A Facile Preparation of Tetrasubstituted Arylalkenes Catalyzed by <i>p</i> ‐Toluenesulfonic Acid Monohydrate ( <i>p</i> ‐TsOH⋅H ₂ O): Application in the Synthesis of the Intermediate of Tamoxifen

Abstract An efficient synthesis of tetrasubstituted arylalkenes was readily achieved by the reaction of α‐( tert ‐butyl)benzylic alcohols using p ‐toluenensulfonic acid monohydrate as a Brønsted acid. A broad range of substrates was applicable for the reaction in good yield with high regioselectivity. The key intermediate in the synthesis of tamoxifen was produced using the present method as an example, and a plausible reaction mechanism was proposed by examining the reaction intermediates.