New arylselanylpyrazole-copper catalysts: Highly efficient catalytic system for C Se and C S coupling reactions

We describe herein the use of arylselanylpyrazole–copper complexes as versatile catalysts for C Se and C S coupling reactions. The performance of these complexes for C Se reactions was investigated in chalcogenoacetylene synthesis. The reactions were carried out under mild and aerobic conditions and afforded selanylalkynes bearing a variety of electron-withdrawing and electron-donating groups. The performance of these catalysts for C S coupling was investigated through the reaction of aryl halides with thiols and products were obtained in moderate to excellent yields. A plausible mechanism for selenoacetylene synthesis is also suggested, and the 77Se NMR results show that these arylselanylpyrazole ligands act as hemilabile ligands. High-resolution mass spectrometry was used to investigate the intermediates and also to corroborate the proposed catalytic cycle.