3,3-Bis(4-methylthio)benzylpent-4-en-1-ol-d4 is labelled 3,3-Bis(4-methylthio)benzylpent-4-en-1-ol (B485945) which is used to prepare opper-catalyzed intramolecular carboetherification/C-H functionalization of aryl-containing alkenols to form fused and bridged tetrahydrofurans.