Metal-Free Synthesis of 4-Bromoisocoumarins through Brominative Annulation of 2-Alkynylaryloate Esters Using In Situ Generated Transient Bromoiodane

Abstract

Herein, we report a facile and proficient protocol for the synthesis of 4-bromoisocoumarins through brominative annulation of 2-alkynylaryloate esters with in situ generated bromoiodane using a simple hypervalent iodine reagent as mild oxidant and potassium bromide as the halogen source. Using this method, a broad range of valuable halogenated isocoumarins can be obtained in excellent yields at room temperature. Also, this reaction takes place in the absence of any metal catalyst and exhibits high functional group tolerance. Besides, the reaction can also be extended to the gram scale, and a catalytic approach was also demonstrated. Additionally, the prepared 4-bromoisocoumarins were further transformed into important synthetic compounds.