A Completely Metal-Free Protocol for Oxidative Desulfitative C-N Coupling Reaction in Non-Basic Condition.

A metal free oxidative desulfitative C-N coupling reaction through activation of latent thiol group using hypervalent iodine reagent is being reported in eco-friendly solvent ethanol. Here, the thio-amide group present in 5-alkylidene-rhodanine has been utilized as latent thiol functionality and C-N coupling with amines is realized. The reaction occurs evading the use of metal catalysts, inert atmosphere, high temperature or microwave heating, and strong base which is normally required for metal catalyzed C-N coupling reaction. Pertinently, here poorly nucleophilic aromatic amines react very efficiently. Desulfitative C-N coupling involving free thiol moiety and poorly nucleophilic aromatic amines in metal free condition has never been accomplished in one step, without requiring high temperature microwave heating or strong bases. The reaction occurs at just 50 °C in few hours under ambient atmosphere. Moreover, here no H2S is released in the environment, since solid sulphur is precipitated out as side product, making this protocol environmentally friendly. Metal free condition, low temperature, use of non-toxic solvent and reagent, prevention of the release of H2S in the environment make this protocol very much environmentally friendly and highly suitable for C-N coupling in a sustainable way.