PhI(OAc)₂-mediated dialkoxylation of 4-aminostyrenes through a dearomatization process under metal-free conditions

A novel PhI(OAc)₂-mediated dialkoxylation of 4-aminostyrenes has been developed. A range of 2,3-disubstituted 1,4-dioxane or 1,2-dimethoxyethane derivatives were formed in 15 to 95% yields with high diastereoselectivities. This transformation was distinct from the previously reported hypervalent iodine(III)-mediated dioxygenation reaction, a process via the formation of a cyclic iodonium ion intermediate. This protocol involves an oxidative dearomatization-induced nucleophilic attack and an aromatization-induced 1,6-conjugated addition.