The organosulfur heteroaromatics have gradually gained attention as suitable electrophilic partners in C-C cross-coupling reactions, due to limited availability of the corresponding heteroaromatic halides. Since the first Liebeskind-Srogl cross-coupling of thioesters with boron derivatives, numerous coupling reactions conditions have been adapted to provide coupling products using, on one hand, various heterocyclic thioorganics, and, on the other hand, exploring the nucleophilic partner and the conditions established for most of the common cross-coupling reactions. The Sonogashira reaction has been proved as one of the most exploited synthetic approaches for alkynylation of heteroaromatic compounds in order to access complex organic molecules of great interest. However, it was less exploited in case of organosulfur heteroaromatics, the literature displaying some examples of methyl or phenyl thioethers and even less surveyed thiones.

In this context, my talk will focus on the work we performed regarding behavior of thioorganic azoles – benzazoles and oxadiazoles thiones and thioethers - in reaction with terminal alkynes, under transition metal catalysis. The optimised synthetic methodology allowed convenient cross-coupling of benzoxazole and benzothiazole methylthioethers substrates with a wide variety of aromatic and aliphatic alkynes, in moderate to good yields. In addition, mercapto-benzothiazoles were found to perform better than mercapto-benzoxazoles. Reactions of oxadiazole thiones and three types of thioethers (methyl, benzyl and phenyl) were more challenging to understand since they displayed a lower predictable reactivity pattern, including a peculiar behaviour of compounds bearing electron-donating substituents.