Intramolecular Halogenative-Arylation of Alkynes Using N-halosuccinimide (NXS) Reagents in the CH3CN-H2O System

Abstract

The cyclizative arylation-halogenation of tethered alkynes has been well explored (particularly for iodo-arylations). It is an important method for the construction of benzo-fused heterocycles as well as carbocycles possessing a halo-olefin. However, to the best of our knowledge, no reaction condition is suitable to promote all three cyclizative halo-arylations, i.e., iodo-arylation, bromo-arylation, and chloro-arylation onto the tethered alkynes is known. Here, we report a set of general reaction conditions for the cyclizative halo-arylation of the tethered alkynes. Our method employs NXS (X = I, Br, Cl) reagents as the source of halonium ion (X⁺) in the CH₃CN and H₂O solvent mixture. This process avoids the use of any transition metal catalysts and additives (acids, bases, etc.). It shows broad substrate scope in terms of substitution on both the aryl groups, with yields ranging from 40 to 98%. A large-scale reaction and synthetic modifications of the products were also demonstrated to show the synthetic applicability of the reported procedures.