Reusable and efficient CoCl2 •6H2O/cationic 2,2′-bipyridyl system-catalyzed S-arylation of aryl halides with thiols in water under air

A CoCl2 center dot 6H(2)O/cationic 2,2'-bipyridyl system was proven to be an efficient and reusable catalyst for the coupling of aryl halides with thiols in water under aerobic conditions, leading to the formation of thioethers. Aryl iodides and bromides could couple with various thiols giving the corresponding thioethers using only a 3 mol% catalyst loading in the presence of 1 equiv KOH and 1.5 equiv Zn at 100 degrees C. For aryl chlorides, reaction at 140 degrees C and prolongation of the reaction time was performed. After reaction, the residual aqueous solution could be reused several times without any additional treatment and regeneration, making this cobalt-catalyzed S-arylation reaction greener.