Copper Oxide Nanoparticles Supported on Graphene Oxide-Catalyzed S-Arylation: An Efficient and Ligand-Free Synthesis of Aryl Sulfides

Copper oxide nanoparticles that are supported on graphene oxide as a catalytic system have been utilized for ligand-free and solvent-free C-S cross-coupling reactions with weak bases such as triethylamine. Symmetrical/unsymmetrical aryl sulfides have been synthesized by the coupling of different aryl halides with aromatic as well as aliphatic sulfides. Surprisingly, aryl chlorides also well reacted with different types of sulfides in the presence of dimethyl sulfoxide and cesium carbonate. Besides, this catalytic system is suitable for the synthesis of phenothiazines via cascade C-S and C-N cross-coupling of ortho-dihalides and ortho-aminobenzothiazoles. In addition, this alternative approach is extremely useful for the synthesis of a variety of symmetrical diaryl sulfides by using thiourea as a sulfur source that is devoid of the foul smell of thiols. Indeed, the calculated E-factor value of our present protocol is 2.52. Furthermore, this protocol is particularly attractive as an environmentally benign and practical method for the synthesis of different aryl sulfides. Moreover, the heterogeneous catalytic system described in this process represents not only a greener approach but retains its significant activity for up to six catalytic cycles.