Bromineless Bromine as an Efficient Desulfurizing Agent for the Preparation of Cyanamides and 2-Aminothiazoles from Dithiocarbamate Salts

In a one-pot procedure, bromineless brominating reagent 1,1′-(ethane-1,2-diyl)dipyridinium bistribromide (EDPBT) has been used as a desulfurizing agent in the preparation of organic cyanamides and substituted thiazoles starting from dithiocarbamic acid salts. In this approach, alkyl/aryl isothiocyantes were first obtained by the desulfurization of dithiocarbamic acid salts with EDPBT. The in situ–generated isothiocyanates reacts with an aqueous ammonia, forming alkyl or aryl thioureas, which on subsequent oxidative desulfurization with EDPBT led to the formation of corresponding cyanamides in good yields. Alternatively, an efficient one-pot synthesis of substituted thiazoles has been achieved by the condensation of the in situ–generated 1-aryl thioureas with the in situ–generated α-bromoketones from ketones, again using EDPBT. The reagent EDPBT can be easily prepared from the readily available reagents. Desulfurizing ability dominates over its brominating ability for substrates amenable to bromination.

Keywords: Cyanamide, desulfurizing agent, dithiocarbamate, ditribromide, thiazole

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ACKNOWLEDGMENTS

B. K. P. acknowledges support of this research from the Department of Science and Technology (DST), New Delhi (SR/S1/OC-15/2006), and the Council of Scientific and Industrial Research (CSIR), 01(2270)/08/EMR-II. R. Y. thanks the CSIR for the fellowship. Thanks are due to CIF IIT Guwahati for NMR spectra and DST Funding for Infrastructure in Science and Technology (FIST) for the X-ray diffraction facility.