Desulfurization Mediated by Hypervalent Iodine(III): A Novel Strategy for the Construction of Heterocycles

The desulfurization ability of diacetoxyiodobenzene (DIB) has been explored in the preparation of isothiocyanates from the corresponding dithiocarbamate salts. The in situ generated isothiocyanates reacted with o-phenylenediamine and o-aminophenol to form monothioureas, which, on treatment with a further equivalent of DIB in one pot, gave benzimidazoles and amino benzoxazoles, respectively. Aliphatic 1,2-diamines on reaction with 2 equiv. of isothiocyanate followed by treatment with DIB gave imidazolidenecarbothioamides,whereas the treatment of aromatic 1,2-diaminebis(thioureas) yielded benzimidazoles with the concurrent formation of isothiocyanate. The driving force for the formation of the latter is the aromatization of the product. The use of DIB makes these methods simpler and more efficient, giving high yields of the desired products in one pot. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)