Copper(0) nanoparticles immobilized on SBA-15: A versatile recyclable heterogeneous catalyst for solvent and ligand free C-S coupling reaction from diverse substrates

Thioester is a vital part of several commercially available drugs. Consequently, development of suitable low cost catalyst for C-S bond formation is extremely necessary. In present work, we report a SBA-15 supported copper(0) nanoparticles based catalyst (Cu(0)MS) using wet impregnation method. The catalyst was thoroughly characterized by several techniques including powder X-ray diffraction, nitrogen adsorption-desorption, field emission scanning electron microscopy-energy dispersive X-ray (FESEM-EDX), transmission electron microscopy (TEM), high angle annular dark field scanning transmission electron microscopy (HAADF-STEM) and inductively coupled plasma-optical emission spectrometry (ICP-OES). This mesoporous silica supported copper(0) nanoparticles have been exploited as a catalyst for ligand-free and solvent-free C-S cross-coupling reactions. Symmetrical/unsymmetrical aryl/alkyl sulphides have been synthesized by the S-arylation of aromatic, heteroaromatic, and aliphatic thiols with aryl, heteroaryl as well as vinyl halides. Aryl chlorides also responded the reaction very well to produce aryl sulfides. The applicability of the current protocol has also been explored for the synthesis of the starting materials of different C-S bond containing pharmaceuticals. In addition, the present catalytic system is also suitable for the synthesis of a variety of symmetrical diaryl sulphides from aryl halides using thiourea as a sulfur source. Furthermore, it was also found that the Cu(0)MS catalyst can be reused five times without substantial loss in activity.

Automated summary

A copper(0) nanoparticles catalyst supported on mesoporous silica was developed for ligand-free and solvent-free C-S cross-coupling reactions, enabling the synthesis of various sulfides and sulfide derivatives with good reactivity towards different substrates. The catalyst was found to be reusable up to five times without significant loss in activity.