Active methine compounds are chlorinated by contacting such compounds with a perchloroalkane and aqueous base in the presence of a phase transfer catalyst which is a tetraalkylonium hydroxide. Chlorinated products, preferably tertiary alkyl chloro compounds, are produced. The tertiary alkyl chloro compounds are useful in elimination reactions, preferably reactions with base, to form unsaturated compounds, particularly compounds having a vinylidene or exomethylene group.