Dioxazolone mediated cyclization reactions through C–H activation

Abstract

3-Substituted 1,4,2-dioxazol-5-ones, also known as dioxazolones, are emerging amidation reagents that can be converted to N-acyl nitrenes in transition-metal-catalyzed amidation reactions. This review highlights dioxazolone mediated two-component cyclization reactions via C–H activation. Many heterocyclic scaffolds have been constructed using this strategy. The types of cyclization reactions include dioxazolone directed C–H activation/cyclization with alkynes, C–H amidation/intramolecular condensation, and macrocyclization. Cyclization forms include [4 + 1], [4 + 2], [5 + 1], [3 + 3], and [4 + n] (n = 11–20) patterns, enabling the construction of five-membered and six-membered heterocycles and 15- to 24-membered macrocycles, respectively. Some polycyclic condensed heterocycles have also been obtained successfully. These cyclization reactions have been carried out under Rh, Ru, Ir or Co catalysis. In most cases, compatibility with functional groups is good, and some conversions are compatible with halogens including iodine, which provides an opportunity for further structural modification through coupling reactions. Some cyclizations can achieve a maximum yield of 99%, while others can be completed within 5 minutes at room temperature. This review will provide a reference for the synthesis of heterocycles and further research in this field.