Herein, we report the discovery and development of the first example of a cationic [1,5]-aryl migration reaction, through an unprecedented six-membered ring fused phenonium ions (which we termed as a trihomologous-phenonium ion). This reaction does not require any acid, base, transition metal-based catalyst or promoter, instead promoted by the water activated NXS reagents. It provides highly diastereoselective and rapid access to the medicinally and biologically important tetra-substituted olefins (allyl alcohols) as well as 2-oxaspiro[5.5]undecane-9-ones. The involvement of an ipso-carbon, as well as the trihomologous-phenonium ion during this novel, cationic [1,5]-aryl migration was strongly supported by the isolation of 2-oxaspiro[5.5]undecane-9-ones. This methodology is highly tolerable for a wide range of propargyl-benzyl ethers, resulting in a selective construction of structurally divergent library of mono-halo-tricarbon-substituted alkenes as well as 2-oxaspiro[5.5]undecane-9-ones. Synthetic application has also been demonstrated by converting two isomeric-iodo-olefins to respective E- and Z-isomers of tamoxifen in a stereospecific manner.