Metal-free oxidative all-halogen–compatible halogenation of methylenecyclopropane for accessing benzoxazines

Abstract

Electrophilic halogenation is a pivotal transformation in organic synthesis, enabling molecular functionalizations that can modulate biological activity. Herein, we report a metal-free oxidative protocol that is compatible with all four major halogens (F, Cl, Br, I) using Selectfluor as a key reagent—either alone for fluorination or in combination with halide salts X⁻ (X = Cl, Br, I) for chlorination, bromination, and iodination. Utilizing readily available methylenecyclopropanes as building blocks, this method efficiently delivers halogenated benzoxazines. This approach is distinguished by its exceptional environmental friendliness, replacing hazardous reagents and heavy metal catalysts with safe, mild conditions. Its practical utility is demonstrated by a scalable and environmentally benign synthesis of the drug etifoxine.