<i>N</i>‐Oxide‐Catalyzed Six‐Membered Ring Bromo‐etherification of ε‐Alkenyl Alcohols

Abstract A six‐membered ring bromo‐etherification of ϵ‐alkenyl alcohols using an N ‐oxide catalyst was developed to furnish 2‐bromomethyl‐6‐substituted tetrahydropyrans with cis ‐selectivity and 3‐bromomethyl isochromans in high yields. DFT calculations indicate that the NMO catalyst enhances the electrophilicity of the bromine atom on NBS via two hydrogen‐bonding interactions after the formation of the NMO‐NBS complex.