Cationic [1,5]‐Aryl Migrations of Propargyl Benzyl Ethers – A Stereospecific Approach to E‐ and Z‐Tetrasubstituted Olefins

Herein we report the discovery and development of the first example of a cationic [1,5]‐aryl migration reaction, through an unprecedented phenonium ions. This reaction does not require any acid, base, transition metal‐based catalyst or promoter, instead promoted by the water activated NXS reagents. It provides a highly diastereoselective and rapid access to the medicinally and biologically important tetra‐substituted olefins (allyl alcohols). The involvement of an ipso‐carbon, as well as the 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. Synthetic application has also been demonstrated by converting two isomeric‐iodo‐olefins to respective E‐ and Z‐isomers of tamoxifen in a stereospecific manner.