Abstract A reaction of SH-containing heterocycles with dimethyl carbonate (DMC) in the presence of K2CO3 and tetrabutylammonium bromide (Bu4NBr) gave heteroaryl methyl thioethers in 44–93% yields. The reaction was carried out under mild conditions. This method provided a useful synthetic method for preparation of various heteroaryl methyl thioethers without the use of toxic methylic halides or dimethyl sulfate.