable to bromination. This is a sustainable process for the preparation of isothiocyantes because the spent reagent can be recovered, regenerated, and reused.

Keywords:

• Desulfurizing agent
• dithiocarbamate
• ditribromide
• isothiocyanate

ACKNOWLEDGMENTS

B. K. P. acknowledges support of this research from the Department of Science and Technology, New Delhi (SR/S1/OC-15/2006), and the Council of Scientific and Industrial Research (CSIR) [01(2270)/08/EMR-II]. R. Y. H. G. and S. M. thank the CSIR for fellowships. Thanks are due to CIF Indian Institute of Technology Guwahati for NMR spectra and the Department of Science and Technology, Funding for Infrastructure in Science and Technology, for the X-ray diffraction facility.

Notes

^a Reactions were monitored by TLC.

^b Confirmed by IR, ¹H NMR, and ¹³C NMR.

^c Isolated yield.

^a Reactions were monitored by TLC.

^b Confirmed by IR, ¹H NMR, and ¹³C NMR.

^c Isolated yield.