Generation and synthetic uses of stable 4-[2-isopropylidene]-phenol carbocation from bisphenol A.

[reaction: see text] Stable 4-[2-isopropylidene]-phenol carbocation, IPP cation 1, was generated readily by addition of bisphenol A in concentrated sulfuric acid at ambient temperature, and the cation could be used for facile syntheses of 4-isopropenyl phenol (IPP), IPP dimers, and spiro-bisphenol derivatives.