Novel and efficient CeCl3.7H2O/NaI-catalyzed sulfenylation of indoles and pyrroles

The preparation and manipulation of functionalized low molecular weight heteroaromatic compounds is of increasing importance for obtaining new more potent pharmaceuticals. In particular, 3-sulfenyl indoles and 2-sulfenyl pyrrole are an important class of compounds due their activity towards the treatment of several deseases, and as inhibitors in medicinal chemistry. Most of methods for their preparation are based on electrophilic aromatic sulfenylation, but a considerable number of them have been unsatisfactory because the procedures provide low yields of the desired products, and/or require harsh conditions that are incompatible with sensitive functional groups [4]. In the framework of our ongoing program in the development of Lewis acid-catalyzed reactions by CeCl3 [5], we have developed a new general and efficient methodology for the sulfenylation of indoles and pyrroles by N-(alkylthio)- and N-(arylthio)phthalimides in the presence of our combination CeCl3.7H2O/NaI.