A study has been made of the reaction of chlorine and various methylthiopurines in absolute and aqueous methanol. In aqueous methanol the alkyl sulfone was isolated. In absolute methanol, replacement of the methylthio group by chlorine was observed in positions 6 and 8 of the purine nucleus. Under these conditions the methylthio group in position 2 was converted to the expected methyl sulfone. A preliminary study of the nucleophilic ...