A synthetic approach to monofluorinated compounds starts from the Friedel-Crafts acylhalogenation of trifluoroethene to give chlorotrifluoroketones and thence trifluorovinyl ketones. These are converted to phenylthio-adducts and thence monofluorinated α, β-unsaturated phenylthioesters, which by reduction afford β-fluoroallylic alcohols.