4′-(Methylthio)acetophenone (4-(Methylthio)acetophenone, p-(methylthio) acetophenone, 4-MTAP) is a sulphur containing organic building block. It is a key intermediate in drug synthesis. Its industrial preparation, via Friedel-Crafts acylation reaction in the presence of aluminium chloride as catalyst and acetyl chloride as acylating agent has been reported. It has been prepared by the acetylation reaction of thioanisole with acetic anhydride in the presence of solid acid catalyst.